Study of ingots solidification kinetics based on physical modelling of casting and melt crystallization

Study of the processes, taking place at the large ingots obtaining during steel casting, as well as during its solidification is a rather hard task. Therefore it is reasonable to use for the study of them methods of solidification modelling by application various hard particles (inoculators), being introduced into a melt. Evaluation of the inoculation effect on the solidification process, structure formation and defected zones extension in model ingots carried out. It was determined, that introduction of inoculators during melt casting results in decreasing of the diphasic zone thickness. It was determined also, that introduction of hard particles (inoculators) in the volume of from 6 till 12% results in reducing time of model ingots solidification. An increase the volume of inoculators leads to prevalence of solidification vertical component over the horizontal one. It was determined also, that introduction of inoculators allows increasing the solidification process orientation, that characterized by an increase of linear taper and as a result – the vertical solidification component increase. It was revealed, that introduction of inoculators at the liquid-solid casting leads to changing the heat center location. The introduction of inoculators results to “elongation” of heat center by the solidifying ingot axis, that relates with a quicker advance of the solid phase in vertical direction, as a result of the quick removal of solidifying ingot overheating.

Study of the Hot Top Performance with Various Heat Insulators

The paper contains a thermal performance calculation which proves that the basic items of heat loss include heat losses spent heating the hot top casing and lining. If thermal insulation is used, losses through the metal mirror do not exceed 3.5%. It is shown that in order to improve hot top efficiency it is required to minimize losses spent on heating the lining and the hot top casing; consequently, the amount of the heat transferred to the solidifying ingot can be increased. The assessment of the performance of the hot top with various heat insulators proves that the most efficient one is the untapered (straight) hot top insulated with the MKPB-340 inserts: in this case the quantity of heat transferred to the chill amounts to 70% of the overall value. An alteration of the hot top insulation type and geometry makes it possible to improve hot top thermal performance. As a result, the heat center of the solidifying ingot shifts to the hot top. Consequently, the shrinkage of solidifying steel is efficiently compensated, which decreases the physical and chemical heterogeneity of the billets produced and improves the ingot-to-product yield.

Castings Dimensions Influence on the Alloyed Layer Thickness

The paper presents the results of simulation of alloy layer formation process on the model casting. The first aim of this study was to determine the influence of the location of the heat center on alloy layer’s thickness with the use of computer simulation. The second aim of this study was to predict the thickness of the layer. For changes of technological parameters, the distribution of temperature in the model casting and temperature changes in the characteristic points of the casting were found for established changes of technological parameters. Numerical calculations were performed using programs NovaFlow&Solid. The process of obtaining the alloy layer with good quality and proper thickness depends on: pouring temperature, time of premould hold at the temperature above 1300°C. The obtained results of simulation were loaded to authorial program Preforma 1.1 in order to determine the predicted thickness of the alloy casting.