Publish Time: 2023-12-20 Origin: Site
A twin screw extruder barrel experiences significant wear over time from the rotating screws, heat, and abrasive materials passing through. Understanding the causes of barrel wear and taking steps to minimize it can extend the life of your extruder barrel.In the process of compounding extrusion production, various chemical additives are often added to improve the overall performance of the products. However, this practice can lead to increased wear and corrosion of the twin-screw extruder screw and barrel. This not only results in a significant waste but also affects the quality of extrudates , and may even directly lead to machine shut-down.
The main causes of barrel wear are:
Abrasion from the screw flights rubbing against the barrel surface
Erosion from materials passing through, especially abrasive fillers and reinforcements
Corrosion from reactive chemicals at high temperatures
Fatigue from thermal stresses during heating/cooling cycles
The feed section sees the most wear as materials enter the barrel. Wear gradually decreases further along the barrel as the melt becomes more homogenous.
There are several strategies to reduce barrel wear:
Use wear-resistant steel alloys, coatings, or liners in high wear areas
Optimize screw design to minimize clearance between screw flight and barrel
Introduce materials gradually to disperse abrasive particles
Use barrel cooling to keep temperatures below material limits
Clean the barrel regularly to remove abrasive residue
Lubricate screws and barrels with non-reactive materials
Proper screw design and compatible materials are key to minimizing abrasive wear.
As a professional twin screw extruder manufaturer, we will share some effective methods to enhance the wear resistance of twin-screw extruders barrels and how to repaire once worn.Let's first look at the wear-resistant treatment for the screw and barrel:
Nitriding technology is currently divided into three main types: ion nitriding, gas nitriding, and liquid nitriding. Among them, ion nitriding has the best effect,which will extend screw service life by 2 to 3 times compared to gas nitriding. In modern metal surface treatments, ion nitriding is a common and widely used technique. It is a chemical heat treatment method, and after ion nitriding treatment, the hardness of the metal surface, such as carbon steel, stainless steel, alloy steel, and powder steel, can be significantly increased. This process also improves burn resistance, corrosion resistance, fatigue strength, and wear resistance.
Chromium and molybdenum plating also play a significant role in improving the wear resistance of twin-screw extruder screws and barrels. Currently, there are various methods for chromium plating, such as black chromium plating, white chromium plating, hard chromium plating, and decorative chromium plating, each achieving different functional effects. In the wear-resistant treatment of twin-screw extruder screws and barrels, hard chromium plating is mainly used to increase the hardness of the barrel, thereby enhancing its wear resistance.
Pratically, it is recommended to use 45# steel or 40Cr steel for the screw material. The thickness of the chromium layer should be at least 0.05mm but should not exceed 0.2mm. After treatment, the internal surface of the barrel can maintain good cleanliness, corrosion resistance and wear resistance as well as improved chemical stability. In addition to chromium plating, spraying a molybdenum layer on the surface can also significantly improve the corrosion resistance and wear resistance of the barrel, effectively reducing wear caused by various reasons during the production process. The main process involves nitrogenizing the steel screw material, nitrogenizing treatment, and plasma spraying.
Build-up alloy involves welding one or more layers of alloy on the top or entire surface of the screw, with each layer having a thickness of 1.5 to 2mm. The base material can be the entire screw or its components. Welding methods may include arc welding, submerged arc welding, plasma argon arc welding, etc. The screw components should undergo preheating treatment at 550 to 600°C before welding, and a 1mm transition layer of high plasticity and toughness, such as Cr25Ni13 or Ni112, should be pre-deposited. After welding, quickly anneal the screw in an SCr-5-10 electric furnace to relieve stress, and then grind the build-up layer.
Next article,we will take a look at how to repair and maintain the screw and barrel of the extruder.