The main difference between silicon nitride bonded silicon carbide bricks and silicon carbide bricks lies in products characteristic, preparation process and application performance.
Silicon nitride bonded silicon carbide brick is made from SiC and Si as raw materials through a nitriding and sintering process. The characteristic of this brick is using Si3N4 as a binder. During the production process, it is necessary to control the addition of temporary binding agents, which helps to fuse the raw materials more evenly. At the same time, during the drying and firing processes, the binding agents can also improve the reaction efficiency between silicon powder and nitrogen. It is characterized by using Si3N4 as the binding phase. Si3N4 exists between SiC grains in the form of needle-like or fibrous crystals and it is an important new refractory material.
Silicon carbide bricks are mainly made from silicon carbide as the main raw material. The different bonding methods can be divided into clay bonded silicon carbide bricks, silicon oxynitride bonded silicon carbide bricks, etc. The preparation of silicon carbide bricks does not involve the commonly known sintering process, but relies on chemical reactions to generate new phases to achieve sintering. In addition, carbon bricks are high-temperature resistant neutral refractory products made of carbonaceous materials as the main component and an appropriate amount of binder.
Silicon nitride bonded silicon carbide bricks have a series of excellent properties, such as good organizational structure, good alkali corrosion resistance, molten cryolite wettability resistance, oxidation resistance, chemical corrosion resistance, as well as high density, high strength, good Thermal shock stability, high thermal conductivity and high resistance value, etc.
Silicon carbide bricks have the characteristics of good wear resistance, corrosion resistance, high high temperature strength, good thermal shock stability, high thermal conductivity, small thermal expansion coefficient, etc., and are high-performance refractory materials.
The characteristic of the silicon nitride bonded silicon carbide brick process is the using the reaction sintering principle. The nitrided refractory bricks use SiC and Si powder as raw materials, and the SiC body containing silicon powder is sintered through the nitridation reaction. The sintering process is completed in a closed furnace that is filled with nitrogen and is easy to control. The temperature pressure and atmosphere in the furnace must be strictly controlled in order to produce products with good microstructure and performance. Main process parameters: nitriding gas pressure 0.02-0.04MPa, furnace atmosphere containing 02 less than 0.01%, final nitriding temperature 1350-1450°C, total nitriding time varies with the shape and size of the product.
Silicon carbide bricks are made of silicon carbide as the main raw material. Silicon carbide content is 72% to 99%. Generally, black silicon carbide (SiC content is more than 96%) is used as raw material, a binder is added (or no binder is added), and it is made through batching, mixing, molding and firing. The main crystal phase is silicon carbide. SiC is covalently bonded and does not have the so-called sinterability. Instead, it relies on chemical reactions to generate new phases to achieve sintering, that is, reaction sintering.
Silicon nitride bonded silicon carbide bricks are mainly used in building sanitary ceramics, daily porcelain, electric porcelain, aluminum, copper, zinc, steelmaking and steel rolling, ironmaking, metal heat treatment, environmental protection and other fields. It is also used as the lining of the lower furnace body of the blast furnace, which can more than double the service life of traditional refractory materials. In addition, it can be used as the lining of aluminum reduction electrolytic cells, which has the advantages of energy saving, extended life, and no pollution to the environment. It can also be used as a blast furnace air cooling pipe sleeve. However, because the price of silicon nitride combined with silicon carbide bricks is relatively high, this makes It has been limited in a wide range of applications.
Silicon carbide bricks are widely used in industry. It’s can be used in metallurgical steel drum linings, nozzles, plugs, blast furnace bottoms and bosses, water-cooled slide rails in heating furnaces; non-ferrous metal smelting stills, distillation tower trays, side walls of electrolyzers, smelting metal crucibles; silicic acid Shelf boards and flameproof materials for salt industry kilns; oil and gas generators and organic waste combustion furnaces in the chemical industry; kiln furniture for high-tech ceramics, aluminum electrolytic cell linings, molten aluminum conduits, and kiln furniture for ceramic kilns, large and medium-sized blast furnaces Lower body, furnace waist and belly, aluminum refining furnace lining, zinc distillation tank lining, etc.
In the diverse landscape of refractory materials, the choice between silicon nitride bonded silicon carbide bricks and silicon carbide bricks hinges on a careful evaluation of the intended application’s demands. Each product presents distinct advantages, , So understanding their differences is pivotal in making an informed decision to ensure optimal performance and longevity in industrial settings.
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