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1

The Influence of Cold Deformation and Annealing on Texture Changes in Austenitic Stainless Steel

Kowalska Joanna, Witkowska Małgorzata

Advances in Science and Technology. Research Journal

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2024

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Vol. 18, no 2

143--158

EN

Austenitic stainless steels are widely used in industry, from heavy industry and power generation to precision mechanics and electronics, accounting for about 2/3 of the stainless steels produced. The stability of austenite influences the properties and behaviour of these steels during deformation and annealing. This paper presents the results of research into austenitic metastable phase X5CrNi1810 steel, which was subjected to cold rolling (in the range of 5 to 80%) and then annealing (at temperatures of 500-900°C). The research focused mainly on changes in crystallographic texture parameters occurring during the analysed processes. It was found that the observed development of the deformation texture is complex due to the fact that several processes take place simultaneously. Namely, the deformation of austenite, the transformation of austenite into martensite, and the deformation of the resulting martensite. The texture of the deformed austenite was similar to the texture of the alloy type {112}<110>. After 80% deformation, the Goss-type {110}<001> texture component showed the highest intensity. The lack of {112}<111> orientation in the texture was due to the fact that this orientation changes to the {112}<110> martensite orientation as a result of the γ→α’ phase transition. Annealing of the deformed steel at 500°C led to an increase in the degree of texturing (sharpening of the texture), which was related to the improvement of the texture in this temperature range. Above 600°C, the degree of texturing decreased, which is directly related to the α’→γ reverse transformation and the subsequent recrystallization process. Magnetic studies indicate an increasing proportion of the magnetic phase α’ (martensite) together with an increasing degree of deformation. For deformation of 80%, the amount of magnetic phase reached a value of more than 33%. However, after annealing at a temperature of 800°C, there is no martensite in the structure, which indicates that, in these heat treatment conditions, the complete reverse transformation of martensite into austenite has already taken place.

2

Phenomenological model of cavitation erosion of nitrogen ion implanted HIPed Stellite 6

Szala Mirosław

Advances in Materials Science

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2023

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Vol. 23, nr 1(75)

98--109

EN

Stellites are a group of Co-Cr-C-W/Mo-containing alloys showing outstanding behavior under cavitation erosion (CE) operational conditions. The process of ion implantation can improve the CE resistance of metal alloys. This work presents the elaborated original phenomenological model of CE of nitrogen ion implanted HIP-consolidated (Hot Isostatically Pressed) cobalt alloy grade Stellite 6. The ultrasonic vibratory test rig was used for CE testing. The nitrogen ion implantation with 120 keV and fluence of 5 × 1016 N+/cm−2 improves HIPed Stellite 6 cavitation erosion resistance two times. Ion-implanted HIPed Stellite 6 has more than ten times higher CE resistance than the reference AISI 304 stainless steel sample. Comparative analysis of AFM, SEM and XRD results done at different test intervals reveals the kinetic of CE process. The model includes the surface roughness development and clarifies the meaning of cobalt-based matrix phase transformations under the nitrogen ion implantation and cavitation loads. Ion implantation modifies the cavitation erosion mechanisms of HIPed Stellite 6. The CE of unimplanted alloy starts on material loss initiated at the carbides/matrix interfaces. Deterioration starts with cobalt matrix plastic deformation, weakening the carbides restraint in the metallic matrix. Then, the cobalt-based matrix and further hard carbides are removed. Finally, a deformed cobalt matrix undergoes cracking, accelerating material removal and formation of pits and craters' growth. The nitrogen ion implantation facilitates ɛ (hcp—hexagonal close-packed)) → γ (fcc—face-centered cubic) phase transformation, which further is reversed due to cavitation loads, i.e., CE induces the γ → ɛ martensitic phase transformation of the cobalt-based matrix. This phenomenon successfully limits carbide removal by consuming the cavitation loads for martensitic transformation at the initial stages of erosion. The CE incubation stage for ion implanted HIPed Stellite 6 lasts longer than for unimplanted due to the higher initial content of γ phase. Moreover, this phase slows the erosion rate by restraining carbides in cobalt-based matrix, facilitating strain-induced martensitic transformation and preventing the surface from severe material loss.

3

Modeling of temperature-dependent cyclic performance of superelastic NiTi shape memory alloy

Xiao Yao, Ju Shuangyan, Lin Jianping

Computer Methods in Materials Science

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2022

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Vol. 22, No. 1

13--22

EN

In this paper, a three-dimensional micromechanical-based constitutive model is proposed to describe the temperature-dependent performance of a cyclic deformed superelastic NiTi shape memory alloy. The dominant texture of the specimen is prescribed as <111> direction along the longitudinal direction. Apart from martensitic transformation, various mechanisms regarding superelastic degradation are taken into consideration. In order to be extended from the single-crystal scale to the polycrystalline version, the constitutive model is implemented into finite element software. It is verified that the measured cyclic response of a superelastic NiTi is well reproduced by the presented approach. Furthermore, the predicting capability of the proposed model is verified by simulating the mechanical behavior of NiTi tube subjected to cyclic bending.

4

In-Situ Observation of Acicular Ferrite Transformation in High-Strength Low-Alloy Steel Using Confocal Laser Scanning Microscopy

Lee Sang-In, Shin Seung-Hyeok, Park Hyeonwoo, Kim Hansoo, Lee Joonho, Hwang Byoungchul

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 4

1497--1501

EN

In-situ observation of the transformation behavior of acicular ferrite in high-strength low-alloy steel using confocal laser scanning microscopy was discussed in terms of nucleation and growth. It is found that acicular ferrite nucleated at dislocations and slip bands in deformed austenite grains introduced by hot deformation in the non-recrystallization austenite region, and then proceeded to grow into an austenite grain boundary. According to an ex-situ EBSD analysis, acicular ferrite had an irregular shape morphology, finer grains with sub-grain boundaries, and higher strain values than those of polygonal ferrite. The fraction of acicular ferrite was affected by the deformation condition and increased with increasing the amount of hot deformation in the non-recrystallization austenite region.

5

Experimental confirmation of high-temperature phase boundaries in the nickel-rich part of Ni-Al-Cr system

Maciąg T., Migas D., Płachta A.

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 4

art. no. e203, 2022

EN

Precise determination of the course of phase boundaries is particularly important for alloys operating at elevated temperatures. In the case of multi-component materials such as nickel superalloys, computational methods are often used for this purpose. They are based on binary and ternary systems and require reliable experimental data. Commonly used research methods for determining phase boundaries at elevated temperature have a number of limitations and it is difficult to interpret their results without the support of other studies. This work presents a series of experiments to confirm the course of phase boundaries γ′/(γ′ + γ) and (γ′ + γ)/γ in Ni-Al-Cr system, particularly at 600 °C. For this purpose, a series of alloys from Ni-rich part of Ni–Al-Cr ternary system was prepared by vacuum induction melting (VIM) and casting into graphite mold under an argon protective atmosphere. Samples after machining were subjected to compression tests using the Gleeble 3800 thermomechanical simulator at room temperature as well as directly at 600 °C after pre-heating at 1100 °C. Stress–strain curves of various character were obtained and were associated with the appropriate phase structure confirmed by X-ray diffraction (XRD) analysis. The relationship between the phase structure of the studied alloys and their mechanical properties has been proven. Compression results were compared with the results of hardness measurements, high-temperature calorimetric solution method and differential thermal analysis (DTA). The obtained results showed a very good agreement in terms of the course of the γ′/(γ′ + γ) and (γ′ + γ)/γ phase boundary in Ni-Al-Cr system.

6

Przemiany fazowe zachodzące w układach Fe/NH3/H2 oraz Fe-N

Michalski Jerzy, Frączek Tadeusz

Inżynieria Powierzchni

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2021

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nr 1

5--13

PL

W artykule omówiono na podstawie literatury przemiany fazowe w azotkach żelaza wytworzonych na proszkach żelaza i na próbkach litych. Przedstawiono przemiany fazowe podczas wyżarzania w atmosferze NH3/H2 oraz w atmosferach obojętnych. Wskazano podobieństwo przemian fazowych w różnych atmosferach zastosowanych podczas wyżarzania. Opisano warunki przemian fazowych w azotkach żelaza podczas wyżarzania w atmosferze NH3/H2, w argonie oraz próżni. Przemiany fazowe zachodzące podczas wyżarzania w atmosferze NH3/H2 są odwracalne, występuje w nich zjawisko histerezy. Podczas przemiany fazowej ɛ→γ’ w atmosferze NH3/H2 do momentu zakończenia przemiany ma miejsce emisja azotu do atmosfery. Natomiast niezbędnym warunkiem przebiegu przemiany γ’→ɛ jest strumień azotu z atmosfery do powierzchni. Przemiany fazowe podczas wygrzewania w próżni i argonie są nieodwracalne. Podczas ciągłego ogrzewania azotowanych proszków żelaza z szybkością 30 K/min w próżni i argonie mogą wystąpić dwie przemiany fazowe, którym nie towarzyszy ubytek masy. Pierwsza, (α+γ’)→γN w zakresie temperatur 540÷550°C w próżni i 620÷630°C w argonie oraz druga, (γ+γ’)→ɛ w zakresie 610÷620°C w próżni i 690÷710°C w argonie. W przypadku nagrzewania w argonie początek ubytku masy rejestrowano w temperaturze ok. 860°C, natomiast w próżni kończy się w tej temperaturze odazotowanie austenitu azotowego γN. Podczas wyżarzania w temperaturze 360ºC przemianie fazowej ɛ→γ’ w warstwie ɛ/γ’ towarzyszy wzrost grubości fazy γ’, który odbywa się kosztem grubości strefy ɛ, przy czym całkowita grubość warstwy po przemianie jest taka sama, jak jej grubość w stanie wyjściowym. W temperaturze 420ºC po zakończonej przemianie ɛ→γ’, utworzona monofazowa warstwa γ’ jest grubsza od warstw ɛ/γ’ w stanie wyjściowym.

EN

In the article, based on the literature, the phase changes in iron nitrides on iron powders and on solid samples were discussed. Phase transformations in NH3/H2 atmosphere and in inert atmospheres are discussed. The similarity of phase transformations in different atmospheres used during annealing were indicated. The conditions of phase transformations in iron nitrides during annealing in NH3/H2 atmosphere, argon and vacuum were discussed. Phase transformations occurring during annealing in the NH3/H2 atmosphere are reversible and there is a hysteresis phenomenon. During the phase transformation ɛ→γ' in the NH3/H2 atmosphere until the transformation is completed, nitrogen emission to the atmosphere takes place. On the other hand, the condition for the course of the transformation of γ'→ɛ is the nitrogen flow from the atmosphere to the surface. Phase changes during heating in vacuum and argon are irreversible. During continuous heating at a rate of 30 K / min in vacuum and argon, nitrided iron powders, two phase transformations may occur, which are not accompanied by weight loss, the first (α+γ') →γN in the temperature range 540÷550°C in a vacuum and 620÷630°C in argon and the second (γ+γ') →ɛ in the range of 610÷620°C in vacuum and 690÷710°C in argon. In the case of heating in argon, the onset of weight loss was recorded at a temperature of about 860°C. Whereas in vacuum the denitration of nitrogen austenite γN ends at this temperature. During annealing at the temperature of 360°C, the phase change ɛ→γ′ in the ɛ/γ′ layer is accompanied by an increase in the thickness of the γ′ phase, which is at the expense of the thickness of the ɛ zone, while the total thickness of the layer after the transformation is the same as its initial thickness. At the temperature of 420°C, after the completion of the γ′ transformation, the formed monophasic layer γ′ is thicker than the ɛ/γ′ layers in the initial state.

7

Application of acoustic emission to the analysis of phase transformations in 27MnCrB5-2 steel tests during continuous cooling

Trafarski Andrzej, Łazarska Małgorzata, Ranachowski Zbigniew

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2021

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Vol. 69, nr 6

art. no. e139389

EN

The goal of the research was to analyze the acoustic emission signal recorded during heat treatment. On a special stand, samples prepared from 27MnCrB5-2 steel were tested. The steel samples were heated to 950°C and then cooled continuously in the air. Signals from phase changes occurring during cooling were recorded using the system for registering acoustic emission. As a result of the changes, Widmanstätten ferrite and bainite structures were observed under a scanning microscope. The recorded acoustic emission signal was analyzed and assigned to the appropriate phase transformation with the use of artificial neural networks.

8

Phase Evolution During Extraction and Recovery of Pure Nd from Magnet

Rasheed Mohammad Zarar, Nam Sun-Woo, Lee Sang-Hoon, Park Sang-Min, Cho Ju-Young, Kim Taek-Soo

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 4

1001--1005

EN

Liquid Metal Extraction process using molten Mg was carried out to obtain Nd-Mg alloys from Nd based permanent magnets at 900°C for 24 h. with a magnet to magnesium mass ratio of 1:10. Nd was successfully extracted from magnet into Mg resulting in ~4 wt.% Nd-Mg alloy. Nd was recovered from the obtained Nd-Mg alloys based on the difference in their vapor pressures using vacuum distillation. Vacuum distillation experiments were carried out at 800°C under vacuum of 2.67 Pa at various times for the recovery of high purity Nd. Nd having a purity of more than 99% was recovered at distillation time of 120 min and above. The phase transformations of the Nd-Mg alloy during the process, from Mg12Nd to α-Nd, were confirmed as per the phase diagram at different distillation times. Pure Nd was recovered as a result of two step recycling process; Liquid Metal Extraction followed by Vacuum Distillation.

9

Mechanical and thermal stability of retained austenite in plastically deformed bainite-based TRIP-aided medium-Mn steels

Kozłowska Aleksandra, Grajcar Adam, Janik Aleksandra, Radwański Krzysztof, Krupp Ulrich, Matus Krzysztof, Morawiec Mateusz

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 3

807--820

EN

Advanced medium-Mn sheet steels show an opportunity for the development of cost-effective and light-weight automotive parts with improved safety and optimized environmental performance. These steels utilize the strain-induced martensitic transformation of metastable retained austenite to improve the strength–ductility balance. The improvement of mechanical performance is related to the tailored thermal and mechanical stabilities of retained austenite. The mechanical stability of retained austenite was estimated in static tensile tests over a wide temperature range from 20 °C to 200 °C. The thermal stability of retained austenite during heating at elevated temperatures was assessed by means of dilatometry. The phase composition and microstructure evolution were investigated by means of scanning electron microscopy, electron backscatter diffraction, X-ray diffraction and transmission electron microscopy techniques. It was shown that the retained austenite stability shows a pronounced temperature dependence and is also stimulated by the manganese addition in a 3–5% range.

10

Wpływ odkształcenia plastycznego na przemiany austenitu przechłodzonego stali mikrostopowej

Opiela Marek, Wojtacha Anna

Stal, Metale & Nowe Technologie

|

2019

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nr 1-2

74--80

PL

W pracy przedstawiono wyniki badań wpływu odkształcenia plastycznego oraz szybkości chłodzenia na strukturę i postać krzywych przemian fazowych austenitu przechłodzonego stali mikrostopowej z Nb, Ti, V i B. Wyznaczono krzywe przemian austenitu przechłodzonego nieodkształconego plastycznie (CTPc) oraz odkształconego plastycznie (OCTPc).

EN

The aim of the paper is to investigate the influence of plastic deformation and cooling rate on the structure and shape of the supercooled austenite transformations diagrams of a Nb-Ti-V-B microalloyed steel. The CCT diagrams of underformed and plastically deformed supercooled austenite were developed. The plastic deformation of steel prior to the start of phase transformations results in a sharp acceleration of pearlitic transformation and a slight translation of bainitic transformation towards shorter times. The elaborated curves of supercooled austenite transformations of the steel create possibilities to develop an industrial technology for thermomechanically treated forgings of high mechanical properties.

11

Hartowanie indukcyjne elementów płaskich metodą przelotową

Iskierka Sławomir, Iskierka Iwona

Przegląd Elektrotechniczny

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2019

|

R. 95, nr 12

132--135

PL

Przedmiotem pracy jest analiza numeryczna procesu hartowania indukcyjnego stali. Opracowano model matematyczny i numeryczny procesu hartowania indukcyjnego, w którym uwzględniono wzajemne wpływy zjawisk elektromagnetycznych i cieplnych oraz wpływ pola temperatury na przemiany fazowe. Pole elektromagnetyczne obliczono opierając się na równaniach Maxwella, biorąc pod uwagę zmianę konduktywności i przenikalności magnetycznej materiału w czasie trwania procesu hartowania. Udział poszczególnych struktur w czasie nagrzewania i chłodzenia wyznaczono na podstawie wykresów CTPi i równań Avramiego, Koistinena i Marburgera.

EN

The subject of the paper is the process of steel induction hardening. There were made: a mathematical and numerical models of the induction hardening in which there were considered interactions of electromagnetic and thermal effects and the influence of thermal field on phase transformations and structural changes in the hardened element. The electromagnetic field was computed based on Maxwell equations, considering changes of material conductivity and magnetic permeability during the hardening process. The fractions of the particular structures in the proces of heating and cooling were computed on the grounds of TTT graphs and equations of Avrami, Koistinen and Marburger.

12

Effect of thermal annealing on structural and optical properties of In doped Ge-Se-Te chalcogenide thin films

Singh Pravin Kumar, Tripathi S. K., Dwivedi D. K.

Materials Science Poland

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2019

|

Vol. 37, No. 4

554--562

EN

Thin films of Ge10–xSe60Te30Inx (x = 0, 2, 4 and 6) were developed by thermal evaporation technique. The annealing effect on the structural properties of Ge10–xSe60Te30Inx (x = 0, 2, 4 and 6) films has been studied by X-ray diffraction (XRD). The XRD results indicate amorphous nature of the as-prepared films whereas crystalline phases in annealed films were identified. Structural parameters such as average crystallite size, strain, and dislocation were determined for different annealing temperatures. Effect of annealing on optical constants of prepared films has been explored using UV-Vis spectrophotometer in the wavelength range of 400 nm to 1000 nm. Various optical constants were determined depending on annealing temperature. It has been noticed that the film transparency and optical bandgap Eg have been reduced whereas the absorption coefficient α and extinction coefficient k increased with increasing annealing temperature. It was found that the prepared samples obey the allowed direct transition. The reduction in optical bandgap with annealing temperature has been described by Mott and Davis model. Due to annealing dependence of the optical parameters, the investigated material could be utilized for phase change memory devices.

13

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

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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.

14

Transformation Diagrams of Selected Steel Grades with Consideration of Deformation Effect

Kawulok R., Schindler I., Mizera J., Kawulok P., Rusz S., Opěla P., Podolínský P., Čmiel K. M., Mališ M.

Archives of Metallurgy and Materials

|

2018

|

Vol. 63, iss. 1

55--60

EN

The aim of this article was to assess the effect of previous plastic deformation on the transformation kinetics of selected steels with a wide range of chemical composition. Transformation (CCT and DCCT) diagrams were constructed on the basis of dilatometric tests on the plastometer Gleeble 3800 and metallographic analyses supplemented by measurements of HV hardness. Effect of previous deformation on transformation was evaluated of the critical rate of formation of the individual structural components (ferrite, pearlite and bainite) in the case of formation of martensite respect to Ms temperature. Previous plastic deformation accelerated especially diffuse transformations (ferrite and pearlite), temperature of Ms was lower after previous plastic deformation and bainitic transformation was highly dependent on the chemical composition of steel.

15

The Analysis of Thermomechanical States in Multipass Arc Weld Surfaced Steel Elements

Winczek J.

Archives of Metallurgy and Materials

|

2018

|

Vol. 63, iss. 4

1615--1628

EN

The paper presents the analysis of temperature fields, phase transformations, strains and stresses in a cuboidal element made from S235 steel, surfaced with multipass GMA (Gas Metal Arc) method. The temperature field is described assuming a dual-distribution heat source model and summing up the temperature fields induced by the padded weld and by the electric arc. Dependence of stresses on strains is assumed on the basis of tensile curves of particular structures, taking into account the influence of temperature. The calculations were carried out on the example of five welds in the middle of the plate made of S235 steel. The simulation results are illustrated in graphs of thermal cycles, volume shares of structural components and stresses at the selected points of cross-section, and the temperature and strain distributions in the whole cross section.

16

Experimental study temperature evolution of pseudoelastic TiNi alloys during shock-induced phase transformation

Shen L., Liu Y., Shan J.

Archives of Mechanics

|

2018

|

Vol. 70, nr 3

191--205

EN

The temperature evolution and the mechanical characteristics of pseudoelasticity TiNi alloys have been studied experimentally at different strain rates. During SHPB testing, the temperature changes were in situ measured by an infrared system recording infrared radiation emitted from the surface of the specimen. It was found that the temperature evolution and the mechanical behavior has a remarkable strain rate effect. With the strain rate increasing, both phase transition subsequent stress and modulus of loading the phase transition stage were higher, exhibiting significant strain and the strain rate hardening characteristic. They were accompanied by the temperature increasing, which suggest that the stress increments result from the temperature change, independently of the strain rate. Calculation analysis results show that latent heat and the dissipated energy in the form of the hysteresis loops, are mainly the sources of the temperature change.

17

Austenite transformation simulation for a controlled rolling processing technology development

Kaverinsky V.

Archives of Mechanical Technology and Materials

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2018

|

Vol. 38

35--39

EN

Using an originally-developed computer model and appropriate software the impact of deformation on austenite phase transformation in low carbon alloyed steel was carried out. The computer simulation takes into account an impact of the deformation degree and takes into account non-constant cooling rate. That makes it useful for the development of thermal and deformation technological processes development. Based on the simulation results a technology of controlled rolling of low carbon steel alloyed by carbide forming elements (Nb, V, Ti) was developed. The proposed technique allows production of rolled steel sheets with high strength and plastic properties, as well as high impact strength in normal and low temperatures.

18

Numerical analysis of temperature and residual stresses in hot-rolled steel strip during cooling in coils

Witek S., Milenin A.

Archives of Civil and Mechanical Engineering

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2018

|

Vol. 18, no. 2

659--668

EN

The main factors influencing on the level of residual stresses in hot rolled steel strips are related with uneven temperature and microstructure changes during cooling on the run-out table and in a coil. That is why in this work, development of coil cooling model with taking into account the influence of radial stresses on the effective thermal conductivity in the radial direction was performed. In order to assess the influence of the phase transformations in the coil on the level of residual stresses, the different laminar cooling strategies were applied. The results of numerical simulations obtained in this work were validated in industrial conditions. It is shown that the end of phase transformations in the strip coil has a significant influence on the level of residual stresses.

19

Analityczno-numeryczna analiza spawania laserowego płaskowników smukłych

Wróbel J., Kulawik A., Bokota A.

Przegląd Spawalnictwa

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2017

|

R. 89, nr 6

36--42

PL

W pracy przedstawiono model analityczno-numeryczny oraz analizę zjawisk cieplnych, przemian fazowych i zjawisk mechanicznych towarzyszących spawaniu techniką laserową smukłych elementów płaskich. Do rozwiązania zagadnienia przewodzenia ciepła zastosowano metodę funkcji Greena. Model szacowania udziału faz oraz ich kinetyki oparto na wykresie spawalniczym ciągłego chłodzenia (CTPc-S). Udziały faz metalurgicznych powstających podczas ciągłego nagrzewania i chłodzenia (austenit, perlit lub bainit) wyznaczano równaniem Johnsona-Mehla i Avramiego. Do wyznaczania tworzącego się martenzytu wykorzystano zmodyfikowane równanie Koistinena i Marburgera. Naprężenia i odkształcenia wyznaczono z rozwiązania metodą elementów skończonych równań równowagi w formie prędkościowej. Uwzględniono odkształcenia cieplne, strukturalne, plastyczne oraz odkształcenia indukowane przemianami fazowymi. Do wyznaczania odkształceń plastycznych zastosowano warunek plastyczności Hubera-Misesa ze wzmocnieniem izotropowym, natomiast odkształcenia plastyczne indukowane przemianami fazowymi obliczano formułą Leblonda. Dokonano analizy składu fazowego i naprężeń towarzyszących spawaniu doczołowemu elementów wykonanych z niskowęglowej spawalnej stali (S235). Analizę przeprowadzono dla dwóch wersji spawania: pojedynczą wiązką laserową oraz podwójnymi wiązkami, z których jedna została użyta do podgrzewania wstępnego, a druga do spawania.

EN

In the paper an analytical-numerical model and the analysis of thermal phenomena, phase transformations and mechanical phenomena occur in laser welding of thin at bars were presented. To solve the heat transfer equation, the method of Green’s function was used. To calculate the phase fractions and their kinetics the model based on the analysis of the continuous cooling diagram for the welding (CCT) is used. Phase fractions which occur during the continuous heating and cooling (austenite, pearlite or bainite) are described by Johnson-Mehl-Avrami (JMA) formula. To determine the formed martensite the modified Koistinen-Marburger (KM) equation is used. The stress and strain are determined by the solution of the equilibrium equations in the rate form using finite element method. In the model the thermal, structural, plastic strains and induced plasticity are taken into account. To calculate the plastic strains the Huber-Mises plasticity condition with isotropic hardening is used. Whereas to determine transformations induced plasticity the modified Leblond model is applied. The analysis of the phase content and stress state which occur during the butt welding of elements made of low carbon steel (S235) were performed. The calculations were carried out for the two cases of welding: a single laser beam and a double laser beam, where first was a preheating source and the second the main welding source.

20

Analiza deformacji cienkościennych kompensatorów dylatacji wykonanych z materiałów metastabilnych

Jamka K.

Przegląd Mechaniczny

|

2017

|

nr 11

44--47

PL

W pracy przedstawiona została analiza MES cienkościennych kompensatorów dylatacji wykonanych ze stali nierdzewnej 316L z uwzględnieniem przemiany fazowej w temperaturze 4,2 K. Stworzony w programie CAD model kompensatora został następnie zaimportowany do środowiska MES w celu poddania trzem analizom uwzględniającym różnorodne warunki obciążeniowe.

EN

The aim of this work was the FEM analysis considering the phase transformation in the temperature of 4.2 K of the thin-wall expansion joints made of 316L stainless steel. Designed in CAD software model was then imported to the FEM environment to subject for 3 different analysis taking into account various loading conditions.