Flow Dynamics and Inclusion Transport in Continuous Casting of Steel

The quality of continuous cast steel is greatly affected by fluid flow in the mold region, especially involving transient phenomena and the transport of inclusion particles. As part of a long-term effort to develop and apply comprehensive models of these and other phenomena, this paper reports on studies to evaluate the relative accuracy of models of three different fluid flow phenomena in continuous casting through comparison with measurements. Firstly, transient flow simulations of velocities in the mold region previously validated with digital particle image velocimetry (PIV) measurements in a single phase water model are applied to inclusion transport. Specifically, particle trajectories are calculated in transient flow fields resulting from Large Eddy Simulations (LES). The results are compared with water model measurements to study the distribution and flotation removal of inclusion particles. The LES model was able to match the measurements both qualitatively and quantitatively. Secondly, steady, multiphase flow computations are compared with flow patterns observed in both a water model and an operating steel caster with argon gas injection. For the same conditions, the water model and steel caster produced very different flow behavior. The computational model was able to match the measured flow patterns in both cases. Thirdly, transient LES simulations of impinging jets are performed and applied to predict heat transfer to surface. This is important for the prediction of shell thinning and breakouts. The angle of jet impingement against the narrow face also appears to have an important influence on the fraction of inclusion particles transported down deep into the caster, where they may become entrapped to form defects. This work suggests that computational flow modeling has the potential to match real processes as well or better than water models, especially when complex related phenomena such as particle motion and multiphase flow are involved. The models will be further improved and applied in future parametric studies. B.G. Thomas and S.P. Vanka, 2002 NSF Design, Service, Manufacturing and Industrial Innovation Research Conf., San Juan, Puerto Rico, January 7-10, 2002. 2