Nanocarbon containing low carbon Al2O3-C refractories: Comparison between N220 and N990 nanocarbons

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.

Automated summary

Continuous casting is a widely used solidification process in steel fabrication. In this process, alumina-carbon-based refractories are commonly used. However, the steel industry now requires low carbon content refractories to produce clean steel and ultralow-carbon steel. This study explores the use of two different grades of nanocarbons in Al2O3-C refractories, and finds that nanocarbons can improve strength, inhibit oxidation, and provide corrosion resistance due to the formation of dense microstructures.