HIGH CONCENTRATION CARBURIZING AND QUENCHING METHOD OF STEEL, AND HIGH CONCENTRATION CARBURIZING AND QUENCHING PARTS

摘要

PROBLEM TO BE SOLVED: To provide a high concentration carburizing and quenching method of steel for obtaining the excellent mechanical properties such as the hardness of a surface part, ware resistance, fatigue resistance, large softening resistance by a simple treatment process at lower carburizing temperatures, and easily suppressing generation of soot, and a high concentration carburizing hardened parts appropriate for, in particular, car parts.;SOLUTION: This high concentration carburizing and quenching method includes a carbo-nitriding step for carbo-nitriding steel at the temperature of 800-880°C, and a hardening step for successively hardening the steel at the temperature higher than the carbo-nitriding temperature. In the carbo-nitriding step, network carbide is solid-solved in the austenite by setting, for example, the concentration of carbon (C) of the carburizing atmosphere to be 0.7-1.2%, and adding 3-8% ammonium gas (NH3), and when the austenite is transformed to the martensite by the hardening, the solid-solved carbide is re-precipitated, and granularly distributed in the martensite in a substantially uniform manner.;COPYRIGHT: (C)2002,JPO