Claims
- 1. A method of casting a hypereutectic-aluminum silicon alloy, comprising the steps of forming a pattern from an expendable polymeric foam material having a configuration corresponding to the article to be cast, positioning the pattern in spaced relation to an outer flask, introducing an unbonded flowable sand into the flask and surrounding said pattern, said sand having a heat diffusivity greater than 1500J/m.sup.2 /.degree.K./s1/2, preparing a molten hypereutectic aluminum-silicon alloy comprising from 12% to 30% by weight of silicon, 0.4% to 5.0% by weight of magnesium, up to 0.3% by weight of manganese, up to 1.4% by weight of iron, up to 5.0% by weight of copper, and the balance aluminum, pouring said molten alloy by gravity into contact with the pattern to thereby decompose the pattern with the products of decomposition being entrapped within the interstices of the sand, solidifying the alloy to precipitate particles of primary silicon and produce a cast article, said precipitated particles of primary silicon having an average particle size less than 30 microns, and a coefficient of variation less than 50%, and removing the cast article from the flask.
- 2. The method of claim 1, wherein the sand in the flask has an AFS base permeability number of 450 to 500.
- 3. The method of claim 1, wherein the cast article comprises an engine block for an internal combustion engine.
- 4. The method of claim 1, wherein the sand is selected from the group consisting of chromite sand, silicon carbide sand, olivine sand, carbon sand, and mixtures thereof.
- 5. A method of casting an engine block for an internal combustion engine, comprising the steps of forming a pattern of an expendable polymeric foam material having a configuration of an engine block and having a plurality of cylindrical bores, supporting the pattern in a flask, introducing unbonded sand into the flask to surround said pattern and fill said bores, said sand having a heat diffusivity greater than 1500 J/m.sup.2 /.degree.K/s1/2, contacting the pattern with a molten hypereutectic aluminum-silicon alloy to thereby decompose the foam pattern with the products of decomposition being entrapped within the interstices of the sand, solidifying the alloy to produce a cast engine block containing precipitated particles of primary silicon having an average particle size of less than 30 microns, and removing the engine block from the flask.
- 6. The method of claim 5, wherein said alloy comprises 12% to 30% by weight of silicon, 0.4% to 5.0% by weight of magnesium, up to 0.3% by weight of manganese, up to 1.4% by weight of iron, up to 5.0% copper, and the balance aluminum.
- 7. The method of claim 5, wherein the precipitated particles of silicon have an average particle size less than 30 microns and the coefficient of variation of the particles is less than 50%.
Parent Case Info
This application is a continuation-in-part of application Ser. No. 07/940,485, filed Sep. 4, 1992, now abandoned.
US Referenced Citations (14)
Non-Patent Literature Citations (1)
Entry |
Metals Handbook, 9th Ed., vol. 15, p. 233, Sep. 1988. |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
940485 |
Sep 1992 |
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