| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a rolled steel bar or wire rod for hot forging, which has high bending fatigue strength, contact fatigue strength and machinability, and in which heat treatment strain can be reduced. <P>SOLUTION: The rolled steel bar or wire rod for hot forging comprises, by mass%, 0.10 to 0.25% C, 0.01 to 0.10% Si, 0.50 to 1.00% Mn, 0.003 to 0.050% S, 1.60 to 2.00% Cr,≤0.10% (including 0%) Mo, 0.025 to 0.050% Al, 0.0100 to 0.0250% N, and the balance being Fe and impurities, and fn defined by formula (1): fn=Cr+2×Mo is 1.82 to 2.10. Further, the differential value between the maximum value and the minimum value is≤10 in Ms values defined by formula (2): Ms=550-361×C-39×Mn-20×Cr-5×Mo at a plurality of measurement positions C1-C17 in the cross-section CS of the steel bar or wire rod having a radius R. <P>COPYRIGHT: (C)2013,JPO&INPIT</p> |
