High-strength steel material excellent in low-temperature strain aging impact characteristics and impact characteristics of weld heat-affected zone and its manufacturing method

摘要

The present invention relates to a steel material used as a material for pressure vessels, offshore structures and the like and, more specifically, to a high-strength steel material having excellent low-temperature strain aging impact properties and welding heat-affected zone impact properties and a method for manufacturing same, the high-strength steel material comprising 0.04-0.14 wt% of carbon (C), 0.05-0.60 wt% of silicon (Si), 0.6-1.8 wt% of manganese (Mn), 0.005-0.06 wt% of soluble aluminum (sol. Al), 0.005-0.05 wt% of niobium (Nb), 0.01 wt% or less (not including 0 wt%) of vanadium (V), 0.012-0.030 wt% of titanium (Ti), 0.01-0.4 wt% of copper (Cu), 0.01-0.6 wt% of nickel (Ni), 0.01-0.2 wt% of chromium (Cr), 0.001-0.3 wt% of molybdenum (Mo), 0.0002-0.0040 wt% of calcium (Ca), 0.006-0.012 wt% of nitrogen (N), 0.02 wt% or less (not including 0 wt%) of phosphorus (P), and 0.003 wt% or less (not including 0 wt%) of sulfur (S), with a balance of Fe and other inevitable impurities, and comprising a mixed structure of ferrite, pearlite, bainite and a martensite-austenite (MA) composite phase as a microstructure, wherein the fraction of the MA phase is 3.5% or less (not including 0%).