[China Aluminum Network], also known as alumina brick high-alumina refractory bricks, similar to its production and stick with a brick manufacturing process, the difference is more mixed flour mixed with high alumina clinker, refractoriness than clay brick, acid and alkali resistant invasion Good candle performance, suitable for use in various furnace firing belts, etc.
Al2O3 content of more than 48% aluminum silicate refractory bricks collectively referred to as high-alumina firebrick. According to the content of Al2O3, it is divided into three grades: I (Al2O3> 75%); II (Al2O3 60% ~ 75%); III (Al2O3 48% ~ 60%). According to the mineral composition, it can be divided into low mullite (including sillimanite) and mullite (Al2O3 48% to 71.8%), mullite-corundum and corundum-mullite (Al2O3 is 71.8%~95%), fired bricks such as corundum (Al2O3 95%~100%).
With the increase of Al2O3 content in high-alumina fire bricks, the amount of mullite and corundum components also increases, the glass phase decreases accordingly, and the fire resistance and density of high-alumina fire bricks also increase. When the content of Al2O3 in the high alumina brick is less than 71.8%, the high temperature stable crystalline phase in the high alumina refractory brick is mullite, and increases with the Al2O3 content. For high alumina refractory bricks with Al2O3 content above 71.8%, the high temperature stable crystalline phases are mullite and corundum. With the increase of 71.8%, the amount of corundum increases and the mullite decreases. Accordingly, the high temperature performance of high alumina refractory bricks is correspondingly improved.
The firing temperature of the high-alumina fire brick depends on the sinterability of the alumina raw material. When using special grade I and grade I bauxite clinker (bulk density ≥ 2.80g/cm3), the structure of the raw material is uniform and the impurity content is high, so that the green body is easy to sinter, but the firing temperature range is narrow, and it is easy to cause overheating. Not burning. When using bauxite Class II (bulk density ≥2.55g / cm3), because the secondary expansion of mullite and petrochemical effects caused by loose, so that the sintered body is not easy, so the firing temperature is slightly higher. When using Class III bauxite clinker (bulk density ≥ 2.45 g/cm3), the structure is dense, the Al2O3 content is low, and the firing temperature is relatively low. Generally, it is slightly higher than 30 to 50°C of the firing temperature of the clinker clay brick. High alumina refractory bricks are fired in an oxidizing flame.
Due to the high softening temperature of high alumina refractory brick is an important property. The experimental results show that it varies with the content of Al2O3 in the high alumina refractory bricks: When the Al2O3 content is lower than the theoretical composition of mullite, the equilibrium phase in the high alumina refractory bricks is the mullite-glass phase. The mullite content increases with the increase of Al2O3 content, and the softening temperature of the load increases accordingly.
High-aluminum refractory bricks have poorer thermal shock resistance than clay bricks, and 850°C water cooling cycles 3 to 5 times. This is mainly due to the fact that corundum has a higher thermal expansion than mullite but no crystalline transformation. Furthermore, the isothermal aluminum bricks such as I and II are inferior in thermal shock resistance than the III high alumina refractory bricks.
In the production, the method of forming a mixture of smut and mud particles is usually adopted to improve the grain structure characteristics of the high-alumina firebrick, thereby improving its thermal shock resistance. In recent years, a certain amount of synthetic cordierite has been added to the ingredients of high-alumina firebricks to produce high-heat-resistant, shock-resistant high-alumina firebricks, achieving remarkable results.
The slag resistance of high alumina refractory bricks also increases with the increase of Al2O3 content. Decreasing the content of impurities will help improve corrosion resistance.
The difference between high-alumina fire bricks and clay bricks is that high-alumina fire bricks have good serviceability and therefore have a longer service life than clay bricks, and have become one of the more widely used fire-resistant bricks in the building material industry.
The special high-alumina brick is a new type of chemically combined high-alumina fireproof brick, which overcomes the weak thermal shock resistance of the high-alumina firebrick and the low resistance of the normal temperature and compressive strength, and possesses the chemical resistance and high strength of the phosphate refractory brick. Various advantages, but also easy to hang kiln skin, is fired with a new type of firebrick. The refractory clay used for high-alumina bricks and blending methods are basically the same as clay bricks, and high-strength refractory clays can also be used.
