SUPER DUPLEX STAINLESS STEEL HAVING SUPERIOR YIELD STRENGTH AND PRODUCTION METHOD THEREOF

摘要

The present invention relates to a heat treatment method capable of improving yield strength and corrosion resistance in a super duplex stainless steel S32750 (2507 stainless steel) comprising: 24-26 wt% of chrome (Cr), 6.0-8.0 wt% of nickel (Ni), 3.5-5.0 wt% of molybdenum (Mo), 0.24-0.32 wt% of nitrogen (N), and the remaining consisting of iron (Fe) and inevitable impurities, wherein the super duplex stainless includes austenite and ferrite. When a material is heat-treated, a heating rate from 700C to an annealing temperature is controlled at 0.33 C/sec or less. The material is maintained at the annealing temperature of 1,030-1,050C for 5-60 minutes, or is maintained at the annealing temperature of 1,010-1,030C for 40-60 minutes in order to induce extraction of a secondary austenite inside the ferrite. As such, the super duplex stainless steel with excellent yield strength and corrosion resistance is able to be provided.