9th ECCC European Continuous Casting Conference – ECCC 2017

Non-metallic large inclusions are detrimental to most physical and chemical properties of steel and require a removal treatment. Inclusions can provide crack nucleation sites, surface defects, corrosion sensitivity and will reduce mechanical properties. Gas stirring in the ladle is commonly used in secondary steelmaking to homogenize chemical composition of alloy elements and temperature and to promote inclusion floatation. Ladle bottom gas bubbling is effective in removing none wetted inclusions by two main mechanisms. By the collision and adhesion mechanism, the inclusions will attach to the gas bubbles and rise with them and float up with them with higher velocity than an inclusion alone. Secondly the buoyant plume created by gas bubbles will generate recirculation flow patterns in the ladle, which enhances turbulent mixing to homogenize the chemical composition and temperature, and helps to accumulate and drag and direct the inclusions to the top slag layer and then to be removed. For the inclusion floatation, a relatively low inert gas flowrate is necessary to prevent breaking the ladle slag layer. In JSW Vijayanagar steel plant, in addition to the gas injection during the secondary metallurgy, ladle purging has been also evaluated during the teeming of the vessel. Numerical simulations have been conducted to determine the best location(s) of the purging plug(s) for optimal deoxidation inclusion floatation. The required gas flow rate has been computed in relation to the remaining steel weight. In parallel, gas injection inside the tundish has been assessed and the removal efficiency of de-oxidation + re-oxidation related inclusions has been compared with the ladle and the results presented in this article.