US2734241A

US2734241A - Vacuum pouring apparatus

Info

Publication number: US2734241A
Authority: US
Publication date: 1956-02-14
Anticipated expiration: 1973-02-14

Description

Feb. 14, 1956 United StateS Patent VACUUM POURNG APPARATUS Raymond L. Southern, New Kensington, and James K. Ely, Pittsburgh, Pa., assiguors to Allegheny Ludlum Steel Corporation, Brackeuridge, Pa., a corporation of Pennsylvania Application November 22, 1954', Serial No.y 478,479

1 Claim. (Cl. 22-73) This invention relates to vacuum pouring apparatus and in particular to apparatus for vacuum Atreating molten metal as it is poured into a mold.

Recently the advantages of vacuum treating molten metal have been recognized and different complicated structures have been designed to effect such vacuum treatment. The structures for vacuum treating molten metal which are known to the industry are massive in size and expensive to produce and operate.

An object of this invention is to provide a relatively simple pouring apparatus for cooperating with a mold to permit evacuation of the mold and subject the molten metal to a vacuum treatment as the metal is poured into the evacuated mold.

A more specific object of this invention is to provide a pouring apparatus disposed to be mounted -on a moldy to effect the evacuation of the mold and subject molten metal supplied thereto to a vacuum treatment to degas the molten metal.

A further object of this invention is to provide, in a pouring apparatus disposed to be mounted on a mold, a vacuum means for effecting the evacuation of the mold and the degassing of the molten metal supplied thereto, and means for controlling the flow of the molten metal and for maintainingthe vacuum when the flow is interrupted.

Other objects of this invention will become apparent from the following description when taken in conjunction -with the accompanying drawing, the'single figure of whichis a View iii-elevation and in section of 'a vacuum pouring apparatus embodying the teachings of this invention.

Referring to the drawing, this invention is illustrated by reference to a vacuum pouring apparatus shown generally at for treating molten metal 12 as it is poured from a ladle 14 into a mold 16. The pouring apparatus shown generally at 10 is formed of two component parts, namely a tundish 18 and a vacuum chamber 20 assembled in sealed relation therewith, the unit being disposed to be seated on the upper rim of the mold 16.

ln general the tundish 18 is of usual construction, having metallic outer side walls 22 and a base 24 and being lined with a suitable refractory material 26 and having a pouring nozzle 28 of refractory material projecting downwardly through the base 24 of the tundish. In this embodiment, the tundish 18 is preferably provided with an induction coil 30 embedded in the refractory material 26 and disposed about the well 32 for holding a supply of molten metal 12, and an induction coil 34 also embedded in the refractory liner and disposed about the pouring nozzle 28. Each of the

induction coils

30 and 34 is preferably of the hollow coil type disposed to have a cooling medium, such as water, circulated therethrough for the protection of the coils, and being connected to suitable induction heating generators (not shown) to be energized thereby so as to prevent freezing of the molten metal 12 in the tundish and nozzle thereof.

In order to control the flow of molten metal 12 through the orifice 36 of the refractory nozzle 28-and to seal such orifice under predetermined conditions, the tundish 18'v is y provided with a stopper rod 38 to which is secured Aa rstopper V'40 of refractory material designed to seat in the nozzle 278 to prevent flow of the molten metal therethrough. The stopper rod 38 is protected from the molten metal 12 as by means of a plurality of sleeves42 of refractory material assembled in end to end yrelation thereabout. Theupper end of the stopper rod 38 is secured to a stopper carrier arm 44 as by means ofthe nuts 46, the stopper carrier arm 44 being secured to an end of a guide rod 48 which is disposed to be actuated by means of. an operating vlever 50 which is pivotly secured to the other end of the guide rod as at 52. The guide rod 48 is carriedl in a guide 54 which is secured as by a link 56 'to a flange Y58 carried vby the guide 54, whereby when pressure is applied to the end of the operatingV lever 50 it will be pivoted to effect an actuation of the guide rod 48. l l y The vacuum chamber 20 is preferably formed as a side wall member 60 disposed to extend downwardly from the base '24l of the tundish 18 about the nozzle 28, being secured to the base 24 to form a seal therewith as by means of a welded joint. Thevside wall member 60 preferably terminates at its lower end in a rim member 62, having a configuration and size disposed to cooperate with the upper edge V64 of a mold 16 for effecting a tight seal therewith. For this purpose thelower edge of the rim 62 and the upper edge 64 of the mold 16 are preferably formed of complementary configurations and are notched asat 66 for receiving the gasket 68 of heat resisting material therebetween whereby a vacuum tight seal is formed between the rim member 62 `andthe upper edge 64 of. the-mold 16. Since the weight of the tundish 18 and of the molten metal 12 contained therein is-to be carried by the side Wall member-60, suitable reinforcing ange members 78 areV disposed in spaced relationto each other to extend between the base 24 and the inner surface of the side wall member 60 to provide adequate support therefor. The side wall member 60 is positioned to'extend downwardly from the tundish 18 about the pouring nozzle 28, whereby the pouringnozzle 28` and the orifice -36 thereof will be aligned with thev mold: 16 when the pouring apparatus 10- is seated `insealedfrelation on 'the mold 16 In order to evacuate the chamber 20 and the mold 16 prior to the pouring of molten metal therein, and to provide for continued evacuation of the chamber 20 during the pouring and after the mold 16 has been filled, the vacuum chamber 2() is provided with a conduit 71 having a ange coupling 72 at its outer end disposed to be connected to a suitable vacuum pump (not shown). The vacuum pump should have sufficient capacity to provide a vacuum of the order of 50 microns or less in the chamber 20 and mold 16. A viewing port 74 is also provided for the vacuum chamber 20 whereby the flow of molten metal into the mold 16 may be observed and the height of the molten metal in the mold 16 can be determined so that the operator of the apparatus can stop the iiow of molten metal to the mold 16 when the metal reaches a predetermined height in the mold 16.

In operation the pouring apparatus 1G is seated on the upper edge 64 of the mold 16, and with the stopper 40 in a position to close the orifice 36 for the pouring nozzle 28, the vacuum pump (not shown) is operated to evacuate the mold 16 and the chamber 20. In practice, if a Supply of the molten metal 12 is not contained in the tundish 18 when the apparatus 10 is first positioned on the mold 16, a suitable wax or other sealing medium (not shown) may be disposed about the stopper 40 for insuring a seal between the stopper 40 and the engaged surface of the pouring nozzle 28.

With the apparatus 10 positioned as described, and a hot top 76 of suitable refractory material disposed about the upper edge of the mold 16 within the chamber 20, molten metal such as steel, ferrous and non-ferrous base metals is poured from the ladle 14 into the tundish 18. With the vacuum in the chamber Z0 and the mold 16 at a predetermined low level as determined by a gauge 78, the operating lever 50 is actuated to raise the guide rod 48 and lift the stopper 40 from its sealed engagement with the pouring nozzle 28. The molten metal 12 then flows freely through the nozzle 36 and the evacuated chamber 20 into the mold 16. As the metal ows through the evacuated chamber 20 into the evacuated mold 16 it is subjected to the vacuum treatment whereby gases such as oxygen, nitrogen and hydrogen and which are not in solution, are removed from the metal. As the mold is lled, gases are continuously removed from the metal flowing thereto and from the surface of the metal in the mold 16, and after the mold 16 is filled and the stopper 40 is actuated to a closed position to stop the tlow of molten metal to the mold 16, gases evolving from the surface of the metal in the mold 16 are also continuously removed. It is to be noted that the

induction coils

30 and 34, when energized, will prevent solidication of the molten metal 12 in the tundish when the apparatus 10 remains on the mold 16 during the solidication period of the metal in the mold 16. In practice, by Watching the rise of the level of the metal in the mold 16 by way of the viewing port 74, the llow of molten metal to the tundish 18 and from thence to the mold 16 can be so controlled that as the mold is lled, the flow from the ladle 14 is stopped so that very little if any of the molten metal 12 remains in the tundish 18 when the mold 16 is lled. The presence of the hot top 76 on the mold within the vacu urn chamber 20 controls the solidication of the metal 12 in the mold 16 so that the upper surface is the last portion to solidify and gases are removed continuously from such upper surface during the solidication period of the vacuum treated cast metal.

After the apparatus is disconnected from the vacuum pump, the apparatus 10 can be readily removed from any given mold 16 and moved to another mold as by means of lifting lugs (not shown), the only criterion being that the molds must have an upper edge for cooperating to receive the rim 62 of the vacuum chamber 20 in a sealed relation therewith.

The apparatus is relatively simple in construction, but effective in operation to degas molten metal as it is poured into a mold. A cleaner and more uniform cast ingot is obtained when the metal is vacuum treated as described, as compared to the cast ingots obtanedby normal mill practice. Since the apparatus is relatively simple in construction, it will be appreciated that it can be readily reproduced by anyone skilled in the art.

We claim:

In a vacuum pouring apparatus for degassing molten metal as it is poured into a mold, the combination comprising, a tundish for holding a supply of the molten metal, a pouring nozzle for the tundish, a stopper disposed for movement to open and close the nozzle, a wall member forming a downwardly extending chamber secured at the upper end thereof to the tundish in a sealed relation therewith about the nozzle, the wall member having a rim member at the lower end thereof having a configuration and size to seat on the mold to effect a tight joint therewith, a plurality of spaced rib members connected between the wall member and the tundish within the confines of the chamber to support the tundish and metal contained therein, communicating means connected through the wall member of the chamber for evacuating the mold and chamber when the rim member is seated on the mold, means disposed to be operated to move the stopper to an open position to permit the ow of molten metal through the evacuated chamber into the evacuated mold while continuing the evacuation thereof to degas the molten metal, said operating means also being disposed to be operated to move the stopper to close the nozzle when the mold is lled to stop the flow of molten metal thereto while permitting continued evacuation of the chamber as the metal solidities in the mold, and means disposed about the nozzle and tundish for maintaining the metal in the tundish in a molten condition.

References Cited in the le of this patent UNITED STATES PATENTS 448,945 Durfee et al. Mar. 24, 1891 2,123,659 Pike July l2, 1938 2,308,395 Smithson et al Ian. 12, 1943 2,482,257 Frei Sept. 20, 1949 2,531,556 Davis et al.` Nov. 28, 1950 FOREIGN PATENTS 2,831 Great Britain NOV` 14, 1864 669,741 Germany Jan. 3, 1939