| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of manufacture of a hot rolled steel plate with high workability and high strength, excellent in corrosion resistance and free from working crack due to central segregation at the time of continuous casting. SOLUTION: A slab of a carbon steel, which has a composition consisting of, by weight, 0.02-0.08% C, 1.0-2.0% Mn, 0.04-0.10% P, <=1.5% Si, <=0.005% S, 0.005-0.100% sol.Al, 0.10-0.60% Cu, 0.05-0.60% Ni, <=0.60% Cr, <=0.005% N, Ti by an amount in the range satisfying 0.04<=Ti%-(48/14×N%-48/32×S%)<=0.10, and the balance iron with inevitable impurities and satisfying inequality 0.5×C%+Mn%+10×P%<=2.6, is cast continuously while applying central segregation reducing treatment, hot-rolled at a finishing temp. in the range between the Ar3 transformation point and (Ar3 transformation point + 100) deg.C, and cooled successively down to <=500 deg.C at >=25 deg.C/sec cooling rate. The resultant steel plate is coiled at a temp. in the range between 300 and T deg.C, where T satisfies T=500 deg.C in the case of 0.04<=P<0.05% and T=(550-1000×P%) deg.C in the case of 0.05%<=P<=0.10%.
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