Preface
Meet 1100 degrees of refractory bricks there are many, cheap clay bricks, good high alumina bricks, mullite bricks, silica bricks magnesium bricks, expensive electrofusion bricks, etc. The choice of refractory brick temperature is only an indicator. But also according to the working conditions, environment, operating characteristics, etc. to choose.
According to the definition of refractory refractories greater than 1580 degrees inorganic non-metallic materials and products. Refractories refers to the temperature of the material under the action of high temperature to reach a specific degree of softening, it marks the performance of the material to resist the action of high temperature.
Refractory bricks need to withstand very high temperatures, and people also need them to work properly even at high temperatures. Therefore, in the weight per unit volume, the density is high, so that can indicate that the denseness of the refractory brick is good, and the strength it brings may be high.
After, refractory firebricks for which the porosity is also a higher requirement.
However, today people need to do specific requirements in the industrial production process, but a manufacturer shall strictly control the apparent porosity has a very high quality. On the other hand, the thermal shock resistance of this material is very good, it is resistant to rapid changes in temperature without being destroyed.
Therefore, it can be concluded that the refractory brick has the characteristics of unit volume weight, high density, good denseness, and high strength.
Common Silica-Alumina Refractory Bricks
Silicon-aluminum refractory bricks are based on the basic theory of the AL2O3-SiO2 binary system phase diagram, mainly including the following.
1. Silica Bricks
Silica brick refers to the refractory brick containing SiO293% or more and is the main variety of acid refractory brick. It is mainly used for masonry coke ovens, but also used in a variety of glass, ceramics, carbon calciner, refractory bricks of the vault of the hot work kiln, and other load-bearing parts. In the hot air furnace of the high-temperature load-bearing parts also used, but should not be used in the hot work equipment below 600 ℃ and temperature fluctuations.
2. Clay Bricks
Clay bricks are mainly composed of mullite (25% to 50%), glass phase (25% to 60%), and square quartz and quartz (up to 30%).
Usually, hard clay is used as raw material, pre-calcined to mature material, then with soft clay, shaped by semi-dry or plastic method, and fired at 1300–1400 C to make clay brick products. Can also add a small amount of water glass, cement, and other binding agents made of non-fired products and indefinite materials.
It is commonly used in refractory bricks in blast furnaces, hot blast furnaces, heating furnaces, power boilers, lime kilns, rotary kilns, glass kilns, ceramics, and refractory brick firing kilns.
3. High Alumina Bricks
The mineral composition of high alumina brick is corundum, mullite, and glass phase, and its content depends on AL2O3/ SiO2 ratio and the type and quantity of impurities. And the grade of refractory brick can be classified according to AL2O3 content.
The raw materials are high alumina bauxite and silica-like natural ores, but also mixed with electrofused corundum, sintered alumina, synthetic mullite, and clinker calcined with alumina and clay in different proportions.
It is mostly produced by the sintering method. But the products also have fused cast bricks, fused granular bricks, unfired bricks, and unshaped refractory bricks. High alumina bricks are widely used in the steel industry, non-ferrous metal industry, and other industries.
4. Corundum Bricks
Corundum refractory brick refers to AL2O3 content of not less than 90%, corundum as the main material phase of a refractory brick, can be divided into sintered corundum brick and electrofusion corundum brick.
What are The Performance Requirements of Refractory Bricks?
Porosity
The porosity in refractory bricks includes open and closed porosity. Porosity generally refers to the percentage of the volume of the visible pores in contact with the atmosphere and the total volume of the product, also called visible porosity. The smaller the porosity of the product, the better the thermal conductivity and the higher the compressive strength, but the resistance to rapid cold and heat is poor.
Bulk density and true density
Bulk density is the number of masses per cubic meter of fireproof brick including all the porosity, while the volume of the firebrick sample includes only the rock part when calculating the true density. Since the true density of different crystalline quartz forms is different. Therefore, the true density of the brick can be understood by its firing. Better-fired silica bricks have a smaller true density.
Normal temperature compressive strength
The product in the room temperature unit area can withstand large pressure, called room temperature pressure strength. The structure is uniform and dense, and the products with good firing have high room-temperature compressive strength.
Thermal expansion
It is usually expressed by the average linear expansion rate in a certain temperature range.
Thermal conductivity
Refers to the performance of refractory bricks in transferring heat. It is expressed in terms of thermal conductivity and its unit is W/(m-℃). Brick with low porosity and dense structure has good thermal conductivity. The crystalline structure has better thermal conductivity than the glassy one.
The thermal conductivity of most refractory bricks, such as silica bricks and clay bricks, increases as the temperature rises. But there are a few refractory bricks (such as magnesium bricks and silicon carbide), but the thermal conductivity decreases as the temperature rises.
Fire resistance
Fire resistance indicates the resistance of refractory bricks to softening (melting) at high temperatures, and refers to the temperature at which the top of the refractory cone specimen is bent down and touches the side of the chassis.
Load softening temperature magic
Indicates the ability of the refractory brick to resist temperature under a certain load. Load softening temperature is the specimen under 0.2MPa pressure, heated at a certain rate of heating, as the temperature rises, the specimen continues to produce deformation. When the specimen’s large height is reduced by 0.6% of the temperature, that is the load softening temperature.
It is related to the chemical properties of the refractory brick, the crystalline structure characteristics, the viscosity of the glass phase at a certain temperature. The relative ratio of the crystalline phase to the glass phase, the firing temperature, and the particle size composition.
High-temperature volume stability
The volume stability of refractory bricks is usually expressed in terms of residual expansion (or shrinkage) when the bricks are used at high temperatures for a long time.
The specific index is refractory firebrick at a certain temperature, heating at a certain time, natural cooling, measuring its volume change, and the value of the percentage of the original volume, known as residual expansion (or residual shrinkage).
Thermal stability
Refractory brick resistance to rapid changes in temperature without damage. The test method is to put half of the specimen into the heating furnace, the other half outside the furnace, heated to 850C when holding for 40 minutes. And then put into the flow of cooling water tank in the rapid cooling, so repeatedly. When the mass of the damaged and detached part is 20% of the mass of the original specimen, the number of times of rapid cooling and rapid heating.
It is closely related to the size of the expansion coefficient of the product, the unevenness of the internal temperature distribution of the product, and the shape and size of the product.
Erosion resistance
Refractory brick at high temperatures to resist the chemical and physical effects of slag, furnace decomposition products performance.
The main factors affecting erosion resistance are the chemical composition of the product and the slag, the working temperature, the nature of the decomposition products of the furnace charge, and the denseness of the product.
Therefore, according to the definition of refractory materials, refractory bricks are shaped refractory materials. Ordinary refractory products are basically all able to meet the high-temperature requirements of 1100. If the refractory clay bricks can meet the requirements of use do not use high alumina bricks.
