related production materials and strength requirements
Screws are rod-shaped mechanical parts that use their own threads to transmit motion or power. The outer surface is cut with a spiral groove or a cone with a tapered spiral groove. The screw has different heads, like the head in the picture is called an external hexagon screw. There are others, such as large flat screws, hex screws, and so on.
Zhoushan screw requirements for material:
It can be known from the extrusion process that the screw works under high temperature, certain corrosion, strong wear and high torque. Therefore, the screw must:
1. High temperature resistance, no deformation under high temperature;
2. Wear resistance and long life;
3. Corrosion resistance, the material is corrosive;
4. High strength, can withstand large torque and high speed;
5. Has good cutting performance;
6. Small residual stress and small thermal deformation after heat treatment.
Common screw materials:
Currently used screw materials are 45 # steel, 40Cr, ammoniated steel, 38CrMOAl, etc.
1.45 steel is cheap and has good processing performance, but has poor wear resistance and corrosion resistance.
Heat treatment: quenched and tempered HB220-270, high frequency quenching HRC45-48.
The performance of 2.40Cr is better than 45 steel, but it is often coated with chromium to improve its ability to resist corrosion and wear. However, the chrome plating layer has higher requirements. The coating is too thin and easy to wear, and too thick to peel off. After peeling, it will accelerate corrosion. It is currently less used.
Heat treatment: quenched and tempered HB220-270, hard chromium plating HRC> 55.
3. Nitrided steel and 38CrMoAl have excellent comprehensive properties and are widely used. Generally, the nitride layer is 0.4-0.6 mm. However, this material has low resistance to hydrogen chloride corrosion and is relatively expensive.
Heat treatment: quenched and tempered HB220-270, nitriding HRC> 65.
Titanium carbide coating methods are used abroad to improve the corrosion resistance of the screw surface, but it is reported that its wear resistance is not good enough. In recent years, a series of measures have been taken abroad to improve the wear and corrosion resistance of screws. One approach is to use highly wear-resistant and corrosion-resistant alloy steel. Such as 34CrAlNi, 31CrMo12 and so on. There is also a method of spraying Xaloy alloy on the surface of the screw. This Xaloy alloy has high wear and corrosion resistance.