Commonly used screw materials include 45 steel, 40Cr, nitrided steel, 38CrMoAl, and high-temperature alloys. 1) 45 steel is inexpensive and has good machinability, but poor wear and corrosion resistance. Heat treatment: quench and temper HB220-270, high-frequency quenching HRC45-48. 2) 40Cr has better performance than 45 steel, but it often requires a chromium plating to improve its corrosion and wear resistance.
However, the chromium plating layer requires high precision; too thin a layer is prone to wear, while too thick a layer is prone to peeling, which accelerates corrosion. Therefore, it is less commonly used. Heat treatment: quench and temper HB220-270, hard chromium plating HRC>55. 3) Nitrided steel and 38CrMoAl have excellent overall performance and are widely used. The nitriding layer is typically 0.4-0.6 mm thick. However, this material has low resistance to hydrogen chloride corrosion and is relatively expensive. 4) High-temperature alloy materials are superior to other materials. This material does not require plating and is mainly used for producing halogen-free screws in injection molding machines. This material has high oxidation and corrosion resistance and can be heat treated to 55-60 degrees Celsius.