Abstract

Permeability is a very important property of refractory materials. For example, it plays a key role in the dewatering of refractory castable, in the oxygen pick up by submerged nozzle during the steel continuous casting or in corrosion of refractory linings by gases (Na2O, K2O,…). On the other hand, permeability to liquid plays a key role in the resistance to the penetration of corrosive fluids. For example, the corrosion of high-alumina refractory bricks and alumina-magnesia in situ spinel castables used in steel ladles by slag involves reactive impregnation where the slag impregnation is driven by the capillary suction and limited by the liquid permeability.

Dedicated permeameter has been designed to perform gas permeability measurements. The pressure drop and the flow rate can be controlled to perform test in viscous conditions and active Klinkenberg’s effects. Liquid permeability can therefore be accurately derived from gas permeability measurements.

The objectives of this work were:

 i) To demonstrate the reliability of the new permeameter and the possibility to measure accurately the permeability . The measurements were carried out on an alumina based refractory Low Cement Castable (LCC).

ii) To evaluate the impact of the corrosion on the gas and liquid permeability of the LCC by measuring the property before and after corrosion. The corrosion tests were performed with industrial slags coming respectively from steel and energy production. The permeability measurements were complemented with microstructural examination by means of Scanning Electron Microscope (SEM) and porosimetry measurements. Finally the characterization of the pores configuration and the permeability results could be correlated.

The infiltration behavior was observed to depend strongly on the basicity of the slag. In the case of a low basicity, the reaction of the matrix with the corrosive species is accompanied by the penetration of the molten slag into the refractory castable, filling and clogging the porosity. The corroded microstructure exhibited consequently a decreased permeability, which could be established accurately thanks to permeability measurements performed in viscous conditions.