The commonly used screw materials in our country are No. 45 steel, 40Cr, ammoniated steel, 38CrMOAl, high temperature alloy and so on. 1) No. 45 steel is cheap and has good processing performance, but its wear resistance and corrosion resistance are poor. Heat treatment: quenching and tempering HB220-270, high-frequency quenching HRC45-48. 2) The performance of 40Cr is better than that of No. 45 steel, but it is often plated with a layer of chromium to improve its corrosion resistance and wear resistance. However, the requirements for the chromium plating layer are relatively high. If the plating layer is too thin, it is easy to wear, and if it is too thick, it is easy to peel off. After peeling, it will accelerate the corrosion. It has been less used. Heat treatment: quenched and tempered HB220-270, hard chromium plating HRC>553) Nitrided steel, 38CrMoAl has excellent comprehensive properties and is widely used. Generally, the nitride layer reaches 0.4-0.6 mm. However, this material has low resistance to hydrogen chloride corrosion and is relatively expensive. 4) The high temperature alloy material is superior to other materials. The material does not require coating and is mainly used for the halogen-free screw of the injection molding machine. The material has high oxidation resistance and corrosion resistance. The heat treatment is hra55`60.