In order to improve the service life of the LF refined ladle and meet the purity requirements of clean steel, the brown corundum-based corundum spinel brick for the LF refined ladle was developed. This refractory brick uses fused brown corundum, white corundum, and high-purity fused magnesia-alumina spinel as the main raw materials introduce an appropriate amount of active magnesia raw materials, and uses inorganic salts as binders. This product has the characteristics of no carbon increase in molten steel, erosion resistance, corrosion resistance, and high-temperature volume stability. This product has a service life of 270-300 heats below the slag line of a 330 t LF slag line in a foreign steel plant, reaching the international level of similar white corundum-based products. It is an ideal material for LF refining ladle.
Brief Introduction of Corundum Spinel Brick
Using fused white corundum, fused spinel, and alumina powder as the main raw materials, it is fired at high temperatures to produce high-purity corundum-spinel ladle lining bricks. The product has excellent performance, slag corrosion resistance, and penetration resistance. A certain amount of spinel is introduced into corundum products, and the high-purity corundum-spinel bricks produced have better slag resistance. It has been used more than 100 times, and it has achieved satisfactory results when used on the ladle, and it has been well received by users.
(1) The corundum spinel brick has high chemical purity, does not contain carbon, will not pollute the molten steel, and can meet the needs of smelting clean steel.
(2) Compared with domestic castables and prefabricated blocks for refined ladle, corundum spinel bricks are fired products with accurate dimensions and good overall consistency of the masonry. The introduction of active magnesia makes the product have stable and continuous micro-expansion, and the use of safety is higher.
(3) The structure of the ceramic bond formed by sintering is better, and the porosity in the sintered environment is better than that of the castable. The material has a strong resistance to molten steel erosion and slag erosion, and the service life of the product is better than castables and precast blocks.
(4) Compared with white corundum-based corundum spinel bricks, the service life reaches the same effect and has more cost-effective advantages.
Slag Resistance of Corundum Spinel Brick
The dynamic slag resistance experiment of corundum spinel refractory bricks was carried out using a vacuum induction furnace. By studying the corrosion of high-basicity desulfurization slag and alumina-silicon killed steel refining slag to the refractory brick, the corrosion mechanism of two alkaline slags on it is analyzed. The results show that the corrosion resistance of corundum spinel refractory bricks is better than that of high basicity desulfurization slag. The corrosion resistance of corundum spinel refractory bricks is mainly affected by the content of alumina and calcium oxide in the slag. The content of CaO, SiO2, and CaF2 in high basicity desulfurization slag is relatively high. It reacts with the Al2O3 in the corundum spinel refractory brick with a low melting point substance, which reduces the viscosity of the slag and causes serious erosion. The high alkalinity desulfurization slag contains low Al2O3 content, which leads to the direct dissolution of MgO in the spinel. The Al-Si-killed steel refining slag has a high content of Al2O3, which forms MA spinel at the MgO/slag interface, leading to indirect dissolution and inhibiting slag erosion.
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The application life of corundum spinel bricks in the ladle capacity of 330t. Smelting high-quality low-carbon steel, LF furnace heating time is 10~15 min, ladle turnover time is 2.5 h/time, ladle free part above slag line is 80 cm, ladle turnover rate is 3.75 times/day. Some surveys have compared the use effect of this refractory brick product, and the comparison results are rough as follows. This product is used in the LF furnace of a foreign steel factory, and the service life is 270~300 times. The corundum-spinel brick produced by a foreign company has been used in the same customer for 270-320 heats. Domestic W and B companies are used for low-carbon steel smelting, and the service life of 300 t ladle in the third steelmaking plant of W company exceeds 250 times. The use of low cement or ultra-low cement combined corundum-spinel castable with 300 t ladle of B company has reached 250 times.
Selection of Raw Materials for Corundum Spinel Bricks
An experiment has studied the influence of the raw material composition of corundum spinel bricks on the performance of corundum spinel bricks. The first is the selection of raw materials for corundum spinel bricks. The main raw materials used in the experiment are fused brown corundum, magnesia-alumina spinel, activated magnesia, white corundum, and high-temperature alumina powder.
The main raw materials are fused brown corundum and high-purity fused spinel. The matrix is white corundum, spinel, and high-temperature alumina powder. Use inorganic binder. The amount of active magnesia raw material added is designed to be 0, 1a, 2a, 3a. The sample numbers are 0#, 1#, 2#, 3#. To study the effect of the different additional amounts of active magnesia on the performance of the product, the sample firing system was carried out at 1500 ℃ for 10 h. Test the apparent porosity, bulk density, compressive strength at room temperature, permanent line change of heating, the high-temperature flexural strength of the sample according to relevant standards, and test the chemical composition of the sample.
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The influence of different raw materials on the performance of corundum spinel brick
According to the experimental data, different raw materials have different effects on the performance of corundum spinel bricks. conclusion as below:
(1) The influence of fused brown corundum material on the properties of corundum-spinel bricks. Fused brown corundum has the characteristics of compact structure, low porosity, high hardness, and corrosion resistance. The brown corundum pellets are designed as aggregates to build a firm structural framework for the product, improve the structural strength of the product, and reduce the porosity. The compressive strength of the sample is 100 MPa, and the apparent porosity is about 16%, which prevents the slag liquid from penetrating into the crystal grains, thereby improving the firmness of the structural frame.
(2) The influence of synthetic spinel on the properties of corundum spinel bricks. Spinel has high chemical purity, stable magnesia-alumina spinel crystal phase, and has significant corrosion resistance to alkaline slag. In particular, the scientific design of the spinel grain size has achieved good results in improving the slag resistance of the matrix. At the same time, spinel has a low thermal expansion coefficient compared with corundum and periclase, which improves the thermal shock resistance of the material.
(3) The influence of active magnesia raw materials on product performance. Because brown corundum and synthetic spinel raw materials are manufactured by electrofusion, the activity is extremely low and the structure is stable. The corundum spinel brick adopts a thousand-method masonry form, which requires the material to have a certain expansibility during the use process to maintain the integrity of the masonry. Therefore, the material reburning line is required to change to a positive value. For the 0# test corundum-spinel brick without active magnesia material, it is refired to -0.3% at 1600 ℃, which is not conducive to ensuring the integrity of the ladle in use. There may even be molten steel seepage along with the shrinking bricks, leading to “package wear” accidents. After the introduction of active magnesia material, the volume effect produced by the secondary spinelization is used to continuously expand the material within a certain range, ensuring the integrity of the tank. At the same time, the amount of spinel crystal phase is increased, which is beneficial to the improvement of slag resistance.
(4) The role of high-temperature alumina powder. On the one hand, it uses its surface activity to react with active magnesia raw materials to form secondary spinel. On the other hand, it can promote sintering to form a ceramic bonding structure and improve structural strength.
(5) The influence of binder on the performance of corundum-spinel bricks. Due to the chemical purity and use requirements, the ingredients of corundum spinel bricks did not incorporate bonded clay. The materials are all “barren materials”, which are non-plastic and difficult to form. Therefore, considering the problem of molding and manufacturing, choose an appropriate inorganic binder to increase the plasticity of the mud without causing the material to reduce its high-temperature performance. The selected inorganic binder improves the structural strength of the product through the change of the phase structure at high temperatures.
Rongsheng refractory brick manufacturer is a popular manufacturer of refractory materials. Whether in terms of product or customer service, the reputation in the industry is good. Our customers are all over the world, and we have our refractory projects in the following countries, such as Thailand, UAE, Turkey, Kuwait, South Africa, Malaysia, Vietnam, Netherlands, Philippines, Singapore, Egypt, Russia Uzbekistan, etc. If you want to know more about corundum spinel bricks for ladle or want to buy corundum bricks, high alumina bricks, magnesia bricks, silica bricks, and other refractory brick products, please contact us. We will provide you with services according to your specific needs.
