China's Refractories

Abstract: Purging plugs installed in the bottom of steel ladles are widely used for the secondary refining of high quality steel grades. The dynamic service conditions and temperature gradients caused by the cold inert gas blown through the plug during stirring create a strong thermal shock impact on the materials. This can affect its service life and restrict the safety and efficiency of steel making if the plug fails during use. In this work, the influence of the particle size distribution (PSD) and amount of reactive alumina on the sintering behavior of ultralow cement bonded corundum-spinel based castables was investigated on lab scale. The relationship between sintering reactivity of matrix and thermal shock resistance of castables was evaluated in detail. Results show that the sintering of castables can be intensified by using finer reactive alumina. However, excessive sintering of the castable through finer reactive alumina is negative for thermal shock resistance. The microstructure characterization reveals that castables with more intense sintering show denser matrix structure, which is less effective in hampering crack propagation and therefore results in decline of their thermal shock resistance.

Key words: reactive alumina, corundum-spinel castable, sintering reactivity, thermal shock resistance