Method for manufacturing austenitic stainless steel

Abstract

A high Si-containing austenitic stainless steel having corrosion resistance in a nitric acid environment at a high temperature is made by hot-rolling a slab of stainless steel and heat treating the hot-rolled stainless steel at a temperature of 1100 to 1160° C. The steel is cooled at cooling rate of at least 100° C./min. The stainless steel has a chemical composition containing: C: at most 0.04%; Cr: 7 to 20%, Ni: 10 to 22%, Si: 2.5 to 7%, Mn: at most 10%, sol. Al: at most 0.03%, P: at most 0.03%, S: at most 0.03%; N: at most 0.035%, a total of one or more of Nb, Ti, Ta, and Zr being 0.05 to 0.7%; and the remainder Fe and impurities. The heating temperature during the hot rolling is T h in which ΔT of Formula (1): T h =1135−90 Si−2.9Cr+40 Ni−ΔT is at least 30□C.

1 . A method for manufacturing austenitic stainless steel comprising
 a hot rolling step of heating and hot-rolling a slab of stainless steel at a heating temperature T h  during the hot rolling   wherein   the slab of stainless steel has a chemical composition containing: by mass %, C: at most 0.04%; Cr: 7 to 20%, Ni: 10 to 22%, Si: 2.5 to 7%, Mn: at most 10%, sol. Al: at most 0.03%, P: at most 0.03%, S: a at most 0.03%; N: at most 0.035%, a total amount of one or more types of elements selected from Nb, Ti, Ta, and Zr: 0.05 to 0.7%; and the remainder being Fe and impurities,   and   the heating temperature T h  is defined as T h  in which ΔT of Formula (1): T h =1135−90Si−2.9Cr+40Ni−ΔT is at least 30° C. or more.   
     
     
         2 . The method for manufacturing austenitic stainless steel according to  claim 1 , further comprising
 a heat treatment step of subjecting the austenitic stainless steel obtained through the hot rolling to heat treatment within a temperature range of 1100 to 1160° C., and thereafter, cooling the austenitic stainless steel at cooling rate of at least 100° C./min.