HIGH STRENGTH HOT ROLLED STEEL SHEET EXCELLENT IN HOLE EXPANDABILITY AND WELD ZONE FATIGUE PROPERTY AND MANUFACTURING METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To provide a high strength steel sheet having enhanced fatigue strength of a weld zone while securing hole expandability.;SOLUTION: There is provided a high strength hot rolled steel sheet containing, by mass%, C:0.02-0.15%, Si:0.01-2%, Mn:0.50-2.5%, P:0.001-0.1%, S:0.0005-0.05%, Al:0.01-0.5%, N:0.0001-0.01% and further containing 1 or 2 of Ti:0.01-0.14% and Nb:0.005-0.09% in a range satisfying following formulae (1) and (2), and having random intensity rate of {110}111 to {110}001 directions from an outermost surface layer to sheet thickness 1/6 thickness of 3.5 or less. 65≤315×[C]+40×[Mn]+11×[Si]-30×[Al]+(35×[V]+20×[Cr]+17×[Ni]+10×[Cu]+5×[Mo])≤150 (1). 0.1×[Mn]+9×[Mo]+2×[Al]≤1.1 (2).;SELECTED DRAWING: Figure 1;COPYRIGHT: (C)2018,JPO&INPIT