CA1152722A - Method and apparatus for controlling caster heat removal by varying casting speed - Google Patents
Method and apparatus for controlling caster heat removal by varying casting speedInfo
- Publication number
- CA1152722A CA1152722A CA000348900A CA348900A CA1152722A CA 1152722 A CA1152722 A CA 1152722A CA 000348900 A CA000348900 A CA 000348900A CA 348900 A CA348900 A CA 348900A CA 1152722 A CA1152722 A CA 1152722A
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- CA
- Canada
- Prior art keywords
- heat removal
- mold
- speed
- removal rate
- actual
- Prior art date
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
Abstract
METHOD AND APPARATUS FOR CONTROLLING CASTER
HEAT REMOVAL BY VARYING CASTING SPEED
Abstract of the Disclosure Breakouts due to insufficient skin thickness exiting below caster mold are prevented. Minimum mold heat removal rate is defined in terms of casting speed. mold faces, mold size, material grade and tundish superheat, then calculated, indicated and compared to actual measured values of heat removal rate. As a result of the comparison, caster preset speed correction is taken to automatically maintain the mold heat removal rate above the minimum level where breakouts occur.
HEAT REMOVAL BY VARYING CASTING SPEED
Abstract of the Disclosure Breakouts due to insufficient skin thickness exiting below caster mold are prevented. Minimum mold heat removal rate is defined in terms of casting speed. mold faces, mold size, material grade and tundish superheat, then calculated, indicated and compared to actual measured values of heat removal rate. As a result of the comparison, caster preset speed correction is taken to automatically maintain the mold heat removal rate above the minimum level where breakouts occur.
Description
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Background of the Invention Field of the Invention This invention relates broadly to continuous metal casting. More particularly, this invention relates to a method and apparatus for controlling caster mold heat ¦ removal to prevent breakouts by varying casting speed. The ¦ invention may be used in all sizes of strand casting machines ¦ in which solidification of a shell with liquid core starts ¦ in single or multiple water-cooled mold faces.
10 ¦ Description of the Prior Art Generally, it is desirable to operate a continuous caster of metal billets, slabs and the like at the highest speeds possible to meet maximum production and utilization l goals. However, in practice only optimum strand throughput 15 l at a predetermined allowable speed prevails, rather than at maximum speed, so as to avoid major disruptions in continuous caster operations. One such major disruption occurs when an improperly solidified strand breaks out l because of insufficient heat transfer in the mold.
20 ¦ It has been discovered that numerous factors exist which lead to insufficient heat transfer when casting molten steel for example. First, low mold rnetal level due to either loss of metal level control or a buildup of an I excessive slag layer when using a mold powder. The low s 25 ¦ metal level causes a reduction of residence time in the mold ana thus r ducln~ heat transfer. Secona, a builaup of
Background of the Invention Field of the Invention This invention relates broadly to continuous metal casting. More particularly, this invention relates to a method and apparatus for controlling caster mold heat ¦ removal to prevent breakouts by varying casting speed. The ¦ invention may be used in all sizes of strand casting machines ¦ in which solidification of a shell with liquid core starts ¦ in single or multiple water-cooled mold faces.
10 ¦ Description of the Prior Art Generally, it is desirable to operate a continuous caster of metal billets, slabs and the like at the highest speeds possible to meet maximum production and utilization l goals. However, in practice only optimum strand throughput 15 l at a predetermined allowable speed prevails, rather than at maximum speed, so as to avoid major disruptions in continuous caster operations. One such major disruption occurs when an improperly solidified strand breaks out l because of insufficient heat transfer in the mold.
20 ¦ It has been discovered that numerous factors exist which lead to insufficient heat transfer when casting molten steel for example. First, low mold rnetal level due to either loss of metal level control or a buildup of an I excessive slag layer when using a mold powder. The low s 25 ¦ metal level causes a reduction of residence time in the mold ana thus r ducln~ heat transfer. Secona, a builaup of
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~ A1203 content of the mold slag during casting of aluminum--¦ killed steel which causes mold slag to become viscous and gummy and results in a significant loss in mold heat transfer.
¦ Third, in a rectangular mold, loss of narrow face taper ¦ increasing a strand-mold gap which reduces heat transfer on one or both narrow faces. Fourth, too high a casting speed which reduces residence time of a thin walled shell in the mold, thereby causing insufficient amounts of heat removal.
l Fifth, excessive temperature of liquid metal entering the 10 ¦ mold which increases the mold heat load. Sixth, casting of wider and thicker slabs which reduce the surface area per volume of metal cast, thus causing more mold surface area to be used to extract the metal superheat and reducing the area l available for formation of solid skin.
15 l Caster operators are taught that a thicker skin l may be formed in a caster mold to prevent breakout by ¦ manually reducing caster speed. This is based on known mold heat removal rate QA per square inch of strand surface l which is speed dependent. However, there is lacking a prior 20 ¦ art relationship defin ng when mold heat removal rate is insufficient, or in what manner caster speed corrective action should be taken. J. Shipman et al in U.S. Patent No.
4,006,633 disclose how to satisfactorily measure and determine l mold heat removal rate in single and multiple mold coolant 25 l flow circuits, but lacks direction as to determining minimurn level of mold heat removal rate as well as caster speed correction. Earlier prior art is similarly deficient, or if mold heat remova] is suggested, it requires a comprehensive ~$27Z2 ¦ analysis and determination of strand thermal and stress pro-¦ files all along the strand beyond the mold which must be ¦ combined wîth mold parameters.
Summary of the Invention 5 ¦ One of the objects of this invention is to provide an improved method and apparatus for continuously controlling caster mold heat removal rate which will overcome the fore-going difficulties.
l Another object of this invention is to provide a 10 ¦ method and apparatus for determining caster minimum level of mold heat removal rate and caster corrective action to be taken in the control of mold heat removal.
Still another object of this invention is to provide an improved method and apparatus for controlling caster mold heat removal without considering such parameters as mold level3 cast strand thermal or stress profiles.
The foregoing objects are attainable in casters with fixed or adjustable mold structures having cooling means for solidifying strand casting, either single or multiple coolant flow circuits, and variable drive means with a presetable feedback loop for controllably withdrawing the strand as cast. The apparatus comprises:
(a) first plural means for determining actual heat removal rate of the cooling means during strand casting;
(b) second plural means for determining a calculated , minimum level of heat removal rate re~uired of the cool g mean s to prevent strand breakout during casting;
., ~l~5~ Z2 (c) third means for comparing outputs from only means (a) with means (b) and as a result generating a speed error signal based on a predetermined difference between the actual and calculated heat removal rates; and (d) said third means including control means for modifying the preset speed of the caster drive means as a function of only the speed error signal so that the actual heat removal rate will exceed the calculated minimum level ¦ thereof.
10 ¦ The method, as practiced on such apparatus, includes ¦ the steps of:
¦ (a) determining actual heat removal rate of the cooling ¦ means during strand casting;
¦ (b) determining a calculated minimum level of heat removal rate according to either:
I C x ~T2 x w x t x p l QL2 k2 + ~ 6 (w+t) S = BTU/min./in.
¦ or C x ~T2 x w x t x p 2 l 2 3r-6 (w+t) - = BTU/in.
¦ where:
20 ¦ k2 = predetermined constant l Cp = liquid specific heat = BTU/# per F. = 0.19 ¦ P = density, ~//ft.3 S = speed, inches per min. (IPM) t = slab thickness or narrow face of mold, inches ~T2 = superheat above liquid temperature, = TT--TL, F
TL = Liquidus temperature, F.
TT = Tundish temperature, F.
w = slab width or wide face of mold, inches, ~5~ 2 ¦ as required o:f the cooling means to prevent strand ¦ breakout during casting;
¦(c) comparing outputs from only step (a) with step (b) l and as a result generating a speed error signal ¦ according to either:
l ~QL = QLli - QL2 ~, ~ speed corrective action needed, ¦ or l ~QL = QLli - QL2 ~, Take speed corrective action, ¦ based on a predetermined difference between the ¦ actual and calculated heat removal rates; and ¦(d) modifying the preset speed of the caster drive means ¦ as a function of only the speed error signal so that the actual heat removal rate will exceed the calculated minimum level thereof.
Brief Description of the Drawings FIG. 1 is a block diagram of a continuous metal caster having a fixed size mold with variable cooling, metal feed, computing and speed control systems in which there is incorporated the present invention.
FIG. 2 is an instrumentation diagram of a computer used to calculate the minimum level of mold heat removal rate useful with either single or multiple faced mold designs in the FIG. 1 embodiment.
FIG. 3 is an instrumentation diagram of the comparator-controller used to automatically select the wide or narrow mold face of an adjustable rectangular mold with the lowest actual mold heat removal rate for use with the FIG. 1 embodiment.
~ ~L15~1Z2 Description of the Preferred ~mbodiment Referring to FIG. 1, continuous metal caster 10, or simply caster 10, will be presumed to have undergone start-up procedures and is operating in essentially a steady-state mode. Superheated molten metal was teemed from ladle 11 into tundish 12 and then fed controllably as hot metal stream 13 into caster mold 14. Mold 14 heat transfer, which is regulated a predetermined amount by coolant flow control valve WCV, effects solidification so that as cast strand 15 leaves mold 14 it continually consists of a liquid core and outer shell or skin of sufficient thickness to prevent a breakout.
Mold 14 instantaneous heat removal requirements vary as a function of mold hot metal level, mold size, other parameters described below, and cast strand 15 withdrawal rate as determined by pinch roll 16 operating in a preset æpeed control loop also described below. In order to accommodate a fluctuating mold heat transfer in the single coolant flow circuit shown in FIG. 1, flow control valve WCV
is interposed between coolant supply 17, mold 14 and coolant return 18 and operates in response to a flow control signal from computer 19. In the case of mold 14 being an adjustable rectangular structure with four independent coolant flow circuits, each circuit has a flow control valve WCVi inter-posed between coolant supply 17 and coolant return 18.
, Computer 19 instrumentation is exemplified by an assembly of conventional analog-type computer and control elements such as are found in a Foxboro Spec. 200 analog computer.
,~
~as~2 easurlng rneans and computer means for determ~n~ng ¦and controlling actual mold 14 heat removal corresponding ¦to computer 19 is disclosed in the Shipman et al Patent No.
~ ¦4,oo6,633. This patent is directed to both single and '~` 5 ¦multiple coolant flow circuits having a separate instrument ¦measuring and controlling computer for each flow circuit.
¦Instead of each computer and measuring device having an ¦"i"th subscript, they carry N,S,E,W, designations corre-¦spondlng to either wide or narrow mold faces as is done ¦hereinbelow.
¦ Regardless of the number of coolant flow circuits ~' ¦used in mold 14, each computer 19 per~orms two functions.
. ¦The first function of computer 19 is to generate a conven-¦tional coolant flow control signal WCVi for its associated '~ 15 ¦flow control valve WCV in response to a coolant flow signal :ii from a respective flow transmitter WT and a preset flow signal (not shown herein). The second function of computer 19 is to use Eq. 1, for example, to produce an actual heat removal Qi signal for comparison and recording purposes in response to signals representing coolant flow rate WTi, ,~ coolant temperature in and out TIi,TOi with respect to mold , 14, all being fed to computer 19.
~'i, Actual heat removal rate may be expressed as , either QL or QA for use with the present invention. QL is ,~ 25 preferred herein because it references heat removal to mold face peripheral length "L', or width "w" and/or "t" thickness ln terms of BTU/min./in. of mold face length which is not dependent upon a speed parameter. ~Ihereas, QA if used ! ~
''i ~'' .
~ ,........... . :, - -- - : . - .
, . . .
~LlSZ7~2 references heat removal to strand face sur~ace area in terms of BTU/in. and is speed dependent. In practice, each computer 19 determines what is designated hereinafter as QL
actual heat removal rate per unit length of mold face as 5follows:
W x ~T x k x C
QLl 1 L 1 _ P _ BTU/min./in. Eq. 1 where:
W = coolant flow rate in GPM
~Tl = TO-TI = coolant temperature rise, F.
kl = constant = 8.33 lbs. per gal.
Cp = specific heat BTU/lb. per F. = 0.19 L = dimension of mold face in inches, and Al = QLl S Eq. 2 where:
S = speed of cast strand leaving mold, inches/min.
Mold 14 face length "L" dimensions shown in FIG. 1 are also fed to computer 19 in addition to coolant flow and thermal parameters. When mold 14 has a single face ,20 and single coolant flow circuit, the "L" dimension corre-sponds to mold face peripheral length data which is fed as a single input "L" (not shown) from a mold length data source to computer 19. Alternatively, when mold 14 is an ad~ustable rectangle having four faces each with an inde-pendent coolant flow circuit, the "L" dimension consists of mold wide face "w" and mold thickness or narrow face ~It~
dimensional data which are fed from respective mold data sources to corresponding inputs to separate computers 19.
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¦ Still referring to FIG. 1, computer 20 determines ; ¦ whàt is designated hereinafter as QL2 calculated minimum ~ ¦ mold heat removal rate per unit length of mold peripheral i ¦ face so as to be on the same basis as QLl. It has been ¦ discovered that the minimum level of mold heat removal rate necessary to prevent a breakout during caster 10 operation may be defined by the following equations:
Q Qs + Qsh Eq. 3 C x QT2 x w x t x p QL2 k2 + 3456 (w+t)S = BTU/min./in. Eq. 4 10 QL2 = QA2 x S Eq. 5 j Cp x QT2 x w x t x p 2 A2 = k2 + 3456 (w+t) = BTU/in. Eq. 6 3456 x k2 (w+t) QS2 w x t x p + CpQT2 = BTU/# Eq. 7 where equations 4 and 6 are for the individual mold faces, equation 7 is for the mold overall heat removal and:
k2 = constant, determined as noted below Q = total heat removal Q2 = heat removed from cast strand skin sh = heat removed from superheat Cp = liquid specific heat = BTU/# per F. = 0.19 p = density, #/ft.3 S = speed, inches per min. (IPM) t = slab thickness or narrow face of mold, inches QT2 = superheat above liquid temperature, a TT-tL, F-TL = Liquidus temperature, F.
TT = Tundish temperature, F.
w = slab width or wide face of mold, inches.
: r I -10-'~'''' ~ ~ :
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Specifically for casting low carbon grade~
aluminum-killed steel in molds 10" thick (t) by 32-76" wide (w) at casting speeds from 30-60 IPM (S), the equations defining the calculated minimum level of mold heat removal rate take the form:
QL2 = 16.64 x S + 0.267 x S x AT2 wW+10 = BTU/min./in.
(Eq. 8) QA2 = 16.64 x 0.267 x AT2 wW+10 = BTU/in.2 Eq 9 QS2 = 11.83 wwl + O.l9~T2 = BTU/# Eq. 10 where constant k2 = 16.64 as determined from analyzing a large number of casts with a wide range of speeds, slag A1203 contents, tundish temperatures and slab widths.
Regardless of the number of coolant flow circuits used in mold 14, only one computer 20 having conventional analog computing elements is employed to determine QL2 calculated minimum level of mold heat removal rate based on either broad Eq. 4 or simplified Eq. 8. Computer 20 pro-; duces a QL2 output for recording and analy~ing purposes, and either one of QL2SG or QL2PG outputs for comparison purposesdepending upon the sheet grade SG or plate grade PG position of grade selector device 21.
In order to calculate QL2, QL2SG or QL2PG, computer 20 received the following operating data from caster 10:
(a) cast strand withdrawal speed S from pinch roll 16 drive tachometer ST~ (b) tundish temperature data from sensor TT;
; (c) liquidus temperature data TL from device 22 which, as ~ shown in FIG. 2, responds to ladle analysis data from sensor :
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¦ L~ and auto/m,anual mode control data from device 23? and (d) , ¦ ''L" dimension data from mold 14 sensors for single coolant i ¦ flow circuits, or "t" and "w" dimension data from mold 14 : ¦ sensors for multiple coolant flow circuits, both as described ¦ above for computer 19 when determining QLli.
¦ Computer 19 output(s) QLli and computer 20 outputs ¦ QL2SG, QL2PG are fed to comparator-controller 24 where QLi , ¦ data is compared to QL2SG or QL2PG data using conventional ,,; ¦ analog computer and control elements. Comparator-controller ' 10 ¦ 24 compares a preselected adjustable QL2SG or QL2PG as a ,, ¦ calculated preset signal against one QLli actual signal at ,,~ ¦ the input of a proportional indicating controller. Con-, ¦ troller output is ~QL which is factored and represents a ''"! ¦ speed error signal used in caster 10 speed corrective action.
15 ¦ When mold 14 has an adjustable rectangular structure, device ,~,, ¦ 24 is also provided with signal selectors to select the ,~,, ¦ lowest of QL1i actual signals for comparison with QL2SG or ,,~ ¦ QL2PG signal. Also device 24 provides different ~QL control ",~ ¦ action for mold wide faces than narrow faces. In addition, ,,,;, 20 ¦ device 24 includes monitoring circuits which signal alarm '~' ¦ device 25 with heat removal and speed error abortive alarms "" ¦ based on exceeding preset signal levels. ., ,",, ¦ When under automatic mode control established by ,~,,, ¦ device 23, comparator-controller 24 receives from caster ~ 25 ¦ speed preset 26 a preset speed input signal PSI simply for ",,~ ¦ caster speed monitoring and feed-through purposes. Caster ",~ ¦ speed preset 26 may be either a manual load or a computer ~," ¦ device which establishes in the PSI signal a desired with-~"~ ~ drawal rate~of cast strand 15 based on known criteria. This :'' I
~ ' ' 'i' '$' l ~ ' '',``:' I
~5~ Z2 signal is fed through device 24 and becomes preset speed output signal PSO which~ together with the ~QL speed error signal, is fed to pinch roll drive controller 27.
Pinch roll drive controller 27 operates in a conventional preset caster speed feedback loop to maintain the withdrawal rate of cast strand 15 at the preset speed established by the PSO signal. This is done algebraically summing the PSO signal at the SUM device which initially feeds a speed control signal to SC device, the latter powering drive motor M. Motor M drives pinch rolls 16, and therefore cast strand 15, at a speed sensed by speed tachometer ST. ST Scaler E/I scales and converts the ST signal into an actual speed signal S of proper units compatible with summer SUM as well as computer 20 which uses this signal as described above to calculate QL2. At SUM, the actual speed signal S
is combined wlth the preset speed signal PS0 and ultimately causes pinch roll drive controller 27 to maintain pinch rolls 16 and cast strand 15 at a constant withdrawal rate.
The ~QL speed error signal fed from comparator-controller 24 to SUM device in pinch roll drive controller 27 has the effect of modifying pinch roll 16 drive speed, and therefore cast strand 15 withdrawal rate. The amount of withdrawal speed correction action is predetermined by comparator-controller 24 and is different for narrow faces than wide faces of adjustable rectangular molds 14 as will be described below. Nevertheless, the withdrawal speed corrective action is defined as follows:
~QL qL~ QL2 -D, No speed ~q. 11 i~,"
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corrective action needed, or ~QL = QLli ~ QL2 < ? Take speed Eq. 12 ¦ corrective action.
¦ Conditions leading to ~QL speed corrective action during a caster 10 operation may occur as follows: First, ¦ ~QL>O and caster 10 is operating under a fixed set of ¦ conditions, no speed corrective action by controller 27 is required. Second, when a change occurs in caster 10 operation ¦ due to one or more of the following: (1) loss of metal level - 10 ¦ in mold 14, (2) slag deterioration such as increase in A1203 content; (3) loss of mold 14 narrow face taper in ¦ rectangular mold design, (4) caster 10 speed increase for ~ I any reason; and (5) increase in tundish 12 temperature as I ¦ sensed by TT sensor; any or all of which may cause ~QL<O, ~, 15 ¦ thus requiring speed corrective action by controller 27 in an amount determined by the magnitude of the ~QL speed error si~nal.
,, I Turning now to FIG. 2, a description will follow ¦ of liquidus temperature TL device 22 and of computer 20 ~! 20 ¦ which determines QL2, the calculated minimum level of mold ,; ¦ heat removal rate to prevent a breakout in cast strand 15.
, ¦ Generally, the analog instrumentation elements of computer ,~ ¦ 2~ operate on -O-lOVDC input to produce a -O-lOVDC output, except where otherwise noted. Scalers are provided where 25 ¦ necessary when another computer element is not equipped with ¦ this function.
~; ¦ FIG. 2 is exemplified with instrumentation elements ¦ to solve Eq. 8 in computer 20, the simplified equation for ¦ calcu~lating minimum level of mold 14 heat removal rate.
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Further, the example is limited to a slab thickness or mold narrow f'ace "tr' dimension of 10" ? thereby simplifying the number of computing elements required to solve Eq. 8. Other numerical values may require additional multipliers. In addition, the example is limited to a slab width or mold wire face "w ' dimension to a range of about 32" to about 76~', and casting speed to a range of about 30IPM to about ~-60IPM, whereupon encountering dimension and speed parameters outside of their respective ranges may require an adjustment 10 to the value of k2. It will now be apparent that computer ~` 20 may also be instrumented to solve broad Eq. 4, rather than simplified Eq. 8 as requirements may dictate.
Liquidus temperature signal tL for use by computer , 20 in solving either Eq. 4 or 8 is fed from one of two 15 sources in device 22, depending upon which source is selected by auto./manual mode control 23. One source is computer ~' liquidus 28 which provides a TL signal representing a liquidus temperature range of from 2730F to 2850F. This is based on ladle analysis provided by sensor LA, or other source not 20 shown. The second source is manual load device 29 which provides the same TL signal as computer liquidus source 28.
However, it is manually set by a caster operator based on tabular data characterized by data consisting of ladle analysis LA and sheet or plate grade 21SG, 21PG variables.
25 Under automatic mode of control, n.c. contacts 23Al select the computer liquidus source 28 to feed the TL signal computer 20, n.o. contacts 23Ml preventing the selection of manual osd souroe 29. I~n~er manual mode of control, ~' -15-~ ,, ' ' :~
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contacts 23Ml are closed and contacts 23Al open, thereby selecting manual load source 29 to provide the TL si~nal to computer 20 and preventing the selection of source 28.
The temperature differential signal required to solve Eq. 4 or Eq. 8 is developed by scaling the tundish t temperature signal TT in TT Scaler 30 in the range of 2730F-2850F, applying it to SUM device 31 where the liquidus temperature signal TL is subtracted from the tundish tem-perature signal TT. This causes SUM device 31 to generate - 10 a AT2 temperature differential signal having a range of 0-120F. Signal Limiting device 32 limits ~T2 to a range , ; of 0-120F. even though in practice there may develop a greater difference between the TT and TL signals.
In solving for the QA2 portion of Eq. 4 or Eq. 8 ~( 15 when strand thickness or mold narrow face dimension "t"-10", ;, the ~T2 signal from signal limiter 32 is fed to the "A"
A multiplying input of AQ2 multiplier/divider/biaser 33 such as f Foxboro #TI-2AP-130. Device 33 has multiplying inputs "A"
,, and "B", dividing input "C", biasing input "E", an output at 20 "D" and scaling and biasing features at all but the "E" input.
The ~T2 input at "A" is scaled internally according to constant k3 = t34x5Cp6xp = 0.267. The parameter "w" from the strand width of mold 14 wide face sensor is used in both ,~ numerator and denominator, therefore it is fed to inputs "B"
25 and "C", the "C" input being biased for "t" or 10". When "t"
is other than 10", scaling must be done proportionally. The k2 constant is added and scaled at the "E" input based on ~, the setting of k2 Bias device 34. The output at "D" of QA2 ,J
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multiplier 33 is now the calculated minimum level of mold 14 heat removal rate in terms of BTU/in2 of mold 14 surface area.
The QA2 output signal from device 33 is fed to the "B" input of QL2 multiplier 35 where it is multiplied by a 0-80IPM caster speed signal ~'S1' supplied to the "A" input.
The output at "D" of QL2 multiplier 35 is now in terms of calculated BT~/min./in. of mold 14 face length. This output is recorded and fed to comparator-controller 24 either as a QL2SG sheet grade signal through normally closed contact 21SG or as a QL2PG plate grade signal when contact 21PG is closed and the 21SG contact is opened by the grade selector 21.
Referring now to FIG. 3, a description of comparator-controller 24 will follow. In device 24, the same type of instrumentation elements as used in computer 20 are used to compare actual QLli-calculated QL2SG or QL2PG=AQL speed error signal. The arrangement shown in FIG. 3 is based on a four-circuit cooling system for a rectangular mold 14 having a separate computer 19 for each of the two wide faces and each of the two narrow faces, these being identified as producing mold 14 actual heat removal rates QLlW, QLlE, QLlN and QL1S, respectivcly. In practice, sheet grade and plate grade calculated QL2 may require different amounts of caster 10 speed corrective action. The same may be true for mold wide faces versus mold narrow faces as well as differences in character of control action required between the wide faces versus the narrow faces. For these reasons, ;~ co parato -oontroller 24 ls provided with separate circuit ~ -17-, ~:
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adjustments, signal selectors and controllers for comparing the lowest measured QLi signal from computer 19 and using it to compare with the preselected calculated QL2 signal to arrive at the ~QL speed error signal. Separate monitoring 5 and alarming in device 25 of mold 14 heat removal and caster 10 speed impending abortive conditions are also provided by device 24.
Comparator-controller 24 has provisions for functioning as follows. Assuming that the calculated sheet - 10 grade QL2SG signal and calculated plate grade QL2PG signal are alternately fed to the respective inputs of multipliers 36,37,38,39, respectively. Sheet grade heat transfer properties are about 5% better than plate grade properties ; and mold 14 wide face heat transfer properties are also about 5% better than mold 14 narrow face properties. For these reasons, the SG,PG inputs of multiplier 36 are preset at about ~5%,0% respectively, thereby causing multiplier 36 , to output a wide face QL2 set point signal. Similarly, the SG,PG inputs of multiplier 37 are preset at about 0%-5%
respectively, thereby causing multiplier 37 to output a narrow face QL2 set point signal.
The wide face QL2 set point signal is fed to a ~s~ corresponding input of proportional indicating controller i 40. Here it is compared to the lowest QLl measured signal from either of the QLlW or QLlE wide face source in computer 19 as determined by low signal selector 41. This device is a Foxboro #TI-2AP-16Q Hi/Lo signal selecting device set to pass the lowest signal when less than zero. The lowest wide ,~''', j~ ~18-:'' ''~, ''' .' ~L~5Z~2Z
face QLlW or QLlE signal indicates which of the wide faces of mold 14 is producing the smaller amount of mold 14 heat removal, thereby requiring caster 10 speed corrective action to prevent a breakout in cast strand 15, regardless of whether strand 15 is a sheet grade or plate grade product.
The control action of P.I. controller 40 is characterized for mold 14 wide face control action.
The narrow face QL2 set point signal is fed to a corresponding input of proportional indicating controller 42.
Here it is compared to the lowest QLl measured signal from either of the QLlN or QLlS narrow face source in computer 19 as determined by low face signal selector 43, a device the same as device 41. Similarly, the lowest narrow face QLlN, QL1S indicates which of the narrow faces of mold 14 is pro-ducing the smaller amount of mold 14 heat removal and thus requiring caster 10 speed corrective action. The control action of device 42 is characterized for mold 14 narrow face control action.
Control output signal from both proportional indicating controllers 40,42 represent mold 14 heat removal ~; rate error between their respective selected wide face or narrow face, as well as the different character of respec-" tive control action when their lowest selected BT~/min./in.
source was less than zero. The two proportional control ~' 25 output signals ~rom controllers 40,42 having different control action are fed to low signal selector 44, a device the same as devices 41,43. Device 44 selects the lowest of ~ the two w de face or narrow ~ace control error s~gnals when ';` -19-, :,' ,, ; - . , . ~ . .. .
~- ' - ' , : ' . ~ , .
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less than zero and feeds them as QQL sp~eed error signal to multiplier 45. The QQL speed error signal has the proper ; preselected control action for the source of heat removal rate error in mold 14, regardless of whether a sheet grade or plate grade casting was preselected by grade selector 21.
Multiplier 45 is adjusted to provide the desired percentage of QQL control action effective by way of voltage to current converter 46 on pinch roll drive controller 27 in FIG. 1.
The QQL speed error signal is effective only when auto./manual mode control 23 in automatic mode and contacts 23A2 are closed. When device 23 is in manual mode contacts , 23A2 open and prevent the QQL speed error signal from being fed ko pinch roll drive controller 27.
Monitoring functions of mold 14 heat removal rate errors and caster speed error parameters are carried out simultaneously with the development of set points noted above. Monitoring functions are set to be activated at a level of about 10% before abort conditions will arise. For these reasons, the SG,PG inputs of wide face alarm adjust 20 multiplier 38 are preset at about -5%,-10% respectively.
This causes multiplier 38 to output a proportioned QL2SG or QL2PG signal to differential alarm relay 47 where it is compared to the lowest wide face QLlW or QL1E signal deter-~;~ mined by low signal selector 41. When the difference in signals is within the preset 10% of approaching control saturation, relay 47 sends a mold 14 wide face abort alarm signal over lead 48 to W.F.Abort device in alarm device 25.
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~ -20-'' , ,,, ~, . ,., 115~:7Z2 The S~,PG inputs of narrow face alarm adjust multiplier 39 are preset at about -10%,-15%, respectively.
This causes multiplier 39 to output a proportional QL2SG
or QL2PG signal to differential alarm relay 49 where it is 5 compared to the lowest narrow face QLlN or QLlS signal determined by low signal selector 43. When the difference in signals is within the preset 10% of approaching control saturation, reIay 49 sends a mold 14 narrow face abort alarm signal over lead 50 to N.F.Abort device in alarm device 25.
: 10 During automatic mode control when contacts 23M2 are open as established by device 23, the caster speed preset input PSI signal fed from preset 26 is passed through : voltage-to-voltage converter 51 to differential alarm relay 52. Here it is compared to the ~QL speed error signal output 15 from multiplier 45. A predetermined difference between the two signals indicating approach of control saturation causes relay 52 to send a speed abort alarm signal over lead 53 to , Speed Abort device in alarm device 25.
The caster preset speed PSI signal is fed into 20 comparator-controller 24 as a voltage variable signal for the purpose of comparing it with the ~QL signal and deter-mining the speed abort condition referred to above. This . slgnal is fed out of device 24 through voltage-to-current converter 54 back to SUM device in controller 27 as the ,~I 25 caster preset speed output signal PS0 mentioned above.
;l It will now be apparent that the analog computing ,"l functions of computers 19,20, liquidus temperature TL source 22, and c arator-controller 24 may be per~ormed by di~ital :''' ' '~ -';'':, . . - - , :
.~ ~ - .-1~527~Z
computer apparatus, either in individual components or in a single minicomputer.
In FIGS. 1-3 both manual and automatic modes of control are established by control device 23, caster 10 operation is such that actual mold heat removal rate QLli in mold 14 as determined by measurement and calculation methods in computer 19 is compared to calculated minimum mold heat removal rate QL2SG or QL2PG as determined by calculation methods in computer 20, thereby preventing breakouts in cast strand 15 below mold 14 due to insufficient strand skin thickness. The various control modes differ in ways in which the comparison takes place in comparator-controller 24 and is used to control the strand 15 casting speed S.
First, under manual mode of control, the operator compares the measured mold heat removal rate QLli by computer 19 to the minimum mold level QL2SG or QL2PG published in ; tables or charts covering one or more of the following operating parameters: tundish temperature, steel grade~
casting speed, strand width or wide face mold dimension and the like. If actual mold heat removal rate QLli falls below the minimum rate level QL2SG or QL2PG, then the operator of caster 10 manually reduces caster preset speed PSI at device 26. If the actual mold heat removal rate is significantly above the calcùlated minimum rate level, the caster 10 operator has the option to increase casting speed S. QLli, QL2 and ~QL records are available for guiding caster 10 operator in ad;usting caster speed S.
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Second, under automatic mode control, the com-: parison of actual mold heat removal rate QL1i determined in computer 19 is automatically compared with calculated : minimum level QL2S~ or QL2PG determined in computer 20.
This comparison takes place in comparator--controller 24 which generates the ~QL speed error signal. QQL speed error signal automatically biases or modifies the pinch roll 15 drive controller 27 to vary casting speed S only in the event that the actual mold heat removal rate reaches the :
10 minimum mold level. When the actual mold heat removal rate exceeds the minimum level, ~QL is zero and the casting speed ~:
S remains unchanged at the preset value of PSO. When ~QL is 7 less than zero, the speed error signal automatically varies . casting speed S to maintain actual heat removal rate at the minimum rate level, or some fixed increment above the minimum rate level, or even within a range which may be defined as a function of caster speed or other variables.
~, Third, caster 10 installations embodying automatic biasing or modifying of the speed control system, such as in ; 20 pinch roll drive controller 27, device 23 provides means for returning to manual operating mode whereby caster 10 speed . control is transferable back to the operator who adjusts , ~ caster pr et speed control device 26 .
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~ A1203 content of the mold slag during casting of aluminum--¦ killed steel which causes mold slag to become viscous and gummy and results in a significant loss in mold heat transfer.
¦ Third, in a rectangular mold, loss of narrow face taper ¦ increasing a strand-mold gap which reduces heat transfer on one or both narrow faces. Fourth, too high a casting speed which reduces residence time of a thin walled shell in the mold, thereby causing insufficient amounts of heat removal.
l Fifth, excessive temperature of liquid metal entering the 10 ¦ mold which increases the mold heat load. Sixth, casting of wider and thicker slabs which reduce the surface area per volume of metal cast, thus causing more mold surface area to be used to extract the metal superheat and reducing the area l available for formation of solid skin.
15 l Caster operators are taught that a thicker skin l may be formed in a caster mold to prevent breakout by ¦ manually reducing caster speed. This is based on known mold heat removal rate QA per square inch of strand surface l which is speed dependent. However, there is lacking a prior 20 ¦ art relationship defin ng when mold heat removal rate is insufficient, or in what manner caster speed corrective action should be taken. J. Shipman et al in U.S. Patent No.
4,006,633 disclose how to satisfactorily measure and determine l mold heat removal rate in single and multiple mold coolant 25 l flow circuits, but lacks direction as to determining minimurn level of mold heat removal rate as well as caster speed correction. Earlier prior art is similarly deficient, or if mold heat remova] is suggested, it requires a comprehensive ~$27Z2 ¦ analysis and determination of strand thermal and stress pro-¦ files all along the strand beyond the mold which must be ¦ combined wîth mold parameters.
Summary of the Invention 5 ¦ One of the objects of this invention is to provide an improved method and apparatus for continuously controlling caster mold heat removal rate which will overcome the fore-going difficulties.
l Another object of this invention is to provide a 10 ¦ method and apparatus for determining caster minimum level of mold heat removal rate and caster corrective action to be taken in the control of mold heat removal.
Still another object of this invention is to provide an improved method and apparatus for controlling caster mold heat removal without considering such parameters as mold level3 cast strand thermal or stress profiles.
The foregoing objects are attainable in casters with fixed or adjustable mold structures having cooling means for solidifying strand casting, either single or multiple coolant flow circuits, and variable drive means with a presetable feedback loop for controllably withdrawing the strand as cast. The apparatus comprises:
(a) first plural means for determining actual heat removal rate of the cooling means during strand casting;
(b) second plural means for determining a calculated , minimum level of heat removal rate re~uired of the cool g mean s to prevent strand breakout during casting;
., ~l~5~ Z2 (c) third means for comparing outputs from only means (a) with means (b) and as a result generating a speed error signal based on a predetermined difference between the actual and calculated heat removal rates; and (d) said third means including control means for modifying the preset speed of the caster drive means as a function of only the speed error signal so that the actual heat removal rate will exceed the calculated minimum level ¦ thereof.
10 ¦ The method, as practiced on such apparatus, includes ¦ the steps of:
¦ (a) determining actual heat removal rate of the cooling ¦ means during strand casting;
¦ (b) determining a calculated minimum level of heat removal rate according to either:
I C x ~T2 x w x t x p l QL2 k2 + ~ 6 (w+t) S = BTU/min./in.
¦ or C x ~T2 x w x t x p 2 l 2 3r-6 (w+t) - = BTU/in.
¦ where:
20 ¦ k2 = predetermined constant l Cp = liquid specific heat = BTU/# per F. = 0.19 ¦ P = density, ~//ft.3 S = speed, inches per min. (IPM) t = slab thickness or narrow face of mold, inches ~T2 = superheat above liquid temperature, = TT--TL, F
TL = Liquidus temperature, F.
TT = Tundish temperature, F.
w = slab width or wide face of mold, inches, ~5~ 2 ¦ as required o:f the cooling means to prevent strand ¦ breakout during casting;
¦(c) comparing outputs from only step (a) with step (b) l and as a result generating a speed error signal ¦ according to either:
l ~QL = QLli - QL2 ~, ~ speed corrective action needed, ¦ or l ~QL = QLli - QL2 ~, Take speed corrective action, ¦ based on a predetermined difference between the ¦ actual and calculated heat removal rates; and ¦(d) modifying the preset speed of the caster drive means ¦ as a function of only the speed error signal so that the actual heat removal rate will exceed the calculated minimum level thereof.
Brief Description of the Drawings FIG. 1 is a block diagram of a continuous metal caster having a fixed size mold with variable cooling, metal feed, computing and speed control systems in which there is incorporated the present invention.
FIG. 2 is an instrumentation diagram of a computer used to calculate the minimum level of mold heat removal rate useful with either single or multiple faced mold designs in the FIG. 1 embodiment.
FIG. 3 is an instrumentation diagram of the comparator-controller used to automatically select the wide or narrow mold face of an adjustable rectangular mold with the lowest actual mold heat removal rate for use with the FIG. 1 embodiment.
~ ~L15~1Z2 Description of the Preferred ~mbodiment Referring to FIG. 1, continuous metal caster 10, or simply caster 10, will be presumed to have undergone start-up procedures and is operating in essentially a steady-state mode. Superheated molten metal was teemed from ladle 11 into tundish 12 and then fed controllably as hot metal stream 13 into caster mold 14. Mold 14 heat transfer, which is regulated a predetermined amount by coolant flow control valve WCV, effects solidification so that as cast strand 15 leaves mold 14 it continually consists of a liquid core and outer shell or skin of sufficient thickness to prevent a breakout.
Mold 14 instantaneous heat removal requirements vary as a function of mold hot metal level, mold size, other parameters described below, and cast strand 15 withdrawal rate as determined by pinch roll 16 operating in a preset æpeed control loop also described below. In order to accommodate a fluctuating mold heat transfer in the single coolant flow circuit shown in FIG. 1, flow control valve WCV
is interposed between coolant supply 17, mold 14 and coolant return 18 and operates in response to a flow control signal from computer 19. In the case of mold 14 being an adjustable rectangular structure with four independent coolant flow circuits, each circuit has a flow control valve WCVi inter-posed between coolant supply 17 and coolant return 18.
, Computer 19 instrumentation is exemplified by an assembly of conventional analog-type computer and control elements such as are found in a Foxboro Spec. 200 analog computer.
,~
~as~2 easurlng rneans and computer means for determ~n~ng ¦and controlling actual mold 14 heat removal corresponding ¦to computer 19 is disclosed in the Shipman et al Patent No.
~ ¦4,oo6,633. This patent is directed to both single and '~` 5 ¦multiple coolant flow circuits having a separate instrument ¦measuring and controlling computer for each flow circuit.
¦Instead of each computer and measuring device having an ¦"i"th subscript, they carry N,S,E,W, designations corre-¦spondlng to either wide or narrow mold faces as is done ¦hereinbelow.
¦ Regardless of the number of coolant flow circuits ~' ¦used in mold 14, each computer 19 per~orms two functions.
. ¦The first function of computer 19 is to generate a conven-¦tional coolant flow control signal WCVi for its associated '~ 15 ¦flow control valve WCV in response to a coolant flow signal :ii from a respective flow transmitter WT and a preset flow signal (not shown herein). The second function of computer 19 is to use Eq. 1, for example, to produce an actual heat removal Qi signal for comparison and recording purposes in response to signals representing coolant flow rate WTi, ,~ coolant temperature in and out TIi,TOi with respect to mold , 14, all being fed to computer 19.
~'i, Actual heat removal rate may be expressed as , either QL or QA for use with the present invention. QL is ,~ 25 preferred herein because it references heat removal to mold face peripheral length "L', or width "w" and/or "t" thickness ln terms of BTU/min./in. of mold face length which is not dependent upon a speed parameter. ~Ihereas, QA if used ! ~
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, . . .
~LlSZ7~2 references heat removal to strand face sur~ace area in terms of BTU/in. and is speed dependent. In practice, each computer 19 determines what is designated hereinafter as QL
actual heat removal rate per unit length of mold face as 5follows:
W x ~T x k x C
QLl 1 L 1 _ P _ BTU/min./in. Eq. 1 where:
W = coolant flow rate in GPM
~Tl = TO-TI = coolant temperature rise, F.
kl = constant = 8.33 lbs. per gal.
Cp = specific heat BTU/lb. per F. = 0.19 L = dimension of mold face in inches, and Al = QLl S Eq. 2 where:
S = speed of cast strand leaving mold, inches/min.
Mold 14 face length "L" dimensions shown in FIG. 1 are also fed to computer 19 in addition to coolant flow and thermal parameters. When mold 14 has a single face ,20 and single coolant flow circuit, the "L" dimension corre-sponds to mold face peripheral length data which is fed as a single input "L" (not shown) from a mold length data source to computer 19. Alternatively, when mold 14 is an ad~ustable rectangle having four faces each with an inde-pendent coolant flow circuit, the "L" dimension consists of mold wide face "w" and mold thickness or narrow face ~It~
dimensional data which are fed from respective mold data sources to corresponding inputs to separate computers 19.
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¦ Still referring to FIG. 1, computer 20 determines ; ¦ whàt is designated hereinafter as QL2 calculated minimum ~ ¦ mold heat removal rate per unit length of mold peripheral i ¦ face so as to be on the same basis as QLl. It has been ¦ discovered that the minimum level of mold heat removal rate necessary to prevent a breakout during caster 10 operation may be defined by the following equations:
Q Qs + Qsh Eq. 3 C x QT2 x w x t x p QL2 k2 + 3456 (w+t)S = BTU/min./in. Eq. 4 10 QL2 = QA2 x S Eq. 5 j Cp x QT2 x w x t x p 2 A2 = k2 + 3456 (w+t) = BTU/in. Eq. 6 3456 x k2 (w+t) QS2 w x t x p + CpQT2 = BTU/# Eq. 7 where equations 4 and 6 are for the individual mold faces, equation 7 is for the mold overall heat removal and:
k2 = constant, determined as noted below Q = total heat removal Q2 = heat removed from cast strand skin sh = heat removed from superheat Cp = liquid specific heat = BTU/# per F. = 0.19 p = density, #/ft.3 S = speed, inches per min. (IPM) t = slab thickness or narrow face of mold, inches QT2 = superheat above liquid temperature, a TT-tL, F-TL = Liquidus temperature, F.
TT = Tundish temperature, F.
w = slab width or wide face of mold, inches.
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Specifically for casting low carbon grade~
aluminum-killed steel in molds 10" thick (t) by 32-76" wide (w) at casting speeds from 30-60 IPM (S), the equations defining the calculated minimum level of mold heat removal rate take the form:
QL2 = 16.64 x S + 0.267 x S x AT2 wW+10 = BTU/min./in.
(Eq. 8) QA2 = 16.64 x 0.267 x AT2 wW+10 = BTU/in.2 Eq 9 QS2 = 11.83 wwl + O.l9~T2 = BTU/# Eq. 10 where constant k2 = 16.64 as determined from analyzing a large number of casts with a wide range of speeds, slag A1203 contents, tundish temperatures and slab widths.
Regardless of the number of coolant flow circuits used in mold 14, only one computer 20 having conventional analog computing elements is employed to determine QL2 calculated minimum level of mold heat removal rate based on either broad Eq. 4 or simplified Eq. 8. Computer 20 pro-; duces a QL2 output for recording and analy~ing purposes, and either one of QL2SG or QL2PG outputs for comparison purposesdepending upon the sheet grade SG or plate grade PG position of grade selector device 21.
In order to calculate QL2, QL2SG or QL2PG, computer 20 received the following operating data from caster 10:
(a) cast strand withdrawal speed S from pinch roll 16 drive tachometer ST~ (b) tundish temperature data from sensor TT;
; (c) liquidus temperature data TL from device 22 which, as ~ shown in FIG. 2, responds to ladle analysis data from sensor :
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115Z7Z~
¦ L~ and auto/m,anual mode control data from device 23? and (d) , ¦ ''L" dimension data from mold 14 sensors for single coolant i ¦ flow circuits, or "t" and "w" dimension data from mold 14 : ¦ sensors for multiple coolant flow circuits, both as described ¦ above for computer 19 when determining QLli.
¦ Computer 19 output(s) QLli and computer 20 outputs ¦ QL2SG, QL2PG are fed to comparator-controller 24 where QLi , ¦ data is compared to QL2SG or QL2PG data using conventional ,,; ¦ analog computer and control elements. Comparator-controller ' 10 ¦ 24 compares a preselected adjustable QL2SG or QL2PG as a ,, ¦ calculated preset signal against one QLli actual signal at ,,~ ¦ the input of a proportional indicating controller. Con-, ¦ troller output is ~QL which is factored and represents a ''"! ¦ speed error signal used in caster 10 speed corrective action.
15 ¦ When mold 14 has an adjustable rectangular structure, device ,~,, ¦ 24 is also provided with signal selectors to select the ,~,, ¦ lowest of QL1i actual signals for comparison with QL2SG or ,,~ ¦ QL2PG signal. Also device 24 provides different ~QL control ",~ ¦ action for mold wide faces than narrow faces. In addition, ,,,;, 20 ¦ device 24 includes monitoring circuits which signal alarm '~' ¦ device 25 with heat removal and speed error abortive alarms "" ¦ based on exceeding preset signal levels. ., ,",, ¦ When under automatic mode control established by ,~,,, ¦ device 23, comparator-controller 24 receives from caster ~ 25 ¦ speed preset 26 a preset speed input signal PSI simply for ",,~ ¦ caster speed monitoring and feed-through purposes. Caster ",~ ¦ speed preset 26 may be either a manual load or a computer ~," ¦ device which establishes in the PSI signal a desired with-~"~ ~ drawal rate~of cast strand 15 based on known criteria. This :'' I
~ ' ' 'i' '$' l ~ ' '',``:' I
~5~ Z2 signal is fed through device 24 and becomes preset speed output signal PSO which~ together with the ~QL speed error signal, is fed to pinch roll drive controller 27.
Pinch roll drive controller 27 operates in a conventional preset caster speed feedback loop to maintain the withdrawal rate of cast strand 15 at the preset speed established by the PSO signal. This is done algebraically summing the PSO signal at the SUM device which initially feeds a speed control signal to SC device, the latter powering drive motor M. Motor M drives pinch rolls 16, and therefore cast strand 15, at a speed sensed by speed tachometer ST. ST Scaler E/I scales and converts the ST signal into an actual speed signal S of proper units compatible with summer SUM as well as computer 20 which uses this signal as described above to calculate QL2. At SUM, the actual speed signal S
is combined wlth the preset speed signal PS0 and ultimately causes pinch roll drive controller 27 to maintain pinch rolls 16 and cast strand 15 at a constant withdrawal rate.
The ~QL speed error signal fed from comparator-controller 24 to SUM device in pinch roll drive controller 27 has the effect of modifying pinch roll 16 drive speed, and therefore cast strand 15 withdrawal rate. The amount of withdrawal speed correction action is predetermined by comparator-controller 24 and is different for narrow faces than wide faces of adjustable rectangular molds 14 as will be described below. Nevertheless, the withdrawal speed corrective action is defined as follows:
~QL qL~ QL2 -D, No speed ~q. 11 i~,"
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corrective action needed, or ~QL = QLli ~ QL2 < ? Take speed Eq. 12 ¦ corrective action.
¦ Conditions leading to ~QL speed corrective action during a caster 10 operation may occur as follows: First, ¦ ~QL>O and caster 10 is operating under a fixed set of ¦ conditions, no speed corrective action by controller 27 is required. Second, when a change occurs in caster 10 operation ¦ due to one or more of the following: (1) loss of metal level - 10 ¦ in mold 14, (2) slag deterioration such as increase in A1203 content; (3) loss of mold 14 narrow face taper in ¦ rectangular mold design, (4) caster 10 speed increase for ~ I any reason; and (5) increase in tundish 12 temperature as I ¦ sensed by TT sensor; any or all of which may cause ~QL<O, ~, 15 ¦ thus requiring speed corrective action by controller 27 in an amount determined by the magnitude of the ~QL speed error si~nal.
,, I Turning now to FIG. 2, a description will follow ¦ of liquidus temperature TL device 22 and of computer 20 ~! 20 ¦ which determines QL2, the calculated minimum level of mold ,; ¦ heat removal rate to prevent a breakout in cast strand 15.
, ¦ Generally, the analog instrumentation elements of computer ,~ ¦ 2~ operate on -O-lOVDC input to produce a -O-lOVDC output, except where otherwise noted. Scalers are provided where 25 ¦ necessary when another computer element is not equipped with ¦ this function.
~; ¦ FIG. 2 is exemplified with instrumentation elements ¦ to solve Eq. 8 in computer 20, the simplified equation for ¦ calcu~lating minimum level of mold 14 heat removal rate.
r l I ., , 11527~Z
Further, the example is limited to a slab thickness or mold narrow f'ace "tr' dimension of 10" ? thereby simplifying the number of computing elements required to solve Eq. 8. Other numerical values may require additional multipliers. In addition, the example is limited to a slab width or mold wire face "w ' dimension to a range of about 32" to about 76~', and casting speed to a range of about 30IPM to about ~-60IPM, whereupon encountering dimension and speed parameters outside of their respective ranges may require an adjustment 10 to the value of k2. It will now be apparent that computer ~` 20 may also be instrumented to solve broad Eq. 4, rather than simplified Eq. 8 as requirements may dictate.
Liquidus temperature signal tL for use by computer , 20 in solving either Eq. 4 or 8 is fed from one of two 15 sources in device 22, depending upon which source is selected by auto./manual mode control 23. One source is computer ~' liquidus 28 which provides a TL signal representing a liquidus temperature range of from 2730F to 2850F. This is based on ladle analysis provided by sensor LA, or other source not 20 shown. The second source is manual load device 29 which provides the same TL signal as computer liquidus source 28.
However, it is manually set by a caster operator based on tabular data characterized by data consisting of ladle analysis LA and sheet or plate grade 21SG, 21PG variables.
25 Under automatic mode of control, n.c. contacts 23Al select the computer liquidus source 28 to feed the TL signal computer 20, n.o. contacts 23Ml preventing the selection of manual osd souroe 29. I~n~er manual mode of control, ~' -15-~ ,, ' ' :~
115;:7ZZ
contacts 23Ml are closed and contacts 23Al open, thereby selecting manual load source 29 to provide the TL si~nal to computer 20 and preventing the selection of source 28.
The temperature differential signal required to solve Eq. 4 or Eq. 8 is developed by scaling the tundish t temperature signal TT in TT Scaler 30 in the range of 2730F-2850F, applying it to SUM device 31 where the liquidus temperature signal TL is subtracted from the tundish tem-perature signal TT. This causes SUM device 31 to generate - 10 a AT2 temperature differential signal having a range of 0-120F. Signal Limiting device 32 limits ~T2 to a range , ; of 0-120F. even though in practice there may develop a greater difference between the TT and TL signals.
In solving for the QA2 portion of Eq. 4 or Eq. 8 ~( 15 when strand thickness or mold narrow face dimension "t"-10", ;, the ~T2 signal from signal limiter 32 is fed to the "A"
A multiplying input of AQ2 multiplier/divider/biaser 33 such as f Foxboro #TI-2AP-130. Device 33 has multiplying inputs "A"
,, and "B", dividing input "C", biasing input "E", an output at 20 "D" and scaling and biasing features at all but the "E" input.
The ~T2 input at "A" is scaled internally according to constant k3 = t34x5Cp6xp = 0.267. The parameter "w" from the strand width of mold 14 wide face sensor is used in both ,~ numerator and denominator, therefore it is fed to inputs "B"
25 and "C", the "C" input being biased for "t" or 10". When "t"
is other than 10", scaling must be done proportionally. The k2 constant is added and scaled at the "E" input based on ~, the setting of k2 Bias device 34. The output at "D" of QA2 ,J
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multiplier 33 is now the calculated minimum level of mold 14 heat removal rate in terms of BTU/in2 of mold 14 surface area.
The QA2 output signal from device 33 is fed to the "B" input of QL2 multiplier 35 where it is multiplied by a 0-80IPM caster speed signal ~'S1' supplied to the "A" input.
The output at "D" of QL2 multiplier 35 is now in terms of calculated BT~/min./in. of mold 14 face length. This output is recorded and fed to comparator-controller 24 either as a QL2SG sheet grade signal through normally closed contact 21SG or as a QL2PG plate grade signal when contact 21PG is closed and the 21SG contact is opened by the grade selector 21.
Referring now to FIG. 3, a description of comparator-controller 24 will follow. In device 24, the same type of instrumentation elements as used in computer 20 are used to compare actual QLli-calculated QL2SG or QL2PG=AQL speed error signal. The arrangement shown in FIG. 3 is based on a four-circuit cooling system for a rectangular mold 14 having a separate computer 19 for each of the two wide faces and each of the two narrow faces, these being identified as producing mold 14 actual heat removal rates QLlW, QLlE, QLlN and QL1S, respectivcly. In practice, sheet grade and plate grade calculated QL2 may require different amounts of caster 10 speed corrective action. The same may be true for mold wide faces versus mold narrow faces as well as differences in character of control action required between the wide faces versus the narrow faces. For these reasons, ;~ co parato -oontroller 24 ls provided with separate circuit ~ -17-, ~:
1~527ZZ
adjustments, signal selectors and controllers for comparing the lowest measured QLi signal from computer 19 and using it to compare with the preselected calculated QL2 signal to arrive at the ~QL speed error signal. Separate monitoring 5 and alarming in device 25 of mold 14 heat removal and caster 10 speed impending abortive conditions are also provided by device 24.
Comparator-controller 24 has provisions for functioning as follows. Assuming that the calculated sheet - 10 grade QL2SG signal and calculated plate grade QL2PG signal are alternately fed to the respective inputs of multipliers 36,37,38,39, respectively. Sheet grade heat transfer properties are about 5% better than plate grade properties ; and mold 14 wide face heat transfer properties are also about 5% better than mold 14 narrow face properties. For these reasons, the SG,PG inputs of multiplier 36 are preset at about ~5%,0% respectively, thereby causing multiplier 36 , to output a wide face QL2 set point signal. Similarly, the SG,PG inputs of multiplier 37 are preset at about 0%-5%
respectively, thereby causing multiplier 37 to output a narrow face QL2 set point signal.
The wide face QL2 set point signal is fed to a ~s~ corresponding input of proportional indicating controller i 40. Here it is compared to the lowest QLl measured signal from either of the QLlW or QLlE wide face source in computer 19 as determined by low signal selector 41. This device is a Foxboro #TI-2AP-16Q Hi/Lo signal selecting device set to pass the lowest signal when less than zero. The lowest wide ,~''', j~ ~18-:'' ''~, ''' .' ~L~5Z~2Z
face QLlW or QLlE signal indicates which of the wide faces of mold 14 is producing the smaller amount of mold 14 heat removal, thereby requiring caster 10 speed corrective action to prevent a breakout in cast strand 15, regardless of whether strand 15 is a sheet grade or plate grade product.
The control action of P.I. controller 40 is characterized for mold 14 wide face control action.
The narrow face QL2 set point signal is fed to a corresponding input of proportional indicating controller 42.
Here it is compared to the lowest QLl measured signal from either of the QLlN or QLlS narrow face source in computer 19 as determined by low face signal selector 43, a device the same as device 41. Similarly, the lowest narrow face QLlN, QL1S indicates which of the narrow faces of mold 14 is pro-ducing the smaller amount of mold 14 heat removal and thus requiring caster 10 speed corrective action. The control action of device 42 is characterized for mold 14 narrow face control action.
Control output signal from both proportional indicating controllers 40,42 represent mold 14 heat removal ~; rate error between their respective selected wide face or narrow face, as well as the different character of respec-" tive control action when their lowest selected BT~/min./in.
source was less than zero. The two proportional control ~' 25 output signals ~rom controllers 40,42 having different control action are fed to low signal selector 44, a device the same as devices 41,43. Device 44 selects the lowest of ~ the two w de face or narrow ~ace control error s~gnals when ';` -19-, :,' ,, ; - . , . ~ . .. .
~- ' - ' , : ' . ~ , .
~L15Z7ZZ
less than zero and feeds them as QQL sp~eed error signal to multiplier 45. The QQL speed error signal has the proper ; preselected control action for the source of heat removal rate error in mold 14, regardless of whether a sheet grade or plate grade casting was preselected by grade selector 21.
Multiplier 45 is adjusted to provide the desired percentage of QQL control action effective by way of voltage to current converter 46 on pinch roll drive controller 27 in FIG. 1.
The QQL speed error signal is effective only when auto./manual mode control 23 in automatic mode and contacts 23A2 are closed. When device 23 is in manual mode contacts , 23A2 open and prevent the QQL speed error signal from being fed ko pinch roll drive controller 27.
Monitoring functions of mold 14 heat removal rate errors and caster speed error parameters are carried out simultaneously with the development of set points noted above. Monitoring functions are set to be activated at a level of about 10% before abort conditions will arise. For these reasons, the SG,PG inputs of wide face alarm adjust 20 multiplier 38 are preset at about -5%,-10% respectively.
This causes multiplier 38 to output a proportioned QL2SG or QL2PG signal to differential alarm relay 47 where it is compared to the lowest wide face QLlW or QL1E signal deter-~;~ mined by low signal selector 41. When the difference in signals is within the preset 10% of approaching control saturation, relay 47 sends a mold 14 wide face abort alarm signal over lead 48 to W.F.Abort device in alarm device 25.
,~.',, :-~.
~ -20-'' , ,,, ~, . ,., 115~:7Z2 The S~,PG inputs of narrow face alarm adjust multiplier 39 are preset at about -10%,-15%, respectively.
This causes multiplier 39 to output a proportional QL2SG
or QL2PG signal to differential alarm relay 49 where it is 5 compared to the lowest narrow face QLlN or QLlS signal determined by low signal selector 43. When the difference in signals is within the preset 10% of approaching control saturation, reIay 49 sends a mold 14 narrow face abort alarm signal over lead 50 to N.F.Abort device in alarm device 25.
: 10 During automatic mode control when contacts 23M2 are open as established by device 23, the caster speed preset input PSI signal fed from preset 26 is passed through : voltage-to-voltage converter 51 to differential alarm relay 52. Here it is compared to the ~QL speed error signal output 15 from multiplier 45. A predetermined difference between the two signals indicating approach of control saturation causes relay 52 to send a speed abort alarm signal over lead 53 to , Speed Abort device in alarm device 25.
The caster preset speed PSI signal is fed into 20 comparator-controller 24 as a voltage variable signal for the purpose of comparing it with the ~QL signal and deter-mining the speed abort condition referred to above. This . slgnal is fed out of device 24 through voltage-to-current converter 54 back to SUM device in controller 27 as the ,~I 25 caster preset speed output signal PS0 mentioned above.
;l It will now be apparent that the analog computing ,"l functions of computers 19,20, liquidus temperature TL source 22, and c arator-controller 24 may be per~ormed by di~ital :''' ' '~ -';'':, . . - - , :
.~ ~ - .-1~527~Z
computer apparatus, either in individual components or in a single minicomputer.
In FIGS. 1-3 both manual and automatic modes of control are established by control device 23, caster 10 operation is such that actual mold heat removal rate QLli in mold 14 as determined by measurement and calculation methods in computer 19 is compared to calculated minimum mold heat removal rate QL2SG or QL2PG as determined by calculation methods in computer 20, thereby preventing breakouts in cast strand 15 below mold 14 due to insufficient strand skin thickness. The various control modes differ in ways in which the comparison takes place in comparator-controller 24 and is used to control the strand 15 casting speed S.
First, under manual mode of control, the operator compares the measured mold heat removal rate QLli by computer 19 to the minimum mold level QL2SG or QL2PG published in ; tables or charts covering one or more of the following operating parameters: tundish temperature, steel grade~
casting speed, strand width or wide face mold dimension and the like. If actual mold heat removal rate QLli falls below the minimum rate level QL2SG or QL2PG, then the operator of caster 10 manually reduces caster preset speed PSI at device 26. If the actual mold heat removal rate is significantly above the calcùlated minimum rate level, the caster 10 operator has the option to increase casting speed S. QLli, QL2 and ~QL records are available for guiding caster 10 operator in ad;usting caster speed S.
::
', C
' , ~:~5?,~Z~ ~
Second, under automatic mode control, the com-: parison of actual mold heat removal rate QL1i determined in computer 19 is automatically compared with calculated : minimum level QL2S~ or QL2PG determined in computer 20.
This comparison takes place in comparator--controller 24 which generates the ~QL speed error signal. QQL speed error signal automatically biases or modifies the pinch roll 15 drive controller 27 to vary casting speed S only in the event that the actual mold heat removal rate reaches the :
10 minimum mold level. When the actual mold heat removal rate exceeds the minimum level, ~QL is zero and the casting speed ~:
S remains unchanged at the preset value of PSO. When ~QL is 7 less than zero, the speed error signal automatically varies . casting speed S to maintain actual heat removal rate at the minimum rate level, or some fixed increment above the minimum rate level, or even within a range which may be defined as a function of caster speed or other variables.
~, Third, caster 10 installations embodying automatic biasing or modifying of the speed control system, such as in ; 20 pinch roll drive controller 27, device 23 provides means for returning to manual operating mode whereby caster 10 speed . control is transferable back to the operator who adjusts , ~ caster pr et speed control device 26 .
"
''' -::,-x, ` -23-'' ' ~s.
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"' ... . . . .
, . .
Claims (24)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of controlling heat removal from a continuous metal caster having cooling means for solidifying strand casting and variable drive means with a presetable feedback loop for controllably withdrawing the strand as cast, the method which comprises:
(a) determining actual heat removal rate of the cooling means during strand casting;
(b) determining a calculated minimum level of heat removal rate according to either:
= BTU/min./in.
or QA2 = 2 BTU/in.
where:
k2 = predetermined constant Cp = liquid specific heat = BTU/# per °F. = 0.19 p = density, #/ft.3 S = speed, inches per min. (IPM) t = slab thickness or narrow face of mold, inches .DELTA.T2 = superheat above liquid temperature, = TT-TL, °F.
TL = Liquidus temperature, °F.
TT = Tundish temperature, °F.
W = slab width or wide face of mold, inches, as required of the cooling means to prevent strand breakout during casting;
(c) comparing outputs from only step (a) with step (b) and as a result generating a speed error signal according to either:
.DELTA.QL = QLli - QL2 ?0, No speed corrective action needed, or .DELTA.QL = QLli - QL2 <0, Take speed corrective action, based on a predetermined difference between the actual and calculated heat removal rates; and (d) modifying the preset speed of the caster drive means as a function of only the speed error signal so that the actual heat removal rate will exceed the calculated minimum level thereof.
(a) determining actual heat removal rate of the cooling means during strand casting;
(b) determining a calculated minimum level of heat removal rate according to either:
= BTU/min./in.
or QA2 = 2 BTU/in.
where:
k2 = predetermined constant Cp = liquid specific heat = BTU/# per °F. = 0.19 p = density, #/ft.3 S = speed, inches per min. (IPM) t = slab thickness or narrow face of mold, inches .DELTA.T2 = superheat above liquid temperature, = TT-TL, °F.
TL = Liquidus temperature, °F.
TT = Tundish temperature, °F.
W = slab width or wide face of mold, inches, as required of the cooling means to prevent strand breakout during casting;
(c) comparing outputs from only step (a) with step (b) and as a result generating a speed error signal according to either:
.DELTA.QL = QLli - QL2 ?0, No speed corrective action needed, or .DELTA.QL = QLli - QL2 <0, Take speed corrective action, based on a predetermined difference between the actual and calculated heat removal rates; and (d) modifying the preset speed of the caster drive means as a function of only the speed error signal so that the actual heat removal rate will exceed the calculated minimum level thereof.
2. The method of claim 1 wherein the actual and calculated heat removal rates are based on unit length of the cooling means.
3. The method of claim 1 wherein the actual and calculated heat removal rates are based on unit surface area of the strand.
4. The method of claim 1 wherein determining the actual heat removal rate occurs by measuring parameters in at least one of plural coolant flow circuits of the cooling means.
5. The method of claim 1 wherein the cooling means includes a solidification mold and the actual and calculated heat removal rates are based on unit length of the mold face periphery.
6. The method of claim 5 wherein the mold is adjustable and the heat removal rates are based on unit length of at least one face of the mold.
7. The method of claim 1 wherein the cooling means includes an adjustable solidification mold with plural faces, each with independent coolant flow circuits and some of which produce unequal cooling rates, and wherein the comparing step is operating to automatically select the lowest level actual heat removal rate present for use in generating the speed error signal.
8. The method of claim 1 wherein determining the calculated minimum level of heat removal rate output is varied by a preselectable physical property of the strand to be cast, thereby adjusting the speed error signal pro-portionally.
9. The method of claim 1 wherein the comparing step includes limiting the generating of the speed error signal to a predetermined percentage of maximum and cor-respondingly the modification of the preset caster speed.
10. The method of claim 1 further including the step of:
(e) recording or otherwise utilizing one or more parameters including the calculated minimum level of heat removal rate and the caster speed error signal.
(e) recording or otherwise utilizing one or more parameters including the calculated minimum level of heat removal rate and the caster speed error signal.
11. The method of claim 1 further including the step of:
(f) alarming impending abortive condition when the lowest actual mold heat removal rate level will no longer exceed the calculated minimum level thereof.
(f) alarming impending abortive condition when the lowest actual mold heat removal rate level will no longer exceed the calculated minimum level thereof.
12. A method of controlling heat removal from a continuous metal caster having cooling means for solidifying strand casting, the method which comprises:
(a) controllably withdrawing the strand as cast using variable drive means with a presetable feedback loop, (b) determining actual heat removal rate of the cooling means during strand casting;
(c) determining a calculated minimum level of heat removal rate according to either:
QL2 = = BTU/min./in.
or QA2 = = BTU/in.
where:
k2 = predetermined constant Cp = liquid specific heat = BTU/# per °F. = 0.19 p = density, #/ft.3 S = speed, inches per min. (IPM) t = slab thickness or narrow face of mold, inches .DELTA.T2 = superheat above liquid temperature, = TT-TL, °F.
TL = Liquidus temperature, °F.
TT = Tundish temperature, °F.
w = slab width or wide face of mold, inches, as required of the cooling means to prevent strand breakout during casting, (d) comparing outputs from only step (b) with step (c) and as a result generating a speed error signal according to either:
.DELTA.QL = QLli - QL2 <0 No speed corrective action needed, or .DELTA.QL = QLli - QL2 <0 Take speed corrective action, based on a predetermined difference between the actual and calculated heat removal rates; and (e) modifying the preset speed of the caster drive means as a function of only the speed error signal so that the actual heat removal rate will exceed the calculated minimum level thereof.
(a) controllably withdrawing the strand as cast using variable drive means with a presetable feedback loop, (b) determining actual heat removal rate of the cooling means during strand casting;
(c) determining a calculated minimum level of heat removal rate according to either:
QL2 = = BTU/min./in.
or QA2 = = BTU/in.
where:
k2 = predetermined constant Cp = liquid specific heat = BTU/# per °F. = 0.19 p = density, #/ft.3 S = speed, inches per min. (IPM) t = slab thickness or narrow face of mold, inches .DELTA.T2 = superheat above liquid temperature, = TT-TL, °F.
TL = Liquidus temperature, °F.
TT = Tundish temperature, °F.
w = slab width or wide face of mold, inches, as required of the cooling means to prevent strand breakout during casting, (d) comparing outputs from only step (b) with step (c) and as a result generating a speed error signal according to either:
.DELTA.QL = QLli - QL2 <0 No speed corrective action needed, or .DELTA.QL = QLli - QL2 <0 Take speed corrective action, based on a predetermined difference between the actual and calculated heat removal rates; and (e) modifying the preset speed of the caster drive means as a function of only the speed error signal so that the actual heat removal rate will exceed the calculated minimum level thereof.
13. Apparatus for controlling heat removal from a continuous metal caster having cooling means for solidifying strand casting and variable drive means with a presetable feedback loop for controllably withdrawing the strand as cast, the apparatus comprising:
(a) first plural means for determining actual heat removal rate of the cooling means during strand casting;
(b) second plural means for determining a calculated minimum level of heat removal rate required of the cooling means to prevent strand breakout during casting;
(c) third means for comparing outputs from only means (a) with means (b) and as a result generating a speed error signal based on a predetermined difference between the actual and calculated heat removal rates; and (d) said third means including control means for modifying the preset speed of the caster drive means as a function of only the speed error signal so that the actual heat removal rate will exceed the calculated minimum level thereof.
(a) first plural means for determining actual heat removal rate of the cooling means during strand casting;
(b) second plural means for determining a calculated minimum level of heat removal rate required of the cooling means to prevent strand breakout during casting;
(c) third means for comparing outputs from only means (a) with means (b) and as a result generating a speed error signal based on a predetermined difference between the actual and calculated heat removal rates; and (d) said third means including control means for modifying the preset speed of the caster drive means as a function of only the speed error signal so that the actual heat removal rate will exceed the calculated minimum level thereof.
14. The apparatus of claim 13 wherein the first and second plural means determine their actual and calculated heat removal rates based on unit length of the cooling means.
15. The apparatus of claim 13 wherein the first and second plural means determine their actual and calculated heat removal rates based on unit surface area of the strand.
16. The apparatus of claim 13 wherein the first plural means measures parameters and determines its actual heat removal rate in at least one of plural coolant flow circuits of the cooling means.
17, The apparatus of claim 13 wherein the cooling means includes a solidification mold and the first and second plural means determine their heat removal rates based on unit length of the mold face periphery.
18. the apparatus of claim 17 wherein the mold is adjustable and the first and second plural means heat removal rates are based on at least one face of the mold.
19. The apparatus of claim 13 wherein the cooling means includes an adjustable solidification mold with plural faces, each with independent coolant flow circuits and some of which produce unequal cooling rates, and wherein the third means automatically selects the lowest level actual heat removal rate present for use in generating the speed error signal.
20. The apparatus of claim 13 wherein the second plural circuit means determining the calculated minimum level of heat removal rate output is varied by a preselect-able physical property of the strand to be cast, thereby adjusting the speed error signal proportionally.
21. The apparatus of claim 13 wherein the third circuit means limits the generating of the speed error signal to a predetermined percentage of maximum and cor-respondingly the modification of the preset caster speed.
22. The apparatus of claim 13 further including:
(e) means for recording or otherwise utilizing one or more parameters including the calculated minimum level of heat removal rate and the caster speed error signal.
(e) means for recording or otherwise utilizing one or more parameters including the calculated minimum level of heat removal rate and the caster speed error signal.
23. The apparatus of claim 13 further including:
(f) means for alarming impending abortive condition when the lowest actual mold heat removal rate level will no longer exceed the calculated minimum level thereof.
(f) means for alarming impending abortive condition when the lowest actual mold heat removal rate level will no longer exceed the calculated minimum level thereof.
24. Apparatus for controlling heat removal from a continuous metal caster having cooling means for solidify-ing strand casting, the apparatus comprising:
(a) variable drive means with a presetable feedback loop for controllably withdrawing the strand as cast;
(b) first plural means for determining actual heat removal rate of the cooling means during strand casting;
(c) second plural means for determining a calculated minimum level of heat removal rate required of the cooling means to prevent strand breakout during casting;
(d) third means for comparing outputs from only means (b) with means (c) and as a result generating a speed error signal based on a predetermined difference between the actual and calculated heat removal rates; and (e) said third means including control means for modifying the preset speed of the caster drive means as a function of only the speed error signal so that the actual heat removal rate will exceed the calculated minimum level thereof.
(a) variable drive means with a presetable feedback loop for controllably withdrawing the strand as cast;
(b) first plural means for determining actual heat removal rate of the cooling means during strand casting;
(c) second plural means for determining a calculated minimum level of heat removal rate required of the cooling means to prevent strand breakout during casting;
(d) third means for comparing outputs from only means (b) with means (c) and as a result generating a speed error signal based on a predetermined difference between the actual and calculated heat removal rates; and (e) said third means including control means for modifying the preset speed of the caster drive means as a function of only the speed error signal so that the actual heat removal rate will exceed the calculated minimum level thereof.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US30,580 | 1979-04-16 | ||
| US06/030,580 US4235276A (en) | 1979-04-16 | 1979-04-16 | Method and apparatus for controlling caster heat removal by varying casting speed |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1152722A true CA1152722A (en) | 1983-08-30 |
Family
ID=21854881
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000348900A Expired CA1152722A (en) | 1979-04-16 | 1980-03-31 | Method and apparatus for controlling caster heat removal by varying casting speed |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4235276A (en) |
| CA (1) | CA1152722A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107649657A (en) * | 2017-08-29 | 2018-02-02 | 武钢集团昆明钢铁股份有限公司 | A kind of small billet tundish stops the method poured |
Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6054138B2 (en) * | 1981-01-08 | 1985-11-28 | 新日本製鐵株式会社 | Method for detecting inclusions in cast steel in continuous casting molds |
| FR2513912A2 (en) * | 1981-10-02 | 1983-04-08 | Fives Cail Babcock | METHOD FOR CONTROLLING THE COOLING OF THE COLORED PRODUCT IN A CONTINUOUS CASTING PLANT |
| US5020585A (en) * | 1989-03-20 | 1991-06-04 | Inland Steel Company | Break-out detection in continuous casting |
| US6125915A (en) * | 1994-03-30 | 2000-10-03 | Golden Aluminum Company | Method of and apparatus for cleaning a continuous caster |
| US6354364B1 (en) | 1994-03-30 | 2002-03-12 | Nichols Aluminum-Golden, Inc. | Apparatus for cooling and coating a mold in a continuous caster |
| US5697423A (en) * | 1994-03-30 | 1997-12-16 | Lauener Engineering, Ltd. | Apparatus for continuously casting |
| US6264767B1 (en) | 1995-06-07 | 2001-07-24 | Ipsco Enterprises Inc. | Method of producing martensite-or bainite-rich steel using steckel mill and controlled cooling |
| AU4596899A (en) | 1998-07-10 | 2000-02-01 | Ipsco Inc. | Method and apparatus for producing martensite- or bainite-rich steel using steckel mill and controlled cooling |
| MXPA00002784A (en) * | 1998-07-21 | 2005-08-16 | Dofasco Inc | Multivariate statistical model-based system for monitoring the operation of a continuous caster and detecting the onset of impending breakouts. |
| ATE290446T1 (en) * | 1999-07-06 | 2005-03-15 | Sms Demag Ag | METHOD FOR MELTING IN A CONTINUOUS CASTING MACHINE |
| CA2414167A1 (en) * | 2002-12-12 | 2004-06-12 | Dofasco Inc. | Method and online system for monitoring continuous caster start-up operation and predicting start cast breakouts |
| US6885907B1 (en) | 2004-05-27 | 2005-04-26 | Dofasco Inc. | Real-time system and method of monitoring transient operations in continuous casting process for breakout prevention |
| DE102006060673A1 (en) * | 2006-11-02 | 2008-05-08 | Sms Demag Ag | Method and control device for controlling the heat dissipation of a side plate of a mold |
| CN102740996B (en) * | 2010-02-11 | 2014-11-12 | 诺维尔里斯公司 | Casting composite ingot with metal temperature compensation |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3358743A (en) * | 1964-10-08 | 1967-12-19 | Bunker Ramo | Continuous casting system |
| CH552423A (en) * | 1972-04-18 | 1974-08-15 | Concast Ag | METHOD AND DEVICE FOR CONTROLLING HEAT EXTRACTION IN KOKILLEN DURING CONTINUOUS CASTING. |
| SU493291A1 (en) * | 1973-02-09 | 1975-11-28 | Институт Автоматики | The method of automatic control of the process of continuous casting of metals |
| US4006633A (en) * | 1976-04-22 | 1977-02-08 | Bethlehem Steel Corporation | Method and apparatus for determining heat removal from a continuous caster |
-
1979
- 1979-04-16 US US06/030,580 patent/US4235276A/en not_active Expired - Lifetime
-
1980
- 1980-03-31 CA CA000348900A patent/CA1152722A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107649657A (en) * | 2017-08-29 | 2018-02-02 | 武钢集团昆明钢铁股份有限公司 | A kind of small billet tundish stops the method poured |
Also Published As
| Publication number | Publication date |
|---|---|
| US4235276A (en) | 1980-11-25 |
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