US3875991A - Arrangement for conveying and batching liquid metal supplied from a receptacle into a mould for continuous casting of metal ingots - Google Patents

Arrangement for conveying and batching liquid metal supplied from a receptacle into a mould for continuous casting of metal ingots Download PDF

Info

Publication number
US3875991A
US3875991A US431562A US43156274A US3875991A US 3875991 A US3875991 A US 3875991A US 431562 A US431562 A US 431562A US 43156274 A US43156274 A US 43156274A US 3875991 A US3875991 A US 3875991A
Authority
US
United States
Prior art keywords
liquid metal
arrangement
passage
mould
duct
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.)
Expired - Lifetime
Application number
US431562A
Other languages
English (en)
Inventor
Evgeny Alexeevich Korshunov
Konstantin Alexeevich Malikov
Lev Mikhailovich Axelrod
Mikhail Iosipovich Arshansky
Georgy Fedorovich Konovalov
Petr Genrikhovich Shmidt
Jury Sergeevich Prudnikov
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
KORSHUNOV EVGENY
Original Assignee
KORSHUNOV EVGENY
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority to DE2362702A priority Critical patent/DE2362702C3/de
Priority to GB31874A priority patent/GB1440687A/en
Application filed by KORSHUNOV EVGENY filed Critical KORSHUNOV EVGENY
Priority to US431562A priority patent/US3875991A/en
Priority to FR7402719A priority patent/FR2258919B1/fr
Application granted granted Critical
Publication of US3875991A publication Critical patent/US3875991A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • 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
    • B22D11/10—Supplying or treating molten metal
    • 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
    • B22D11/14—Plants for continuous casting
    • B22D11/145—Plants for continuous casting for upward casting

Definitions

  • An arrangement for conveying and batching liquid metal supplied from a receptacle into a chilled mould comprises an inlet and an outlet boxes for liquid metal and an intermediate section of the arrangement lo cated therebetween.
  • the inlet box is provided with a drive for axially moving this box, and the intermediate section has a liquid metal duct provided with induction pumps.
  • the walls of the liquid metal duct which are adjacent to the induction pumps located outside these walls, are made inwardly convex so as to project into the inerior of the passage in such a manner that the passage is of restricted cross section in the intermediate zone thereof.
  • At least one drive for developing a force in said walls to overcome the tensile stresses therein appearing under the action of the liquid metal pressure.
  • This liquid metal duct is durable and the arrangement can opcr' ate under pressure changes from 0 to 10 atm.
  • the invention relates to arrangements for conveying and batching liquid metal supplied from a receptacle into the mould in a plant for continuous or semicontinuous casting of metal ingots.
  • These plants are provided with a receptacle for liquid metal from which it is fed into a chilled mould.
  • a metal ingot, which has been formed in the chilled mould, but is not yet completely solidifed, is fed into an arragnism for secondary cooling, wherein it is finally solidified, and then into an arrangement for cutting the ingot into predetermined lengths.
  • liquid metal is normally fed into the mould through a closed liquid metal duct.
  • a method of casting metal ingots has been recently contemplated which involves the positive supply of liquid metal through a siphon arrangement from the bottom into a radially arcuated chilled mould and an intermittent drawing of an ingot upwards into an arrangement for secondary cooling under intermittent changes in the pressure of the liquid metal exerted upon the ingot skin in the mould zone.
  • the plant for carrying out the above-mentioned method comprises a receptacle for liquid metal which is positively fed through a siphon arrangement from the bottom into a radially arcuated chilled mould, the arrangement for secondary cooling being disposed above the mould in the direction of the production flow.
  • the initial formation of the ingot skin is effected under elevated pressure, and for that reason the quality of the ingot as a whole, and especially the surface finish of the ingot being cast, can be substantially better as compared to the ingots made in the plants of other types.
  • the pressure exerted upon the ingot skin is raised at regular time intervals by raising the pressure of the liquid metal in the siphon arrangement.
  • the pressure exerted upon the ingot skin in the mould zone is reduced by lowering the pressure of the liquid metal in the siphon arrangement.
  • the pressure in the siphon arrangement may be raised either by increasing the pressure ofgas above the metal in said receptacle, or by raising the pressure directly in the passage of the siphon arrangement by using induction pumps, which are now being widely used for pumping liquid metals.
  • Induction pumps are preferably used in the siphon arrangement.
  • liquid metal ducts in known induction pumps for pumping liquid metals having high melting point are not reliable in operation, and in the majority of cases these ducts comprise a thick-walled pipe of a ceramic refractory material.
  • Another not less important object of the invention is to provide an arrangement for conveying liquid metal from a receptacle into the mould in a metal casting plant which can ensure the control of liquid metal supply from said receptacle into the mould independent of the head of the liquid metal in the receptacle.
  • Still another object of the invention is to provide an arrangement which can be the most efficiently used for conveying liquid metal from a receptacle into the mould for casting ingots so as to ensure accelerated solidification of the end face of the tail portion of the ingot at the end of the casting operation, whereby a current casting operation can be completed in the plant so as to prepare it for the next casting during a short time interval.
  • an arrangement for conveying liquid metal supplied from a receptacle into a chilled mould in a plant for casting metal ingots comprising an inlet box, an intermediate section including an induction pump and a liquid metal duct having the walls defining a passage, and an outlet box, the inlet and outlet boxes having passages communicating with the passages of the liquid metal duct, wherein according to the invention each of the walls of the liquid metal duct adjacent to the inductors of the induction pump is inwardly convex so as to project into the interior of the passage, thereby restricting the cross section of the passage in the intermediate zone thereof, while the inlet box is axially movable relative to the intermediate section of the arrangement, and there is provided drive means providing this axial movement and the application of a pressure for sealing joints between the parts of the arrangement.
  • the arrangement incorporating the above-described embodiment of the liquid metal duct has sufficient strength and is not damaged under intermittent changes of the liquid metal pressure therein.
  • the above-described liquid metal duct is preferably provided with at least one drive means which develops a force compressing the convex walls of the metal duct in the transverse direction so as to prevent them from being tensioned under the action of the liquid metal pressure. and there is preferably provided a pressure exerting plate, said drive means acting upon said walls of the liquid metal duct through this plate.
  • each of said members having an integral portion for closing said passages, as well as a portion with an opening of a size about equal to that of the passage to be closed by this member.
  • sliding members can be used for batching the liquid metal and for closing the passages for liquid metal in the inlet and outlet boxes in the case of troubles in the operation of the arrangement for conveying liquid metal. as well as at the end of the casting operatron.
  • Said members in the inlet and outlet boxes are preferably made of a highly refractory electricallyand heatconductive material, and a bushing of an electrically non-conductive material is preferably mounted in the opening of each member, the size of the bore of the bushing being about equal to that of the passage with which it cooperates.
  • the use of the sliding members made of a highly refractory electricallyand heabconductive material allows on the one hand, to feed electric current thereto through chilled shoes so as to heat with this current through the sliding members the refractory lining at the input of the inlet box and at the output of the outlet box. and on the other hand, where electric current is not passed through the sliding members, and where chilled shoes are brought in contact therewith, said shoes comprising boxes having the cavity connected to a coolant source. to effect rapid freezing of the end of the ingot being cast.
  • the bushings of the sliding members made of electrically non-conductive material prevent the current leakage when it is passed through the blocks.
  • FIG. I shows a longitudinal axial section of the arrangement according to the invention for supplying liquid metal from the bottom into a radially arcuated chilled mould:
  • FIG. 2 is a longitudinal axial section of the arrange ment according to the invention for supplying liquid metal from the top into a chilled mould;
  • FIG. 3 is a partially sectional view taken along the line III-III in FIG. 2;
  • FIG. 4 is a sectional view taken along the line l /IV in FIG. I.
  • the arrangement for conveying and batching liquid metal is located under a receptacle 1 (FIG. 1) for liquid metal 2.
  • a movable inlet box 3 having a passage 4 for reception of the liquid metal being supplied is con nected to the outlet opening of the receptacle 1.
  • the movable inlet box 3 is mounted in a stationary casing 5 which is provided with a drive 6 mounted thereon and adapted to move the inlet box axially relative to a liquid metal duct 7 having a passage 8 and located in an intermediate section 9 of the arrangement.
  • the drive 6 is used to urge the inlet box 3 against the liquid metal duct 7 of the intermediate section 9 of the arrangement, and the passage 4 of the inlet box is in register with the inlet opening of the passage 8 of the liquid metal duct of the intermediate section 9 of the arrangement.
  • the outlet end of the liquid metal duct 7 is connected to a stationary outlet box 10 having a passage II for passing liquid metal, the outlet opening of the passage 8 of the liquid metal duct 7 also being in register with the inlet opening of the passage 11 ofthe outlet box 10.
  • the passages of the inlet and outlet boxes for passing liquid metal at high melting point are provided with a refractory lining. It should be noted that the passage 11 of the outlet box 10 of the arrangement for conveying liquid metal may have different constructions depending upon the direction of the metal outflow in different types of the metal casting plants.
  • the chilled mould 12 (FIG. I) in this case is mounted on the outlet box 10, and the size of the passage 11 of the outlet box 10 is selected such as to ensure that the opening be located in the internal space of the mould 12.
  • the passage ll ofthe outlet box 10 is made so as to enable the metal outlet downwards from the outlet box, a pouring ladle 13 being accommodated in the outlet box 10 for a better shaping of the metal stream.
  • Two walls of the passage 8 of the liquid metal duct 7 are made inwardly convex so as to project into the interior of the passage.
  • Flat inductors 14 of an induction pump are mounted adjacent to these walls from the outside.
  • the inductors 14 of the induction pump are accommodated in houings 15 so as to be movable relative to the liquid metal duct 7 when acted upon by drives 16.
  • the liquid metal duct 7 (FIG. 1) of the intermediate section 9 of the arrangement for conveying and batch ing liquid metal from the receptacle 1 into the mould 12 of the plant for casting metal ingots is mounted on a support 17.
  • a pressure exerting plate 18 mounted on the flat wall of the liquid metal duct 7 above is a pressure exerting plate 18 located thereabove and having a heat insulating layer 19 on the underside and provided with at least one drive means 20 which is adapted to create compressive stresses in the walls of the liquid metal duct 7 in the transverse direction through the pressure exerting plate.
  • Drive means 20 of the pressure exerting plate 18 comprises a plurality of preferably pneumatic jacks, each being pivotally secured to a housing 15 of one inductor l4 and fixed to the housing of the other inductor by means of a latch.
  • sliding members 22 Mounted in through slots 21 (FIG. l)ofthe inlet box 3 and outlet box 10 of the arrangement are sliding members 22. They are made of a highly refractory electricallyand heat-conductive material and have open ings 23 accommodating refractory bushings 24 of an electrically non-conductive material, the size of the bushing openings corresponding to the cross-sectional size of the passage 1] closed by this member.
  • Water-chilled shoes 25 having current supply buses 26 FIG. 4) are urged against the sliding members 22 from both sides.
  • the water-chilled shoes 25 are urged against the sliding members 22 by means of drives 27 which are also adapted to move the members 22 along the slot 21 to close the passage of the liquid metal duct.
  • the arrangmeent for conveying and batching liquid metal from a receptacle into the mould of a plant for casting metal ingots operates as follows.
  • the liquid metal duct 7 Prior to the beginning of the casting of a metal ingot the liquid metal duct 7 is mounted onto the support 17 (FIG. I) and the duct may be either integral or assembled of separated parts lengthwise depending upon the length.
  • the movable inlet box 3 and the stationary outlet box 10 as well as the housings accommodating the inductors 14 are at the maximum distance relative each others. This enables unobstructed installation of the liquid metal duct 7 onto the support [7, whereafter a thin layer of plastic refractory is applied to the end faces of the duct.
  • the movable inlet box 3 is axially moved by the drive 6 relative to the liquid metal duct 7, and a force is created, which should be sufficient for reliable sealing of joints between the inlet box 3, metal duct 7 and the outlet box 10.
  • the inductors 14 of the induction pump are brought closer to the liquid metal duct 7 by means of the drives 16, and the pressure exerting plate 18 is mounted onto the liquid metal duct 7 from the top, the plate being then preliminary urged against the liquid metal duct 7 by the rods of the drives 20.
  • the pneumatic jacks of the drives 20 are preliminary mounted in the operative position so as to be connected to the housing 15 of one inductor 14 through a pivotal connector and to the housing 15 of the other inuctor I4 by means of the latch.
  • the sliding members 22 are brought by the drives 27 into such a position. at which the bores of their bushings are in register with the openings of the passages in the inlet and outlet boxes of the arrangement.
  • the refractory lining is heated at the input and output end of the inlet and outlet boxes respectively by heating the sliding members 22, through which electric current of a predetermined value is passed for that purpose.
  • the liquid metal duct 7 may be heated by using a heated pattern made of an electrically conductive material, and preferably of thin steel sheet. the shape of the pattern being as similar as possible to the shape of the passage of the liquid metal duct 7 into which the pattern is to be inserted.
  • the pattern is heated by the induction method by currents induced therein using the inductors 14 of the induction pump.
  • the receptacle l containing liquid metal 2 is brought near to the arrangement for conveying and batching liquid metal prepared in the above-described manner
  • the receptacle 1 is connected to the inlet box 3 so as to eliminate any leakage of metal through the joints between the parts of the arrangement and between the latter and the receptacle.
  • the metal 2 is fed from the receptacle 1 into the arrangement for conveying it into the mould 12 upon lifting the stopper provided in the receptacle 1.
  • the metal may be fed into the mould 12 under gravity through the inlet box 3, liquid metal duct 7 and outlet box 10.
  • the induction pump is energized by supplying electric power to the inductors 14 thereof.
  • the induction pump will be used either to increase. or to reduce the rat of metal flow through the passage of the liquid metal duct 7.
  • the mould can be supplied with metal, only if the pressure of the metal in the passage of the liquid metal duct of the arrangement at the output is greater than the excessive pressure of gas over the metal meniscus in the mould.
  • the head of the liquid metal in the arrangement herein de scribed may, however, become insufficient to overcome the gas pressure over the metal meniscus.
  • the induction pump will ensure an increase in the pressure of the liquid metal in the passage of the liquid metal duct 7, whereby the conditions for unobstructed passage of metal into the mould 12 will be created.
  • the casting of metal with an intermittent drawing of the ingot from the mould 12 FIG. I) upwards involves changes in the pressure in the zone of the mould 12 at regular time intervals, and hence, the changes in pressure in the passage 8 of the liquid metal duct 7 of the arrangement for conveying the metal. as well as the intensive metal supply into the zone of the mould l2 during the accelerated drawing of an ingot 28 from the mould.
  • the end face of the tail por tion of the ingot 28 is rapidly cooled and solidified, whereby the movement of the ingot 28 upwards can be continued in the direction towards an arrangement for secondary cooling of the plant (the arrangement for secondary cooling of the plant for metal casting is not shown) without any danger of leakage of the liquid metal from the ingot 28 being cast, which is not yet solidilied.
  • the movable inlet box 3 Upon closing the output opening of the outlet box 10 and disconnection of the inductors 14 from a power supply source the movable inlet box 3 is moved away from the liquid metal duct 7, and a small residue of the liquid metal is discharged into a preliminarily prepared receptacle not shown).
  • the arrangement is reliable in operation under changes in the liquid metal pressure from 0 up to atm., and the members 22 for closing the passages for liquid metal ensure the control (batching) of the metal flow supplied for the formation of the ingot.
  • An arrangement for conveying and batching liquid metal from a receptacle into a mould for continuous or semicontinuous casting of metal ingots comprising: an axially movable inlet box having a passage for recep- 15 tion of the liquid metal from said receptacle; an intermediate section disposed downstream said inlet box in the production flow direction and including a liquid metal duct having two inwardly convex opposite walls projecting into the interior of a passage of the liquid metal duct so as to restrict the cross section of the passage in the intermediate zone thereof; induction pumps located outside each of said convex walls of said liquid metal duct and adjacent thereto; an outlet box in communication with said mould located downstream said intermediate section in the direction of the production flow; drive means providing the axial movement ofsaid inlet box and the application of a force so as to ensure the sealing of joints between said boxes and said intermediate section of the arrangement.
  • said liquid metal duct includes at least one drive means adapted to develop a force to compress in the transverse direction the convex walls of the liquid metal duct so as to prevent them from being tensioned under the action of the liquid metal pressure, and a pressure exerting plate, said drive means acting upon said walls of the liquid metal duct through said plate.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Casting Support Devices, Ladles, And Melt Control Thereby (AREA)
  • Continuous Casting (AREA)
US431562A 1974-01-07 1974-01-07 Arrangement for conveying and batching liquid metal supplied from a receptacle into a mould for continuous casting of metal ingots Expired - Lifetime US3875991A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
DE2362702A DE2362702C3 (de) 1974-01-07 1973-12-17 Vorrichtung zum Zuführen, Fördern und Dosieren einer Metallschmelze zu einer Stranggießkokille
GB31874A GB1440687A (en) 1974-01-07 1974-01-03 Apparatus for conveying liquid metal
US431562A US3875991A (en) 1974-01-07 1974-01-07 Arrangement for conveying and batching liquid metal supplied from a receptacle into a mould for continuous casting of metal ingots
FR7402719A FR2258919B1 (de) 1974-01-07 1974-01-28

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US431562A US3875991A (en) 1974-01-07 1974-01-07 Arrangement for conveying and batching liquid metal supplied from a receptacle into a mould for continuous casting of metal ingots

Publications (1)

Publication Number Publication Date
US3875991A true US3875991A (en) 1975-04-08

Family

ID=23712485

Family Applications (1)

Application Number Title Priority Date Filing Date
US431562A Expired - Lifetime US3875991A (en) 1974-01-07 1974-01-07 Arrangement for conveying and batching liquid metal supplied from a receptacle into a mould for continuous casting of metal ingots

Country Status (4)

Country Link
US (1) US3875991A (de)
DE (1) DE2362702C3 (de)
FR (1) FR2258919B1 (de)
GB (1) GB1440687A (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4566859A (en) * 1983-06-20 1986-01-28 Interatom Internationale Atomreaktorbau Gmbh Method for carrying liquid metal by two series-connected electric magnet pumps
FR2751249A1 (fr) * 1996-07-17 1998-01-23 Pont A Mousson Dispositif de positionnement d'un bloc-filiere d'une table de coulee d'une machine de coulee continue verticale ascendante
CN101468385B (zh) * 2007-12-29 2010-11-24 中国船舶重工集团公司第七二五研究所 一种可用来制取金属粉末及铸件的金属液联动输送装置

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2419781A1 (fr) * 1978-03-17 1979-10-12 Perie Rene Machine de coulee continue pour tubes
US4635705A (en) * 1983-12-14 1987-01-13 Westinghouse Electric Corp. Double-sided electromagnetic pump with controllable normal force for rapid solidification of liquid metals
FR2705259B1 (fr) * 1993-05-19 1995-07-07 Pont A Mousson Dispositif d'alimentation en métal en fusion, notamment en fonte, d'une machine de coulée, et installation de coulée intégrant ce dispositif d'alimentation.
CN102914163B (zh) * 2012-11-14 2014-09-17 西南铝业（集团）有限责任公司 合金熔炼设备及其流槽

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2386369A (en) * 1942-06-15 1945-10-09 Gen Electric Co Ltd Electromagnetic pump for electrically conducting liquids
US3263283A (en) * 1962-09-04 1966-08-02 Siderurgie Fse Inst Rech Continuous casting process and apparatus
US3288069A (en) * 1962-09-07 1966-11-29 Siderurgie Fse Inst Rech Electromagnetic pumps for pumping molten metal
US3777801A (en) * 1970-08-28 1973-12-11 Gravicast Patent Gmbh Casting apparatus

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2386369A (en) * 1942-06-15 1945-10-09 Gen Electric Co Ltd Electromagnetic pump for electrically conducting liquids
US3263283A (en) * 1962-09-04 1966-08-02 Siderurgie Fse Inst Rech Continuous casting process and apparatus
US3288069A (en) * 1962-09-07 1966-11-29 Siderurgie Fse Inst Rech Electromagnetic pumps for pumping molten metal
US3777801A (en) * 1970-08-28 1973-12-11 Gravicast Patent Gmbh Casting apparatus

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4566859A (en) * 1983-06-20 1986-01-28 Interatom Internationale Atomreaktorbau Gmbh Method for carrying liquid metal by two series-connected electric magnet pumps
FR2751249A1 (fr) * 1996-07-17 1998-01-23 Pont A Mousson Dispositif de positionnement d'un bloc-filiere d'une table de coulee d'une machine de coulee continue verticale ascendante
WO1998003288A1 (fr) * 1996-07-17 1998-01-29 Pont-A-Mousson S.A. Dispositif de positionnement d'un bloc-filiere d'une table de coulee d'une machine de coulee continue verticale ascendante
US6247520B1 (en) * 1996-07-17 2001-06-19 Pont -A-Mousson S.A. Pouring table die block positioning device for an uphill vertical continuous casting machine
CN101468385B (zh) * 2007-12-29 2010-11-24 中国船舶重工集团公司第七二五研究所 一种可用来制取金属粉末及铸件的金属液联动输送装置

Also Published As

Publication number Publication date
GB1440687A (en) 1976-06-23
FR2258919B1 (de) 1977-09-23
DE2362702B2 (de) 1977-07-21
DE2362702A1 (de) 1975-06-19
FR2258919A1 (de) 1975-08-22
DE2362702C3 (de) 1978-03-09

Similar Documents

Publication Publication Date Title
US11364539B2 (en) Method and apparatus for counter-gravity mold filling
US3032841A (en) Methods and apparatus for casting metal
US3435878A (en) Method of casting metals by induction heating
US4062399A (en) Apparatus for producing directionally solidified castings
US3875991A (en) Arrangement for conveying and batching liquid metal supplied from a receptacle into a mould for continuous casting of metal ingots
US3741280A (en) Mould for the production of metal ingots
US2716790A (en) Apparatus for casting metallic articles
US3727674A (en) Low-pressure chill-casting devices
US3598175A (en) Apparatus for casting metal slabs and billets
US6598658B2 (en) Apparatus and method of forming parts
US3976118A (en) Method for casting material under pressure
US3467168A (en) Continuous casting apparatus and method including mold lubrication,heat transfer,and vibration
US20040000387A1 (en) Apparatus and method of forming parts
US2782476A (en) Apparatus for casting air foils and the like
US3653426A (en) Furnace pouring and casting system
US3450190A (en) Low pressure casting apparatus
KR101642905B1 (ko) 수직형 반연속 주조 방법
US2789328A (en) Apparatus for casting of metals
EP1640088B1 (de) Druckgiessen von Batterieklemmen
US3608623A (en) Wedge-shaped chock means for locking impression blocks of a die assembly
US3627019A (en) Method of casting a continuous series of slugs
US3506063A (en) Continuous casting
GB2103132A (en) A method and apparatus for low pressure casting of metals
US473579A (en) Ingot-mold
US4971294A (en) Induction heated sliding gate valve for vacuum melting furnace