| 摘要 |
PURPOSE:To manufacture the title wire rod having excellent wire drawability by executing rapid cooling with steam mist to a wire rod obtd. by subjecting a steel having specific compsn. to hot rolling while it is conveyed in the state of a nonconcentric ring and thereafter subjecting it to specific quenching in an off line. CONSTITUTION:A steel constituted of, by weight, <=0.20% C, <=2.0% Si, 0.05 to 2.50% Mn, <=0.015% P, <=0.015% S, <=0.005% Ti, <=0.005% Al, <=50ppm total N, 10 to 40ppm total O and the balance substantially Fe and contg. <=10mum oxide inclusions in which <=40% Al2O3 is regulated is subjected to hot rolling. The obtd. wire rod 1 is rapidly cooled by steam mist 9 from a mist nozzle 6 in the upper direction and by an air blast from the lower direction while it is conveyed on a conveyer 2 in the state of a nonconcentric ring. The steam mist 9 is generated by atomizing 0.5 to 10m<3>/min water at <=100Nm<3>/m<3> steam ratio. The cooling is executed at >=15 deg.C/sec cooling speed to convert the structure into bainite, martensite or that mixed therebetween. The wire rod 1 is then heated to Ac1 to Ac1+180 deg.C in an off line and is quenched at >=50 deg.C/sec cooling speed. |
