Graphite electrode refers to a high-temperature resistant graphite conductive material made from petroleum coke and asphalt coke as aggregates, coal tar as binder, through raw material calcination, crushing and grinding, batching, mixing, molding, calcination, impregnation, graphitization and mechanical processing. It is called artificial graphite electrode (referred to as graphite electrode), which is different from natural graphite electrode prepared from natural graphite as raw material.
Graphite electrodes are mainly made from petroleum coke and needle coke as raw materials, with coal tar pitch as a binder. They are made by calcination, batching, mixing, molding, roasting, graphitization, and machining. They are conductors that release electrical energy in the form of an arc in an electric arc furnace to heat and melt the furnace material. According to their quality indicators, they can be divided into ordinary power graphite electrodes, high-power graphite electrodes, and ultra-high power graphite electrodes.
The main raw material for the production of graphite electrodes is petroleum coke. A small amount of asphalt coke can be added to ordinary power graphite electrodes, and the sulfur content of both petroleum coke and asphalt coke cannot exceed 0.5%. Needle coke is also required when producing high-power or ultra high power graphite electrodes. The main raw material for the production of aluminum anodes is petroleum coke, and the sulfur content is controlled to be no more than 1.5% to 2%. Petroleum coke and asphalt coke should comply with relevant national quality standards.
The advantage of Graphite electrode
(1) The increasing complexity of mold geometry and the diversification of product applications have led to higher requirements for the discharge accuracy of spark machines. The advantages of graphite electrodes are that they are easy to process, have a high discharge machining removal rate, and have low graphite loss. Therefore, some group based spark machine customers have abandoned copper electrodes and switched to graphite electrodes. In addition, some special shaped electrodes cannot be made of copper, but graphite is easier to form, and copper electrodes are heavier and not suitable for processing large electrodes. These factors have led some group based spark machine customers to use graphite electrodes.
(2) Graphite electrodes are easier to process and have a significantly faster processing speed than copper electrodes. For example, using milling technology to process graphite is 2-3 times faster than other metal processing and does not require additional manual processing, while copper electrodes require manual grinding. Similarly, if high-speed graphite machining centers are used to manufacture electrodes, the speed will be faster, the efficiency will be higher, and there will be no dust problem. In these machining processes, selecting tools with appropriate hardness and graphite can reduce tool wear and damage to copper electrodes. If we compare the milling time between graphite electrodes and copper electrodes, graphite electrodes are 67% faster than copper electrodes. In general, in electrical discharge machining, using graphite electrodes is 58% faster than using copper electrodes. In this way, processing time is significantly reduced, while manufacturing costs are also reduced.
(3) The design of graphite electrodes is different from that of traditional copper electrodes. Many mold factories usually have different reserve amounts for rough and fine machining of copper electrodes, while graphite electrodes use almost the same reserve amount, which reduces the number of CAD/CAM and machine processing times. This alone is enough to greatly improve the accuracy of mold cavities.
The application of Graphite electrode
(1) Used for electric arc steelmaking furnace
Electric furnace steelmaking is a major user of graphite electrodes. The production of electric furnace steel in China accounts for about 18% of the crude steel production, and graphite electrodes used in steelmaking account for 70% to 80% of the total amount of graphite electrodes used. Electric furnace steelmaking is the process of using graphite electrodes to introduce current into the furnace, and utilizing the high-temperature heat source generated by the arc between the electrode end and the furnace charge for smelting.
(2) Used for mineral thermal electric furnaces
Mineral thermal electric furnaces are mainly used for the production of industrial silicon and yellow phosphorus. Their characteristic is that the lower part of the conductive electrode is buried in the furnace material, forming an arc in the material layer, and using the heat energy emitted by the resistance of the furnace material itself to heat the furnace material. Among them, mineral thermal electric furnaces with high current density require graphite electrodes. For example, about 100kg of graphite electrodes are consumed for producing 1 ton of silicon, and about 40kg of graphite electrodes are consumed for producing 1 ton of yellow phosphorus.
(3) Used for resistance furnaces
The graphitization furnace used for producing graphite products, the melting furnace used for melting glass, and the electric furnace used for producing silicon carbide all belong to resistance furnaces. The materials inside the furnace are both heating resistors and objects to be heated. Usually, graphite electrodes for conductivity are embedded in the furnace head wall at the end of the resistance furnace for discontinuous consumption of graphite electrodes.
(4) Used for preparing irregular graphite products
The blank of graphite electrodes is also used for processing into various shaped graphite products such as crucibles, molds, boats, and heating elements. For example, in the quartz glass industry, for every 1 ton of electric melting tube produced, 10 tons of graphite electrode blanks are required; for every 1 ton of quartz brick produced, 100 kilograms of graphite electrode blanks are consumed.
