US3514519A - Heated transfer vessel for molten metal casting apparatus and method - Google Patents

Description

May 26, 1970 E G SCHEMPP ETAL HEATED TRANSFER VESSEL FOR MOLTEN METAL CASTING APPARATUS AND METHOD 2 Sheets-Shee'z 2 Filed Feb. 8, 1968 E mm 0. W G %M sa BO y E TTORA EY United States Patent O 3,514,519 HEATED TRANSFER VESSEL FOR MOLTEN METAL CASTING APPARATUS AND METHOD Eberhard G. Schempp, Glenshaw, and Robert J. Taylo',

McKees Rocks, Pa., assignors to Lectromelt Corporation, Pittsburgh, Pa., a corporation of Delaware Filed Feb. 8, 1968, Ser. No. 703.942 Int. Cl. Hb 3/62; B22d 11/00 U.S. Cl. 13--20 12 Claims ABSTRACT OF THE DISCLOSURE A refractory lined molten metal transfer vessel having at least one upper inlet for receiving molten metal from a ladle and at least one lower nozzle for discharging molten metal into a continuous casting apparatus. Resistance heating means Supplies radiant energy to the vessel and the molten metal, and an inlet for inert gas is provided to minimize oxidation of the molten metal and the resistance heating means.

BACKGROUND OF THE INVENTION tundish. The transfer vessel has one or more nozzles at its lower end for discharging molten metal into one or more generally vertically arranged molds having an upper opening and means for continuously withdrawing the ingot from its lower end.

The various handling procedures, which occur before the molten metal is cast, include tapping of the furnace, discharging of the metal into a ladle, possible additional metallurgical treatments such as vacuum degassing, transporting the ladle to the casting apparatus, discharge of the metal into the transfer vessel and, finally, the discharge of the metal into the molds. This time lapse between tapping and teeming may result in substantial heat loss in the molten metal. Also, vari-able conditions of the ladle, of the tap, of the transfer, of the slag blanket and added processes, result in a wide range of actual temperature losses from heat to heat. In order to insure that such heat losses do not lower the melt temperature below that necessary for successful casting, excessive furnace tapping temperatures were heretofore required.

A serious chilling effect may also occur as molten metal is discharged from a ladle into a relatively cold transfer vessel. This is particularly serious since the first portion of molten met-al to enter the tundish is generally at a substantially lower temperature than the bulk of the ladle content. For example, in a ISO-ton ladle the temperature difference 'between the top and bottom layers of molten metal may be as much as 40 F.

In addition, oxidation may occur in the stream of molten metal falling into the transfer vessel frorn the ladle as well as to the surface of the molten metal as it flows to the various discharge nozzles. This contaminates the metal with hydrogen, oxygen and nonmetallic inclusions and, in addition, seriously shortens the life of the refractory and the transfer vessel.

It is an object of the invention to provide a new irnproved transfer vessel for a continuous casting apparatus.

Another object of the invention is to provide a con- "ice tinuous casting transfer vessel having means for regulating the melt temperature during -a casting operation.

A further object of the invention is to provide means to prevent the chilling of molten metal in a transfer vessel during a continuous casting operation.

Yet another object of the invention is to provide means to prevent oxidation of molten metal in a transfer vessel during a continuous casting operation.

These and other objects and advantages of the instant invention will become more apparent from the description of the preferred embodiment taken with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational View illustrating a continuous casting apparatus incorporating the instant invention;

FIG. 2 is a side elevational view, partly in section, of the transfer vessel according to the instant invention;

FIG. 3 is a top plan View of the transfer vessel illustrated in FIG. 2;

FIG. 4 is a fragmentary view of the heating rod assernbly of the transfer vessel illustrated in FIG. 2; and

FIG. 5 is a fragmentary View illustrating the heating elements clarnps useable with the transfer vessel according to the invention.

SUMMARY OF THE INVENTION A refractory lined molten metal transfer vessel having at least one molten metal inlet and at least one molten metal outlet and means for heating the molten metal and vessel during a continuous casting operation. The invention may also include means for providing an inert gas atmosphere within the vessel.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 in greater detail, the transfer vessel or tundish 10 is shown to be disposed between a ladle 11 and the mold 12 of the continuous casting apparatus. The ladle 11 is provided with a spout 14 that is normally closed `by a plug (not shown) which may be operated frorn a remote location by means which are not shown but which are well known in the art The tundish 10 may be generally pear-shaped in vertical section and include a body portion 16 and a cover portion 17. An inlet pipe 18 opens into the cover portion 17 and is disposed in registry with the ladle spout 14, and one or more discharge nozzles or ports 20 open into the lower end of the tundish body 16. Disposed below each of the discharge nozzles 20 and in general registry therewith is the mold 12 of the continuous casting operation. The continuous casting apparatus forms no part of the instant apparatus and, accordingly, Will not be discussed in detail. For purposes of understanding the instant invention, it will be suffcient to state that the mold 12 includes an inlet 21 at it s upper end and means 23 at its lower end for continuously withdrawing the ingot 24.

Referring now to FIGS. 2 and 3, the tundish body 16 is shown to comprise an elongate trough-like body having side walls 28 'which slope gently upwardly from its lower end and comprising an outer metallic shell 29 and an inner refractory lining 31 which may be composed, for example, of MgO or MgO-Cr O mixture. The discharge nozzles 20 are preferably disposed in equispaced relation along the lower end of the tundish body, and each is composed of a zirconia cast refractory which is illustrated as a single member but which may be composed of a plurality of shape members as well.

The cover 17 is substantially coextensive with the tundish body 16 comprises a metallic frame 33 for supporting a generally vertical side wall portion 34 and an arched roof 35, each of which is composed of a high alumina cast refractory material. A generally tubular inlet nozzle 37, formed of cast high alumina refractory, extends vertically through an opening 38 formed generally in the center of the arched roof 35 and extends downwardly to the lower edge of the cover 17.

A plurality of equally spaced apart heating assemblies 40 extend transversely across the cover 17 for preheating the tundish and for maintaining or elevating the melt temperature during a casting operation. The heating assemblies 40 are each received through one of a plurality of pairs of aligned openings 42 which are formed transversely in the side wall portion 34 of cover 17 wherein the heating assemblies 40 are supported in a generally parallel relation below the arched roof 35.

Each heating assembly 40 may comprise a heating rod 43 extending transversely across the cover 17 beneath the arched roof 35 and which is held in position by a pair of elongate, generally cylindrcal holders 45 which are disposed in general alignment within the apertures 42 and extend outwardly therefrom for engagement by clamp assemblies 46. As seen in FIG. 4, the rod 43 and the holders 45 may each be composed of graphite and may be joined in any suitable manner such as by an externally threaded graphite nipple member 48 which is received in threaded openings 50 and :51 suitably formed in the ends of the heating rods 43 and the holders 45, respectively.

As seen particularly in FIG. 5, the clamps 46 have a pair of opposed generally arcuate shoes 52 which are sutably held in high pressure engagement with their respective holders 45, and each clamp is suitably connected to bus bars 53 which are in turn connected to a source of electrical energy (not shown). The clamp shoes 52 and the bus bars 53 may be composed of any suitable conductive material, such as Copper, and each may be provided with means to permit the circulation of cooling fluid, such as the tubing 54 within the clamp shoes 52 and the hollow interier of the bus bars 53. Those skilled in` the art -will appreciate that the bus bars 53 will be connected to a suitable energy source. I

The roof 35 may also have one or more apertures 50 which may be provided with a nipple 56 for receiving a Conduit 57 whose other end may be connected to a suitable source of inert gas, such as nitrogen.

In operation, the heating elements 43 -will be energized prior to the beginning of a casting operation to preheat the inner surface of the refractory lining 31 to' approximately the temperature of the liquid metal to be cast. This prevents chilling of the steel as it is being discharged from the ladle into the tundish through the inlet nozzle 37. The heating assemblies 40 may also remain energized during the casting operation so that the temperature of the molten steel may be maintained at a desired level or even elevated. This insures satisfactory casting and pre- 'vents freezing of the molten metal within the discharge nozzles 20.

Those skilled in the art will appreciate that the molten metal entering the tundish will flow to each end of the tundish body 16 and discharge through each of the nozzles into a mold of the continuous casting apparatus disposed therebelo'w. In addition, a final temperature adjustment may be made during the casting operation so that the 'steel temperature may be maintained within the relatively narrow range needed for successful continuous casting, regardless of variations in the ladle, the tap, the transfer, the slag blanket at any intermediate metallurgical processes. In addition, the nonreducing nitrogen atmosphere within the tundish cover avoids oxidation of the stream falling into :the tundish and of the surface of the steel fiowing toward the nozzles. This not only prolongs refractory life, but avoids contamination of the steel by hydrogen, oxygen and nonmetallic inclusions.

While only a single 'type of heating assembly has been disclosed, this is intended to be merely illustrative, since those skilled in the art will appreciate that other types of heating assemblies may also be employed. In addition, while only a single embodiment of the instant invention has been shown and described, it is not intended to be limited thereby, but only by the scope of the appended claims.

We claim:

1. A vessel for transfer-ing molten metal from a ladle to continuous casting apparatus, said vessel comprising a hollow body portion having an open upper end and a cover portion substantially coextensive with said body portion, said body portion having at least one port for discharging molten metal to said casting apparatus, said cover having at least one port for receiving molten metal from said ladle and radiant electrical heating means supported beneath said cover for preheating said body portion and controlling the temperature of molten metal therein.

2. The vessel set forth in claim 1 wherein gas inlet means is provided in said cover so that an inert gas atmosphere may be introduced into said vessel.

3. The vessel set forth in claim 1 wherein said body portion is elongate and has a plurality of spaced discharge nozzles opening into its lower end.

4. The vessel set forth in claim 1 wherein said radiant heating means comprises electrical resistance heating elements. 4

5. The vessel set forth in claim 1 wherein said cover is composed of a refractory thermal insulating material and is generally arched.

6. The vessel set forth in claim 1 wherein said radiant heating means comprises at least one graphite heating element extending through an opening in said cover, and clamping means for supporting said graphite heating element and for connecting the same to a source of electrical energy.

7. The vessel set forth in claim 6 wherein gas inlet means is provided in said cover so that an inert gas atmosphere may be introduced into said vessel.

8. The vessel set forth in claim 7 wherein said body portion is elongate and has a plurality of spaced discharge nozzles opening into the lower end thereof.

9. The vessel set forth in claim 8 wherein said cover is composed of a refractory thermal insulating material and is generally arched to refiect radiant heat to said body portion.

10. The vessel set forth in claim 9 wherein the port in said cover is located generally at the center thereof and wherein said discharge ports are arranged vertically in substantial alignment and spaced from said entrance port, and wherein said radiant heating means comprises a plurality of graphite rod means spaced along said cover to,

substantially uniformly heat said body portion, said entrance port comprising a nozzle extending downwardly from said cover toward said body portion.

1 1. -In the method of continuously casting molten metal; the steps of introducng said metal from a ladle into a transfer vessel, heating said metal with graphite resistance heating means while in said transfer vessel, and discharging said molten metal into continuous casting apparatus from a plurality of spaced apart discharge nozzles in said transfer vessel, introducng an atmosphere of inert gas into said vessel.

12. The method set forth in claim 11 and including the step of preheating said vessel prior to the introduction of molten metal thereto from said ladle.

References Cited UNITED STATES PATENTS 2,27l,838 2/1942 Hanawalt 13-20 2,682,566 6/1954 Wahlberg 13--20 X 3,273,208 9/ 1966 Greenberger i 164--281 H. B. GILSON, Primary Examiner U.S. CI. X.R. 164-281

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