Abstract

Properties and quality consistency of refractory castables are closely associated with porosity and pore size distribution. More uniform pores distribution under equivalent porosity is preferable. In this work, a kind of surfactant was introduced into alumina-spinel castable for making steel ladle integral purging plugs by pre-casting for the purpose of avoiding big pores and improving properties. The surfactant was absorbed by alumina based powders by pre-mixing them, so that it can be better dispersed in the castable by adding such powdery additive. The addition was set at 0, 1%, 2% and 3% respectively. Properties of the castables in terms of water demand, flow value, hot modulus of rupture and permanent linear change were investigated and microstructure of the samples dried and fired at different temperatures were observed by SEM. The incorporation of such agent can influence the flow behavior, properties and microstructure of the castables, while little effect on the original shaping and drying process as well as volumetric stability at high temperature. The introduction of this additive is helpful to reducing bleeding phenomenon of the castable and avoiding segregation. Hot modulus of rupture at 1400℃ can also be enhanced from 14.3MPa to 16.8MPa at 1% addition of the additive, which can be attributed to a reduction of big vacancies and an increase in smaller size pores which are more uniformly distributed in the matrix. Field test of the improved alumina-spinel castable with addition of 1% of the additive was carried out as pre-cast integral purging plugs in a 90t stainless steel ladle in Taiyuan Iron & Steel (Group) Co., Ltd. and positive results were obtained, evidenced by reduced late stage cracking and prolonged durability.