Using Physical Simulation for Assessing the Effect of Teeming Method and Rate on the Core Zone Formation in Large Ingots

The effect of teeming method and teeming rate exerted on the solidification and formation of core zone in large ingots have been studied. The investigation has been performed based on physical simulation, for which a laboratory-scale facility (a crystallization mold) making it possible to visualize and monitor the solidification and structural formation of model ingots has been designed and constructed. Sodium thiosulfate (crystalline sodium hyposulfite) Na 2 S 2 O 3 ⋅5H 2 O has been used as a model solution. The correspondence between the processes occurring under the model and real conditions of casting industrial ingots has been evaluated using similarity criteria obtained based on the dimension theory considering physicochemical processes occurring in the ingot under teeming and crystallization. Such two methods as downhill casting and uphill casting have been used in order to teem the melt into the mold. During teeming, the geometrical and technological parameters of the model ingots remained unchanged while varying teeming rate. The core zone length and medium width have been measured for the model ingot. The thermal profiling of the mold model surface has been monitored within the entire solidification time for to evaluate the thermal field varying in the course of ingot teeming and crystallizing. The processing of thermal imaging patterns has made it possible to observe the temperature change on the surface of the model mold throughout the ingot height for downhill cast ingots teemed at different rates. The analysis of the results has demonstrated that the melt teeming rate exerts a significant effect on the core zone length. It has been established that decreasing melt teeming rate leads to an increase in the directional character of crystallization and improving core zone structure.