Martensitic stainless steel whose mechanical properties can be adjusted by heat treatment, in layman’s terms, is a type of hardenable stainless steel. Typical grades are Cr13 type, such as ss410, ss420, ss430, and so on. After quenching, the hardness is higher, and different tempering temperatures have different combinations of strength and toughness. It is mainly used for steam turbine blades, tableware, and surgical instruments. According to the difference in chemical composition, martensitic stainless steel can be divided into two types: martensitic chromium steel and martensitic chromium-nickel steel. The structure and strengthening mechanism can also be divided into martensitic stainless steel, martensitic and semi-austenitic (or semi-martensitic) precipitation-hardening stainless steel, and maraging stainless steel. Cast martensitic stainless steel is divided into: