PURPOSE: To produce a machine structural part further improved in mechanical properties such as bearing strength, bending fatigue strength and twisting fatigue strength.
CONSTITUTION: A steel contg., by weight, 0.35 to 0.65% C, 0.03 to 1.50% Si, 0.3 to 1.0% Mn and 0.1 to 3.0% Cr, furthermore contg., at need, one or ≥two kinds among 0.01 to 1.5% Al, 0.05 to 0.5% V and 0.05 to 0.5% Mo, similarly, 0.5 to 2.0% Ni, similarly, one or two kinds of 0.005 to 0.05% Ti and 0.01 to 0.10% Nb and, similarly, one or ≥two kinds among 0.02 to 0.40% S, 0.01 to 0.50% Pb, 0.0003 to 0.010% Ca, 0.005 to 0.10% Te and 0.01 to 0.50% Bi, and the balance Fe with impuritiets is subjected to nitriding treatment at the Ac1 transformation point or above of the steel to ≤950°C, is cooled by air cooling or by using a refrigerant and is thereafter subjected to induction hardening.
NAKAMURA SADAYUKI
WATANABE YOICHI
NISSAN MOTOR