A new model with varied thermal-physical parameters in which the existence of airspace resulting in heterogeneous heat transfer and the latent heat of fusion at the solidification front was considered was developed.The results showed that the simulated temperature of the billet was well in agreement with the measured one.On-line control method to secondary cooling zone of continuous caster for square billet-target surface temperature control can realize the real-time control for surface temperature.Shell thickness of the billet was investigated based on the developed model.Aimed at the squre billet in continuous casting in the third metallugical plant of the capital steel group

the effects of drawing velocity and overheating on surface temperature and solidification of the billet were analyzed.The influences of different control methods on surface temperature of succeeding cooling loops were discussed for fluctuation of water supply of a certain cooling loop.By consideration of the mutual conjunction among different cooling loops and varied production conditions

simulated results showed that the model is better beneficial to the stabilization of the surface temperature and improvement of the billet quality.