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Study of Solidification of Continuously Cast Steel Round Billets Using Numerical Modellin

Tkadleckova M., Válek L., Socha L., Saternus M., Pieprzyca J., Merder T., Michalek K., Kováč M.

Archives of Metallurgy and Materials

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2016

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Vol. 61, iss. 1

221--226

EN

The paper is dedicated to the verification of solidification of continuously cast round steel billets using numerical modelling based on the finite element method. The aim of numerical modelling is to optimize the production of continuously cast steel billets of round format. The paper describes the pre-processing, processing and post-processing phases of numerical modelling. Also, the problems with determination of the thermodynamic properties of materials and the heat transfer between the individual parts of the casting system, including the definition of the heat losses along the casting strand in the primary and secondary cooling, were discussed. The first results of numerical simulation show the so-called thermal steady state of continuous casting. The temperature field, the metallurgical length and the thickness of the shell at the end of the mould were predicted. The further research will be concentrated on the prediction the risk of the cracks and the porosity based on the different boundary conditions.

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Model study of tundish steel intermixing and operational verification

Michalek K., Gryc K., Tkadleckova M., Bocek D.

Archives of Metallurgy and Materials

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2012

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Vol. 57, iss. 1

291-296

EN

The aim of this paper will be to present new knowledge and experience from numerical and physical modelling of metallurgical processes at the Department of Metallurgy, VSB - Technical University of Ostrava in Czech Republic and to explain especially the principle of tundish process simulations. The numerical modelling was realized by the CFD program FLUENT. The paper describes the pre-processing, processing and post-processing phases of numerical modelling. The physical modelling of the steel flow verification is based on a monitoring of the time dependency of concentration changes during experiments for individual tundish outlets. There exist two basic methods of KCl concentration change utilization in this "water" physical tundish modelling methodology. The utilization of mentioned methods are discussed and possible future developments are outlined for research of tundish steel intermixing.

PL

Celem artykułu jest przedstawienie wyników i doświadczeń z numerycznego i fizycznego modelowania procesów metalurgicznych w Zakładzie Metalurgii, VSB - Uniwersytet Techniczny w Ostrawie (Republika Czeska) i wyjaśnienie zasady symulacji procesów mieszania stali w kadzi pośredniej. Program CFD FLUENT posłużył do modelowania numerycznego. W artykule opisano pre-processing, processing i post-processing modelowania numerycznego. Weryfikację modelowania fizycznego przepływu stali dokonano w oparciu o eksperymenty, w których monitorowano zmianę stężenia w czasie dla poszczególnych stref kadzi. Istnieją dwie podstawowe metody wykorzystania zmian stężenia KCl w wodzie. Omówiono wykorzystanie wymienionych metod i możliwości przyszłego rozwoju badań mieszania stali w kadzi pośredniej.

3

Utilization of thermal analysis to thermo physical properties study of real steel grades

Klus P., Zaludova M, Gryc K., Smetana B., Michalek K., Dobrovska J., Tkadleckova M., Socha L.

Archives of Materials Science and Engineering

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2012

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Vol. 58, nr 2

116--119

EN

Purpose: This paper deals with determining the temperatures of phase transformations in real steel grades. It also includes the study of industrially produced steel grades using the methods of thermal analysis by experimental equipment STA 449 F3 Jupiter made by NETZSCH and Setsys 18TM made by SETARAM. Design/methodology/approach: Selected methods of thermal analysis (DSC and DTA) enable to obtain the temperatures of phase transformations taking place in steel during the linear heating/cooling. Within the casting technology of steel, thermal analysis is used to determine the solidus temperature and especially the crucial liquidus temperature. Findings: Experimentally obtained solidus and liquidus temperatures are higher in the DSC method (max. 3.8°C). The difference between the temperatures of phase transformation (T) running between the solidus temperature (TS) and liquidus (TL) for both methods (DTA and DSC) differ by a maximum of 3.2°C. The results from experimental measurements were compared with theoretical calculations of liquidus and solidus temperatures by different authors and with the computed results from thermodynamic database COMPUTHERM and also with temperatures from the equilibrium phase diagram of Fe-Cr-C. Experimentally obtained solidus temperatures are lower than the calculated equilibrium solidus temperatures. Experimentally obtained liquidus temperatures are in the range of temperatures obtained using computational relations. The temperatures mentioned in the equilibrium phase diagram (diagram for a particular steel grades was not found) are higher than experimentally obtained temperatures. Research limitations/implications: The results of experimental studies can be used to refine the knowledge of basic physical properties of steel and for example replacement of the tabulated values or estimated values of phase transformation temperatures and thermal capacity. Furthermore, the obtained data will be implemented in the material databases of numerical programs used for the simulation of metallurgical processes. Originality/value: On the basis of applied research in close collaboration with industry companies, the obtained data can contribute significantly to optimize the operating conditions, thereby increasing the efficiency of the steelmaking technology and final quality of cast steel.

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Evaluation of chemical heterogeneity of a 90-ton forging ingot

Machovcak P., Opler A., Carbol Z., Trefil A., Merta K., Tkadleckova M., Michalek K.

Archives of Materials Science and Engineering

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2012

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Vol. 58, nr 1

22--27

EN

Purpose: This article describes performance of the experimental 90-ton forging ingot casting, the way of cutting, the methodology of chemical analysis and the results of that investigation. Design/methodology/approach: The experimental ingot 8K91SF weighing almost 90 tons was cast due the performance a detailed analysis of the current state of casting and solidification. The ingot was cut and macrostructure and chemical heterogeneity of the ingot was evaluated in detail. The standard method used in metallurgical analytics - analyses using optical emission spectrometers - was not applicable due to the large number of required analyzes. Thus, the mobile optical spectrometer SPECRTOTEST was used. Sulfur prints and fluid penetration tests were performed due to detect macroscopic distribution of sulfur and to locate surface-breaking defects. Findings: Current level of segregations of selected elements in real 90-ton steel ingot was detected. Also mutual mixing of two heats needed for the production of this ingot was verified. Research limitations/implications: Future research is focused on determination of inclusion content in selected parts of experimental ingot and on the level of micro-segregations. We are limited by the accuracy of chosen analytical method, which is also discussed in the paper. Practical implications: The gained knowledge is used to specification of the setting of boundary conditions of the numerical simulations, which should help to optimize the production technology of casting heavy forging ingots and minimize the level of segregation in ingots. Originality/value: New knowledge concerning mutual mixing of two heats needed for bottom casting of heavy forging ingot are presented in this paper. Distribution of segregation in so heavy ingot was detected. Results are the base for further investigations in macro-segregations and for the improving the accuracy of results of numerical simulations.