Method for manufacturing a high-strength hot rolled steel sheet for linepipe with superior DWTT characteristics at low temperature

摘要

The present invention relates to a method for manufacturing high strength hot rolled steel sheets for steel pipes used for construction, line pipes and offshore structures, etc. The purpose is to use Mo, Nb and Ti appropriately and to optimize the rolling manufacturing process conditions for precipitation and structure. The present invention provides a method for manufacturing a hot rolled steel sheet having excellent strength due to miniaturization and excellent cryogenic impact toughness.;The present invention for achieving the above object, by weight% C; 0.03-0.09%, Si; 0.01-0.50%, Mn; 1.2-2.0%, P; 0.01% or less, S; 0.001% or less, Ti; 0.01- Preparing a steel slab composed of 0.10%, N; 0.01% or less, Nb; 0.04-0.07%, Ni; 0.1-0.5%, Mo; 0.1-0.5%, and the remaining Fe and other unavoidable impurities; Reheating the steel slab of the composition at a heating zone temperature of 1150-1350 ° C. and then hot rolling to a finish rolling temperature of 750-850 ° C .; The present invention relates to a method for manufacturing a hot rolled steel sheet for a line pipe having a high DWTT ductile wave rate, including a step of cooling the finished hot rolled steel slab by water and winding it at a temperature of 500-600 ° C.;Line pipe, low temperature toughness, DWTT