Simultaneous enhance of the thermal shock resistance and slag-penetration resistance for tundish flow-control refractories: The role of microporous magnesia

Abstract

As the low thermal shock and slag-penetration resistance of the magnesia castables cause the premature failure of tundish flow-control devices leading to the pollution of steel, the microporous magnesia with high closed porosity and intergranular CaZrO3 phase was utilized for simultaneously enhancing the high-temperature performance. The thermomechanical stress and slag corrosion tests indicated that since the micro-closed pores effectively relieved the thermal stress and CaZrO3 absorbed massive crack-propagation energy, the cold modulus of rupture and residual strength ratio respectively reached 14.4 MPa and 73.4% after thermal shock cycles, nearly half higher than that of the fused magnesia based castables. Meanwhile, the synergistic effect of micro-closed pores and intergranular CaZrO3 phase significantly reduced the slag-wettability, improved the interfacial energy and dihedral angle, leading to the decline of slag penetration indice (decreased by ∼34.8%). This study suggests a potential approach to generate new magnesia based castables in tundish for making clean steel.