| 摘要 |
PURPOSE:To obtain inexpensively a round steel for a rod mill, etc. having excellent wear resistance by subjecting a steel contg. C and Mn at a specific rate to hot rolling and quick cooling then to hardening and tempering by making use of the heat remaining in the round steel. CONSTITUTION:A steel consisting of 0.80-1.00wt% C, 0.4-1.8% Mn, <=0.5% Si, <=0.5% Cr, <=0.5% Ni, <=0.5% Mo and the balance Fe and inevitable impurities is rolled by hot rolling at >=800 deg.C. The surface of such round steel material is forcibly cooled to decrease the surface temp. thereof to <=200 deg.C. The steel material is then allowed to cool to restore the surface temp. up to >=400 deg.C by the heat remaining in the steel material. Tempered martensite structure is formed in the surface layer part and ferrite-pearlite structure is formed in the central part by the above-mentioned method, by which the wear resistance of the hot rolled round bar is improved. |
