Abrasive: How is brown corundum made?


EOG Member
The amount of aluminum sulfide produced depends on the amount of pyrite added. The melting point of brown molten alumina decreases with the increase of aluminum sulfide content. The shape of corundum crystal is closely related to the content of aluminum sulfide in furnace liquid. When the content of aluminum sulfide in the melt is close to 4%, the corundum crystallized from the melt is mainly equiaxed, and the particle shape is particularly good.​
When the content of aluminum sulfide in the melt is 6.5%, there are fine particles besides equiaxed grains. The various compounds in aluminates are bound together in the form of particles. All kinds of oxides can not be separated by visual inspection. Due to different chemical composition and different cementitious materials, the color of white alumina varies greatly, mainly gray, brown and brown.​
For example, Pingguo deposit in Guangxi is dark gray, Henan and Shanxi mines are gray, Guizhou bauxite deposit is white and light gray, Shandong Tianzhuang bauxite deposit is chlorite. The smoke exhaust hood is the main method to remove smoke from corundum furnace. brown fused alumina manufacturer That is, a large smoke exhaust hood is arranged above the furnace body. In this way, the black alumina crown cover is mainly composed of furnace cover, chimney and furnace cover. The upper cover of the furnace is a double-layer structure welded by 6-8mm steel plate.​
The middle interlayer can pass through cooling water and be provided with ventilation hole to prevent explosion accident caused by expansion of superheated steam. The side wall of furnace cover is welded by steel plate and lining refractory brick. According to the way of dust removal, dust purification equipment can be divided into two categories: wet and dry. The quality assessment of pink alumina is now usually carried out by the bar method.​
Stick is judged from two aspects. On the one hand, it has rod-shaped color and crystal luster. The color is white, with shiny crystal stars better. The color is very dark and the quality is not good. It is necessary to extend the melting time of raw SiC. On the other hand, look at the thickness of the rod. Sparse pass and rough pass indicate that the furnace temperature is low and it takes some time. Before stopping the heating furnace, the thickness of the rod sample is 1.5 ~ 2.5mm. This is normal. If the thickness is greater than 3 mm, the sample is too thick.​
Generally speaking, the surface layer of alumina sand has low strength, and the quality of different parts of crystal tube is also different. Generally, the less SiC content in the outer layer, the smaller the crystal size. Use a gradient shovel to remove amorphous silicon carbide and secondary silicon carbide at the same time; clean the transistors, then manually shovel the fine crystals into a pile, lift them with a grab, and store them in a centralized memory for crushing and processing.​
So far, the end point of white corundum smelting has not been based on strict judgment. corundum wholesale The current should be reduced gradually, the power should be reduced gradually, and the furnace should be closed slowly. The black silicon carbide is cooled naturally after shutdown. Cool it slowly for a period of time to allow enough time for sodium perchlorate to crystallize and precipitate, and finally concentrate in the middle and upper part of the frit. The frit can then be cooled quickly with water.​