(STSI-109)NUMERIC MODELLING OF THE INFLUENCE OF MOULD SLAG FILM FLOW ANDMOULD SLAG-RADIATION INTERACTION ON HEAT TRANSFER IN THECONTINUOUS CASTING MOULD

摘要

A 2D numeric model for the shell growth in the mouldduring continuous casting has being developed withthe long term goal to become a tool for understandingand improving continuous casting practice. Thepresent model is limited to steady state simulationsand has been used to simulate heat flow andtemperatures in the melt/shell/slag/mould system.Comparison with in-plant measurements of the mouldtemperatures via thermocouples near the mould/slaginterface has made it possible to deduce approximatevalues for the heat transfer coefficient in the “gas gap”between slag film and copper mould and get goodcorrespondence with measured heat fluxes.The model contains treatment of turbulent and laminarflow, heat conduction and radiation with absorptionand scattering. Accurate modelling leads to degreesof freedom of typically one million or more in the 2Dcase and long computing times. It is therefore ofcrucial importance to understand the influence ofthese physical phenomena and their possibleapproximate treatments on the predictive power of thenumeric simulations.In the present work the model has been used toinvestigate the contribution of mould slag laminar flowand radiation on the heat flux and, in addition, theeffects of possible model simplifications on the heatflux value. Modelling of mould slag flow and radiationboth substantially increase computing time and theneed for primary memory due to the fine meshingnecessary in the mould slag region.The mould slag laminar flow has been modelleddriven by gravity and the contact with the moving shelland takes place in a typically 0.1 mm thick regionadjacent to the shell. It is concluded that the verticalflow of the mould slag has a negligible convectivecontribution to the horizontal heat flux and thereforecan be omitted from the model causing a few percenterror in the heat flux.On the contrary, simplified modelling of the radiationcauses larger errors and has to be judged from caseto case.