Patent ID: 7749431

Claim:
A stainless steel for high-pressure hydrogen gas characterized in that: (a) the steel consists of, by mass %, C: not more than 0.04%, Si: not more than 1.0%, Mn: 7 to 30%, Cr: 15 to 22%, Ni: 5 to 20%, V: 0.001 to 0.57%, N: 0.20 to 0.4510% and Al: not more than 0.10%, and optionally at least one element selected from at least one of the first, second and third groups of elements specified below, and the balance Fe and impurities, (b) among the impurities, P is not more than 0.030%, S is not more than 0.005%, and Ti, Zr and Hf are not more than 0.01% respectively, and (c) the contents of Cr, Mn and N satisfy the following relationship [1]: 2.5Cr+3.4Mn≦300N [1] wherein the symbols of the elements represent the contents, % by mass, of the respective elements; wherein the first group of elements is; Mo: 0.3 to 3.0%, W: 0.3 to 6.0%, Nb: 0.001 to 0.20% and Ta: 0.001 to 0.40%; wherein the second group of elements is; B: 0.0001 to 0.020%, Cu: 0.3 to 5.0%, and Co: 0.3 to 10.00/a; and wherein the third group of elements is; Mg: 0.0001 to 0.0050%, Ca: 0.0001 to 0.0050%, La: 0.0001 to 0.200%, Ce: 0.0001 to 0.200%, Sm: 0.0001 to 0.40%, Pr: 0.0001 to 0.40%, and Nd: 0.0001 to 0.50%, and d) the steel has a tensile strength of not lower than 863 MPa and a yield strength not lower than 534 MPa.