Manufacturing method of high strength steel sheet having excellent low temperature impact toughness

摘要

The present invention relates to a method of manufacturing high tensile strength steel used as a material for shipbuilding and sea structure, and its purpose is 50 kg / mm2 high tensile strength steel with excellent tensile strength at low temperature (-40 ℃) through recrystallization controlled rolling (RCR). To provide a method for producing a. The present invention is a method of manufacturing a tensile strength 50kg / mm2 high-tensile strength steel sheet, by weight% C: 0.09-0.16%, Si: 0.10-0.50%, Mn: 0.90-1.60%, P: 0.020% or less, S: Steel slab containing 0.010% or less, Al: 0.015-0.050%, Ti: 0.005-0.150%, N: 20-60 ppm, weight ratio of Ti / N: 3.0-3.4, remaining Fe and other unavoidable impurities was 1150-1250 ° C. After heating at a temperature of, the final rolling was carried out in a recrystallization temperature range of 950-1030 ° C. by adding 20-3-% of loading per rolling pass, and then accelerated to a temperature range of 550-610 ° C. at a rate of 7-15 ° C./sec. The technical gist of the present invention relates to a method for manufacturing a high tensile strength steel sheet having excellent low temperature impact toughness including cooling.