Influence of thermal diffusion on decarburisation of iron–chromium alloy droplets by oxygen–argon gas mixtures

Using an electromagnetic levitation technique, the kinetics of decarburisation of Fe–Cr–C alloy droplets by oxygen–argon gas mixtures containing up to 10 vol.-% oxygen was investigated at 1873 K. The observed decarburisation rates were less than predicted using conventional formulation of governing mass transport numbers. It is hypothesised that the effects of thermal diffusion caused by the steep temperature gradient (∼1550 degrees) between the incoming gas stream and the surface of the droplet, is responsible for the difference observed between the well established mass transfer model and the experimental data for decarburisation kinetics. This finding has important implications with respect to the application of appropriate mass/heat transport equations when using commercial software to model pyro-metallurgical processes, such as stainless steel refining, where large temperature gradients are an inherent component of the system.