IMPROVEMENT OF RESISTANCE TO NITRIC-ACID CORROSION IN WELD ZONE OF AUSTENITIC STAINLESS STEEL

摘要

PURPOSE:To securely improve resistance to nitric-acid corrosion in the undermentioned weld zone by applying specific heat treatment to the weld zone of a low-C austenitic stainless steel material to which specific heat treatment is previously applied. CONSTITUTION:An austenitic stainless steel material which contains =0.02% by weight of C and in which P content is limited preferably to =0.02% is heated to 650-950 deg.C for =1min. Subsequently, the above steel material is cooled down to ordinary temp. by means of rapid cooling or allowing it to stand to be cooled in the case of heating at 650-850 deg.C and also by means of rapid cooling in the case of heating at 850-950 deg.C, by which the austenitic stainless steel material having high corrosion resistance to high-temp. nitric acid containing oxidizing metal ions is obtained. The weld zone of the above steel material is heated to 650-950 deg.C for =1min and then cooled down to ordinary temp. by means of rapid cooling or alloying it to stand to be cooled in the case of heating at 650-850 deg.C and also by means of rapid cooling in the case of heating at 850-950 deg.C. It is desirable to pass the steel material through the temp. region of 350-620 deg.C in 30min in the above rapid cooling. By the above heat treatment, be resistance to nitric-acid corrosion in the above weld zone can be securely improved.