Development of porous refractory ceramic plugs: Will the next generation be 3D printed?

Abstract

Controlling non-metallic inclusion content during secondary metallurgy is a key feature in ensuring the quality of steel. In a typical process, these particles are captured by bubbles generated by a ceramic porous plug located at the bottom of the ladle, whose structure consists of open pores that allow gas injection into the molten bath. Nevertheless, during the non-bubbling period, liquid steel can penetrate through this porous structure, solidifying at the colder plug regions. In order to withdraw this infiltrated thickness, an oxygen lance heats the surface of the porous plug to resume its operation for the next process run. This cleaning procedure is pointed out as the leading wear mechanism for such a refractory. A classical approach to understand the infiltration of a liquid in a porous structure is based on Washburn's equation, which defines the starting condition for liquid penetration. By applying the same fundamentals to this problem, a criterion to avoid liquid steel infiltration into the plug is set. In this study, the influence of the pore diameter, the material composition, the gas counter-pressure and the ceramic structure tortuosity on steel penetration was analysed. Based on these results, feasible routes were proposed as countermeasures to refrain the molten metal infiltration of porous refractory ceramic purging plugs.