POSCO Holdings Inc.
Low-temperature steel plate having excellent impact toughness, and method for manufacturing same

Abstract:

Provided are a low-temperature steel plate having excellent impact toughness, and a method for manufacturing same, the low-temperature steel plate comprising, in wt %, 0.02-0.08% C, 6.0-7.5% Ni, 0.5-0.9% Mn, 0.03-0.15% Si, 0.02-0.3% Mo, and 0.1-0.3% Cr, and 50 ppm or less of P, 10 ppm or less of S, and the remainder in Fe and various unavoidable impurities, and the microstructure at 1/4t (t: thickness of the steel plate) location of the steel plate comprising, in % surface area, 10-35% tempered bainite, 3-15% residual austenite, and the remainder in tempered martensite, and having granularity of 10 .mu.m or less of high angle grain boundaries at 15.degree. or greater as measured by Electron Backscatter Diffraction (EBSD).