What are the common materials of screw?

Common materials of screw
1) 45 steel is cheap and has good processability, but poor wear and corrosion resistance.
Heat treatment: quenching and tempering hb220-270, high frequency quenching hrc45-48
2) The performance of 40Cr is better than that of 45 steel, but a layer of chromium is often needed to improve its corrosion and wear resistance. However, the requirement for chromium plating is high. Too thin coating is easy to wear, too thick coating is easy to peel off, but after peeling off, the corrosion is accelerated, so it has been rarely used.
Heat treatment: quenching and tempering hb220-270, hard chromium plating HRC > 55
3) Nitriding steel and 38CrMoAl have excellent comprehensive properties and are widely used. Generally, the nitrided layer is 0.4-0.6 mm. However, this material has low resistance to hydrogen chloride corrosion and high price.
4) The superalloy material is superior to other materials. The material is mainly used for raw halogen-free screw of injection molding machine without coating. The material has high oxidation resistance and corrosion resistance, heat treatment hra55 ` 60
At present, 45 steel, 40Cr, ammoniated steel, 38CrMoAl, superalloy and so on are commonly used in China.