Steel for cold forging/nitriding, steel material for cold forging/nitriding, and cold-forged/nitrided component

摘要

A steel comprises, by mass percent, C: 0.10 to 0.15%, Si: not less than 0.02% and less than 0.10%, Mn: more than 0.90% and not more than 2.50%, P≦0.030%, S≦0.050%, Cr: 0.80 to 2.0%, V: 0.05 to 0.50%, Al: 0.01 to 0.07%, N≦0.0080%, O≦0.0030%, and one or more selected from Mo, Cu, Ni, Ti, Nb, Zr, Pb, Ca, Bi, Te, Se and Sb, the balance being Fe and impurities. The composition satisfies [35≦Mn/S≦200], [20≦(669.3×loge C−1959.6×loge N−6983.3)×(0.067×Mo+0.147×V)≦80], [140×Cr+125×Al+235×V≧160] and [150≦511×C+33×Mn+56×Cu+15×Ni+36×Cr+5×Mo+134×V≦200].

主权项

1. A steel for cold forging and nitriding, having a chemical composition comprising, by mass percent, C: 0.10 to 0.15%, Si: not less than 0.02% and less than 0.10%, Mn: more than 0.90% and not more than 2.50%, Cr: 0.80 to 2.0%, V: 0.05 to 0.50%, and Al: 0.01 to 0.07%, with the balance being Fe and impurities, wherein
P, S, N and O among the impurities are P: 0.030% or less, S: 0.050% or less, N: 0.0080% or less, and O: 0.0030% or less, the Fn1 expressed by the formula (1) described below is 35 to 200, the Fn2 expressed by the formula (2) described below is 20 to 80, the Fn3 expressed by the formula (3) described below is 160 or more, and the Fn4 expressed by the formula (4) described below is 150 to 200:
Fn1=Mn/S  (1);Fn2=(669.3×loge C−1959.6×loge N−6983.3)×(0.067×Mo+0.147×V)   (2);Fn3=140×Cr+125×Al+235×V  (3); andFn4=511×C+33×Mn+56×Cu+15×Ni+36×Cr+5×Mo+134×V   (4); where, each symbol C, Mn, S, Cr, Mo, V, N, Al, Cu and Ni in the above formulas (1) to (4) represents the content by mass percent of the element concerned.