Abstract <p>The results of a laboratory studies on the solidification process and development of structural zones within ingots upon adding melt to the sinkhead part in 7, 19 and 40 min after chill pouring at different values of added melt temperature (<i>T</i>_{chill. pour} = 75°C, <i>T</i>_s.h. pour = 80°C). The studies have been carried out by means of a method of physical (cold) simulation based on a flat mold model (crystallizer mold). A scale model of a forging ingot weighing 19.6 tons has been accepted as an analogue. The unit makes it possible to visualize the processes occurring during the solidification and structure formation of a forging ingot of calm steel. Sodium thiosulfate pentahydrate (Na₂S₂O₃·5H₂O) has been used as a model solution. This work was carried out in continuation of papers published earlier concerning the studies on the effect of differentiated pouring technology exerted on the solidification and zonal structure formation in forging ingots. The increase in the temperature of the melt added to the sinkhead part leads to an increase in the total solidification time of model ingots. A solidification mechanism inherent in model ingots has been determined. Topping-up the sinkhead part of experimental ingots with melt leads to a smaller development of axial friability along the ingot axis. Resulting from the suppression of the development of the zone of differently oriented crystals, the temperature of the melt added to the sinkhead part and the holding time before topping-up the melt portions exert a significant effect on the solidification mechanism and, as a consequence, on the development of the structural zones of the solidifying ingot.</p>