Ferritic stainless steel and method for manufacturing same

Ferritic stainless steel comprising:

• not more than 0.025% by mass of C,
• not less than 0.05% by mass and not more than 3.0% by mass of Si,
• not less than 0.05% by mass and not more than 2.0% by mass of Mn,
• not more than 0.04% by mass of P,
• not more than 0.03% by mass of S,
• not more than 0.5% by mass of Ni,
• not less than 10.5% by mass and not more than 25.0% by mass of Cr,
• not more than 0.025% by mass of N,
• not less than 0.39% by mass and not more than 1.0% by mass of Nb,
• not more than 3.0% by mass of Mo,
• not more than 0.13% by mass of Cu,
• not more than 0.2% by mass of Al,
• not more than 0.5% by mass of Ti, and
• iron and an inevitable impurity as a remainder,
• when spectra are measured by XPS analysis at a surface of said ferritic stainless steel and at depths of from 0.5 nm to 6 nm from the surface in increments of 0.5 nm, said ferritic stainless steel satisfying the following Expression (1):
• 240≤Cr(O)+Si(O)≤261 (1)
• where
• (i) Cr(O) represents a value obtained by calculating, for each measurement depth in terms of an atomic percent concentration with use of each of the spectra, a proportion of the total number of atoms of Cr which is present as oxide or hydroxide to the total number of atoms of Fe, Cr, Ti, Nb, Mo, and Si each of which is present as a simple substance, oxide, or hydroxide and integrating all calculated atomic percent concentrations, and
• (ii) Si(O) represents a value obtained by calculating, for each measurement depth in terms of an atomic percent concentration with use of each of the spectra, a proportion of the number of atoms of Si which is present as oxide to the total number of atoms of Fe, Cr, Ti, Nb, Mo, and Si each of which is present as a simple substance, oxide, or hydroxide and integrating all calculated atomic percent concentrations.