Nissan Motor Company Limited

Daido Steel Co., Ltd.

Atsumi Hatano

Takashi Matsumoto

Sadayuki Nakamura

Yoshio Okada

Makoto Yoshida

A steel for gears consists essentially of 0.10-0.30 wt % of C, not more than 1.0 wt % of Si, not more than 1.0 wt % of Mn, 1.50-5.0 wt % of Cr, and balance including iron and impurity. A gear made by the steel forms a hardened surface layer by carbonizing-hardening-tempering or carbonitriding-hardening-tempering. The amount of C at the hardened surface layer is within a range 0.7 to 1.3 wt %, and the amounts of C, Si and Cr satisfies a relationship 5.5&lt;3.times.C (wt %)+5.2.times.Si (wt %)+Cr (wt %). Therefore, the gear performs superior pitting-resistance and wear-resistance.

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Komaki, Japan

Atsumi Hatano