| 摘要 |
PROBLEM TO BE SOLVED: To provide steel having excellent in machinability, low in ductility, capable of cold dividing working, and in which the divided fracture exhibits a flat brittle fracture surface. SOLUTION: This steel is composed of a low ductility non-heat treated steel having a compsn. contg., byweight, 0.20 to 0.70% C, <=1.50% Si, 0.3 to 2.0% Mn, <=0.15% P, 0.002 to 0.2% S, <=0.2% Cu, <=0.5% Ni, 0.02 to 2.0% Cr, <=0.5% Mo, <=0.8% W, <=0.50% V, <=0.17% Nb, <=0.50% Ti and <=0.50% Zr also satisfying Ti+Zr: >0.20 to 0.50%, <=0.010% B, <0.04% Al, <=0.008% N, <=0.30% Pb, <=0.10%, Ca, Al+2N-0.04<=0% and Ti+Zr-1.2S>0%, and the balance Fe with impurities, in which the maximum diameter of Ti carbosulfide and Zr carbosulfide in the steel is regulated to <=10μm, the total amount thereof is regulated to >=0.05% by cleanliness.
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