At present, China has a material commonly used screw 45 steel, 40Cr, ammoniation steel, 38CrMOAl, high-temperature alloys.

　　No. 1) 45 steel cheap, processing performance, but poor corrosion resistance wear.
Heat treatment: quenching HB220-270, induction hardening HRC45--48.

　　Performance 2) 40Cr steel is better than 45, but often coated with chromium to improve their resistance to corrosion and wear. But require a higher layer of chrome coating is too thin easy to wear, thick is easy peeling, flaking but accelerated corrosion, has been rarely used.
Heat treatment: quenching HB220-270, hard chrome plating HRC> 55

　　3) nitriding steel, 38CrMoAl relatively excellent overall performance, used widely. Usually the nitride layer of 0.4-0.6 mm. But this material ability to resist corrosion of hydrogen chloride is low, and the price is higher.

　　4) high-temperature alloy material is superior to other materials, the material without coating, injection molding machine is mainly used for raw halogen-free screw, the material is anti-oxidation high corrosion resistance, heat hra55`60