POSCO Holdings Inc.
Austenitic steel having excellent machinability and ultra-low temperature toughness in weld heat-affected zone, and method of manufacturing the same

Abstract:

Provided are an austenitic steel having excellent machinability and ultra-low temperature toughness in a weld heat-affected zone including 15 wt % to 35 wt % of manganese (Mn), carbon (C) satisfying 23.6C+Mn.gtoreq.28 and 33.5C-Mn.ltoreq.23, 5 wt % or less (excluding 0 wt %) of copper (Cu), chromium (Cr) satisfying 28.5C+4.4Cr.ltoreq.57 (excluding 0 wt %), and iron (Fe) as well as other unavoidable impurities as a remainder, wherein a Charpy impact value of a weld heat-affected zone at -196.degree. C. is 41 J or more, and a method of manufacturing the steel. According to the present invention, a low-cost ultra-low temperature steel may be obtained, a stable austenite phase may be formed at low temperature, carbide formation may be effectively suppressed, and a structural steel having excellent machinability and ultra-low temperature toughness in a weld heat-affected zone may be provided.