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EPA-600/R-94~ 198 Novembe r 1994 THE RAETRAD MODEL OF RADON GAS GENERATION, TRANSPORT, AND INDOOR ENTRY by Kirk K. Nielson, Vern C. Rogers, Vern Rogers, and Rodger B. Holt Rogers and Associates Engineering Corporation P. 0. Box 330 Salt Lake City, UT 84110-0330 EPA Interagency Agreement RWFL 933783-01 Contract 68-DO-0097 to Sanford Cohen & Associates. Inc., McLean. VA DCA Project Officer: Richard Dixon Florida Department of Community Affairs 2740 Centerview Drive Tallahassee, FL 32399 EPA Project Officer: David C. Sanchez U.S.Environmental Protection Agency Air and Energy Engineering Research Laboratory Research Triangle Park, NC 27711 Prepared for: State of Florida Department of Community Affairs 2740 Centerview Drive Tallahassee, FL 32399 and U.S. Environmental Protection Agency Office of Research and Development Washington, DC 20460
------- EPA REVIEW NOTICE This report has been reviewed by the U.S. Environmental Protection Agency, and approved for publication. Approval does not signify thai the contents necessarily reflect the views and policy of the Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use. This document is available to the public through the National Technical Informa- tion Service, Springfield, Virginia 22161.
------- EXECUTIVE SUMMARY The RAETRAD (RAdon Emanation and TRAnsport into Dwellings) model has been developed to provide a simple, inexpensive means of estimating the rates of radon gas entry into dwellings from underlying soils. It can represent slab-on-grade houses of different sizes and shapes on soils with any distribution of radon source strengths, physical properties, water contents, and gas transport properties. It was developed in part under the Florida Radon Research Program (FRRP), which has been co-sponsored by the Florida Department of Community Affairs (DCA) and the U.S. Environmental Protection Agency (EPA). It has been used in the FRRP to characterize the effects of foundation soil and fill properties on indoor radon entry, to characterize the modes of radon entry, to characterize soil radon potentials for mapping of their geographic distributions, to develop simplified lumped-parameter models, and to support development of radon-protective building construction standards. RAETRAD computes radon production from radium decay, radon interactions in the solid, liquid, and gas phases of soils and concretes, and radon gas transport and indoor entry by both diffusion (concentration-driven) and advection (with pressure-driven air flow). It solves LaPlace's equation in steady state to define air pressure distributions under and near the house and to obtain air flow velocities that are used in the radon calculations. The radon differential equation also is solved in steady state, and incorporates the air velocity field in computing simultaneous diffusive and advective radon transport. The equations are solved numerically in elliptical-cylindrical geometry to represent houses of different sizes and with varying rectangular aspect (length/width) ratios. Radon entry rates into a house are computed by integrating the total radon transport across the floor surface area. Indoor radon concentrations also are estimated from the computed entry rates by dividing by the house volume and its air ventilation rate. Several analytical functions are used in RAETRAD to enhance its computational efficiency and to simplify its user interface. The numerical calculations of air flow and radon transport through floor cracks are accelerated by use of analytical functions to estimate the mesh-equivalent permeabilities and radon diffusion coefficients for the specified cracks rather than using finely-graded numerical meshes to represent them. Analytical functions also are used to define soil radon diffusion coefficients and air permeabilities for cases in which measured values are unavailable. These use soil porosities, water contents, and textures to define the radon transport properties from empirical correlations with measured data. In addition to modeling symmetric cracks in the floor slab, RAETRAD also accommodates asymmetric openings such as utility penetrations that do not match the elliptical symmetry computed for the equivalent rectangular house shape. These are represented by multiple numerical calculations that determine transverse leakage terms for the discrete-point floor openings. The numerical-analytical calculations are performed by computing all finite-difference coefficients for each model mesh unit and solving the equations simultaneously by a non-iterative matrix inversion technique. The resulting computer code is relatively small and efficient, and operates on an IBM"- compatible personal computer. Typical execution times are on the order of 1-2 minutes or longer, depending on the complexity of the problem being solved and the speed of the computer. A user interface provides queries for definition of an input file and selection of appropriate input parameters. i i i
------- The RAETRAD code was validated and benchmarked by several comparisons with analytical calculations and with empirical radon data. The analytical validations included comparison with a 2-dimensionaJ air pressure field calculated for a simple uniform 15 ft. x 31 ft. soil space with two different pressures applied at its top surface. Relative standard deviations of less than 1 % were obtained between the RAETRAD calculations and the analytical pressure field at the 1-, 2-, 4-, 8-, and 15-ft. depths below the pressure boundary. Analytical validations with 1-dimensional radon generation and diffusion from an open soil and a concrete-covered soil suggested the utility of defining a small (0.1-ft) mesh unit at the top of the soil profile to minimize the effects of mesh spacing. In these comparisons, both soil radon profiles and surface radon fluxes agreed consistently within less than 1%. Additional 1-dimensional validations included a uniform soil with radon generation, diffusion, and advective transport. In this case, the air flow velocities were forced by an external definition of a uniform pressure gradient, since RAETRAD is designed to compute only realistic, 2-dimensional pressure profiles. Again, agreement was within less than 1 % for all cases of air flowing into the soil profile. When air was drawn from the profile, a depletion of the profile was observed that caused a maximum error of 4% for the case that was analyzed. This error was reduced by considering a thicker soil profile, and was exaggerated if a thin soil layer was considered. Comparisons of RAETRAD calculations with empirical radon measurements utilized two test-cell structures (6 m x 6 m) constructed in South-Central Florida and monitored primarily by Southern Research Institute (SRI). One of these structures (test cell 1) utilized floating-slab floor construction with concrete-block stem walls over a concrete footing. The other structure had similar footings and stem walls, but its floor slab was poured to extend into a course of chair blocks at the top of the stem wall. Both cells had identical wood-frame superstructures, without windows, that were sealed with 2-3 cm of polyurethane foam to minimize air infiltration. Soil densities, radium concentrations, radon emanation coefficients, and moistures were measured in this project from numerous cores collected around and under the test cells. SRI provided measured soil radon and air permeabilities, and indoor pressures, air"ventilation, and radon concentrations. Field soil sampling at the test cell site extended only to 4-7 ft. depths for most cores; hence deeper soil regions were extrapolated from existing moisture and radium data. Calculated radon concentration profiles were within 4.4% of the means of measured values under test cell 1, compared to a 34% root-mean-square uncertainty among the measured values. Calculated radon profiles were within 18% of the means of measured values under test cell 2, compared to a 42% root-mean-square uncertainty among the measured values. Measured soil air permeabilities differed from values calculated from soil density, moisture and texture by 42%sbased on composite averages at four different depths. Excluding a heterogeneous, low-permeability layer under part of the site, the agreement was improved to 24% relative standard deviation. Indoor radon in the test cells was analyzed by RAETRAD to compare with measurements before and after drilling a center hole in each of their slabs. For the initial slab conditions, RAETRAD computed 97 pCi L"1 in test cell 1, only 2% above the mean of the measured values, 95 ± 44 pCi L'1. The radon computed by RAETRAD for test cell 2 was 20 pCi L"1, which was 10% below the mean of the measured values, 22 + 7 pCi L"\ With a 10-cm center hole in each slab, test cell 1 was computed to have an indoor radon concentration of 212 pCi L"1, which was 17% below the mean of the measured values, 255 ± 78 pCi L1. Test cell 2 with a center hole had a computed radon concentration of 87 pCi L'\ which was 18% above the mean of the measured values, 74 + 33 pCi i v
------- LComputed air pressure and radon concentration profiles under test cell 1 had relative standard deviations from measured values of 11 % and 12% respectively, which were smaller than the standard deviations among the replicate measurements. Computed air pressure and radon concentration profiles under test cell 2 had relative standard deviations from measured values of 25% and 20% respectively, which also were smaller than the standard deviations among the replicate measurements. Additional comparisons of RAETRAD calculations with radon measurements in the test cells were performed with test cell 2 at indoor pressures of -10 Pa and -20 Pa instead of its passive-condition pressure of -0.6 Pa. For the -10 Pa condition, test cell 2 was computed to have an indoor radon concentration of 51.5 pCi L', which was 3% higher than the measured 50 pCi L'1 value. For the - 20 Pa condition, an indoor radon concentration of 42.9 pCi L1 was computed by RAETRAD, 14% lower than the measured value of 50 pCi L"1. Collectively, the six model comparisons with indoor radon measurements in the test cells had an average difference of 11 %, with an average bias of -3%. Comparisons of RAETRAD calculations with indoor radon measurements in 50 FRRP demonstration houses exhibited much larger variations (geometric standard deviations of 2.8), and a bias of a factor of 0.56 below the measured values. This was attributed to the much less detailed characterization of the houses, primarily with respect to the concrete slab integrity and diffusivity. Significant unobserved holes or cracks (>50 cm2) near utility penetrations or by walls, bathtubs, or other features could cause this much bias, as could a 3-fold higher radon diffusion coefficient than was used for the floor (0.001 cm2 s'1)- Observations and measurements support either of these possibilities. ABSTRACT The report describes the theoretical basis, implementation, and validation of the RAdon Emanation and TRAnsport into Dwellings (RAETRAD) model, a conceptual and mathematical approach for simulating radon (222Rn) gas generation and transport from soils and building foundations to the indoor environment. It has been implemented in a computer code of the same name to provide a relatively simple, inexpensive means of estimating indoor radon entry rates and concentrations. RAETRAD uses the complete, multi-phase differential equations to calculate radon generation, decay, and transport by both diffusion and advection (with pressure-driven air flow). The equations are implemented in a steady-state, 2-dimensional finite-difference mode with elliptical-cylindrical geometry for maximum efficiency and modeling detail. For validation, the air flow part of RAETRAD was compared with a 2-dimensional analytical calculation of air flow through a uniform field. Variations of
Источник: https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P100S220.TXT

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(h
m
o
0.05-

0.00-t "T" T - i

2 4 5 6 7 10
0
Viscosity (Poise)

FIG. 2-5

EFFECT OF VISCOSITY AND OSCILLATION FREQUENCY ON


PERIMETER GAP THICKNESS

0.0250 -

0.0225 -
\ 1.5 m/min
\
0.0200 - \
\
\
\
e 0.0175 - \
\
e 1.0 m/min^
PH 0.0150 -
H
PM
O
id
0.0125-
Ui
a
0.0100-

0.0075-
0)
> 0.0050-

0.0025-

0.0000-1 1 1 1 1 1 1 1 1
0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16
Distance from Slab Towards Mould (mm)
FIG. 2-6
EFFECT OF CASTING SPEED ON VELOCITY PROFILE IN GAP
(MAIN PORTION OF PERIMETER) "
17

0.5 m/min
1.0 m/min
1.5 m/min

g 0.02-

0.00 i 1 1 1 1

0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75


Distance from Shell Towards Mould (nun)

FIG. 2-7

EFFECT OF C ASTING SPEED ON VELOC ITY PROFILE IN GAP


(CORNER REGIONS)

3.5n Slab S i z e 2100 x 200 nun


Mould O s c i l l a t i o n : 100 cps
3.0-
0)
c 2.5-
O
p

J? 2.0
c
O 1 5
P
CU

ra L O '
c
o
o
0.5-

0.0 1 1 1 1 1 1 1
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75
Casting Speed (m/min)

FIG. 28
EFFECT OF C ASTING SPEED AND POWDER VISC OSITY ON
THE C ONSUMPTION RATE
18

3.5-
Slab Size 2100 x 200 mm
Casting Speed: 1.0 m/min
3.0-

c 2.5-
s
Oi
.* 2 . 0 -
c
H 1.5 \ 150 cpm
4J \
& \
n 1.0 - \
e
0 100 cph-.
u
0.5-
50 cpm
0.0 -i r 1 1 r
3 4 5 6 7 10
Viscosity (Poise)

FIG. 2-9

EFFECT OF POWDER VISC OSITY AND OSC ILLATION FREQUENC Y


ON POWDER C ONSUMPTION RATE

According
According tt oo Model
Model j Plant
_x P l a t e Grades a t ^ 0 . 8 5 m/min j T r i a l
_# S t r i p Grades a t ^ 1 . 2 m/min ) a t a

c 0.45 -\
o 0.85 m/min
o
o. 0.40 - 1.20 m/min
ni
w 0.35 -l
0.30 -t-
2 3 4 5 6
V i s c o s i t y (Poise)
FIG. 210
EFFECT OF MOULD SLAG VISC OSITY ON C ONSUMPTION RATE:
COMPARISON OF PLANT TRIAL DATA WITH NSC MODEL
-19-

\ / / / , 1 4 0 0 C y / y V - SiC hot plate


f f f f f Heat Flow
FIG. 2-11
SCHEMATIC DIAGRAM OF HOT PLATE E XPE RIME NTS

/H20

Thermometer
(a)

Copper Finger

op * > * Clamp
\W\ Alumina Tube
/ A
/ Pt Foil
/ A
RF Coils. -*o /
/
/
Molten
/ Graphite
Steel
f
1500C / C Crucible

Alumina Tube
,. . r i , - - , i^n Decarburised
KD)
^''"Tn Powder Layer
Sintered Layer
Molten Drops
Surrounded b y Carbon
Molten Layer

FIG. 2-12
(A) SCHE MATIC DIAGRAM OF THE APPARATUS USE D IN THE
INDUCTION FURNACE E XPE RIME NTS
(B) SCHE MATIC ILLUSTRATION OF THE LAYE RS FORME D IN THE TUBE
20

T
Meniscus 400
200 600 < 11200 1600
Temperature C M "il
O
nat
o bo
<->
ii
<u
S

FIG. 2-13
THE TEMPERATURE PROFILE IN THE POWDER L9 FROM TRTAT. 1
21

7(n

Meniscus T
200 400 600 < 800 1000 o 1600
Temperature (C)

o
OH
t* be
O .5
5S
O 0)
o* S

FIG. 2-14
THE TEMPERATURE PROFILE IN THE POWDER L9 FROM TRIAL 2
22

Equation of Line is:


Y = .975436E02 X +21.4392
Correlation C oefficient = .83617
95% Confidence Limits for the
points
14 points in File

Meniscus 0
1600
Temperature (C )
1C4->

lOJ p-4
O
PU
u hl)
o
%+->
Q)
o
PU S

FIG. 215

THE TEMPERATRE PROFILE IN THE POWDER L7


-23-

70'
Equation of Line is:
Y = .529211E-04 Xt2 -.100593 X+l +56.595
R squared = 84.4868
95% Confidence Limits for the points
39 points in File

Meniscus 0
fe 200 400 600 5pv.00 1000 3
o
ti
o Temperature (C)
J co
-10
o
O b
(IH C

FIG. 2-16

THE TEMPERATURE PROFILE IN THE POWDER L8


24-

APPENDIX21

In order to calculate the powder consumption rate it is necessary to calculate the


gap thickness (between the slab and the mould) and the velocity profile of the semimolten powder
in this gap.

A major factor in determining the flow characteristics is the viscosity of the powder. Information
on viscosities is readily available, but the viscosity is affected by the force being exerted on the
powder by the mould oscillation. Ohashi has derived equation (A21.1) to give the effective
viscosity:

u" = u ( l + 4 n 2 f 2 i n 2 r l
....(A21.1)

The viscosity is also varying across the gap due to the temperature drop. This is given by:

.... (A21.2)
where

Q
~ ITHTT"/
m s
Applying fluid lubrication theory to the gap, the basic equation defining the flow is:

8x \ ox / dy
(A21.3)

Assuming djj = 0 and with the following boundary conditions


dy

u = Vc at x = 0
and u = 0 at x = 2d

equation (2.3) is integrated to give:

Qx
z 2 f 2 _ !_ 2 s j:2i Q* oQ Qx Q
4pg(l+4n fW )d fQx ^ Qe" - e e
+ (e
u
uQ 2 ti rrs "- ,
1 e "
Q V

.... (A21.4)
which defines the velocity profile in the gap.
-25

The gap thickness is obtained by integrating equation (A2-1.3) to obtain the pressure P and then
substituting the statistic pressure difference for P:

d= VQ,UV /36g(p p -pXl + 4 n V )


1 F
..(A2-1.5)

where Qi = Q2(l-Qe-Q-e-Q)/(l+e-2Q-Q2e-Q-2e-Q)

V0 is the average relative speed of the slab with respect to the mould and is given by:

V0 = 4 fa sin (1-a) n + (l-2a) Vc


.... (A2-1.6)
and
1 1 . -l( V c \
a = - - sin ( J
2 n V2nfW
....(A2-1.7)
In the corner regions the shrinkage of the solidifying steel creates a greater gap than above, and
the gap here is:

di = D K/2
.... (A2-1.8)

The length over which this is effective is a relative affect of thermal contraction and the bulging of
the shell

x = a.a ATV I V 2h /J
o .... (A2-1.9)
To"
By integrating the flow around the whole perimeter the consumption rate is obtained.
26-

3. STICKER BREAKOUTS

3.1 Review Of The Published Work On Sticker Breakout

The occurrence of sticker breakouts has frequently been linked with the nature and the
performance of the casting powders employed. If measures are to be taken to eliminate sticker
breakouts, it will be necessary to answer two queries:

(I) Why do some powders produce a higher incidence of sticker breakout than others?

(ii) Why do some batches of powder (with a good overall record on sticker breakout) produce
sticker breakouts?

It will be seen that much of the published work relates to the detection and subsequent remedial
actions which can be taken to avoid sticker breakouts; some work has been reported on the effect
of the composition of the powder on sticker breakouts but little work has been reported on the
effect of batch to batch variations on breakouts.

3.1.1 Detection Of Sticker Breakouts

Heat Flux Measurements

Heat flux measurements have been used to detect imminent sticker breakouts by employing
thermocouple arrays located in the mould. Ohasi et aid), Tsuneoka et aK2' and Kurihara et al<3)
have all reported measurements made with these detection systems; a typical temperature-time
trace, revealing an imminent sticker breakout, is shown in Fig. 3-1. Matsushita et al(*) observed
(rom heat flux measurements that (i) a hot tear develops, and this is initiated at the middle of the
fixed side, and (ii) sticker breakout occurs when "hot spot descending speed" (v0) is between 0.35
and 0.85 v<, where vc is the casting speed. Subsequently, Matsushita et al<6> concluded that the
"hot spot1* was due to shell breakage, but neither the magnitude of the temperature rise nor the
rate of increase could be used with certainty to predict breakout. They concluded that the
propagation velocity of the tear (Horn nose1) was 0.75 (0.15) vc. They also used Fourier
transformations to analyse the results of T(mould)-(time) plots, and concluded that the
temperature transition associated with sticker breakout exists in a certain zone.

Friction Measurements

Nakamori et aU6J> monitored (i) the current required to vibrate the mould and (ii) the vibration
acceleration of the mould to derive frictional force measurements in the mould. They found that
this produced characteristic variations just before sticker breakout occurred (Fig. 3-2) and with
this system they were able to detect 60% of the sticker breakouts which occurred.

Remedial Action To Avoid Sticker Breakouts

Non-sinusoidal oscillations have been used to lower the incidence of sticker breakouts. Suzuki et
al?) hav studied the effect of non-sinusoidal oscillations on the frictional forces by determining
the pressure difference between the inlet and outlet of the hydraulic cylinder. This quantity
corresponds to the (inertiaforceof the mould) + (friction force inside the mould (AFf)), the inertia
force could be deduced separately from the pressure difference in idling periods. In Fig. 3-3 it can
be seen that the AFf increases as the casting speed (vc) increases, and AFf was found to be smaller
in the case of non-sinusoidal oscillations. It was considered that this was due to (i) an increase in
-27

powder consumption, and (ii) the speed of the mould relative to that of the shell decreased with
non-sinusoidal oscillation and thus resulted in lower friction forces at high casting speeds.

3.1.2 Thories For The Cause of Sticker Breakouts

Crystallisation Index Of Powder

Sorimachi et aldM2) reported that the incidence of breakouts was related to the crystallisation
index of the mould powder. This index was determined by quenching the liquid slag from the
mould into a stainless steel receptacle with subsequent metallographic examination of the
quenched sample. Breakouts decreased when (i) basicity (CaO/SiCt) decreased, and (ii)
crystallisation temperature decreased (Figs. 3-4 and 3-5).

Imai et aU13> reported that the presence of gases increased both the crystallisation index (Fig. 3-6)
and the viscosity of the slag (Fig. 3-7). The relative crystallisation index was determined in these
experiments by X-ray diffraction. They suggested that as the viscous friction force accounted for
80-90% of total friction, the presence of gases (Ar, CO2 or air) in the slag could thus increase the
viscous friction force to a level where it exceeded the tensile strength of the shell. This would
result in restraint of the shell and a breakout would occur in due course.

3.1.3 Heat Flux Variations Caused By Changes In Casting Speed

It is known that sticker breakouts are more likely to occur after periods where the casting speed
(vc) has been varied. These conditions cause variations in the mould temperatures*14* (Figs. 3-8(a)
and (b)) and when these data are presented in the form of plots of mould temperature versus
casting speed (Figs. 3-9(a) and (b)) a hysteresis in the results is revealed. Breakouts occur when
there is either too much or too little heat extraction from the mould, as can be seen from Fig. 3-10
which shows the recorded heat transfer plotted as a function of the casting speed for various casts.
Thus it would appear probable that sticker breakouts are related to the hysteresis observed in
both the mould temperature and heat transfer. The hysteresis can be accounted for by the
changes which occur in the depth of the molten pool (H). When vc is changed suddenly a certain
time is required before these changes work their way through into changes in the depth of the
molten pool and the thickness of the slag layer (d). Two cases are discussed below:-

(i) When vc is decreased, both H and d will increase, thus when vc is restored to its original
value there will be a time lag before the molten pool depth (H) (and subsequently d),
revert to their steady state values and in this interim period the relatively thick slag
layer will result in low values of heat flux and mould temperature.

(ii) When vc is increased, both H and d will decrease, thus when vc is restored to its original
value both H and d will remain below their equilibrium values until steady state
conditions are attained and consequently the heat flux and the mould temperature will
both remain relatively high during this interim period.

This type of sticker breakout is particularly prevalent in high speed casting.

3.1.4 Frictional Forces In The Mould

Tokiwa et al<7 > calculated the frictional forces in the mould arising from an insufficient flow of
molten casting powder into the mould/strand gap. They derived values for the frictional forces in
the mould for these conditions; this was found to vary only slightly from the value for normal
conditions.
28

Mizukami et a l (9,10) produced a mathematical model to predict friction forces in the mould. The
tensile stress (at) was calculated and compared with the high temperature strength (%) as a
function of casting speed, taking into account the physical properties of the mould powder. For a
casting speed of 1.8 m min-l it was calculated that Ob>Of for a position 50 mm below the meniscus,
but Ob < Of at a depth of 200 mm; thus it was necessary to improve lubrication by using a powder
with low viscosity and low melting point. It was proposed that the oscillation mode should have
the negative strip (NS) taking a critical value given by

8 8 1
N ^ . - ' . )

where t1 and t2 are times at which v m = vc. For non-sinusoidal oscillation this requires that the
time when the mould is ascending should be longer than when it is descending. Non-sinusoidal
oscillation decreased the liquid friction by about 40%.

3.1.5 Formation Of A Pseudo-Meniscus

Tsuneoka et al(2) made the following observations of sticker breakouts:

(i) The oscillation marks have a characteristic V-shape, fanning out from the sticking point
(Fig. 3-11).
(ii) The pitch of the oscillation marks in the 'constrained' region is smaller than that in the
sound portion.

(iii) Shell thickness in the ruptured portion (shown as A in Fig. 3-11) is larger towards the
meniscus, cf smaller in normal section (B in Fig. 3-11), as can be seen in Fig. 3-12.

They proposed the following theory, which is shown diagrammatically in Fig. 3-13:

(i) At stage 2 - "constrained shell" is separated from sound shell.

(ii) Molten steel enters this gap and solidifies on each portion of shell (marked X, Y) and

shown in stage 3.

(iii) This newly-formed shell is then separated again (stage 4).

(iv) Molten steel solidifies again at stage 5.


This process is repeated, and the pseudo-meniscus descends towards the bottom of the mould until
a point is reached where breakout occurs.
Tsuneoka et al(2) also developed a 3-dimensional, non-steady state, heat transfer model to
simulate this mechanism; it can be seen from Fig. 3-14 that there is excellent agreement between
the calculated and measured temperature transitions.

These workers also analysed the forces affecting the rupture and repair of the shell. During
normal solidification there are two forces operating, the frictional force (F,,) between the shell
and mould and F g , the force due to shell gravity. Relationships for F^ and F g were derived and an
expression for the shell yield stress (FJ was also obtained. Plots of the magnitude of F, F g and F c
29-

versus the distance from the meniscus are given in Fig. 3-15(a) and it can be seen that the shell
cannot rupture in the mould, as the condition F> Fj,-Fg is always satisfied.
r

However, when a 'constraint' occurs, the shell rupture which occurred at the meniscus (described
above) propagates to the mould bottom at rates of avc and vc, respectively, where a and are
constants relevant to the casting and width directions. As the force due to shell gravity is offset by
buoyancy, the inertia due to oscillation, F 0l is taken into account and a relationship derived.
Assuming that the yield stress of the ruptured shell formed during the period of negative strip (tn)
attained maximum value at the end of this period in every oscillation, they calculated values for
F0, FJJ and F0. It can be seen from Fig. 3-15(b) that when the pseudo-meniscus has travelled 300
mm below meniscus F 0 < (F^-F,,), the rupture will propagate downwards as a consequence of the
friction force caused by ferro-pressure. This will occur despite the fact that the constraining force
at the meniscus is released by the solidification contraction of the constrained shell. In order to
recover the situation, the operation must meet the condition that (F o >(F u -F 0 ). Fig. 3-16
represents the control variables, v c and tn, necessary to prevent breakout. If the terms a and
(defined above) exceed the value of 0.75 used in the calculations for Fig. 3-16 further deceleration
would be required to recover the situation.

3.1.6 Causes Of The 'Constraint'

Tsuneoka et al<2> examined the stuck shell and found evidence of copper adhering to the shell and
also carbon-concentrated structures which they attributed to contact of the meniscus with
unmelted casting powder. They suggested that the constraint occurred because the coefficient of
friction between the mould and the strand was increased by solid/solid contact as a result of the
insufficient flow of liquid slag.

Mukai et al<15> also examined the shell stuck in the mould after a sticker breakout and observed:

(i) Traces of molten metal droplets (which possessed a carburised structure and cavities) in
the vicinity of the sticking point.

(ii) A carburised structure in the vicinity of the sticking point.


o
(iii) The metal droplets and carburised structure had similar compositions to that of the
molten steel except for the C content.

(iv) The carbon content was close to 4% for the metal droplets.

They concluded that the cavities were due to the formation of CO(g) on solidification and that the
carburised structure was due to the formation of local regions with high carbon concentrations in
the meniscus. They also suggested that unmelted casting powders were the carbon source of these
decarburised regions and that this powder caused a blockage to slag infiltration. Since the
carburised region would have a low melting point, the shell would not be repaired sufficiently at
the time of negative strip, and this would lead to sticking of the shell to the mould.

3.1.7 Comments On The Theories Of Sticker Breakouts

It would appear the theory due to Tsuneoka*2) explains most of the facts and observations, but it
does not explain how the 'constraint' occurs, other than suggesting that an interruption to the slag
flow was responsible. However, the increased carbon levels in the shell have been noted by
Tsuneoka et al<2> and Mukai et al<ls>, and thus it seems the 'constraint' could be caused by the
decrease in the liquidus temperature of the steel, as suggested by Mukai. Furthermore, there is
30

strong evidence that the solid slg film attached to the mould remains more or less unaltered
throughout the casting operation. It can be seen that the sequence of events shown in Fig. 3-13
does not take the infiltrated slag film into account and the latter would serve as a partial barrier
to heat flow from the mould. A tentative represenentation of the sequence of events occurring
during a sticker breakout, where the slag layer is also taken into account, is shown in Fig. 3-17.

It is proposed that the essential features in the events leading to a sticker breakout are:

(i) A carbonaceous agglomerate (probably alumina) is forced to the edge of the mould (Stage
1).

(ii) Carbon diffuses out of the 'agglomerate and forms a zone of carbon-rich steel in the
locality of the agglomerate, the steel in this zone has a low melting point and
consequently does not freeze (Stage 2).

(iii) The agglomerate blocks the flow of slag into the mould/strand gap (Stage 2) and thus
there is a melt-back of the solidified slag film which results in an increase in both the
heat transfer and mould temperature.

(iv) The increased heat transfer results in the solidification of the steel which forms a
pseudo-meniscus separated from the original meniscus.

(v) Both the pseudo-meniscus and the original meniscus become thicker as the process
proceeds.

(vi) The gap between the original meniscus and the pseudo-meniscus will not be fully
repaired in negative strip time because of the low melting point of the steel and the
relatively low heat transfer associated with the thick slag layer (Stages 4 and 5), and the
tear will redevelop during positive strip periods in subsequent oscillations.

(vii) In the second and subsequent oscillations (e.g. Stages 7 and 8) melt-back of the solid slag
film would occur at a lower level, so the temperature transient would appear to move
down the mould as observed.

(viii) The absence of a liquid slag layer would result in solid/solid friction which would account
for the increased friction forces recorded. Breakout would occur when these forces
exceeded the shell yield stress.

There is anecdotal evidence that a sticker breakout often occurs during periods when the casting
conditions would result in the formation of relatively large amounts of alumina. However it is not
known whether a sticker breakout can occur without the formation of a carburised, low melting
shell in the meniscus region.

The observation of Sorimachi et alUMZ) that the incidence of sticker breakouts increased with
increasing basicity of the mould powder can not be accounted for the powder to dissolve alumina
(see Section 3.10) since the reverse would have been expected. If this observation is generally
applicable, the lower frequency of cracking must be due to the thicker slag layer produced by the
high silica, high viscosity, molten powders.
-.31 -

3.2 Summarv Of Factors Relevant To Sticker Breakout

3.2.1 Casting Conditions Favouring Sticker Breakout

(i) Where the casting conditions have resulted in the formation of relatively large amounts

of alumina (see Section 3.5).

(ii) Where zirconia is produced by the erosion of the SEN (see Section 3.5).

(iii) When the casting speed is suddenly changed, which causes insufficient or excessive

extraction of heat from the shell.

3.2.2 Differences Between Stuck And Unstuck Portions Of The Shell

(i) The oscillation marks have the characteristic V-shape fanning out from the sticking
point; the pitch of these marks being smaller than in the sound portion of the shell.
(ii) The shell thickness in the stuck portion increases towards the meniscus which is the
opposite of that observed in a sound shell.
(iii) Iron droplets are formed on both sides of the stuck shell in the vicinity of the sticking
point, none were observed in the sound shell.
(iv) The stuck shell has a carburised structure whereas the sound shell had no carburised
regions.

(v) Cavities can be observed in the stuck shell which is associated with the formation of
CO(g) bubbles, whereas none were observed in the sound shell.

3.2.3 Possible Mechanism For Sticker Breakout

It is possible that sticking breakout occurs by the following mechanism:

(i) There is a blockage to the flow of slag into the mould/strand gap by large agglomerates
sited at the meniscus.
(ii) In this region, there is carbon diffusion into the steel which results in the formation of a
high carbon, low melting point, shell which does not heal in the positive strip time.

(iii) Breakout occurs when the frictional forces exceed the yield stress for a steel shell.

3.2.4 Possible Sources Of Blockage

Carbonaceous materials which block the flow of slag into the mould/strand gap are:

(i) Alumina particles associated with casting powder.


(ii) SEN and tundish stopper rods materials which may be eroded or be ripped away when
the alumina agglomerates attached to the refractory wall are flushed out by a build up of
pressure.
32-

3.3 Prediction Of Sticker Breakout By Qn-Plant Monitoring

In order to investigate the casting parameters which affect sticking breakouts, plant trials have
been carried out on a slab caster which permitted the logging of the relevant casting parameters.
The slab caster was a twin strand machine and signals were logged from both strands.

The logging system, consisting of a microcomputer with isolated measurement pods, stored the
data during casting from a large number of casts in order to acquire information for as many
breakouts as possible. The system had a variable sampling rate (up to a maximum of 12 per
minute) for recording all the plant signals, this was sufficient to monitor any unexpected changes
in signals prior to breakout. These data were processed with other relevant recorded data,
available as needed, for any casts which terminated in a breakout.

The logged signals were also correlated with slab surface quality inspection data which are
available on computer. This allowed relationships for the prediction of slab surface quality to be
developed. For this part of the work a slower sampling rate could be used, and further details are
given in another section of the report.

The following signals were logged:

Casting speed
Mould oscillation
Mould water flow rates
Zone 1A flow rate
Zone IB flow rate
Edge zone flow rate
Mould water inlet and outlet temperatures
Tundish stopper position
Mould metal level and rate of change

Fig. 3-18 shows a schematic illustration of the data logging system and the casting parameters
logged. The relevant plant signals were wired through isolating amplifiers to an isolated
measurement pod in the caster control room, and were connected via a serial link to a
microcomputer, situated a safe distance away, which controlled both the logging and recording.

Additional information to be used in the analysis, where appropriate, included:

SEN immersion depth


Samples of used and unused mould flux
Measurements of slag depth in the mould
Measurements of powder consumption rate

3.3.1 Monitoring Mould Water Temperatures

Examples of the processed logged data for casting speed, mould water flows, mould water
differential temperatures, and the calculated mould heat flux for the 2 broad faces of the mould
taken from a cast that was aborted due to a sticker breakout, are shown in Figs. 3-19 to 3-23,
respectively.

The mould water differential temperatures (Fig. 3-20) were measured between the common inlet
temperature and the separate outlet temperatures for each face of the mould. This trace was
fairly constant except at the position equivalent to the drop in casting speed (Fig. 3-19) from 0.67
-33-

to 0.56 m/min for 27.6 minutes. There was a time lag of approximately 1.5 minutes before the
speed drop produced a detectable change in the mould water differential temperatures and the
mould heat flux.

The sticker breakout occurred on the outer radius of the strand and from Fig. 3-22 it can be seen
that there was no detectable change in the mould heat flux from the outer radius when compared
to that of the inner radius, prior to the breakout.

The final 10 minutes of casting are shown in more detail in Fig. 3-23 to show this more clearly.

Several breakouts have been monitored with this system and it has proved too insensitive to
detect either the occurrence of the breakout or any adverse conditions leading up to the breakout
by the monitoring of the mould water differential temperatures.

In order to improve the sensitivity of the mould heat flux measurements, the response time of this
system can be decreased by repositioning the resistance thermometers to be as close as possible to
the outlets from the mould plates, but whether these improvements would be sufficient to produce
a reliable system has not been established.

This system has also been used to assess any relationship between heat flux in the mould and slab
surface quality, details of which are given in Section 4.2.

3.3.2 Monitoring Of Mould Temperatures By Thermocouples

A more accurate method of measuring mould copper temperatures and hence the heat flux
transferred through the mould can be achieved by the installation of an array of thermocouples
into the mould walls. The temperatures recorded by these thermocouples will give indications of
the conditions in the mould, and analysis of the variations can be used to recognise problems
arising during casting.

Figs. 3-24 to 3-26 show the casting speed, the thermocouple reading from a position 80 mm below
the meniscus on the inner radius, and the mould cooling temperature rise for the same mould
plate, respectively, for the same slab machine cast. It is readily seen that the mould water
temperature rise trace (Fig. 3-26) reflects the change in the casting speed but little else is
discernible. However, the thermocouple trace (Fig. 3-25) reflects other events in the mould as
well as the casting speed, e.g. the larger peaks and troughs are indicative of changes in the mould
level.

In order to predict a sticker breakout from thermal flux measurements it is necessary to


understand the cause of the heat flux changes under these conditions. Fig. 3-27 shows the
development down the mould of a potential breakout due to sticking in six stages. Alongside the
shell development are temperature traces (a and b) from 2 thermocouples implanted in the mould
wall at two depths below the meniscus and in the same vertical line. Fig. 3-27 (1) shows normal
casting conditions, but if a localised sticking occurs between the newly formed shell and the mould
at the meniscus level, a tear will occur as the strand is withdrawn and the stuck portion rises with
the mould oscillation. During negative strip the tear will heal slightly and then pull away again
during the next oscillation cycle. This is repeated at each successive mould stroke and the tear
slowly advances down the mould at approximately 60% of the casting speed. The tear also
advances outwards in the horizontal direction at an equivalent rate to the vertical direction. This
results in a typical shaped shell with characteristic oscillation marks as described in Section 3.1.5.
34

Under normal casting conditions the upper mould thermocouple would register a higher
temperature than the lower one, indicating a thinner, hotter shell at that position. As the thin
tear region passes the upper thermocouple position the melt back of the slag flm causes the
temperature to rise as shown in Fig. 3-27 (3). As the tear region passes further down the mould
and the shell thickens above the tear, the temperature begins to fall and will eventually fall to
below the normal casting temperature.

The lower thermocouple temperature will follow a similar pattern as the upper, and at a certain
point the temperatures will cross over as in Fig. 3-27 (5). This system can be linked to alarms
which would respond to these characteristic temperature traces. On the alarm the strand can be
stopped or slowed down (see Fig. 3-16) to allow the tear region to heal enough and so the stuck
portion can be pulled free from the mould and the shell will not rupture on exit from the mould.

As sticking can occur at any position of the meniscus around the perimeter of the mould there
must be enough pairs of thermocouples to cover the whole mould, but from an engineering
viewpoint it is preferable to keep the number of thermocouples to a minimum. Consequently the
pairs of thermocouples must be positioned close together to ensure that if a sticker occurred at a
point mid-way between them, the thermocouple response would still allow sufficient time for
preventative action. Thermocouple separation/distances will therefore depend upon casting
speed, length of mould below meniscus and the response time of the casting machine to slow down
or stop.

3.4 Quality Control Tests For Powders

Quality control testing of mould fluxes was carried out on plant to specify whether a particular
batch of powder had deviated from that specified by both the manufacturer and the plant
technical departments.
r
A wide range of tests, both simple and sophisticated, have been used to examine the various
properties of the powder/slag, as shown in Table 3-1. Most of the tests require sophisticated
equipment, and are time consuming and are, consequently, not ideal as routine tests. Routine
Q.C. tests must (i) be quick and easy, (ii) use equipment that can be quickly or permanently set up
and (iii) give results which are reproducible and which can be interpreted quickly and acted upon.

Ideally the tests should be such that they do not deform the powder structure, and represent the
in-mould situation as closely as possible; these conditions are not easy to simulate.

The following relatively easy tests were performed:


*r
Bulk density - This measures variations in characteristics such as agglomeration
properties and moisture content. Powders with a low bulk density
are more porous and are better insulators.

Size gradings - The distribution of particle sizes is important since it can affect the
melting rate of the powder. Samples with a large volume fraction of
small particles or granules will have a lower bulk density. This will
also give an indication of the flowability of the powder, i.e. the
ability of the powder toflowevenly, and so produce an even
thickness layer of powder on the meniscus.
-35-

Chemical composition - including water content - can be compared with the


manufacturer's specification and the basicity and the viscosity
can be calculated from the chemical composition.

Mould dips - Molten slag depths can be accurately measured in the mould
using a device consisting of four metal wires with different
melting points, viz. mild steel, copper, aluminium and solder.
When dipped through the powder and slag layers and into the
steel, the mild steel wire will melt near the slag/metal interface;
the melting point of copper (1080C) is close to that of the
powders in use; the aluminium (melting point 660C) melts in
the sintered powder layer and the solder (melting point 183C)
close to the surface of the powder (Fig. 3-28). The temperature
profile through the powder/slag layer can then constructed from
these data.

3.4.1 Variability Of Casting Powder Supplies

Although some incidences of sticker breakout occur when the casting conditions favour the
formation of alumina, other breakouts occur suddenly and inexplicably without any apparent
build up in alumina. It is generally believed that the casting powder is responsible for this latter
type of breakout. Appreciable variations in either the chemical composition or the particle size
distribution of a specific batch of powder could be one of the possible causes of the breakout.
Consequently, the variability of casting powder supplies has been monitored for twelve batches of
powder L7, three batches of L4 and two batches of L2 (Table 3-2).

3.4.2 Variations In Chemical Composition

The results of the investigation are summarised in Table 3-2 which shows the maximum and
minimum levels recorded for the most important components of the powder. It can be seen that
the extreme bounds of composition rarely deviate from the specified range except for levels of free
carbon and to a lesser extent, AI2O3. In all probability, the small AI2O3 variations would have
little effect on the performance of the powder. However, variations of the carbon content, as large
as those shown in Table 3-2, could have a marked effect on the rate of melting of the powder and
consequently could lead to the build up of a carbon-rich agglomerate.

3.4.3 Variations In Particle Size Distribution

The results on the variability of the particle size distribution for different supplies of casting
powders are summarised in Table 3-3. It can be seen that the variations (i) within a bag, (ii)
within one pallet, (iii) from pallet to pallet and (iv) from batch to batch were all monitored. The
following observations can be made about the particle size distribution:

(i) The variations within any bag are small.

(ii) The variations within one pallet, and from pallet to pallet and from batch to batch are all
considerable.

(iii) As might be expected, these variations, in percentage terms, are the greatest for the
most populous particle size range (>250 urn for L7 and < 125 um for L4 and L2).
36

The particle size distribution could have an appreciable effect on the rate of melting of the powder,
and sticking breakouts occurred when using powder L7. Unfortunately no samples of the bags
used just prior to the breakout are available, but variability in supplies could be a contributory
factor.

3.4.4 Variations Of Chemical Composition With Particle Size Distribution

The chemical compositions of the various particle size fractions have been determined on three
bags of casting powder from two different batches of L7. The results indicated (i) that there is
surprisingly little variation in the levels of CaO and SO2, and (ii) the smallest size fraction ( < 125
um) was higher in A1 2 0 3 (5.4 cf 4.9%) and Na 2 O (7.1 cf 6.4%) and lower in F (6.6 cf 5.3%) and free
carbon (8.6% cf 11%) than the larger (>125 urn) fractions. Clearly the free carbon variations
could have a significant influence on the casting performance, particularly where the smallest
particle size range deviated appreciably from the norm.

3.4.5 Conclusions On Variability Of Powder Supplies

(i) The variations in both the free carbon contents and the distribution of particle sizes
recorded in the supplies monitored in this investigation were considerable and could lead
to appreciable differences in the melting rate of the powders.

(ii) These differences in melting rate could lead sequentially to marked changes in the depth
of the molten slag pool, the thickness of infiltrating slag film and the heat flux extracted
from the shell. Such changes in heat flux could lead to sticker breakout^) (Section
3.1.3) and longitudinal cracking (Section 4.1).

3.5 Monitoring Of Casting Techniques Related to Slag Alumina Levels

3.5.1 Introduction

It has been stated previously that it would appear that some sticker breakouts are associated with
casting conditions which result in the formation of alumina. Consequently, in an attempt to

Источник: https://www.scribd.com/document/356438934/Mould-Flux
GvG Profession Guides
Ranger • Monk • Mesmer • Bitchroles • Flagger • Teamplay • Tactics • Splitting

Being a good ranger is a very difficult thing to learn – you will only become one by practicing a lot. You will notice when you are having a good game or not. If you play well, the game will go smoothly, you will dictate the flow of play, and you will direct your team to a win. On the other hand, if you play poorly, there will be chaos. Your team will have no control of movement or the flow of the game, and in the voice chat everyone will end up screaming because they have no idea what is happening.

This guide won't cover how to play in and against specific team builds. These scenarios are too situational and will change with meta, flux and playstyle. The key to improving after having read read this guide is to practice as much as possible. If you can’t GvG, random arenas and alliance battles are great places to practice. There you’ll learn all kind of different skills, the effects of them and how to control certain builds.

Interface

As a ranger you need to see what's happening on the battle field.
  • You need to widen the skill activation bar of your target. This is very important, because it will greatly help you with identifying skills quickly and deciding whether or not to use an interruption skill.
  • You need a larger compass, so that you will be able to see quickly and in better detail what is going on on the map.
  • Keep your screen open and free. As a ranger you watch the field a lot. Having a large party window or your inventory open will reduce visibility.
    • Don't overdo this with a 4k resolution. You can only watch parts of your screen at a time anyway, so displaying too much at a time won't help.

Now set your skill bindings. A ranger doesn’t need a lot of micro skills, so in essence you don’t have to change a lot from the default settings. Because target selection is crucial as a ranger, Tab is a very important key to switch to your next target, but switching back to your previous target is probably just as important. With mostly default settings Q (key next to tab) is useful for selection the previous target. This way, target selection can be done with the same finger. Target nearest item is also a very important key. One of the roles rangers have is pushing flags, which means that you will have to be able to pick up the opponent's flag as fast as possible when they drop it. V is a close key for this. Toggle in your general options to auto target NPCs and items when there is no chosen target. When you expect a flag to be dropped un-select your target and spam space so you pick up the flag faster than your opponent.

Roles

The ranger is designed to be a versatile profession, but not all variants are commonly viable in competitive play. You could categorise the ranger in 5 roles:

1.  The apply ranger: This is the most common ranger build, as well as one of the most versatile roles in the game. The apply ranger uses his poison to pressure the team, spread interrupts, camp a single target, push flags or follow splits. This all depends on the situation during the match.
2.  The turret: This bow ranger is meant to have good single target spike damage while being one of the strongest split defending options and well-suited for interrupting.
3.  The beast master: This ranger focuses solely on its pet to provide pressure or spikes.
4.  The spear ranger: This ranger provides good condition spread, often combined with the extra pressure from a pet.
5.  The spiritpooper: This ranger would mostly sit back and cast spirits to make your team builds as effective as possible and destroy the opponent’s. This is usually done in a mostly physical based team with an adjusted backline light on enchantments to make full use of spirits such as Infuriating HeatNightfallRanger. Expertise Infuriating HeatElite Nature RitualCreate a level 1..8..11 Spirit. Non-Spirit creatures within its range gain adrenaline twice as fast. This Spirit dies after 30..54..62 seconds.5315 and Nature's RenewalCoreRanger. Wilderness Survival Nature's RenewalNature RitualCreate a level 1..8..11 Spirit. For 30..126..158 seconds, Enchantments and Hexes cast by non-Spirit creatures take twice as long to cast, and it costs twice as much Energy to maintain Enchantments. This Spirit dies after 30..126..158 seconds.5560.

In the current meta the first two roles are most common and will now be explained in detail, assuming these standard bars:

The energy cost of attack skills, rituals, touch skills and all Ranger skills is reduced by 56%.

CoreRanger. Expertise 14Distracting ShotBow AttackIf Distracting Shot hits, it interrupts target foe's action but deals only 15 damage. If the interrupted action was a skill, that skill is disabled for an additional 20 seconds.2½10CoreRanger. Marksmanship 11Savage ShotBow AttackIf Savage Shot hits, your target's action is interrupted. If that action was a Spell, you strike for +24 damage.4½5FactionsRanger. Marksmanship 11Melandru's ShotElite Bow AttackIf this attack hits, your target bleeds for 20 seconds. If it hits a foe that is moving or knocked down, that foe takes +21 damage and is crippled for 12 seconds.218CoreRanger. Expertise 14Lightning Reflexes (PvP)StanceFor 11 seconds, you have a 75% chance to block melee and projectile attacks, and you attack 33% faster.445NightfallMonk. Protection Prayers 1Mending TouchSpellTouched ally loses two Conditions and is healed for 18 Health for each Condition removed in this way.2¾6CoreRanger. Wilderness Survival 11Apply PoisonPreparationFor 24 seconds, foes struck by your physical attacks become Poisoned for 12 seconds.7212NightfallRanger. Wilderness Survival 11Natural StrideStanceFor 6 seconds, you run 33% faster and have a 50% chance to block incoming attacks. Natural Stride ends if you become Hexed or Enchanted.212CoreNo Profession. UnlinkedResurrection SignetSignetResurrect target party member. That party member is returned to life with 100% Health and 25% Energy. This Signet only recharges when you gain a morale boost.3

The energy cost of attack skills, rituals, touch skills and all Ranger skills is reduced by 56%.

CoreRanger. Expertise 14Distracting ShotBow AttackIf Distracting Shot hits, it interrupts target foe's action but deals only 15 damage. If the interrupted action was a skill, that skill is disabled for an additional 20 seconds.2½10CoreRanger. Marksmanship 14Savage ShotBow AttackIf Savage Shot hits, your target's action is interrupted. If that action was a Spell, you strike for +27 damage.4½5CoreRanger. Marksmanship 14Pin DownBow AttackIf Pin Down hits, your target is Crippled for 14 seconds.78NightfallRanger. Marksmanship 14Burning ArrowElite Bow AttackIf this attack hits, you strike for +29 damage and cause Burning for 7 seconds.45CoreRanger. UnlinkedAntidote SignetSignetCleanse yourself of Poison, Disease, and Blindness, and one additional condition.14EotNRanger. Marksmanship 14Rapid FirePreparationFor 24 seconds, you attack 33% faster while wielding a bow.2212PropheciesRanger. Expertise 14DodgeStanceFor 11 seconds, you move 33% faster and have a 72% chance to block incoming projectiles. Dodge ends if you attack.230CoreNecromancer. Curses 3Rend EnchantmentsSpellRemove 6 Enchantments from target foe. For each Monk Enchantment removed, you take 49 damage.5220

Equipment

PvTemplate.pngApply ranger main equipment:
Turret ranger main equipment:
Crippling recurve bow:
Turret 40/40 curses:
Apply 40/40 prot:
Shield set:

Runes

You need to hit 14 expertise for break points on its energy reduction to be able to use your skills sufficiently frequently. In case of the apply ranger an 11-10-10 base distribution is picked to get most benefits out of the condition duration bonuses on the marksmanship and wilderness survival skills, reaching the break point with a major attribute rune. The apply ranger takes minor runes for the remaining attributes. As a turret ranger, you hit 14 expertise with a minor rune and headpiece, using the majopr rune for marksmanship to increase your damage output. A rune of restoration is only recommendable for the turret ranger as it also affects your own inflicted conditions.

Insignias

As your insignia you should pick scout's. In an 8v8 situation you are in general an unlikely target for spikes, so if your Apply PoisonCoreRanger. Wilderness Survival 11Apply PoisonPreparationFor 24 seconds, foes struck by your physical attacks become Poisoned for 12 seconds.15212 or Rapid FireEotNRanger. Marksmanship 14Rapid FirePreparationFor 24 seconds, you attack 33% faster while wielding a bow.5212 has been taken out, you're not put at an immediate risk. Spikes featuring elementalists will deal a lot less damage due to your inherent +30 armour against elemental damage, physical attacks can be worked around with your blocking stances. If you have trouble getting your preparation up you should call your monks for help anyway, so they can provide you with AegisCoreMonk. Protection Prayers AegisEnchantment SpellFor 5..10..11 seconds, all party members within earshot have a 50% chance to block attacks.10230. Apply has the same recharge when interrupted as complicate, so you should not cast apply on recharge. You can wait a few seconds and see if the Mesmer is targeting you and waiting for apply or if he did use it on somebody else. You may fake out an interrupt. You could also run out of the mesmer's range/vision by repositioning yourself behind your team to get poison up or push further on their flag. In skirmish and split defense situations, when you need your bonus armour against split elementalists most, nothing will interrupt your preparation anyway.

Weapon sets

Each build uses 5 weapon sets. Most of the time you won’t need the vampiric flatbow, so you can leave it in your inventory until it is required.

Interruption

Interruption skills

Distracting ShotDistracting ShotCoreRanger. Expertise 14Distracting ShotBow AttackIf Distracting Shot hits, it interrupts target foe's action but deals only 15 damage. If the interrupted action was a skill, that skill is disabled for an additional 20 seconds.2½10

This is probably the strongest interrupt available to a ranger. It has a low energy cost, and with a 10 second recharge, it is more frequently usable than mesmer interrupts. However distracting shot does very little damage and compared to other ranger interrupts 10 seconds is a long recharge. It is probably the strongest interrupt, because it disables any skill for 20 additional seconds including skills with no recharge like Resurrection SignetCoreNo Profession. UnlinkedResurrection SignetSignetResurrect target party member. That party member is returned to life with 100% Health and 25% Energy. This Signet only recharges when you gain a morale boost.3. As it interrupts actions rather than just spells, it can be used against any skill type. Because of the added recharge distraction shot is best used to shut down key skills. These can vary situationally from resurrection to monk or damage skills.

Savage ShotSavage ShotCoreRanger. Marksmanship Savage ShotBow AttackIf Savage Shot hits, your target's action is interrupted. If that action was a Spell, you strike for +13..25..29 damage.10½5

This skill is a very strong interrupt due to its recharge time of 5 seconds. Because of 14 expertise the energy cost is reduced from 10 to 4, so it can be used frequently. Just like distracting shot it works against any action. An interrupt of a spell skill deals additional damage which is especially important in skirmish situations. In general it can be used to interrupt skills when you want to save Distracting ShotCoreRanger. Expertise 14Distracting ShotBow AttackIf Distracting Shot hits, it interrupts target foe's action but deals only 15 damage. If the interrupted action was a skill, that skill is disabled for an additional 20 seconds.2½10 or it is currently recharging. It can be combined with poison spreading by interrupting different targets – which is a good opportunity for prediction interrupts. By spreading poison it is also very good to use it as a prediction interrupt.

Magebane ShotMagebane ShotNightfallRanger. UnlinkedMagebane ShotElite Bow AttackIf this attack hits, it interrupts target foe's action. If that action was a Spell, it is disabled for an additional 10 seconds. This attack cannot be blocked.10½5

A strong option for apply rangers, but it takes the important elite slot. It should only be used when interrupting the opposing team is expected to be your main role. Like Savage ShotCoreRanger. Marksmanship Savage ShotBow AttackIf Savage Shot hits, your target's action is interrupted. If that action was a Spell, you strike for +13..25..29 damage.10½5 it costs 10 energy (4 with expertise) and has a 5 second recharge, but instead of dealing extra damage when interrupting it gives spells an additional recharge of 10 seconds. Even though any action can be interrupted, the additional recharge time only applies to spell skills.

Concussion ShotConcussion ShotCoreRanger. Marksmanship Concussion ShotBow AttackIf Concussion Shot hits while target foe is casting a Spell, the Spell is interrupted and your target is Dazed for 5..17..21 seconds. This attack deals only 1..13..17 damage.25½5

This skill works entirely different the interrupt skills listed above. Concussion shot has an extraordinary energy cost of 25 (reduced to 11 by 14 expertise) and a low recharge of 5 seconds. It only works against spell skills, unlike the other skills which work against any action. Applying dazed means that the currently casted spell gets interrupted, the casting time of spells used while suffering from that condition is doubled and any attack will interrupt spells before taking into account any attack skill's effects. If you were to land a Distracting ShotCoreRanger. Expertise 14Distracting ShotBow AttackIf Distracting Shot hits, it interrupts target foe's action but deals only 15 damage. If the interrupted action was a skill, that skill is disabled for an additional 20 seconds.2½10 on a dazed target, an interrupted spell will not receive the additional 20 seconds recharge time. Concussion shot works best against elementalist splits and in skirmishes against single monks, but because of its high energy cost and multiple condition removal skills it is lacking in 8v8 situations.
Using interruption impactfully
Having a good ping and a good computer will help greatly. This will offer more time to land your interrupts on reaction. However, having a good ping and a good computer is not what makes you a good ranger. Even with an average ping you will still be able to hit most skills and just take away few options. It will be impossible to hit 3/4s, but you can play around it. There are a few things to keep in mind for hitting interrupts:

Reaction time

Ranger interrupts aren't solely dependent on your reflexes. In general (for rangers aswell as Mesmers) it is a good idea to enlarge the skill activation bar and to enable your sound effects. The larger activation bar will help you identify skills quickly and decise whether or not to interrupt them. The sound effects may tell you which skills are being used around you.

Bow based interruption specifics

Especially important for the ranger are attack speed and arrow flight time, as both determine how long it will take between your input and the interruption effect. A faster attack speed and a shorter distance to the target both decrease the time until your interrupt effect happens.
To change your attack speed you can change your bow type. In most circumstances it is best to use a recurve bow as it has the shortest arrow flight time, making it both hard to dodge your attacks in general and decreasing the time until your interrupting arrow hits. Secondly it's possible to use stances and preparations to improve your attack speed. The turret ranger uses Rapid FireEotNRanger. Marksmanship 14Rapid FirePreparationFor 24 seconds, you attack 33% faster while wielding a bow.5212 for this purpose, whereas most poison rangers resort to Lightning Reflexes (PvP)CoreRanger. Expertise Lightning Reflexes (PvP)StanceFor 5..10..11 seconds, you have a 75% chance to block melee and projectile attacks, and you attack 33% faster.1045 unless taking another utility skill instead.
The most important consideration for hitting your interrupts is having good positioning. Because of arrow flight time, the closer you are to your target, the easier it will be to hit your interrupts.
Note that interruption skills cause a delay of 0.75 seconds, so you can't attack or use another interruption right after you used one. A caster may use a one second activation time skill right next to you after you used an interruption on him and you can't do anything about it.
Lastly, make sure that your line of sight is not obstructed. You can't interrupt targets covering behind an object without pushing up to them.

Shield Guardian

Most current teams have two to three Shield GuardianFactionsMonk. Protection Prayers Shield GuardianEnchantment SpellFor 1..3..4 seconds, all party members in earshot have a 75% chance to block incoming attacks. If an attack is blocked, all allies in earshot are healed for 10..34..42 and Shield Guardian ends.51.520s in their backline. It has priority to take these out for your team to be effective.
  • Warriors switching targets to knock someone down may get blocked on their Devastating HammerCoreWarrior. Hammer Mastery Devastating HammerElite Hammer AttackIf Devastating Hammer hits, your target is knocked down and suffers from Weakness for 5..17..21 seconds.7 or Hammer BashCoreWarrior. Hammer Mastery Hammer BashHammer AttackLose all adrenaline. If Hammer Bash hits, your target is knocked down.6, ruining their chain.
  • Spikes after switching a target won't have a deep wound if the deep wound source is the first attack skill used and blocked.
  • You can't switch targets for interrupting, unless using Magebane ShotNightfallRanger. UnlinkedMagebane ShotElite Bow AttackIf this attack hits, it interrupts target foe's action. If that action was a Spell, it is disabled for an additional 10 seconds. This attack cannot be blocked.10½5. It will nonetheless trigger the party healing.
  • Whenever an attack hits a target enchanted with shield guardian, your opponents in earshot are healed for 28 to 38 health points. This party healing reverts a lot of your pressure's impact. In case of your poison spreading, 3.5 to 4.75 seconds of poison per block.
When your team is not splitting it has priority to interrupt shield guardian. It is often used in chains. This means that you should be alert if you see a shield guardian going up, that you know another one is going up aswell. You can either interrupt the next one (if you missed the first), or use Apply PoisonCoreRanger. Wilderness Survival 11Apply PoisonPreparationFor 24 seconds, foes struck by your physical attacks become Poisoned for 12 seconds.15212, since apply and shield guardian got roughly same recharge. This has two benefits: Your arrows won't get blocked and the opponent not party healed, but also you'll have an easy timer when the next SG's usually are being cast again.

Interrupting on reflex

Ranger interrupts are in general slower than mesmer interrupts. However, it is still possible to hit 3/4s. The key is that interruption on reflex is partially based on prediction and not entirely on reaction, especially for 3/4 skills. Whenever you know your opponent will have to cast something very soon, prepare for it so you can use your interruption as soon as the skill activation bar shows up. The difference to pure prediction is that you still try to wait until you see your target casting a skill. Interrupting on reflex takes more time to watch a single target than the other options.

Interrupting on prediction

This is the most unreliable way of interrupting, however sometimes it is necessary to use it. Interrupting on prediction is very useful when your ping isn’t good enough to reliably hit interrupts or when you are sure your target will cast a spell and interrupting it will cause a lot of pressure or even a kill. Hitting interrupts on prediction is easier when your frontline consistently does damage at the same time when they are calling spikes. It will also help if you are better at mind games with interrupts and faking skills than your target. If your opponent doesn’t notice that you want to interrupt him he won’t try to avoid the interrupt. During skirmishes you will learn by experience when your opponent will most likely cast skills. They will often cast a skill once they are in your aggro bubble, when their skills are recharged, when your target is getting low on health or when it switched from its shield to casting set. Wasting interrupts will give your opponents a window to cast skills, because your interrupts have an after cast, your skills will be on recharge and you wasted energy.

Interrupting on animation

This is probably one of the hardest methods of interrupting if you are new to it, but it is highly effective. You can only get used to it and get better by practicing this a lot. There are many important skills which take longer than one second to cast. These skills have different skill animations and most of the time also a signal or a sound when it is being cast. To observe these skills you will need a good field awareness. You will need to zoom-out your camera and have an overview of most casters. To make it easier to interrupt on animation it is important to position yourself well. Most of the time there will be two or three characters with long cast time. It is important to be able to see them and preferably be close to your target so you can swap with C+tab to your target.

Shutting down

Sometimes it is necessary to shut down a specific character. This can be done through two ways: Interrupting key skills and/or denying energy. When you are about to shut down a specific character you first have to know why you are doing so. Does it have to happen immediately (interrupt key skills) or will you need to shut someone down over a longer time period? These situations are little skirmishes which can be done within an 8v8 battle.
A GvG match evolves over time and sometimes your team is taking more pressure and will have to play defensive and sometimes you will have to play offensive. This takes different approaches on which skills you should interrupt and the importance (if you should focus more on spreading poison or camp a specific target).
The advantage of draining a target's energy is that it is hard on most casters to regain it if they have to keep playing 8v8. Draining energy is effective for the long term, but it also needs a long term focus from the ranger to interrupt his energy skills. Energy denial does not require the usage of the seldomly used Debilitating ShotCoreRanger. Marksmanship Debilitating ShotBow AttackIf Debilitating Shot hits, your target loses 1..8..11 Energy.1010. Interrupting energy management skills will cause an effective energy leak aswell. A necromancer with a disabled Angorodon's GazeEotNNecromancer. Soul Reaping 13Angorodon's GazeSpellSteal 45 Health from target foe. If you are suffering from a condition, you gain 11 Energy.5110 won't be able to spread hexes, an elementalist without attunement will run dry quite soon or reduce his skill usage, which both serves your purpose. Even if you can't take out an attunement, interrupting elementalists is going to hurt their energy management, as they won't get back energy from the attunement for successfully casting the spell.
Interrupting key skills is more a short term option. Interrupting DiversionCoreMesmer. Domination Magic 14DiversionHex SpellFor 6 seconds, the next time target foe uses a skill, that skill takes an additional 53 seconds to recharge.10312 or powerful damage skills will immediately put some pressure off your team and may prevent kills. To interrupt important skills you will need to know their recharge time so you can anticipate when it is going to be used the next time, allowing you to interrupt it on prediction or reflex. A skill like Shield GuardianFactionsMonk. Protection Prayers Shield GuardianEnchantment SpellFor 1..3..4 seconds, all party members in earshot have a 75% chance to block incoming attacks. If an attack is blocked, all allies in earshot are healed for 10..34..42 and Shield Guardian ends.51.520 is probably going to be used on recharge, so if you want to play offensively, keep an eye on each monk every 20 seconds to take out their shield guardians.
Some builds are more susceptible to one strategy over the other due to different energy management systems and skill dependencies. Decreasing the energy supply of a mesmer by taking out Drain EnchantmentCoreMesmer. Inspiration Magic 9Drain EnchantmentSpellRemove an Enchantment from target foe. If an Enchantment is removed, you gain 13 Energy and 88 Health.5220 may prove ineffective if he has Power DrainCoreMesmer. Inspiration Magic 9Power DrainSpellIf target foe is casting a Spell or Chant, that Skill is interrupted and you gain 19 Energy.5¼20 to compensate for it quickly.

Spreading Poison

Applying wide-spread pressure with Apply PoisonCoreRanger. Wilderness Survival Apply PoisonPreparationFor 24 seconds, foes struck by your physical attacks become Poisoned for 3..13..16 seconds.15212 is one of the main reasons why rangers are being played. Combined with frequent interrupts, it is what differentiates the ranger from other professions in 8v8 situations.
Poison is effective when you can spread it on multiple people. To do this you’ll need to have good target selection. Switching targets by using tab is easier and faster for this purpose than selecting them by clicking, because you are near certain that you will attack someone who hasn’t been poisoned yet. Using target closest foe allows to target an appropriate target if you happen to tab to a target which is out of your range.
Positioning is very important to interrupt skills, but it is just as important for poison spreading. Stand at the centre of the battle field so your arrows can hit all targets without having a long flight time or requiring you to move towards someone. You want to have a low chance that your arrows are dodged and you don’t want your targets to be obstructed. In most cases this means that you will position yourself between their midline and the backline.
Use Lightning Reflexes (PvP)CoreRanger. Expertise 14Lightning Reflexes (PvP)StanceFor 11 seconds, you have a 75% chance to block melee and projectile attacks, and you attack 33% faster.445 to attack 50% faster and spread much more effectively. Using your interruptions can be useful, but their aftercast delay may decrease your spreading effectivity. A poisonous spear has a shorter range, but decisively faster attack speed. This is most useful when the casters are standing close to each other anyway. The main downside is that you lose out on the ability to use your interruptions quickly.
Because lightning recharges has a 45 seconds recharge time you have to decide carefully when to use it. Will it maximize the pressure to use it for poison spreading, delay it a short while for more precise interruption or use it entirely differently for the ability to push deep with the blocking chance as a backup? It's ideally used once the your counters Restore ConditionPropheciesMonk. Protection Prayers 14Restore ConditionElite SpellRemove all Conditions (Poison, Disease, Blindness, Dazed, Bleeding, Crippled, Burning, Weakness, Cracked Armor, and Deep Wound) from target other ally. For each Condition removed, that ally is healed for 66 Health.5¾2 and Shield GuardianFactionsMonk. Protection Prayers Shield GuardianEnchantment SpellFor 1..3..4 seconds, all party members in earshot have a 75% chance to block incoming attacks. If an attack is blocked, all allies in earshot are healed for 10..34..42 and Shield Guardian ends.51.520 are on recharge.
If you are doing a lot of poison pressure you will most likely be camped with ComplicateFactionsMesmer. Domination Magic 14ComplicateSpellIf target foe is using a skill, that skill is interrupted and disabled for target foe and all foes in the area for an additional 12 seconds.10¼20. It is important to be able to play around this. Apply has the same recharge when interrupted as complicate, so you should not cast apply on recharge. You can wait a few seconds and see if the Mesmer is targeting you and waiting for apply or if he did use it on somebody else. You may fake out an interrupt. You could also run out of the mesmer's range/vision. If your apply got interrupted you should change your focus to interrupting.

Skirmishes

As a ranger you will engage in skirmishes, either against splits or by pushing flags. It is important to stay ahead of your target and anticipate its moves. Your goal is to dictate your game plan on the opposing team, disturbing theirs.
To win skirmishes you will need as much information as possible. You will need to know the map and its mechanics. You will have to know on which places you want to skirmish your opponent and which places you prefer to avoid a battle. In general you want these skirmishes to happen in an open area, unless you are pushing their flag and trying to bodyblock. One example for using the terrain is when you are pushing the flag on Frozen Isle. There are two areas where the flag runner will have to run over ice. The flag runner will get snared if he stops moving on the ice to cast a spell or dodge Melandru's ShotFactionsRanger. Marksmanship 11Melandru's ShotElite Bow AttackIf this attack hits, your target bleeds for 20 seconds. If it hits a foe that is moving or knocked down, that foe takes +21 damage and is crippled for 12 seconds.518's crippling. This gives you an opportunity to get good positioning and snare the flagrunner. Places you would like to avoid a skirmish are places with effects like the spores on Weeping Isle, places with many objects and bridges. You want to avoid bridges because most bridges are bugged and in specific situations your arrows will be obstruced.
Besides knowing the map, you will also have to know everything about your opponent. You will have to know his skills, his death penalty and his experience on that character. You will also have to know what his goal is. Is it late in the game and does their split have to kill NPCs, or does he just want to stall the game to keep his main team alive?

Defending splits

When you are defending against a split you will always be at an advantage over fighting in an open area. You will have NPCs to aid you in your battle. Although during the split you would prefer to kill your target, it is more important to keep your NPCs alive. This is because your NPCs will not resurrect, while the splitter will resurrect and he might get morale boosts, which nullifies your kill's impact. However, giving death penalty to a splitter is a huge advantage for future skirmishes, because your target will be easier to kill.

Split defense is going to be explained with an elementalist split, as it's both most common and the build you have most tools against. In this example there are two split elementalists:

Your maximum Energy is raised by 27.

CoreElementalist. Energy Storage 9Aura of Restoration (PvP)Enchantment SpellFor 60 seconds, you gain 1 Energy and are healed for 320% of the Energy cost each time you cast a spell.5¼20CoreElementalist. Air Magic 16Air AttunementEnchantment SpellFor 62 seconds, you are attuned to Air. You gain 1 Energy plus 30% of the base Energy cost of the Skill whenever you use Air Magic.10130CoreElementalist. Air Magic 16Lightning SurgeElite Hex SpellAfter 3 seconds, target foe is knocked down and struck for 106 lightning damage, and has Cracked Armor for 21. This spell has 25% armor penetration.10110PropheciesElementalist. Air Magic 16Chain LightningSpellTarget foe and up to two other foes near your target are struck for 90 lightning damage. This spell has 25% armor penetration.51026CoreElementalist. Air Magic 16Lightning StrikeHex SpellStrike target foe for 53 lightning damage. This spell has 25% armor penetration. If you are Overcast, that foe is hexed with Lightning Strike for 3 seconds. When this hex ends, that foe is struck again for 53 lightning damage.515FactionsElementalist. Air Magic 16Shock ArrowSpellSend out a shocking arrow that flies swiftly toward target foe, striking for 53 lightning damage. If Shock Arrow strikes a foe suffering from Cracked Armor, you gain 5 Energy plus 1 Energy for every 2 ranks of Energy Storage. Shock Arrow has 25% armor penetration.518PropheciesElementalist. Air Magic 16Windborne SpeedEnchantment SpellFor 14 seconds, target ally moves 33% faster.10¾5EotNMonk. Healing Prayers 10Patient SpiritEnchantment SpellFor 2 seconds, target ally is Enchanted with Patient Spirit. Unless this enchantment ends prematurely, that ally is healed for 90 Health when the enchantment ends. 5¼4
When your opponents are splitting with two, you will also have to defend with two, usually alongside your third backline character. When defending against two elementalists you want to lengthen the fight, so you will be able to pressure your targets. Before you will be able to pressure your targets they will need to be get low on energy, so they won’t be able to spam their healing skills. To create pressure you will have to combine a few core objectives of the ranger. You will have to keep poison and bleeding on both elementalists. You will also have to interrupt the skills which do most damage. Try to hit the skills which are most troublesome for your healer with Distracting ShotCoreRanger. Expertise 14Distracting ShotBow AttackIf Distracting Shot hits, it interrupts target foe's action but deals only 15 damage. If the interrupted action was a skill, that skill is disabled for an additional 20 seconds.2½10 and remove cracked armour from yourself with Mending TouchNightfallMonk. Protection Prayers 1Mending TouchSpellTouched ally loses two Conditions and is healed for 18 Health for each Condition removed in this way.5¾6. By camping one elementalist his energy will drop faster, but there’s a higher risk there will go too much damage through for your healer to handle. Most of the time after around 15-30 seconds the eles will get on lower energy and will get pressure. At this point it is important to change your focus: Instead of interrupting skills that do most pressure, you will have to cripple a target and focus on the elementalist which has Healing BreezeCoreMonk. Healing Prayers 8Healing BreezeEnchantment SpellFor 15 seconds, target ally gains +7 Health regeneration.1015. Taking this healing out may allow you to force a kill as you deal more pressure than Patient SpiritEotNMonk. Healing Prayers 10Patient SpiritEnchantment SpellFor 2 seconds, target ally is Enchanted with Patient Spirit. Unless this enchantment ends prematurely, that ally is healed for 90 Health when the enchantment ends. 5¼4 counters and your target can't easily escape.
Well-coordinated splits and will hide behind walls and use their skills more effectively. You will have to push up to create a line of sight and this means that your healer will have to push with you, thus forcing him into a dangerous position. In the end this is worth it, because now you will be able to support him with interruptions instead of just standing there and watch.

Splitting offensively

Splitting on ranger is rare. Back in the days it used to be a lot more popular, but because most builds are decent now at defending a ranger it has become riskier to split as a ranger. It can lead to big plays carrying your team to victory, but it could also ruin the game for your team and give any advantage away you had on mainteam.
The best time to be splitting is when the other team doesn’t notice that you’re going to split. This will give you time to kill NPCs or get good positioning. Tactically it is best to split when you won’t be able to accomplish anything on mainteam (as a team). It could be that your ping is too bad to reliably interrupt skills, or you can't apply pressure due to a counter like "It's Just a Flesh Wound."NightfallParagon. Motivation "It's Just a Flesh Wound."Elite ShoutTarget other ally loses all conditions. If a condition was removed in this way, that ally moves 25% faster for 1..8..11 seconds.52. In these situations you should go to split, because luring people away from the mainteam is more effective than staying there.
You could also go to split to cause chaos. Most of the time when the opposing team is winning and making kills they don’t know how to react properly to a splitting ranger, because they want to keep damage on mainteam to keep the pressure on, but don’t want to lose their third backline so they can lure the knights.
When you are splitting into their base you will be in a disadvantage over fighting in an open area, because you will get a lot more damage from NPCs attacking you and it will be harder to escape. This could be a problem when you take too much pressure from the NPCs, because you don’t have strong healing skills, unless replacing Resurrection SignetCoreNo Profession. UnlinkedResurrection SignetSignetResurrect target party member. That party member is returned to life with 100% Health and 25% Energy. This Signet only recharges when you gain a morale boost.3 with Troll UnguentCoreRanger. Wilderness Survival 11Troll UnguentSkillFor 13 seconds, you gain +8 Health regeneration.5310.
The most important part of a split is to stay alive. If you die you won’t be able to help your team for a while and you will get death penalty, which makes you prone to dying more often. To not die you will need to know if you can split, tactical insight, and good map awareness. You will have to know what the other team will send back and you will have to wait for opportunities to split when they can’t react to your split, because they are doing other things. Just remember that you are splitting to help your team (get pressure off, gain flag advantage or take out NPCs for the late game).
The ranger doesn’t have a lot of upfront damage and does not have self-heals on most occasions. However the ranger can still be a good splitter: The ranger is quick, has interrupts, snare, pressure and a condition or hex remove. These are all great assets for skirmishes. When you are splitting you will have to try to keep your health as high as possible while still killing NPCs if possible. If you know you can beat the defender in a 1v1 just go for the big plays, but keep in mind not to die because you aggroed NPCs and are taking additional damage.

Communication

Communication is key. If you want to optimize your performance you will need to know what your team is doing and your team needs to know what you are doing. As a ranger you usually have a good overview of what is happening on the map and have knowledge of movement and pressure of the opposing team. This is very important to communicate with your own team.
It is important to call interrupts on key skills. Distracting shots on important skills should be called, like when you have disabled Restore ConditionPropheciesMonk. Protection Prayers 14Restore ConditionElite SpellRemove all Conditions (Poison, Disease, Blindness, Dazed, Bleeding, Crippled, Burning, Weakness, Cracked Armor, and Deep Wound) from target other ally. For each Condition removed, that ally is healed for 66 Health.5¾2 or Healing BurstFactionsMonk. Healing Prayers 14Healing BurstElite SpellTarget ally is healed for 150. All party members in earshot of your target gain Health equal to the Divine Favor bonus from this spell. Your Smiting Prayers are disabled for 20 seconds.5¾4. It is also important that you should call the interrupts on skills your team is asking to interrupt. Do not forget to call what is preventing you from doing your job. If their midline is casting Blurred VisionCoreElementalist. Water Magic 14Blurred VisionHex SpellFor 10 seconds, target foe and adjacent foes are Hexed with Blurred Vision. While Hexed, those foes have a 50% chance to miss with attacks.10112, blind or FaintheartednessCoreNecromancer. Curses 14FaintheartednessHex SpellFor the next 15 seconds, target foe attacks 50% slower, and that foe suffers -3 Health degeneration.1018 on you all the time, ask for a removal.
Because you have such a good overview over the map as a ranger you will be moving around a lot. You will be pushing the backline, pushing flags, splitting or defending splits. You should call when you are doing these things so your team knows what is going on. You should call as well what is following you or what you are following and where to. In same cases you could also ask your frontline to support your push when you know it will force a kill or gains you positional advantage. An example could be that when you hit GuardianCoreMonk. Protection Prayers 11GuardianEnchantment SpellFor 6 seconds, target ally has a 50% chance to block attacks.514 on the third monk with Distracting ShotCoreRanger. Expertise 14Distracting ShotBow AttackIf Distracting Shot hits, it interrupts target foe's action but deals only 15 damage. If the interrupted action was a skill, that skill is disabled for an additional 20 seconds.2½10 while pushing and it is getting low on energy.

External Links

Источник: https://gwpvx.fandom.com/wiki/Guide:GvG_Ranger

Mod Doll Monday Giveaway (July 27 - Aug 3rd) Who Modeled It Best

Hi everyone,

Welcome to week three of our Mod Doll Monday giveaways! The question is simple: who models it best? You vote to help us decide and one lucky participant will receive the winning doll as well as the Limited Edition Liberty Jane Outfit. The winner will be selected at random on Monday, August 3rd, 2015, and notified within 48 hours.

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Vote Now & Enter To Win: [note, you enter through the entry form that is embedded on this page and appears just below this paragraph, if you don't see it, be sure to visit the page from your desktop or an alternate browser such as Google Chrome. It may not appear on all mobile devices. This is not a comment contest - in other words leaving a comment on the bottom of this page is not an official entry method]. The only required entry method is to vote in the poll to help us decide who models it best. The doll with the most votes will be given away with the Limited Edition Liberty Jane Outfit. One person will receive one of the dolls and the outfit. You can enter once, or gain multiple entries by completing the other entry methods, and increase your chances of winning. Please review all Terms and Conditions on the giveaway page before entering. While we wish we could run this contest everywhere, for legal reasons it is only open to eligible residents of the U.S. and Canada, not including Rhode Island. This contest is exclusively endorsed by Liberty Jane Clothing. Not associated with American Girl® Doll.

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More pictures of each doll:

We'd love to hear from you. Leave a comment and tell us - which dolls you think we should feature in the next few weeks. We shop - you enter - one lucky person wins!

Thanks everyone,

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Mod Doll Monday Giveaway (July 27 - Aug 3rd) Who Modeled It Best

Hi everyone,

Welcome to week three of our Mod Doll Monday giveaways! The question is simple: who models it best? You vote to help us decide and one lucky participant will receive the winning doll as well as the Limited Edition Liberty Jane Outfit. The winner will be selected at random on Monday, August 3rd, 2015, and notified within 48 hours.

More About Each Doll:

American Girl® Truly Me™ #64:With beautiful straight black hair, brown eyes, and an asian inspired look, this cute Truly Me™ doll is newly released for 2015. Doll also comes with original Truly Me™ booklet, outfit and box. Retail Value: $115

American Girl® Truly Me™ #62: With beautiful straight dark brown hair, brown eyes, and medium skin tone, this cute Truly Me™ doll is newly released for 2015. Doll also comes with original Truly Me™ booklet, outfit and box. Retail Value: $115

More About The Limited Edition Liberty Jane Clothing Outfit: The Liberty Jane Woomera dress is from the Fall 2012 Outback Libby collection has been created in a casual style, perfect for those warm summer days! The dress is made from a rayon blend fabric, that feels soft like a knit. It features a high-low hemline, gathered front yoke detail, cute faux buttons, and a velcro opening in the back. Black gladiator sandals also included. Retail value: $49.

Vote Now & Enter To Win: [note, you enter through the entry form that is embedded on this page and appears just below this paragraph, if you don't see it, be sure to visit the page from your desktop or an alternate browser such as Google Chrome. It may not appear on all mobile devices. This is not a comment contest - in other words leaving a comment on the bottom of this page is not an official entry method]. The only required entry method is to vote in the poll to help us decide who models it best. The doll with the most votes will be given away with the Limited Edition Liberty Jane Outfit. One person will receive one of the dolls and the outfit. You can enter once, or gain multiple entries by completing the other entry methods, and increase your chances of winning. Please review all Terms and Conditions on the giveaway page before entering. While we wish we could run this contest everywhere, for legal reasons it is only open to eligible residents of the U.S. and Canada, not including Rhode Island. This contest is exclusively endorsed by Liberty Jane Clothing. Not associated with American Girl® Doll.

a Rafflecopter giveaway

More pictures of each doll:

We'd love to hear from you. Leave a comment and tell us - which dolls you think we should feature in the next few weeks. We shop - you enter - one lucky person wins!

Thanks everyone,

Cinnamon


100 Comments

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Источник: https://www.pixiefaire.com/blogs/freebies-and-giveaways/43759493-mod-doll-monday-giveaway-july-27-aug-3rd-who-modeled-it-best

Metabolic Flux Analysis

Metabolic Flux Analysis: Methods and Protocols opens up the field of metabolic flux analysis to those who want to start a new flux analysis project but are overwhelmed by the complexity of the approach. Metabolic flux analysis emerged from the current limitation for the prediction of metabolic fluxes from a measured inventory of the cell. Divided into convenient thematic parts, topics in this essential volume include the fundamental characteristics of the underlying networks, the application of quantitative metabolite data and thermodynamic principles to constrain the solution space for flux balance analysis (FBA), the experimental toolbox to conduct different types of flux analysis experiments, the processing of data from 13C experiments, and three chapters that summarize some recent key findings. Written in the successful Methods in Molecular Biology series format, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step, readily reproducible protocols, and notes on troubleshooting and avoiding known pitfalls.

 

Authoritative and easily accessible, Metabolic Flux Analysis: Methods and Protocols presents protocols that cover a range of relevant organisms currently used in the field, providing a solid basis to anybody interested in the field of metabolic flux analysis.

Keywords

cell culture flux analysis metabolomics stoichiometry thermodynamics

Editors and affiliations

  • Jens O. Krömer
  • Lars K. Nielsen
  • Lars M. Blank
  1. 1.Centre for Microbial Electrosynthesis (CEMES), Advanced Water Management CentreUniversity of QueenslandSt. Lucia, BrisbaneAustralia
  2. 2.AIBNUniversity of QueenslandSt. Lucia, BrisbaneAustralia
  3. 3.Biology DepartmentRWTH Aachen UniversityAachenGermany

Bibliographic information

  • Book TitleMetabolic Flux Analysis
  • Book SubtitleMethods and Protocols
  • EditorsJens O. Krömer
    Lars K. Nielsen
    Lars M. Blank
  • Series TitleMethods in Molecular Biology
  • Series Abbreviated TitleMethods Molecular Biology
  • DOIhttps://doi.org/10.1007/978-1-4939-1170-7
  • Copyright InformationSpringer Science+Business Media New York2014
  • Publisher GRAPHIC Screenshot Studio Crack 1.9.98.98 download - Activators Patch Press, New York, NY
  • eBook PackagesSpringer Protocols
  • Hardcover ISBN978-1-4939-1169-1
  • Softcover ISBN978-1-4939-4159-9
  • eBook ISBN978-1-4939-1170-7
  • Series ISSN1064-3745
  • Series E-ISSN1940-6029
  • Edition Number1
  • Number of PagesXII, 316
  • Number of Illustrations19 b/w illustrations, 51 illustrations in colour
  • TopicsBiochemistry, general
    Enzymology
Источник: https://link.springer.com/content/pdf/10.1007%2F978-1-4939-1170-7.pdf
25.0 9.0 4.5 1.5 5.0 18.5 4.0
Manufacturers specification
-4-

2. MELTING AND INFILTRATION OF POWDERS

2.1 Factors Affecting The Powder Melting Rate

When a casting powder melts it forms a pool of molten slag on the meniscus of the steel, and this
pool supplies a constant feed of molten slag into the mould/strand gap (Fig. 2-1). This flow of slag
is essential to ensure that there is both good lubrication of the shell and the correct level of heat
transfer between the shell and the mould. It has been reported*1.2) that in order to avoid
longitudinal cracking and sticker breakouts, it is necessary to maintain a pool depth of more than
10 mm. The depth of the molten pool is governed by (i) the magnitude of the heat flux passing
from the steel meniscus through the liquid and powder layers, and (ii) the rate of melting of the
powder. The latter is controlled by the following factors:

(i) the amount and the particle size of the carbon particles present in the powder;

(ii) the type of carbon used (e.g. carbon black, coke breeze, etc) and the relative f.lux 4.75 Crack - Crack Key For U of
these different forms of carbon;

(iii) the melting range of the mineral constituents of the powders (it is possible to obtain
powders with identical chemical compositions, but with different melting ranges by
using different mineral constituents).

The heat transfer through the powder layers is dependent upon the casting speed and
consequently this will influence both the depth of the molten pool and the thickness of the liquid
slag flowing into the mould/strand gap.

The effect of changes of casting speed (vc) on the molten pool depth(3) is clearly shown in Fig. 2-2.
The infiltration of the liquid slag into the mould/strand gap is strongly influenced by both the
viscosity (i) of the molten slag, and the downward speed of the mould'*). Consequently it has been
proposed(S) that the term (qvc) provides the best criterion for the provision of optimum conditions
for lubrication and heat transfert.

The depth of the molten pool is a sensitive function of the value of (nvc) except in the range 1 to 3.5
poise m (steel) min-1, and consequently this range provides the most stable molten pool depth and
the most stable conditions for various casting parameters,* as can be seen from Fig. 2-3. The
incidences of longitudinal cracking and sticker breakout are related to the flow of slag into the
mould/strand gap and consequently any thorough investigation of these problems must include a
study of the factors affecting the melting rate and subsequent infiltration of the casting powders.

WolfiV uses the term (n.vc2), cf(qVf)

*In practice this range is restricted toquc = 2 to 3.5, since argon injection into the SEN will cause
the formation ofpinholes in the strand when n,ve is between 1 and 2
2.2 Mathematical Models For The Infiltration Of Molten Powder

Comparison Of Models Of Mould Flux Flow

In this section and Appendix 2-1 these symbols have been employed to denote the following
parameters:

a Oscillating Amplitude (m)


C Consumption Rate (kg/tonne)
c Specific Consumption Rate (kg/m2/s) "'
d Half Gap Thickness (m)
d Gap Length (m)
D Slab Thickness (m)
f Oscillation Frequency (cycles/min)
g Acceleration due to Gravity (m/s2)
h Shell Thickness (m)
hi Thickness of Molten Powder Pool (m)
K Coefficient of Solidification Contraction (1.6%)
L Slab Width
1 Gap Thickness (m)
P Static Pressure (N/m2)
R Gas Constant (Joules/mole. Deg)
Tm Powder Melting Point (K)
Ts Slab Surface Temperature (K)
u Molten Powder Velocity (m/s)
V,VC Casting Speed (m/s)
V0 Relative Moving Speed (m/s)
x Distance from Slab Surface towards Mould Wall (m)
y Distance Down Mould (m)
a Negative Strip Ratio
OQ Creep Constant (ms- kg)
o-i Coefficient of Thermal Expansion (1.355 x 10-5 m/m/k)
AG Activation Energy of Viscosity (J/mole)
AT Temperature Drop Across Shell (K)
p Powder Density (kg/m3)
PF Steel Density (kg/m3)
u Powder Viscosity at Temperature of Slab Surface
T Powder Elasticity (0.28 N/m2)

Introduction

This section describes a model which can be used to investigate the behaviour of different casting
powders under different operating conditions. The main use of the model is in predicting the
consumption rates of powders and the thickness of the liquid portion of slag film between the
strand and mould wall.

A number of models describing various aspects of mould powder behaviour have been written and
during the course of this work four of them have been investigated in some detail. This section
describes each of the models and gives the reasons for choosing the model in use, in preference to
the others.
-6-

Kor Model

Kor*6) used the NavierStokes equation for an incompressible fluid between a plate moving at
constant velocity (the slab) and an oscillating plate (the mould) as the basis for his analysis:

du dp d2u
p = +u
7"
dt 7"
dy d x;2
.(2.1)

From the solution of this equation Kor determined that the consumption rate was given by:
/ g (vee ) l 2I
p p) U\
c
\ 1 2 ii 2 /
. (2.2)
During the analysis he also determined the velocity profile in the slag flowing between the shell
and the mould, although this was not required in calculating the consumption rate.

The main drawback with this model is that no attempt was made to calculate the gap thickness
between the steel shell and the mould and thus known values were required. Also no account was
made of thermal effects f.lux 4.75 Crack - Crack Key For U the film.

Clausthal Model

This model<7> calculated a velocity profile in the slag flowing between the steel shell and the
mould from the following equation for the flow between parallel plates:

du u.d u
dt
dx 2
. (2.3)
Equation (2.3) was then integrated around the perimeter of the slab to give the consumption rate.
This analysis was then extended to cover the case of nonparallel plates. Fig. 24 shows the
conditions assumed to exist in the mould. Thus, in order to use this model, values must be known
(or calculated from solidification and solid state, thermal contraction data) for the thickness of the
gap at the meniscus and in the parallel portion of the gap together with the lengths of the non
parallel and parallel (up to the formation of an air gap) portions of the gap between the mould and
the shell. Also no account was taken of any thermal effects.

Niggel and Felder Model

Niggel and Felder used a thermomechanical approach^) to calculate both the gap thickness and
the consumption rate. This required a knowledge of the thermal conductivity of both solid and
liquid powders and estimates of the heat transfer and temperatures in the mould arid steel shell.
The basic equation used was:

K3
dp
C dy
A
G
l< S 3> +
\ V c G 2< S 3>
. (2.4)
where S 3 = T/Tm

N g(u)(u-l)dni

c
2
Gt(S) = ^ 3 f (u-l) g(u)dn -
(S-l) Ul
g(u)du

J (u-l)g(n)dn
G2(S) = 1 - - and g(u) = u ( u - l )
(S-l)J g(u)dn

Niggel and Felder also tried to include mould oscillation but the theory predicted that this has no
effect on powder behaviour. They also suggested that this method was only valid for low viscosity
powders.

NSC Model

In the NSC modele Ohashi calculated both the gap thickness and the velocity profile in the gap
and from these derived the consumption rate of the powder. As a starting point, Ohashi assumed
that the viscosity of the powder was affected by an external force (mould oscillation) and,
therefore, used a rheological approach.

Fluid lubrication theory was used to calculate the gap thickness and the velocity profile around
the majority of the perimeter of the slab, but on the corner it was assumed that the solidification
shrinkage of the slab dictated the gap thickness in this region. (The length over which this corner
gap is present was calculated as a relative effect of thermal contraction and the bulging of the
shell.)

This model is the most comprehensive of those published and is therefore being used at present. A
full description of the model is given in Appendix 2-1.

NSC Model Results

Fig. 2-5 shows the effect of viscosity and oscillation frequency on the predicted gap thickness.
Corner gap thickness is not known as this is dependent on the slab size (2100 x 200 mm in this
case) and is 1.6 mm which is far higher than anything obtained for the perimeter. The velocity
profile in this gap is shown in Fig. 2-6, while Fig. 2-7 shows the velocities in the corner regions.

Total slag consumption rate for the entire perimeter is affected by casting speed, viscosity and
oscillation frequency as shown in Figs. 2-8 and 2-9.

In comparison with plant data (Fig. 2-10) the model shows up reasonably well. It correctly
predicted that consumption rises with lower viscosity and casting speeds. The fact that in
general, calculated consumption rates are lower than measured values may be due to slag being
trapped in the oscillation marks on the slab shell.
-8

Conclusions

1. The NSC model of mould flux behaviour was chosen for use. It incorporates all of the
relevant flux and casting parameters and gives good agreement with plant results for
slab casting.

2. The Kor model does not calculate gap thickness and ignores any thermal effects.

3. The Clausthal model requires a detailed knowledge of the gap parameters, i.e. thickness
of both solidified and molten slag near the meniscus and from below the meniscus to the
beginning of the air gap together with the lengths of these regions. The thermal aspects
are also ignored.

4. The Niggel and Felder model is only valid for low viscosity powders. As the theory
underlying this model predicts that mould oscillation has no effect on powder
consumption this is omitted from the model.

2.3 Melting Rate Tests

Lidefeldt and HasselstromUO) devised an apparatus to determine the melting rate of casting
powders in which the molten powder in a conical cell dripped into a collector, which was weighed
continuously. Riboud@) carried out similar tests and concluded that the results were controlled
more by the fluidity of the powder than by the melting rate. In an attempt to devise a test which
would give an accurate simulation of the melting process in the mould, we applied the following
design criteria:

(i) The test should preferably be simple so that it can be used for routine testing of powders.

(ii) The heating should be unidirectional.

(iii) Crucibles should be sufficiently wide to minimise the possibility of bridging' in the
powder layers.

2.3.1 'Hot Plate' Experiments

Experimental

A silicon carbide Trot plate' furnace was used to provide the unidirectional heating, this had a
maximum operating temperature of 1400C. A schematic drawing of the apparatus is given in
Fig. 2-11. The hot plate was preheated to 1400C and then a crucible of graphite, alumina or iron,
with a known weight of powder was placed on the plate and heated for a selected time. The
amount of molten powder was determined by sectioning the crucible and measuring the volume of
the molten phase formed. Details of the experiments are given in Table 2.1.

Results and Discussion

The results of the various tests carried out are summarised in Table 2-1 and it can be seen that it
proved very difficult to decarburise the powders, even when thin layers of powders were used in
the experiments (e.g. 5,9 and 10). Consequently, it was concluded that higher temperatures
around 1500C were required to derive quantitative information from these experiments.
Unfortunately, the hot plate was incapable of operating above 1400C when the furnace lid was
removed. If the lid was left on the furnace the criterion of unidirectional heating was no longer
9-

applicable. Consequently, further tests were carried out on an induction furnace in an attempt to
derive values for the melting rates of different powders.

2.3.2 Induction Furnace Experiments

It was intended to measure the melting rates of powders by placing the powder on the surface of
molten iron at 1500C for a specified time and determining the volume of melted slag. However,
the heat transfer through the powder is also important in determining how quickly a powder will
melt and consequently the experiment was designed to provide heat flux density data (Q) from
which values for the thermal conductivity of the various layers (viz. liquid, sintered and powder)
could be calculated. A schematic diagram of the apparatus is given in Fig. 2-12. The powder was
placed in an alumina tube (19 mm i.d.) located on the surface of the molten iron at 1500C and the
heat flux density (Q) was measured with the aid of a copper finger sited on the surface of the
powder, and the measurement of the temperature rise (AT) of the water flowing through the
finger at a constant known rate. Dissolution of the alumina refractory by the molten slag was
prevented by lining the tube with platinum foil.

Several experiments had to be aborted because the powder column collapsed and fell into the steel
melt. Only two complete runs were obtained; the data are summarised in Table 2-2.

The disintegration and collapse of the powder layers was so frequent that it was decided that this
experiment was not suitable as a routine melting rate test. However, valuable data could be
obtained for the effective thermal conductivities (k) of the various layers by analysis of the data
listed in Table 2-2. These values of k are in agreement with expected values, the low value for the
sintered phase (0.26 Wm-lk-l) indicating the porous nature of this phase.

X-ray analysis of the various layers revealed the presence of cuspidine in all three phases and
combeite and CaF2 were also detected in the decarburised powder layer. It was also noted that the
region of the liquid layer contained a sub-layer of melted slag particles surrounded by a carbon
network.

2.4 Heat Flow Through The Casting Powder Above The Meniscus

Slag Dip Experiments

The temperature profile in the powder above the steel meniscus was derived by inserting a probe
into the powder during plant trials. The probe consisted of four wires (mild steel, copper,
aluminium and solder) and the lengths of these were measured after removal from the powder;
the length of the wires established the positions of the steel meniscus and 1085,660 and 183C
isotherms respectively. Two trials were carried out on Powder L9 and one each on powders L7 and
L8, the results are given in Figs. 2-13 to 2-16, respectively.

Analysis Of The Heat Transfer Data

The powder consists of three layers (molten, sintered and powder) and the temperature profiles,
given in Figs. 2-13 to 2-16, were drawn by assuming that the sintered and powder phases existed
over the ranges (melting temperature 660C) and (660-183C), respectively. Similar
temperature profiles to those shown in Figs. 2-13 to 16 have been reported by Japanese
workers*1 M2). The calculated temperature gradients for the various layers are given in Table 2-3.
Further analysis of the results is difficult since no heat flux density measurements were recorded
in the plant trials and there are no thermal conductivity data available for these powders.
10

However thermal conductivity data for the powder and sintered phases of other casting powders
have been reported recently*13).

The aluminium wire on melting in the sintered, porous phase would probably leave an air gap and
thus it could be argued that the thermal conductivity through this layer would approximate to
that of a gas (0.08 Wm-lk 1 ). Values obtained in Section 2.3 indicated that the sintered layer
around this gas was very porous, and thus had a low thermal conductivity. The heat flux density
(Q) was calculated using the expression, Q = -k(dT/dx) and the value k = 0.08 Wm-ik-1 for the
porous phase and this was used to derive values of the thermal conductivity for the powder phase.
The values obtained for Q and k (powder) are given in Table 2-3, the latter being in agreement
with reported values*13* for powder and spherodised mould fluxes, 0.24 and 0.44 Wm-ik-1,
respectively.

It is difficult to analyse the data for the liquid layer since it is known that the upper part contains
molten drops held in a skeleton of carbon and there may be a substantial heat transfer coefficient
associated with this interface. Furthermore, it is difficult to attribute a value to the effective
thermal conductivity of the liquid layer since there will be a substantial contribution from
convection and radiation conduction.

2.5 References

1. Ogibayashi S et al
Nippon Steel Tech, Report 1987,34,1

2. Koyama K et al
Nippon Steel Tech. Report 1987,34,41

3. RiboudPV
Research Contract 7210.CA/131/311,810 Report EUR 9560.1983

4. Anzai E, Sigezumi I
Trans ISIJanan 1986,26, B 97

5. WolfM
AIME Elee Furnace Proc: 1982,40,335

6. KorGJW
An Analysis of the Fluid Flow of Liquid Mould Powder in the Space Between the
Continuous Casting Mould and the Steel Shell
US Steel Corporation

7. Mathematisches Modell fur Schmierwirkung der Giessschlacke in der


Stranggusskokille
Final Report on ECSC Contracts 7210.CA/131/311/810, Report EUR 9560.1984

8. NiggelCh and Felder E


Lubrication by Slags of the Continuous Casting of Steel
Research Contract EEB-1-117-F, Report EUR N.9339,1985

9. OhashiT
Characteristics of Mould Powder and its Effect on the Surface Quality of Slabs
Mannesmann Continuous Casting Conference 1980
11

10. Lidefeldt H and Hasselstrom P


4the Int. Iron and Steel Congress - Continuous Casting held London, May 1982, pubi.
Metals Soc, Paper 10

11. Nakano T et al
Nippon Steel Tech Report 1987.34.21

12. Sakurayo T et al
F.lux 4.75 Crack - Crack Key For U of Mannesmann Continuous Casting Conference in Dusseldorf, October 1980

13. Taylor R, Mills K C


Ironmaking and Steelmaking 1988.15 187
12

TABLE 2-1
DETAILS OF 'HOT PLATE' EXPERIMENTS

Powder Crucible

Temp Time Observations


Ezpt (C) (mins)
Int
Mass Dimens-
Type Material
(g) ions
(mm)

1 L8 20 C 25x56 1400 7 Powder did not melt.


Microscopic examination
revealed small grains of melted
powder in a 'sea' of carbon +
unmelted powder.

2 20 C 25x56 1400 10 As above

3 20 C 25x56 1400 20 Some decarburisation of top 10


mm of powder but no bulk
melting
4 L8 25 AI2O3 32x64 1400 20 Some decarburisation but still
no bulk melting. Weight loss
EditPlus Crack v5.4 Build 3527 + Serial Key Free Download (2021) 9.5%

S 25 AI2O3 74x15 1400 20 Top half of powder


decarburised; centre was a
'sintered crust', bottom layer -
not decarburised.
6 LI 50 Fe 57x49 1400 20 Most of powder was
decarburised, a sintered layer
formed at the bottom.

7 50 Fe 57x49 1400 20 All powder was decarburised;


the bottom layer consisted of
goodsync reviews sintered and semi-molten
phases

8 25 Fe 57x49 1400 20 Formed sintered and semi-


molten mass

9 25 Fe 57x49 1400 20 Initial powder layer 5 mm:


results as in Expt. 8.

10 25 Fe 57x49 1400 30 Initial powder layer 5 mm;


results as Expt. 8.
13

TABLE 2-2

RESULTS OF HEAT FLUX EXPERIMENTS

H20 Liquid Sinter Powder


Flow Q
Run AT Observations
Rate (C) Wm-2
(C) d k d k d k

1 0.15 0.5 1500 Experiment aborted


since column
collapsed into bath
due to melting of
clamps
2 0.15 0.4 1500 14.8 13 0.5 7 0.26 28 0.6
xl03
3 1500 10 20 18 Experiment without
Cu-finger. T (surface)
187C
Powder kept
collapsing into melt -
more powder added.

Units: Layer Thickness (d) mm : Thermal Conductivity (k) Wm-1k-1


Flow Rate: l/min-1

TABLE 2-3

CALCULATED VALUES FOR THERMAL PROPERTIES


DERIVED FROM SLAG DIP EXPERIMENTS

(dT/dx) Kmm-2
Q k(powder)
Powder
Wm-2 Wm-1k-1
Liquid Sinter Powder

L7 (1) 50 70 17 5600 0.33


(2) 39 65 16 5200 0.33
L8 42 125 17 10,000 0.59
L7 40 100 100
14

Mould

Glasiy slag layer

Crystalline lag
layer

Liquid slag layer


Liquid steel

Solidified steel
hell

Motion of layers

FIG. 2-1
SCHEMATIC REPRESENTATION OF THE
VARIOUS LAYERS OF CASTING POWDER
FORMED IN THE MOULD

Casting
'Speed (m/min)

1.3-

1.1- /

m m
Depth 2 min time
(mm)
20-

io- 1 2 1 4 3
t Ve (poise m/min)

FIG. 2-2 FIG. 2-3


THE EFFECT OF CASTING SPEED VARIATIONS IN THE MOULD
CHANGES ON THE DEPTH OF THE TEMPERATURE, HEAT
MOLTEN POOL TRANSFER AND THE LIQUID
SLAG FILM THICKNESS AS~
FUNCTION OF THE PARAMETER (nv c )
15

Steel Shell

Mould

FIG. 2-4

ASSUMED SLAG BEHAVIOUR FOR CLAUSTHAL MODEL


16

0.35-,

0.3-
50 cpm
0.25

3 0.20
C
3 0.15
H
A
H
0.10-
(h
m
o
0.05-

0.00-t "T" T - i

nVIDIA GeForce Experience Crack 2 4 5 6 7 10
0
Viscosity (Poise)

FIG. 2-5

EFFECT OF VISCOSITY AND OSCILLATION FREQUENCY ON


PERIMETER GAP THICKNESS

0.0250 -

0.0225 -
\ 1.5 m/min
\
0.0200 - \
\
\
\
e 0.0175 - \
\
e 1.0 m/min^
PH 0.0150 -
H
PM
O
id
0.0125-
Ui
a
0.0100-

0.0075-
0)
> 0.0050-

Zentimo xStorage Manager 2.3.1.1281 Free Download with Crack 0.0025-

0.0000-1 1 1 1 1 1 1 1 1
0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16
Distance from Slab Towards Mould (mm)
FIG. 2-6
EFFECT OF CASTING SPEED ON VELOCITY PROFILE IN GAP
(MAIN PORTION OF PERIMETER) "
17

0.5 m/min
1.0 m/min
1.5 m/min

g 0.02-

0.00 i 1 1 1 1

0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75


Distance from Shell Towards Mould (nun)

FIG. 2-7

EFFECT OF C ASTING SPEED ON VELOC ITY PROFILE IN GAP


(CORNER REGIONS)

3.5n Slab S i z e 2100 x 200 nun


Mould O s c i l l a t i o n : 100 cps
3.0-
0)
c 2.5-
O
p

J? 2.0
c
O 1 5
P
CU

ra L O '
c
o
o
0.5-

0.0 1 1 1 1 1 1 1
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75
Casting Speed (m/min)

FIG. 28
EFFECT OF C ASTING SPEED AND POWDER VISC OSITY ON
THE C ONSUMPTION RATE
18

3.5-
Slab Size 2100 x 200 mm
Casting Speed: 1.0 m/min
3.0-

c 2.5-
s
Oi
.* 2. 0 -
c
H 1.5 \ 150 cpm
4J \
& \
n 1.0 - \
e
0 100 cph.
u
0.5-
50 cpm
0.0 -i r 1 1 r
3 4 5 6 7 10
Viscosity (Poise)

FIG. 2-9

EFFECT OF POWDER VISC OSITY AND OSC ILLATION FREQUENC Y


ON POWDER C ONSUMPTION RATE

According
According tt oo Model
Model j Plant
_x P l a t e Grades a t ^ 0. 8 5 m/min j T r i a l
_# S t r i p Grades a t ^ 1. file matching software - Activators Patch m/min ) a t a

c 0.45 -\
o 0.85 m/min
o
o. 0.40 - 1.20 m/min
ni
w 0.35 -l
0.30 -t-
2 3 4 5 6
V i s c o s i t y (Poise)
FIG. 210
EFFECT OF MOULD SLAG VISC OSITY ON C ONSUMPTION RATE:
COMPARISON OF PLANT TRIAL DATA WITH NSC MODEL
-19-

\ / / / 1 4 0 0 C y / y V - SiC hot plate


f f f f f Heat Flow
f.lux 4.75 Crack - Crack Key For U FIG. 2-11
f.lux 4.75 Crack - Crack Key For U SCHEMATIC DIAGRAM OF HOT PLATE E XPE RIME NTS

/H20

Thermometer
(a)

Copper Finger

op * > * Clamp
\W\ Alumina Tube
/ A
/ Pt Foil
apple music on xbox one / A
RF Coils. -*o /
/
/
Molten
/ Graphite
Steel
f
1500C / C Crucible

Alumina Tube
. . r i- -i^n Decarburised
KD)
^''"Tn Powder Layer
Sintered Layer
Molten Drops
Surrounded b y Carbon
Molten Layer

FIG. 2-12
(A) SCHE MATIC DIAGRAM OF THE APPARATUS USE D IN THE
INDUCTION FURNACE E XPE RIME NTS
(B) SCHE MATIC ILLUSTRATION OF THE LAYE RS FORME D IN THE TUBE
20

T
Meniscus 400
200 600 < 11200 1600
Temperature C M "il
O
nat
o bo
<->
ii
<u
S

FIG. 2-13
THE TEMPERATURE PROFILE IN THE POWDER L9 FROM TRTAT. 1
21

7(n

Meniscus T
200 400 600 < 800 1000 o 1600
Temperature (C)

o
OH
t* be
O .5
5S
O 0)
o* S

FIG. 2-14
THE TEMPERATURE PROFILE IN THE POWDER L9 FROM TRIAL 2
22

Equation of Line is:


Y = .975436E02 X +21.4392
Correlation C oefficient = .83617
95% Confidence Limits for the
points
14 points in File

Meniscus 0
1600
Temperature (C )
1C4->

lOJ p-4
O
PU
u hl)
o
%+->
Q)
o
PU S

FIG. 215

THE TEMPERATRE PROFILE IN THE POWDER L7


-23-

70'
Equation of Line is:
Y = .529211E-04 Xt2 .100593 X+l +56.595
topaz remask 5.0 1 crack - Activators Patch R squared = 84.4868
95% Confidence Limits for the points
39 points in File

Meniscus 0
fe 200 400 600 5pv.00 1000 3
o
ti
o Temperature (C)
J co
-10
o
O b
(IH C

FIG. 2-16

THE TEMPERATURE PROFILE IN THE POWDER L8


24-

APPENDIX21

In order to calculate the powder consumption rate it is necessary to calculate the


gap thickness (between the slab and the mould) and the velocity profile of the semimolten powder
in this gap.

A major factor in determining the flow characteristics is the viscosity of the powder. Information
on viscosities is readily available, but the viscosity is affected by the force being exerted on the
powder by the mould oscillation. Ohashi has derived equation (A21.1) to give the effective
viscosity:

u" = u ( l + 4 n 2 f 2 i n 2 r l
.(A21.1)

The viscosity is also varying across the gap due to the temperature drop. This is given by:

. (A21.2)
where

Q
f.lux 4.75 Crack - Crack Key For U ~ ITHTT"/
m s
Applying fluid lubrication theory to the gap, the basic equation defining the flow is:

8x \ ox / dy
(A21.3)

Assuming djj = 0 and with the following boundary conditions


dy

u = Vc at x = 0
and u = 0 at x = 2d

equation (2.3) is integrated to give:

Qx
z 2 f 2 _ !_ 2 s j:2i Q* oQ Qx Q
4pg(l+4n fW )d fQx ^ Qe" - e e
+ (e
u
uQ 2 ti rrs "- ,
1 e "
Q V

. (A21.4)
which defines the velocity profile in the gap.
-25

The gap thickness is obtained by integrating equation (A2-1.3) to obtain the pressure P and then
substituting the statistic pressure difference for P:

d= VQ,UV /36g(p p -pXl + 4 n V )


1 F
.(A2-1.5)

where Qi = Q2(l-Qe-Q-e-Q)/(l+e-2Q-Q2e-Q-2e-Q)

V0 is the average relative speed of the slab with respect to the mould and is given by:

V0 = 4 fa sin (1-a) n + (l-2a) Vc


. (A2-1.6)
and
1 1. -l( V c \
a = - - sin ( J
2 n V2nfW
.(A2-1.7)
In the corner regions the shrinkage of the solidifying steel creates a greater gap than above, and
the gap here is:

di = D K/2
. (A2-1.8)

The length over which this is effective is a relative affect of thermal contraction and the bulging of
the shell

x = a.a ATV I V 2h /J
o . (A2-1.9)
To"
By integrating the flow around the whole perimeter the consumption rate is obtained.
26-

3. STICKER BREAKOUTS

3.1 Review Of The Published Work On Sticker Breakout

The occurrence of sticker breakouts has frequently been linked with the nature and the
performance of the casting powders employed. If measures are to be taken to eliminate sticker
breakouts, it will be necessary to answer two queries:

(I) Why do some powders produce a higher incidence of sticker breakout than others?

(ii) Why do some batches of powder (with a good overall record on sticker breakout) produce
sticker breakouts?

It will be seen that much of the published work relates to the detection and subsequent remedial
actions which can be taken to avoid sticker breakouts; some work has been reported on the effect
of the composition of the powder on sticker breakouts but little work has been reported on the
effect of batch to batch variations on breakouts.

3.1.1 Detection Of Sticker Breakouts

Heat Flux Measurements

Heat flux measurements have been used to detect imminent sticker breakouts by employing
thermocouple arrays located in the mould. Ohasi et aid), Tsuneoka et aK2' and Kurihara et al<3)
have all reported measurements made with these detection systems; a typical temperature-time
trace, revealing an imminent sticker breakout, is shown in Fig. 3-1. Matsushita et al(*) observed
(rom heat flux measurements that (i) a hot tear develops, and this is initiated at the middle of the
fixed side, and (ii) sticker breakout occurs when "hot spot descending speed" (v0) is between 0.35
and 0.85 v<, where vc is the casting speed. Subsequently, Matsushita et al<6> concluded that the
"hot spot1* was due to shell breakage, but neither the magnitude of the temperature rise nor the
rate of increase could be used with certainty to predict breakout. They concluded that the
propagation velocity of the tear (Horn nose1) was 0.75 (0.15) vc. They also used Fourier
transformations to analyse the results of T(mould)-(time) plots, and concluded that the
temperature transition associated with sticker breakout exists in a certain zone.

Friction Measurements

Nakamori et aU6J> monitored (i) the current required to vibrate the mould and (ii) the vibration
acceleration of the mould to derive frictional force measurements in the mould. They found that
this produced characteristic variations just before sticker breakout occurred (Fig. 3-2) and with
this system they were able to detect 60% of the sticker breakouts which occurred.

Remedial Action To Avoid Sticker Breakouts

Non-sinusoidal oscillations have been used to lower the incidence of sticker breakouts. Suzuki et
al?) hav studied the effect of non-sinusoidal oscillations on the frictional forces by determining
the pressure difference between the inlet and outlet of the hydraulic cylinder. This quantity
corresponds to the (inertiaforceof the mould) + (friction force inside the mould (AFf)), the inertia
force could be deduced separately from the pressure difference in idling periods. In Fig. 3-3 it can
be seen that the AFf increases as the casting speed (vc) increases, and AFf was found to be smaller
in the case of non-sinusoidal oscillations. It was considered that this was due to (i) an increase in
-27

powder consumption, and (ii) the speed of the mould relative to that of the shell decreased with
non-sinusoidal oscillation and thus resulted in lower friction forces at high casting speeds.

3.1.2 Thories For The Cause of Sticker Breakouts

Crystallisation Index Of Powder

Sorimachi et aldM2) reported that the incidence of breakouts was related to the crystallisation
index of the mould powder. This index was determined by quenching the liquid slag from the
mould into a stainless steel receptacle with subsequent metallographic examination of the
quenched sample. Breakouts decreased when (i) basicity (CaO/SiCt) decreased, and (ii)
crystallisation temperature decreased (Figs. 3-4 and 3-5).

Imai et aU13> reported that the presence of gases increased both the crystallisation index (Fig. 3-6)
and the viscosity of the slag (Fig. 3-7). The relative crystallisation index was determined in these
experiments by X-ray diffraction. They suggested that as the viscous friction force accounted for
80-90% of total friction, the presence of gases (Ar, CO2 or air) in the slag could thus increase the
viscous friction force to a level where it exceeded the tensile strength of the shell. This would
result in restraint of the shell and a breakout would occur in due course.

3.1.3 Heat Flux Variations Caused By Changes In Casting Speed

It is known that sticker breakouts are more likely to occur after periods where the casting speed
(vc) has been varied. These conditions cause variations in the mould temperatures*14* (Figs. 3-8(a)
and (b)) and when these data are presented in the form of plots of mould temperature versus
casting speed (Figs. 3-9(a) and (b)) a hysteresis in the results is revealed. Breakouts occur when
there is either too much or too little heat extraction from the mould, as can be seen from Fig. 3-10
which shows the recorded heat transfer plotted as a function of the casting speed for various casts.
Thus it would appear probable that sticker breakouts are related to the hysteresis observed in
both the mould temperature and heat transfer. The hysteresis can be accounted for by the
changes which occur in the depth of the molten pool (H). When vc is changed suddenly a certain
time AirDroid Desktop Crack required before these changes work their way through into changes in the depth of the
molten pool and the thickness of the slag layer (d). Two cases are discussed below:-

(i) When vc is decreased, both H and d will increase, thus when vc is restored to its original
value there will be a time lag before the molten pool depth (H) (and subsequently d),
revert to their steady state values and in this interim period the relatively thick slag
layer will result in low values of heat flux and mould temperature.

(ii) When vc is increased, both H and d will decrease, thus when vc is restored to its original
value both H and d will remain below their equilibrium values until steady state
conditions are attained and consequently the heat flux and the mould temperature will
both remain relatively high during this interim period.

This type of sticker breakout is particularly prevalent in high speed casting.

3.1.4 Frictional Forces In The Mould

Tokiwa et al<7 > calculated the frictional forces in the mould arising from an insufficient flow of
molten casting powder into the mould/strand gap. They derived values for the frictional forces in
the mould for these conditions; this was found to vary only slightly from the value for normal
conditions.
28

Mizukami et a l (9,10) produced a mathematical model to predict friction forces in the mould. The
tensile stress (at) parted magic mac - Free Activators calculated and compared with the high temperature strength (%) as a
function of casting speed, taking into account the physical properties of the mould powder. For a
casting speed of 1.8 m min-l it was calculated that Ob>Of for a position 50 mm below the meniscus,
but Ob < Of at a depth of 200 mm; thus it was necessary to improve lubrication by using a powder
with low viscosity and low melting point. It was proposed that the oscillation mode should have
the negative strip (NS) taking a critical value given by

8 8 1
N ^. - '. )

where t1 and t2 are times at which v m = vc. For non-sinusoidal oscillation this requires that the
time when the mould is ascending should be longer than when it is descending. Non-sinusoidal
oscillation decreased the liquid friction by about 40%.

3.1.5 Formation Of A Pseudo-Meniscus

Tsuneoka et al(2) made the following observations of sticker breakouts:

(i) The oscillation marks have a characteristic V-shape, fanning out from the sticking point
(Fig. 3-11).
(ii) The pitch of the oscillation marks in the 'constrained' region is smaller than that in the
sound portion.

(iii) Shell thickness in the ruptured portion (shown as A in Fig. 3-11) is larger towards the
meniscus, cf smaller in normal section (B in Fig. 3-11), as can be seen in Fig. 3-12.

They proposed the following theory, which is shown diagrammatically in Fig. 3-13:

(i) At stage 2 - "constrained shell" is separated from sound shell.

(ii) Molten steel enters this gap and solidifies on each portion of shell (marked X, Y) and

shown in stage 3.

(iii) This newly-formed shell is then separated again (stage 4).

(iv) F.lux 4.75 Crack - Crack Key For U steel solidifies again at stage 5.


This process is repeated, and the pseudo-meniscus descends towards the bottom of the mould until
a point is reached where breakout occurs.
Tsuneoka et al(2) also developed a 3-dimensional, non-steady state, heat transfer model to
simulate this mechanism; it can be seen from Fig. 3-14 that there is excellent agreement between
the calculated and measured temperature transitions.

These workers also analysed the forces affecting the rupture and repair of the shell. During
normal solidification there are two forces operating, the frictional force (F,) between the shell
and mould and F gthe force due to shell gravity. Relationships for F^ and F g were derived and an
expression for the shell yield stress (FJ was also obtained. Plots of the magnitude of F, F g and F c
f.lux 4.75 Crack - Crack Key For U 29-

versus the distance from the meniscus are given in Fig. 3-15(a) and it can be seen that the shell
cannot rupture in the mould, as the condition F> Fj,-Fg is always satisfied.
r

However, when a 'constraint' occurs, the shell rupture which occurred at the meniscus (described
above) propagates to the mould bottom at rates of avc and vc, respectively, where a and are
constants relevant to the casting and width directions. As the force due to shell gravity is offset by
buoyancy, the inertia due to oscillation, F 0l is taken into account and a relationship derived.
Assuming that the yield stress of the ruptured shell formed during the period of negative strip (tn)
attained maximum value at the end of this period in every oscillation, they calculated values for
F0, FJJ and F0. It can be seen from Fig. 3-15(b) that when the pseudo-meniscus has travelled 300
mm below meniscus F 0 < (F^-F,), the rupture will propagate downwards as a consequence of the
friction force caused by ferro-pressure. This will occur despite the fact that the constraining force
at the meniscus is released by the solidification contraction of the constrained shell. In order to
recover the situation, the operation must meet the condition that (F o >(F u -F 0 ). Fig. 3-16
represents the control variables, v c and tn, necessary to prevent breakout. If the terms a and
(defined above) exceed the value of 0.75 used in the calculations for Fig. 3-16 further deceleration
would be required to recover the situation.

3.1.6 Causes Of The 'Constraint'

Tsuneoka et al<2> examined the stuck shell and found evidence of copper adhering to the shell and
also carbon-concentrated structures which they attributed to contact of the meniscus with
unmelted casting powder. They suggested that the constraint occurred because the coefficient of
friction between the mould and the strand was increased by solid/solid contact as a result of the
insufficient flow of liquid slag.

Mukai et al<15> also examined the shell stuck in the mould after a sticker breakout and observed:

(i) Traces of molten metal droplets (which possessed a carburised structure and cavities) in
the vicinity of the sticking point.

(ii) A carburised structure in the vicinity of the sticking point.


o
(iii) The metal droplets and carburised structure had similar compositions to that of the
molten steel except for the C content.

(iv) The carbon content was close to 4% for the metal droplets.

They concluded that the cavities were due to the formation of CO(g) on solidification and that the
carburised structure was due to the formation of local regions with high carbon concentrations in
the meniscus. They also suggested that unmelted casting powders were the carbon source of these
decarburised regions and that this powder caused a blockage to slag infiltration. Since the
carburised region would have a low melting point, the shell would not be repaired sufficiently at
the time of negative strip, and this would lead to sticking of the shell to the mould.

3.1.7 Comments On The Theories Of Sticker Breakouts

It would appear the theory due to Tsuneoka*2) explains most of the facts and observations, but it
does not explain how the 'constraint' occurs, other than suggesting that an interruption to the slag
flow was responsible. However, the increased carbon levels in the shell have been noted by
Tsuneoka et al<2> and Mukai et al<ls>, and thus it seems the 'constraint' could be caused by the
decrease in the liquidus temperature of the steel, as suggested by Mukai. Furthermore, there is
30

strong evidence that the solid slg film attached to the mould remains more or less unaltered
throughout the casting operation. It can be seen that the sequence of events shown in Fig. 3-13
does not take the infiltrated slag film into account and the latter would serve as a partial barrier
to heat flow from the mould. A tentative represenentation of the sequence of events occurring
during a sticker breakout, where the slag layer is also taken into account, is shown in Fig. 3-17.

It is proposed that the essential features in the events leading to a sticker breakout are:

(i) A carbonaceous agglomerate (probably alumina) is forced to the edge of the mould (Stage
1).

(ii) Carbon diffuses out of the 'agglomerate and forms a zone of carbon-rich steel in the
locality of the agglomerate, the steel in this zone has a low melting point and
consequently does not freeze (Stage 2).

(iii) The agglomerate blocks the flow virtual dj pro 8.2 crack - Crack Key For U slag into the mould/strand gap (Stage 2) and thus
there is a melt-back of the solidified slag film which results in an increase in both the
heat transfer and mould temperature.

(iv) The increased heat transfer results in the solidification of the steel which forms a
pseudo-meniscus separated from the original meniscus.

(v) Both the pseudo-meniscus and the original meniscus become thicker as the process
proceeds.

(vi) The gap between the original meniscus and the pseudo-meniscus will not be fully
repaired in negative strip time because of the low melting point of the steel and the
relatively low heat transfer associated with the thick slag layer (Stages 4 and 5), and the
tear will redevelop during positive strip periods in subsequent oscillations.

(vii) In the second and subsequent oscillations (e.g. Stages 7 and 8) melt-back of the solid slag
film would occur at a lower level, so the temperature transient would appear to move
down the mould as observed.

(viii) The absence of a liquid slag layer would result in solid/solid friction which would account
for the increased friction forces recorded. Breakout would occur when these forces
exceeded the shell yield stress.

There is anecdotal evidence that a sticker breakout often occurs during periods when the casting
conditions would result in the formation of relatively large amounts of alumina. However it is not
known whether a sticker breakout can occur without the formation of a carburised, low melting
shell in the meniscus region.

The observation of Sorimachi et alUMZ) that the incidence of sticker breakouts increased with
increasing basicity of the mould powder can not be accounted for the powder to dissolve alumina
(see Section 3.10) since the reverse would have been expected. If this observation is generally
applicable, the lower frequency of cracking must be due to the thicker slag layer produced by the
high silica, high viscosity, molten powders.
.31 -

3.2 Summarv Of Factors Relevant To Sticker Breakout

3.2.1 Casting Conditions Favouring Sticker Breakout

(i) Where the casting conditions have resulted in the formation of relatively large amounts

of alumina (see Section 3.5).

(ii) Where zirconia is produced by the erosion of the SEN (see Section 3.5).

(iii) When the casting speed is suddenly changed, which causes insufficient or excessive

extraction of heat from the shell.

3.2.2 Differences Between Stuck And Unstuck Portions Of The Shell

(i) The oscillation marks have the characteristic V-shape fanning out from the sticking
point; the pitch of these marks being smaller than in the sound portion of the shell.
(ii) The shell thickness in the stuck portion increases towards the meniscus which is the
opposite of that observed in a sound shell.
(iii) Iron droplets are formed on both sides of the stuck shell in the vicinity of the sticking
point, none were observed in the sound shell.
(iv) The stuck shell has a carburised structure whereas the sound shell had no carburised
regions.

(v) Cavities can be observed in the stuck shell which is associated with the formation of
CO(g) bubbles, whereas none were observed in the sound shell.

3.2.3 Possible Mechanism For Sticker Breakout

It is possible that sticking breakout occurs by the following mechanism:

(i) There is a blockage to the flow of slag into the mould/strand gap by large agglomerates
sited at the meniscus.
(ii) In this region, there is carbon diffusion into the steel which results in the formation of a
high carbon, low melting point, shell which does not heal in the positive strip time.

(iii) Breakout occurs when the frictional forces exceed the yield stress for a steel shell.

3.2.4 Possible Sources Of Blockage

Carbonaceous materials which block the flow of slag into the mould/strand gap are:

(i) Alumina particles associated with casting powder.


(ii) SEN and tundish stopper rods materials which may be eroded or be ripped away when
the alumina agglomerates attached to the refractory wall are flushed out by a build up of
pressure.
32-

3.3 Prediction Of Sticker Breakout By Qn-Plant Monitoring

In order to investigate the casting parameters which affect sticking breakouts, plant trials have
been carried out on a slab caster which permitted the logging of the relevant casting parameters.
The slab caster was a twin strand machine and signals were logged from both strands.

The logging system, consisting of a microcomputer with isolated measurement pods, stored the
data during casting from a large number of casts in order to acquire information for as many
breakouts as possible. The system had a variable sampling rate (up to a maximum of 12 per
minute) for recording all the plant signals, this was sufficient to monitor any unexpected changes
in signals prior to breakout. These data were processed with other relevant recorded data,
available as needed, for any casts which terminated in a breakout.

The logged signals were also correlated with slab surface quality inspection data which are
available on computer. This allowed relationships for the prediction of slab surface quality to be
developed. For this part of the work a slower sampling rate could be used, and further details are
given in another section of the report.

The following signals were logged:

Casting speed
Mould oscillation
Mould water flow rates
Zone 1A flow rate
Zone IB flow rate
Edge zone flow rate
Mould water inlet and outlet temperatures
Tundish stopper position
Mould metal level and rate of change

Fig. 3-18 shows a schematic illustration of the data logging system and the casting parameters
logged. The relevant plant signals were wired through isolating amplifiers to an isolated
measurement pod in the caster control room, and were connected via a serial link to a
microcomputer, situated a safe distance away, which controlled both the logging and recording.

Additional information to be used in the analysis, where appropriate, included:

SEN immersion depth


Samples of used and unused mould flux
Measurements of slag depth in the mould
Measurements of powder consumption rate

3.3.1 Monitoring Mould Water Temperatures

Examples of the processed logged data for casting speed, mould water flows, mould water
differential temperatures, and the calculated mould heat flux for the 2 broad faces of the mould
taken from a cast that was aborted due to a sticker breakout, are shown in Figs. 3-19 to 3-23,
respectively.

The mould water differential temperatures (Fig. 3-20) were measured between the common inlet
temperature and the separate outlet temperatures for each face of the mould. This trace was
fairly constant except at the position equivalent to the drop in casting speed (Fig. 3-19) from 0.67
-33-

to 0.56 m/min for 27.6 minutes. There was a time lag of approximately 1.5 minutes before the
speed drop produced a detectable change in the mould water differential temperatures and the
mould heat flux.

The sticker breakout occurred on the outer radius of the strand and from Fig. 3-22 it can be seen
that there was no detectable change in the mould heat flux from the outer radius when compared
to that of the inner radius, prior to the breakout.

The final 10 minutes of casting are shown in more detail in Fig. 3-23 to show this more clearly.

Several breakouts have been monitored with this system and it has proved too insensitive to
detect either the occurrence of the breakout or any adverse conditions leading up to the breakout
by the monitoring of the mould water differential temperatures.

In order to improve the sensitivity of the mould heat flux measurements, the response time of this
system can be decreased by repositioning the resistance thermometers to be as close as possible to
the outlets from the mould plates, but whether these improvements would be sufficient to produce
a reliable system has not been established.

This system has also been used to assess any relationship between heat flux in the mould and slab
surface quality, details of which are given in Section 4.2.

3.3.2 Monitoring Of Mould Temperatures By Thermocouples

A more accurate method of measuring mould copper temperatures and hence the heat flux
transferred through the mould can be achieved by the installation of an array of thermocouples
into the mould walls. The temperatures recorded by these thermocouples will give indications of
the conditions in the mould, and analysis of the MediaHuman YouTube Downloader Licenses key can be used to recognise problems
arising during casting.

Figs. 3-24 to 3-26 show the casting speed, the thermocouple reading from a position 80 mm below
the meniscus on the inner radius, and the mould cooling temperature rise for the same mould
plate, respectively, for the same slab machine cast. It is readily seen that the mould water
temperature rise trace (Fig. 3-26) reflects the change in the casting speed but little else is
discernible. However, the thermocouple trace (Fig. 3-25) reflects other events in the mould as
well as the casting speed, e.g. the larger peaks and troughs are indicative of changes in the mould
level.

In order to predict a sticker breakout from thermal flux measurements it is necessary to


understand the cause of the heat flux changes under these conditions. Fig. 3-27 shows the
development down the mould of a potential breakout due to sticking in six stages. Alongside the
shell development are temperature traces (a and b) from 2 thermocouples implanted in the mould
wall at two depths below the meniscus and in the same vertical line. Fig. 3-27 (1) shows normal
casting conditions, but if a localised sticking occurs between the newly formed shell and the mould
at the meniscus level, a tear will occur as the strand is withdrawn and the stuck portion rises with
the mould oscillation. During negative strip the tear will heal slightly and then pull away again
during the next oscillation cycle. This is repeated at each successive mould stroke and the tear
slowly advances down the mould at approximately 60% of the casting speed. The tear also
advances outwards in the horizontal direction at an equivalent rate to the vertical direction. This
results in a typical shaped shell with characteristic oscillation marks as described in Section 3.1.5.
34

Under normal casting conditions the upper mould thermocouple would register a higher
temperature than the lower one, indicating a thinner, hotter shell at that position. As the thin
tear region passes the upper thermocouple position the melt back of the slag flm causes the
temperature to rise as shown in Fig. 3-27 (3). As the tear region passes further down the mould
and the shell thickens above the tear, the temperature begins to fall and will eventually fall to
below the normal casting temperature.

The lower thermocouple temperature will follow a similar pattern as the upper, and at a certain
point the temperatures will cross over as in Fig. 3-27 (5). This system can be linked to alarms
which would respond to these characteristic temperature traces. On the alarm the strand can be
stopped or slowed down (see Fig. 3-16) to allow the tear region to heal enough and so the stuck
portion can be pulled free from the mould and the shell will not rupture on exit from the mould.

As sticking can occur at any position of the meniscus around the perimeter of the mould there
must be enough pairs of thermocouples to cover the whole mould, but from an engineering
viewpoint it is preferable to keep the number of thermocouples to a minimum. Consequently the
pairs of thermocouples must be positioned close together to ensure that if a sticker occurred at a
point mid-way between them, the thermocouple response would still allow sufficient time for
preventative action. Thermocouple separation/distances will therefore depend upon casting
speed, length of mould below meniscus and the response time of the casting machine to slow down
or stop.

3.4 Quality Control Tests For Powders

Quality control testing of mould fluxes was carried out on plant to specify whether a particular
batch of powder had deviated from that specified by both the manufacturer and the plant
technical departments.
r
A wide range of tests, both simple and sophisticated, have been used to examine the various
properties of the powder/slag, as shown in Table 3-1. Most of the tests require sophisticated
equipment, and are time consuming and are, consequently, not ideal as routine tests. Routine
Q.C. tests must (i) be quick and easy, (ii) use equipment that can be quickly or permanently set up
and (iii) give results which are reproducible and which can be interpreted quickly and acted upon.

Ideally the tests should be such that they do not deform the powder structure, and represent the
in-mould situation as closely as possible; these conditions are not easy to simulate.

The following relatively easy tests were performed:


*r
Bulk density - This measures variations in characteristics such as agglomeration
properties and moisture content. Powders with a low bulk density
are more porous and are better insulators.

Size gradings - The distribution of particle sizes is important since it can affect the
melting rate of the powder. Samples with a large volume fraction of
small particles or granules will have a lower bulk density. This will
also give an indication of the flowability of the powder, i.e. the
ability of the powder toflowevenly, and so produce an even
thickness layer of powder on the meniscus.
-35-

Chemical composition - including water content - can be compared with the


manufacturer's specification and the basicity and the viscosity
can be calculated from the chemical composition.

Mould dips - Molten slag depths can be accurately measured in the mould
using a device consisting of four metal wires with different
melting points, viz. mild steel, copper, aluminium and solder.
When dipped through the powder and slag layers and into the
steel, the mild steel wire will melt near the slag/metal interface;
the melting point of copper (1080C) is close to that of the
powders in use; the aluminium (melting point 660C) melts in
the sintered powder layer and the solder (melting point 183C)
close to the surface of the powder (Fig. 3-28). The temperature
profile through the powder/slag layer can then constructed from
these data.

3.4.1 Variability Of Casting Powder Supplies

Although some incidences of sticker breakout occur when the casting conditions favour the
formation of alumina, other breakouts occur suddenly and inexplicably without any apparent
build up in alumina. It is generally believed that the casting powder is responsible for this latter
type of breakout. Appreciable variations in either the chemical composition or the particle size
distribution of a specific batch of powder could be one of the possible causes of the breakout.
Consequently, the variability of casting powder supplies has been monitored for twelve batches of
powder L7, three batches of L4 and two batches of L2 (Table 3-2).

3.4.2 Variations In Chemical Composition

The results of the investigation are summarised in Table 3-2 which shows the maximum and
minimum levels recorded for the most important components of the powder. It can be seen that
the extreme bounds of composition rarely deviate from the specified range except for levels of free
carbon and to a lesser extent, AI2O3. In all probability, the small AI2O3 variations would have
little effect on the performance of the powder. However, variations of the carbon content, as large
as those shown in Table 3-2, could have a marked effect on the rate of melting of the powder and
consequently could lead to the build up of a carbon-rich agglomerate.

3.4.3 Variations In Particle Size Distribution

The results on the variability of the particle size distribution for different supplies of casting
powders are summarised in Table 3-3. It can be seen that the variations (i) within a bag, (ii)
within one pallet, (iii) from pallet to pallet and (iv) from batch to batch were all monitored. The
following observations can be made about the particle size distribution:

(i) The variations within any bag are small.

(ii) The variations within one pallet, and from pallet to pallet and from batch to batch are all
considerable.

(iii) As might be expected, these variations, in percentage terms, are the greatest for the
most populous particle size range (>250 urn for L7 and < 125 um for L4 and L2).
36

The particle size distribution could have an appreciable effect on the rate of melting of the powder,
and sticking breakouts occurred when using powder L7. Unfortunately no samples of the bags
used just prior to the breakout are available, but variability in supplies could be a contributory
factor.

3.4.4 Variations Of Chemical Composition With Particle Size Distribution

The chemical compositions of the various particle size fractions have been determined on three
bags of casting powder from two different batches of L7. The results indicated (i) that there is
surprisingly little variation in the levels of CaO and SO2, and (ii) the smallest size fraction ( < 125
um) was higher in A1 2 0 3 (5.4 cf 4.9%) and Na 2 O (7.1 cf 6.4%) and lower in F (6.6 cf 5.3%) and free
carbon (8.6% cf 11%) than the larger (>125 urn) fractions. Clearly the free carbon variations
could have a significant influence on the casting performance, particularly where the smallest
particle size range deviated appreciably from the norm.

3.4.5 Conclusions On Variability Of Powder Supplies

(i) The variations in both the free carbon contents and the distribution of particle sizes
recorded in the supplies monitored in this investigation were considerable and could lead
to appreciable differences in the melting rate of the powders.

(ii) These differences in melting rate could lead sequentially to marked changes in the depth
of the molten slag pool, the thickness of infiltrating slag film and the heat flux extracted
from the shell. Such changes in heat flux could lead to sticker breakout^) (Section
3.1.3) and longitudinal cracking (Section 4.1).

3.5 Monitoring Of Casting Techniques Related to Slag Alumina Levels

3.5.1 Introduction

It has been stated previously that it would appear that some sticker breakouts are associated with
casting conditions which result in the formation of alumina. Consequently, in an attempt to