Silicon carbide (SiC) is made of quartz sand, petroleum coke (or coal coke) and wood chips as raw materials through high temperature smelting in a resistance furnace. There are two main smelting methods. The following will take you to find out.
The smelting method of silicon carbide:
1. New material method
The new materials (silica sand, petroleum coke) are directly loaded into the reaction zone of the furnace for smelting. The principle of roasting material is to load the new material at the bottom of the furnace and the heat preservation areas on both sides for roasting, and then put the obtained roasting material into the reaction zone of the next furnace for smelting.
2. Roasting method
It is divided into two kinds. One is the method of only loading the new material at the bottom of the furnace for roasting, which is the method adopted by many factories in China. The other is to load the new material on the bottom and both sides of the furnace for simultaneous roasting, which is called the full roasting material method. There are few factories using this method.
The quality of the raw materials in the new material method has little fluctuation, and the formula of the charge is relatively stable, so the quality of the product is also relatively stable. The roasting material method uses the temperature in the furnace to partially remove the volatiles in the new material in the roasting material area, so that the silica sand and the petroleum coke are polymerized into porous particles with good air permeability. The roasting material of the green furnace also contains a certain amount of salt diffused from the reaction material. Using the roasting material to return to the furnace can increase the output of the furnace, reduce the power consumption of the unit product, and can reduce or not use wood chips. When preparing the reaction material for the green furnace, less salt can be added than the new material method. The tangent point of the roasting material method is that the transportation volume of the charge is large, and the composition fluctuates greatly, which increases the workload of sampling and analysis, and the formula of each furnace must be changed.
According to the purity of silicon carbide, it is mainly divided into black silicon carbide and green silicon carbide, and their uses are also different.
1. Black silicon carbide contains about 98.5% SiC, and its toughness is higher than that of green silicon carbide. It is mostly used for processing materials with low tensile strength, such as glass, ceramics, stone, refractory materials, cast iron and non-ferrous metals. Green silicon carbide contains more than 99% SiC and has good self-sharpening properties.
2. In addition, there is a special variety in silicon carbide, which is cubic silicon carbide, which is a specially made yellow-green crystal, which is mostly used in the finishing industry, such as the processing of bearings, with good micromachining effect.
Because of its stable chemical properties, high thermal conductivity, small thermal expansion coefficient and good wear resistance, silicon carbide has many other uses besides abrasives, such as: coating silicon carbide powder on turbine impellers or cylinder blocks by a special process. The inner wall can improve its wear resistance and prolong the service life by 1 to 2 times; the high-grade refractory used to make it is resistant to shock, small in size, light in weight and high in strength, and has good energy-saving effect.
Silicon carbide has high hardness and excellent thermal conductivity. It is a semiconductor and can resist oxidation at high temperatures.
