PROCESS FOR PRODUCING HIGH-STRENGTH STEEL PLATE FOR WELDED STRUCTURE

摘要

A process for efficiently producing a steel plate for welded structures that has excellent matrix toughness and HAZ toughness is provided in which Ti is positively utilized for structural control. An ingot having a composition which has C, Mn, Nb, Ti, and N contents that satisfy given requirements is heated under given conditions and subjected to rough rolling so that each rolling pass satisfies given requirements concerning rolling temperature, draft, and interval between passes, and is subsequently subjected to accelerated cooling at an average rate of cooling in the plate-thickness direction of 5 ºC/s or more. It is preferable that after the rough rolling and before the accelerated cooling, finish rolling should be conducted so that each rolling pass satisfies given requirements concerning rolling temperature, draft, and cumulative draft. After the accelerated cooling, heat treatment may be conducted. Water cooling may be conducted between passes of the rough rolling or of the finish rolling, after the rough rolling, or before the finish rolling.