Is superior in machinability the high intensity high Characteristic quality check steel

摘要

PROBLEM TO BE SOLVED: To provide a steel product having extremely superior balance between strength and toughness, excellent in machinability at respective strength levels after hardening and tempering, and suitably used as a stock for parts for machine structural use, etc. ;SOLUTION: This steel product has a composition consisting of, by weight, 0.1-0.6% C, 0.05-1.5% Si, 0.4-2.0% Mn, 0.002-0.2% S, 0.04-1.0% Ti, 0.005-0.05% Al, ≤0.008% N, 0-2.0% Cr, 0-0.3% V, 0-0.05% Nb, 0-0.5% Mo, 0-1.0% Cu, 0-2.0% Ni, 0-0.02% B, 0-0.1% Nd, 0-0.50% Pb, 0-0.01% Ca, 0-0.5% Se, 0-0.05% Te, 0-0.4% Bi, and the balance Fe with inevitable impurities and satisfying Ti(%)/S(%)≥2. Further, this steel product has a structure where martensite comprises ≥50% and the grain size of old austenite grains is regulated to JIS grain size number 5 or above.;COPYRIGHT: (C)1998,JPO