| 摘要 |
PROBLEM TO BE SOLVED: To provide hot forged non-heat treated steel parts which can ensure excellent machinability without depending on aging treatment while ensuring high strength. SOLUTION: The hot forged non-heat treated steel parts have a chemical composition containing, by mass, 0.35 to 0.45% C, 0.40% or less Si, 0.90 to 1.40% Mn, 0.04 to 0.10% S, 1.00% or less Cr, 0.20 to 0.50% V, and the balance Fe with inevitable impurities, wherein 2Mn+5Mo+Cr<3.1; Ceq=C+Si/7+Mn/5+Cr/9+V is 0.9-1.1; the hardness is HV 340 or more; the yield ratio is 0.7 or more; and the structure is ferrite-perlite structure containing 10% or less of bainite. COPYRIGHT: (C)2010,JPO&INPIT |
