Spring steel refers to the steel specially used for manufacturing springs and elastic elements due to its elasticity in the quenching and tempering state. The elasticity of steel depends on its elastic deformation capacity, that is, within the specified range, the elastic deformation capacity makes it bear a certain load, and no permanent deformation occurs after the load is removed. Spring steel shall have excellent comprehensive properties, such as mechanical properties (especially elastic limit, strength limit, yield ratio), anti elastic property (i.e. anti elastic degradation property, also known as anti relaxation property), fatigue property, hardenability, physical and chemical properties (heat resistance, low temperature resistance, oxidation resistance, corrosion resistance, etc.).