An original application of ANSYS simulating the forming of the temperature field of a massive casting from ductile cast-iron during the application various methods of its cooling using steel chills. The numerical model managed to optimize more than one method of cooling but, in addition to that, provided serious results for the successive model of structural and chemical heterogeneity, and so it also contributes to influencing the as solidified microstructure. The file containing the acquired results from both models, as well as from their organic unification, brings new and, simultaneously, remarkable findings of causal relationships between the structural and chemical heterogeneity and the local solidification time in any point of the casting. Therefore the determined relations enable the prediction of the local density of the spheroids of graphite in dependence on the local solidification time. The calculated temperature field of a two-ton (500 × 500 × 1000) mm casting of ductile cast-iron with various methods of cooling has successfully been compared with temperatures obtained experimentally. This has created a tool for the optimization of the microstructure with an even distribution of the spheroids of graphite in such a way so as to minimize the occurrence of degenerated shapes of graphite, which happens to be one of the conditions for achieving good mechanical properties of castings of ductile cast-iron. Key-words: ductile cast-iron, massive casting, cooling, temperature field, numerical model Uporaba originalnega programa ANSYS omogo~a simulacijo tvorbe temperaturnega polja v masivnem lito`eleznem ulitku pri razli~nih metodah hlajenja z jeklenimi hladilnimi telesi. Z numeri~nim modelom se lahko optimira ve~metod hlajenja, dodatno pa je mogo~izra~un pomembnih rezultatov za modeliranje strukturne in kemijske heterogenosti, kar tudi prispeva k vplivu na lito mikrostrukturo. Dobljeni rezultati obeh modelov omogo~ajo pomembne ugotovitve o odnosih med strukturno in kemijsko heterogenostjo ter lokalnim~asom strjevanja v poljubni to~ki ulitka in napoved lokalne gostote krogli~astega grafita v odvisnosti od lokalnega~asa strjevanja. Izra~unano temperaturno polje dvotonskega ulitka duktilne`elezove litine z izmerami (500 × 500 × 1000) mm je bilo v skladu z eksperimentalnimi rezultati pri razli~nih metodah hlajenja. Na podlagi teh ugotovitev je bilo izdelano orodje za optimizacijo mikrostrukture z enakomerno porazdelitvijo krogli~astega grafita, s~imer se zmanj{a pojav degeneriranih oblik grafita in se ustvarijo pogoji za dosego dobrih mehanskih lastnosti ulitkov duktilne`elezove litine. Klju~ne besede: temperaturno polje, strjevanje, ohlajanje, numeri~na optimizacija, strukturna in kemijska heterogenost

The paper deals with investigation into segregation behavior of selected elements in longitudinal cut of continuous steel slab, in the breakout area. The breakout occurred after a flying change of tundish in order to begin casting of another steel grade. Altogether 11 samples were taken from the part of a solidified slab. Concentrations of selected elements (Al, Si, P, S, Cr, Mn, Ni and Mo) were measured in these samples using scanning electron microscope and energy dispersive spectroscopy. Using the original mathematical models the basic micro-segregation characteristics and the parameter of macro-heterogeneity were further determined for each analyzed element. Then a quantitative measurement of inclusions ("micro-purity") in the samples was performed using a metallographic microscope. Then method of differential thermal analysis was used for the measurements of temperatures of phase transformations. The following main results were found: - magnitude of micro-segregation of the analyzed elements in the measured sections of 1000 μm is approximately the same in all the analyzed samples, - chemical macro-heterogeneity is very high across the analyzed slab section, - very uneven mixing of melts of both steels was probably one of the main causes of formation of the breakout.

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Abstract. The solidification and cooling of a continuously cast billet, slab or cylinder, generally of a concasting and the simultaneous heating of the mold is a very complicated problem of three-dimensional (3D) transient heat and mass transfer. The solving of such a problem is impossible without numerical models of the temperature field of the concasting itself which it is being processed through the concasting machine (caster). The application of the numerical model requires systematic experimentation and measurement of operational parameters on a real caster as well as in the laboratory. The measurement results, especially temperatures, serve not only for the verification of the exactness of the model, but mainly for optímization of the process procedure: real process  input data  numerical analyses  optimization  correction of real process. The most important part of the investigation is the measurement of the temperatures in the walls of the mold and the surface of the slab in the zones of secondary and tertiary cooling.