Twin screw extruder consists of many components, among which the screw is a critical component. Its quality directly affects the extrusion effect.
The commonly used screw materials in China are 45# steel, 40Cr, nitrided steel, 38CrMOAl, and high temperature alloy.
45# steel is cheap with good machinability, but poor wear and corrosion resistance. Heat treatment: quenching and tempering HB220~270, high frequency quenching HRC45~48.
40Cr has better performance than 45# steel, but often needs to be plated with chromium to improve its corrosion and wear resistance. However, the requirements for the chrome plating are high. If the coating is too thin, it is easy to wear, and if it is too thick, it is easy to peel off, which will accelerate corrosion after peeling off, so it has been applied less. Heat treatment: quenching and tempering HB220~270, hard chrome plating HRC＞55.
Nitrided steel and 38CrMoAl have better comprehensive performance and are widely used. The nitride layer is generally 0.4~0.6mm. However, this material has poor resistance to hydrochloric acid corrosion and is expensive.
High temperature alloy material is better than other materials. This material does not need coating and is mainly used for the halogen-free screw of injection molding machine. It has high oxidation resistance and corrosion resistance.
The co-rotating twin-screw has a shared structure. The characteristic is that convex platforms or mirror pins are milled or installed on the screw, and divergent grooves or orifices are opened. The machine with this screw has high plasticizing efficiency, uniform mixing, and good product quality, and has been widely used both domestically and internationally.
The barrier type screw has a structure feature that a "barrier" is set at a certain position on the screw to hinder the solid phase of the material from passing through and promote the solid phase melting. The simplest one of barrier screws is to configure a barrier mixing element at the head of a regular screw. It is mainly used for polyolefin materials.
The variable channel screw has a structure feature that the cross-sectional shape or area of the screw channel changes with an angle variation. Its representative is the wave screw. Because the compression, shear, and relaxation of this screw are relatively frequent, it is not suitable for processing thermal sensitive plastics. Although the twin-groove screw is difficult to manufacture, its plasticizing and mixing quality is good and it is suitable for difficult-to-process plastics with high plasticizing efficiency.
Nanjing KY Chemical Machinery Co., Ltd. not only provides customers with first-class extruders but also helps customers optimize the entire production system.
From material storage, drying, transportation, metering, mixing to final product packaging, we provide customers with a set of high reliability and cost-effective solutions equipped with a factory-level intelligent control system. Welcome to consult us.
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