Applications of silicon carbide

As everyone knows, silicon carbide has a very broad application field, in the field of abrasive, chemical, metallurgy, high-grade refractory materials, advanced ceramics have a very versatile. Silicon carbide is a special material machinery industry chain upstream link – wafer productionprocess, mechanical industry development, silicon carbide industry has brought some opportunities by expanding and upgrading of product structure and the downstream demand.

Refractory materials and machinery are silicon carbide traditional low-end applications, low added value. With the continuous innovation of the processing equipment and technology, aiming at strengthening the development of the new use of silicon carbide and new application market, expand the business ideas, is the only way for the healthy development of the silicon industry in the future.

Silicon carbide are used widely, such as metallurgy, machinery, chemical industry, mining machinery, light industry, electronics, a heating body, abrasive can be used as a metallurgicalindustrial purifying agent, deoxidizing agent and modifier. In the mechanical processing can be used as synthetic cemented carbide; silicon carbon plate after processed can be used for roof plate as refractory ceramic firing. By finishing the production of powder, can be used in the high-tech electronic components and far infrared radiation material coating, high purity micro powder can be coated for national defense industry stone machine industry Aerospace ware, use in every field of economy of domestic and international is very wide.

Production and processing of silicon carbide is dependent on the crusher and mill equipment, and because of its special requirements, so it is necessary to select appropriate crusher products can meet the requirements of. The broken plastic, red star heavy sand making machine is suitable for soft or hard and super hard materials, widely used in all kinds of ores, cement, refractories, aluminum where soil clinker, glass raw materials, mechanism building sand, stone and various metallurgical slag, especially for silicon carbide, Jin Gang sand, sintered bauxite, beautiful sand high hard, and very hard abrasive resistant material than other types of crusher yield higher efficiencies.

New type refractory -magnesia calcium brick

Magnesia calcium brick also called high calcium magnesium brick. In order to periclase as main crystal phase, silicate calcium for three secondary crystalline phase of magnesiarefractories. Containing MgO80% ~ 87%, CaO6% ~ 9%, CaO/SiO2 than in 2.2 ~ 3. The show structural characteristics of periclase and two calcium silicate calcium silicate and three direct contact, eutectic (interstitial 4CaO – Al2O3 – Fe2O3 into veinlets filled in the silicate calcium silicate calcium two and three between. Low porosity. Refractoriness under load was generally higher than 1700 DEG C, good performance of anti alkaline residue. But poor thermal shock resistance. Taking calcium magnesite as raw material, and through crushing, proportioning, mixing, molding, firing at 1550 to 1600 degrees. Can be used for side blown converter steelmaking at eye, open hearth and oxygen converter etc…

Magnesia calcium brick is basic refractory products with MgO and CaO as the main chemical components, including dolomite brick and magnesia dolomite brick. Magnesia calcium brick with excellent performance, especially with purifying molten steel performance is other kind of refractory materials do not possess. Therefore, magnesia calcium brick has been widely used in AOD furnace, VOD furnace and LF furnace refining equipment, and have achieved good results.

Magnesia calcium brick with seven properties, respectively, high temperature resistance, slag corrosion resistance, anti stripping performance, wear resistance, purifying molten properties, hydration resistance.

Along with our country stainless steel and all kinds of clean steel production capacity continues to expand, all kinds of refractories consumption will continue to increase. For better production and use of magnesia calcium brick, for China’s steel industry and other high temperature industrial services, to analyze and discuss the use performance of magnesia calcium brick, with understanding and knowledge of magnesia calcium brick using performance and influence factors is very necessary.

Furnace refractories and kiln car refractory

Furnace refractories  including and kiln wall top, generally divided into three layers, the inner layer is a light cotton insulation, felt, plate, the middle layer is heavy or light insulating brick, outer with red brick or low temperature heat preservation brick based. The inner layer of the light insulating layer is a rapid development in recent years, with the temperature of mullite fiber, both high temperature mullite fiber, high alumina mullite fiber, containing zirconium mullite fiber from each system, temperature 1200 C ~1600 C. In the fiber is used in the process of wire drawing, silk, blowing process. The inner layer is also useful for lightweight mullite, high aluminum light brick or board, with lightweight alumina, mullite hollow spherical brick as the main body. Heavy material middle still use the heavy material with low aluminum high silicon, high aluminum low silica, mullite and cordierite, mullite materials such as coke gemstones and made mostly from. Low temperature refractory material outer layer mainly bauxite, coke gemstones, clay and other production, relatively lowtemperature resistance performance of the aluminum content, poor but low price.

Kiln car refractory kiln car surface, the kiln car frame, load bearing board, saggar, except the basic architecture of the kiln car surface material, the rest of the material referred to as kiln furniture materials. Kiln car refractories and furnace wall materials are basically the same. Kiln material according to different situations with mullite, high alumina mullite, cordierite, mullite – cordierite, SiC, oxide combined silicon carbide, silicon nitride bonded silicon carbide etc… In addition to the above materials, modern ceramic kiln cannot be ignored is the roller kiln ceramics sticks, now have aluminum oxide ceramic stick, silicon nitride, silicon carbide, silicon infiltration of recrystallized silicon carbide, silicon nitride bonded silicon carbide etc.. The kiln roller building sanitary ceramics sticks to high alumina based.

Access threshold for the refractories industry

The Ministry website news, in order to strengthen the management of  refractory  material industry, and guide rational investment, accelerate structural adjustment, change in mode of development, promote the healthy and sustainable development of refractory materials industry, the ministry organized the preparation of the “refractory material industry access conditions” (Draft), is to solicit opinions from the public.

It is reported, the draft from the production layout, technology and equipment, quality management, clean production, energy saving and comprehensive utilization, production safety and social responsibility, supervision and management and other aspects, in refractory material industry of the access specification. Draft pointed out, strict control of new capacity, in principle, to rely on the existing refractory materials production enterprises, through a joint reorganization, the implementation of equal or reduction replacement, carry out technological transformation, promote energy-saving emission reduction, the promotion of the production and use of unshaped refractory materials, the optimization of the industrial structure, improve the production concentration.

Datong securities investment consultant Zhang Cheng think, refractories industry set admittance threshold, will reduce duplication of investment, avoid small enterprises rushing headlong into mass action, helps to promote the orderly development of refractory industry. “Strict control of new capacity, through a joint reorganization, the implementation of equal or reduction replacement” expression, fully explain the industry supply will be controlled, the industry is expected to set off the upsurge of M & an integration. Therefore, refractory materials leading enterprises is expected to benefit from it.

Analysis of thermal radiation ability of refractory brick

At the same temperature, the ratio of heat energy and blackbody radiation surface of refractory brick of the radiation. Also cal. Also called the blackness, rate of thermal radiation, the radiation rate, radiation coefficient, and relative radiation rate. It is characterized of refractory brick surface of the heat radiation ability. High temperature kiln furnace wall brick surface emissivity directly affects the efficiency of heat transfer in the furnace material. Use from the emissivity of paint spraying furnace wall heating furnace to improve the thermal efficiency is one of the important ways, saving fuel consumption, the influence of the surface emissivity of refractory brick composition and surface state. Silicon carbide, zirconium containing refractory brick has a relatively high emission rates, often used in the manufacturing of high emissivity coating. Refractory brick firing rate decreased with the increase of temperature in general. The surface state it largely depends on the refractory materials. The surface roughness increases when the emissivity. Refractory brick at room temperature, surface emissivity typically between (0.85 ~ 0.99)

Brick under normal temperature and surface emissivity are typically between (0.85 ~ 0.99)

Refractory brick emission test method a lot of, common card meter method, it is the vacuum cavity to be measured refractory brick sample in the constant temperature and the inner wall around the black. For refractory brick samples after heating specimen measured under steady state conditions the thermal equilibrium temperature and input power, or cooling curve for determination of refractory brick samples (non steady state method), Hen according to the law of conservation of energy to write the heat balance equation, to calculate the emission rate of refractory brick.

To understand the information in refractory products, please pay attention to Xinmi Changxing refractory http://www.yilongrefractory.com

Improvement and using of furnace refractory material

Open hearth furnace masonry damage mainly caused by slag and liquid steel chemical erosion and high temperature corrosion and spalling. Open hearth is most easily damaged, is the weak link in the whole lining, directly related to the small yield of furnace. Therefore, all the countries take the thin furnace top as an important technical index of open hearth furnace; open hearth furnace life refers to the so-called top life. Enter sixty ages, the world each for open hearth furnace adopting ordinary alkaline brick masonry. China is widely used magnesia brick, the medium-sized open hearth furnace service life reached about 1000 times.

With the development of open hearth oxygen blowing intensified smelting, the production efficiency is improved, but the decline in life. To this end. We must improve the brick quality, development of new varieties, to meet the need of strict furnace smelting process. In this case, the British in the 1959 car developed directly combines the basic brick manufacturing, the key is using high purity raw materials, high pressure shaping and high temperature firing. In order to combine the firebrick and magnesia brick firing temperature and high temperature relation of bending strength. With increasing the burning amyl temperature, direct burning of magnesia chrome brick flexural strength increases, and magnesia brick to 1800 C strength decreases. As is said, in order to obtain the excellent combination of magnesium lead bricks, the sintering temperature should be greater than 1700 DEG C, the best sign about 1800 DEG C firing.

The creep of refractory material

Refractory material especially in the high temperature when subjected to below its ultimate strength under a certain stress will produce plastic deformation, deformation along with the load increasing, and even lead to the failure of materials. This external force generated by the deformation increased with time phenomenon called creep. Creep refractories are its stress compression under certain temperature and pressure effect after certain time generated to represent the creep. Sometimes often to achieve individual variables of time, can also be directly to the deformation or strain rate versus time curve description. The compressive stress strain measuring results is not easy to be keen reflected inside the material phase change, so often in the bending creep or creep (torsional shear creep) said.

Creep refractory material is a function of stress, temperature, time and material structure. Material at higher temperature, stress is bigger, the longer, the greater the creep rate. When the refractory material completely by the crystal structure, creep in addition to bond strength by the relevant and crystal elastic effects of crystal, crystal body is mainly controlled by vacancy diffusion, dislocation movement, the control with the state grain boundary sliding and grain. Crystal defects, grain boundaries are less and less grain combine is strong, not easy to produce serious creep.

When the material containing glass phase, especially when the glass phase as continuous phase, material creep by glass phase control. The higher the amount and viscosity of the glass phase is low, material under low stress can produce viscous flow, so in the high temperature creep is more serious. When the refractory materials containing high temperatures may form an impurity liquid phase, the formation of the impurity quantity of the liquid phase, the viscosity decreases with the increase of the temperature is faster, the more serious the creep.

The grain boundary of the refractory material in the pores or cracks can be directly caused by grain boundary sliding. In addition, in the high temperature materials in liquid phase to solid phase permeable pores in, especially to the infiltration of 25 mu m or less, in the small pores, thus holes exist, through the liquid phase migration also influence of creep. Therefore, the material porosity has great influence on the creep. Improve the porosity, actually can increase the creep rate.