Currently commonly used extruder screw materials are: 45 steel, 40Cr, ammoniated steel, 38CrMOAl and so on.
It has poor wear resistance and corrosion resistance.
Heat treatment: quenching and tempering HB220-270, high-frequency quenching HRC45-48.
The extruder screw material 40Cr 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. At present, it is rarely used.
Heat treatment: tempered HB220-270, hard chromium plating HRC>55.
Generally, the nitride layer reaches 0.4-0.6 mm. However, the extruder screw material has low resistance to hydrogen chloride corrosion, and the price is relatively high.
Heat treatment: tempering HB220-270, nitriding HRC>65.
In foreign countries, there is a method of titanium carbide coating to improve the corrosion resistance of the extruder screw surface. But according to reports, its wear resistance is not good enough.
In recent years, the industry has taken a series of measures to improve the wear resistance and corrosion resistance of the extruder screw. One way is to use highly wear-resistant and corrosion-resistant alloy steel, such as 34CrAlNi, 31CrMo12, etc. There is also a method of spraying copper and aluminum alloy on the surface of the extruder screw. This copper-aluminum alloy has high wear resistance and corrosion resistance.
