The Active Part Of Refractory Bricks — Magnesia Alumina Refractory Bricks

In the production of refractory bricks, it is necessary to stabilize their refractory temperature, shock resistance, heat resistance, etc. The reason for focusing on these aspects is that this cannot be separated from the main points in the production process of refractory bricks.
However, PER refractory plant technicians introduce alumina or bauxite clinker in the ingredients to improve the thermal shock resistance of magnesia bricks, forming a magnesia-alumina spinel matrix. Thus, magnesia-alumina bricks are made.
Magnesia-aluminum bricks are alkaline refractory products with magnesia as the main crystalline phase and magnesia-alumina spinel as the matrix, also known as the first generation of magnesia-spinel bricks.

In the production of magnesia-aluminum brick, in order to make magnesia-aluminum spinel uniformly distributed in the matrix of the brick, we generally use magnesium sand-high alumina bauxite in the cylinder mill together with fine grinding. The amount of high alumina bauxite added is generally calculated according to the products containing 7%~8% Al2O3.
Magnesium aluminum brick material particle composition strictly adopts the “two big, middle small” principle of proportioning, to ensure the number of large particles and fine powder, reduces the middle particles. Common fine grinding powder in the ingredients must be added to adapt to the Al2O3 content and particle composition of the fine powder content.
When producing magnesia-alumina bricks, CaO content should be strictly limited in raw magnesium sand, because CaO forms calcium-magnesium olivine (CMS) in magnesia-alumina bricks, 1% of CaO forms 2.8% CMS. the more CMS, the more amount of liquid phase appears at high temperature, which is an important reason why it belongs to one of the many classifications of shaped refractory bricks.
For example, in the MgO-MS-MA system, the liquid phase starts at 1700°C. In the presence of CMS, the liquid phase appears at 1500°C. In the MA-CMS binary system, the liquid phase appears at 1410°C only.
At the same time, the solution formed by high CaO content has small viscosity and good fluidity, which will obviously lower the load softening temperature. Therefore, the C / S ratio of magnesium sand and the absolute content of CaO should be strictly controlled in order to improve the high-temperature performance of the products. The firing temperature of magnesia-alumina brick is about 30~50℃ higher than common magnesia brick, and the rest firing system is the same as common magnesia brick.

The main fiber structure of magnesium aluminum brick is characterized by uniformly dispersed in situ reaction spinel in the matrix, the general crystal size is less than 20mm. magnesium aluminum brick has good slag resistance, high-temperature performance, and thermal stability, the price is cheaper than magnesium spinel brick.
Once widely used in steelmaking blast furnace roofs, now still used in steel ladles, steelmaking furnace permanent lining, glass kiln heat storage chambers, mixed iron furnaces, steelmaking reflection kiln roofs, and refractory industrial high-temperature kilns.