US2218781A - Method of casting one metal upon another - Google Patents

Description

Patented Oct. 22, 19

PATENT OFFICE METHOD OF CASTING ONE LIETAL UPON ANOTHER Henry T. Baggett, Houston, Tex., assignor to Hughes Tool Company, Houston, Tex a cori poration of Delaware No Drawing. Application February 27, 1940,

.Serial No. 321,035

2 Claims. 7 (01. 22-204) My invention relates to casting a layer of metal upon another metallic object. It ,is employed particularly in forming a hard facing layer upon a steel tool.

In forming a hard abrasion resisting surface upon a steel pin, bushing and the like, by castlng, some difficulty has been experienced in bonding' the two metals together. Oxidation alon the surface of the tool to be hard faced prevents or interferes with the securing of an integral attachment of one metal upon the other and a poor job results. The air included in the furnace tends to form oxides upon t e tto1 when hot, particularly where an oxidizing atmosphere in the furnace is employed.

It is an object of the invention to provide means of obtaining a reducing atmosphere directly adiacent the point of application of the hard facing material to the work, thereby assuring a firm a bond between the two metals.

I aim to prevent oxidation both of the metal being cast and of the metal on to which the cast is being made.

My invention consists of the use of reducin v gases obtained by the action of heat upon materials in the sand of the mold at points closely adjacent the metal being cast. I mix with the sand of the mold a carbonaceous material from which carbon monoxide and carbon dioxide will be released through the heat of the furnace. The

is placed in the mold thus treated with carbonaceous materials .with a space thereabout to receive the hard facing material such, for example as stellite. The said hard material is then placed in a chamber above the mold and the mold and chamber capped in by a layer of sand. The hard material has a fusing point somewhat lower than that of the pin. The carbonaceous material in the sand may be barium carbonate, charcoal. coke, or some organic compound such as linseed oil. These materials are mixed in the sand of the mold and when the bearing and pin together with the charge of hard material are in place, the molds are placed in the furnace. As the furnace heats up to the fusing temperatures of the hard material, the sand will release the carbonaceous gases such as CO. These gases prevent access of the oxygen to the metallic surfaces of the molten metal and the metallic object upon' which it is cast. Thus there is no formation of oxides on the metal .to prevent a firm bond between the metals. Therefore the casting operation becomu Y metal object, such for example as a bearing pin uniformly reliable and the molten metal attaches itself integrally upon the surface of the pin. When the heat has. been applied sufliciently to melt the charge of hard material, this molten metal will run by gravity downwardly into the. 5 recess about the pin and will attach itselfto the surface of the pin. Due to the heat of the furnace, the outer surface of the pin reaches a sweating condition, so that the molten metal attaches and adheres'thereto" forming an integral bond. v 10 The process of casting the hard surfacing material upon the pinis both time-saving and laborsaving, as compared with common methods of welding. By my method the results are uni- 5 formly -good and superior to the results obtained -by welding and the operation is materially expedited. Also, a large number of molds will be simultaneously placed in the furnace and acted upon to perform the hard facing operation, thus further cheapening the process. 20

What I claim as new is:

1. In forming a hard surfacing p n a metal object, the steps of forming a mold about the object by mixing with the sand of the mold a carbonaceous material adapted to release carbon monoxide by the action of heat, packing the mold material about said object, leaving a space adiacent to said object to receive said surfacing material, placing hard material above said mold, enclosing said object and hard material about with sand, heating said mold inafurnace to a temperature above the fusing point of said hard material but below the fusing point of said object, whereby the heat of said furnace will melt said hard material, causing it to flow by gravity into 35 said space, and said carbonaceous material will release carbon monoxide and prevent forming of oxides. Y

2. The process of casting a hard metal surfacing of comparatively low melting point upon a 40 tool of higher melting point comprising, forming about said tool a mold of sand impregnated with carbonaceous material adapted to release carbon monoxide by the action of heat. forming a space in said mold adjacent said tool to receive. said hard metal, placing piecw of said hard metal above said space, enclosing said mold about said object andhard metal, placing said mold in a furnace and meltingsaidhardmetalinthepresence of gasarisingfromlaidcarbonaceousmamax 1 34mm.