Nec Corporation

Hitachi Metals Precision, Ltd.

Ryoji Yamamoto

Katsuhisa Ishikawa

Takayuki Tsukahara

A novel low thermal expansion cast alloy is provided. The alloy consists of, by percents by weight, 0.02 to 0.25% of C, 30.5 to 33.3% of Ni, 4.0 to 6.0% of Co, 0.005 to 0.70% of Mn, 0.005-0.50% of Si and the balance substantially of Fe, with the proviso that % C.gtoreq.3.0285-0.0936 x % Ni (% C and % Ni are weight % of C and Ni). By such composition, micro-segregation of Ni can be reduced and the Ni content range showing the low thermal expansion coefficient can be broadened to an extent of substantially enabling mass production by a casting process in place of the conventional forging or rolling process. The average thermal expansion coefficient at the temperature range from - 50 to 120.degree. C. of the cast alloy is not more than 1.5.times.10.sup.-6 /.degree.C.

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Shimane, Japan

Ryoji Yamamoto