| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a high strength hot rolled steel sheet stable for the variation in hot rolling conditions, small in the variation in strength and elongation and small in the variation in the material caused by welding heat effect. SOLUTION: In this method for producing a high strength hot rolled steel sheet in the class of 490 to 780 MPa, steel having a composition containing 0.01 to 0.1% C, <=0.05% Si, 0.1 to 2% Mn, <=0.02% P, <=0.005% S, 0.01 to 0.1% Sol.Al, 0.001 to 0.008% N and 0.01 to 0.2% Ti and satisfying 5<=(Mn/54.9)/(Ti*/47.9)<=15; Ti*=Ti-3.4×N-1.5×S is hot-rolled at the finishing temperature of Ar3 to 930 deg.C and is coiled at 500 to 650 deg.C. Further, it is possible that the content of Mn is controlled to 0.1 to 1.4%, Ti to 0.01 to 0.15%, (Mn/54.9)/(Ti*/47.9) to <=40, or further, Cr and Mo of <=1% and Nb and V of <=0.1% may be added thereto.
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