Patent ID: 6866724

Claim:
A steel bar or wire rod for cold forging excellent in ductility after spheroidizing annealing, characterized by: consisting of a steel containing, in mass, 0.1 to 0.6% of C, 0.01 to 0.5% of Si, 0.2 to 1.7% of Mn, 0.001 to 0.15% of S, 0.015 to 0.05% of Al and 0.003 to 0.025% of N, and having the contents of P and O controlled to 0.035% or less and 0.003% or less, respectively, with the balance consisting of Fe and unavoidable impurities; the area percentage of ferrite in the metallographic structure of the portion from the surface to the depth of 0.15 of its radius being 10% or less, with the rest of the structure consisting substantially of one or mote of martensite, bainite and pearlite; and the average hardness of the portion from the depth of 0.5 of its radius to the center being lower than that of its surface layer (the portion from, the surface to the depth of 0.15 of the radius) by HV 20 or more.