| 摘要 |
PCT No. PCT/JP96/00805 Sec. 371 Date Mar. 19, 1997 Sec. 102(e) Date Mar. 19, 1997 PCT Filed Mar. 27, 1996 PCT Pub. No. WO96/30555 PCT Pub. Date Oct. 3, 1996The cold rolled steel sheet or galvanized steel sheet comprises by weight C: 0.0001 to 0.0026%, Si: not more than 1.2%, Mn: 0.03 to 3.0%, P: 0.015 to 0.15%, S: 0.0010 to 0.020%, Al: 0.005 to 0.1%, N: 0.0005 to 0.0080% and B: 0.0003 to 0.0030% with the balance consisting of Fe and unavoidable impurities. A process for producing the above steel sheet is also provided which comprises the steps of: performing hot roll finishing of a slab having the above chemical composition at the Ar3 transformation point or above; preferably, then cooling the hot rolled strip, within 1.5 sec after the completion of the hot rolling, to 750 DEG C. at a rate of not less than 50 DEG C./sec; coiling the strip in the temperature range of from room temperature to 750 DEG C.; cold rolling the coiled strip a reduction ratio of not less than 70%; subjecting the cold rolled strip to continuous annealing at 600 DEG to 900 DEG C. or to continuous galvanizing by the sendzimer method; and performing temper rolling with a reduction ratio of not less than 1.5x(1-400xC) % and not less than 2080x(C - 0.0015) wherein C represents the carbon content in % by weight.
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