PROCESS FOR PRODUCING HIGH-CONCENTRATION CARBURIZED STEEL

摘要

This invention provides a process for producing a high-concentration carburized steel which can realize dispersion of a large amount of fine and spherical carbides without causing lowered service life of a furnace, deformed steel products, and lowered working efficiency. The production process comprises (i) a primary carburization step for carburizing a steel product having a predetermined composition at a primary carburization temperature (T1) (°C) until the surface carbon concentration (C) reaches a predetermined carbon concentration, (ii) a cooling step of, after the completion of the primary carburization step, cooling the steel product at a cooling rate of not less than 1°C/min to Ar1 point or less, (iii) a secondary carburization initial step of raising the temperature of the steel product to a secondary carburization start temperature (T2<SUB>s</SUB>), which is at least 100°C below the primary carburization temperature (T1), and carburizing the steel product at a secondary carburization temperature (T2), (iv) a secondary carburization late step of, subsequent to the completion of the secondary carburization initial step, raising the temperature of the steel product to a quench hardening temperature (Tq) and further carburizing the steel product at the quench hardening temperature (Tq), and (v) a quench hardening step of, after the completion of the secondary carburization late step, quench hardening the steel product.