Production manner null of the non quality check steel sheet where full house thermal welding HAZ tenacity

摘要

PURPOSE:To improve the toughness in a weld-heat affected zone and that of a steel itself by heating a slab having specified content of Si, Mn and A2 and specifying the conditions of its surface temp. and finish rolling. CONSTITUTION:A steel constituted of, by weight, 0.02 to 0.06% C, =0.70% Si, 0.50 to 1.60% Mn, 0.010 to 0.060% Al, 0.005 to 0.012% Ti, 0.0020 to 0.0O50% N, 0.0005 to 0.00l5% B and the balance Fe with inevitable impurities is cast. Furthermore, each component to be contained is regulated so as to satisfy the conditions expressed by the inequality. This slab is heated to 1000 to 1250 deg.C. Next, the slab is subjected to finish rolling of =60% in such a manner that the surface temp. determined by the following conditions lies in the range of 760 to A deg.C: when the finishing sheet thickness (mm) is 16mm, A deg.C=900-(50/8)X the finishing sheet thickness, and when the finishing temp. is =16mm, A deg.C=800. In this way, the non-heat treated steel sheet for welding structures having stable toughness can be obtd.