Evaporative-pattern casting

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.[1]

The two major evaporative-pattern casting processes are:[1]

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,[2] evaporative foam casting, foam vaporization casting, lost pattern casting, the castral process, and expanded polystyrene molding.[3][4] Proprietary terms included Styro-cast,[5] Foam Cast,[6] Replicast,[7] Policast.[4] and Lost Foam Sintered Shell (LFSS)[8]

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.[9][10]

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.[11]

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.[12][13]

References

  1. ^ a b Degarmo, Black & Kohser 2003, p. 321.
  2. ^ U.S. patent 4,068,704.
  3. ^ American Society for Metals et al. 1991, p. 229.
  4. ^ a b Totten, Funatani & Xie 2004, p. 357.
  5. ^ Styro-cast, retrieved 2009-03-29[permanent dead link‍].
  6. ^ American Foam Cast, retrieved 2009-03-29.
  7. ^ Replicast Process (CS), retrieved 2009-03-29.
  8. ^ "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.
  9. ^ Donahue, Raymond; Anderson, Kevin, Lost Foam Casting, ASM International, retrieved 2010-04-06.
  10. ^ U.S. patent 2,830,343
  11. ^ Biswanath, Mondal (2004), Proceedings of the National Conference on Investment Casting: NCIC 2003, Allied Publishers, ISBN 978-81-7764-659-7
  12. ^ Bodine, Jack R. (1999-05-01), "From a monument to the Vega: the journey of the aluminum casting industry", Modern Casting: 13.
  13. ^ Success through partnership: lost foam (PDF), September 1998, retrieved 2009-03-30.

Bibliography