DUPLEX STAINLESS STEEL HAVING EXCELLENT CORROSION RESISTANCE IN HEAT AFFECTED ZONE IN SULFIDE ENVIRONMENT

摘要

PURPOSE:To exceedingly improve the corrosion resistance of the heat affected zone in the duplex stainless steel in the atmosphere having the presence of hydrogen sulfide by specifying the alloy concn. and ferrite fractional rate in ferrite in the duplex stainless steel used in the above atmosphere. CONSTITUTION:The compsn. of the duplex stainless constituted of ferrite and austenite used in the atmosphere of high corrosivity contg. H2S is regulated to the one contg., by weight, 0.2% C, 2% Mn, 0.03% P, 0.001% S, 20 to 30% Cr, 2.5 to 4.0% Mo, 7.5 to 17% Ni, 2% Si and 0.1 to 0.4% of one or two kinds among Ti, Nb and V, or furthermore contg. one or both of 1% Cu and 1% W and the balance Fe. Furthermore, the ferrite fractional rate (f) expressed by the formula I is regulated so as to satisfy 0.3f0.7 and the index S of pitting corrosion resistance is regulated to the value expressed by the formula II, by which the heat affected zone in the duplex stainless steel exhibits excellent resistance to the corrosion such as pitting and stress corrosion cracking.