HIGH STRENGTH STEEL SHEET FOR LINE PIPE WITH EXCELLENT RESISTANCE TO HYDROGEN INDUCED CRACKING PROPERTIES AND METHOD OF MANUFACTURING THE SAME

摘要

PURPOSE: A high-strength hot-rolled steel sheet with superior hydrogen-induced-cracking resistance for a line pipe and a manufacturing method thereof are provided to achieve API(American Petroleum Institute) 5L X70MS steel securing high hydrogen-induced-cracking resistance in a strong acid atmosphere by controlling the contents of C(Carbon), Nb(Niobium), and S(Sulfur). CONSTITUTION: A method for manufacturing a high-strength hot-rolled steel sheet comprises a step of hot-rolling a slab(S110) and a step of cooling and winding the hot-rolled slab(S120). The slab comprises C of 0.05-0.10wt.%, Si(Silicon) of 0.2-0.3wt.%, Mn(Manganese) of 1.4-1.6wt.%, S of 0.0015wt.% or less, Cr(Chromium) of 0.1-0.3wt.%, Ti(Titanium) of 0.1-0.3wt.%, Nb of 0.05-0.1wt.%, V(Vanadium) of 0.01-0.05wt.%, Ca(Calcium) of 0.001-0.004wt.%, and Fe(Iron) and inevitable impurities of the remaining amount.