Case hardening steel, carburized component, and manufacturing method of case hardening steel

摘要

This case hardening steel has a chemical composition including, by mass %: C: 0.1 to 0.6%; Si: 0.02 to 1.5%; Mn: 0.3 to 1.8%; P: 0.025% or less; S: 0.001 to 0.15%; Al: over 0.05 to 1.0%; Ti: 0.05 to 0.2%; N: 0.01% or less; and O: 0.0025% or less, and further including, by mass %, one or more of Cr: 0.4 to 2.0%, Mo: 0.02 to 1.5%, Ni: 0.1 to 3.5%, V: 0.02 to 0.5%, and B: 0.0002 to 0.005%, and the balance consisting of iron and unavoidable impurities.

主权项

1. A case hardening steel wherein a chemical composition of the case hardening steel consists of, by mass %:
C: 0.1 to 0.6%; Si: 0.02 to 1.5%; Mn: 0.3 to 1.8%; P: 0.025% or less; S: 0.001 to 0.15%; Al: over 0.05 to 1.0%; Ti: 0.059 to 0.2%; N: 0.01% or less; O: 0.0025% or less, and one or more of Cr: 0.4 to 2.0%, Mo: 0.02 to 1.5%, Ni: 0.1 to 3.5%, V: 0.02 to 0.5%, and B: 0.0002 to 0.005%, and the balance consisting of iron and unavoidable impurities, wherein a structure of the case hardening steel is a hot-rolled structure, wherein in the hot-rolled structure, a structural fraction of a bainite is 30% or less, a ferrite grain size index is any of Nos. 8 to 11 defined in JIS G0552 dated 1998, and a maximum diameter of Ti-based precipitates in a cross-section along longitudinal direction in a matrix of the steel is 40 μm or less.