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Sintering Process of Silicon Carbide Ceramics
The main component of silicon carbide ceramic material is SiC. Has excellent mechanical properties, excellent oxidation resistance, extremely high wear resistance and low coefficient of friction. The biggest advantage of silicon carbide ceramics is that it can maintain high strength and hardness at a high temperature of 1400 degrees Celsius. In addition, the thermal conductivity of pressureless silicon carbide ceramics is also very high, second only to beryllium oxide and aluminum nitride ceramics, so it is suitable for various harsh environments.
Because silicon carbide ceramics have many excellent properties, they have been widely used in aerospace, machinery industry, electronics and other fields in recent years, and the market prospect is broad. Let’s briefly introduce them below.
Sintering of Silicon Carbide Ceramics
Silicon carbide ceramics are manufactured by sintering. According to the sintering process, silicon carbide ceramics can be divided into recrystallized silicon carbide ceramics, reaction sintered silicon carbide ceramics, pressureless sintered silicon carbide ceramics, hot-pressed sintered silicon carbide ceramics, high temperature hot isostatic pressing sintered silicon carbide ceramics and chemical vapor phase Silicon carbide is deposited. The properties of silicon carbide prepared by different processes are quite different.
Among these sintering methods, pressureless sintered silicon carbide is the most widely used and most promising silicon carbide sintering technology. This sintering method not only can obtain dense, high-quality ceramic parts, but also is suitable for parts with various complex shapes. Here’s how to use them:
Due to its superhard properties, it can be prepared into various grinding wheels, abrasive cloths, sandpapers and various abrasives, which are widely used in the machining industry. Industrial silicon carbide is mostly used as abrasive, and abrasive tools made of black silicon carbide are mostly used for cutting and grinding materials with low tensile strength, such as glass, ceramics, stones and refractories, as well as cast iron parts and non-ferrous metal materials. grinding. Grinding tools made of green silicon carbide are mostly used for grinding hard alloys, titanium alloys and optical glass, as well as honing of cylinder liners and fine grinding of high-speed steel tools. Cubic silicon carbide is specially used for super-fine grinding of miniature bearings. The oil stone made of cubic silicon carbide powder is used for super-fine grinding of bearings, and its smoothness can be directly ground from V9 to V12 or above.
(Silicon carbide grinding powder)
Silicon carbide is used in greater quantities as a refractory material than as an abrasive. Refractory black silicon carbide is usually divided into three grades: ① high-grade refractory black silicon carbide. The chemical composition of this grade is exactly the same as that of black silicon carbide for abrasives. It is mainly used to manufacture advanced silicon carbide products, such as gas turbine components, nozzles, silicon nitride-bonded silicon carbide parts, blast furnace high temperature zone lining materials, and high temperature kiln components , High temperature kiln kiln support, refractory sagger, etc. ②The secondary refractory black silicon carbide contains more than 90% silicon carbide. It is mainly used to manufacture medium and high temperature resistant kiln components, such as muffle furnace lining materials. In addition to using the heat resistance and thermal conductivity of silicon carbide, these components also use its chemical stability in many occasions. ③ Black silicon carbide, a low-grade refractory material, whose silicon carbide content is required to be greater than 83%, is mainly used for the lining of tapping grooves, ladle, zinc smelting and sponge iron manufacturing.
(Silicon carbide refractory bricks)
In steelmaking, ferrosilicon is usually used for deoxidation, and silicon carbide is used instead of ferrosilicon as a deoxidizer. The quality of the steel produced is better and more economical. Because silicon carbide is used for deoxidation, the slag is less and faster, which effectively reduces the content of some useful elements in the slag, and the steelmaking time is short and the composition is better controlled.
Deoxidizer black silicon carbide is widely used in the steel industry in countries such as the United States and Japan. The materials suitable for deoxidizers produced by silicon carbide for abrasives or refractory materials in the furnace can all be sold and used in production without returning to the furnace. The comprehensive utilization rate of products is high, and the economic effect of silicon carbide production is excellent.
4.Wear-resistant and high-temperature parts
Using the high hardness, wear resistance, acid and alkali corrosion resistance of silicon carbide ceramics, it is used in the machinery industry and chemical industry to prepare a new generation of mechanical sealing materials, sliding bearings, corrosion-resistant pipes, valve plates and fan blades. Especially as a mechanical sealing material, it has been recognized internationally as the fourth-generation basic material since metal, alumina, and cemented carbide. Its acid and alkali resistance is extremely excellent compared with other materials, and there is almost no one. Materials are comparable.
Using the high thermal conductivity of silicon carbide ceramics, it is used in high-temperature heat exchangers in metallurgical industry furnaces, etc., and the operating temperature can reach 1300 ° C; grinding rice with silicon carbide sand can improve the quality of rice compared with other grinding rollers, and the quality of rice can be improved. The rice rate is increased by 1% to 2%, and the cost is reduced by 30% to 40%.
Coating silicon carbide micropowder on the turbine impeller by electroplating method can greatly improve the wear resistance of the impeller and prolong its maintenance period. Pressing the cubic silicon carbide powder and W28 fine powder into the cylinder wall of the internal combustion engine with mechanical pressure can prolong the service life of the cylinder block by more than 1 times.
(Silicon carbide impeller, silicon carbide nozzle)
Using a mixture of silicon carbide and borax to perform surface boronizing chemical heat treatment on the 45°steel harvester blade, the hardness of the boronized layer can reach the Kjeldahl microhardness of 1800-2000kg/mm², thereby prolonging its service life several times.
The idler made of silicon carbide has already been successfully used in rolling mills. It has better heat resistance and wear resistance than metal idlers, and can improve the quality of the rolled steel.
Sand pumps and hydrocyclones made of silicon carbide materials have good wear resistance; wear parts such as cylinder liners made of silicon carbide materials can be widely used in petroleum and chemical industry machinery and can also be used as high temperature Materials for thermomechanical use. Because of its good high temperature properties, such as high temperature oxidation resistance, high high temperature strength, low creep, good thermal conductivity and low density, silicon carbide is the first choice for high temperature resistant components of thermomechanics, such as the combustion chamber of high temperature gas turbine, Turbine stationary blades, high temperature nozzles, etc. Pistons and cylinder liners made of silicon carbide are used in diesel engines without lubricating oil and cooling, which can reduce friction by 30% to 50% and reduce noise significantly.
Combustion chambers and nozzles composed of silicon carbide ceramics and other materials have been used in rocket technology. Silicon carbide has a medium density, high hardness and elastic modulus, and low price. It can be used in armored vehicles and aircraft belly and bulletproof and stab-proof clothing.
Silicon carbide material also has self-lubricating properties and a small friction coefficient, which is about half of that of cemented carbide. Its characteristics of good thermal shock resistance and high elastic modulus are used in some special places. For example, it is used to make high-power laser mirrors. Its performance is better than that of copper. Due to its low density, good rigidity and small deformation, CVD and Reaction sintered silicon carbide lightweight mirrors have been used extensively in space technology.
(Silicon carbide ceramic body armor)
6.Electrical and Electricians
Using the high thermal conductivity and good insulation of silicon carbide ceramics, it is used as a substrate and packaging material for large-scale integrated circuits. Silicon carbide heating element is a commonly used heating element. Because of its advantages of simple and convenient operation, long service life and wide range of use, it has become the most durable and inexpensive heating material. The operating temperature can reach 1600 ℃ . Silicon carbide can also be used as the valve body of the arrester and the far infrared generator.
(Silicon carbide reflection mirror)
Selection of silicon carbide sintering equipment: pressureless sintered silicon carbide is widely used. In order to obtain high-quality silicon carbide ceramics, high-quality sintering equipment must be used for preparation. The RVS vacuum sintering furnace provided by SIMUWU is an excellent product for processing silicon carbide sintering. It has the characteristics of good temperature uniformity and high temperature control accuracy. SIMUWU provides a professional team of engineers who can solve various problems encountered in the production process and are committed to giving customers the most convenient and efficient experience.
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