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.

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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.