US2946101A

US2946101A - Procedure for vacuum casting and arrangement intended therefor

Info

Publication number: US2946101A
Authority: US
Inventors: Lilljekvist Bengt Ludv Fredrik; Uhrus Lars Olof
Original assignee: SKF AB
Current assignee: SKF AB
Priority date: 1957-06-01
Filing date: 1958-05-29
Publication date: 1960-07-26
Anticipated expiration: 1977-07-26
Also published as: GB846178A; BE568211A; DE1121774B; FR1196514A

Description

y 1950 B. F. LILLJEKVIST ETAL PROCEDURE FOR VACUUM CASTING AND ARRANGEMENT INTENDED THEREFOR Filed May 29, 1958 BY Mai/6 2W ATTYS.

INVENTORSZ BENGT LILLJEKVIST LARS OLOF UHRUS UQ Cd States Patent PROCEDURE FOR VACUUM CASTING AND ARRANGEMENT INTENDED THEREFOR Bengt Ludvig Fredrik Lilljekvist and Lars Olof Uhrus, both of Hofors, Sweden, assignors to Aktiebolaget Svenska Kullagerfabriken, Goteborg, Sweden, a, corporation of Sweden Filed May 29, 1958, Ser. No. 738,731

Claims priority, application Sweden June 1, 1957 7 Claims. (CI. 22-84) receptacle, usually called a recipient, is evacuated. The

molten metal passes as a jet into the ladle or ingot mould, and gaseous components will then be separated from the metal because of the prevailing vacuum. The effectiveness of the degassification is dependent on the shape of the jet. In order to obtain good degassification, it is necessary for the jet to have a large surface in relation to the fluid quantity. One way, therefore, of obtaining good degassification is to make the jet as thin as possible, which means that the casting must be carried out as slowly as possible. For practical reasons, the molten metal must not be allowed to flow through very small holes, as the metal will then solidify in the narrow passage. From a practical standpoint, it is not possible to cast steel through holes having diameters less than about 10 mm.

This invention refers to a process for vacuum casting to remove the difliculties arising from solidifications when molten metals pass through small holes, and is chiefly characterized by the fact that when the walls of the hole have been heated by the molten metal, the flow area will be reduced to the minimum area at which there is no risk for the metal to solidify.

Two designs for the procedure according to the invention are shown in Figs. 1-4, of which Figs. 1 and 2 show in vertical section two diiferent arrangements for a nozzle before casting, and Fig. 3 shows a vertical section of the same nozzle when casting has started. Finally, Fig. 4 shows a cross section through the lower part of the nozzle illustrating how the discharge duct will look.

In Figs. 1 and 2, 1 designates the top part of the nozzle and 2 the bottom part. They are made of refractory material and separated by a horizontal plane 3. In the top part 1 of the nozzle there is a circular tapered hole 4, which can be closed by a stopper 11. In the bottom part 2 there is a hole co-axial with hole 4. The upper part 5 and the lower part 6 of this hole are cylindrical and the intermediate part 7 is conical. The diameters of

cylinders

5 and 6 have a ratio of about 3:1. In the wall of the cylindrical hole 6 a slit 12, parallel with the cylinder, is recessed with a section area which is about 10% of the area of cylinder 6. In Fig. 1 a round ball 8 of refractory material is held against the cylindrical sur- 2 4 face 5 by means of a metal strip 6. The diameter of ball; 8 is somewhat larger than-that of hole 6, and thereforethe ball does not fall through the hole. In the other design, shown in Fig. 2, the ball is pressed against the cylinder wall 5 by a spring 10.

When the casting process starts the ceramic stopper 11, which rests on the top conical surface 4 of the nozzle and closes the inlet opening, is lifted so that metal flows through the nozzle. The first jet, which is rather large, will heat the walls of the duct so that solidification is thence prevented. The first metal which flows through will melt the strip 9 or spring 10, thus releasing the ball which is forced by the jet down into a lower position and pressed against the tapered surface 7. The greater part, about of the lower passage will thus be obstructed, as the metal flows only through slit 12 in the wall of hole 6. The invention is, of course, not restricted to the above designs. The flow area can be reduced in numerous ways. For instance, the stopper can be designed so that it will increase or decrease the flow area when it is moved up or down.

We claim:

1. A charging nozzle having an interior wall therein defining a flow passage through the nozzle, said nozzle having a discharge opening in communication with said flow passage and including a first portion of predetermined cross-sectional flow area and a second portion of sub stantially smaller cross-sectional flow area, a flow-restricting element within the flow passage of said nozzle engageable with said first portion of said discharge opening -to reduce the flow area through said nozzle and attenuate element from its retracted, non-restricting position for engagement with said first portion of the discharge openmg.

2. A charging nozzle according to claim 1, wherein the flow-restrictingelement comprises a spherical valve member of refractory material, wherein the nozzle includes a chamber formed in the wall defining the flow passage for housing said spherical valve member when said valve member is in its retracted, non-restricting position, and wherein the means for retaining said flow-restricting element in its retracted, non-restricting position remote from the discharge opening comprises a device suscep tible of destruction by the heat of the metal flowing through the nozzle, to thereby release said flow-restricting element from its position within said chamber for engagement with said first portion of said discharge opening.

3. A charging nozzle according to claim 1 wherein the meansfor retaining the flow restricting element in said retracted, non-restricting position consists of a device susceptible to destruction by contact with the molten metal, and located in the path of said metal flowing through the nozzle.

4. A charging nozzle according to claim 1, wherein the nozzle includes a chamber formed in the wall defining said flow passage for housing said flow restricting element and its retaining means.

5. A charging nozzle according to claim 3 wherein the device susceptible to destruction by contact with the molten metal and located in the path of said metal flowing through the nozzle consists of a spring which upon destruction releases said flow-restricting element from its retracted, non-restricting position.

6. A charging nozzle according to claim 3 wherein the device susceptible to destruction by contact with the molten metal and located in the path of said metal flowing through the nozzle consists of a clip anchored to the wall defining the flow passage, which clip upon destruction releases said flow-restricting element from its re-' tracted, non-restricting position.

7. A charging nozzle according to claim 4, wherein the nozzle comprises separable parts which, when separated, afiord acess to said chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,663,093 Peiler Mar. 20, 1928 2,243,425 Junghans May 27, 1941 10 2,312,796 Campbell Mar. 2, 1943 FOREIGN PATENTS 902,495 France Aug. 31, 1945