1. Commonly used materials for twin screw barrel screws
The most common screw barrel materials in China are 45# steel, 40Cr, nitrided steel and 38CrMOAl. The performance requirements of these materials will be introduced one by one, as follows:
(1) The screw barrel material of 45 steel is relatively cheap, cost-effective, and has good processing functions. The only disadvantage is: poor wear resistance and corrosion resistance. Heat treatment: quenching and tempering HB220-270; high frequency quenching HRC45-48.
(2) The screw barrel material of 40Cr has better functions than 45# steel, but we need to plate a layer of chromium frequently to improve its ability to resist corrosion and wear. However, there are higher requirements for the chrome plating layer. 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 corrosion, so the material is currently used less. The heat treatment method is: quenching and tempering HB220-270; hard chrome plating HRC> 55.
(3) Nitrided steel and 38CrMoAl, which is also the materials of screw barrel, has relatively good comprehensive functions, and its application functions are also relatively wide. Generally, the nitride layer is 0.4 to 0.6 mm. However, this material has relatively low resistance to hydrogen chloride corrosion and is relatively expensive. The heat treatment method: quenching and tempering HB220-270; nitriding HRC> 65.
2. Material requirements for twin screw barrel screws
We know from the extrusion process that the screw runs under the environment of high temperature, certain corrosion, strong wear and high torque. Therefore, the screw barrel screw must meet the following requirements:
(1) High temperature resistance, no deformation under high temperature;
(2) Wear resistance and long service life;
(3) Corrosion resistance, the material is corrosive;
(4) High strength, withstand large torque and high speed;
(5) It has a good cutting function.
(6) After heat treatment, the residual stress is small and the thermal deformation is small.
