Case hardening steel, method for producing same, and mechanical structural part using case hardening steel

摘要

A case hardening steel, which has excellent cold forgeability and excellent crystal grain coarsening prevention characteristics after carburization, contains, in mass %, 0.05-0.20% of C, 0.01-0.1% of Si, 0.3-0.6% of Mn, 0.03% or less of P (excluding 0%), 0.001-0.02% of S, 1.2-2.0% of Cr, 0.01-0.1% of Al, 0.010-0.10% of Ti, 0.010% or less of N (excluding 0%), and 0.0005-0.005% of B, with the balance consisting of iron and unavoidable impurities. The density of Ti-based precipitates having circle-equivalent diameters less than 20 nm in the case hardening steel is 10-100 pieces/μm2; the density of Ti-based precipitates having diameters of 20 nm or more in the case hardening steel is 1.5-10 pieces/μm2; and the case hardening steel has a Vickers hardness of 130 HV or less.

主权项

1. A steel comprising, in mass %:
C: 0.05-0.20%; Si: 0.01-0.1%; Mn: 0.3-0.6%; P: 0.03% or less, excluding 0%; S: 0.001-0.02%; Cr: 1.2-2.0%; Al: 0.01-0.1%; Ti: 0.010-0.10%; N: 0.010% or less, excluding 0%; and B: 0.0005-0.005%, with a balance comprising iron and unavoidable impurities, wherein a density of Ti-based precipitates having a circle-equivalent diameter of less than 20 nm is 10-100 pieces/μm2, a density of Ti-based precipitates having a circle-equivalent diameter of 20 nm or more is 1.5-10 pieces/μm2, and a Vickers hardness is 130 HV or less.