Yaowu Wei

Lightweight cordierite–mullite refractories with low coefficients of thermal conductivity and high mechanical properties

Lightweight cordierite–mullite refractories with low coefficients of thermal conductivity (CTCs), high strengths and high thermal-shock resistances were prepared using porous cordierite ceramics as aggregates. Phase compositions and microstructures of lightweight refractories were measured by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), etc. The effect of the relative mullite content of matrix (RMCM) on the microstructures and properties of lightweight refractories was investigated. It was found that the RMCM has a strong effect on the CTC and the mechanical properties. With an increase of RMCM, the compressive and flexural strengths of specimen increase. The thermal-shock resistance is the highest when the RMCM is 22 wt%, and also improved slightly when the RMCM is 46 wt% comparing with the specimen without mullite. When the RMCM is 46 wt%, the CTC reaches the minimum. Specimen with the RMCM of 46 wt% is the most appropriate mode, which has a moderate apparent porosity of 30%, a high compressive strength of 135.1 MPa, a high flexural strength of 20.5 MPa, a good thermal-shock resistance and a low CTC of 0.61 W mK−1.

Investigation on Slag Resistance of Magnesia Based Castable Containing SiC

Corrosion of four magnesia based castables with different SiC contents by ladle slag was conducted using the static crucible test. Effect of SiC content on the slag resistance of castables was investigated by XRD, SEM, EDAX. The reactions between refractories and slag were simulated through FactSage® thermochemical software. It has been found that SiC can increase the penetration resistance of magnesia based castables, not decreasing their corrosion resistance. With increasing the content of SiC, the SiO2 content and the viscosity of penetrated slag increase. The lower wettability of slag to SiC and the higher viscosity of penetrated slag affect the penetration resistance of magnesia based castables, whereas the reactions between slag and castables affect the corrosion resistance of magnesia based castables. The thermochemical simulation helps to understand the reaction mechanism.