The material of used extruder screws varies and depends primarily on the original design of the equipment and the materials intended for processing.
The most common and widely used material for screws is 38CrMoAlA (a chromium-molybdenum-aluminum alloy steel). In addition, depending on specific performance requirements, there are various other high-performance materials available.
| Material Type | Typical Grades | Key Features | Key Use Cases |
| Common materials | 38CrMoAlA | It offers excellent overall performance and, after nitriding treatment, exhibits high surface hardness (up to HV900 or higher), as well as wear and corrosion resistance, making it the most widely used material for screws. | It is suitable for the extrusion processing of most common plastics and is the most common type found on the second-hand market. |
| Highly wear-resistant / Reinforced | W6Mo5Cr4V2 (high-speed steel) | Extremely high hardness (up to HRC 60 or higher) and excellent wear resistance, making it suitable for handling highly abrasive or high-wear materials | Extruders specifically designed for processing highly abrasive plastics containing glass fibers, mineral fillers (such as calcium carbonate), and other similar materials |
| Highly corrosion-resistant | 9Cr18MoV | It offers excellent corrosion resistance and can withstand corrosive gases generated by the decomposition of materials (such as PVC) and flame retardants. | For processing corrosive plastics such as PVC, or in situations where corrosive additives such as flame retardants must be added during production. |
| Extended-life | Bimetal/Coating Treatment | On standard substrates (such as 45# steel), applying a wear- and corrosion-resistant alloy coating (such as nickel-based alloys or tungsten carbide) through spraying or lining increases costs but significantly extends service life. | Suitable for large-scale, high-intensity continuous production, where equipment stability and longevity are of the utmost importance. |
| Entry-level | No. 45 steel | It is inexpensive and easy to machine, but its wear and corrosion resistance are relatively poor. | This is commonly found in extruders used for early-stage production or those processing low-grade, non-corrosive plastics; when inspecting used equipment, special attention should be paid to the condition of wear and tear. |
It is important to note that even if the screw material itself is wear-resistant, the rate of wear will still increase significantly when processing materials containing fillers such as glass fiber or calcium carbonate.