420J2 is a Martensitic stainless steel whose mechanical properties can be adjusted through heat treatment. In layman’s terms, it is a type of hardenable stainless steel. Typical grades are Cr13 type, such as 2Cr13, 3Cr13, 4Cr13, etc. 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.