US3270376A - Method and apparatus for continuous casting utilizing solidified skin thickness determinations - Google Patents

Method and apparatus for continuous casting utilizing solidified skin thickness determinations Download PDF

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US3270376A
US3270376A US233723A US23372362A US3270376A US 3270376 A US3270376 A US 3270376A US 233723 A US233723 A US 233723A US 23372362 A US23372362 A US 23372362A US 3270376 A US3270376 A US 3270376A
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Prior art keywords
strand
signal
signals
skin thickness
skin
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Thalmann Armin
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SMS Concast AG
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Concast AG
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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
    • B22D11/225—Controlling or regulating processes or operations for cooling cast stock or mould for secondary cooling
    • 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
    • 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
    • B22D11/20—Controlling or regulating processes or operations for removing cast stock
    • B22D11/207—Controlling or regulating processes or operations for removing cast stock responsive to thickness of solidified shell
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/07—Analysing solids by measuring propagation velocity or propagation time of acoustic waves
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D27/00—Simultaneous control of variables covered by two or more of main groups G05D1/00 - G05D25/00
    • G05D27/02—Simultaneous control of variables covered by two or more of main groups G05D1/00 - G05D25/00 characterised by the use of electric means

Definitions

  • the output of a continuous casting machine depends from the material and the section to be cast, from the I quality thereof, the heat absorption capacity of the plant etc. By means of known empirical figures, it is possible to determinate the values for the required cooling and for the optimum casting speed.
  • the liquid metal core or pool thereby represents a measure for these values.
  • This core is surrounded by a solidified external zone called the skin or crust of the strand and if the shape of the core is considered as a measure for the cooling and the casting speed then also the thickness of the skin will be a measure for these values. If the casting speed and the cooling are constant, then theoretically the thickness of the skin at a determinated level in the range of the core also should always be the same. But reduction of the casting temperature during the casting operation, the adjustment of the lowering speed due to modification-s in the feed of the liquid casting material and other factors may, however, modify the shape of the pool and thus also the thickness of the solidified skin.
  • the invention contemplates a method for continuous casting comprising the steps of ascertaining during the casting operation, and in a range in which the strand shall have a predeterminated skin thickness in accordance with the requirements of the material, at least periodically this skin thickness and of using the measured value-s for controlling the machine in the sense of these requirements.
  • this method makes possible for an optimum use of the machine in that it does not only measure the skin thickness but moreover compares the obtained values with a nominal value for the skin thickness and makes use of the produced signals for controlling the machine.
  • the signals for this control are continuously produced during the casting operation.
  • the obtained values for the deviations of the actual skin thickness from the nominal value therefor may be used to control the lowering speed, the cooling intensity or both these factors.
  • the same signals may be used to control other factors, such as for example the feed of liquid metal.
  • waves, electric current or rays are sent transversally through the strand and give indications on the transitions from the .solid to the liquid state within the portions of the strand penetrated thereby, these indications being given in the form of signals.
  • Radioactive rays for example gamma-rays have the property to be responsive to the density of a material. If, still in the mentioned range, an emitter, for example a source of cobalt-60, is arranged on one side of the strand while opposite thereof there is arranged a receiver, a difference in the received intensity will appear on the receiving side due to the different densities of the liquid and of the solid material. This difference may be used to localize the transition from solid to liquid in the material of the strand and by comparing the nominal value of the skin thickness with this localized point, for example in a discriminator, a signal may be produced that may be used for controlling the machine after amplification.
  • an emitter for example a source of cobalt-60
  • waves For localizing the transitions from solid to liquid of a material, it is also possible to use waves, whereby waves of high frequency such as for example waves produced by ultrasonic emitters, are particularly appropriate.
  • An ultrasonic emitter placed in the selected range on one side of the casting emits high frequency waves transversally to the casting axis. These waves are reflected at the points of transition from solid to liquid. This reflection generally designated by echo is received in a receiver placed on the same side of the strand.
  • the time intervals between the emission of the pulses and their reception, constitute an indication for the point of reflection. Such time intervals may be compared in a discriminator with a nominal value, whereby the produced signals after amplification serve to controlthe machine.
  • a further possibility of coupling the ultrasonic waves may consist in the use of a jet of water under pressure between the emitter and the receiver on the one hand and the hot strand on the other hand.
  • This jet is directed to impact perpendicularly onto the strand with a pressure that makes the water pierce through the vaporous layer on the casting surfaces to be described hereinafter, due to the kinetic energy imparted to the jet by this pressure.
  • the skin thickness In order to obtain a precise picture of the pool or liquid core in the strand it may be advantageous to measure the skin thickness at several points in the range of this core. The obtained values make possible by interpolation to figure out the shape and size of the core. It is also possible to compare the obtained measurements for the skin thickness with each other. For example the sum of all measured skin thicknesses may be compared with the sum of the nominal values, or the signal for the smallest skin thickness may be found out and only after such a result is present, the machine may be controlled or the control of the machine may be influenced.
  • the requirements of the material may ask for further parameters influencing the adjustment to be considered.
  • Such parameters are the temperature of the casting surface, the temperature of the liquid metal previous to its arrival into the die, etc.
  • the measured actual values of these parameters may again be compared with appropriate nominal values in order to influence, by means of appearing deviations the control of the machine by the deviations of the actual from the nominal skin thickness.
  • FIGURE 1 diagrammatically illustrates a continuous casting machine
  • FIGURE 2 shows the arrangement of an emitter and of a receiver for carrying out the ultrasonic echo method
  • FIGURE 20 shows a sequence of pulses
  • FIGURE 2b shows a block diagram illustrating the production of control pulses in the echo method
  • FIGURE 20 shows a series of signal forms
  • FIGURE 3 shows the arrangement of emitter and receiver for carrying out the ultrasonic method of penetration with a coupling by water jets and ionization of the vapor layer;
  • FIGURE 3a shows a sequence of pulses
  • FIGURE 3b is a block diagram illustrating the production of control pulses according to this method
  • FIGURE 3c shows forms of signals obtained thereby
  • FIGURE 4 shows the arrangement of emitter and receiver in the method using gamma-rays passing through the strand
  • FIGURE 44 shows a sequence of signals
  • FIGURE 41 is a block diagram illustrating the production of control pulses according to this method.
  • FIGURE 40 shows forms of signals
  • FIGURE 5 illustrates a method using electrical resistance
  • FIGURE 5a is a block diagram illustrating the production of control pulses according to this method
  • FIGURE 5b shows signal shapes
  • FIGURE 6 illustrates the determination of the surface temperature of the strand by means of a thermo-element
  • FIGURE 6a is a block diagram illustrating the production of temperature signals
  • FIGURE 7 shows the determination of the surface temperature of the strand by means of a ray-pyrometer
  • FIGURE 7a is a block diagram showing the production of temperature signals in accordance with this last method
  • FIGURE 8 is a block diagram illustrating the evaluation of several measurements of the skin thickness
  • FIGURE 9 is a block diagram showing the evaluation of the pulses according to FIGURES 2 and 3;
  • FIGURE shows signal forms
  • FIGURE 10 is a block diagram illustrating the evaluation of the signals according to FIGURES 4 and 5, and
  • FIGURE 10a shows signal forms.
  • FIGURE 1 This figure represents a conventional continuous casting machine to which the invention may be applied.
  • Reference numeral 11 designates a lad-1e containing liquid metal for example liquid steel that is poured into an intermediate container or tundish 12. From the tundish 12 the liquid metal is guided into an oscillating, Watercooled die 13 in which is formed a solidified external zone the so-called crust or skin. The liquid metal enclosed within this skin is generally referred to as pool or liquid core. The skin and the core together form a strand 14 which is drawn from the die 13 in well known manner at a determinated speed first by means of a dummy-bar I9. Thereby the strand is cooled in a secondary cooling zone 15 through which it is guided.
  • the cooling to which the strand is submitted in this secondary cooling zone solidifies more and more, i.e. the liquid core becomes smaller and smaller.
  • the solidified strand 14 is drawn off by a set of rollers 16 and is deviated by a bending mechanism 17.
  • a straightening device 18 finally straightens the strand again whereafter it is cut into lengths.
  • Detection means 20 for determinating the skin thickness are advantageous-1y arranged immediately after the die or mould 13. They may of course also be placed at any other point or at several points in the range of the liquid core.
  • FIGURES 2-2c In FIGURE 2 the detection means 20 is shown in form of an ultrasonic emitter 21 and receiver 22 lodged.
  • a water-cooled roller 23 This roller 23 is pressed by means of a pressure device (not represented) against the strand 14 including in its interior the liquid core'S. Between the strand 14 and the roller 23 the cooling water 24 of the secondary cooling is dammed in the roller 23 and the cooling water 24 forms the coupling fluid for the ultrasonic waves between the emitter 21, the strand 14 and the receiver 22.
  • the emitter 21 emits ultrasonic Waves in direction towards the strand 14.
  • the waves are reflected towards the receiver 22 at the points of transition a-e between different fluid states so that there is obtained a sequence of pulses as shown in FIG. 2a.
  • the emission of such waves is repeated at regular time intervals t1 with a pulse 0.
  • the reflection of this pulse at point a (transition from the cooling water for the roller to the roller) supplies in the receiver an echo pulse 1, at the point b (transition between the roller and the strand surface) an echo pulse 2, at the point (transition from solid to liquid steel) an echo pulse 3, at the point d (transition from liquid to solid) an echo pulse 4 and at the point e (strand surface) an echo pulse 5.
  • the impact of the pulses on the receiver 22 takes place at time intervals t.
  • the time interval between the emission of pulse 0 and the receipt of the echo pulses is -a measure for the distances covered by the waves.
  • a time interval- 14 between the pulses 2, 3 and 4, 5, respectively corresponds to a skin thickness K between the points b, c and d, e, respectively.
  • the pulses 2 and 3 will be considered hereafter.
  • the time interval t4 it is necessary to introduce internal control time intervals 12 and t3.
  • the time interval 12 corresponds to the interval between the emission of pulse 0 and an assumed time point P between the echo pulses 1 and 2, while the time interval 13 extends from said point P to an assumed time point Q between the pulses 3 and 4.
  • the pulse sequence according to FIGURE 2a is now evaluated to form control signals corresponding to the skin thickness, by means of a diagram illustrated in FIG- URE 2b.
  • FIGURE 20 The signal forms appearing at the outlets of the blocks are shown in FIGURE 20, whereby it is assumed for the signal sequence at the left a measured actual skin thickness inferior to the nominal skin thickness and for the signal sequence at the right a measured actual skin thickness superior to the nominal skin thickness.
  • a pulse generator 30 produces the tension pulse 0 which, as already mentioned, is repeated at regular time intervals t1.
  • These tension pulses 0 on the one hand act onto an ultrasonic emitter 21 for example onto an emitter with an oscillating quartz and on the other hand onto time elements 31 and 32. In the emitter 21 these pulses are transformed into ultrasonic waves.
  • the time elements 31 and 32 are switched-in by the pulses A1 of the generator 30 during the time intervals 12 and (t2+t3), respectively and they issue at their outlets signals A4 and A5, respectively.
  • the signals A4 and A of the time elements 31 and 32 act onto a 0-1-implication member 33 producing at its outlet a signal A6 only when at its inlet the signal A4 is zero and simultaneously the signal A5 is one. The signal A6 thus extends over the time interval t3.
  • the echo pulses 1-5 are received by the receiver 22, which may be a dynamical microphone.
  • the outlet signals A2 of the receiver 22 are amplified by an amplifier 34 to a level A3.
  • the signals A3 and the signal A6 act onto a gate 35.
  • the signal A3 may appear at the outlet of the gate 35 as signal A7 only when the signal A6 with the value 1 is present. Consequently pulses may pass through the gate 35 only during the time interval t3, ie the echo pulses 2 and 3 which are contained in the outlet signal A7 may pass through.
  • This signal A7 now acts onto both inlets of a bistable sweep stage 36 which is switched-in by the echo pulse 2 and switched-off by the echo pulse 3.
  • the outlet signal A8 with the switch-in time t4 and [4, respectively, represents the actual value of the skin thickness K.
  • the outlet signal A8 acts onto a differentiating member 37, the outlet signal A9 of which leads to a rectifier 38 which cuts off the negative portion of this signal A9 leading to the production of a signal A10.
  • this signal A10 there is switched in a time element 39 for the nominal value with adjustable delay time t5.
  • the outlet signal All of this time element 39 with the delay time t5 thus represents the nominal value of the skin thickness K. r
  • the actual value and the nominal value are discriminated. Thereby the signal A8 for the actual value and the signal A11 for the nominal value act onto implication members 40 and 41.
  • the 1-0-implication member 40 supplies at its outlet a signal A12 only provided that the signal A8 for the actual value is present and simultaneously the signal A11 for the nominal value disappears, in other words each time I4 is superior to t5.
  • the O-I-implication member 41 only supplies at its outlet a signal A13 when the signal A8 for the actual value disappears and simultaneously the signal A11 for the nominal value is present, i.e. when t4 is inferior to t5. Consequently the outlet A12 only supplies a signal when the skin thickness K exceeds the nominal value.
  • the outlet A13 further supplies a signal only when the actual skin thickness is inferior to the nominal value therefor.
  • the pulse duration of these signals is directly proportional to the deviation from the nominal value. Whenever no signal appears at the outlets A12 and A13 the skin thickness corresponds to the nominal value.
  • the actual skin thickness is measured continuously.
  • FIGURES 3-30 illustrates the method of penetration.
  • An emitter 50 and a receiver 51 are each lodged in a water container 52 and 53, respectively.
  • Each of these containers 52 and 53 is provided with a jet nozzle by means of which it is possible to direct a jet of cooling water 54 and 55, respectively under such pressure against the strand 14 that this jet may be used as coupling means for transmitting ultrasonic waves to the strand.
  • sources of current 56 and 57 are connected on the one hand, with water housings 52 and 53, respectively, which are electrically insulated from the strand, and on the other hand with the contact rollers 58 and 59, respectively.
  • a vapor film or layer is formed between the cooling water jets 54 and 55, respectively, and the hot surface of the strand.
  • This hot surface and the jets of water 54 and 55, respectively, serve as electrodes separated from each other :by the vapor film acting as insu lator.
  • By applying a voltage between the electrodes a high electrical field strength is produced in the very thin vapor film leading to gas discharges. Thereby the vapor molecules are ionized and wander back in the liquid.
  • By adjusting the applied voltage it is possible to reduce the vapor film to zero so that the transmission of ultrasonic Waves is not hindered anymore.
  • the emitter 50 emits ultrasonic waves in direction to the strand 14 and to the receiver 51. There is formed a pulse sequence according to FIGURE 3a. The emission of these waves takes place at regular time intervals :10 by means of a pulse The impact of a pulse 1' representing the emission pulse 0 delayed by its passage through the material of the strand on the receiver 51 takes place after a time interval t. This interval between the emission of the pulse 0' and the receipt of pulse 1' thus constitutes a measure for the dimension of the liquid core S plus both skin thicknesses K.
  • the time interval 120 represents the interval from the emission pulse 0' to an assumed time point R immediately before pulse 1', while the time interval 230 extends from this time point R to an assumed time point M immediately after the pulse 1.
  • the time interval t40 begins at point R and ends at pulse 1.
  • the pulse sequence according to FIGURE 3a is now transformed according to the block diagram of FIGURE 3b into control signals corresponding to the skin thickness.
  • the associated signal forms are shown in FIGURE 30, whereby for the signals represented at the left there is assumed an actual skin thickness too small with regard to the nominal skin thickness While at the right in this figure, there is assumed that the actual skin thickness is superior, to the nominal thickness.
  • FIGURE 3a The evaluation of the pulse sequence according to FIGURE 3a is effected in the same manner as has already been described for FIGURE 2b, whereby a ferromagnetical vibrator is used in the emitter 50 in lieu of the oscillating quartz in the emitter 21 and a crystal microphone is used in the receiver 51 in place of the dynamical microphone in the receiver 22.
  • the only difference with respect to FIGURE 2b remains solely in the switch-in triggering of the bistable sweep stage 36. While this is effected in FIGURE 2b by signal A7 of the prior stage 35, in FIGURE 3b a switch-in signal B must be separately produced since there is no corresponding pulse.
  • the output signal A6 of the O-l-implication member 33 is transformed into a signal B14 by means of a differentiating member 59.
  • a rectifier 60 the negative portion of the signal B14 is cut off so that the mentioned switch-in signal B in form of a signal B15 is produced.
  • the further production of the signals B8 to B13 is effected similarly to that of the signals A8 to A13 in FIGURE 2b.
  • the detection means 20 consists of a source of rays 70, for example of a source of 00-60 and of a radioactivity responsive element 71, for example a Geiger counter. In order to protect this counter 71 from heat, it is surrounded by a cooling mantle 69.
  • the gamma-rays emitted by the source 70 penetrate through the strand 14 and are transformed in the Geiger counter 71 into a continuous pulse sequence having as parameter the time I according to FIGURE 40.
  • the rate of admission of the gamma-rays in the Geiger counter 71 varies With modifications of the density in the penetrated strand 14 and more particularly with any modification of the thickness K of the skins and consequently with the size of the liquid core S.
  • the evaluation of this pulse sequence is effected according to the block diagram of FIGURE 4b.
  • the signal forms appearing at the Outlets of the blocks are shown in FIGURE 40, whereby on the left side thereof the actual skin thickness is larger than the nominal value and on the right side thereof, the actual skin thickness is smaller than the nominal value.
  • the pulses C1 supplied by the Geiger counter 7 are amplified to a level C2 by means of an amplifier 72.
  • These outlet pulses O2 act onto a pulse transformer '73 which lets pass only a predetermined part of the pulses, for example only each third pulse.
  • the average number of outlet pulses C3 in a time interval t constitutes a measure for the actual value of the skin thickness K, i.e. the outlet signal C3 by its frequency of pulses represents the actual value of the skin thickness.
  • this actual value In order to make use of this actual value for control purposes this actual value must first be compared with a nominal value for the skin thickness.
  • the outlet signal C5 of this gate by its frequency of pulses, represents the desired nominal value for the skin thickness.
  • the signals 03 and 05 respectively, owing to their opposite polarity, lead to an addition or subtraction, respectively of the voltage of a storing element contained in the integrating member 76.
  • the outlet signal C7 of the amplifier acts onto Schmidt triggers 7 8 and 79.
  • the trigger 78 forms an outlet signal 08 only when signal C7 is larger than a predetermined positive value p, i.e. when the skin thickness K is too small.
  • an outlet signal C9 can only be formed at the trigger 79 when the signal C7 exceeds a predetermined negative value n, i.e. when the skin thickness K is too large. If no signals C8 or C9 appear, this means that the skin thickness K actually corresponds to its nominal value.
  • FIGURES 5-56 FIGURE 5 illustrates a method based on the electrical conductivity, in which contact rollers 99 and 91 are pressed against the strand 14. These contact rollers are supplied with current from an evaluation circuit 92 and this current passes through the strand 14. In accordance with the thickness of the two skins K and consequently with the size of the liquid core S the electrical resistance between the contact rollers and 91 varies.
  • the evaluation circuit is shown in form of a block diagram in FIGURE 5a. All signal forms appearing at the outlet of the blocks are shown in FIGURE 5 b.
  • a resistance measuring bridge 94 in form of a Wheatstone or Thomson bridge is supplied from a rectangular generator 93 the output signal of which is designated by D1.
  • D1 the resistance produced by the strand 14 between the contact rollers 90 and '91 is contained as a measure for the actual value of the skin thickness K.
  • a potentiometer serving to assign a measure for the nominal value of the skin.
  • this bridge serves as discriminator since the outlet signal D2 with its phase position and its amplitude indicates whether the skin thickness is too large or too small as compared with the nominal value for the skin thickness. Whenever no signal D2 appears, i.e. when the bridge 94 is in equilibrium the skin thickness K is equal to the nominal value.
  • the alternate voltage D2 is fed to an amplifier 95 the out-let signal D3 of which on the one hand acts onto a limiting stage 96 adapted to limit the amplitude of signal D3 to a predetermined value b and on .the other hand onto a Gratz rectifier 97.
  • the outlet signal D4 of the limiting stage 96 leads to a gate stage 98 supplying an outlet signal D5 only when the outlet signal D6 of the rectifier 97 attains a predetermined value s. This last-mentioned value must be selected in 9 such manner, that the gate stage 98 is open only when the inlet signal D 4 is already limited by the element 96.
  • the outlet signal D5 acts onto phase discriminators 99 and 100.
  • the phase discriminator 100 is also acted upon by the outlet signal D1 of the rectangular generator 93.
  • the phase discriminator 99 receives the outlet signal D7 of a NOT-gate 101, to the inlet of which is fed the signal D1.
  • the discriminators '99 and 100 respectively, have the property to produce an outlet signal D8 and D9, respectively, only when both their inlet signals have equal phases. If the phases are not equal or if a phase falls out, no outlet signal is produced.
  • the appearance of an outlet signal D8 and D9, respectively, indicates a deviation of the skin thickness K from the nominal value thereof. If no signal appears, the actual skin thickness corresponds to the nominal value therefor.
  • FIGURES 25 the actual skin thickness is always compared with a nominal value for this thickness.
  • the signals produced by differences between these two values shall subsequently be transformed into control signals for adjusting the machine. This transformation may be effected by hand or automatically.
  • the signals indicating the actual skin thickness may be fed to an oscillograph mounted in the control table of the die operator without being compared with a nominal value, whereby the actual skin thickness appears on the screen of the oscillograph in form of a curve.
  • a marking brought on the screen indicates the nominal skin thickness and should the curve of the actual skin thickness depart from this marking the die operator may directly make the required changes in the control.
  • the signals representing the actual skin thickness may be fed to an indicating instrument.
  • a marking on this instrument indicates a nominal range with a minimum and a maximum nominal value. Correction of the machine by the die operator takes place only when the hand of the instrument leaves this nominal range.
  • FIGURES 6 and 6a In order to ascertain the surface temperature T of the strand 14 in FIGURE 6 there is provided a platinumrhodium thermoelement 110 scanning with its first soldering point 111 the surface of the strand 14 and icontacting with its second soldering point 112 a heat element 113. By a current source 114 and an intermediate nominal value potentiometer 115 the heating element 113 is brought to a desired nominal temperature. In accordance with the point of greater temperature at the one or at the other soldering points there is produced a positive or a negative voltage applied to an evaluating circuit 116. In the case of equality between nominal and equal temperature this voltage disappears.
  • FIGURE 6a illustrates this evaluating circuit 116 in a block diagram.
  • the very small thermo-electrical voltages E1 are amplified to a level E2 by means of an amplifier 117, this outlet signal E2 actuating Schmidt triggers 118 and 119.
  • the operation of a Schmidt trigger has already been described with respect to FIGURE 4.
  • the appearance of outlet signals E3 and E4 at the triggers 118 and 119, respectively, indicates deviations of the actual temperature from the nominal temperature. No signal appears each time the actual temperature coincides with the nominal temperature.
  • FIGURES 7 and 7a In order to ascertain the surface temperature T of the strand 14 use may also be made of a ray-pyrometer such as shown for example in FIGURE 6. To this end the temperature radiation of the strand surface is directed through a lens onto a first photo-electric resistance mounted into an evaluation circuit 131. The temperature radiation of a further source of heat 132 is directed through a lens 133 onto a second photo-electric resist ance. This last-mentioned source of heat 132 is maintained at the desired nominal temperature by a source of current 134 by means of a nominal value potentiometer 135.
  • FIGURE 70 the evaluating circuit 131 is shown by way of a block diagram.
  • the latter corresponds to that of FIGURE 5a with the exception that instead of the measuring bridge 94 having resistances in the branches of the bridge, there is provided in this example a measuring bridge 136 having mounted into its branches the two mentioned photo-electric resistances.
  • the appearance of outlet signals F8 and F9 corresponding to the outlet signal-s D8 and D9, respectively, in FIGURE 5, indicates a deviation of the actual temperature from the nominal temperature. No signal appears when both these temperatures are equal.
  • FIGURE 8 This figure illustrates the comparison of three measurements of the skin thickness taken at diflerent places in the range of the liquid core for the purpose of producing a single signal for controlling the machine. Thereby two possibilities of comparison shall be described:
  • a control signal shall only be produced when only one of the three measurements is positive or negative.
  • the possibilities of comparison may be selected by a program switch 154.
  • the illustrated position of switch 144 corresponds to the second of the above-mentioned possibilities (case b).
  • the signals G1, G2, G3 for too thick skins act onto an OR-gate 140 and onto an AND- gate 142, while the signals G4, G5, G6 for too thin skin-s are directed to an OR-gate 141 and to an AND-gate 143.
  • An outlet signal G7 may only be produced at gate 140 when one of the signals G1, G2, G3 is present and analogously an outlet signal G8 may only be produced at gate 141 when any of the signals G4, G5, G6 is present.
  • a signal G9 at gate 142 can only be produced when all three signals G1, G2, G3 are present, while a signal G10 at gate 143 canonly be produced when all of the signals G4, G5, G6 are present. Consequently the signals G11 and G12, respectively, form the mentioned single signal for the control.
  • FIGUR'ES 9 and 9a The evaluation of the signals produced by ultrasonic waves, for indicating deviations of the actual skin thick- 1 1 ness from a nominal skin thickness (FIGURES 2 and 3) and of the signals indicating deviations of the surface temperature of the strand from a nominal value is effected according to the block diagram of FIGURE 9. For the evaluation of these signals, the following adjusting functions are assumed.
  • the pulses H1 and H2 correspond to the pulses A12 and A13 in FIGURE 2b and B12 and B13 in FIGURE 3b.
  • the counter 150 adds the pulses H1 and subtracts the pulses H2 while the counter 151 subtracts the pulses H1 and adds the pulses H2.
  • the pulses H1 and H2 respectively, exceed a predeterminated value s, an outlet signal H3 and H4, respectively, is produced.
  • NOR-gate 152 For the logistical connection of all control signals for the carrying out of the mentioned adjusting functions there are provided a NOR-gate 152, an OR-gate 153 and AND-gates 154, 155', 156, 157.
  • the temperature signals H5 and H6 correspond to the signals E3 and E4 of FIGURE 6a or to the signals F8 and F9 of FIGURE 7a.
  • an outlet signal H8 will appear only provided that one of the signals H6 or H7 is present.
  • An outlet signal H9, H10, H11, H12 may appear at gates 154, 155, 156, 157, respectively, only provided that the signals H 4- and H7, H4 and H5, H6 and H8, H4 and H6, respectively, are present simultaneously.
  • the duration of the signals H9, H10, H11, H12 is different. For the stepwise actuation of the adjusting members it is desirable that these signals appear within a predeterminated time interval in order to obtain a constant adjusting action. This end the signals H9, H10, H11, H12 act onto a pulse former 158, 159, 1 60, 16-1, re-
  • the outlet signals H13, H14, H15, H16 of this pulse former appear with a selective duration k independently of the duration of the corresponding inlet signals.
  • the period k must be of such length that With one evaluated control order the number of pulses on the counters and 151, respectively, is lowered beneath the pro-selected value.
  • a control order for the adjusting members has its effeet in the strand 14 only after a certain time. in order to make inactive pulses appearing in the meantime, there is provided a locking device.
  • This device consists of elements 166, 16 7, 168 and 169.
  • the NOR-gate 166 has an outlet signal H17 only when the signals H13, H14, H15 and H16 miss simultaneously.
  • the signal H17 is transformed into a signal H18 which has its negative portion cut otf by a rectifier 16 8.
  • the thus obtained outlet signal H19 acts onto the'time member 169 and switches-in the latter for the mentioned locking time h resulting in the formation of the control locking signal H20.
  • the signals H13, H14, H15, H16 and the control locking signal H20 act onto l-O-implication members 162, 163, 164, respectively.
  • Each of the implication members 162, 16 3, 1 64 and 165 supplies its outlet signal H21, H22, H23 and H24, respectively, provided that the signal H13, H14, H15 and H16 is present and simultaneously the signal H20 disappears.
  • the outlet signals H21, H22, H23 and H24 thus represent the control signals increase cooling, reduce cooling, increase casting speed and reduce casting speed, respectively.
  • the outlet signals H21 and H22 act onto a motor .170 adjusting a cooling fluid valve 171 for the secondary cooling of the strand 14.
  • the outlet signals H23 and H24 operate a motor 172 for adjusting the held excitation 17-3 of a Ward-Leonard-device associated to the rollers 16.
  • the signals H2 1 and H22 produce in the motor a positive and negative rotation, respectively, for increasing and reducing respectively, the amount of cooling fluid at valve 171.
  • the signals H2 3 and H24 result in the motor 172 into a positive and negative rotation, respectively, for increasing and reducing, respectively, the field strength of the Ward-Leonard motor so as to modify the casting speed.
  • This modification of the casting speed due to its connection with further parts of the machine requires further adjustment such as the die oscillation, the speed of the straightening device, the speed of a rolling mill that may be connected after the continuous casting machine etc. All these adjustments are thus influenced by the signals signalling deviations of actual values from nominal values for the strand.
  • FIGURE 10 The evaluation of the signals produced by gamma-rays and indicating deviation of the actual skin thickness from the nominal skin thickness (FIGURE 4) and of the signals obtained by the electrical resistance method (FIG- URE 5) is effected in accordance with the block diagram of FIGURE 10. The corresponding signal forms are visible from FIGURE 10a. The adjusting functions are assumed to be the same as in FIGURE 9. Also the evaluation circuit is similar with the exception that the production of signals J3 and J4 from the signals 31 and 32 indicating deviations of the skin thickness is effected differently. Instead of the designation of the signals by H in FIGURE 9, in FIGURE 10 the signals are designated by J.
  • time interval is effected in the following example by a time element.
  • the signals I25 and J27 switch in a time element 181 and 1-84, respectrvely, which switch olf after a certain time z. If the s gnals J25 or J27, disappear before the time z ends the time elements 181 and 1.84, respectively, are switched off immediately.
  • the outlet signals of the time elements 181 and 184 are designated by J26 and J28, respectively.
  • the signals J1 and J26 act onto a I-O-implication member 1 82 and the signals J2 and J28 act onto a I-O-implication member .185.
  • outlet signals J6 and J4 may be produced only when on the one hand the signals 11 and J2, respectively are present and on the other hand the signals J26 and J28, respectively, are missing.
  • a time interval k identical as to its function with the time interval k in FIGURE 9 is selected in such manner, that for each evaluated control order the signals J1 or J2, respectively, disappear.
  • the invention is not limited to the few examples given herein'before.
  • the method of continuous casting which comprises the steps of continuously casting molten metal into a mold, cooling said mold to solidify the metal along the periphery to form a strand having a solidified skin enclosing a molten core, withdrawing said strand from said mold in continuous manner, cooling said strand to progressively solidify the molten metal in said core, measuring the thickness of the solidified skin of the strand enclosing the molten core and controlling the casting process in accordance with said measurement of the skin thickness to maintain the skin thickness enclosing the molten core with sufiicient material to withstand working operation according to the metal to be cast.
  • the method of continuous casting which comprises the steps of continuously casting molten metal into a mold, cooling said mold to solidify the metal along the periphery to form a strand having a solidified skin enclosing a molten core, withdrawing said strand from said mold in continuous manner, cooling said strand to pro gressively solidify the molten metal in said core, measuring the thickness of the solidified skin of the strand repeatedly, averaging said measurements thereby to overcome measurement distortion due to unevenness of and lack of homogeneity of said skin, and control-ling the casting process in accordance with said average of said measurements of skin thickness to maintain the skin thickness with sufficient material to withstand working operation according to the metal to be cast.
  • the method of continuous casting which comprises the steps of continuously casting molten metal into a mold, cooling said mold to solidify the metal along the periphery to [form a strand having a solidified skin enclosing .a molten core, withdrawing said strand from said mold in continuous manner, cooling said strand to progressively solidify the molten metal in said core, transmitting signals through said strand in a direction transverse to the axis of said strand, detecting signals reflected within said strand by the interfaces between solidified and molten metal, and .controlling the casting process in response to said detected reflected signals which serve as an indication of the location of such interfaces to maintain the skin thickness with sufiicient material to withstand working operation according to the metal to be cast.
  • the method of continuous casting (which comprises the steps of continuously casting molten metal into a mold, cooling said mold to solidify the metal along the periphery to form a strand having a solidified skin enclosing a molten core, withdrawing said strand from said mold in continuous manner, cooling said strand to progressively-solidify the molten metal in said core, measuring the thickness of the solidified skin of the strand at several positions displaced along the axis of said strand from the position of said first measurement and using the resulting measurements for controlling the casting process to maintain the skin thickness :with sufficient material to withstand working operation according to the metal to be cast.
  • a continuous casting plant comprising a continuous casting mold to receive molten metal and to solidify the periphery of said molten metal into a skin defining a strand and enclosing therewithin a molten core; means for pouring molten metal into said mold; means for withdrawing in continuous manner the strand cast by said mold; means for cooling said strand to progressively solidify the molten metal enclosed in the core of the strand; means for measuring the skin thickness of said strand after issuance of the strand from said mold; said measuring means comprising a source of ultrasonic signals, means for introducing said ultrasonic signals into said casting in a direction transverse to the longitudinal axis thereof, means for receiving said ultrasonic signals reflected from the interface between solidified and molten metal in said strand to determine the position of the interface between the solidified skin and the molten core; and means responsive to said measurement of skin thickness for controlling the casting process to maintain the skin thickness at that thickness corresponding to optimum casting speed and casting quality.
  • a continuous casting plant comprising a continuous casting mold to receive molten metal and to solidify the periphery of said molten metal into a skin defining a strand and enclosing therewith in a molten core; means for pouring molten metal into said mold; means for Withdrawing in continuous manner the strand cast by said mold; means for cooling said strand to progressively solidify the molten metal enclosed in the core of the strand; means for measuring the skin thickness of said strand after issuance of the strand from said mold; said measuring means comprising a source of ultrasonic signals, means for introducing said ultrasonic signals into said casting in a direction transverse to the longitudinal axis thereof, and means for receiving signals passing through said strand rfrom said source to determine the position of the interface between the solidified skin and the molten core in said strand; and means responsive to said measurement of skin thickness for controlling the casting process to maintain the skin thickness at that thickness corresponding to optimum casting speed and casting quality.
  • a continuous casting plant comprising a continuous casting mold to receive molten metal and to solidify the periphery of said molten metal into a, skin defining a strand and enclosing therewithin a molten core; means for pouring molten metal into said mold; means for withdrawing in con-tinuous manner the strand cast by said mold, means for cooling said strand to progressively solidify the molten metal enclosed in the core of the strand; means .for measuring the skin thickness of said strand after issuance or the strand from said mold; said measuring means comprising means for the generation of a signal, fluid coupling means coupling said signal generator to said strand to introduce said signal into said casting in a direction transverse to the longitudinal axis thereof, and means for receiving said signal to determine the position of the interface between the solidified skin and the molten core in said strand; and means responsive to said measurement 0t skin thickness for controlling the casting process to maintain the skin thickness at that thickness corresponding to optimum casting speed and casting quality.

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Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3344841A (en) * 1965-06-18 1967-10-03 Koppers Co Inc Control apparatus for a continuous cast billet
US3421569A (en) * 1966-03-11 1969-01-14 Kennecott Copper Corp Continuous casting
US3478808A (en) * 1964-10-08 1969-11-18 Bunker Ramo Method of continuously casting steel
US3491824A (en) * 1966-12-06 1970-01-27 Boehler & Co Ag Geb Process of producing rolled stock from a high-melting metal by continuous casting and rolling operations
US3543567A (en) * 1967-11-20 1970-12-01 Concast Ag Method of intensifying reflection of ultrasonic waves from boundary between solid and liquid metal
US3635620A (en) * 1967-02-13 1972-01-18 Gen Cable Corp Apparatus for controlling the dimensions of multiple layers of extruded insulation
US3707184A (en) * 1969-05-20 1972-12-26 Concast Ag Withdrawal and straightening apparatus for continuous casting
US3834445A (en) * 1971-09-20 1974-09-10 Voest Ag Continuous casting mold having a breakout sensing and control device
US5355935A (en) * 1989-06-12 1994-10-18 Institut De Recherches De La Siderurgie Francaise (Irsid) Method and device for vibrating an ingot mould for the continuous casting of metals
US5509460A (en) * 1994-08-25 1996-04-23 Massachusetts Institute Of Technology Solid/liquid interface detection in continuous casting processes by γ-
US5673746A (en) * 1994-08-25 1997-10-07 Massachusetts Institute Of Technology Solid/liquid interface detection in casting processes by gamma-ray attenuation
ES2328206A1 (es) * 2007-11-07 2009-11-10 Zunibal, S.L Traductor para colada de hierro.
US9327347B2 (en) 2008-03-05 2016-05-03 Southwire Company, Llc Niobium as a protective barrier in molten metals
US9382598B2 (en) 2010-04-09 2016-07-05 Southwire Company, Llc Ultrasonic device with integrated gas delivery system
US9481031B2 (en) 2015-02-09 2016-11-01 Hans Tech, Llc Ultrasonic grain refining
US9528167B2 (en) 2013-11-18 2016-12-27 Southwire Company, Llc Ultrasonic probes with gas outlets for degassing of molten metals
US9617617B2 (en) 2010-04-09 2017-04-11 Southwire Company, Llc Ultrasonic degassing of molten metals
CN107377920A (zh) * 2017-06-28 2017-11-24 秦皇岛首秦金属材料有限公司 一种厚板坯尾坯二冷水脉冲控制方法
US10022786B2 (en) 2015-09-10 2018-07-17 Southwire Company Ultrasonic grain refining
US10233515B1 (en) 2015-08-14 2019-03-19 Southwire Company, Llc Metal treatment station for use with ultrasonic degassing system

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1508919B1 (de) * 1966-03-05 1971-02-04 Olsson Ag Erik Anordnung eines thermosensitiven Elementes in einergekühlten stanggiesskokille
JPS492659B1 (de) * 1970-12-23 1974-01-22

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2246907A (en) * 1940-04-12 1941-06-24 William R Webster Continuous molding machine
US2641034A (en) * 1949-01-29 1953-06-09 Babcock & Wilcox Co Method of and apparatus for indicating and/or controlling the level of liquid within an opaque container
US2748290A (en) * 1951-05-31 1956-05-29 Socony Mobil Oil Co Inc Measurement of wall thickness

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE502192A (de) * 1950-03-28

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2246907A (en) * 1940-04-12 1941-06-24 William R Webster Continuous molding machine
US2641034A (en) * 1949-01-29 1953-06-09 Babcock & Wilcox Co Method of and apparatus for indicating and/or controlling the level of liquid within an opaque container
US2748290A (en) * 1951-05-31 1956-05-29 Socony Mobil Oil Co Inc Measurement of wall thickness

Cited By (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3478808A (en) * 1964-10-08 1969-11-18 Bunker Ramo Method of continuously casting steel
US3344841A (en) * 1965-06-18 1967-10-03 Koppers Co Inc Control apparatus for a continuous cast billet
US3421569A (en) * 1966-03-11 1969-01-14 Kennecott Copper Corp Continuous casting
US3491824A (en) * 1966-12-06 1970-01-27 Boehler & Co Ag Geb Process of producing rolled stock from a high-melting metal by continuous casting and rolling operations
US3635620A (en) * 1967-02-13 1972-01-18 Gen Cable Corp Apparatus for controlling the dimensions of multiple layers of extruded insulation
US3543567A (en) * 1967-11-20 1970-12-01 Concast Ag Method of intensifying reflection of ultrasonic waves from boundary between solid and liquid metal
US3707184A (en) * 1969-05-20 1972-12-26 Concast Ag Withdrawal and straightening apparatus for continuous casting
US3834445A (en) * 1971-09-20 1974-09-10 Voest Ag Continuous casting mold having a breakout sensing and control device
US5355935A (en) * 1989-06-12 1994-10-18 Institut De Recherches De La Siderurgie Francaise (Irsid) Method and device for vibrating an ingot mould for the continuous casting of metals
US5509460A (en) * 1994-08-25 1996-04-23 Massachusetts Institute Of Technology Solid/liquid interface detection in continuous casting processes by γ-
US5673746A (en) * 1994-08-25 1997-10-07 Massachusetts Institute Of Technology Solid/liquid interface detection in casting processes by gamma-ray attenuation
ES2328206A1 (es) * 2007-11-07 2009-11-10 Zunibal, S.L Traductor para colada de hierro.
US9327347B2 (en) 2008-03-05 2016-05-03 Southwire Company, Llc Niobium as a protective barrier in molten metals
US9382598B2 (en) 2010-04-09 2016-07-05 Southwire Company, Llc Ultrasonic device with integrated gas delivery system
US9617617B2 (en) 2010-04-09 2017-04-11 Southwire Company, Llc Ultrasonic degassing of molten metals
US10640846B2 (en) 2010-04-09 2020-05-05 Southwire Company, Llc Ultrasonic degassing of molten metals
US9528167B2 (en) 2013-11-18 2016-12-27 Southwire Company, Llc Ultrasonic probes with gas outlets for degassing of molten metals
US10316387B2 (en) 2013-11-18 2019-06-11 Southwire Company, Llc Ultrasonic probes with gas outlets for degassing of molten metals
US9481031B2 (en) 2015-02-09 2016-11-01 Hans Tech, Llc Ultrasonic grain refining
US10441999B2 (en) 2015-02-09 2019-10-15 Hans Tech, Llc Ultrasonic grain refining
US10233515B1 (en) 2015-08-14 2019-03-19 Southwire Company, Llc Metal treatment station for use with ultrasonic degassing system
US10022786B2 (en) 2015-09-10 2018-07-17 Southwire Company Ultrasonic grain refining
US10639707B2 (en) 2015-09-10 2020-05-05 Southwire Company, Llc Ultrasonic grain refining and degassing procedures and systems for metal casting
CN107377920A (zh) * 2017-06-28 2017-11-24 秦皇岛首秦金属材料有限公司 一种厚板坯尾坯二冷水脉冲控制方法

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BE624437A (de)
DE1262518B (de) 1968-03-07
CH389173A (de) 1965-03-15

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