Since the 1990s, lightweight castables have begun to rise. The early lightweight castables mainly used fly ash, float beads, ceramsite fibers, high-aluminum lightweight aggregates, etc. as aggregate powders to produce lightweight castables. However, in the process of use, its low temperature, poor thermal shock stability and low strength restrict the development of lightweight castables. Lightweight and high-strength castables are based on bauxite-based corundum hollow spheres as lightweight aggregates, calcium aluminate cement as binder, homogenized bauxite fine powder as matrix, and functional additives are introduced to enhance the thermal shock resistance of the castable. and flexural strength at medium and high temperature.
Take a steel mill’s use of light-weight and high-strength castable ladle capping as an example: the automatic ladle capping system uses light-weight and high-strength casting, which can reduce the tapping temperature by 8°C to 15°C. Take an empty ladle of 120 tons of this steel as an example: the next furnace of molten steel can be cooled by 17°C to 19°C within 20 minutes. Therefore, in order to keep the pouring temperature unchanged, the tap temperature of the converter can only be increased, and this measure brings a lot of energy consumption and material loss.
It can be seen from the above table that the temperature drop of using light and high-strength castables from tapping to the end of refining is 90 °C compared with the temperature drop of molten steel without capping, and 99 °C without capping. °C. The temperature drop at this stage differs by 9°C.
The use of lightweight and high-strength castables can cover the vacancy time within 4 hours, without off-line baking, and can be used in a converter. After the light and high-strength castable is used to cover, the temperature of the empty ladle will drop by 300 °C after 9 hours of vacancy, and the ladle covering agent can be omitted after the cover is applied.
