Effect of molten metal addition in the overflow section on the behavior of convective flows during solidification of model ingots
摘要
This work presents the investigation of the influence of increasing the temperature of the melt and the holding time before refilling the overflow section of the ingot on the behavior of convective flows (descending and ascending) during the solidification of model ingots. The study was conducted using the method of physical (cold) modeling on a flat mold model (mold-crystallizer). A scaled model of a forging ingot weighing 19.6 t was used as an analog. The setup allows for the visualization of processes occurring during the solidification and structure formation of a forging ingot made of calm steel. A pentahydrate solution of sodium thiosulfate (Na2S2O3·5H2O) was used as the modeling solution. The pouring of the melt into the mold-crystallizer was performed from above. This work is a continuation of previously published studies on the influence of differential pouring technology on the solidification and structure formation processes in forging ingots. The study shows that for all model ingots, the maximum velocity of convective flows is observed at the initial stages of solidification, which is caused by the kinetic impact of the falling stream on the solidifying melt within the ingot. After the pouring of the melt into the ingot body is completed, the velocity of the descending flows rapidly decreases. Refilling the overflow section of the ingot with melt after various time intervals leads to an increase in the velocity of both descending and ascending convective flows. It was established that the maximum increase in the velocity of convective flows occurs when 50% of the solid phase is formed. Further solidification results in a decrease in the descending flows, while the velocity of the ascending flows increases. Increasing the interval between refilling the overflow section with melt to 40 min results in a 1.4-fold increase in the solidification time of the model ingot. It was determined that raising the temperature of the added melt portions leads to a greater difference between the velocities of the ascending and descending flows.