Numerical studies on the parameters influencing steel ladle heat loss rate, thermal stratification during holding and steel stream temperature during teeming

Numerical experiments were performed on fluid flow and heat transfer in 107-tonne steel ladles by 3-step implementations of numerical models. In the first step, a 1-dimensional numerical model was used to predict heat conduction fluxes through the ladle wall, bottom and top slag layer. In the second step, by means of computational fluid dynamics (CFD) modelling and employing the predicted heat loss fluxes as thermal boundary conditions, a 2-dimensional CFD model was applied to simulate natural convection in steel ladles during the holding period before teeming. In the third step, a 3-dimensional CFD model was implemented to further simulate fluid dynamics in the same ladles with drainage flows during teeming. Using these mathematical numerical models, the bulk cooling rate of the steel melt, the extent of thermal stratification during holding and the steel stream temperature during teeming were investigated for 2 types of 107-tonne steel ladles lined, respectively, with alumina and spinel in walls. In these investigations, the following 4 parameters were considered: (i)ladle lining inside surface (hot-face) temperature before tapping, (ii)top slag layer thickness, (iii) holding time and (iv) teeming rate. An important result of these investigations is that the concerned parameters all significantly influence the steel stream temperature during teeming, and the differences in teeming stream temperatures among different ladles, caused by these parameters, can be up to 20 deg C, which may be essential to temperature control in tundishes during continuous casting.