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Malleable iron still has a niche.

A friend at General Motors recently gave me the Casting Answers & Advice article in the February issue of MODERN CASTING, and as a "malleabler," I would like to comment. I know malleable has become less popular in recent years, but I believe strongly that the material still has special properties and applications. It is important to educate people on the existence of malleable iron to stop it from completely disappearing.

I work for an iron casting facility in the Netherlands. We produce high quality parts in malleable iron and ductile iron. Our facility has produced malleable iron parts since 1934 for customers like Detroit Diesel Corp., Allison Transmission and Shanghai General Motors. Our plant took over some production of GM's closed malleable iron plant.

It was interesting to read the history behind the trade name Armasteel. But to be clear, the GM specification from August 1993 is titled Ferritic and Pearlitic (Armasteel) Malleable Iron Castings and shows the GM11M, GM86M, GM85M, GM84M and GM88M grades. The 85M mentioned in your Table 1 comes from the MS-034, a different specification.

It would have been helpful if the article had referred to the present specifications of malleable iron, the GMW1 of Oct. 2000 from GM, the ISO5922 second edition (Feb. 15, 2005) and the EN1562:1997.

Malleable iron dates back to about 1900, if you mean its application in the automotive industry. The history of the material goes back to Europe, where the French metallurgist R.A.F. de Reaumur published the first discussions of malleable iron in 1720-1722. In America, the inventor Seth Boyden introduced malleable iron. Boyden knew of the "white-heart" iron of Europe, foresaw a potential market for such a material and started a series of experiments to produce it. Because of the chemical composition of the pig iron used, Boyden found the fractures of his specimens black and gray ("black-heart"), with free carbon resulting from the heat treatment process. In 1831, he was granted the first American patent for malleable iron, and production of castings began in his New Jersey facility.

The article suggests any malleable cast iron produced with proper controls can perform like Armasteel. The phrase "proper controls" is suggestive to questions, while ductile iron needs the same or even more controls for controlling mechanical properties and soundness.

The article also says ductile iron equivalents are available for all four grades of Armasteel, and for many applications this is true. But malleable iron has the unique properties of a low silicon cast iron. Depending on how much a designer wants to compromise, malleable iron is superior to ductile for certain applications.

My friend at GM thought it was suggested GM is no longer using malleable iron; it still uses tons a day.


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Title Annotation:Letterbox
Author:van Ettinger, Cor
Publication:Modern Casting
Date:Apr 1, 2008
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