Metal founding – Process – Shaping liquid metal against a forming surface
Patent
1985-02-27
1987-01-13
Lin, Kuang Y.
Metal founding
Process
Shaping liquid metal against a forming surface
164103, B22D 1900
Patent
active
046357017
DESCRIPTION:
BRIEF SUMMARY
The invention relates to composite metal articles. The invention particularly relates to articles of two different metals securely bonded together, with one metal protecting the other in a manner required for a particular application.
A wide variety of procedures has been proposed for providing composite metal articles to enable use of desirable properties of two dissimilar metals. Thus, articles of a metal of low corrosion resistance frequently are protected by hard-facing or cladding with a wear or corrosion resistant metal such as stainless steel. Alternatively, tough but readily machinable metals can be similarly protected by application of a material which provides in a composite article the required wear resistance. In the latter case, the tough metal supports and retains a relatively brittle abrasion resistant material which may fracture under impact loading, while also enabling machining and fixing of the composite article in a manner possible only with difficulty for an article of abrasion resistant material alone.
Hardfacing by weld deposition of metal to provide a composite article, while widely used, is relatively slow, labour intensive, relatively costly and subject to a number of practical limitations. However, recourse to hardfacing is necessary in many applications because of the lack of an economic and/or practical alternative. A variety of alternative proposals is set out in U.K. patent specifications Nos. 888404, 928928, 977207, 1053913, 1152370, 1247197 and 2044646 and in U.S. Pat. Nos. 3,279,006 and 3,342,564.
U.K. Pat. No. 888404 proposes a process for clad steel products, such as of mild or low alloy steel and a stainless steel, clad by casting a melt of one of the steels around a solid of the other steel. The solid other metal is mechanically or chemically cleaned prior to the casting process, while casting is performed under a substantial vacuum. However, it is made clear that no complete bond is made merely by the casting process. The composite article thus has to be hot-rolled to weld the two steels together; the bonding being effected by the hot rolling. The process thus suffers from the disadvantages of having to be performed under vacuum, a procedure not well suited to many production situations; while the need for hot rolling limits the choice of materials with which the process can be applied, as well as the form of the resultant composite article.
U.K. Pat. No. 928928 is concerned with liners for grinding mills, and points out the problems resulting from making the liner solely from an abrasion resistant material such as carbidic cast iron, either unalloyed, or an alloyed cast iron such as nickel-chromium white cast iron. It thus proposes a composite liner of such material and a backing of a softer and tougher metal or alloy, produced by a double casting operation in which a first metal is cast, and the second metal is cast against the first metal. Evidently cognizant of the difficulty of achieving a bond between a solid and a cast metal, and being unable with a brittle cast iron to have recourse to hot rolling to overcome this difficulty, U.K. Pat. No. 928928 teaches that the first metal, typically the carbidic cast iron, is only partially solidified when the second metal is cast against it.
U.K. Pat. No. 928928 recognises the adverse consequences of oxidation of the surface of the first metal against which the second metal is to be cast. For this purpose, a chill mould is used to achieve rapid cooling of the first metal to its partially solidified condition. However, to further offset oxidation, a flux can be used to protect that surface; the flux being present in the mould before pouring the first metal or added in liquid form with the first metal.
Due to the backing being cast in the proposal of U.K. Pat. No. 928928, its properties will be inferior to those of a wrought backing. Also, the need for the first metal to be only partially solidified when casting the second metal provides a substantial constraint. Thus, close temperature control is imperative due to rapid coo
REFERENCES:
patent: 39531 (1863-08-01), Savary et al.
patent: 2235199 (1941-03-01), Chace
patent: 2881491 (1959-04-01), Jominy et al.
English Translation of U.S.S.R., 558,754.
Arnold Brian K.
Aspin Ronald E.
Bosworth Michael R.
Heijkoop Teunis
Henderson Ian D.
Lin Kuang Y.
Vida-Weld Pty. Limited
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