TWO-PHASE STAINLESS STEEL

摘要

The duplex stainless steel according to the invention provides super duplex stainless steel with low susceptibility to weld cracks and high weldability, as well as the resistance to stress corrosion cracking and toughness of the weld zones. The steel is therefore suitable for a wide range of applications including heat exchangers exposed to sea water, brine-resistant equipment and structures, pipings in chemical plants, line pipes, and oil well pipes. The steel according to the invention is principally characterized by a composition consisting of, by weight, 2.0% or less Si, 2.0% or less Mn, 22.0-24.0% Cr, 4.5-6.5% Ni, 4.0-4.8% Mo, 0.001-0.15% Al, and 0.25-0.35% N, the remains of Fe and inevitable impurities including 0.03% or less C, 0.05% or less P and 0.005% or less S, and a RVS, the index of susceptibility to cracking on welding, 7 or less, and a PREW, the index of pitting resistance, greater than 40.