Evaporative-pattern casting is a type of casting process that uses a pattern made from a material that will evaporate when the molten metal is poured into the molding cavity. The most common evaporative-pattern material used is polystyrene foam.
The two major evaporative-pattern casting processes are:
The main difference is that lost-foam casting uses an unbonded sand and full-mold casting uses a bonded sand (or green sand). Because this difference is quite small there is much overlap in the terminology. Non-proprietary terms that have been used to describe these processes include: cavityless casting, evaporative foam casting, foam vaporization casting, lost pattern casting, the castral process, and expanded polystyrene molding. Proprietary terms included Styro-cast, Foam Cast, Replicast, Policast. and Lost Foam Sintered Shell (LFSS)
History
The first patent for an evaporative-pattern casting process was filed in April 1956, by Harold F. Shroyer. He patented the use of foam patterns embedded in traditional green sand for metal casting. In his patent, a pattern was machined from a block of expanded polystyrene (EPS), and supported by bonded sand during pouring. This process is now known as the full mold process.
In 1964, M.C. Flemmings used unbonded sand for the process. The first North American foundry to use evaporative-pattern casting was the Robinson Foundry at Alexander City, Alabama. General Motors' first product using these processes was the 4.3 L, V-6 diesel cylinder head, which were made in 1981 at Massena, New York.
A study found in 1997 that evaporative-pattern casting processes accounted for approximately 140,000 tons of aluminium casting in the United States. The same survey forecast that evaporative-pattern casting processes would account for 29% of the aluminium, and 14% of the ferrous casting markets by 2010.
References
- ^ Degarmo, Black & Kohser 2003, p. 321.
- U.S. patent 4,068,704.
- American Society for Metals et al. 1991, p. 229.
- ^ Totten, Funatani & Xie 2004, p. 357.
- Styro-cast, retrieved 2009-03-29.
- American Foam Cast, retrieved 2009-03-29.
- Replicast Process (CS), retrieved 2009-03-29.
- "Metafore Castings Private Limited - Pioneers in Stainless Steel, Alloy Steel and SGI Castings through Lost Foam Sintered Shell Process in India". www.metaforecastings.com. Retrieved 2018-12-05.
- Donahue, Raymond; Anderson, Kevin, Lost Foam Casting, ASM International, retrieved 2010-04-06.
- U.S. patent 2,830,343
- Biswanath, Mondal (2004), Proceedings of the National Conference on Investment Casting: NCIC 2003, Allied Publishers, ISBN 978-81-7764-659-7
- Bodine, Jack R. (1999-05-01), "From a monument to the Vega: the journey of the aluminum casting industry", Modern Casting: 13.
- Success through partnership: lost foam (PDF), September 1998, retrieved 2009-03-30.
Bibliography
- American Society for Metals; Stefanescu, D M; ASM International Handbook Committee; ASM International Alloy Phase Diagram Committee (1991), ASM Handbook, vol. 15 (10th ed.), ASM International, ISBN 978-0-87170-021-6.
- Degarmo, E. Paul; Black, J T.; Kohser, Ronald A. (2003), Materials and Processes in Manufacturing (9th ed.), Wiley, ISBN 0-471-65653-4.
- Totten, George E.; Funatani, Kiyoshi; Xie, Lin (2004), Handbook of metallurgical process design (illustrated ed.), CRC Press, ISBN 978-0-8247-4106-8.
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