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Silicon Carbide Craftsmanship

Hangzhou JWG Technology Co.Ltd | Updated: Sep 08, 2017

Silicon carbide (SiC) is made of quartz sand, petroleum coke (or coal), wood chips (need to add green silicon carbide when adding salt) and other raw materials through the resistance furnace high temperature smelting. Silicon carbide in nature also has rare minerals, mozzanite. Silicon carbide, also known as carbon silica. In the contemporary C, N, B and other non-oxide high-tech refractory raw materials, silicon carbide is the most widely used, the most economical one, can be called gold sand or refractory sand. At present, China's industrial production of silicon carbide is divided into black silicon carbide and green silicon carbide two, are hexagonal crystals, the specific gravity of 3.20 ~ 3.25, micro hardness of 2840 ~ 3320kg / mm2.

Substance species

Silicon carbide black silicon carbide and green silicon carbide two commonly used basic varieties, are α-SiC. ① black silicon carbide containing about 95% SiC, its toughness is higher than the green silicon carbide, mostly used for processing tensile strength of low materials, such as glass, ceramics, stone, refractory materials, cast iron and nonferrous metals. ② green silicon carbide with about 97% SiC, self-sharpening, and most used for processing carbide, titanium and optical glass, but also for honing cylinder liner and grinding high-speed steel cutting tools. In addition to cubic silicon carbide, which is made in a special process of yellow-green crystals, for the production of abrasive for the super-finishing of the bearing, the surface roughness can be raised from Ra32 ~ 0.16 microns to Ra0.04 ~ 0.02 microns.

Craftsmanship

Due to the small natural content, silicon carbide is mostly man-made. The common method is to mix quartz sand with coke, the use of silica and petroleum coke, add salt and wood chips, into the electric furnace, heated to about 2000 ° C high temperature, after a variety of chemical processes to get silicon carbide powder The

Silicon carbide (SiC) because of its great hardness and become an important abrasive, but its application is more than the general abrasive. For example, it has the high temperature resistance, thermal conductivity and become a tunnel kiln or shuttle kiln preferred kiln materials, it has the conductivity to make it an important electric heating elements. Preparation of SiC products First of all to prepare SiC smelting block [or: SiC particles, containing C and superhard, so SiC particles have been called: emery. But note that it is different from the composition of natural emery (also known as garnet). In industrial production, SiC smelting block is usually quartz, petroleum coke as raw material, auxiliary recovery material, material, after grinding and other processes into a reasonable proportion and reasonable size of the charge (in order to adjust the permeability of the charge need to add appropriate Of the wood chips, the preparation of green silicon carbide, but also add the amount of salt) prepared by high temperature. High temperature preparation of SiC smelting block thermal equipment is a dedicated silicon carbide furnace, the structure from the bottom of the furnace, the inside of the electrode with the end of the wall, removable side wall, furnace heart (called: electric furnace center of the heating element, With graphite powder or petroleum coke according to a certain shape and size installed in the charge center, usually round or rectangular. Its ends connected with the electrode) and other components. The furnace used in the firing method commonly known as: buried powder burning. (The SiC is mainly formed at ≥1800 ℃), and the co-heating is started, and the furnace temperature is about 2500 ℃, or even higher (2600 ~ 2700 ℃), the charge reaches 1450 ℃. However, ≥ 2600 ℃ when the decomposition of SiC, but the decomposition of the Si and the charge will be generated in the SiC. Each group of electric furnaces is equipped with a set of transformers, but the production is only a single electric furnace power supply, in order to adjust the voltage according to the load characteristics to maintain a constant constant power, high-power electric furnace to heat about 24 h, after the power to generate the basic reaction of SiC After a period of cooling can remove the side wall, and then gradually remove the charge.

After the high temperature calcination of the charge from the outside to the inside are: unreacted material (in the furnace from the role of insulation), oxygen silicon carbide (semi-reactive material, the main component is C and SiO.), Adhesive layer Very important material layer, the main component is C, SiO2, 40% ~ 60% SiC and Fe, Al, Ca, Mg carbonate), amorphous layer (the main component is 70% to 90% SiC, and Cubic SiC is β-sic, the rest is C, SiO2 and Fe, A1, Ca, Mg carbonate), secondary SiC layer (the main component is 90% to 95% SiC, the layer has been generated hexagonal SiC A SiC layer (SiC content <96%, and hexagonal SiC that is a large crystal of SiC), furnace core graphite. In the above-mentioned layers, the unreacted material and a part of the silicon carbide layer are usually collected as inexpensions, and the other part of the silicon carbide layer is collected together with the amorphous material, the secondary product and the partial binder Charge, and some sticky very tight, large block, impurities and more sticky material is abandoned. While the first grade products are graded, crushed, crushed, chemically treated, dried and sieved, after magnetic separation to become a variety of particle size of the black or green SiC particles. To be made of silicon carbide powder also through the water selection process; to make silicon carbide products have to go through the process of forming and burning.


Hangzhou JWG Technology Co.Ltd