Enhancing mechanism of improved slag resistance of Al2O3-spinel castables added with pre-synthesized (Al,Cr)2O3 micro-powder

In order to enhance the slag resistance of Al2O3-spinel castables, (Al,Cr)2O3 is added into Al2O3-spinel system as a pre-synthesized micro-powder. Firstly, (Al,Cr)2O3 micro-powder is synthesized by sintering under reduction conditions to prevent the formation of hexavalent chromium. The Al2O3-spinel castables are prepared using tabular alumina, fused spinel, alpha-Al2O3 micro-powder, calcium aluminate cement and (Al,Cr)2O3 micro-powder as the raw materials. The bulk density, porosity, mechanical properties, and slag resistance of the samples are tested. Afterward, the effects of (Al,Cr)2O3 micro-powder (0-3 wt%) on the slag resistance and microstructures of the Al2O3-spinel castables are assessed by X-ray diffraction (XRD) and energy-dispersive (SEM-EDS) analysis. The results show that the addition of (Al,Cr)2O3 micro-powder can could inhibit the deteriorating effects of Cr3+ on the mechanical properties of the samples. The microstructure results also shows that with the addition of the (Al, Cr)2O3 micro-powder, a secondary solid solution of Ca(Al,Cr)12O19 formed, causing the unit cell to become larger. In the slag erosion area, CA6 crystals formed with network-like interwoven structures, high density, and greater thickness. These characteristics significantly reduce the erosion and permeability indices of the castables, and improve the slag erosion resistance of the material.