LOW STRAIN CARBURIZED GEAR EXCELLENT IN DEDDENDUM BENDING STRENGTH AND ITS PRODUCTION

摘要

PURPOSE: To produce a low strain carburized gear excellent in deddendum bending strength and small in heat treating strains by using a steel having a specified compsn. contg. Ni, Cr, Mo, Al and B as the stock and specifying the concn. of C in the surface of a carburizing hardened layer, the grain size therein and the hardness of the core part. ;CONSTITUTION: A steel having a compsn. contg., by weight, 0.30 to 0.60% C, ≤1.5% Si, ≤2.5% Mn, ≤2.5% Ni, ≤2.0% Cr, ≤1.0% Mo, 0.01 to 0.06% Al, ≤0.0050% B and 0.0040 to 0.0200% N, furthermore contg., at need, one or more kinds among 0.010 to 0.050% Ti, 0.010 to 0.050% Nb and 0.01 to 0.30% V, and the balance Fe with inevitable impurities, and in which the contents of P and S are regulated to ≤0.03% and ≤0.03% is used as the stock to form a gear. This gear is subjected to carburizing treatment, and the concn. of C in the surface of the carburizing hardened layer is regulated to 0.5 to 1.0%, i.e., to the one more than the concn. of C in the stock. Next, the gear is gradually cooled and is thereafter subjected to induction hardening to regulate the austenite grain size in the hardened layer to JIS No.≥9 and the hardness of the core part to ≥250HV.;COPYRIGHT: (C)1996,JPO