High aluminum refractory
Alumina refractory is a kind of engineering ceramics with alumina as the main component and a small amount of other materials. Alumina is one of the most stable oxides, with high hardness, high strength and resistance to spalling. It is insoluble to water and superheated steam, as well as to most inorganic acids and bases. Alumina refractory not only has the characteristics of refractory clay bricks, but also remains stable in the higher temperature range and is suitable for furnace linings with temperatures up to 3350°F. It has high erosion resistance in oxidizing and reducing atmospheres and is widely used in the thermal processing industry.
The refractories of high alumina refractories increase with the increase of alumina content. The 50%, 60%, 70% and 80% alumina grades contain a corresponding proportion of alumina, respectively, with an allowable error of plus or minus 2.5%.
According to the American Society for Materials and Testing (ASTM) standards, high aluminum bricks are divided into the following categories according to their alumina content:
1. Mullite refractory: Mullite refractory bricks contain approximately 72% alumina and 28% silica. They have excellent volume stability and strength at high temperatures. They are very suitable for the top of electric furnaces, blast furnaces and blast furnace furnaces, and the upper structure of glass pot furnaces.
2. Corundum refractory: Corundum refractory refers to the refractory containing more than 99% alumina. Such refractories include monocrystalline, polycrystalline and α-alumina. High alumina bricks are commonly used in cement, lime and ceramic kilns, glass storage tanks, crucibles for melting various metals, furnaces and shaft furnaces of blast furnaces, and lead slag furnaces.
3. These materials are very economical to use in the lower part of the immersion tank in the steel industry, mainly because of their erosion resistance to iron slag. The production cost and price of high aluminum refractories increase with the increase of alumina content, so it is necessary to determine the most suitable alumina content for each use by experiment or test.
Magnesia brick
Magnesium refractory is a kind of basic refractory with magnesium oxide as the main component and containing more than 85% magnesium oxide. They are made from natural magnesite (MgCO3) and silica (SiO2). High-quality magnesia bricks usually consist of a low CaO-SiO2 ratio of ferrite and a minimal amount of ferrite, especially when the furnace lining is operating under oxidation and reduction conditions.
The physical properties of such bricks are generally poor, but they have strong erosion resistance to alkaline slag, especially to stone ash slag and iron-rich slag. This kind of refractory brick is the most important refractory material in the steelmaking process. In addition to metallurgical furnaces, magnesia bricks are now successfully used in glass tank inspectors, lime kilns and cement kilns. Raw magnesite (MgCO3) is usually used in light or heavy fired form. Light burned magnesite is used for sewage treatment, compound fertilizer and chemical raw materials.
Refired magnesite is a widely used raw material in refractory industry. Recently, in order to further improve corrosion resistance, people began to use fused magnesia, high crystallinity magnesite sinter and high purity magnesite sinter. Fused magnesite is produced by fused refractory grade magnesite or other magnesite precursors in electric arc furnaces. The fuse is removed from the arc furnace, cooled and crushed. The material is used in the production of refractory materials.
Refractory products – Dolomite bricks
Dolomite refractory is a kind of alkaline refractory with calcium oxide and magnesium oxide as the main components. They are formed from natural dolomite (CaCO3-MgCO3) by high-temperature calcination. The CaO+MgO content of high purity dolomite is greater than 97%. Dolomite refractory is considered to be the most compatible material with cement kiln clinker because of its excellent coating stability and very good resistance to thermal shock and alkali attack under different kiln operating conditions. These zirconia-rich refractories can be used to prevent cracking.
Chromite refractory
Chromium-magnesium refractory and magnesia-chromium refractory are two different refractory materials.
Chromium-magnesium materials typically contain 15-35% Cr2O3 and 42-50% MgO; Chrome-magnesia refractories are used in key parts of high temperature furnaces. These materials are resistant to corrosive slag and gases and have a high refractoriness.
Magnesium-chromium refractories contain at least 60% MgO and 8-18% Cr2O3; Magnesium-chrome refractories are suitable for the highest temperatures and can come into contact with the most basic slag used in steel smelting.
The spalling resistance of magnesium-chromic materials is usually better than that of chrome-magnesium materials.
Refractory products – zirconia refractory
Zirconia refractory is a kind of polycrystalline material. There are some difficulties in its use and manufacture as a refractory material. It must be stabilized before it can be used as a refractory. This can be achieved by adding small amounts of stabilizers such as calcium, magnesium and cerium oxide. Its performance mainly depends on the degree of stability, the amount of stabilizer and the quality of the original raw material. Zirconia refractories have very high fire resistance. Their strength at room temperature can be maintained up to 2700°F. Therefore, they can be used as high-temperature building materials for furnaces and kilns. The thermal conductivity of zirconia refractories is much lower than that of most other refractories, so it is used as high temperature insulation refractories. Because zirconia has very low heat loss and is not easy to react with liquid metal, it is particularly suitable for the manufacture of refractory crucible and other containers for metallurgy. Zirconia is a useful refractory for glass furnaces, mainly because it is not easily soaked by glass melts and has a low reaction with glass melts.
Amorphous refractory is a general term for amorphous refractory products that are constructed in some form of suspension and eventually solidified into solid blocks. Most amorphous refractory formulations consist of large-particle refractories (aggregates), fine-particle refractories (filling the Spaces between particles), and binders (holding the particles together in their unsintered state). Amorphous refractories are replacing traditional sintered refractories at a faster rate in many applications, including industrial furnaces.
There are a variety of construction methods for amorphous refractory materials, such as ramming method, spray method, spray method, and so on. The ramming method is mainly used in cold applications where proper consolidation of the material is very important. The same method can be used for both air-set and heat-set materials. Need to select the appropriate tamping tool.
