HIGH STRENGTH STEEL SHEET EXHIBITING GOOD BURRING WORKABILITY AND EXCELLENT RESISTANCE TO SOFTENING IN HEAT-AFFECTED ZONE AND METHOD FOR PRODUCTION THEREOF

摘要

The present invention provides high burring, high strength steel sheet excellent in softening resistance of the weld heat affected zone and a method of production of the same, that is, high burring, high strength steel sheet excellent in softening resistance of the weld heat affected zone containing, by wt %, C: 0.01 to 0.1%, Si: 0.01 to 2%, Mn: 0.05 to 3%, P≦̸0.1%, S≦̸0.03%, Al: 0.005 to 1%, N: 0.0005 to 0.005%, and Ti: 0.05 to 0.5% and further containing C, S, N, Ti, Cr, and Mo in ranges satisfying 0%C−(12/48Ti−12/14N−12/32S)≦̸0.05%, Mo+Cr≧0.2%, Cr≦̸0.5%, and Mo≦̸0.5%, the balance being Fe and unavoidable impurities, wherein the microstructure comprises ferrite or ferrite and bainite.