Nanocarbon containing low carbon Al ₂ O ₃ –C refractories: Comparison between N220 and N990 nanocarbons

Abstract

Continuous casting process is the majorly used solidification process in steel fabrication. The refractories used in this process are most commonly made up of alumina‐carbon‐based compositions. Generally, these functional refractories consist of about 30% residual carbon after coking. Improvements in steel industries, such as attaining clean steel and ultralow‐carbon steel, require alumina‐carbon refractories with low carbon content. In the present work, low carbon‐containing Al2O3–C refractories are studied by using two different grade nanocarbons, namely, N220 and N990 with varying amounts, along with fixed 3‐wt% graphite in the batch composition. The physical, mechanical, and thermomechanical properties along with the oxidation resistance are evaluated and compared. Phase analysis and microstructural developments at different temperatures were also characterized. Optimized compositions of both the nanocarbons are further studied for hot strength and oxidation resistance measurement. Based on all the obtained results, one batch composition is finalized for the thermal shock and corrosion testing. All the results are compared against a reference batch composition containing 25% graphite as a carbon source. The formation of in situ ceramic phases like aluminum carbide in nanocarbon‐containing compositions provides a dense compact microstructure that improves strength, helps to inhibit oxidation, and contributes to corrosion resistance.

Use of alumina dispersant in alumina‐spinel castable: Comparison between in situ and preformed spinels

“…The impurity phases, namely, lime, silica, and iron oxide, have come from the slag only, indicating the reaction of these impurity phases with the matrix phase of the castable, resulting in the formation of lowmelting liquid phases in the castable matrix. The presence of porous structure, primarily in the slag corroded zone, may be associated with the solidification of molten phases on the refractory surface 45 as shown in Figure 15A. Further, the presence of spinel phase in the composition is found to be beneficial for the refractory as spinel absorbs the impurity elements, like Fe, as shown in Figure 17B, wherein EDAX analysis shows a minor presence of Fe within spinel grain.…”