Description：The tundish is an important thermal equipment for the high temperature molten steel after smelting to enter the continuous casting process. In order to improve the flow state of the liquid in the tundish under the action of the kinetic energy of the ladle injection, the refractory lining of some large-capacity tundishes is also equipped with a short Retaining walls and slag retaining walls. The role of the tundish slag retaining wall is to reduce the entry of non-metallic inclusions into the mold and improve the internal quality of the continuous casting billet, especially for aluminum killed steel with high aluminum content. The slag retaining weir is composed of aluminum-magnesium, magnesium-based refractory castables or castable preforms.
Title：Magnesium refractory castable for tundish slag weir
Keyword：Tundish, slag weir, magnesia refractory castable
There are two types of refractory materials for the tundish slag retaining weir: aluminum-magnesium and magnesia; the cost of magnesium-based slag retaining weir is lower than that of aluminum-magnesium slag retaining weir. Its performance and metallurgical effect are: it has the best hot strength at working temperature; it has high strength when immersed in molten steel; the oxygen content brought into the molten steel is reduced by 80% than that of high aluminum; at the same time, it can absorb the inclusions in steel Al2O3 , Forming magnesium-aluminum spinel on the surface to prevent further penetration of slag.
Magnesia refractory castable retaining wall uses electro-dissolved magnesia or high-purity sintered magnesia as the main raw material, adding an appropriate amount of Uf-SiO2 micropowder and α-Al2O3 micropowder to the matrix, and adding a certain amount of water reducing agent to vibrate by pouring It is made by low-temperature firing after molding. The addition of SiO2 micropowder can significantly reduce the hydration of MgO particles in the magnesia refractory castable, and greatly reduce the pulverization and cracking of the magnesia refractory castable during the baking process; at the same time, the addition of Uf-SiO2 micropowder can be combined with MgO and MgO. The H2O reaction produces MgO-SiO2-H2O gel combination; in addition, the introduction of SiO2 powder can also make the castable have good fluidity.
Studies have shown that although SiO2 powder can promote the growth of magnesium-aluminum spinel in the castable, it will also generate a certain amount of low-melting liquid phase in the material, which will adversely affect the slag resistance of the material. Usually, the amount of addition is not More than 2%. Adding an appropriate amount of Al2O3 powder to the matrix can use Al2O3 powder to improve the fluidity of the castable. At the same time, MgO and Al2O3 generate spinel MgAl2O4 at high temperatures, resulting in a volume expansion of about 8%, which can reduce the porosity of the material and reduce the slag Infiltrate and increase the content of magnesium-aluminum spinel in the matrix, so as to strengthen the matrix and improve the high-temperature mechanical properties of the material. Studies have shown that the addition amount of α-Al2O3 micropowder is about 8%.
See Table 1 for physical and chemical indexes of slag retaining weir for tundish.