| 摘要 |
PROBLEM TO BE SOLVED: To produce a high strength hot rolled steel sheet having good corrosion resistance and also excellent in pore expandability (stretch-flanging properties) and to provide a method for producing it. SOLUTION: As to this producing method, a slab contg., by weight, 0.02 to 0.10% C, <=0.5% Si, 0.5 to 1.8% Mn, 0.05 to 0.10% P, <=0.005% S, 0.005 to 0.10% Al, 0.10 to 0.50% Cu, 0.10 to 0.50% Ni, 0.010 to 0.100% Ti, and the balance iron with inevitable impurities is subjected to hot rolling in which the rolling is finished at the temp. equal to or above the Ar3 transformation point and is coiled at 500 to 350 deg.C to form its metallic structure into the one consisting essentially of ferrite and bainite.
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