HIGH-STRENGTH STEEL MATERIAL FOR POLAR REGION ENVIRONMENT HAVING EXCELLENT ANTI-FRACTURE CHARACTERISTICS AT LOW TEMPERATURES AND METHOD FOR MANUFACTURING SAME

摘要

Provided are a high-strength steel material for a polar region environment having excellent anti-fracture characteristics at low temperatures and a method for manufacturing the same. A high-strength steel material having excellent anti-fracture characteristics at low temperatures according to the present invention comprises, in terms of weight%: 0.005-0.07% of C; 0.005-0.3% of Si; 1.7-3.0% of Mn; 0.001-0.035% of Sol.Al; 0.02% or less (0% excluded) of Nb; 0.01% or less (0% excluded) of V; 0.001-0.02% of Ti; 0.01-1.0% of Cu; 0.01-2.0% of Ni; 0.01-0.5% of Cr; 0.001-0.5% of Mo; 0.0002-0.005% of Ca; 0.001-0.008% of N; 0.02% or less (0% excluded) of P; 0.003% of less (0% excluded) of S; 0.003% or less (0% excluded) of O; the remainder of Fe; and unavoidable impurities. The high-strength steel material having excellent anti-fracture characteristics at low temperatures according to the present invention satisfies relation 1 and relation 2, and the microstructure thereof comprises at least 70 area% of a total of polygonal ferrite and acicular ferrite and comprises 3.5 area% or less of MA phase (martensite-austenite composite phase).