Metal founding – Process – Shaping liquid metal against a forming surface
Patent
1985-11-18
1987-05-26
Godici, Nicholas P.
Metal founding
Process
Shaping liquid metal against a forming surface
164 98, 164112, 164120, 164132, B22D 1802, B22D 1902, B22D 1914
Patent
active
046677275
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the manufacture of articles by the technique known variously as squeeze forming, squeeze casting or extrusion casting which for the sake of convenience throughout this specification and claims will be referred to as "squeeze forming". Basically the technique of squeeze forming comprises introducing liquid metal into a first part of a mould, closing the mould under pressure so that the liquid metal is displaced by the mould closure to fill a cavity within the mould without entrapping air, maintaining the metal under pressure whilst solidification takes place so as to ensure that any shrinkage cavities which may form are closed and filled, and then opening the mould and removing the formed article.
It is known to produce various squeeze formed articles, usually of aluminium or aluminium alloys, but such articles have generally been of a fiarly simple shape. Thus where a more complex shape is required it has generally been necessary to achieve such shape by some form of machining operation subsequent to manufacture of the squeeze formed article.
However, co-pending U.S. patent application Ser. No. 681,997 filed Dec. 7, 1984, now U.S. Pat. No. 4,570,693. discloses and claims a method of manufacturing a metal article by squeeze forming wherein a required shape is produced in the as-formed article which shape does not require subsequent machining. The required shape, as disclosed in the aforesaid patent application, is achieved by locating a shape compacted soluble salt core in a mould part of the squeeze forming press prior to the introduction of molten metal thereto, the core being compacted to such a density that it will have sufficient integrity to resist the pressures to which it is subjected during the squeeze forming operation and having such a surface finish as to form a corresponding surface in the squeeze formed article which will not require any subsequent machining. Specifically, the compacted soluble salt core is shaped to form a re-entrant bowl in the crown of an internal combustion engine piston.
In connection with the squeeze forming of internal combustion engine pistons produced by methods other than those disclosed in the aforesaid U.S. Pat. No. 4,570,693, it has been proposed to reinforce the crown region around the edges of the bowl. These other methods have comprised the location of a reinforcement insert in the squeeze forming press on to which the molten metal is poured so that in the as-formed piston the reinforcement insert is incorporated in the piston crown at the crown surface. The reinforcement material, which may be a solid metal block or a mat of whiskers or fibres, then has to be machined in the as-formed piston to a required shape of bowl in the finished piston.
It is an object of the present invention to provide an improved method of manufacturing an article by squeeze forming whereby a complex shape may be provided to the article without the necessity of extensive subsequent machining and wherein such shape is selectively reinforced at those areas thereof susceptible to operational requirements of reinforcement.
In accordance with the invention there is provided a method of manufacturing a light metal article by squeeze forming molten metal in a mould wherein the molten metal is introduced into the mould, the mould is closed under pressure to displace molten metal to fill a cavity in the mould and the metal is maintained under pressure whilst solidification thereof takes place, the mould subsequently being opened and the formed article removed characterised in that a required shape is formed in the squeeze formed article with reinforcement in the metal matrix of the article extending to at least part of a boundary of said shape by locating a core and a reinforcement insert adjacent said core in the mould prior to the introduction of molten metal thereto and in that the core comprises a soluble salt core compacted to such a density and surface finish that it retains its integrity under the conditions of sustained temperature and pressure transmitted the
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Barlow John
Rogers David B.
Batten, Jr. J. Reed
GKN Technology Limited
Godici Nicholas P.
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