The extruder barrel screw can be known in the extrusion process that the barrel screw is working under high temperature, corrosion, intense wear, and high torque. There are three common heating methods, but the more commonly used heating method is resistance heating.
(1)Resistance heating method
It allows current to pass through a wire with a relatively large resistance (resistance wire), thereby generating heat and then conducting it to the material through the extruder barrel wall.
(2)Electric induction heating method
The outer circumference of the cylinder of the extruder is equipped with a coil, and a magnetic silicon steel sheet is installed on the periphery of the coil. When current flows through the coil, the silicon steel sheet and the barrel form a closed magnetic circuit. The alternating magnetic flux induces the barrel to generate current, and the barrel generates heat due to a certain resistance value.
(3) Heating medium heating method
This heating method refers to heating the barrel with water vapor or oil as the heating medium. Steam needs to be transported by boiler equipment and pipelines, and electric resistance heaters are used to heat oil. Both types of heating equipment are relatively complicated, costly, and difficult to control temperature, so they are rarely used today.
According to reports, a problem frequently encountered when processing plastic products by extrusion and injection molding is the rapid wear and corrosion of the screw and barrel. In most cases, the screw and barrel are worn and corroded to the point where they need to be replaced in about half a year, even within two or three months. This forces the plastic molding and processing industry to conduct more and more in-depth discussions on strengthening measures for wear resistance and corrosion resistance of the screw and barrel.
In recent years, in order to improve the wear resistance and corrosion resistance of the screw and barrel of the extruder, great progress has been made in the study of corrosion-resistant strengthening measures for the screw and barrel. This is manifested in the research and development of new raw materials for the production of screws and barrels, and the transplantation of new mechanical manufacturing technology and new heat treatment technology to the manufacturing process of screws and barrels.
A simple situation in this regard: In the 1950s, medium carbon steel and alloy steel were selected for surface quenching, chromium plating, or chromium plating after quenching. After that, alloy steel, nitrided steel and other materials are often used for gas nitriding treatment.
After entering the 1970s, in addition to continuing to use more nitrided steel for gas nitriding treatment, more and more methods such as nitriding have been used. The process of selecting medium carbon steel and alloy steel for chromium plating has been significantly added. The new technology of wear-resistant and corrosion-resistant alloy is widely used for spraying and surfacing the top surface of the screw ridge of the extruder, and even the entire screw spiral surface. In some special cases, pure nickel is used to make the screw.
For the extruder barrel, cast iron, medium carbon steel or alloy steel is widely used to make the barrel body. Then the inner wall of the hole is cast with a new process of wear-resistant and corrosion-resistant special alloy materials.