Improvement in Slag Resistance of No-Cement Refractory Castables by Matrix Design

Abstract

The corrosion resistance of spinel containing cement bonded castables has been extensively investigated in the past. However, corrosion of no-cement refractory castables (NCC) has not been widely studied since the use of NCC has been relatively limited up till now. This paper focuses on the slag resistance of NCCs, and the often-used spinel containing low cement castable (LCC) is used as the reference. Three different NCC binders were designed: (i) Al₂O₃ + MgO (alumina bond), in situ spinel formation; (ii) Al₂O₃ + SiO₂ (microsilica-gel bond), mullite formation; and (iii) Al₂O₃ + MgO + SiO₂ (MgO-SiO₂ bond). Slag resistance tests were conducted using the static crucible method with ladle slag. The corrosion mechanisms were studied by means of Scanning Electron Microscopy (SEM/EDS), X-ray Diffraction (XRD), and thermodynamic simulations. The results confirmed that the mineral phases, microstructure, and liquid formation at a high temperature of the refractory materials had a strong impact on the corrosion resistance. The slag resistance was significantly improved when the cement was replaced by the cement-free binders.