Austenitic stainless steel plate

An austenitic stainless steel plate having a chemical composition consisting of, by mass %,

• C:
• 0.150% or less,
• Si:
• 2.0% or less,
• Mn:
• 3.00% or less,
• P:
• 0.060% or less,
• S:
• 0.0080% or less,
• Cr:
• 16.0 to 22.0%,
• Mo:
• 3.00% or less,
• Ni:
• 8.0 to 15.0%,
• Cu:
• 2.0% or less,
• Al:
• 0.080% or less,
• N:
• 0.250% or less,
• Nb:
• 0 to 0.10%,
• Ti:
• 0 to 0.10%,
• B:
• 0 to 0.0050%,
• V:
• 0 to 0.50%,
• W:
• 0 to 0.50%,
• Ca:
• 0 to 0.0100%,
• Mg:
• 0 to 0.0100%,
• Zr:
• 0 to 0.50%,
• Co:
• 0 to 1.0%,
• Ga:
• 0 to 0.010%,
• Hf:
• 0 to 0.10%,
• REM:
• 0 to 0.10%, and
• the balance:
• Fe and impurities, wherein
• when changes in concentrations of elements O, Fe, Cr, Mn, Ni, Mo, Si, Cu, Al, and N are measured from an outermost surface of the steel plate in a depth direction by using glow discharge optical emission spectrometry and a total amount of the elements except for O is converted to 100% by mass %,
• a maximum value of A-value calculated by Formula (i) described below is 45 or more in a region from the outermost surface down to a depth position of 20 nm,
• a minimum value of B-value calculated by Formula (ii) described below is 25 or more in a region from the outermost surface down to a depth position of 50 nm, and
• the austenitic stainless steel plate has a plate thickness of 4.5 mm or more:
• A
• -
• value
• =
• Cr
• +
• 2
• ⁢
• Si
• +
• 5
• ⁢
• Mo
• +
• 10
• ⁢
• Al
• (
• i
• )
• B
• -
• value
• =
• Cr
• +
• Ni
• +
• Mn
• +
• Cu
• +
• 8
• ⁢
• N
• (
• ii
• )
• where each element symbol in the Formulas (i) and (ii) represents a content (by mass %) of each element measured in each depth position in the glow discharge optical emission spectrometry and is zero when the element is not contained.