Patent ID: 6890665

Claim:
A martensitic stainless steel comprising: in mass % C: 0.15-0.22%, Si: 0.18-1.0%, Mn: 0.05-1.0%, Cr: 10.5-14.0% and Fe as substantial residual, and further including Ni: not more than 0.20%, Al: not more than 0.05%, N: not more than 0.100%, S: not more than 0.015% and P: not more than 0.020% as impurities; wherein a scale layer on the surface of the base material consists of an inner layer scale including mainly FeCr 2 O 4 , and an outer layer scale having a thickness of not more than 20 μm deposited on the surface of the inner layer scale at a surface coverage of not less than 1% and not more than 15%; and wherein rust preventive oil is applied to the surface of said scale layer.