Phase-field modeling of steel scrap melting in a liquid steel bath

The kinetics of scrap melting is an important aspect of EAF steelmaking and has been the subject of several studies. In EAF steelmaking, there are two distinct melting mechanisms; (i) the melting of scrap by the arc through a combination of radiant and convective heat transfer and (ii) the melting of scrap immersed in a molten steel bath without direct heating from the arc. In traditional EAF steelmaking, the first mechanism dominated the melting process but with the increasing use of 'hot heel' operation and a general trend to utilization of the liquid bath as the melting medium, the second mechanism has become more important. Previous studies have focused on investigating the melting behaviour of single scrap pieces with regular shapes, though Gaye et al. did consider the physics of multi-piece scrap melting. One of the most important aspects of scrap melting in a bath that has received little attention is the agglomeration of scrap pieces even though industrial experience suggests that this is a critical aspect of understanding the kinetics of scrap melting. The effect of preheating scrap, including the formation of oxide layer, on scrap melting kinetics is another area worthy offuture attention. This study is focused on investigating multi-piece scrap melting in liquid steel by both mathematical modeling and high temperature experimentation. The study emphasizes the formation and agglomeration of solidified shells and investigates the effect of size, shape, oxidation and initial scrap temperature on melting behaviour. A new approach for modeling melting behaviour has been developed, the phase field technique, to model convective heat transfer in the case of scrap melting in a bath. The phase field model is able to deal more easily with complex geometry compared to traditional 'sharp interface' heat transfer equations where tracking the interfaces and their interactions is complex. It is expected that from this study a better understanding of scrap melting can be developed and provide insight into how to improve the melting process in an EAF.