STEEL MATERIAL FOR CASE HARDENING SUPERIOR IN COLD WORKABILITY AND COARSE-PARTICLE-PREVENTING PROPERTY IN CARBURIZATION, AND MANUFACTURING METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To provide a steel material for case hardening which improves cold workability and prevents coarse particles from being produced during carburization, and to provide a manufacturing method therefor.;SOLUTION: The steel material for case hardening comprises, by mass%, 0.1-0.4% C, 0.01-1.3% Si, 0.3-1.8% Mn, 0.001-0.15% S, 0.02-0.1% Al, and 0.006-0.025% N, further one or more elements of Cr, Mo, Ni, V and Ti, or further 0.005-0.05% Nb, limited P and O contents, and the balance iron with unavoidable impurities; and has precipitates of Ti with a diameter of 0.1 μm or smaller controlled to 5/μm² or more in a matrix of a hot-rolled structure, a hardness by HV of H+30 or lower (wherein H is determined by the expression: H = 273.5 C% + 39.1 Si + 54.7 Mn% + 30.4 Cr% + 136.7 Mo% + 18.2 Ni%), and a decarbonization depth DM-T prescribed in JIS G0558 controlled to 0.2 mm or less.;COPYRIGHT: (C)2004,JPO&NCIPI