There are generally three molding methods used in the carbon industry, namely compression molding, extrusion molding, and vibration molding methods. Among them, the compression molding method is low due to labor productivity. At present, except for a small number of products with special requirements that use this molding method, the molding process in the carbon industry has basically been withdrawn. From the perspective of my country and the world, the extrusion molding method is the main molding method in the carbon industry. The graphite electrode formed by this method has preferential orientation in the axial direction, which makes the various “physical-mechanical” parameters in the axial direction of the product better than other directions, which is suitable for the use conditions of graphite electrodes and has high labor productivity. However, in order to produce large-diameter graphite electrodes or other carbon products with large cross-sections, a large-tonnage hydraulic press must be used when using this molding method. At present, the production of graphite electrodes with φ400mm in our country generally uses a 2500t hydraulic extruder, and the production of graphite electrodes with a diameter of 500mm or more uses a 3500t hydraulic extruder. Some foreign manufacturers of graphite electrodes also commonly use 4000t and 6000t hydraulic extruders, and the largest hydraulic extruder may be the 12700 hydraulic extruders of National Carbon Co. of the United States. These equipment not only have high extrusion pressure but also have a very long body due to the requirements of the electrode extruder’s molding method, so the bodyweight is very large. For example, a 3550t hydraulic extruder made in the Soviet Union is 36m long and weighs 577t. A 6300t hydraulic extruder made in Austria weighs 700t. In addition, these devices are equipped with high-power main motors, generally 300~400kW. It is conceivable that such equipment requires a large amount of investment and high energy consumption, which is not affordable by ordinary small and medium-sized factories.
Since the French VAW company vigorously introduced the vibration forming method in the 1960s, it has been widely used in the aluminum carbon industry, especially in the production of prebaked anodes, and has gradually been extended to the production of cathode carbon blocks and graphite electrodes. The vibration molding machine used in this molding method has a simple structure, a compact body, a small weight, and a low cost. According to the estimation of the French company KHD, the investment of a vibration forming machine is about 40% of that of a corresponding hydraulic extruder. The total power of the motor is only 37% of that of the extruder, and the molding energy consumption of the product is only 32% of that of the extruder. For some simple vibration forming machines in our country, the investment for one is only about 200,000 yuan, which is only about 5% of the 2500t extruder. Although its labor productivity and single-unit capacity are lower, it can also be used for the molding of large graphite electrodes with diameters above φ300mm and even φ500mm or larger. This is exactly what the small and medium-sized carbon plants hope for.
Although the vibration forming machine has many advantages mentioned above, can high-quality products be obtained by using it for the forming of graphite electrodes? At least can you get products that meet the standards? For this, most people in my country’s carbon industry hold a negative attitude. It is mainly believed that the particles in the vibration molded product are preferably oriented along the transverse direction, which is a bad orientation for graphite electrodes. Secondly, it is considered that the volume density of vibration molded products is not uniform. Because the above two points will affect a series of physical and mechanical properties of the product, people’s denial or suspicion is not unreasonable.
Based on everyone’s skepticism, some people conducted relevant discussions and analyses and finally came to the following conclusions.
1) Vibration molding, as a molding method for producing graphite electrodes, can produce ordinary graphite electrodes that are suitable for my country’s current national standard GB3072-82.
2) If the vibration hydroforming method is adopted, ordinary graphite electrodes of better quality can be produced, and the bulk density can reach more than 1.60g/cm3. If it is combined with vacuuming during the molding process, its bulk density can be further increased.
3) Since the graphite electrode formed by vibration has a higher volume density and a lower porosity, oxidation consumption can be reduced during use.
4) Due to the random orientation of the particles of the vibration-shaped electrode, its physical-mechanical properties have similar values in the axial and radial directions. Therefore, when the axial resistivity is similar to that of the extruded electrode, its radial physical-mechanical parameters are better than those of the extruded electrode.
5) The vibration forming machine, especially the small simple vibration forming machine, has little investment, but it can produce large-diameter graphite electrodes and other large-section graphite products. Moreover, its technology is easy to master, and the forming yield is high, which is suitable for small and medium carbon factories.
6) Although the vibration forming method has been developed in my country since the end of the 1960s. However, it has not been mass-produced for many years, and most manufacturers are limited to using it to produce carbon blocks and regenerated graphite electrodes. Many people hold negative attitudes about whether it can be used in the production of graphite electrodes. Therefore, a lot of work needs to be done. Only when the electrodes produced by them are proved to be at least no worse than extruded electrodes in long-term and large-scale use, can this molding method be recognized by the carbon industry in my country.
The author puts forward a little work and some opinions on the vibration forming method for the reference of colleagues. I also hope to get criticism and corrections from my colleagues. This article is from the Internet. If there is something wrong, please contact the author of this website to delete or modify it. Learn more about the graphite electrode production process.