Austenitic stainless steel material, method for producing the same, and device for hydrogen

An austenitic stainless steel material, wherein

• a chemical composition comprises, in mass %:
• C:
• 0.20% or less;
• Si:
• 2.0% or less;
• Mn:
• 6.0 to 20.0%;
• P:
• 0.060% or less;
• S:
• 0.0080% or less;
• Cr:
• 10.0 to 18.0%;
• Ni:
• 4.0 to 12.0%;
• N:
• 0.01 to 0.30%;
• Cu:
• 4.0% or less;
• Mo:
• 3.0% or less;
• Al:
• 0 to 0.20%;
• Ca:
• 0 to 0.01%;
• B:
• 0 to 0.01%;
• Mg:
• 0 to 0.01%;
• Nb:
• 0 to 1.0%;
• Ti:
• 0 to 1.0%;
• V:
• 0 to 1.0%;
• W:
• 0 to 2.0%;
• Zr:
• 0 to 1.0%;
• Co:
• 0 to 2.0%;
• Ga:
• 0 to 0.10%;
• Hf:
• 0 to 0.10%;
• REM:
• 0 to 0.10%;
• and
• the balance:
• Fe and impurity,
• an A value calculated by a formula (i) described below is 30.0 to 60.0, and
• in a metallurgical structure of a surface layer, a proportion Gs of high angle grain boundaries satisfies a formula (ii) described below:
• A value=3.2Mn+0.7Cr+6.2Ni+38.7N+4.8Cu+9.3Mo−53 (i)
• 0.1<Gs<0.6 (ii)
• where element symbols in the formula (i) denote contents (mass %) of the elements contained in steel, 0 is given when the element is not contained, and a symbol in the formula described above is defined as follows:
• Gs:
• proportion of high angle grain boundaries.