Austenitic stainless steel material

An austenitic stainless steel material, which has a passivation film on a surface, comprising:

• a chemical composition consisting of, in mass %,
• C:
• 0.10% or less,
• Si:
• 1.0% or less,
• Mn:
• 8.0 to 10.0%,
• P:
• 0.030% or less,
• S:
• 0.0030% or less,
• Cr:
• 15.0 to 18.0%,
• Ni:
• 7.0 to 9.0%,
• N:
• 0.15 to 0.25%,
• Al:
• 0.005 to 0.20%,
• Ca:
• 0.0005 to 0.01%,
• Cu:
• less than 1.0%,
• Mo:
• less than 1.0%,
• B:
• 0 to 0.0050%,
• Nb:
• 0 to 0.50%,
• Ti:
• 0 to 0.50%,
• V:
• 0 to 0.50%,
• W:
• 0 to 0.50%,
• Zr:
• 0 to 0.50%,
• Co:
• 0 to 0.50%,
• Mg:
• 0 to 0.005%,
• Ga:
• 0 to 0.010%,
• Hf:
• 0 to 0.10%,
• REM:
• 0 to 0.10%, and
• the balance:
• Fe and impurities,
• wherein:
• an f value calculated by Formula (i) below is more than 29.5 and less than 32.5;
• cation fractions of a chemical composition in the passivation film satisfy Formula (ii) below:
• f value=Ni+0.72Cr+0.88Mo+1.11Mn−0.27Si+0.53Cu+12.93C+7.55N (i)
• 4.5≤(Mn+Fe)/Cr<9.0 (ii)
• where, each symbol of an element in Formula (i) above represents a content (mass %) of the corresponding element contained in the steel, with a value of a symbol being taken as zero if the corresponding element is not contained, and each symbol of an element in Formula (ii) above represents a cation fraction (atomic percent) of the corresponding element contained in the passivation film, with a value of a symbol being taken as zero if the corresponding element is not contained.