Silicon Carbide Ceramic

Description

1. Silicon Carbide Ceramic Description

Silicon carbide ceramic not only have excellent mechanical properties at room temperature, such as high flexural strength, excellent oxidation resistance, good corrosion resistance, high wear resistance and low friction coefficient. And high temperature mechanical properties, such as strength, creep resistance, etc., are also the best known ceramic materials.
 
The initial application of SiC is that due to its superhard properties, it can be prepared into various grinding wheels, abrasive cloths, sandpapers and various abrasives, so it is widely used in the machining industry. In World War II, it was found that it can also be used as a reducing agent and heating element in steelmaking, thus promoting the rapid development of SiC. Silicon carbide ceramic have been widely used in petroleum, chemical, microelectronics, automobile, aerospace, aviation, papermaking, laser, mining and atomic energy and other industrial fields.
 
At present, silicon carbide has been widely used in high-temperature bearings, bulletproof plates, nozzles, high-temperature corrosion-resistant parts, and electronic equipment parts in the high-temperature and high-frequency range.
 
2. Wide Application of Silicon Carbide Ceramic
 
Silicon carbide ceramic have four main application areas. Namely, functional ceramics, advanced refractories, abrasives and metallurgical raw materials.
 
(1) As an abrasive, it can be used as an abrasive tool. Such as grinding wheels, whetstones, grinding heads, sand tiles, etc.
(2) as metallurgical deoxidizer and high temperature resistant material.
(3) High-purity single crystals can be used to manufacture semiconductors and silicon carbide fibers.
 
Specifically, silicon carbide ceramics are used in chemical, refractory, metallurgy, steel, ceramics and other fields.
 
In the chemical industry. Silicon carbide can be used as a deoxidizer for steelmaking and a modifier for cast iron structure. It can also be used as a raw material for the manufacture of silicon tetrachloride and is the main raw material for the silicone resin industry. Silicon carbide deoxidizer is a new type of strong composite deoxidizer, which replaces the traditional silicon powder carbon powder for deoxidation. Compared with the original process, the physical and chemical properties are more stable and the deoxidation effect is good. The deoxidation time is shortened, energy is saved, steelmaking efficiency is improved, and steel quality is improved. Reduce the consumption of raw and auxiliary materials, reduce environmental pollution, improve working conditions, and improve the comprehensive economic benefits of the electric furnace.
 
In the refractory industry, the use of silicon carbide has the characteristics of corrosion resistance, high temperature resistance, high strength, good thermal conductivity, and impact resistance. On the one hand, silicon carbide can be used in various smelting furnace linings, high-temperature furnace components, silicon carbide plates, silicon carbide lining plates, supports, saggars, silicon carbide crucible, silicon carbide tiles, etc. In the iron and steel industry, the use of silicon carbide's characteristics of corrosion resistance, thermal shock resistance, wear resistance, and good thermal conductivity is used for the lining of large blast furnaces to improve the service life.
 
On the other hand, it can be used for high-temperature indirect heating materials in the non-ferrous metal smelting industry. Such as vertical tank distillation furnace, rectification furnace tray, aluminum electrolytic cell, copper melting furnace lining, arc plate for zinc powder furnace, thermocouple protection tube, etc. It is used to make high-grade silicon carbide ceramic materials such as wear resistance, corrosion resistance and high temperature resistance. It can also be used to make rocket nozzles, gas turbine blades, etc.
 
Metallurgical beneficiation. The hardness of silicon carbide is second only to diamond, and it has strong wear resistance. It is an ideal material for wear-resistant pipes, impellers, pump chambers, cyclones, and hopper linings. Its wear resistance is 5-20 times of the service life of cast iron and rubber.
 
In the ceramic industry, thin-plate kiln furniture is manufactured by utilizing its characteristics of thermal conductivity, thermal radiation, and high thermal strength. Not only can the capacity of kiln furniture be reduced, but also the capacity and product quality of the kiln can be improved. It shortens the production cycle and is an ideal indirect material for ceramic glaze baking and sintering.
 
In addition, silicon carbide is also one of the ideal materials for solar water heaters for highways and aviation runways.
 
3. Sintering Process for Preparing Silicon Carbide Ceramic
 
At present, the methods for preparing high-density SiC ceramics mainly include pressureless sintering, hot pressing sintering, hot isostatic pressing sintering and reaction sintering.

• Through the pressureless sintering process, SiC parts with complex shapes and large dimensions can be fabricated. Therefore, it is considered to be the most promising sintering method for the preparation of SiC ceramics.
• With the hot-pressing sintering process, only simple-shaped SiC parts can be produced, and the number of products produced in one hot-sintering process is small. Therefore, it is not conducive to commercial production.
• Although the hot isostatic pressing process can obtain complex shaped SiC products, the green body must be encapsulated. Therefore, it is difficult to achieve industrial production.
• SiC parts with complex shapes can be prepared by the reaction sintering process, and the sintering temperature is relatively low. However, the high temperature performance of reaction sintered SiC ceramics is poor.

Table 1 presents some properties of SiC ceramics in pressureless sintering, hot pressing sintering, hot isostatic pressing sintering and reaction sintering.
    
Obviously, the properties of SiC ceramics vary depending on the sintering method. Generally speaking, the comprehensive properties of pressureless sintered silicon carbide are better than those of reaction sintered SiC, but inferior to those of hot pressing sintered and hot isostatic pressing sintered silicon carbide.
 
4. Types and Specific Applications of Reactive Sintered Silicon Carbide Ceramic Products
 
Commonly used silicon carbide ceramic generally refer to reaction sintered silicon carbide products. Reaction sintered silicon carbide ceramics, also known as self-bonding silicon carbide ceramics. The blank is made into a green body by pressing, extrusion, grouting or other forming methods. It can be used as a coating material for nuclear fuel, sealing parts of various types of machinery, and high-temperature gas turbine components (mainly combustion chambers) with ideal effects. This type of silicon carbide ceramic products mainly include silicon carbide tanks, silicon carbide cans, silicon carbide containers, silicon carbide saggers, silicon carbide boxes, silicon carbide tubes, special-shaped silicon carbide parts, etc.
 
4.1 Silicon carbide ceramic tank - mainly used in the production of sponge iron
 
The tunnel kiln process produces sponge iron. The reduction tank is placed on the tank car, and the concentrate powder, coal powder and limestone powder are respectively loaded into the silicon carbide reduction tank according to a certain proportion and charging method, and then pushed into the tunnel kiln. After the silicon carbide ceramic tank is preheated, heated, roasted and cooled, the concentrate powder is reduced to obtain sponge iron. The process is mature and reliable, with less investment, quick effect, low cost, and high and stable product quality. With the advantages of simple operation, stable equipment operation and low energy consumption, it is the most used sponge iron production process in China.
 


4.1.1 Working Environment of Silicon Carbide Ceramic Reduction Tank
 
Tunnel kiln sintering reduced iron powder is to use a row of reduction tanks on the kiln car, and put the items to be fired into the silicon carbide reduction tanks for sintering. Therefore, in the sintering process, the reduction tank has to withstand high temperature and air scouring and changes in cooling and heating cycles. The harsh environment has high requirements on the performance and quality of the reduction tank, and the silicon carbide reduction tank has also become a vulnerable part. Therefore, the reduction tank is required to have high high temperature strength, erosion resistance and good thermal shock resistance.
 
4.1.2 Performance of Silicon Carbide Ceramic Reduction Tank
 
Silicon carbide ceramic reduction tank is sintered at high temperature with silicon carbide as aggregate and binder added. In addition to maintaining the good characteristics of silicon carbide, it has good oxidation resistance because a dense oxide protective film can be formed after the surface is oxidized to prevent further oxidation.
 
In the sintering of the tunnel kiln, the life of the silicon carbide refractory reduction tank used to hold the iron powder is an important condition for the long life of the kiln. The life of the refractory reduction tank determines the efficiency and benefit of production. Silicon carbide ceramic refractory reduction tank has good properties such as high temperature strength, high thermal conductivity, good thermal shock resistance and alkali corrosion resistance, and low thermal expansion rate. It is stable to most chemical substances and is not corroded by molten non-ferrous metals, and has achieved excellent effects in the application of direct reduction iron kilns.
 
 
 
4.1.3 Production process of silicon carbide ceramic reduction tank
 
The manufacture of silicon carbide ceramic reduction tank adopts the force method of reaction sintering. Using SiC as aggregate, adding compound additives. Select a reasonable particle gradation mixing system and forming process. After the green body is dried, it is fired at a temperature of 1350 ~ 1450 ℃ in an oxidizing atmosphere in a special kiln. The SiC particles are tightly bound together by the ceramic phase sintered with the aid of the additive and the silica film formed by the oxidation of the contact surface of the silicon carbide particles. Thereby a dense ceramic block is formed and high strength is obtained. In order to improve the performance of the product, the purity of the selected SiC raw material should be above 97%.

In recent years, we have developed a new type of silicon carbide ceramic reduction tank in response to the development requirements of the powder metallurgy industry and customer feedback. More than a dozen program groups have been tested successively. After comparison and trial, the process plan of adding composite ceramic additive was finally determined. At the same time, the production line has been transformed to form a standardized reduction tank production line, and the product performance has been greatly improved. In addition to supplying the domestic market, the products are also exported to Japan, Europe and other countries and regions.
 
4.2 Silicon Carbide Ceramic Saggers, Shed Plates, Trap Plates - Ceramic Kiln Furniture
 
With the rapid development of the national economy, SiC kiln furniture has become an important auxiliary material in industries such as electric ceramics and grinding wheels in China, and the demand is also increasing. The quality of kiln furniture directly affects the cost and quality of the ceramic products produced. The production of ceramic products tends to be of high quality, high yield and low consumption, and the firing process tends to be fast. Therefore, the requirements for kiln furniture are also more stringent. First of all, it is expected that kiln furniture materials can withstand high temperatures, even have high strength at very high temperatures, and be durable under high temperature and rapid firing conditions. Secondly, it is less heat storage, fast heat transfer, smooth and flat kiln furniture, and accurate size.


 
SiC material has excellent high temperature mechanical properties, fire resistance, thermal shock resistance, high thermal conductivity and low expansion. Using it as kiln furniture material can greatly reduce energy consumption and improve the production capacity of the kiln. Therefore, it is widely used in the hot work of kilns.
 
3.2.1 Classification of silicon carbide kiln furniture
 
The quality of SiC kiln furniture depends to a large extent on the condition of the binder. Therefore, SiC kiln furniture is classified by different binders and can be generally divided into four categories.
(1) Clay binds SiC;
(2) Silicon oxide combined with SiC;
(3) SiN4 combines with SiC;
(4) Recrystallized SiC.
 
3.2.2 The performance of SiC kiln furniture
 
High temperature resistance and high strength, good thermal stability, good wear resistance and corrosion resistance, and high thermal conductivity. The outstanding weakness of SiC kiln furniture materials is poor oxidation resistance, mainly because SiC oxidizes to generate SiO2, which causes volume expansion and deformation at high temperature. Therefore, different binders will limit the effect of oxidation.
 
The clay-bonded SiC kiln furniture generates a small amount of liquid phase at high temperature, and the mechanical strength of the material decreases with the increase of temperature, so the service life and operating temperature of the clay-bonded SiC kiln furniture are limited. Although the high temperature strength of SiO2 bond is slightly better than that of clay bond, it is far less than Si3N4 bonded SiC and recrystallized SiC. Si3N4 combined with SiC kiln furniture is called a replacement product, mainly because of the good high temperature performance of this material. Recrystallized SiC makes the best use of the characteristics of SiC itself, and the strength of this product is 7 to 10 times that of general SiC products. The common feature of it and Si3N4 combined with SiC kiln furniture is that the mechanical strength of the kiln furniture not only does not decrease at high temperature, but increases slightly. This excellent performance, coupled with good thermal shock resistance and oxidation resistance, can double the service life of kiln furniture compared with traditional kiln furniture.
 
3.2.3 Application of silicon carbide kiln furniture
 
SiC kiln furniture has a wide range of uses, especially for shed plates, trap plates and saggars for various kilns. At present, most of the kiln furniture used in ceramics, grinding wheels and other industries are made of clay or high alumina. These materials themselves have low high temperature strength, poor thermal shock resistance, and are easily deformed and ruptured under high temperature loads. Due to the thickness of these products, the production capacity of the kiln is reduced and the load of the kiln furniture itself is increased, which reduces the service life of the kiln furniture. Sometimes, the consumption of kiln furniture accounts for more than 30% of the production cost and affects the quality of the product. SiC kiln furniture, especially Si3N4 combined SiC and recrystallized SiC kiln furniture, has high bending strength, good thermal shock resistance, oxidation resistance, excellent wear resistance, corrosion resistance and high temperature creep resistance. As a new generation of kiln furniture, it has been recognized and accepted by more and more industries.
 
The use of SiC kiln furniture can greatly reduce the loading ratio of kiln furniture and products. Effectively use the volume of the kiln to strengthen the firing process of the product and achieve rapid firing. The application of SiC kiln furniture, especially Si3N4 combined with SiC and recrystallized SiC kiln furniture, is increasingly favored by the kiln industry due to its excellent performance. So as to promote the greater development of the refractory industry.
 
 
4.3 Silicon Carbide Ceramic Tube - Power Plant Coal Injection Tube
 
Silicon carbide tubes are mainly used in medium frequency forging, various heat treatment electric furnaces, metallurgy, chemical industry, non-ferrous metal smelting and other industries. Widely used in metallurgical sintering furnace and intermediate frequency heating forging furnace. Length can be designed. Silicon carbide tube has the advantages of high strength, high hardness, good wear resistance, high temperature resistance, corrosion resistance, good thermal shock resistance, high thermal conductivity and good oxidation resistance.
 


The silicon carbide wear-resistant tubes and coal injection tubes of power plants independently developed by the company have excellent characteristics such as high temperature resistance, wear resistance, impact resistance, good stability in rapid cooling and rapid heating, high bending resistance, and strong acid and alkali corrosion resistance. All of its performances have been tested and recognized by national authoritative testing institutions. Silicon carbide ceramic tubes have the following properties.
 
1. Dimensional stability at high temperatures, resistance to deformation and high strength at high temperatures
2. Resistance to thermal shock, abrasion and corrosion
3. Anti-oxidation and erosion resistance

It can be widely used in: electric power, steel plant slag flushing trench, coal chemical industry, mining, transportation pipeline.
  4.4 Silicon Carbide Ceramic Desulfurization Burners, Special-Shaped Parts, etc.
 
 
4.5 Silicon Nitride Bonded Silicon Carbide Products

 
5. To Buy Silicon Carbide Ceramic Products, Please Contact Us
 
The company's silicon carbide ceramic products include silicon carbide tubes (coal injection tubes for power plants), silicon carbide saggers, silicon carbide shed plates, silicon carbide bricks, wear-resistant and corrosion-resistant impellers, wear-resistant seals, etc. Widely used in electric power, electric porcelain, direct reduced iron, vanadium and titanium, mineral processing, metallurgical industries, etc. The products are sold well in China and exported to Germany, the United States, South Korea, Japan, Turkey, Thailand, Indonesia, Vietnam, India, Spain, Australia, the Middle East and other countries and regions. To buy silicon carbide ceramic, silicon carbide crucible, silicon carbide tube, sintered silicon carbide, silicon carbide refractory, please contact us.