Study On The Quantitative Model Of Centerline Defects Based On Numerical Simulation Of Thermal And Stress

Continuous casting, a technology to produce steel has developed rapidly these years both in domestic and foreign factory. It's application makes the process of steel manufacture more efficient, more controllable, more environmental friendly. But many key techniques are not perfect and need optimization.As well known, the process of continuous casting is so complicated that the traditional mathematical model of solidification needs optimization. Based on the data measured from the line, a new suitable model for the specific process is proved. Consequently, the solidification process of the billet affected by the process parameters such as casting speed, Moulding temperature, cooling water are analyzed.Centerline shrinkage and segregation are the main defects of continuous casting billet. The electromagnetic stirring (EMS) and soft reduction (SR) applied on the final stage of solidification have obvious effects on improving the interior quality. However, according to the numerical simulation, they could not apply simultaneously restricted by the equipments.In this paper, based on thermal-stress models and shrinkage criterion functions, a new quantitative model is proposed. Compared with the traditional criterion functions, such as Niyama criterion function, it takes into account mushy zone's pressure and fluid, which could improve the process of solidification and control the centerline defects. The simulation based on the quantitative model gains directional result. It reveals that in order to secure internal quality, the soft reduction should be applied on the position where the interior mushy zone almost lost it's fluid, and the solidification end is the crucial position where the soft reduction must be applied.