JPS57116757A - High-chromium low-nickel two-phase stainless steel with superior acid resistance - Google Patents

Abstract

PURPOSE: To obtain a high-Cr low-Ni 2-phase stainless steel having superior corrosion resistance to 20W30% sulfuric acid and applicable to apparatus parts with large cross-sectional area by providing a composition contg. a large amount of Cr, a specified amount of Mo, a relatively small amount of Ni and a large amount of N.

CONSTITUTION: This 2-phase stainless steel consists of, by wt., ≤0.08% C, ≤1.5% Si, ≤1.5% Mn, ≤0.03% P, ≤0.03% S, 3W5% Ni, 0.5W4% Mo, 30W36% Cr, 0.3W0.6% N and the balance Fe with inevitable impurities. The lower limit or more of Ni is required to provide a 2-phase structure owing to the deposition of γ phase and to improve the mechanical characteristics such as ductility and toughness and the corrosion resistance owing to the structure, yet more than the upper limit of Ni deteriorates the corrosion resistance. The lower limit or more of Mo is required to improve the sulfuric acid resistance, yet more than the upper limit of Mo deteriorates the workability and ductility. The lower limit or more of Cr is required to improve the corrosion resistance of the γ phase inferior to the other α phase, yet more than the upper limit of Cr causes embrittlement and deteriorates the workability and weldability. The lower limit or more of N is required to improve the ductility, toughness and corrosion resistance owing to the 2-phase structure, yet more than the upper limit of N causes difficult addition and casting defects.

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