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1

Numerical Modelling of Metal Melt Refining Process in Ladle with Rotating Impeller and Breakwaters

Sviželová J., Tkadlečková M., Michalek K., Walek J., Saternus M., Pieprzyca J., Merder T.

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 2

659--664

EN

The paper describes research and development of aluminium melt refining technology in a ladle with rotating impeller and breakwaters using numerical modelling of a finite volume/element method. The theoretical aspects of refining technology are outlined. The design of the numerical model is described and discussed. The differences between real process conditions and numerical model limitations are mentioned. Based on the hypothesis and the results of numerical modelling, the most appropriate setting of the numerical model is recommended. Also, the possibilities of monitoring of degassing are explained. The results of numerical modelling allow to improve the refining technology of metal melts and to control the final quality under different boundary conditions, such as rotating speed, shape and position of rotating impeller, breakwaters and intensity of inert gas blowing through the impeller.

2

Physical Modelling of Degassing Process by Blowing of Inert Gas

Michalek K., Tkadlečková M., Socha L., Gryc K., Saternus M., Pieprzyca J., Merder T.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 2

987--992

EN

This paper deals with the possibilities of using physical modelling to study the degassing of metal melt during its treatment in the refining ladle. The method of inert gas blowing, so-called refining gas, presents the most common operational technology for the elimination of impurities from molten metal, e.g. for decreasing or removing the hydrogen content from liquid aluminium. This refining process presents the system of gas-liquid and its efficiency depends on the creation of fine bubbles with a high interphase surface, uniform distribution, long period of its effect in the melt, and mostly on the uniform arrangement of bubbles into the whole volume of the refining ladle. Physical modelling represents the basic method of modelling and it makes it possible to obtain information about the course of refining processes. On the basis of obtained results, it is possible to predict the behaviour of the real system during different changes in the process. The experimental part focuses on the evaluation of methodical laboratory experiments aimed at the proposal and testing of the developed methods of degassing during physical modelling. The results obtained on the basis of laboratory experiments realized on the specific physical model were discussed.

3

Evaluation of Approaches of Numerical Modelling of Solidification of Continuously Cast Steel Billets

Tkadlečková M., Michalek K., Strouhalová M., Sviželová J., Saternus M., Pieprzyca J., Merder T.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 2

1003--1008

EN

The paper evaluates two approaches of numerical modelling of solidification of continuously cast steel billets by finite element method, namely by the numerical modelling under the Steady-State Thermal Conditions, and by the numerical modelling with the Traveling Boundary Conditions. In the paper, the 3D drawing of the geometry, the preparation of computational mesh, the definition of boundary conditions and also the definition of thermo-physical properties of materials in relation to the expected results are discussed. The effect of thermo-physical properties on the computation of central porosity in billet is also mentioned. In conclusion, the advantages and disadvantages of two described approaches are listed and the direction of the next research in the prediction of temperature field in continuously cast billets is also outlined.

4

Research and Development of the Solidification of Slab Ingots from Special Tool Steels

Tkadlečková M., Michalek K., Gryc K., Socha L., Jonšta P., Saternus M., Pieprzyca J., Merder T.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 3

1453--1458

EN

The paper describes the research and development of casting and solidification of slab ingots from special tool steels by means of numerical modelling using the finite element method. The pre-processing, processing and post-processing phases of numerical modelling are outlined. Also, problems with determining the thermophysical properties of materials and heat transfer between the individual parts of the casting system are discussed. Based on the type of grade of tool steel, the risk of final porosity is predicted. The results allowed to improve the production technology of slab ingots, and also to verify the ratio, the chamfer and the external/ internal shape of the wall of the new designed slab ingots.

5

Physical Modelling of Tundish Slag Entrainment under Various Technological Conditions

Michalek K., Gryc K., Socha L., Tkadlečková M., Saternus M., Pieprzyca J., Merder T., Pindor L.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 3

1467--1471

EN

This paper deals with the issue of physical modelling of vortexes creation and tundish slag entrainment over the mouth of the nozzle into the individual casting strands. Proper physical model is equivalent to the operational continuous casting machine No. 2 in TŘINECKÉ ŽELEZÁRNY, a.s. Physical modelling methodology and simulated operational conditions are shortly described. Physical modelling was used for the evaluation of current conditions of steel casting at the application of different impact pads in the tundish. Further, laboratory measurement on the physical model aiming the determination of exact critical periods of vortexes creation and study of the slag entrainment as a consequence of changes in surface level during the tundish refilling to standard level were realised. The obtained results were analysed and discussed.

6

Comparison of solidus and liquidus temperatures of real low carbon steel grade obtained by use of thermal analysis methods

Smetana B., Kawuloková M., Zlá S., Kalup A., Strouhalová M., Řeháčková L., Rosypalová S., Tkadlečková M., Michalek K., Dobrovská J.

Prace Instytutu Metalurgii Żelaza

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2016

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T. 68, nr 2

33--39

EN

Praca dotyczy badania temperatur przemian fazowych (temperatur solidus i likwidus) z użyciem różnych metod analizy termicznej. Obecnie kluczowymi metodami analizy termicznej są: różnicowa analiza termiczna DTA, skaningowa kalorymetria różnicowa oraz „bezpośrednia” analiza termiczna TA. Praca przedstawia podstawowe zasady, charakterystykę, zalety, wady i wyniki uzyskane przy użyciu tych trzech, bardzo często stosowanych metod. Przedstawiono wyniki z zakresu wysokiej temperatury (powyżej 1000°C) z naciskiem na zakres topnienia i krzepnięcia stali. Omówiono wyniki uzyskane przy zastosowaniu wspomnianych metod podczas procesu nagrzewania/chłodzenia, z uwzględnieniem różnych obciążeń analizowanych próbek i innych czynników, które mogą wpływać na uzyskane wyniki. Podano ocenę krzywych nagrzewanie/chłodzenie DTA i DSC. Porównano i omówiono uzyskane temperatury solidus i likwidus.

PL

The paper deals with the study of phase transition temperatures (solidus and liquidus temperatures) with the use of different thermal analysis methods. Currently, the key thermal analysis methods are DTA (Differential Thermal Analysis), DSC (Differential Scanning Calorimetry) and ‘direct’ thermal analysis (TA). The study presents the basic principles of these methods, their characteristics, advantages, disadvantages and results obtained with these three very often used methods. There paper presents results from the high temperature region (above 1000°C) with the focus on the melting and solidifying region of real steel grade – multicomponent alloy. The paper discusses results obtained with the three mentioned methods at heating/cooling process, with different loads of analysed samples and other factors that can influence the obtained results. The evaluation of heating/cooling curves, DTA and DSC – curves at heating and cooling is demonstrated. The obtained solidus and liquidus temperatures are compared and discussed.

7

Study of Tundish Slag Entrainment Using Physical Modelling

Michalek K., Gryc K., Socha L., Saternus M., Tkadlečková M., Pieprzyca J., Merder T., Pindor L.

Archives of Metallurgy and Materials

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2016

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Vol. 61, iss. 1

257--260

EN

This paper deals with the possibilities of using physical modelling to study the slag entrainment in the tundish. A level of steel in the tundish is changing during sequential continuous casting. The most significant decrease in the steel level occurs when replacing ladles. It is generally known that if the height of steel level in the tundish drops below a certain critical level, it may generate vortexes over the nozzles and as a consequence entrainment of tundish slag into individual casting strands can occur. Thus, it is necessary to identify the critical level of steel for specific operational conditions. In this paper, the development of physical modelling methodology is described as well as physical model corresponding to operational continuous casting machine No. 2 in Třinecké železárny, a.s. The obtained results are discussed.

8

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.

9

Impact of Oscillation Parameters on Surface Quality of Cast Billets

Cibulka J., Krzok R., Hermann R., Bocek D., Cupek J., Michalek K.

Archives of Metallurgy and Materials

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2016

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Vol. 61, iss. 1

283--288

EN

The paper is focused on impact of different oscillation parameters on surface quality of peritectic steel grades cast into billets 150x150 mm. Hydraulic oscillation used for this purpose was temporarily installed on one strand of the billet caster. Hydraulic oscillation enables, in comparison to ordinary used electromechanical oscillation, flexible set-up of basic parameters of the oscillation cycle (negative strip time and its ratio). Proper oscillation mode is capable to assure regular oscillation marks development, good lubrication in the mould and adequate compression of the solidifying shell. Impact of an oscillation mode providing negative strip time 0.085 s and its ratio -50 % on surface quality of cast billets is compared with standard oscillation mode applied on strands equipped with electromechanical oscillation characterized with variable negative strip time between 0.084 and 0.096 s and fixed negative strip ratio to -14 %.

10

Study of Casting and Solidification of Slab Ingot from Tool Steel Using Numerical Modelling

Tkadlečková M., Michalek K., Machovčák P., Kováč M., Socha L.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 4

2879--2886

EN

The main problem in the production of forgings from tool steels, especially thick plates, blocks, pulleys and rods which are used for special machine components for demanding applications, it is the inhomogeneous structure with segregations, cracks in segregations or complex type of non-metallic inclusions MnS and TiCN. These forgings are actually produced from conventional forging ingots. Due to the size of forgings, it would be interesting the production of these forgings from slab ingots. It is possible that the production of forgings from slab ingots (which are distinguished by a characteristic aspect ratio A/B), it would reduce the occurrence of segregations. The paper presents the verification of the production process of slab steel ingots in particular by means of numerical modelling using finite element method. The paper describes the pre-processing, processing and post-processing phases of numerical modelling. The attention was focused on the prediction of behavior of hot metal during the mold filling, on the verification of the final porosity, of the final segregation and on the prediction of risk of cracks depending on the actual geometry of the mold.

PL

Głównym problemem w produkcji odkuwek ze stali narzędziowych, szczególnie grubych płyt, bloków, kół pasowych i prętów, używanych do specjalnych elementów maszyn dla żądanych zastosowań, jest niejednorodna struktura z segregacją, pęknięciami w segregacji lub złożonego typu niemetaliczne wtrącenia MnS i TiCN. Te odkuwki są rzeczywiście produkowane z konwencjonalnych wlewków przeznaczonych do kucia. Ze względu na wielkość odkuwek, można by produkować te odkuwki z wlewków płaskich. Możliwe, że produkcja odkuwki z wlewków płaskich (które wyróżniają się charakterystycznym stosunkiem A/B), pozwoli zmniejszyć występowanie segregacji. W pracy przedstawiono weryfikację procesu produkcji wlewków płaskich za pomocą modelowania numerycznego z wykorzystaniem metody elementów skończonych. Artykuł opisuje fazy modelowania numerycznego: wstępną fazę przetwarzania, obróbkę i przetwarzanie końcowe. Zwrócono uwagę na zachowanie się ciekłego metalu podczas napełniania wlewnic, na weryfikację końcowej porowatości, końcowej segregacji i przewidywania ryzyka pęknięcia w zależności od rzeczywistej geometrii wlewnic.

11

Physical Modelling of the Steel Flow in RH Apparatus

Pieprzyca J., Merder T., Saternus M., Michalek K.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 3A

1859--1863

EN

he efficiency of vacuum steel degassing using RH methods depends on many factors. One of the most important are hydrodynamic processes occurring in the ladle and vacuum chamber. It is always hard and expensive to determine the flow character and the way of steel mixing in industrial unit; thus in this case, methods of physical modelling are applied. The article presents the results of research carried out on the water physical model of RH apparatus concerning the influence of the flux value of inert gas introduced through the suck legs on hydrodynamic conditions of the process. Results of the research have visualization character and are presented graphically as a RTD curves. The main aim of such research is to optimize the industrial vacuum steel degassing process by means of RH method.

PL

Skuteczność procesu próżniowego odgazowania stali metodą RH zależy od wielu czynników. Jednym z ważniejszych są procesy hydrodynamiczne zachodzące w kadzi stalowniczej i komorze próżniowej. Określenie sposobu przepływu i mieszania się stali w urządzeniu przemysłowym jest bardzo trudne i kosztowne. W związku z tym do tego celu wykorzystuje się m. in. metody modelowania fizycznego. W artykule przedstawiono rezultaty badań przeprowadzonych na wodnym modelu fizycznym urządzenia RH, dotyczące wpływu wartości strumienia gazu obojętnego wprowadzanego przez dysze króćca ssącego na warunki hydrodynamiczne procesu. Wyniki badań mają charakter wizualizacji oraz przedstawione zostały w postaci krzywych retencji RTD. Cel tego typu badań związany jest z optymalizacją przemysłowego procesu próżniowego odgazowania stali metodą RH.

12

Influence of Direct Thermal Analysis Experimental Conditions on Determination of the High Temperature Phase Transformation Temperatures

Gryc K., Strouhalová M., Smetana B., Socha L., Michalek K.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 4

2867--2872

EN

Thermo-physical and thermodynamic properties of metallic systems represent some of the most important data that allows to describe their behaviour under strictly specified conditions. These data are the basic, input data for simulative programs, which can model this behaviour and they can be applied to real conditions. Method of direct thermal analysis is the one of the methods of enabling to obtain such data. This paper deals with application of this method on particular sample of pure standard material. The experimental laboratory system for thermal analysis Netzsch STA 449 F3 Jupiter was used for experimental measurements. This paper is studying the influence of experimental conditions on the obtained temperature of phase transformations and on shift of phase transformation temperatures with respect to the monitored experimental conditions, accuracy and credibility of the measured data. Acquired values of this data could be significantly influenced by experimental conditions, size (mass) of samples, purity of inert atmosphere and also by regimes of controlled heating and cooling rates.

PL

Właściwości fizyczne i termodynamiczne układów metalicznych stanowią jedne z najważniejszych danych, które pozwalają opisać ich zachowanie w ściśle określonych warunkach. Dane te są podstawowymi danymi wejściowymi dla programu, który może symulować model tych zachowań i które mogą być zastosowane do rzeczywistych warunków. Metoda prostej (bezpośredniej) analizy termicznej jest jedną z metod pozwalających na uzyskanie takich danych. Niniejszy artykuł dotyczy zastosowania tej metody, w szczególności próbki czystego materiału standardowego. Do pomiarów eksperymentalnych było używane urządzenie dla analizy termicznej Netzsch STA 449 F3 Jupiter. W artykule analizowano wpływ warunków doświadczalnych na uzyskane temperatury przemian fazowych oraz na zmiany temperatur przemian fazowych z uwzględnieniem monitorowanych warunków doświadczalnych, dokładności i wiarygodności danych pomiarowych. Warunki doświadczalne, wielkości (masa) próbek, czystość atmosfery obojętnej, a przedziały kontrolowanej szybkości ogrzewania i chłodzenia mogą w znaczący sposób wpływać na otrzymane wartości tych danych.

13

Evaluation of Influence of Briquetted Synthetic Slags on Slag Regime and Process of Steel Desulphurization

Socha L., Michalek K., Bažan J., Gryc K., Machovčák P., Opler A., Styrnal P.

Archives of Metallurgy and Materials

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2014

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Vol. 59, iss. 2

809--813

EN

This paper presents the industrial results of evaluation of efficiency of synthetic slags during the treatment of steel at the equipment of the secondary metallurgy under conditions of the steel plant VÍTKOVICE HEAVY MACHINERY a.s. The aim of the heats was to assess the influence of the briquetted and sintered synthetic slags based on AI2O3 aiming the course of the steel desulphurization and slag regime during the production and treatment of steel grade 42CrMo4 with the technology EAF→LF→ VD. Within the plant experiments, basic parameters influencing the steel desulphurization and slag regime were monitored: desulphurization degree, basicity, content of easily reducible oxides, proportion of CaO/AI2O3 and Mannesmann’s index. Obtained results allowed to compare the steel desulphurization and to evaluate the slag regime. It was proved that the synthetic slag presenting the briquetted mixture of secondary corundum raw materials can adequately replace the synthetic slag created from the sintered mixture of natural raw materials.

PL

W pracy tej przedstawiono przemysłowe wyniki oceny efektywności zastosowania żużli syntetycznych podczas obróbki pozapiecowej stali w zakładzie VÍTKOVlCE HEAVY MACHINERY a.s. Celem badań był a ocena wpływu brykietówanych i spiekanych żużli syntetycznych opartych na AI2O3 - na przebieg odsiarczania stali i żużla podczas produkcji i obróbki stali 42CrMo4. zgodnie z technologią EAF → LF → VD. Podczas eksperymentów w zakładzie, monitorowano podstawowe parametry wpływające na odsiarczania stali i żużla: stopień odsiarczania, zasadowość, zawartość tlenków łatwo redukowałnych, stosunek CaO/AI2O3 oraz indeks Mannesniann’a. Uzyskane wyniki pozwoliły na porównanie stopnia odsiarczania stali w kontekście zastosowanych żużli. Wykazano, że syntetyczny żużel składający się z brykietowanej mieszaniny wtórnego korundu, może zastąpić syntetyczny żużel otrzymywany ze spieku mieszaniny surowców naturalnych.

14

The effect of boundary conditions of casting on the size of porosity of heavy steel ingot

Tkadlečková M., Michalek K., Gryc K., Smetana B., Machovčák P., Socha L.

Journal of Achievements in Materials and Manufacturing Engineering

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2013

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Vol. 56, nr 1

29--37

EN

Purpose: The paper presents new knowledge from numerical modelling of porosity in heavy steel ingot using ProCAST software. The main aim of numerical modelling realized under the conditions of the Department of Metallurgy and Foundry and Regional Materials Science and Technology Centre at the VSB-TU Ostrava is the optimization of the production of heavy steel ingots produced at the companyVítkovice Heavy Machinery a.s. Design/methodology/approach: The selected method of numerical modelling enables 3D fully dimensional numerical simulation of steel casting and the subsequent solidification of steel with the possibility of prediction of ingot defects. Findings: The numerical modelling of casting and solidification of the 90 ton heavy steel ingot under different boundary conditions of the casting led to these main conclusions: In all simulated variants, the final character of solidification was very similar. The lowest level of porosities were achieved in the variant when we used the longer filling time together with decrease of casting temperatures. However, the tested adjustment of casting technology appeared to have only small impact on the resulting porosity. Practical implications: The change of geometry of the mould will have probably more effect on the character of the solidification than only the small changes of the casting parameters which are dependent on the steel grade. Originality/value: On the basis of applied research in close collaboration with industry companies, the obtained data can contribute significantly to optimization the operating conditions, thereby increasing the efficiency of the steelmaking technology and final quality of cast steel.

15

Numerical modelling of macrosegregation in heavy steel ingot

Tkadlečková M., Machovčák P., Gryc K., Michalek K., Klus P.

Archives of Metallurgy and Materials

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2013

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Vol. 58, iss. 1

171-177

EN

The paper presents new knowledge and experience from numerical modelling of macrosegregation in heavy steel ingot using ProCAST software. The main aim of numerical modelling realized under the conditions of the Department of Metallurgy and Foundry and Regional Materials Science and Technology Centre at VSB-TU Ostrava is the optimization of the production of heavy steel ingots produced in V´ITKOVICE HEAVY MACHINERY a.s. Input parameters of computation were determined by the real conditions of parallel experimental casting of a 90-ton steel ingot. The input data were also verified by thermal analysis and thermography measurement. The numerical results of macrosegregation were compared with the chemical analysis evaluated in a real ingot section. According to the comparison, attention will be focused next on determination of the effect of boundary conditions of filling and solidification of the ingot on the size of macrosegregation.

PL

W artykule przedstawiono doswiadczenia i nowe informacje uzyskane o procesie makrosegregacji w wielkogabarytowym wlewku stalowym przy pomocy modelowania numerycznego z uzyciem oprogramowania ProCast. Głównym celem badan o charakterze modelowania numerycznego prowadzonych na Wydziale Metalurgii i Odlewnictwa oraz w Regionalnym Centrum Technologii i Inzynierii Materiałowej VSB-TU Ostrava jest optymalizacja produkcji wielkogabarytowych wlewków stalowych produkowanych w VITKOVICE HEAVY MACHINERY a.s. Dane wejsciowe do obliczen zostały wyznaczone w oparciu o opracowana analize rzeczywistych warunków odlewania stacjonarnego 90-tonowego wlewka stalowego. Zostały one dodatkowo zweryfikowane poprzez analize termiczna i pomiary termograficzne. Wyniki obliczen numerycznych porównano z wynikami analizy chemicznej przeprowadzonej dla wlewka rzeczywistego. Uzyskane rezultaty upowazniaja do podjecia w dalszej czesci badan problematyki dotyczacej okreslenia wpływu warunków brzegowych napełniania wlewnicy i krzepniecia wlewka na wielkosc procesu makrosegregacji.

16

Influence of submerged entry nozzle on intermixed zone in round blooms with a diameter of 525 mm

Michalek K., Gryc K., Tkadlečková M., Morávka J., Huczala T., Bocek D., Horáková D.

Archives of Metallurgy and Materials

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2013

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Vol. 58, iss. 1

187-191

EN

This work compares the experimental results of nickel concentration measurements in the intermixed zone of the continuously cast round blooms with a diameter of 525 mm using two types of submerged entry nozzles (SEN) - a straight-through nozzle and one with 5-ports. Based on determination of the system and optical interface in the blooms a detailed study of concentration profiles on the bloom surface in a small radius area, on the right side and then also on a cross-section of the blooms, was carried out. The results were further analysed using approximation models, and were to be used to verify the proposed model for predicting intermixed zones for a continuous casting machine, developed based on the results of physical and numerical modelling.

PL

Praca przedstawia porównanie wyników pomiarów doświadczalnych stężenia niklu we wlewkach okrągłych o średnicy 525 mm odlewanych metodą COS z strefa przejściową, przy użyciu dwóch typów wylewów zanurzanych typu SEN - wylewu osiowego oraz promieniowego 5-strumieniowego. Pomiary wykonano na powierzchni wlewków oraz na ich przekroju poprzecznym przy użyciu metod optycznych. Analizę uzyskanych wyników pomiarów przeprowadzono wykorzystując modele aproksymujace. Uzyskane w ten sposób rezultaty wykorzystano do modernizacji opracowanego wcześniej w oparciu o rezultaty badan o charakterze modelowania fizycznego i numerycznego modelu do prognozowania wielkości strefy przejściowej dla badanego urządzenia do ciągłego odlewania stali.

17

Evaluation of the chemical composition and microcleanliness of the steel samples from the heavy forging ingot

Michalek K., Tkadlečková M., Gryc K., Machovčák P.

Archives of Metallurgy and Materials

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2013

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Vol. 58, iss. 4

1161--1167

EN

The paper presents new results obtained from the evaluation of the chemical composition, microcleanliness and structure of the 90-ton heavy ingot cast in two successive heats, in which the content of Cu and Ni was intentionally modified in order to assess the degree of mutual mixing of the two heats in the ingot volume during the steel casting and solidification. For determination of chemical composition, spectral analysis and LECO were used. Microcleanliness evaluation was carried out on a Hitachi microanalytical complex equipped with the energy-dispersive spectrometer Vantage. To assess the composition of oxide non-metallic inclusions ternary diagrams were used. Structure of the basic steel matrix was induced by etching. The evaluation showed that in the casting of two successive heats, a certain degree of inhomogeneity of chemical composition, especially in the lower part of the ingot can be assumed in case of different composition. A greater segregation of sulphur in the central top part of the ingot was also detected. However, microcleanliness of the entire ingot is in general very good with low proportions of non-metallic inclusions.

PL

W pracy tej przedstawiono, wyniki uzyskane z oceny składu chemicznego, czystości w skali mikro i struktury 90 tonowych wlewków odlanych w dwóch kolejnych sekwencjach, w których zawartości Cu i Ni celowo zmieniono, dla oceny stopnia wzajemnego mieszania się dwóch wytopów w objętości wlewka podczas odlewania i krzepnięcia stali. Dla określenia składu chemicznego zastosowano analizę spektralną i LECO. Badania mikroczystości przeprowadzono na zespole urządzeń do mikroanalizy Hitachi wyposażonym w spektrometr energii rozproszonej Vantage. Dla oceny składu tlenkowych wtrąceń niemetalicznych użyto trójskładnikowych układów równowagi. Struktura podstawowej osnowy stali została ujawniona za pomocą trawienia. Ocena wykazała, iż przy odlewaniu dwóch kolejnych odlewów, można zakładać pewien stopień niejednorodności składu chemicznego, zwłaszcza w dolnej części wlewka, zwłaszcza przy różnych składach chemicznych. Stwierdzono również większą segregację siarki w centralnej części wlewka Jednakże, mikroczystość całego wlewka jest na ogół bardzo dobra, przy niskich proporcjach wtrąceń niemetalicznych.

18

Study of Fe-C-based alloys by dynamic methods of thermal analysis

Gryc K., Smetana B., Žaludová M, Tkadlečková M., Michalek K., Socha L., Klus P., Dobrovská J., Machovčák P.

Journal of Achievements in Materials and Manufacturing Engineering

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2012

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Vol. 55, nr 2

694--699

EN

Purpose: of this paper is to determine the temperatures of liquidus/solidus temperatures for multicomponent Fe-C-based alloys (industrially produced steel grades). The obtained results could be used in settings of conditions of steel casting and/or in the numerical simulations of processes occurring during casting and solidification of steel. Design/methodology/approach: Two modern apparatus for dynamic thermal analysis were used. Measurements of liquidus/solidus temperatures were realized by two thermal analysis methods. Experiments by the differential scanning calorimetry were done using the new one Setaram Multi High Temperature Calorimeter with 3D sensor (smaller samples about 2.6 g). The direct thermal analysis was used for large samples (23 g) at the STA 449 F3 Jupiter equipment. Findings: The differences between calculated and experimentally obtained values of liquidus/solidus temperatures were found. Also temperatures of solidification process are different than for “equilibrium” conditions. Practical implications: Presented results will be implemented into steel production practice - lowering of superheating of steel during ingot casting. The obtained temperatures will be implemented also into numerical simulations of ingot solidification. Originality/value: Two thermal analysis methods with different sample mass of steel was used under conditions of one research team. The direct cooperation between steel plant experts and university research team was applied. The utilization of results is the next phases of cooperated research of the authors.

19

Modelling steel’s homogenization during argon purging

Pieprzyca J., Kudliński Z., Michalek K., Gryc K., Tkadlečková M.

Journal of Achievements in Materials and Manufacturing Engineering

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2012

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Vol. 55, nr 2

573--577

EN

Purpose: One of the primary tasks that put the steel producers to the test is to reduce production costs while maintaining high quality. This objective is achieved among others through the optimization of conducted technological processes. Commonly used technology of steel homogenization with inert gases is an important stage in the production of steel in which that objective can be accomplished. Design/methodology/approach: Tests of hydrodynamic processes occurring during the steel blowing with inert gases process directly in industrial conditions is very difficult or impossible. Therefore, as the primary research method physical modelling was used. In order to carry out the tests described in the article a physical model of the station for the argon purging was used that is working at the VSB-TU, Department of Metallurgy and Foundry in Ostrava. Findings: As a result the study provided values for the investigated process and determined the appropriate location of the gas-permeable fittings in steelmaking ladle’s bottom plug. This allows to obtain the required conditions for the steel mixing in the entire volume of ladle’s workspace. Research limitations/implications: Tests presented in the article were carried out in the VSB-TU in Ostrava. Due to this fact some research limitations occurs that applies to localization and physical model’s specific construction. Therefore, as a result of cooperation between VSB-TU in Ostrava and the Silesian University of Technology will be carried out the construction of the new research station in Katowice. Practical implications: The results of the research constitute the basis to make changes that will allow the optimization to so far used purge of steel technology. Originality/value: The results presented in the article are addressed to the steel producers and it allows to optimize on-going steel homogenization process that takes place in the ladle.

20

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.