Graphite electrode is made of petroleum coke, needle coke and coal pitch, through calcining、batching、kneading、forming、baking、Impregnation, graphitizing and machining.
Calcining: When carbonaceous raw materials undergo heat treatment at high temperature, they discharge their moisture and volatiles, and the production process to improve their physical and chemical properties is called calcination. In general, carbon materials are calcined with gas and its own volatiles as heat source, the highest temperature is 1250-1350℃.Calcining causes profound changes in the structure and physical and chemical properties of carbon materials. It is mainly reflected in improving the density mechanical strength and electrical conductivity of coke, improving the chemical stability and oxidation resistance of coke, and laying a foundation for subsequent processes.
Raw material crushing treatment and ingredients: Before batching, the bulk coke and needle coke should be sieved.
Batching: Batching is the process of weighing and focusing the aggregate and powder binders of various sizes according to the formulation requirements. Scientific formulation and stability of batching operation are one of the most important factors affecting product quality and performance.
Kneading: At a certain temperature, the quantitative carbonaceous granules and powders were mixed with the quantitative binders.
Forming: The forming of carbon material refers to the process of forming a blank with a certain shape, size, density and strength by the plastic deformation of the mixed carbon paste under the external force applied by the forming equipment.
Baking: Baking is a process of carbonization of coal bitumen in the blank of carbon products under the protection of the filler. The bituminous coal tar formed after carbonization solidifies the carbon aggregate and powder particles together, and the carbonized coal products have higher mechanical strength, lower resistivity, better thermal stability and chemical stability. Baking is one of the main processes in the production of carbon products, and also an important part of the three heat treatment processes in the production of graphite electrode. The production cycle of baking is longer and the energy consumption is higher. The quality of raw blank baking has a certain impact on the quality of finished products and production cost.
Second baking: Second baking is the process of carbonizing the bitumen in the interstices of the baking products after being impregnated. The raw materials of the electrodes and joints which require higher volume density shall be roasted twice, and the raw materials of the joints shall be roasted three times or two times.
Impregnation: Impregnation is a process of immersing liquid impregnation bitumen into the pores of the electrode under certain temperature and pressure when carbon material is placed in the pressure vessel. The aim is to reduce porosity, increase bulk density and mechanical strength, and improve electrical and thermal conductivity of the electrode.
Graphitization: Graphitization refers to the high temperature heat treatment process in which carbon products are heated above 2300 degrees Celsius in the protective medium in the high temperature electric furnace to transform the amorphous layer carbon into three-dimensional ordered graphite crystal structure.
Machining: Machining relies on machining to achieve the required dimension, shape, accuracy for the electrode body and joint.