[China Aluminum Network] High-alumina bricks, common materials used to produce MgO-Cr2O3 products are mainly magnesia, chrome ore, synthetic magnesia-chromium sand, and sometimes some additives are added. Sintered magnesia and fused magnesia with different MgO content (generally greater than 89%), in combination with refractory chrome ore with different Cr2O3 content, chromium concentrate, sintered or fused magnesia chromite (sometimes adding a little Chromium green) can produce many kinds of magnesium chromium products. High alumina brick production process essentials are as follows: The content of MgO in the ingredients is 60%-70%, Cr2O3 content is 8%-12%. A typical formula for high alumina bricks is: Xinjiang chrome ore 2.0 - 0mm, 25% - 35%; magnesia 3.0 - 0mm, 40% - 45%; magnesia fines, 20% - 30% . The mixing, forming and drying of high-alumina bricks are the same as those of magnesium bricks. Then, in the production process, unless you want to weigh the chemical industry, you should also pay attention to the following points.
(1) Influence of chromium ore and magnesia ratio on chromium-magnesia refractories Practice demonstration that when the ratio of chrome ore and magnesite is 50:50, the product has a high thermal shock stability, followed by chromium ore and magnesium As the quality increases or decreases, the thermal stability decreases. When the chromium ore content is too high, the ability of the article to counterbalance the effectiveness of the iron compound at 1650°C will drop dramatically. Chromium ore particles can form a solid solution with Fe2O3, resulting in rapid expansion of the volume, resulting in product explosion phenomenon. The higher the content of chromium ore in the furnish, the more serious the explosion phenomenon. The mobilization of magnesium content in the ingredients can enhance the slag resistance of the products.
(2) Effect of matrix mineral synthesis on product performance The important mineral synthesis of magnesium-chromium products is periclase and spinel. The matrix portion is synthesized from silicates. Important minerals in the silicate matrix are M2S, CMS, C3MS2 and so on. In addition to M2S, CMS and C3MS2 are low-melting minerals, so the CaO content in the raw materials should be limited, and the matrix ore in the brick should be made into a highly refractory M2S.
(3) Influence of Ambient Properties When the magnesium-chromite refractories are fired in a reducing atmosphere, at 650°C, solid phase contrast of MgO in the magnesia fine powder replaces FeO in the coarse-grained chromite ore. The volume is reduced by approximately 24.3%. Such a large volume reduction causes firing cracks. In the combined atmosphere, FeO in the chrome ore is already combined with Fe2O3 at 500°C to form (Fe, Cr)2O3 solid solution, and the volume is reduced by 1.5%, and FeO is replaced by FeO in the combined atmosphere to synthesize Fe2O3, followed by MgO concluded magnesium ferrite, which was only 6.6% of the total volume of the two linings. According to this, chromium-magnesia refractories should be fired in a weak chemical atmosphere.
In general, because chromium ore contains low-cost iron, residual carbon cannot easily be burned out during preheating when the waste liquid of the pulp slurry is used as the slag forming agent. The high-alumina brick code bricks should be left with a large fire path, which should be reduced appropriately. Brick density, and mobilize bricks in the pre-tropical heating rate. The firing temperature of high-alumina bricks is generally between 1550 and 1600°C. Under the premise of ensuring the shape accuracy of products, the firing temperature is higher.
