High alumina refractory bricks are a type of refractory material, and the main component of this type of refractory brick is Al2O3.
If the Al2O3 content is higher than 90%, it is called corundum brick. Due to different resources, the standards of various countries are not completely consistent. For example, European countries stipulate that the lower limit of Al2O3 content for high-alumina refractory materials is 42%. In China, high-alumina bricks are usually divided into three grades according to the Al2O3 content in them: first-grade high-alumina bricks-Al2O3 content ≥75%; second-grade high-alumina bricks-Al2O3 content ≥ 65%; third-grade high-alumina bricks-Al2O3 content ≥55%; Al2O3 content less than 48% is called clay refractory bricks.
Since the main raw material of high-alumina bricks belongs to aluminum stone, its main content is composed of aluminum oxide, iron oxide, silicon oxide, etc. If aluminum oxide and silicon oxide are used to distinguish the grades of high-alumina bricks, then iron oxide is an impurity in high-alumina bricks. Many people will raise a question, what effect does the iron content in high-alumina bricks have on their performance?
The iron content in high-alumina bricks has a huge impact on its performance. The iron element in high alumina refractory bricks can reduce its refractoriness. The main reason is that iron oxides are easy to form a low-melting point liquid phase at high temperatures. At the same time, iron elements are easy to react with other substances in a high-temperature environment, thereby changing the internal structure of high-alumina bricks, resulting in a decrease in their high-temperature strength. A high iron content will increase the thermal conductivity of high-alumina bricks, resulting in faster heat transfer and affecting their insulation effect and energy utilization efficiency. Therefore, in the production process of high-alumina bricks, there are strict requirements on the impurity content in the raw materials.
In the production process of high-alumina bricks, the iron content of some common high-alumina bricks with high aluminum content is fixed. For example, the raw material of 48% high-alumina bricks uses 60% high-alumina bauxite clinker, and the iron content must be within 3.0%; the raw material of 55% high-alumina bricks uses 65% high-alumina bauxite clinker, and the iron content must be within 2.5%; the raw material of 65% high-alumina bricks uses 75% high-alumina bauxite clinker, and the iron content must be within 2.2%; the raw material of 75% high-alumina bricks uses 85% high-alumina bauxite clinker, and the iron content must be within 2.0%; the raw material of 80% high-alumina bricks uses 88% high-alumina bauxite clinker, and the iron content must be within 1.5%. Therefore, strict control of iron content is very necessary for the quality of high-alumina bricks.
How to control the iron content in high alumina refractory bricks requires not only control of the raw materials, but also control of the production process. At present, raw material manufacturers usually control the iron content in the raw materials through ore dressing, purification, iron removal and other processes to meet the requirements of producing different grades of high alumina bricks and ensure that high alumina bricks can perform well in the corresponding environment. In the production process, the raw material ratio must also be controlled to reduce the iron content in high alumina bricks. This is not only to ensure the quality of high alumina bricks, but also very necessary in the production process of other refractory materials.
