In order to improve the thermal shock resistance of magnesia bricks, more and more magnesia alumina brick companies have introduced alumina or bauxite clinker into the ingredients to form a magnesia alumina spinel matrix to make magnesia alumina bricks. Magnesia alumina brick is an alkaline refractory product with periclase as the main crystal phase and magnesia alumina spinel as the matrix, also known as periclase spinel brick. Ramming material

In the production of magnesia alumina bricks, in order to make the magnesia alumina spinel evenly distributed in the matrix of the brick, magnesia-high alumina bauxite is generally used for fine grinding in a barrel mill. The adding amount of high alumina bauxite is generally calculated based on the product containing 7% to 8% Al2O3. The particle composition of magnesia-aluminum bricks must be proportioned strictly according to the principle of "big at two ends and small in the middle" to ensure the quantity of large particles and fine powder and reduce intermediate particles. The amount of common finely ground powder added in the ingredients must be adapted to the Al2O3 content and the fine powder content in the particle composition. When producing magnesia alumina bricks, the content of CaO in the raw magnesia should be strictly limited, because CaO forms magnesia olivine (CMS) in magnesia alumina bricks, and 1% CaO forms 2.8% CMS. The more CMS, the more liquid phase appears at high temperature. For example, in the MgO-MS-MA system, the starting temperature for the formation of a liquid phase is 1700°C. When CMS exists, a liquid phase will appear at 1500°C. The temperature at which the liquid phase appears in the MA-CMS binary system is only 1410°C. At the same time, the solution formed due to the high content of CaO has low viscosity and good fluidity, which will significantly lower the load softening temperature. Therefore, the C/S ratio of magnesia and the content of CaO should be strictly controlled to improve the high temperature performance of the product. The firing temperature of magnesia alumina brick is about 30~50℃ higher than that of ordinary magnesia brick, and the other firing system is the same as ordinary magnesia brick.

Magnesia alumina bricks have good thermal shock resistance, high temperature mechanical strength, and high load softening temperature. The main fiber structure feature of magnesia alumina brick is that the in-situ reaction spinel is evenly dispersed in the matrix, and the crystal size is generally less than 20mm. The magnesia alumina brick has good slag resistance, high temperature performance and thermal stability, and the price is higher than that of magnesia spinel. Bricks are cheap, and layer tube rice is used on the top of steel-making open-hearth furnaces. It is still used in ladle, permanent lining of steel-making furnaces, regenerators of glass kilns, iron mixers, steel-making reflex kiln roofs and high-temperature furnaces in refractory industry.