Patent ID: 6475305
Filing Date: 2002-11-05
Classification: C22C

Abstract:
A steel product for machine structural use having a Nd-free chemical composition comprising, in mass percent, C: 0.05% to 0.43%; Si: 0.50% to 2.5%; Mn: 0.15% to 1.06%; P: not greater than 0.035%; S: over 0.080% to 0.2%; Cu: 0% to 1.5%; Ni: 0% to 2.0%; Cr: 0% to 2.0%; Mo: 0% to 1.5%; V: 0% to 0.50%; Nb: 0% to 0.1%; Ti: 0% to less than0.04%; B: 0% to 0.01%; Al: not greater than 0.04%; N: not greater than 0.015%; Bi: 0% to 0.10%; Ca: 0% to 0.05%; Pb: 0% to 0.12%; Te: 0% to 0.05%; Se: 0% to 0.5%; value of fn1 represented by equation (1) below being not less than 7.5; value of fn2 represented by equation (2) below being not less than 3.0; balance being Fe and incidental impurities; an area percentage of a ferrite phase in microstructure being 10% to 80%; and Hv hardness being 160 to 350;fn1=âˆ’23C+Si(5âˆ’2Si)âˆ’4Mn+104Sâˆ’3Crâˆ’9V+10â€ƒâ€ƒ(1) fn2=3.2C+0.8Mn+5.2S+0.5Crâˆ’120N+2.6Pb+4.1Biâˆ’0.001&agr;2+0.13&agr;â€ƒâ€ƒ(2) where an element symbol appearing in equation (1) or (2) represents the content in mass percent of the corresponding element, and &agr; represents the area percentage in % of the ferrite phase in the microstructure.