Austenitic stainless steel for hydrogen gas and method for its manufacture

Abstract

An austenitic stainless steel for use in a hydrogen gas atmosphere comprises, in mass %, C: 0.10% or less, Si: 1.0% or less, Mn: 0.01 to 30%, P: 0.040% or less, S: 0.01% or less, Cr: 15 to 30%, Ni: 5.0 to 30%, Al: 0.10% or less, N: 0.001 to 0.30 % with the balance Fe and inevitable impurities. An X-ray (111) integration intensity of a cross section along the direction rectangular to the working direction is five times that in a random direction or less, and the X-ray integration intensity ratio of a cross section along the working direction satisfies I(220)/I(111)≦10. The high strength steel can also contain one or more of the groups of Mo and W; V, Nb, Ta, Ti, Zr and Hf; B; Cu and Co; Mg, Ca, La, Ce, Y, Sm, Pr and Nd.

1 . An austenitic stainless steel for hydrogen gas characterized by having a chemical composition comprising, in mass percent, C: at most 0.10%, Si: at most 1.0%, Mn: 0.01-30%, P: at most 0.040%, S: at most 0.01%, Cr: 15-30%, Ni: 5.0-30%, sol. Al: at most 0.10%, N: 0.001-0.30%, and a remainder of Fe and impurities, and by having a structure such that the x-ray integrated intensity I(111) of a cross section in a direction perpendicular to the direction of working is at most 5 times that of a random direction and such that the x-ray integrated intensity ratio I(220)/I(111) of a cross section in the direction of working is at most 10.  
   
   
       2 . An austenitic stainless steel as set forth in  claim 1  wherein the chemical composition further contains, in mass percent, at least one of Mo: 0.3-3.0% and W: 0.3-6.0%.  
   
   
       3 . An austenitic stainless steel as set forth in  claim 1  wherein the chemical composition further contains, in mass percent, at least one of V: 0.001-1.0%, Nb: 0.001-1.0%, Ta: 0.001-1.0%, Ti: 0.001-1.0%, Zr: 0.001-1.0%, and Hf: 0.001-1.0%.  
   
   
       4 . An austenitic stainless steel as set forth in  claim 2  wherein the chemical composition further contains, in mass percent, at least one of V: 0.001-1.0%, Nb: 0.001-1.0%, Ta: 0.001-1.0%, Ti: 0.001-1.0%, Zr: 0.001-1.0%, and Hf: 0.001-1.0%.  
   
   
       5 . An austenitic stainless steel as set forth in  claim 3  wherein the chemical composition further contains, in mass percent, at least one of Nb: greater than 0.20% not greater than 1.0%, Ta: greater than 0.40% not greater than 1.0%, and Ti: greater than 0.10% not greater than 1.0%, and wherein C+N is ≦0.05%.  
   
   
       6 . An austenitic stainless steel as set forth in  claim 4  wherein the chemical composition further contains, in mass percent, at least one of Nb: greater than 0.20% not greater than 1.0%, Ta: greater than 0.40% not greater than 1.0%, and Ti: greater than 0.10% not greater than 1.0%, and wherein C+N is ≦0.05%.  
   
   
       7 . An austenitic stainless steel as set forth in  claim 1  wherein the chemical composition further contains, in mass percent, 0.0001-0.020% of B.  
   
   
       8 . An austenitic stainless steel as set forth in  claim 2  wherein the chemical composition further contains, in mass percent, 0.0001-0.020% of B.  
   
   
       9 . An austenitic stainless steel as set forth in  claim 3  wherein the chemical composition further contains, in mass percent, 0.0001-0.020% of B.  
   
   
       10 . An austenitic stainless steel as set forth in  claim 4  wherein the chemical composition further contains, in mass percent, 0.0001-0.020% of B.  
   
   
       11 . An austenitic stainless steel as set forth in  claim 5  wherein the chemical composition further contains, in mass percent, 0.0001-0.020% of B.  
   
   
       12 . An austenitic stainless steel as set forth in  claim 6  wherein the chemical composition further contains, in mass percent, 0.0001-0.020% of B.  
   
   
       13 . An austenitic stainless steel as set forth in  claim 1  wherein the chemical composition further contains, in mass percent, at least one of Cu: 0.3-2.0% and Co: 0.3-5.0%.  
   
   
       14 . An austenitic stainless steel as set forth in  claim 1  wherein the chemical composition further contains, in mass percent, at least one of Mg: 0.0001-0.0050%, Ca: 0.0001-0.0050%, La: 0.0001-0.20%, Ce: 0.0001-0.20%, Y: 0.0001-0.40%, Sm: 0.0001-0.40%, Pr: 0.0001-0.40%, and Nd: 0.0001-0.50%.  
   
   
       15 . An austenitic stainless steel as set forth in  claim 1  characterized in that the austenite average grain diameter is at most 20 μm.  
   
   
       16 . An austenitic stainless steel as set forth in  claim 14  characterized in that the austenite average grain diameter is at most 20 μm.  
   
   
       17 . A method of manufacturing an austenitic stainless steel for hydrogen gas characterized by carrying out plastic working with a decrease in cross section of 10-50% in a temperature range of room temperature to 200° C. on a steel having a chemical composition as set forth in  claim 1 , and then performing final plastic working with a reduction in cross section of at least 5% in a direction different from the direction of working of the above-described plastic working.