Advantages of unshaped lining for ladles
Magnesia-carbon brick (MgO-C) has been used as the inner lining of ladle refractory materials for many years. In the 1980s, Japan developed a magnesium-aluminum spinel castable with prefabricated spinels for use in ladles. In the 1990s, in situ spinel composition was formed in the second-generation lining with fine magnesium oxide and activated alumina added to the matrix.
Different spinel castable materials are used in different ladle areas. At the bottom of the ladle, especially the breathable bricks and wall tiles, the volumetric stability of the ladle under high temperature and pressure is the most important. In the process of high-speed refining of molten steel and when blowing in low-temperature stirring gases, its high corrosion resistance and thermal shock resistance are also very important. Castable containing prefabricated spinel has become the standard for this application and provides optimal performance.
The requirements for ladle side walls vary. Since each steel clad case has some deformation after transportation, storage and treatment, and the inner lining is not absolutely rigid, one of the advantages is to avoid cracks caused by stress peaks through stress relaxation. Adding silicon powder to the castable formed by spinel to form a liquid phase will cause the castable to soften (a sharp drop in the RUL curve) to release thermal stress. The volume expansion caused by the formation of in situ spinels can close the joints on the surface. Therefore, castable formed with spinel brings some advantages to the ladle side wall. In this paper, it is believed that the combination of containing spinel and forming spinel is the best solution.
Keyword：Ladle refractory lining, kiln, Magnesia carbon brick, Spinel castable，Unshaped lining
Realed product：Magnesia carbon brick
The replacement of magnesia-carbon bricks with unshaped lining at the bottom and side walls of the ladle has brought many advantages to the steelmaking process, mainly as follows:
(1) The use time of the ladle is extended;
(2) The total number of ladle operations is reduced by 20%;
(3) Compared with MgO-C bricks containing toxic and carcinogenic substances (phenolic resin, coal tar asphalt, etc.), the castable does not have any harmful materials.;
(4) Reduce the unit cost of steel production;
(5) Produce ultra-low carbon steel in a better operating environment, because there is no carbon increase in the refractory material of the ladle;
(6) The unit consumption of refractory materials is reduced by more than 50%.
Compared with other amorphous liners, the last advantage is the most important.
Technically, the unit consumption of refractory materials is reduced by more than 50%, which is based on the concept of seamless lining. When the inner lining of the ladle uses magnesia-carbon bricks and when the service life of the bricks is reached, it will be replaced by a new set of MgO-C bricks. However, for the amorphous lining, the situation is completely different. During the first installation, the amount of castable is the same as that of brick. When the lining is replaced at the bottom and side walls in the future, if the brick lining is used, all the lining needs to be replaced. If unshaped refractory materials are used, only part of the lining in contact with molten steel (about 40% to 60%) needs to be replaced, and the undamaged lining will remain in place. Refractory materials can be saved by using unshaped liners until the end of the ladle operation and before all the inner liners of the ladle, including the necessary safety working layers, are fully updated.