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

摘要

The present invention relates to a steel material having excellent strain aging impact toughness at cryogenic temperatures and a method for manufacturing the same. In one embodiment of the present invention, by weight%, C: 0.05 to 0.08%, Mn: 0.4 to 1.0%, Ni: 3-5%, P: 50 ppm or less, S: 10 ppm or less, the balance Fe and other unavoidable impurities and, the microstructure includes at least one of tempered bainite and tempered martensite, and the average C concentration in the matrix of the microstructure is 0.04% or less, and 15° or more measured by EBSD on the surface Provided are a steel material having a high boundary angle and excellent strain aging impact toughness at a cryogenic temperature having a particle size of 10 μm or less, and a method for manufacturing the same.