According to foreign data reports, one of the problems often encountered in extrusion and injection molding of plastic products is the rapid wear and corrosion of screw barrel. In many cases, the screw barrel is worn and corroded to the point that it needs to be replaced in about half a year, even in two or three months, which forces the plastic molding industry to conduct more and more in-depth research on the strengthening measures of wear and corrosion resistance of screw barrel.
In recent three years, in order to improve the wear and corrosion resistance of screw barrel, great progress has been made in the research on the wear and corrosion strengthening measures of screw barrel. It is mainly reflected in the development of new materials for manufacturing screw barrel, and the transplantation of new mechanical manufacturing technology and new heat treatment technology into the manufacturing process of screw barrel.
The brief information in this regard is as follows:
1. In the 1950s, medium carbon steel and alloy steel were mainly used for surface quenching, chromium plating or chromium plating after quenching.
2. Then, alloy steel, nitrided steel and other materials are mostly used for gas nitriding treatment.
3. After entering the 1970s, in addition to the continuous use of nitrided steel for gas nitriding treatment, more and more ion nitriding processes were used, and the chromium plating processes of medium carbon steel and alloy steel were significantly increased.
4. The new technology of spray coating and surfacing wear-resistant and corrosion-resistant alloy on the top surface of the tooth edge of the extruder screw, even the spiral surface of the whole extruder screw, is widely used. In some special cases, pure nickel is used to manufacture the screw.
5. For the barrel, the new process of manufacturing the barrel body with cast iron, medium carbon steel or alloy steel, and then casting the inner hole wall with wear-resistant and corrosion-resistant special alloy lining is widely used.
Corrosive, abrasive and high temperature resistant resins may unknowingly damage the screw and barrel. For example, some engineering materials, thermoplastic elastomers and biopolymer materials sometimes form a corrosive environment. In addition, reinforcing materials (such as glass fiber, glass ball, etc.), some fillers and additives are abrasive.
In order to avoid affecting production efficiency and product quality, processors must closely monitor the hazards that these materials may cause to the equipment. In order to maintain high processing standards, it is necessary to establish a preventive maintenance scheme. When necessary, the extruder screw and barrel should be checked and measured, and the screw should be pulled out for re installation or replacement, because minimal wear will also affect the product quality.
The best way to protect the equipment from corrosive and abrasive resins is to select appropriate materials to manufacture screws and barrels. In order to deal with corrosive, abrasive and high temperature resistant melts, the manufacturing cost of wear resistant barrel and extruder screw is about 3 ~ 4 times higher than that of standard polyolefin screw. This is because wear resistant alloys are expensive and difficult to process. However, they can provide longer service life and longer maintenance intervals.