PURPOSE: To obtain a steel for driving transmission system parts used by applying a carbon diffusing treatment and high contact fatigue strength by specifying the compsn. consisting of C, Si, Mn, P, S, Mo, Al, N, O, Cr, V and Fe.
CONSTITUTION: Steel contg., by weight, 0.05 to 0.15% C, 0.5 to 3.0% Si, 0.3 to 2.0% Mn, ≤0.030% P, 0.01 to 0.06% S, 0.1 to 1.0% Mo, 0.01 to 0.1% Al, 0.002 to 0.02% N and ≤0.01% O and furthermore contg. one or two kinds of 1.3 to 10.0% Cr and 0.5 to 5.0% V, and the balance Fe with inevitable impurities is machined. The machined material is subjected to carburizing or carbo- nitriding treatment for ≥3hr in a carburizing or carbo-nitriding atmosphere of 900 to 1050°C and 1.5 to 5.0% carbon potential. Thereafter, the material subjected to the carbon diffusing treatment is penetrated into the quenching oil of 60 to 200°C, is quenched and thereafter subjected to tempering treatment at 100 to 200°C for ≥0.5hr. Thus, the driving transmission system parts having high contact fatigue strength is obtd.
NAITO KENICHIRO
FUSADA HIDEHIKO
