STEEL MATERIAL HAVING EXCELLENT STRAIN-AGING IMPACT TOUGHNESS AT EXTREMELY LOW TEMPERATURES AND METHOD OF MANUFACTURING SAME

摘要

One embodiment of the present invention provides a steel material having excellent strain-aging impact toughness at extremely low temperatures and a method of manufacturing same, wherein the steel material comprises, in wt%: 0.05-0.08% of C; 0.4-1.0% of Mn; 3-5% of Ni; 50 ppm or less of P; 10 ppm or less of S; and the balance of Fe and other inevitable impurities, and comprises one or more types from tempered bainite and tempered martensite as a microstructure, wherein the average concentration of carbon in the matrix of the microstructure is 0.04% or less, and the grain size having a high boundary angle of 15° or more, as measured by EBSD on surfaces, is 10 µm or less.