450MPa TS 450MPA GRADE HEAVY GUAGE STEEL SHEET HAVING EXCELLENT RESISTANCE TO HYDROGEN INDUCED CRACKING AND METHOD OF MANUFACTURING THE SAME

摘要

The present invention relates to a tensile strength 450 MPa grade heavy gauge steel sheet having excellent resistance to hydrogen induced cracking and a manufacturing method thereof by optimizing composition, microstructure, and methods of rolling, cooling, and heat treatment of steel. The heavy gauge steel sheet of the present invention includes C: 0.03~0.06 wt%, Si: 0.2~0.4 wt%, Mn: 1.0~1.6 wt%, P: 0.03 wt% or less, S: 0.003 wt% or less, Al: 0.06 wt% or less, N: 0.01 wt% or less, Cu: 0.05~0.4 wt%, Ni: 0.05~0.5 wt%, and Ca: 0.0005~0.003 wt%. In addition, the heavy gauge steel sheet has a composition including remnant Fe and unavoidable impurities; and a thickness of 40 mm or more and a tensile strength of 450 MPa or more.