"Forging Alloys
As with the cast piston, the earliest forged pistons were made with poor alloys. The same silicon-induced brittleness that makes the cast piston crack when dropped would have resulted in defects during the forging process had it been used in a forging. Consequently, during the time that the cast piston defined a piston's normal expansion rate, the forged piston was far behind the technology, and this famous for excessive expansion. The forged piston had to be fitted loose, which made it noisy and wasted power. Recently however, silicon has been introduced to the forged piston. A mixture of alloys has been found that together with silicon do not result in defective forgings. For example, nickel has been found to offset the silicon's tendency toward brittleness. However, not very much nickel can be used, as it is a heavy metal, and it affects the mixture in other ways. The result is that the modern forged piston is much more dimensionally stable than was true in the past. It's a much better product, comparable in every way to the traditional cast piston."
Cast Versus Forged Pistons
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