Influence of Wettability and Reactivity on Refractory Degradation – Interactions of Molten Iron and Slags with Steelmaking Refractories at 1550°C

Refractories, materials that can withstand high temperatures, play an important role in the iron and steel sector which alone accounts for ~70% of total refractories pro‐ duced. In this chapter, detailed wettability and interfacial phenomena investiga‐ tions on alumina-carbon and zirconia-carbon refractories at steelmaking temperatures. The wettability between refractory substrates and molten iron/slags was investigated at 1550°C using the sessile drop approach in a horizontal tube fur‐ nace equipped with a CCD camera. Detailed experimental results were obtained on alumina-carbon/molten iron system at high temperatures. Alumina is known to be non-wetting to molten iron while carbon can be easily wetted. Observed contact an‐ gles were found to depend strongly on the substrate composition and contact time. While the refractory substrates containing 50 and 60% carbon were found to be nonwetting to molten iron, the substrates containing higher amounts of C (≥ 70%) were found to become increasingly wetting. Molten iron droplets were seen to spread on these substrates. The wettability of zirconia-carbon and alumina-carbon (C: 10-20 wt %) with two steelmaking slags (Slag 1: MnO: 50%, SiO2: 25%, Al2O3:25%, and Slag 2: MnO: 40%, SiO2:60%) was investigated at 1550°C. The wettability with Slag 1 was found to be‐ come poorer with increasing carbon content in the refractory; however a complete wetting was observed after 20 minutes of contact. Slag 2 showed a better wettability with higher carbon refractories. The extent of gasification of ZrO2 – C system was found to be 9 times higher than the Al2O3 – C system. At ~5 minutes of contact, the slag appeared to get lifted away from the substrate leading to a slowing down of slag penetration. The maximum height of the gaseous gap decreased with increas‐ ing carbon in the substrate [880μm, 630μm & 440μm respectively for 20%, 15% & 10% carbon in the substrate]. The formation of the gaseous gap between slag 1 and the substrate was attributed to poor wetting and gas pressure. Slag 2 did not exhibit the formation of a gaseous gap due to lower contact angles between the slag and refractory. Alumina – carbon showed higher contact values but no gas gap forma‐ © 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. tion was detected. The absence of gaseous gap was attributed to insufficient gas generation in this case.