Austenitic stainless steel excellent in intergranular corrosion resistance and stress corrosion cracking resistance, and method for producing austenitic stainless steel material

Abstract

An austenitic stainless steel excellent in intergranular corrosion resistance and stress corrosion cracking resistance, comprising: C: 0.005 wt % or less; Si: 0.5 wt % or less; Mn: 0.5 wt % or less; P: 0.005 wt % or less; S: 0.005 wt % or less; Ni: 15.0 to 40.0 wt %, Cr: 20.0 to 30.0 wt %, N: 0.01 wt % or less; O: 0.01 wt % or less; and the balance of Fe and inevitable impurities, wherein the content of B included in the inevitable impurities is 3 wt ppm or less.

1 . An austenitic stainless steel comprising Fe and: C: 0.005 wt % or less; Si: 0.5 wt % or less; Mn: 0.5 wt % or less; P: 0.005 wt % or less; S: 0.005 wt % or less; Ni: 15.0 to 40.0 wt %, Cr: 20.0 to 30.0 wt %, N: 0.01 wt % or less; O: 0.01 wt % or less; and inevitable impurities, wherein
 a content of B in the total weight of the steel is 3 wt ppm or less.   
     
     
         2 . The austenitic stainless steel according to  claim 1 , wherein the total content of C, P, S, N and O is 0.02 wt % or less. 
     
     
         3 . The austenitic stainless steel according to  claim 2 , further comprising Ti, wherein a content of Ti is an amount stoichiometrically equivalent to or more than the total content of C, P, S, N and O. 
     
     
         4 . A method of producing an austenitic stainless , the method comprising:
 hot working an ingot having a chemical composition of the stainless steel according to  claim 1 ; and   solution treating the stainless steel material obtained by the hot working; wherein   the solution treating comprises:   heating the stainless steel material at a heat treatment temperature in a first temperature range of 1000 to 1150° C. for 1 minute or more; and then,   cooling the stainless steel material from the heat treatment temperature in the first temperature range to ordinary temperature by rapid or natural cooling.   
     
     
         5 . A method of producing an austenitic stainless steel, the method comprising:
 hot working an ingot having a chemical composition of the stainless steel according to  claim 1 ; and   solution treating the stainless steel material obtained by the hot working; wherein   the solution treating comprises:   heating the stainless steel material at a heat treatment temperature in a first temperature range of 1000 to 1150° C. for 1 minute or more;   cooling the stainless steel material from the heat treatment temperature in the first temperature range by rapid or natural cooling;   heating the stainless steel material at a heat treatment temperature in a second temperature range of 650° C. or higher for 10 minutes or more after the cooling, and then,   cooling the stainless steel material from the heat treatment temperature in the second temperature range to ordinary temperature by rapid or natural cooling.   
     
     
         6 . The method of producing an austenitic stainless steel material according to  claim 4 , after the solution treatment, further comprising:
 cold working the stainless steel material at a working ratio of 40% or more and less than 75%; and then   heating the stainless steel material at a heat treatment temperature in a temperature range of 700° C. or higher for 10 minutes or more for recrystallization.   
     
     
         7 . The method of producing an austenitic stainless steel material according to  claim 6 , between the cold working and the recrystallization treatment, further comprising:
 heating the stainless steel material at a heat treatment temperature in a range of 500 to 650° C. for 30 minutes or more to deposit precipitation in strain aging.