METHOD FOR CARBURIZING HEAT TREATMENT OF HIGH STRENGTH GEAR SMALL IN STRAIN AND THE GEAR

摘要

PURPOSE: To obtain a gear high in fatigue strength and small in strain at the time of hardening as well as low in noise by subjecting the surface of a gear using a low alloy steel having a specified compsn. as stock to carburizing treatment, thereafter subjecting it to heat treatment under specified conditions and subsequently executing hardening and tempering. ;CONSTITUTION: A low alloy steel having a compsn. contg., by weight, 0.1 to 0.3% C, 0.15% Si, 0.30 to 1.50% Mn, 0.30 to 1.5% Cr and one or more kinds among 0.05 to 0.20% V, 0.02 to 0.20% Nb and 0.01 to 0.20% Ti is used as stock and is worked into a gear. The surface layer part of the gear is subjected to carburizing treatment. After that, it is held to the temp. range of the Ar₁ transformation point to the Ar₃ transformation point of the steel at the inside of the noncarburized part for 5min to 2hr and is subjected to oil hardening or salt bath hardening in a state in which the compsn. of the surface of the gear is held to austenite, and successively, tempering treatment is executed at 130 to 200°C. The gear whose internal structure is constituted of 30 to 50% martensite and the balance ferrite and pearlite and having the excellent property of being extremely small in strain at the time of hardening can be manufactured.;COPYRIGHT: (C)1993,JPO&Japio