Screw (Pinyin: Lu Gómez G Shan N, English: Screw): The outer surface is cut with a cylindrical spiral groove or a cone with a conical spiral groove. The screw has a different head, like the head in the picture called the outer hexagonal screw. There are other, such as large flat screw, hexagon screws and so on.
Requirements for material
From the extrusion process, the screw is in high temperature, certain corrosion, intense wear, large torque work under, so the screw must:
1 high temperature resistance, not deformed at elevated temperatures;
2 wear resistance, long life;
3 corrosion resistance, corrosion of materials;
4 high strength, can withstand large torque, high speed;
5 have good machining performance;
6 after heat treatment residual stress is small, heat deformation is small.