CAST AUSTENITIC STAINLESS STEEL EXCELLENT IN NITRIC ACID RESISTANCE AND SURFACE TREATMENT THEREFOR

摘要

PURPOSE: To produce a cast austenitic stainless steel for structural purposes, excellent in corrosion resistance under a nitric acid environment with a concentration not higher than azeotropic concentration and also having high strength and superior castability. ;CONSTITUTION: This steel is a cast high strength austenitic stainless steel having a steel composition which consists of, by weight, ≤0.03% C, 0.3-1% Si, ≤2% Mn, ≤0.03% P, ≤0.03% S, 19-21% Cr, 8.5-12% Ni, 0.05-0.2% N, 0.03-0.1% Nb+Ta, ≤0.001% B, and the balance Fe with inevitable impurities and in which the ratio between Creq, represented by Creq=%Cr+1.5×%Si+1.4×%Mo+%Nb-4.99, and Nieq, represented by Nieq=%Ni+30×%C+0.5×%Mn+26×(%N-0.02)+2.77, is regulated to 0.9-1.2, also having superior castability, and excellent in nitric acid resistance under a nitric acid environment with a concentration not higher than azeotropic concentration. Surface treatment for this cast austenitic stainless steel excellent in nitric acid resistance can be performed by immersing this cast steel for ≥30min in an aqueous solution having a temp. of 40-70°C and 20-50wt.% nitric acid concentration.;COPYRIGHT: (C)1996,JPO