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 0.80W1.00wt% C, 0.4W1.8% 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°C. The surface of such round steel material is forcibly cooled to decrease the surface temp. thereof to ≤200°C. The steel material is then allowed to cool to restore the surface temp. up to ≥400°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.
NISHINO JIYUNJI
HARADA TAKEO
SAKAGUCHI SATOSHI
TAKAHASHI TAKESHI
