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V průběhu odlévání odlitků z tvárné litiny mohou vznikat podmínky příznivé pro vznik vnitřních vad v odlitcích. Přítomnost těchto vad může být pro daný odlitek fatální a společně s dalšími okolnostmi vést k jeho likvidaci. Proto je potřeba odhalit přítomnost vad, pokud možno ještě ve fázi návrhu odlitku. K tomuto účelu lze využít numerické simulace, které jsou v dnešní době běžně používaným nástrojem k predikci vad. Tato práce popisuje proceduru numerického modelování odlévání a tuhnutí odlitku z tvárné litiny, určeného pro energetický průmysl. Cílem numerických simulací byla predikce odlévání, tuhnutí a napěťových stavů s cílem ověřit adekvátnost navržené technologie výroby. Numerické simulace odhalily mírné nedostatky v technologii výroby, jež by mohly při neočekávané změně procesních podmínek vest ke vzniku vad. Tyto nedostatky se týkaly zejména vtokové soustavy, nálitkování odliku a náchylnosti ke vzniku trhlin. Na základě simulací byla navržena opatření pro eliminaci rizik spojených se vznikem diskutovaných vad, jež budou zakomponována do technologie výroby. PING Junior 2021 is organized with the support of funds for specific university research project SVK1-2021-008 and ERDF "Research of additive technologies for future applications in the machinery industry - RTI plus" (No. CZ.02.1.01/0.0/0.0/18_069/0010040).

V rámci výzkumu byly provedeny numerické simulace ve výpočetním SW MAGMASOFT, zaměřené na optimalizaci odlévání a tuhnutí daného typu odlitku, určeného pro lodní průmysl. Tento článek prezentuje výsledky numerických simulací společně s návrhem změn v technologii výroby, vedoucích ke zvýšení kvality odlitku. Z výsledků simulací nebyly zjištěny závažné nedostatky navržené technologie. Z hlediska optimalizace plnění však byla doporučena úprava tvaru zářezů pro zamezení rozstřiku kovu. Pro dosažení struktury bez vnitřních vad se doporučuje optimalizace nálitkování odlitku a mírná úprava tvaru pro eliminaci rizika tvorby porezity a prasklin. PING Junior 2021 is organized with the support of funds for specific university research project SVK1-2021-008 and ERDF "Research of additive technologies for future applications in the machinery industry - RTI plus" (No. CZ.02.1.01/0.0/0.0/18_069/0010040).

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. Web of Science 63 2 992 987

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. 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. Web of Science 60 4 2871 2867

The knowledge of the solidus and liquidus temperatures of the real-steel grades is one of the most important technological factors - especially when dealing with the processes of casting and solidification. These temperatures are critical parameters for proper settings of the models (physical or numerical) or in the final stage of an applied research of a real process. A correct setting of a production technology is significantly affecting the final quality of the as-cast steel (billets or ingots). Therefore, this paper is devoted to discussing the findings obtained during a utilization of dynamicthermal-analysis methods to identify the solidus and liquidus temperatures applicable to commercially produced steels. The results obtained with a differential thermal analysis (DTA) for three steel grades and with 3D differential scanning calorimetry (3D DSC) for two steel grades are compared with the results of the selected equations commonly used for liquidus and/or solidus temperature calculations. The calculations obtained with the Computherm SW for the discussed steels were also realized. It can be stated that the equilibrium liquidus and solidus temperatures obtained with the above-mentioned methods for each steel grade differ. The differences between the calculated results, the thermodynamic calculations and thermal-analysis results are very unpredictable and vary individually for different steels. These differences are not marginal (tens of Celsius degrees). So, it is sometimes suitable to combine several methods for a proper determination of the liquidus and solidus temperatures for a correct setting of a steel-making process or its modelling. The best solution for a technological process is to obtain the liquidus and solidus temperatures for a concrete-steel grade from agiven steelmaking practice - a thermal analysis of a concrete-steel grade is a possible way. Poznavanje solidusnih in likvidusnih temperatur realnih jekel je med najpomembnejšimi tehnološkimi dejavniki - še posebno pri obravnavi procesov med ulivanjem in strjevanjem. Te temperature so kritični parametri za pravilno postavitev modela (fizikalnega ali numeričnega) ali pri končni stopnji raziskav realnega procesa. Pravilna postavitev proizvodne tehnologije pomembno vpliva na končno kvaliteto ulitega jekla (gredic in ingotov). Zato je ta članek namenjen razpravi o ugotovitvah, dobljenih med uporabo metod dinamične termične analize za ugotavljanje solidusne in likvidusne temperature pri komercialno proizvedenih jeklih. Rezultati, dobljeni z diferenčno termično analizo (DTA) za 3 jekla in s 3D diferenčno vrstično kalorimetrijo (3D DSC) za 2 vrsti jekel, so bili primerjani z rezultati iz izbranih enačb, ki se navadno uporabljajo za izračun temperature solidusa in likvidusa. Za obravnavana jekla so bili tudi izdelani izračuni s Computherm SW. Ugotovljeno je bilo, da se ravnotežne likvidusne in solidusne temperature, dobljene z omenjenimi metodami, razlikujejo. Razlike med izračunanimi rezultati, termodinamičnimi izračuni in rezultati termične analize so nepredvidljivi in se različno spreminjajo pri različnih jeklih. Te razlike niso nepomembne (desetine stopinj Celzija). Zato je včasih pomembno kombinirati več metod za pravilno določitev likvidusne in solidusne temperature pri procesu proizvodnje jekla ali njegovem modeliranju. Najboljša rešitev za tehnološki proces je ugotavljanje likvidusne in solidusne temperature pri konkretnem jeklu iz dane jeklarske prakse - mogoča pot pa je tudi s termično analizo konkretnega jekla.

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. Web of Science 58 1 177 171

The paper presents new knowledge about physical and numerical modelling of a non-stationary steel flow into a mould through a subentry shroud with an inner, pressed metering nozzle. The physical and numerical modelling was realized under the conditions of the Department of Metallurgy and Foundry at VSB-Technical University of Ostrava. A special type of the subentry shroud is used during continuous casting of steel in Třinecké železárny, a.s. During continuous casting of steel, two unfavourable phenomena were observed. In the first case, it was not possible to increase the casting speed, though the diameter of the metering nozzle was extended. In the second case, a fluctuation of the casting speed among individual casting strands was detected. These two problems did not allow an improvement of the performance of the casting machine. Therefore, the physical and numerical modelling was performed. Attention was focused on the verification of the effect of the inner diameter of the nozzle body and internal diameter of the metering nozzleon the resulting volume flow rates. Four diameters of the metering nozzle - (16; 17; 17.5; 18) mm - were tested. The physical modelling was done on a 1 : 1 model constructed from Plexiglas. The numerical modelling was realized in the ANSYS FLUENT software. On the basis of the results of the modelling study and in cooperation with the VESUVIUS company, a new type of the profile of the subentry shroud with a metering nozzle was designed. The first experimental results in the steel plant led to an increase in the productivity of the continuous-casting machine. Članek predstavlja novo znanje o fizikalnem in numeričnem modeliranju nestacionarnega toka jekla v kokilo skozi potopljen izlivek z notranjo šobo. Fizikalno in numerično modeliranje je bilo izvršeno v Oddelku za metalurgijo in livarstvo na VSB Tehniški univerzi, Ostrava. V Třinecké železárny, a. s., se uporabljajo posebne izvedbe potopljenih izlivkov med kontinuirnim ulivanjem jekla. Pri tem sta bila opažena dva neželena pojava. Pri prvem ni bilo mogoče povečati hitrosti litja, čeprav je bil povečan premer notranjega izlivka, pri drugem pa je bilo opaženo spreminjanje hitrosti litja med posameznimi žilami. Ta dva pojava nista omogočila izboljšanja zmogljivosti livne naprave. Zato je bilo izvršeno fizikalno in numerično modeliranje. Pozornost je bila usmerjena na preverjanje vpliva notranjega premera telesa izlivka in notranjega premera izlivne šobe na stopnje pretoka. Preizkušeni so bili štirje premeri (16; 17; 17,5 in 18) mm notranjega izlivka. Fizikalni model je bil izdelan na modelu 1 : 1, izdelanem iz pleksi stekla. Numerični model je bil izdelan s programsko opremo ANSYS FLUENT. Na osnovi rezultatov in s sodelovanjem podjetja VESUVIUS je bila konstruirana nova vrsta potopnega izlivka z notranjo izlivno šobo. Prvi preizkusi v jeklarni so omogočili povečanje produktivnosti naprave za kontinuirno ulivanje.

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. Web of Science 58 1 191 187

The paper describes the knowledge about and results of the experimental heats performed in an electric steel plant. The aim was to verify the possibilities of a controlled desulphurization of alloy steel in a VOD (Vacuum Oxygen Decarburization) device, particularly when using chemical heating through the OVD process (Oxygen Vacuum Deoxidation/Degassing), as well as the standard slag formers. Experimental procedures were used in the production of alloy tool steel. Both, the system of making the reducing slag and optimizing the composition of individual oxides in order to achieve the desired basicity, are complicated by the products of the chemical heating. Therefore, it was necessary to develop a new production technology that would eliminate such oxide products of chemical heating and, thus, the maximum degree of desulphurization could be achieved. The main principle of the technology is to create appropriate thermodynamic and kinetic conditions required for desulphurization. In particular, this concerns a low oxygen activity in the steel, the composition of refining slag, and an intense bath stirring with argon. Članek opisuje znanje in rezultate raziskave eksperimentalnih talin, izdelanih v elektrojeklarni. Namen je bil preveriti možnost kontroliranega razžvepljanja legiranega jekla v VOD (Vacuum Oxygen Decarburization)-napravi, posebno med uporabo kemijskega ogrevanja med OVD (Oxygen Vacuum Deoxidation/Degassing)-postopkom, kot tudi standardnih gradnikov žlindre. Eksperimentalni postopki so bili uporabljeni pri proizvodnji legiranega orodnega jekla. Oboje, tvorba reduktivne žlindre in optimalna sestava posameznih vključkov, z namenom doseganja želene bazičnosti, ovirajo produkti kemijskega ogrevanja. Zato je bilo potrebno razviti novo tehnologijo proizvodnje, ki bi preprečila oksidne produkte kemijskega ogrevanja, kar bi omogočilo doseganje maksimalne stopnje razžvepljanja. Osnovni princip nove tehnologije je zagotoviti ustrezne termodinamične in kinetične pogoje, potrebne za razžvepljanje. To pomeni nizko aktivnost kisika v jeklu, sestavo rafinacijske žlindre in intenzivno mešanje kopeli z argonom.

The article deals with the results of the experimental heats performed in the electric steel plant of TŘINECKÉ ŽELEZÁRNY, a. s. (TŽ, a. s.). The aim was to verify the possibility of deep desulphurization of steel in the basic 10-t electric arc furnace. Experimental procedures making use of the industrially produced synthetic slag were applied in the production of the high-alloy chrome steels and the middle-alloy tool steels, where the desulphurization, interms of thermodynamics, is a more demanding process than the chrome-nickel steel desulphurization. With the use of the technological processes it is possible to achieve low contents of sulphur in steel, below mass fraction 0.003 %. Achieving these contents depends on a suitable slag basicity, and, inparticular, on the ratio of CaO/Al2O3. Based on the analysis of the results, a critical factor significantly affecting the final content of the sulphur and thus the efficiency of the desulphurization of steel, the content of FeO in the reduction slag, is carefully considered. A higher MgO content in slag (up to w = 25 %) had no significant influence on the results of the steel desulphurization. Članek predstavlja rezultate eksperimentalnih talin, izdelanih v TŘINECKÉ ŽELEZÁRNY, a. s. (TŽ, a. s.). Namen raziskav je bil preveriti možnost močnega razžvepljanja jekla v bazični 10-tonski elektropeči. Izvršena je bila raziskava z uporabo industrijsko proizvedene sintetične žlindre pri proizvodnji močno legiranega kromovega jekla in srednje legiranega orodnega jekla, pri katerih je termodinamika razžvepljanja bolj zapletena kot pri razžvepljanju krom-nikljevih jekel. S primernimi tehnološkimi ukrepi je mogoče doseči v jeklu majhno vsebnost žvepla, nižjo od masnega deleža 0,003 %. Doseganje teh vsebnosti je odvisno od primerne bazičnosti žlindre in posebno še od razmerja CaO/Al2O3. Na osnovi analize rezultatov je bil določen kritični faktor, vsebnost FeO v redukcijski žlindri, ki močno vpliva na končno vsebnost žvepla in s tem na učinkovitost razžvepljanja. Večja vsebnost MgO (do masnega deleža 25 %) v žlindri nima večjega vpliva na razžvepljanje jekla.

This work compares the experimental results of nickel-concentration measurements in the intermixed zone of the continuously cast round blooms witha diameter of 525 mm using two types of submerged entry nozzles (SEN) - a straight-through nozzle and the one with 5-ports. Based on the determination of the system and optical interface in a bloom, a detailed study of the concentration profiles on the bloom surface in a small-radius area, on the right-hand side, and then also on the cross sections of the blooms was carried out. The results were further analysed using the approximation models, and were used to verify the proposed model predicting the intermixed zones for the continuous-casting machines. The developed model was based on the results of the physical and numerical modelling. V tem delu so predstavljeni eksperimentalni rezultati merjenja koncentracije niklja v območju mešanja kontinuirno ulitih okroglih blokov s premerom 525 mm pri uporabi dveh vrst potopljenih šob (SEN) - gladke ravne šobe in šobe s 5 odprtinami. Opravljen je bil podrobnejši študij profila koncentracije na površini bloka na področje majhnega premera, na ravnem delu in tudi na prečnem prerezu bloka. Rezultati so bili analizirani z uporabo modelov približka in uporabljeni za napovedovanje območja mešanja pri napravah za kontinuirno ulivanje. Razviti model temelji na rezultatih fizikalnega in numeričnega modeliranja.

The paper is devoted to new experiences with the setting of a numerical simulation of filling and solidification of a 90-ton steel ingot in the ProCAST simulation programme. The aim of the numerical modelling realized under the conditions of the Department of Metallurgy and Regional Materials Science and Technology Centre (RMSTC) at VSB-TU Ostrava is the verification and optimization of the production technology for the heavy-steel ingots produced in VÍTKOVICE HEAVY MACHINERY a.s. The input parameters of the computation were determined with the real conditions of casting a 90-ton steel ingot. The ingot geometry was created in the CAD system SolidWorks. Before the computational grid generation of finite elements in the Visual-Meshmodule, the geometry was subjected to an analysis of the topology. The material properties of the individual components of the ingot-casting system were defined with the Computherm calculating module selecting the materials from its own database of ProCast. In addition, the thermodynamic properties were determined by using the datasheets of the refractory materials of the manufacturer, and finally checked with the equations generally used to determine liquidus and solidus temperatures, density and enthalpy, etc. The boundary conditions and the heat transfer were also defined. In parallel with the numerical simulation, the operational experimental casting of a 90-ton ingot was carried out. To obtain more complete information about the temperature fields of the ingot-casting system and of the data about the values of the heat flow, the process of filling and solidification was monitored by using thermal imaging cameras. The conclusion summarizes the main knowledge obtained on the basis of the primary results of the computation and gives a guideline for further research. Članek obravnava nove izkušnje z numerično simulacijo polnjenja in strjevanja 90-tonskega jeklenega ingota s ProCAST-programom za simulacijo. Namen izvršenega numeričnega modeliranja v Department of Metallurgy in Regional Materials Science and Technology Centre (RMSTC) na VSB-TU Ostrava je preverjanje in optimiranje proizvodne tehnologije težkih jeklenih ingotov, proizvedenih v Vítkovice Heavy Machinery, a. s. Vhodni parametri za izračun sobili določeni v realnih razmerah pri ulivanju 90-tonskega jeklenega ingota. Geometrija ingota je bila postavljena v CAD-sistemu SolidWorks. Pred postavitvijo mreže končnih elementov z Visual-Mesh-modulom je bila geometrija obdelana s topološko analizo. Lastnosti materiala posameznih komponent livnega sistema ingota so bile določene z računskim modulom Computherm in z izbiro materiala iz datoteke ProCast. Termodinamske lastnosti so bile določene z uporabo datotek proizvajalcev ognjevzdržnih materialov ter končno preverjene z izračunom po enačbah, ki se uporabljajo za določanje temperature likvidusa in solidusa, gostote, entalpije itd. Določeni so bili robni pogoji in prenos toplote. Vzporedno z numerično simulacijo je bilo izvršeno eksperimentalno ulivanje 90-tonskega ingota. Da bi dobili bolj popolno informacijo o temperaturnih poljih ulivnega sistema ingota in podatke o vrednostih toplotnega toka, je bil postopek polnjenja in strjevanja posnet tudi s termovizijsko kamero. Sklepi povzemajo glavne ugotovitve primarnih rezultatov izračunov in dajejo napotke za nadaljnje raziskave.

The paper is devoted to selected aspects of the current issues of the high-temperature interaction of the synthetic multicomponent oxidic systems and selected grades of steel. Analysing the consequences of the interaction between slag and molten steel is an integral part of modern research that can be connected with subsequent, applied research in the field of producing and refining steel. The interactions between the synthetic slag and the molten metal is realized after the processing of the liquid steel in the primary metallurgical aggregates, i.e., at the beginning of refining processes of secondary metallurgy. The addition of these synthetic systems (slag) significantly affects many technological processes and indirectly affects the final quality of the cast steel. This influence can be seen on two levels: the metallurgical and the metallographic. Both of these levels of evaluation complement each other. For the evaluation of the metallurgical aspects of refining processes a number of thermodynamic relations were used, supplemented by empirically established formulas and coefficients. Metallographic analyses utilize modern tools in the study of the structure and the chemical composition of materials, i.e., from light microscopy to sophisticated systems of microanalysis of elemental composition using a scanning electron microscope combined with an energy-dispersive X-ray micro-analyser. It is obvious that this area deserves more focused research and more attention, particularly in the context of the on-going needs for the identification and quantification of phenomena taking place in the following metallurgical innovations. Članek obravnava izbrane vidike aktualnih vprašanj o visokotemperaturni interakciji sintetičnih večkomponentnih oksidnih sistemov v izbranih vrstah jekel. Analiziranje posledic interakcije med žlindro in talino je sestavni del potekajočih raziskav in se lahko poveže z uporabnimi raziskavami na področju proizvodnje in rafinacije jekla. Do interakcije med sintetično žlindro in staljeno kovino pride po izdelavi taline jekla v primarni metalurški peči, na začetku postopka rafinacije v sekundarni metalurgiji. Dodatek sintetične žlindre močno vpliva na številne tehnološke procese in neposredno vpliva na končno kvaliteto ulitega jekla. Ta učinek se kaže na dveh nivojih: na metalurškem in metalografskem. Oba nivoja ocene sta med seboj komplementarna. Za oceno metalurških vidikov postopka rafinacije je bilo uporabljeno več termodinamskih odvisnosti, dopolnjenih z empirično določenimi enačbami in koeficienti. Metalografska analiza uporablja sodobna orodja za študij strukture in kemijske sestave materiala - od svetlobne mikroskopije do zapletenih sistemov mikroanalize, elementne sestave z uporabo vrstičnega elektronskega mikroskopa v kombinaciji z energijsko disperzijsko rentgensko spektroskopijo. Očitno to področje zahteva bolj usmerjene raziskave in večjo pozornost, posebno v kontekstu zahtev, identifikacije in kvantifikacije pojavov, ki so posledica metalurških inovacij.

This paper presents the experience obtained from plant experiments specialized in the usage of three types of fluxing agents for slags based on Alsub{2}Osub3. Proper experiments took place during the steel treatment by secondary metallurgy. The objective of the plant experiments was to assess the degree of steel desulphurization and its course. An assessment of the steel desulphurization with the help of basic parameters, such as the degree of desulphurization, the basicity, the content of easily reducible oxides, the proportion of CaO/Alsub{2}Osub3 and Mannesmann's index was made. At the same time the behaviour of the fluxing agents and the development of their dissolution in steelmaking slags were assessed. Članek prikazuje izkušnje, dobljene s preizkusi v železarni, z uporabo treh vrst talil za tvorbo žlindre na osnovi Alspodaj{2}Ospodaj3. Primerni preizkusi so bili izvršeni med obdelavo jekla s sekundarno metalurgijo. Cilj preizkusov v železarni je bil določiti stopnjo razžvepljanja in njegov potek. Z osnovnimi parametri, kot so bazičnost, vsebnost lahko reducirnih oksidov, delež CaO/Alspodaj{2}Ospodaj3 in Mannesmannov indeks, je bilo ocenjeno razžvepljanje jekla. Istočasno je bilo ugotovljeno vedenje talil in nastanek njihovih raztopin v jeklarski žlindri.