Patent ID: 9528172
Filing Date: 2016-12-27
CPC Classification: C21D,C22C,F16L

Claim Text:
1. A steel sheet having resistance to fracture and resistance to hydrogen-induced cracking characterized by having: a chemical composition consisting of, in mass %, C: at least 0.02% to at most 0.04%, Si: at least 0.05% to at most 0.50%, Mn: at least 1.10% to at most 1.60%, P: at most 0.015%, S: at most 0.0030%, Nb: at least 0.005% to at most 0.030%, Ti: at least 0.005% to at most 0.020%, Al: at least 0.005% to at most 0.060%, Ca: at least 0.0005% to at most 0.0060%, N: at least 0.0015% to at most 0.0070%, at least one element selected from Cu, Ni, Cr, and Mo, the at least one element or more than one element being in a total amount of greater than 0.1% to less than 1.5%, and a remainder of Fe and impurities, a steel structure comprising at least 10% by area to at most 16.5% of bainite and a remainder of ferrite and pearlite, a degree of segregation of Nb which is less than 1.60 and a degree of segregation of Mn which is less than 1.40 both at the center of the thickness of the steel sheet, a cracking area ratio of at most 5.0% when measured after immersion for 96 hours in an aqueous acetic acid solution at 25° C. with a pH of 4 which contains 5% sodium chloride and has a H a percent ductile fracture of at least 85% in a DWTT test carried out at −30° C. DWTT-SA@-30 on a steel sheet with a thickness of at least 6 mm to at most 40 mm.