Volgograd State Technical University, Volgograd, Russia

S. B. Gamanyuk, Cand. Eng., Associate Prof., Dept. of Materials Technology, e-mail: gamanuk@mail.ru
D. V. Rutskiy, Cand. Eng., Associate Prof., Head of Dept. of Materials Technology, e-mail: drutskii@vstu.ru
N. A. Zyuban, Dr. Eng., Prof., Dept. of Materials Technology, e-mail: tecmat49@vstu.ru
M. V. Kirilichev, Head of Laboratory, Dept. of Materials Technology, e-mail: tecmat@vstu.ru

The paper presents the results of a laboratory study of the solidification process and the development of structural zones in ingots when refilling the profitable part with melt, 7, 19 and 40 minutes after pouring the ingot body at the same temperature of the refilled melt equal to 75 °C). The research was carried out by the method of physical (cold) modeling, on a flat model of a mold (mold-crystallizer). A scale model of a forge ingot weighing 19.6 tons is taken as an analogue. The installation allows you to visualize the processes occurring during the solidification and structure formation of a forging ingot of calm steel. A five-aqueous solution of sulfuric acid sodium (Na₂S₂O₃·5H₂O) was used as a modeling solution. The melt was poured into the mold mold from above. This work was carried out in continuation of previously published works on the study of the influence of differentiated casting technology on the process of solidification and structure formation of zones in forging ingots. The work shows that an increase in the holding time after filling the ingot body when refilling the melt into head contributes to the suppression of the volumetric solidification mechanism and contributes to the continued growth of the columnar crystal zone, which leads to a greater development of the columnar crystal zone solidifying by a sequential mechanism. Ingots obtained with refilling of head 40 minutes after filling the body differ from the comparative ingot in greater structural uniformity and a less developed axial zone in the body of the ingot. At the same time, the shrinkage sink is completely concentrated in the volume of the profitable part. An increase in the duration of refilling heads with melt leads to a 1.5-fold increase in the total solidification time of model ingots. The longer the holding interval between refilling the ingot with melt, the more favorable conditions are created for the development of a zone of columnar crystals and, as a result, a more homogeneous structure of the solidified model ingot. The results obtained show that the holding time before refilling portions of the melt has a significant effect on the solidification mechanism and, as a result, on the development of structural zones of the solidifying ingot. 
The research was conducted with financial support of the grant of Russian Scientific Fund No. 23-29-00973, https://rscf.ru/project/23-29-00973/.

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