Wyniki wyszukiwania - BazTech

1

Physical and numerical simulation of the production chain of fasteners manufactured of 32CrB4 steel control-cooled in the stelmor process to develop the multiphase microstructure

Piwowarczyk Michał, Wolańska Natalia, Wilkus Marek, Pietrzyk Maciej, Rauch Łukasz, Kuziak Roman, Pidvysots’kyy Valeriy, Radwański Krzysztof

Computer Methods in Materials Science

|

2023

|

Vol. 23, No. 2

5--16

EN

The development of the concept of Thermomechanical Controlled Processing (TMCP) in the wire rod rolling mill of CMC Poland has opened up new opportunities for the production of fasteners without the application of heat treatment. The crucial effect of TMCP in the case of wire rod rolling is its capability of shaping fine austenite grain size following the last pass, typically below 20–25 µm in the wire rod cross-section. This is a prerequisite for obtaining the required cold workability level for the cold forming of fasteners, even if hard constituents (bainite, martensite) are present in the wire rod structure. In this paper, the physical simulation and numerical modelling capabilities were described for the design of cooling conditions in the Stelmor process and cold heading operation. The investigated material was conventional 32CrB4 grade used for the fasteners production with the application of heat treatment.

2

Accounting for the random character of nucleation in the modelling of phase transformations in steels

Poloczek Łukasz, Kuziak Roman, Foryś Jakub, Szeliga Danuta, Pietrzyk Maciej

Computer Methods in Materials Science

|

2023

|

Vol. 23, No. 2

17--28

EN

In our earlier work, a stochastic model of multi-stage deformation at elevated temperatures was developed. The model was applied to calculate histograms of dislocation density and grain size at the onset of phase transformation. The histograms were used as input data for the simulation of phase transitions using the traditional deterministic model. Following this approach, microstructural inhomogeneity was predicted for different cooling conditions. The results obtained, showing the effect of dislocation density and inhomogeneity of austenite grain size on the microstructural inhomogeneity of the final product, can be considered reliable as they are based on material models determined in previous publications and validated experimentally. The aim of the present work was to extend the model by taking into account the stochastic nature of nucleation during phase transitions. The analysis of existing stochastic models of nucleation was performed, and a model for ferritic transformation in steels was proposed. Simulations for constant cooling rates as well as for industrial cooling processes of steel rods were performed. In the latter case, uncertainties in defining the boundary conditions and segregation of elements were also considered. The reduction of the computing costs is an important advantage of the model, which is much faster when compared to full field models with explicit microstructure representation.

3

Thermal-mechanical finite element simulation of flat bar rolling coupled with a stochastic model of microstructure evolution

Szeliga Danuta, Czyżewska Natalia, Kusiak Jan, Kuziak Roman, Morkisz Paweł, Oprocha Piotr, Pietrzyk Maciej, Piwowarczyk Michał, Poloczek Łukasz, Przybyłowicz Paweł, Rauch Łukasz, Wolańska Natalia

Computer Methods in Materials Science

|

2022

|

Vol. 22, No. 3

137--148

EN

It is generally recognized that the kinetics of phase transformations during the cooling of steel products depends to a large extent on the state of the austenite after rolling. Austenite deformation (when recrystallization is not complete) and grain size have a strong influence on the nucleation and growth of low-temperature phases. Thus, the general objective of the present work was the formulation of a numerical model which simulates thermal, mechanical and microstructural phenomena during multipass hot rolling of flat bars. The simulation of flat bar rolling accounting for the evolution of a heterogeneous microstructure was the objective of the work. A conventional finite-element program was used to calculate the distribution of strains, stresses, and temperatures in the flat bar during rolling and during interpass times. The FE program was coupled with the stochastic model describing austenite microstructure evolution. In this model, the random character of the recrystallization was accounted for. Simulations supplied information about the distributions of the dislocation density and the grain size at various locations through the thickness of the bars.

4

Stochastic model describing evolution of microstructural parameters during hot rolling of steel plates and strips

Szeliga Danuta, Czyżewska Natalia, Klimczak Konrad, Kusiak Jan, Kuziak Roman, Morkisz Paweł, Oprocha Piotr, Pietrzyk Maciej, Poloczek Łukasz, Przybyłowicz Paweł

Archives of Civil and Mechanical Engineering

|

2022

|

Vol. 22, no. 3

art. no. e139

EN

Enhancing strength-ductility synergy of materials has been for decades an objective of research on structural metallic materials. It has been shown by many researchers that significant improvement of this synergy can be obtained by tailoring heterogeneous multiphase microstructures. Since large gradients of properties in these microstructures cause a decrease of the local fracture resistance, the objective of research is to obtain smoother gradients of properties by control of the manufacturing process. Advanced material models are needed to design such microstructures with smooth gradients. These models should supply information about distributions of various microstructural features, instead of their average values. Models based on stochastic internal variables meet this requirement. Our objective was to account for the random character of the recrystallization and to transfer this randomness into equations describing the evolution of dislocations and grain size during hot deformation and during interpass times. The idea of this stochastic model is described in the paper. Experiments composed of uniaxial compression tests were performed to supply data for the identification and verification of the model in the hot deformation and static recrystallization parts. Histograms of the grain size were measured after hot deformation and at different times after the end of deformation. Identification and validation of the model were performed. The validated model, which predicts evolution of heterogeneous multiphase microstructure, is the main output of our work. The model was implemented in the finite element program for hot rolling of plates and sheets and simulations of these processes were performed. The model’s capability to compare and evaluate various rolling strategies are demonstrated in the paper.

5

Decomposition mechanisms of continuously cooled bainitic rail in the critical heat-affected zone of a flash-butt welded joints

Królicka Aleksandra, Żak Andrzej, Kuziak Roman, Radwański Krzysztof, Ambroziak Andrzej

Materials Science Poland

|

2021

|

Vol. 39, No. 4

615--625

EN

The joining process of bainitic rails is significant in terms of their industrialization in high-speed and heavy-loaded railways. This paper demonstrates the microstructure changes in the critical zone of the welded joint, which is responsible for the greatest deterioration in mechanical properties. Extensive progress in the decomposition of the retained austenite and bainitic ferrite occurs in the low-temperature heat-affected zone (LTHAZ) of the flash-butt welded joint of low-carbon bainitic rail. The decomposition products of the retained austenite were mainly a mixture of cementite and ferrite. The cementite was mainly precipitated at the boundary of the bainitic ferrite laths, which indicates lower thermal stability of the filmy austenite. Moreover, it was found that a part of the refined blocky retained austenite was decomposed into the ferrite and nanometric cementite, while another remained in the structure. The decomposition mechanisms are rather heterogeneous with varying degrees of decomposition. A relatively high proportion of dislocations and stress fields prove the occurrence of residual stresses formed during the welding process.

6

Study on the influence of sheet straightening process on residual stress distribution, mechanical properties and structure of deep-drawing steel sheets

Radwański Krzysztof, Adamiec Andrzej, Kuziak Roman, Zaława Dariusz, Sozańska-Jędrasik Liwia

Journal of Metallic Materials

|

2021

|

Vol. 73, no. 4

3--10

EN

The article describes the impact of the stretch levelling process of DC03 and DC04 steel sheets on their quality in terms of further application for products formed in technologies used in the automotive industry. The straightening process was carried out in a demonstration line developed as part of a project carried out by DAR STAL Dariusz Zaława together with the Łukasiewicz Research Network - Institute for Ferrous Metallurgy. The study examined the influence of stretch levelling on waviness and the state of internal stresses of the sheets. It was found that the use of stretch levelling with a controlled elongation value results in obtaining a favourable and stable state of stress in the sheets. No significant influence of the straightening process on the structure and mechanical properties of the sheets was found.

PL

W ramach artykułu opisano wpływ procesu prostowania naciągowego blach ze stali DC03 i DC04 na ich jakość pod kątem dalszego przeznaczenia na wyroby kształtowane w technologiach stosowanych w przemyśle motoryzacyjnym. Proces prostowania prowadzono w linii demonstracyjnej opracowanej w ramach projektu realizowanego przez firmę DAR STAL Dariusz Zaława wspólnie z Sieć Badawcza Łukasiewicz - Instytutem Metalurgii Żelaza. W ramach pracy badano wpływ prostowania naciągowego na falistość i stan naprężeń własnych blach. Stwierdzono, że zastosowanie prostowania naciągowego, z kontrolowaną wartością wydłużenia, powoduje uzyskanie korzystnego i stabilnego stanu naprężenia w blachach. Nie stwierdzono znaczącego wpływu procesu prostowania na strukturę oraz właściwości mechaniczne blach.

7

Method for heat treatment of the running surface of the head of the pearlitic steel rails

Kuziak Roman, Pidvysots’kyy Valeriy, Rauch Łukasz, Pietrzyk Maciej

Journal of Metallic Materials

|

2021

|

Vol. 73, no. 1

9--15

EN

The paper deals with the new approach to the optimization of the pearlitic rail’s head hardening process aimed at balancing the relation between strength and ductility of the head running surface. In the industrial process, efforts have been undertaken so far to maximize the hardness of the rail’s head while maintaining its pearlite structure, resulting in obtaining enhanced wear resistance and resistance to the contact fatigue defects initiation. The new approach, described in this paper, aims at designing the head hardening process enabling achievement of the high hardness of the running surface combined with high ductility expressed in terms of the total elongation. To achieve this aim of the investigation, a computer program was developed capable of predicting the occurrence of the phase transformations during rail head cooling and microstructure features after cooling. The program was linked with dedicated inverse module enabling the adjustment of the cooling conditions to achieve the required state of the pearlitic structure.

PL

W artykule przedstawiono nowe podejście do optymalizacji procesu obróbki cieplnej szyn perlitycznych, którego celem jest uzyskanie korzystnej relacji między twardością a ciągliwością warstwy tocznej główki szyn. Opracowane dotychczas technologie obróbki cieplnej szyn perlitycznych stawiały sobie za cel uzyskanie jak najwyższej twardości powierzchni tocznej główki, przy zachowaniu struktury perlitycznej tej powierzchni. Dzięki temu uzyskuje się znaczący wzrost odporności tej powierzchni na procesy zużycia i inicjowanie wad kontaktowo-zmęczeniowych. Zaproponowana metoda obróbki cieplnej umożliwia uzyskanie bardzo wysokiej twardości powierzchni tocznej, ale równocześnie, pozwala na uzyskanie wysokiej ciągliwości tej warstwy, wyrażonej poprzez wydłużenie do zerwania w statycznej próbie rozciągania. Warunki obróbki cieplnej, spełniającej powyższe założenia, opracowano stosując dedykowany program komputerowy, który symuluje przemiany fazowe w szynie, z możliwością przeprowadzenia optymalizacji procesu z zastosowaniem metody obliczeń odwrotnych.

8

Influence of heat treatment on thermo-mechanical fatigue and high temperature creep properties for 316L steel

Poloczek Łukasz, Kuziak Roman, Pidvysots’kyy Valeriy

Journal of Metallic Materials

|

2021

|

Vol. 73, no. 3

33--43

EN

The main purpose of the work was to develop the characteristics of high-temperature structure degradation processes under the synergistic effects of thermo-mechanical fatigue and high temperature creep for samples made of 316L steel in the delivery condition and after heat treatment. The use of heat treatment consisting of solution treatment at 1100°C for 45 minutes and water cooling improved the mechanical properties of 316L steel. Moreover, in fatigue tests, in every case, increasing the strain value in a single cycle leads to a faster sample rupture. An additional aim of the research was also to develop and verify a new innovative research methodology concerning the combination of fatigue cycles with the creep process at elevated temperature, the aim of which is to better reflect the behaviour of the material in real working conditions.

PL

Głównym celem pracy było opracowanie charakterystyk wysokotemperaturowych dla procesów degradacji struktury pod wpływem synergicznego oddziaływania zmęczenia cieplno-mechanicznego i pełzania w podwyższonej temperaturze dla próbek wykonanych ze stali 316L w stanie dostawy i po obróbce cieplnej. Zastosowanie obróbki cieplnej polegającej na przesyceniu w 1100°C przez 45 minut i chłodzeniu wodą poprawiło właściwości mechaniczne stali 316L. Ponadto w testach zmęczeniowych w każdym przypadku zwiększenie wartości odkształcenia w jednym cyklu prowadzi do szybszego rozerwania próbki. Dodatkowym celem badań było również opracowanie nowej, innowacyjnej metodyki badawczej dotyczącej połączenia cykli zmęczeniowych z procesem pełzania w podwyższonej temperaturze, której celem jest lepsze odzwierciedlenie zachowania materiału w rzeczywistych warunkach pracy.

9

Study of phase transformations in complex phase steel using a mesoscale cellular automaton model part 2: Experiments and validation

Opara Jarosław, Kuziak Roman

Journal of Metallic Materials

|

2020

|

Vol. 72, no. 3

32--44

EN

A two-dimensional mesoscale model based on the concept of hybrid cellular automata was used to study phase transformations in a complex phase steel during continuous cooling. This model enables simulation of the decomposition of austenite into ferrite, bainite, and martensite, accompanied by calculations of volume and grain boundary diffusion of carbon. In effect, as a result, one can observe the morphology of simulated microstructures, corresponding carbon segregation as well as microhardness distribution. These results with the kinetics of austenite to ferrite phase transformation and predicted values of the complex phase steel hardness are the subject of model validation. A series of dilatometric experiments were carried out with constant cooling rates in order to construct a CCT diagram and validate the presented model. The convergence of simulated results with empirical outcomes was confirmed quantitatively using a dedicated goal function and data summaries in the table and graphs. However, some qualitative and quantitative discrepancies in terms of microstructure morphology are indicated which was possible thanks to applying a wide range of different validation parameters of the model. It is emphasized how crucial is the use of appropriate validation methodology.

PL

Dwuwymiarowy mezoskalowy model oparty na koncepcji hybrydowych automatów komórkowych zastosowano do badania przemian fazowych w stali wielofazowej podczas ciągłego chłodzenia. Model ten umożliwia symulację rozpadu austenitu w ferryt, bainit i martenzyt wraz z obliczeniami objętościowej i granicznej dyfuzji węgla. W efekcie można zaobserwować morfologię symulowanych mikrostruktur, odpowiadającą im segregację węgla, a także rozkład mikrotwardości. Wyniki te wraz z kinetyką ferrytycznej przemiany fazowej i przewidywanymi wartościami twardości stali wielofazowej są przedmiotem walidacji modelu. Przeprowadzono szereg eksperymentów dylatometrycznych przy stałych szybkościach chłodzenia w celu opracowania wykresu CTPc i walidacji przedstawionego modelu. Zbieżność wyników symulacji z danymi empirycznymi została potwierdzona ilościowo za pomocą dedykowanej funkcji celu oraz zestawienia danych w tabeli i na wykresach. Jednakże, wskazano na pewne rozbieżności jakościowe i ilościowe pod względem morfologii mikrostruktury, co było możliwe dzięki zastosowaniu szerokiego wachlarza różnych parametrów do walidacji modelu. Podkreślono, jak istotne jest zastosowanie odpowiedniej metodologii walidacji.

10

Study of phase transformations in complex phase steel using a mesoscale cellular automaton model Part 1: Modeling fundamentals

Opara Jarosław, Kuziak Roman

Journal of Metallic Materials

|

2020

|

Vol. 72, no. 3

17--31

EN

A two-dimensional mesoscale model based on the concept of hybrid cellular automata is developed to study phase transformations in a complex phase steel during continuous cooling. The model is capable of simulating microstructure evolution with carbon diffusion in the volume and along grain boundaries, γ/α interfaces migration into austenite, as well as formation of bainite and martensite islands during intensive cooling in lower temperatures. In contrast to the classic statistical approaches which are based on the assumption of modeling one point in the material with homogeneous microstructure, the proposed phase transformations’ model in the mesoscale accounts for material heterogeneity. The simulation results in the form of a digital material representation with microstructures and maps showing the carbon concentration field as well as microhardness distribution are presented. One of the main advantages of the model is that has only seven adjustment coefficients that are used in the fitting process.

PL

Dwuwymiarowy mezoskalowy model oparty na koncepcji hybrydowych automatów komórkowych został opracowany w celu badania przemian fazowych w stali wielofazowej podczas ciągłego chłodzenia. Model umożliwia symulację rozwoju mikrostruktury wraz z dyfuzją węgla w objętości, jak i wzdłuż granic ziaren oraz migracją powierzchni międzyfazowych γ/α do austenitu, a także powstawaniem wysp bainitu i martenzytu podczas intensywnego chłodzenia w niższych temperaturach. W odróżnieniu od klasycznych podejść statystycznych, które bazują na założeniu modelowania jednego punktu w materiale o jednorodnej mikrostrukturze, zaproponowany model przemian fazowych w mezoskali umożliwia uwzględnienie warunków niejednorodności materiału. Zaprezentowano wyniki symulacji w postaci cyfrowej reprezentacji materiału z mikrostrukturami oraz mapami przedstawiającymi pola stężenia węgla oraz rozkłady mikrotwardości. Jedną z głównych zalet modelu jest to, że regulowany jest tylko za pomocą siedmiu współczynników w procesie dopasowania.

11

Innowacyjna stal wysokokrzemowa z regulowaną niską zawartością zanieczyszczeń i wtrąceń niemetalicznych o kontrolowanej morfologii oraz odpowiednim poziomie inhibitora AlN z przeznaczeniem na wysokojakościowe blachy transformatorowe

Różański Piotr, Radwański Krzysztof, Niesler Marian, Woźniak Dariusz, Zdonek Bogdan, Mazur Artur, Pidvysots’kyy Valeriy, Kuziak Roman, Maracha Grzegorz, Fraś Wojciech

Journal of Metallic Materials

|

2020

|

Vol. 72, no. 2

63--82

PL

W artykule przedstawiono przebieg i wyniki badań przemysłowych wykonanych w ramach 1 Etapu projektu, którego końcowym celem jest opracowanie innowacyjnej stali elektrotechnicznej nowej generacji, przeznaczonej na blachy transformatorowe o wysokiej przenikalności magnetycznej (wysokiej indukcji 1,9 T i małej stratności 0,8 W/kg) z ziarnem zorientowanym (typ HGO) wraz z technologią jej wytwarzania w zakresie: wytapiania w konwertorze z obróbką pozapiecową uwzględniającą próżniowe odgazowanie stali w demonstracyjnej instalacji, ciągłego odlewania wlewków płaskich i walcowania ich na gorąco na półwyrób do dalszego przerobu. Pozostałe etapy wytwarzania blach transformatorowych obejmujące walcowanie na zimno, międzyoperacyjną obróbkę cieplną i cieplno-chemiczną oraz obróbkę powierzchniową stanowią tajemnicą przedsiębiorstwa. W ramach 1 Etapu projektu wykonano symulacje numeryczne i fizyczne wytapiania, odlewania i walcowania na gorąco stali o założonych parametrach jakościowych, celem uzyskania materiału do dalszych badań. Określono parametry wytapiania i odlewania zapewniające uzyskanie odpowiedniej jakości stali o maksymalnej zawartość tlenu całkowitego 12 ppm i udziale powierzchniowym wtrąceń niemetalicznych max. 0,05%, oraz wymagania techniczno-technologiczne urządzenia do obróbki ciekłej stali w próżni, stanowiącego instalację demonstracyjną, a także opracowano model reologiczny stali transformatorowej dla procesu walcowania blach na gorąco, z użyciem którego przeprowadzono wstępne symulacje w celu uzyskania rozkładów temperatury, odkształcenia i prędkości odkształcenia w walcowanym paśmie.

EN

The article presents the process and results of industrial tests carried out as part of the 1st Stage of the project, the final goal of which is to develop an innovative new-generation electrical steel designed for the manufacture of transformer plates with high magnetic permeability (high inductance of 1.9 T and low lossiness of 0.8 W/ kg) and with oriented grain (HGO type) together with the technology of its production in the scope of: melting of steel in a converter with ladle treatment taking into account vacuum degassing of steel in a demonstration installation, continuous casting of flat ingots and their hot rolling for further processing. The remaining stages of transformer plate production, including cold rolling, inter-operational heat and thermo-chemical treatment, as well as surface treatment operations, are a trade secret. As part of the 1st Stage of the project, numerical and physical simulations of melting, casting and hot rolling of steel with assumed quality parameters were carried out in order to obtain material for further research. The melting and casting processes parameters were determined to ensure obtaining the appropriate quality of steel with a maximum total oxygen content of 12 ppm and the surface fraction of non-metallic inclusions of max. 0.05%, technical and technological requirements for the device for liquid steel processing in vacuum constituting the demonstration installation were determined, and a rheological model of transformer steel for the sheet hot-rolling process was developed, with the use of which preliminary simulations were carried out to obtain temperature, deformation and strain rates in the rolled strip.

12

Mean field and full field modelling of microstructure evolution and phase transformations during hot forming and cooling of low carbon steels

Szeliga Danuta, Bzowski Krzysztof, Rauch Łukasz, Kuziak Roman, Pietrzyk Maciej

Computer Methods in Materials Science

|

2020

|

Vol. 20, No. 3

121--132

EN

The paper describes a critical comparison of mean field and full field approaches to modelling hot deformation/controlled cooling sequences for steels. Classification of the models, based on the balance between predictive capabilities and computing costs, is presented. Mean field models, which describe microstructure evolution and phase transformations were connected with thermomechanical finite element program and applied to simulation of the hot strip rolling process and cooling of tubes after hot rolling. Full field model described in the paper is a connection of the finite element (FE) and level set (LSM) methods. These methods were used to simulate heating/cooling sequence in the continuous annealing line. A suggestion to use a stochastic model as a bridge between mean field and full field approaches is made.

13

Numerical simulation of manufacturing process chain for pearlitic and bainitic steel rails

Milenin Andrij, Zalecki Władysław, Pernach Monika, Rauch Łukasz, Kuziak Roman, Zygmunt Tomasz, Pietrzyk Maciej

Archives of Civil and Mechanical Engineering

|

2020

|

Vol. 20, no. 4

125--142

EN

Computer system for the design of technology of the manufacturing of pearlitic and bainitic rails was presented in this paper. The system consists of the FEM simulation module of thermal–mechanical phenomena and microstructure evolution during hot rolling integrated with the module of phase transformation occurring during cooling. Model parameters were identified based on dilatometric tests. Physical simulations, including Gleeble tests, were used for validation and verification of the models. In the case of pearlitic steels, the process of subsequent immersions of the rail head in the polymer solution was numerically simulated. The objective function in the optimization procedure was composed of minimum interlamellar spacing and maximum hardness. Cooling in the air at a cooling bed was simulated for the bainitic steel rails and mechanical properties were predicted. The obtained results allowed us to formulate technological guidelines for the process of accelerated cooling of rails.

14

Material characterization for numerical simulation of manufacturing of automotive part made of magnesium alloy

Pietrzyk Maciej, Kuziak Roman, Bzowski Krzysztof, Rauch Łukasz, Ambroziński Mateusz, Gronostajski Zbigniew, Chorzępa Władysław

Archives of Civil and Mechanical Engineering

|

2020

|

Vol. 20, no. 1

72--81

EN

Evaluation of the possibility of substitution of steel part in the car body by the one made of AZ31 alloy was the main objective of the whole project. The objective of this paper was to determine the flow stress model, which accounts for the difference in the behavior of magnesium alloys during tension and compression. Tension tests on Zwick machine and compression tests on Gleeble 3800 were performed. Inverse analysis was applied to interpretation of the results of the tests. Separate numerical models for tension and compression were implemented into Abaqus software and simulations of the stamping were performed. Sensitivity of the results to the flow stress model was evaluated.

15

Precipitation-hardened low-carbon high-strength bainitic steels for manufacturing of fasteners

Kuziak Roman, Pidvysots’kyy Valeriy, Węglarczyk Stanisław, Pietrzyk Maciej

Journal of Metallic Materials

|

2019

|

Vol. 71, no. 3

8--11

EN

Design of the manufacturing chain for fasteners made of precipitation-hardened low-carbon high-strength bainitic steels was the objective of the paper. The choice of the material was based on the good performance of these steels in various applications. Compression tests at different temperatures (20-300°C) and different strain rates (0.1-10 s-1) were performed to provide data for identification of the flow stress model for the selected steels. Authors inverse algorithm was applied to determine coefficients in the flow stress model, which was implemented into the FE code Forge. Simulations of the whole manufacturing chain involving hot rolling of rods, controlled cooling, drawing and 4-step cold forging were performed. Physical simulations were performed on the Gleeble 3800 to validate material models, which were used in optimization of manufacturing chains for fasteners. Good predictive capability of the material models was confirmed. Final part of the paper presents an application of numerical modelling for the design of the best manufacturing technology. Since simulation of the one case of manufacturing requires very long computing times, application of classical mathematical optimization was not possible. Therefore, an approach known as variant optimization was applied. In this approach, trial and error method was combined with the knowledge of the expert. The objective was to improve the material flow in the forging and to improve the contact between the head of the fastener and the material being joined. Various variants of the technology were simulated and new technological parameters were proposed, which gave noticeable improvement of the objective function.

PL

W artykule scharakteryzowano proces projektowania technologii kucia elementów złącznych z niskowęglowych stali bainitycznych umacnianych wydzieleniowo. Technologię kucia zaprojektowano na podstawie symulacji numerycznych z wykorzystaniem programu Forge. Do symulacji użyto modelu reologicznego badanych stali opracowanego metodą analizy odwrotnej prób plastometrycznych zrealizowanych za pomocą symulatora Gleeble 3800. Badania plastometryczne przeprowadzono na próbkach cylindrycznych w przedziale temperaturowym 20-300°C i prędkości odkształcenia 0,1-10 s-1. Celem przeprowadzonych badań było przeprowadzenie symulacji fizycznych i numerycznych całego łańcucha produkcyjnego elementów złącznych z uwzględnieniem walcowania i chłodzenia walcówki, przeciągania i kucia na zimno. W końcowej części artykułu scharakteryzowano możliwości modelowania numerycznego w celu opracowania najkorzystniejszej technologii wytwarzania elementów złącznych. W tym przypadku zastosowanie klasycznych algorytmów optymalizacyjnych okazało się niemożliwe. Dlatego zastosowano podejście optymalizacji wariantów technologicznych metodą prób i błędów, połączoną z wiedzą ekspercką. W wyniku zastosowanej metody opracowano najkorzystniejszy wariant kucia zarówno z uwagi na płynięcie plastyczne materiału, jak również optymalny kontakt główki elementu złącznego z łączonym elementem.

16

Optimization of the heat treatment process to obtain the required distribution of mechanical properties in the rail head of pearlitic rails

Kuziak Roman, Pidvysotsk’yy Valeriy, Radwański Krzysztof, Mazur Artur, Zygmunt Tomasz, Pietrzyk Maciej, Rauch Łukasz, Bachniak Daniel

Journal of Metallic Materials

|

2019

|

Vol. 71, no. 1

3--9

EN

The paper presents metallurgically based approach allowing the design of the parameters of the pearlitic rail head heat treatment to obtain the targeted mechanical properties. The described solutions enable predicting the progress of phase transformations, final microstructure and mechanical properties distribution in the pearlitic rail subject to heat treatment. It also allows the optimization of the cooling conditions to obtain a strictly defined distribution of mechanical properties in the rail head. The program is developed as a result of research activities performed in the HyPremRail R&D project. The core of the program consists of the phase transformations model which is implemented in the numerical code based on the FEM for heat transfer calculations. The model predicts the pearlite nodule and colony size as well as cementite interlamellar spacing. Using these parameters, strength properties distribution in the rail can be predicted, since the phase transformations model is combined with the Fourier heat transfer equation. To perform the numerical simulations, the boundary conditions for heat treatment should be defined. On the contrary, using inverse analysis, the program can provide the cooling conditions allowing obtaining defined mechanical properties distribution in rail head.

PL

Artykuł przedstawia matematyczny model oparty na wiedzy metaloznawczej, umożliwiający zaprojektowanie parametrów obróbki cieplnej główki szyny ze stali perlitycznej w celu uzyskania pożądanych właściwości mechanicznych. Dzięki implementacji modelu w programie komputerowym opartym na metodzie elementów skończonych możliwe jest śledzenie postępu przemian fazowych w trakcie obróbki cieplnej główki szyny o strukturze perlitycznej, a w efekcie końcowym również przewidywanie parametrów mikrostruktury finalnej oraz właściwości mechanicznych szyny. Drugą funkcją programu jest określenie warunków obróbki cieplnej powodujących uzyskanie założonego rozkładu właściwości mechanicznych w główce szyny obrabianej cieplnie. Prezentowane podejście oraz program komputerowy opracowano w ramach prac związanych z realizacją projektu badawczo-rozwojowego „HyPremRail”. Po zadaniu warunków chłodzenia program realizuje lokalnie obliczenia odległości między płytkami cementytu, wielkości ziarna i kolonii perlitu w oparciu o opracowany model przemian fazowych, posługując się rozwiązaniem MES równania Fouriera, a następnie przelicza wartości uzyskanej odległości międzypłytkowej na twardość, granicę plastyczności i wytrzymałość na rozciąganie. Przeprowadzenie obliczeń wymaga zdefiniowania warunków początkowych i brzegowych procesu obróbki cieplnej. Z kolei zagadnienie optymalizacji parametrów procesu w celu uzyskania korzystnego rozkładu właściwości mechanicznych w obszarze główki rozwiązywane jest za pomocą metody obliczeń odwrotnych.

17

Fast model for phase transformations during cooling of pre-annealed multiphase steels

Szeliga Danuta, Kuziak Roman, Zalecki Władysław, Pidvysotskyy Valeriy, Chang Yuling, Bleck Wolfgang, Bachniak Daniel, Pietrzyk Maciej

Computer Methods in Materials Science

|

2019

|

Vol. 19, No. 4

150--161

EN

A thorough experimental and numerical analysis of phase transformations in a selected CP800 steel was the general objective of the paper. Dilatometric tests were performed for a wide range of cooling rates. Two models based on a mean field approach were considered. The first was an upgrade of the Johnson-Mehl-Avrami-Kolmogorov equation. The second model was based on the Leblond equation. Both models were identified using inverse analysis of the experimental data. Simulations of various cooling schedules were performed to validate the models. Phase compositions for these cooling schedules were determined. Following this the effect of elements' segregation during solidification of steel on the occurrence of marteniste/bainite bands was accounted for using the developed models.

PL

W artykule opisano doświadczalną i numeryczną analizę przemian fazowych w wybranej stali o podwyższonej wytrzymałości. Próby dylatometryczne wykonano w szerokim zakresie prędkości chłodzenia. Rozważono dwa modele wykorzystujące metodę średniego pola. Pierwszym modelem była zmodernizowana wersja modelu JMAK (Johnson-Mehl-Avrami-Kolmogorov). Drugim modelem było rozwinięcie równania Leblonda. Przeprowadzono identyfikację modeli wykorzystując rozwiązanie odwrotne dla prób dylatometrycznych. W celu walidacji modeli wykonano symulacje różnych schematów chłodzenia. Wyznaczono skład fazowy dla tych schematów. Następnie oszacowano wahania składu chemicznego w badanej stali i wykorzystano opracowane modele do określenie wpływu segregacji pierwiastków podczas krzepnięcia stali na powstawanie pasm martenzytu/bainitu.

18

Structure and mechanical properties of dual-phase steel following heat treatment simulations reproducing a continuous annealing line

Radwanski Krzysztof, Kuziak Roman, Rozmus Radoslaw

Archives of Civil and Mechanical Engineering

|

2019

|

Vol. 19, no. 2

453--468

EN

In the presented investigation, cold-rolled sheets of a selected dual-phase (DP) steel were heat-treated according to varying thermal profiles, thus reproducing continuous annealing process. Initially the samples were soaked at 780 and 810 °C for 0–60 s followed by water cooling. Next, samples were preliminary treated by applying the same conditions, however after water cooling these compositions were subject to tempering at 230, 380 and 460 °C for both 60 and 240 s. The characterization of the effect of heat-treatment parameters on the mechanical properties and structure is the main objective of this investigation. Mechanical properties of the samples after applied thermal profiles were in line with those requirements imposed on the commercial sheets of DP steels. The obtained results of the investigation showed that tempering deteriorates the Yield Ratio, defined as Rp0.2/Rm. This was caused by the martensite decomposition combined with carbide precipitation processes. Transmission electron microscopy observations revealed precipitated carbides, Fe3C in martensitic and M7C3 in ferritic areas. The quantitative results of the structural investigation were then applied to predict the Rp0.2 and Rm using the Perlade model. The results indicate that discrepancies between the measured tensile tests and calculated Rp0.2 and Rm do not exceed 10%.

19

Selection of the best phase transformation model for optimization of manufacturing processes of pearlitic steel rails

Kuziak Roman, Pidvysots'kyy Valeriy, Pernach Monika, Rauch Lukasz, Zygmunt Tomasz, Pietrzyk Maciej

Archives of Civil and Mechanical Engineering

|

2019

|

Vol. 19, no. 2

535--546

EN

Selection of the best model for simulation of manufacturing processes of pearlitic steel rails was the objective of the paper. Achieving a proper balance between its predictive capabilities and computing costs was used as a criterion. Review of the pearlitic transformation models was performed and modification of the JMAK equation was selected for further analysis. Empirical models were developed to describe microstructure and mechanical properties of rails. Dilatometric tests were performed to supply data for identification of the phase transformation model. Physical simulations of various thermal cycles were performed to validate and verify the models. Finite element (FE) simulations of the hot rolling provided distributions of the temperature and the austenite grain size at the cross section of the rail, which were used as an input for modelling of phase transformations during cooling. Accelerated cooling by a cyclic immersion of the rail head in the polymer solution was considered as a case study. Performed simulations confirmed good predictive capabilities of the model.