Mohsen Nouri Khezrabad
Sessions
Alumina-carbon-based refractories, due to their unique physical and mechanical properties, are widely used as sliding gates, shroud nozzles, monoblock stoppers, and sub-entry nozzles in the steelmaking industry. In this study, the effect of modified surface of nano alumina additives and their composites with multi-walled carbon nanotubes with silane group in alumina-carbon refractories was investigated.
In this regard, nano alumina was added to functionalized carbon nanotubes to prepare the nanocomposite. To achieve better distribution of the nano additives, the particles were first functionalized with APTES silane groups. Then, 1% by weight of the additive was added to the fine grain part and subsequently mixed with the coarse particles of the alumina-carbon body. For the physical and mechanical property assessments, the samples were shaped under uniaxial pressing at a pressure of 150 MPa, tempered at 200°C for 6 hours, and fired at 1450°C for 2 hours in a reducing atmosphere under a coke bed.
Apparent density, apparent porosity, and cold crushing strength (CCS) were determined according to the standards. For microstructural phenomena and phase analysis, SEM and XRD were used. The results showed that the sample containing 1% by weight of the alumina-MWCNT nanocomposite exhibited the highest cold crushing strength of approximately 156 MPa. Additionally, the Weibull modulus results confirmed this finding. According to the SEM results, the improvement in mechanical properties can be associated with the increased formation of SiC in the presence of Al2O3-MWCNT by the vapor-solid mechanism.
In production of clean steel or special grades of steel, calcium is injected during ladle furnace process in order to remove inclusions. However, normal Alumina-ZrO2-carbon slide gate plates suffer from calcium vapor attack leading to chemical corrosion and shortening the life of the plates. In this research, a new MgO-spinel-carbon slide gate plate was developed to overcome the drawback of Al2O3-ZrO2-C ones. The result was also compared to a commercially available MgO-C slide gate. In this regard, the chemical analysis, physical and mechanical properties as well as mineralogical composition of all the plates were investigated. The different corrosion mechanisms of each plate were discussed. The result showed that although the commercial imported MgO-C carbon plate had the best performance in practice, the domestically developed MgO-Spinel-carbon plates also showed much better performance than Alumina-Zirconia Carbon and can be used safely for flow control of Ca-Treated steel.