| 摘要 |
PROBLEM TO BE SOLVED: To provide a hot rolled steel sheet which has excellent flash and upset weldabilities so as to obtain weld zone strength for preventing the occurrence of a weld zone fracture in a production line, and to provide a high workability, high tensile strength cold rolled steel sheet produced from the hot rolled steel sheet as the stock. SOLUTION: The hot rolled steel sheet having excellent weldability comprises, by mass, 0.05 to 0.2% C,≤2.0% Si, 0.5 to 3.5% Mn,≤0.1% P,≤0.02% S, 0.01 to 2.0% Al and≤0.007% N, and the balance substantially Fe with inevitable impurities. The number of inclusions with a diameter of 0.1 to 1.0μm included in the steel sheet is≤2,000 pieces/mm<SP>2</SP>, and the number of inclusions with a diameter of >1.0μm is≤[3.9-(Si+Al)]×100 pieces/mm<SP>2</SP>. The hot rolled steel sheet is subjected to flash welding or upset welding, and thereafter subjected to cold rolling to produce a cold rolled steel sheet. COPYRIGHT: (C)2003,JPO
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