HIGH STRENGTH LINEPIPE STEEL PLATE FOR LARGE DIAMETER PIPE WITH HIGH HIC RESISTANCE AT THE H2S CONTAINING ENVIRONMENT AND MANUFACTURING METHOD THEREOF

摘要

A linepipe steel plate having high strength and large diameter and a manufacturing method thereof are provided to improve HIC(hydrogen induced cracking) resistance of a linepipe steel plate by optimizing components, rolling condition, and accelerated cooling condition of the linepipe steel plate. A linepipe steel plate having high strength and large diameter comprises 0.02~0.06 weight% of C, 0.1~0.4 weight% of Si, 0.8~1.5 weight% of Mn, 0.05~0.4 weight% of Ni, 0.05~0.4 weight% of Cu, 0.005~0.1 weight% of Al, 0.015 weight% or less of P, 0.002 weight% or less of S, 0.0005~0.004 weight% of Ca, 0.01~0.08 weight% of Nb and 0.002~0.007 weight% of N. The linepipe steel plate further comprises at least one selected from the group consisting of 0.5 weight% or less of Cr, 0.5 weight% or less of Mo, and 0.003 weight% of B. The Ca and S satisfy the equation of 1.2Ca/S3.5.