EP0037472A1 - Einrichtung und Verfahren für die Bestimmung der Grenzfläche flüssig-fest sowie des oberen Endes beim elektromagnetischen Giessen - Google Patents

Einrichtung und Verfahren für die Bestimmung der Grenzfläche flüssig-fest sowie des oberen Endes beim elektromagnetischen Giessen Download PDF

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Publication number
EP0037472A1
EP0037472A1 EP81101845A EP81101845A EP0037472A1 EP 0037472 A1 EP0037472 A1 EP 0037472A1 EP 81101845 A EP81101845 A EP 81101845A EP 81101845 A EP81101845 A EP 81101845A EP 0037472 A1 EP0037472 A1 EP 0037472A1
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EP
European Patent Office
Prior art keywords
casting
liquid
head
inductor
solid interface
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP81101845A
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English (en)
French (fr)
Inventor
Peter J. Kindlmann
John C. Yarwood
Gary L. Ungarean
Derek E. Tyler
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Olin Corp
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Olin Corp
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Publication date
Application filed by Olin Corp filed Critical Olin Corp
Publication of EP0037472A1 publication Critical patent/EP0037472A1/de
Withdrawn legal-status Critical Current

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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
    • 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
    • B22D11/01—Continuous casting of metals, i.e. casting in indefinite lengths without moulds, e.g. on molten surfaces
    • B22D11/015—Continuous casting of metals, i.e. casting in indefinite lengths without moulds, e.g. on molten surfaces using magnetic field for conformation, i.e. the metal is not in contact with a mould

Definitions

  • One method of controlling the casting process has been the use of an induced electromagnetic (EM) field, rather than a mold with definite walls, to both confine and shape the molten metal or alloy which is being cast.
  • EM induced electromagnetic
  • This process utilizes a strong electromagnetic field to counterbalance the metallostatic forces effected by the head of molten metal or alloy
  • the electromagnetic casting apparatus comprises a three part mold consisting of a water cooled inductor, a non-magnetic screen, and a manifold for applying cooling water to the ingot. Containment of the molten metal is achieved without direct'contact between the molten metal and any component of the mold. Solidification of the.molten metal is achieved by direct application of water from the cooling manifold to the ingot shell.
  • Another control system for electromagnetically forming ingots of fixed transverse dimension discloses minimizing variations in the gap between the molten metal and the inductor by sensing and using the gap or an electrical parameter related thereto to control the current to the inductor.
  • thermocouples spaced vertically along the container walls.
  • the thermocouples measure temperature change within the container and control an electric circuit in response to such measurement.
  • the invention is based on the fact that a sharp change in the temperature measured within the container occurs as one travels from a pool of molten metal to a point above the pool and vice versa.
  • an EM casting system has no mold or container walls to compare with.
  • EM systems typically utilize shields and coolant manifolds at the molten metal input ends of the primary casting zone. Utilization of such prior art electro-optical devices in the manner suggested by the aforementioned prior art would at the very least be complicated, if not impossible. Finally, in operating at the visable light spectrum, these devices are subject to inaccuracies based upon the existence of a dirty environment in or near a casting station.
  • a method of head top surface measurement which has been used during EM casting runs provides the use of a float device which locates the upper surface of the molten metal being EM cast.
  • reliability problems associated with having the primary measuring device in contact with or subject to damage by the melt exist.
  • This reliability problem also exists with respect to a feeler device utilized to feel or locate the interface between the liquidus and solidus parts of an ingot being electromagnetically cast.
  • these methods require that additional equipment be added to the EM containment zone which complicates the E4 casting apparatus and places the sensing elements in a very vulnerable position.
  • use of such devices during electromagnetic casting may cause surface perturbations in the liquid metal meniscus which can result in casting defects.
  • Another system for locating the head top surface in an EM casting or containment zone and a continuous casting mold utilizes at least one sensing coil placed in the vicinity of the molten metal surface in a continuous casting system.
  • the impedance value of the coil which varies as the molten metal moves up or down, is used as an indication of the location of the top surface of the melt.
  • the prior art also discloses the use of a system of intensified ultrasonic wave reflection at the solidification front of a continuously cast ingot in order to locate the front.
  • the system involves the use of electromagnetic agitating coils in the area of the solidification front.
  • Such a system is not readily adaptable to an EM casting system which, of course, itself is driven by an electromagnetic inductor.
  • Another system utilizes a plurality of fiber optic filaments secured within elements of an electromagnetic casting system, e.g. within the shield and/or manifold and/ or inductor, to measure and determine the load surface height and location of the liquid-solid interface.
  • the system uses infrared radiation emitted from the surface of the forming ingot as a measure of the desired parameters.
  • This system has the benefits of not requiring the insertion of probes into the primary casting zone, and provides other information, such as licidus temperature and maximum temperature.
  • One problem with this approach is that the system of filaments is inserted within elements of the casting system, requiring modification of the affected elements.
  • the present invention overcomes the deficiencies described above and provides an accurate means for measuring head and the location of the peripheral liquid-solid interface of the forming ingot in an electromagnetic casting station without necessitating the introduction of any sensing element into the EM casting zone enclosed by the inductor and shield without modification of the inductor or shield, simultaneously, reliably, and without creation of any safety hazards (such as would be introduced for example by devices utilizing high energy radiation).
  • the measuring system of the present invention operates efficiently in a less than perfectly clean environment such as would be found in an EM primary casting zone.
  • the present invention relates to a process and apparatus for determination and display of molten metal head and liquid-solid interface position during an electromagnetic casting run by utilizing the in-phase component of the voltage across the inductor as an indicator of head and interface position.
  • the equivalent series resistance (ESR) of the casting system is measured and monitored during the casting run. The value of this parameter is then compared with a table or chart relating the ESR of the system and the values of or changes in the values of head and liquid- ' solid interface position for a given metal or alloy being cast.
  • ESR equivalent series resistance
  • Signal generation and analysis in accordance with this invention can be carried out using either analog or digital circuitry or combinations thereof.
  • the electromagnetic casting mold 10 is comprised of an inductor 11 which is water cooled; a cooling manifold 12 for applying cooling water to the peripheral surface 13 of the metal being cast C; and a non-magnetic shield 14, Molten metal is continuously introduced into the mold 10 during a casting run, in the normal manner using a trough 15 and down spout 16 and conventional-molten metal head control.
  • the inductor 11 is excited by an alternating current from a power source 17.
  • the alternating current in the inductor 11 produces a magnetic field which interacts with the molten metal head 19 to produce eddy currents therein. These eddy currents in turn interact with the magnetic field and produce forces which apply a magnetic pressure to the molten metal head 19 to contain it so that it solidifies in a desired ingot cross section.
  • the molten metal head 19 is formed or molded into the same general shape as the inductor 11 thereby providing the desired ingot cross section:
  • the inductor may have any desired shape including circular or rectangular as required to obtain the desired ingot C cross section.
  • the purpose of the non-magnetic shield 14 is to fine tune and balance the magnetic pressure with the.hydrostatic pressure of the molten metal head 19.
  • the non-magnetic screen 14 may comprise a separate element as shown or may, if desired be incorporated as a unitary part of the manifold for applying the coolant.
  • a conventional ram 21 and bottom block 22 are held in the magnetic containment zone of the mold 10 to allow the molten metal to be poured into the mold at the start of the casting run.
  • the ram 21 and bottom block 22 are then uniformly withdrawn at a desired casting rate.
  • Solidification of the molten metal which is magnetically contained in the mold 10 is achieved by direct application of water from the cooling manifold 12 to the ingot surface 13.
  • the water is applied to the ingot surface 13 within the confines of the inductor 11.
  • the water may be applied to the ingot surface 13 above, within or below the inductor 11 as desired.
  • the present invention describes a technique for measurement of liquid head utilizing certain electrical parameters of containment inductor 11.
  • the in-phase current amplitude Io in containment inductor 11 is monitored, and signals representative of the magnitude or amplitude thereof are then utilized to extract head height and liquid-solid interface location information.
  • the in-phase current Io is a function of the resistive part of the total inductor load impedance which is made up of the resistance of inductor 11 itself, that of the shield 14 and that of the contained solid-liquid metal load.
  • the resistance of the inductor 1 1 and shield l4 are constant at constant frequency.
  • the resistance of the liquid-solid load at constant frequency is a function of themetal or alloy being cast and the proportions of liquid and solid involved because the resistivities of the two states (p s , solid and p L , liquid) differ significantly.
  • the load resistance is a function of the air gap, d (load periphery).
  • the resistances of the shield and inductor, as well as temperature of operation can be taken as constant in that their position is fixed during the casting run.
  • the frequency f is either known, being a controlled element of the electromagnetic casting system, i.e. a system driven at a known or set frequency, or it can be measured by use of a frequency counter or frequency meter.
  • the resis- t ance of the shield (R S ) and inductor (R L ) is as stated hereinabove assumed approximately constant and can be determined by measurements using an appropriate inductance/ resistance meter.
  • the inductor-ingot air gap d can be conveniently extracted from a measurement of out of phase inductor current, I 90 . This parameter is either known, being maintained constant (preferred) or can be constantly monitcred.
  • the liquid metal level relative to the inductcr m can be ascertained by any of several techniques including probes, floats or coils as described in the Prior Art Statement hereinabove.
  • this parameter can be derived from a measurement of the out of phase current in the shield.
  • the equivalent series resistance represents the total resistance load seen when looking into the two terminals of inductor 11 and includes the resistances of the shield 14, inductor 11, and the load.
  • the ESR is a function of several parameters including the values of d, h, and m. As disclosed hereinabove, except for the value of h, the values of d and m are either known or can be readily determiped. Thus, if one were to monitor or determine the value of the ESR, then it would be possible to calibrate or chart the value of the head (h).
  • FIG. 2 is a block diagram showing a system for monitoring an electromagnetic casting system in order to determine head and/or liquid-solid interface location during a casting run.
  • inductor 11 is shown connected to an electrical power supply 17 which provides the necessary current to the system at a desired frequency and voltage.
  • the power supply circuit may be considered as two subcircuits 25 and 26.
  • the external circuit 25 consists essentially of a solid state generator providing an electrical potential across the load or tank circuit 26 which includes the inductor 11.
  • Tank circuit 26 except for the inductor 11 is sometimes referred to as a heat station and includes elements such as capacitors and transformers. Both external circuit 25 and tank circuit 26 may be of a conventional design.
  • Figure 2 includes a subcitcuit RC which may be utilized in monitoring the equivalent series resistance (ESR) of a typical electromagnetic casting system.
  • the current in inductor 11 may be sensed by a conventional current sense pickup device 27 such as a current transformer.
  • a current- to-voltage scaling resistor network 29 generates a corresponding voltage.
  • This voltage is fed to a phase-locked loop circuit 30 which "locks" onto the fundamental of the current waveform and generates a sinusoidal phase reference output having a phase angle of 0° with respect to the current fundamental.
  • phase-sensitive voltage rectifier 31 derives the fundamental frequency current amplitude.
  • the voltage signal from phase-sensitive voltage rectifier 31, properly scaled, is then fed to analog voltage divider 32.
  • Phase-sensitive voltage rectifier 28 generates a signal corresponding to the in-phase (0°) voltage across inductor 11, which signal, properly scaled, is also fed to analog voltage divider 32
  • Analog voltage divider 32 divides the signals from phase-sensitive rectifiers 28 and 31, respectively, to obtain an output signal which is representative of the equivalent series resistance of the casting system which includes the load, inductor 11 and shield 14.
  • liquid head h and liquid-solid interface position s is carried out by interpolation.
  • Values of the ESR for different geometric arrangements, values of h, and liquid-solid load resistivities can be determined by suitable modeling and empirical measurement procedures and thereafter confirmed by careful measurement during actual electromagnetic casting experiments.
  • scaling is performed by empirical measurement based solely on experiment utilizing a model system and observation of a particular geometrical and alloy electromagnetic casting system.
  • Such a model electromagnetic system suitable for empirical measurements is depicted in Figure 3.
  • the contribution to the ESR from the load includes resistance contributions from the liquid and solid portions of the forming ingot.
  • the resistivity of the molten metal ( PL ) is substantially different than the resistivity of the solid metal (p S ).
  • the resistance of the load changes as the location of the liquid-solid interface changes, that is, as the interface goes up the equivalent series resistance at the terminals of inductor 11' decreases.
  • a model as depicted in Figure 3 can be set up so as to permit empirical establishment of a chart or table relating the ESR and the values of h and s for specific alloys and geometric arrangements.
  • a load C' model is set up to move vertically within the casting zone established by an inductor 11' and a shield 14' of a size and positioned in the same way as during the intended casting run. It is, of course, possible to utilize the actual casting station and/or the inductor 11 and shield 14 which would be utilized during the casting run.
  • liquid-solid front (24) or interface front be approximated through the entire load thickness, that is, the interface need not duplicate the entire interface 2 b of the load during the casting run.
  • the primary area of electromagnetic interaction is two penetration (skin) depths (2 ⁇ ) around the ingot or load model periphery.
  • the penetration of depth ⁇ is, of course, a function of the resistivity of the alloy being cast and the frequency at which the system is running.
  • a constant diameter metal head 19' such as that depicted in Figure 3 may be utilized to carry out empirical measurements for the parameter values, geometries, and alloy to be cast.
  • Such an interface would tend to give a little lower reading in the in-phase part of the current in inductor 11, that is, the reading would tend to indicate that the liquid-solid interface peripheral front is a little higher than it actually is during the casting run.
  • Testing can determine whether there is a sufficient discrepancy, and if so, whether it is tolerable or not. In any case adjustment can be built into the chart or table, or'more exact load model construction can be carried out. Finally, if the system is utilized as a determiner of variation or deviation from a desired value rather than as an exact determination of a value or position, then discrepancies might be more readily tolerable.
  • the load model C' has a solid upper portion 19' constructed of a material having a resistivity p L which closely approximates the resistivity of the molten alloy which is to be cast and a solid lower portion 18' constructed of a material having a resistivity ⁇ S which closely approximates the resistivity of the solid portion of the alloy being cast.
  • the procedure now would be to set up the electromagnetic casting model and to move the load model up and down within the model casting zone to establish the correlation between changes in ESR as a function of liquid-solid interface location or position s.
  • the solid upper portion of the load model can be changed; that is, readings in ESR variation can be taken for several different values of h.
  • the signal corresponding to the ESR eminating from analog voltage divider 32 may now readily be utilized as an indicator of head h and the position of the liquid-solid interface s.
  • This output signal is fed to analog to digital converter 42 which converts it into an appropriate digital form.
  • the output of the analog to digital converter 42 is fed to a computer 43 such as a mini-computer or microprocessor as, for example, a PDP-8 with Dec Pack manufactured by Digital Equipment, Inc.
  • the computer 43 is programmed to analyze the signal from analog voltage divider 38 in conjunction with preprogrammed geometrical and electrical parameter data to compute via a programmed chart established through empirical testing data the value of or variation in head h and liquid-solid interface position s.
  • Computer 43 then generates a signal corresponding to the value of or variations in head h and interface position s to analog converter 44 which converts the signal into an analog form which can be read on one or more readout devices 45
  • Monitoring of the ESR of the casting system can be carried out by digital means, analog, or a combination of both, and the circuit of Figure 2 merely represents one preferred form of circuitry for carrying out the monitoring and determining steps of the present invention.
  • Digital and analog circuitry may perform the same or similar functions with respect to an electromagnetic casting system.
  • the use of a microprocessor or computer is thought to be highly desirable because such a device can readily interpolate between varying points in a chart or table and would, therefore, be quite efficient in continuously providing readings of the value of or deviations from a prescribed value of h and s .
  • the monitoring and determination system of the instant invention finds utility in two types of measurements and readouts. It may be utilized to measure or approximate head height and/or liquid-solid interface position relative to some datum point, as for example, the bottom of inductor 11, or it may be utilized to monitor and determine a departure or variation in head height and/or interface position relative to a desired position or value. It is clear that in the latter use, linearity and exact pro- portionalities are less critical, that is, such a use permits or can tolerate greater slope differences. It is contemplated that such a monitoring system as an alternative to use as an absolute calibration device or interface meter might best be utilized as a reproducibility or error sensing mechanism. Thus, deviations in maintaining the head (h) at a desired value and the liquid-solid interface at a desired level (typically at the center of inductor 11) can be readily ascertained.
  • the process of the present invention is operable whether frequency (f) varies or net.
  • ESR equivalent series resistance
  • the processing mode of the ESR monitored in the electromagnetic circuit may be analog, digital, or a hybrid of both.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Continuous Casting (AREA)
EP81101845A 1980-04-07 1981-03-12 Einrichtung und Verfahren für die Bestimmung der Grenzfläche flüssig-fest sowie des oberen Endes beim elektromagnetischen Giessen Withdrawn EP0037472A1 (de)

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US13764580A 1980-04-07 1980-04-07
US137645 1980-04-07

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EP0037472A1 true EP0037472A1 (de) 1981-10-14

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0068827A1 (de) * 1981-06-26 1983-01-05 Olin Corporation Steuerung der Grenzfläche flüssig-fest beim elektromagnetischen Giessen
GB2142729A (en) * 1983-07-01 1985-01-23 Nippon Kokan Kk Method and apparatus for non-contact measurement of solidified shell of a metal casting having unsolidifed inner part
US4516625A (en) * 1983-01-10 1985-05-14 Olin Corporation Electromagnetic control system for casting thin strip
DE3427940A1 (de) * 1984-07-28 1986-02-06 Friedhelm Prof.Dr.-Ing. 6332 Ehringshausen Kahn Verfahren und vorrichtungen zur steuerung einer raumausfuellung durch metallschmelzen mit hilfe von elektromagnetischen feldern

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2027805A1 (en) * 1970-06-05 1971-12-09 Kujbyschewskij metallurgietscheskij zawoed lmeni V I Lemna, Kujbyschew (Sowjetunion) Ingot moulding in continuous and semicontin- - uous metal casting
US4161206A (en) * 1978-05-15 1979-07-17 Olin Corporation Electromagnetic casting apparatus and process
DE2812279A1 (de) * 1978-03-21 1979-09-27 Bhattacharya Sylvia Verfahren und vorrichtung zum steuern des erstarrens eines gegossenen metallischen werkstoffstueckes

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2027805A1 (en) * 1970-06-05 1971-12-09 Kujbyschewskij metallurgietscheskij zawoed lmeni V I Lemna, Kujbyschew (Sowjetunion) Ingot moulding in continuous and semicontin- - uous metal casting
DE2812279A1 (de) * 1978-03-21 1979-09-27 Bhattacharya Sylvia Verfahren und vorrichtung zum steuern des erstarrens eines gegossenen metallischen werkstoffstueckes
US4161206A (en) * 1978-05-15 1979-07-17 Olin Corporation Electromagnetic casting apparatus and process
DE2853792A1 (de) * 1978-05-15 1979-11-22 Olin Corp Induktionsgiessverfahren und vorrichtung zu dessen durchfuehrung

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0068827A1 (de) * 1981-06-26 1983-01-05 Olin Corporation Steuerung der Grenzfläche flüssig-fest beim elektromagnetischen Giessen
US4516625A (en) * 1983-01-10 1985-05-14 Olin Corporation Electromagnetic control system for casting thin strip
GB2142729A (en) * 1983-07-01 1985-01-23 Nippon Kokan Kk Method and apparatus for non-contact measurement of solidified shell of a metal casting having unsolidifed inner part
DE3427940A1 (de) * 1984-07-28 1986-02-06 Friedhelm Prof.Dr.-Ing. 6332 Ehringshausen Kahn Verfahren und vorrichtungen zur steuerung einer raumausfuellung durch metallschmelzen mit hilfe von elektromagnetischen feldern

Also Published As

Publication number Publication date
JPS56154259A (en) 1981-11-28

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Inventor name: TYLER, DEREK E.