POSCO Holdings Inc.
ULTRA-THICK STEEL MATERIAL HAVING EXCELLENT SURFACE PART NRL-DWT PROPERTIES AND METHOD FOR MANUFACTURING SAME

Abstract:

Disclosed are a high-strength ultra-thick steel material and a method for manufacturing same. The high-strength ultra-thick steel material comprises in weight % 0.04-0.1% of C, 1.2-2.0% of Mn, 0.2-0.9% of Ni, 0.005-0.04% of Nb, 0.005-0.03% of Ti and 0.1-0.4% of Cu, 100 ppm or less of P and 40 ppm or less of S with a balance of Fe, and inevitable impurities, and comprises, in a subsurface area up to t/10 (t hereafter being referred to as the thickness of the steel material) , polygonal ferrite of 50 area % or greater (including 100 area %) and bainite of 50 area % or less (including 0 area %) as microstructures.