Martensitic stainless steel for brake disk and method for producing said steel

A martensitic stainless steel used for a brake disk of a two-wheeled vehicle, the martensitic stainless steel comprising:

• in % by mass, C of 0.025% to 0.080%, Si of 0.05% to 0.8%, Mn of 0.5% to 1.5%, P of 0.035% or less, S of 0.015% or less, Cr of 11.0% to 13.5%, Ni of 0.01% to 0.50%, Cu of 0.01% to 0.08%, Mo of 0.01% to 0.30%, V of 0.01% to 0.10%, Al of 0.05% or less, and N of 0.015% to 0.060%;
• the balance being Fe and inevitable impurities;
• a DFE value defined by a formula (1) ranging from 5 to 30;
• and
• a δ ferrite fraction observed in a cross section structure ranging from 5% to 30% by an area ratio,
• DFE=12(Cr+Si)−430C−460N−20Ni−7Mn−89 Formula (1)
• where:
• Cr, Si, C, N, Ni and Mn in the formula (1) respectively indicate contents.