Graphite is an allotrope of carbon. It is a gray-black, opaque solid with stable chemical properties, corrosion resistance, and is not easy to react with chemicals such as acids and alkalis. Natural graphite comes from graphite deposits, and can also be made into artificial graphite by using petroleum coke, pitch coke as raw materials after a series of processes.
Molded graphite products have good electrical conductivity, high temperature resistance, corrosion resistance, high purity, self-lubrication, thermal shock resistance, isotropy, and easy precision machining. Molded graphite is widely used in aerospace, solar photovoltaic and semiconductor, continuous casting, cemented carbide and electronic mold sintering, electric spark, glass, medicine and other industries. The commonly used pressing methods in the carbon and graphite product industry are extrusion and molding.
The molding method used in molded graphite is to put a certain amount of paste into a mold with the required shape and size and then pressurize it from the top or bottom. Sometimes a certain pressure is applied to the paste from both the upper and lower directions at the same time, so that the paste is compressed in the mold and formed. The pressed semi-finished product is then demolded and cooled for inspection and then is stacked. The molding equipment includes vertical presses and horizontal presses. By the molding method, it generally can only press one product at a time, and the production efficiency is relatively low. But it can make some products that cannot be made by extrusion method. Molded graphite has a very wide range of properties in terms of mechanical strength, friction resistance, density, hardness, electrical conductivity, etc., and can be further enhanced by impregnation with resin or metal.
The extrusion method used to extruded graphite block is to put the paste into the paste cylinder of the press for extrusion. A replaceable extrusion nozzle (according to the cross-sectional shape and size of the product) is installed in front of the press. There is a movable baffle in front of the extrusion nozzle, and behind the paste cylinder is the main plunger of the press. Before pressurizing, Put a baffle on the mouth, and when pressurizing, make the pressure move forward to discharge and compress. When removing the baffle and continuing to pressurize, the paste will be extruded from the mouth of the extrusion nozzle. Cut the extruded strips into required lengths. After cooling it down, harden and then stack it. Extruded graphite is semi-continuous production, that is, after adding a certain amount of paste, several products (graphite blocks, graphite materials) can be continuously extruded, therefore, the production efficiency of the extrusion method is much higher than that of the molding method. Most carbon and graphite products are currently produced by extrusion. Molded graphite is often used to produce cold-pressed graphite with smaller size or products with finer structures.