The screw refers to a cylinder whose outer surface is cut with a spiral groove or a cone which is cut with a spiral groove. Because the screw will be subject to certain corrosion during the extrusion process, and the high temperature, working under high torque, will also be subject to certain wear, the screw has two key requirements for material properties.
1) wear resistance and long life;
2) High temperature resistance, no deformation under high temperature;
3) Corrosion resistant, the material is corrosive;
4) Has good cutting performance;
5) High strength, can withstand high torque, high speed;
6) The residual stress is small after heat treatment, and the thermal deformation is small.