Analysis of Common Materials for Screw and Barrel: Performance, Application and Selection Recommendations
As core components of injection molding machines and extruders, the material selection of screw and barrel directly determines the service life, processing performance and product quality of the whole machine. In practical applications, different working conditions and different plastic raw materials have different requirements for the materials of screw and barrel. This article will analyze several common material types and their applicable scenarios from a professional perspective for reference by industry insiders.
- Introduction to Screw Materials
The screw is mainly subjected to multiple working conditions such as high temperature, high pressure, high shear and corrosion. Commonly used materials are as follows:
^ 38CrMoAlA (alloy quenched and tempered steel)
Features: High cost performance, the most widely used material, with good hardenability and toughness.
Heat treatment method: quenching and tempering + nitriding (surface hardness can reach HV950~1050).
Service life: about 1~2 years under normal use.
Applicable raw materials: ordinary plastics such as PP, PE, PS, etc.
^ 42CrMo (medium carbon alloy steel)
Features: high strength, good toughness, suitable for large diameter or high torque conditions.
Heat treatment method: quenching and tempering, surface nitriding can also be added.
Scope of application: suitable for screw designs with special requirements for torque.
^ SKD61 (hot working die steel imported from Japan)
Features: high temperature resistance, strong heat fatigue resistance, can withstand long-term operation at high temperatures.
Hardness: hardness HRC 48~52 after heat treatment.
Applicable scenarios: engineering plastics, glass fiber or mineral filling materials.
High wear-resistant alloy screw (double alloy spray coating)
Features: surface spray alloy layer (such as Ni-Cr-B-Si system), thickness 0.51.5mm, hardness up to HRC 6065.
Service life can reach more than 3~5 years.
Applicable raw materials: PVC, high corrosion and high wear plastics containing glass fiber/mineral powder/flame retardant.
- Barrel Material Analysis
As a fixed outer shell, the barrel is mainly subjected to internal pressure and material wear and corrosion. The following are common materials:
^ 38CrMoAlA (quenching and tempering + nitriding)
Advantages: high cost performance, moderate wear resistance.
Disadvantages: general corrosion resistance, not suitable for highly corrosive raw materials.
Dual alloy barrel (bimetallic sleeve)
Inner wall centrifugal casting alloy layer, commonly used materials such as Fe-based, Ni-based, Co-based alloys.
Hardness: HRC 60-65, thickness 1.5-2.5mm.
Features: significantly improve wear resistance and corrosion resistance, widely used in high filling or special plastic processing.
Service life: usually 2~5 times that of ordinary barrels.
^ Integral alloy steel barrel (for special industries)
For example, medical and food-grade plastic equipment requires no pollution, and stainless steel or special coatings (such as PTFE) may be used.
- Material selection suggestions and precautions
Ordinary plastic processing (such as PE, PP, ABS): It is recommended to use 38CrMoAlA nitrided material, which is economical and practical.
Engineering plastics, high-filling materials: Use double alloy screw/barrel, which can greatly improve wear resistance and reduce maintenance frequency.
PVC processing: Because it contains chlorine and is highly corrosive, a special corrosion-resistant alloy layer is required.
Glass fiber filled materials: It is recommended to use a high chromium-nickel double alloy spray coating to prevent increased wear.
- Conclusion
The selection of screws and barrels may seem like details, but it is actually related to the stable operation of the equipment and the production cost control of the enterprise. Reasonable material configuration not only prolongs the service life, but also improves product quality and production efficiency. When selecting materials, factors such as raw material type, frequency of use, processing temperature and maintenance cycle should be considered comprehensively.
If you have any questions during material selection or use, please contact us via WhatsApp or email, and we will provide you with professional technical support and supporting solutions.
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