Patent ID: 7767039

Claim:
A martensitic stainless steel having a martensitic microstructure and consisting essentially of, in mass %, C: 0.001-0.1%, Si: 0.05-1.0%, Mn: 0.05-2.0%, P: at most 0.025%, S: at most 0.010%, Cr: 11-18%, Ni: 1.5-10%, sol. Al: 0.001-0.1%, N: at most 0.1%, O: at most 0.01%, Cu: 0-5%, solid solution Mo: 3.5-7%, W: 0-5%, V: 0-0.50%, Nb: 0-0.50%, Ti: 0-0.50%, Zr: 0-0.50%, Ca: 0-0.05%, Mg: 0-0.05%, REM: 0-0.05%, and B: 0-0.01%, the composition satisfying the following Equation (1), and a remainder of Fe and impurities and undissolved Mo, if undissolved Mo is present: Ni-bal.=30(C+N)+0.5(Mn+Cu)+Ni+8.2−1.1(Cr+Mo+1.5Si)≧−4.359. Equation (1)