Experimental and numerical study of calcium treatment of steel

This paper presents the laboratory scale experiments of calcium release in liquid steel and its modeling to better understand the mass transfer mechanism occurring during calcium treatment of steel. The calcium injections are performed at the liquid steel temperature below and above the boiling point of calcium (1484 °C). The corresponding yields (calcium recovery) are compared. The objective is to confront the experimental results with the results of the numerical model developed. Rise of calcium droplet in liquid steel is a three-phase problem (calcium droplet/liquid steel/air at the top) therefore an in-house scientific computational platform based on finite element methods is adapted to allow the modeling of such three-phase flows, which is validated using classical bench mark issued from literature. Mass transfer model is first validated by comparison with the analytical solution obtained for a motionless calcium droplet dissolving in stable liquid steel. This case study highlighted the importance and sensitivity on the prediction of concentration profile near the interface with numerical parameters, such as the mesh size. The case of mass transfer for a rising liquid droplet in a liquid matrix is also simulated. The accordance between the calculated Sherwood number and the Sherwood number found in the literature demonstrates the ability of the model to predict the mass transfer rate occurring at the interface. © EDP Sciences, 2019.