The use conditions and raw material selection of the refractory castable in the impact zone of the ladle.
The ladle is an important thermal equipment in the steelmaking system. The inner lining of the ladle bears the erosion and impact of molten steel and molten slag for a long time. With the continuous progress of steelmaking technology, the proportion of refined steel has been increasing, which puts forward higher and higher requirements for the performance of refractory materials in the ladle. Because it directly affects the life of the ladle and the stability of production. Years of application practice have shown that the most economical use of ladle is to match materials reasonably according to the different use requirements of each part. In order to synchronize the life of each part of the ladle, reduce the number of minor and intermediate repairs.
The Use Conditions and Requirements of the Castable in the Impact Zone of the Ladle
- The temperature of molten steel. The tapping temperature of the converter is 1650℃~1680℃.
- Directly bear the impact of molten steel in the converter. The ladle contains 95t~105t of steel, the molten steel has a drop of about 5m, and each ladle has an assessment of 70 times.
- The residence time of molten steel in the ordinary ladle, including pouring time, is about 60 minutes/time.
It can be seen that the castable in the impact zone of the bottom of the ladle should have high refractoriness, high thermal strength, excellent thermal shock resistance, slag resistance, and corrosion resistance of molten steel. Therefore, its service life should be synchronized with the ladle wall.
Selection of Raw Materials for Ladle Castables
The raw material of ladle castable (https://refractorycastablecement.com/refractory-castable-manufacturer/steel-ladle-castable/) is generally high alumina spinel, which is proved to be suitable after years of actual application experience. Relevant studies have shown that the reaction of Al2O3 and MgO to produce spinel has a large volume expansion, adding an appropriate amount of pre-synthesized spinel to the matrix can reduce excessive expansion and promote sintering. And when the spinel is added in the form of a fine powder, it can absorb a large amount of iron oxide in the slag, solidify the iron oxide, and slow down the penetration of the slag. In addition, by adding Al2O3 fine powder to the matrix ingredients, on the one hand, a mineral phase in which spinel and corundum coexist is formed in the matrix; on the other hand, the CaO in the slag and the Al2O3 in the fine powder form needles to make the pores finer. Both of these factors can inhibit the penetration of slag, thereby improving the corrosion resistance of the castable.
In summary, we can make the system highly purified and improve the material quality without greatly changing the material system of the castable. Some high-alumina materials are replaced by corundum, and sintered magnesia is replaced by fused magnesia, the addition of fine powder is optimized, and fine powder of fused corundum and spinel with an average particle size of less than 5μ is introduced.
In addition, adding an appropriate amount of industrial Cr2O3 as a modifier can supplement the lattice defects of Al2O3 and activate the Al2O3 lattice. Because Cr2O3 and Al2O3 and other oxides form an infinite solid solution or a compound with a high melting point at high temperatures, it has a small thermal expansion value. At the same time, the addition of Cr2O3 promotes the absorption of iron by the spinel and increases the viscosity of the slag. When it is evenly distributed in the material matrix, the high-temperature performance and corrosion resistance of the material can be improved.
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