| 摘要 |
A machine structural steel product which comprises, in mass %, 0.05 to 0.55 % of C, 0.50 to 2.5 % of Si, 0.01 to 2.00 % of Mn, 0.035 % or less of P, 0.005 to 0.2 % of S and 0.150 % or less of N, and optionally further comprise one or more of Cu, Ni, Cr, Mo, V, Nb, Ti, B, Al, Bi, Ca, Pb, Te, Nd and Se, with the proviso that its chemical composition satisfies the formulae: -23C+Si (5-2Si)-4Mn+104S-3Cr-9V+10 >= 0 and 3.2C+0.8Mn+5.2S+0.5Cr-120N+2.6Pb+4.1Bi-0.001.alpha.2+0.13.alpha. >= 3.0, the balance being Fe and impurities, contains ferrite phase in an amount of 10 to 80 % in the structure thereof, and has a Hv hardness of 160 to 350, wherein .alpha. represents an area ratio of ferrite phase in the structure in terms of %; and structural parts for a machine manufactured from the steel product. The steel product and the structural parts are much excellent in machinability, particularly with respect to "drill life" and "disposability of chips" in drilling. The structural parts can be manufactured with relative ease through machining from the above steel product.
|
