AUSTENITIC STAINLESS STEEL HAVING SUPERIOR CREEP RUPTURE DUCTILITY

摘要

PURPOSE:To further improve the creep rupture ductility of an austenitic stainless steel having a specified compsn. as well as to ensure high corrosion resistance, by specifying the amounts of B and Mo in the steel and the grain size of the steel. CONSTITUTION:The compsn. of an austenitic stainless steel is composed of, by weight, =0.06% C, 0.02-0.07% N, 0.0006-0.0025% B, 0.20-0.8% Mo (B/Mo=0.003), 16.0-19.0% Cr, 9.0-12.0% Ni and the balance Fe. The grain size of the steel is regulated to ASTM grain size No.=4.5. In the steel, B shows a strength and ductility improving effect but the effect is not well shown by 0.0006% B and 0.0025% B deteriorates the corrosion resistance of the grain boundaries. Mo is effective in improving the strength at high temp. and the corrosion resistance by solid soln. strengthening and precipitation strengthening but 0.20% Mo is not effective and 0.8% Mo deteriorates the creep rupture ductility. The ratio of B/Mo is regulated to =0.003 so as to control the increase of the sensitivity to intergranular corrosion by the addition of B. In case of grain size No.4.5, the creep rupture elongation is not considerably improved.