Determination of optimal taper in continuous casting billet mould using thermo-mechanical models of mould and billet

An industrial continuous casting process of steel billet is analysed using numerical models for the heat transfer and mechanical deformation in the mould and billet. Elastoplastic thermo-mechanical model, including creep and thermal stresses, is developed to determine the temperature and stress fields, and the resultant deformation in the mould. A three-dimensional, turbulent flow model is also developed to simulate fluid flow and solidification of the molten steel as it flows inside the mould. The heat transfer at the mould-billet interface is decoupled using a heat flux profile obtained from inverse heat transfer calculations, developed in an earlier work. Temperature measurements made in the industrial billet mould have been used for this purpose. Important results from the models are discussed to gain understanding of the physical aspects governing the casting process. The distortion profile of the mould and the thermal shrinkage of the billet are used to determine an optimal taper for the mould. Two separate taper profiles are suggested for the corner and off-corner regions around the mould periphery, due to the different nature of the heat transfer in these regions. Finally, these two profiles are compared with the existing single tapered profile for the operational mould in the industry. It is observed that the existing profile has significantly less taper in the meniscus region which can lead to higher air gap and subsequent defects in casting.