As the main component of the indefinite refractory, the amount of refractory aggregate is generally 60%-73%, and the amount of refractory powder is 15-40%, both of which have a significant impact on the performance of the indefinite refractory. So what are the commonly used raw materials for refractories?
1. Bauxite clinker
Bauxite clinker is made of bauxite ore after high temperature calcination, and its Al2O3content is generally more than 50%. In the unshaped refractory materials, it is common to process bauxite into refractory aggregate and powder. In important parts or parts in direct contact with the hot work equipment of steel and iron, high quality high alumina bauxite clinker should be chosen as refractory aggregate and powder.
2.Layey raw materials
Clay materials and refractory clay, divided into hard clay and soft clay and semi-soft clay. Hard clay is mostly kaolinite single mineral type precipitated clay, generally need to be calcined into clay clinker before use. Clay clinker is also known as coke clinker. In unshaped refractories, clay clinker is generally used only as a refractory aggregate. Soft clays are mainly kaolinite-type clays, which are easily dispersed in water, have high plasticity and adhesion, and have good sinterability at high temperatures. Soft clay does not need to be calcined, but can be used after drying and grinding. It is a binding agent for producing aluminous silicate bricks and is also one of the good binding agents for irregular refractory materials. Semi-soft clay is also kaolinite type, mainly used as clay clinker or finely ground as binding agent.
3. Semi-siliceous raw materials
Semi-siliceous raw materials mainly include natural chlorite and siliceous kaolin, etc., which are semi-acidic refractory materials. Chlorite can be made into ladle lining bricks, but also as an aggregate of indefinite refractory materials, can be used directly, but also after calcination. When siliceous kaolin is used as refractory aggregate and powder, it is mainly used in medium and low temperature parts.
4. Silica raw materials
Silica raw materials are crystalline silica, colloidal silica and vein quartz, collectively known as silica. Refractory materials with silica, SIO₂ content should be greater than 96%. When silica raw material is used to make unshaped refractories, it should be added with used silica bricks as refractory aggregate and powder, or with mineralizing agents such as iron scales to generate a certain liquid phase. In order to buffer the stress produced by crystalline transformation, and at the same time can promote the transformation of quartz to stable scaled quartz and square quartz.
5. Magnesia class raw materials
Magnesian raw materials are magnesium sand, dolomite, magnesium olivine and serpentine, etc., are alkaline, also known as alkaline refractory raw materials.
(1) Magnesium sand
Magnesium sand is magnesite or magnesium oxide extracted from seawater, salt lake water through sintering or electrofusion. Divided into sintered magnesium sand and electrofusion magnesium sand.Magnesite sintered product in 800-1000℃ temperature, collectively called light sintered magnesite, is the binding agent of magnesium refractory products, also is the raw material of magnesium cement. Sintered magnesite sand is the product of full sintering under the temperature of 1600-1900℃. Seawater magnesia sand is sintered from seawater magnesium oxide by high pressure into ball or mass at 1600-1800℃ temperature. Salt lake magnesia sand is made by heating the by-product after extracting potassium and sodium salt from lake water to 600-800℃ to get MgO after dehydration and then calcination.
(2)Electrofused magnesium sand
Electric fused magnesite sand using selected magnesite or sintered magnesite sand in the electric arc furnace by 2500 ℃ high temperature melting made. It is a good raw material for advanced carbon-containing not burned brick and unshaped refractory materials. In the magnesium sand with the right amount of dolomite and iron scale made of high iron magnesium calcium sand, can be used for electric furnace bottom pounding material and rapid replenishment of furnace material.
Sintered dolomite is also known as dolomite clinker. Its and synthetic magnesia dolomite is the main raw material for steelmaking furnace lining brick, also used to fill the furnace material. In the unshaped refractory materials, mainly as refractory aggregates.
In the magnesium peridotite refractories, mainly with peridotite and pure peridotite as raw materials. Peridot may not be calcined directly for refractory aggregates.
Serpentine in 600-700 ℃ temperature calcination will begin to dehydrate, the formation of magnesium olivine and other minerals. Serpentine must be calcined before use. It can be used for brick making, as refractory aggregate or even heat furnace auxiliary base material.
6. The blue crystal family of mineral materials
The sapphire group of minerals is the precipitate of the primary clay material generated by metamorphosis. After burning, the sapphire mineral products are the high quality raw materials of unshaped refractories and high alumina refractory products.
Mullite is generally synthetic, and the production processes are sintering and electrofusion. High purity, low creep rate, low thermal expansion, good resistance to thermal shock, strong resistance to chemical erosion and other characteristics. It is widely used in the refractory industry.
Corundum is generally made of industrial alumina or bauxite after sintering or electrofusion. Bauxite as raw material, can be obtained from ordinary corundum. Adding iron filings is, can produce brown corundum. When zircon or zirconium oxide is added, zirconium corundum is obtained. Adding other minerals can improve the properties of corundum. At present, corundum is used more and more as refractory aggregate and powder, and the effect is remarkable.
9. Industrial alumina
Industrial alumina is produced by the Bayer process with bauxite as raw material. It can be used as refractory powder or superfine powder. In recent years, there are also refractory castables with ultra-micro powder for binding agent.
10. Spinel-type materials
Spinel refers to all minerals belonging to the spinel family, but a narrow sense of spinel system refers specifically to magnesium aluminum spinel. Magnesia spinel structure is strong, high melting point, low thermal expansion, low thermal stress, good thermal shock resistance, strong resistance to alkaline erosion. The sintered and electrofused spinel refractory industry is developing relatively rapidly.
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