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1

Effect of hot deformation and isothermal holding temperature on retained austenite characteristics in 3-5% Mn multiphase steels

Opiela Marek, Grajcar Adam, Pakieła Wojciech

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2023

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Vol. 71, nr 2

art. no. e144611

EN

The paper presents stress-strain characteristics recorded during the four-step compression of axisymmetric samples in the Gleeble thermomechanical simulator. The hot deformability of three steels with Mn concentrations of 3%, 4% and 5% was compared. The analysis of the influence of plastic deformation and Mn content on the microstructure of alloys, and in particular, on a fraction and morphological features of the retained austenite, was performed. The proportion of the retained austenite was determined by the X-ray diffraction method. It was found that the content of Mn in the range from 3% to 5% does not have a significant impact on the high-temperature resistance of the steel during compression tests, but it has a significant influence on the microstructure of the steel and the fraction of retained austenite. The optimal conditions for maximizing the proportion of retained austenite were obtained at the temperature of 400 °C, and it decreased with increasing Mn concentration in the steel. It has been shown that it is related to the redistribution of carbon from the remaining austenite fraction with an increase in the manganese content. The mechanical properties were determined on the basis of hardness measurements.

2

Preliminary Structures Assessment of Some TRIP Steels

Pantilimon Mircea Cristian, Berbecaru Andrei-Constantin, Coman George, Sohaciu Mirela G., Dumitrescu Ruxandra Elena, Ciucă Sorin, Gherghescu Ioana-Arina, Predescu Cristian

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 2

491--498

EN

Automotive industry is constantly interested in building cars made of light and high strength parts in order to reduce the emission levels, the fuel consumption and minimize the effects of a car crash. Some parts may be made of lighter materials, but the steel ones must compensate the strength needed for the car body. Research is made for finding new materials showing high strength combined with high ductility. Among them, transformation - induced - plasticity steels are of great interest, efforts being made to improve their characteristics. A new composition of such a steel is presented, its features being compared with those of three other steels of the same class and category. Optical microscopy at different magnifications is performed, together with Vickers hardness test. Structural particularities are found for each tested steel, justified by their own chemical compositions. The new steel reveals important characteristics: besides the mainly bainitic structure, it has both larger ferritic areas and amounts of retained austenite, making him proper for further study.

3

The qualitative-quantitative approach to microstructural characterization of nanostructured bainitic steels using electron microscopy methods

Królicka Aleksandra, Janik Aleksandra, Żak Andrzej, Radwański Krzysztof

Materials Science Poland

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2021

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Vol. 39, No. 2

188-199

EN

Both qualitative and quantitative analyses play a key role in the microstructural characterization of nanobainitic steels focused on their mechanical properties. This research demonstrates various methods of microstructure analysis using transmission electron microscopy (TEM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) techniques, taking into account these two approaches. The structural constituents have been qualitatively characterized using TEM and selected area electron diffraction (SAED), together with quantitative analysis based on the misorientation angle (EBSD). Besides, quantitative measurement of austenite with both blocky and film-like morphologies has been carried out. Due to the scale of nanostructured bainite, it is also important to control the thickness of bainitic ferrite and film-like austenite; hence, a method for measuring their thickness is presented. Finally, the possibility of measuring the prior-austenite grain size by the EBSD method is also demonstrated and compared with the conventional grain boundary etching method. The presented methods of qualitative and quantitative analyses form a complementary procedure for the microstructural characterization of nanoscale bainitic steels.

4

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

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2021

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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.

5

Nieniszcząca ocena zawartości austenitu szczątkowego w stali X45NiCrMo4 techniką amplitudowo-częstotliwościową prądów wirowych

Kondej Adam, Nawrocki Piotr

Inżynieria Powierzchni

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2021

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nr 3

5--11

PL

Praca dotyczy zastosowania techniki amplitudowo-częstotliwościowej prądów wirowych do oceny zawartości austenitu szczątkowego w stali narzędziowej X45NiCrMo4 po różnych obróbkach cieplnych. Aparaturę pomiarową stanowił Wirotest M2 z zestawem głowic o różnych częstotliwościach pracy: 91, 283 i 432 kHz oraz 1,15 i 2,41 MHz. Przeprowadzone badania wskazują, że największą korelację wyników dla metody prądów wirowych i dyfrakcji rentgenowskiej (XRD) uzyskano dla głowicy 432 kHz. Pozwala ona na pośrednie oszacowanie procentowej zawartości austenitu szczątkowego zarówno za pomocą analizy amplitudowej, jak i częstotliwościowej . Wraz ze wzrostem zawartości austenitu szczątkowego rośnie wartość amplitudy napięcia oraz częstotliwości sygnału prądowirowego . Pomiar amplitudowo-częstotliwościowy może być alternatywą lub uzupełnieniem dla drogiej i czasochłonnej metody XRD.

EN

The work concerns the application of the amplitude-frequency eddy current technique to assess the content of residual austenite in the X45NiCrMo4 tool steel after various heat treatments. The measuring equipment was Wirotest M2 with a set of heads with different frequencies: 91 , 283, 432 kHz and 1.15, 2.41 MHz. The conducted research shows that the greatest correlation of the results for the eddy current and X-ray diffraction (XRD) method was obtained for the 432 kHz head. It allows an indirect estimation of the percentage of the residual austenite content by both amplitude and frequency analysis. With the increase of the residual austenite content, the value of the voltage amplitude and the frequency of the eddy current signal increases. Amplitude-frequency measurement can be an alternative or supplement to the expensive and time consuming XRD method.

6

Influence of Heat Treatment and Nickel Content on the Properties of the GX4CrNi13-4 Steel

Kaňa V., Krutiš V., Bořil P., Záděra A., Rimko M.

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 1

37--41

EN

For the EN GX4CrNi13-4 martensitic stainless steel, research was conducted to investigate the impact of the quenching intensity and the content of nickel on the mechanical properties and amount of retained austenite. It was found that the amount of retained austenite significantly increases with growing nickel concentration. On the other hand, the cooling rate at quenching makes a difference only if the cooling is intensive, then amount of retained austenite decrease. A higher nickel content improves the mechanical properties. With more intensive cooling, the tensile strength decreases while the yield strength increases. The ductility is not significantly affected by the cooling intensity.

7

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.

8

Microstructure-Properties Relationship and Mechanical Stability of Retained Austenite in Thermomechanically Processed Medium-C TRIP Steel at Different Deformation Temperatures

Skowronek A., Kozłowska A., Grajcar A., Morawiec M.

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 2

941--949

EN

The paper presents the effect of deformation temperature on the mechanical stability of retained austenite in a multiphase TRIP steel. Series of static tensile tests were carried out in the temperature range –20 to 140°C in order to simulate the temperatures occurring during stamping process of automotive steel sheets and conditions of their exploitation. Samples deformed at 20°C and 60°C showed the best combination of strength and ductility. It was related to the gradual transformation of retained austenite into martensite. Obtained results revealed that the intensity of TRIP effect is significantly related to the deformation temperature. The amount of retained austenite, which transformed into martensite during plastic deformation decreases as the deformation temperature increases. It was also found that the stability of retained austenite depends on its morphology. The obtained results showed the relationship between deformation temperature and the stability of retained austenite. The chemical composition and microstructure of multiphase steels dedicated to the automotive industry should be designed for providing the maximum TRIP effect at the specific deformation temperatures.

9

Physical simulation and dilatometric study of double-step heat treatment of medium-Mn steel

Skowronek A., Morawiec M., Ruiz-Jimenez V., Garcia-Mateo C., Grajcar A.

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 4

578--588

EN

The work addresses physical simulation and dilatometric study of one-step and double-step heat treatments of medium-Mn steel designed for automotive sheets. The conventional one-step isothermal bainitic transformation was applied as the reference heat treatment. The newly implemented heat treatment consisted of isothermal holding in a bainitic region followed by additional holding of the material at reduced temperature also in the bainitic range. This step was added to refine the microstructure, which led to the stabilization of the retained austenite. Calculations of equilibrium state and non-equilibrium cooling and simulations of the developed thermal cycles were performed using the thermodynamic JMatPro software. The physical simulations of the heat treatment were performed in the dilatometer. The obtained samples were subjected to microscopic observations using light and SEM microscopy. One- and two-step heat treatments allowed to obtain bainitic structures with high contents of retained austenite. Lowering the temperature of one-step isothermal holding resulted in the bainite refinement and adjacent retained austenite. The increased Mn content in steel increased its susceptibility to form coalesced bainite resulting in the partial formation of thicker plates despite a decrease in a process temperature.

10

Obróbka cieplna stali średniomanganowych dla motoryzacji

Grajcar Adam, Morawiec Mateusz, Skowronek Adam

Stal, Metale & Nowe Technologie

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2019

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nr 7-8

12--18

PL

Nowoczesne materiały konstrukcyjne wykorzystywane w branży automotive powinny łączyć wysoką wytrzymałość z dobrą formowalnością – są to własności do niedawna wykluczające się. Z drugiej strony koszty produkcji muszą być relatywnie niskie, gdyż aspekt ekonomiczny jest niezwykle ważny w obecnych czasach. Wymienione własności wytrzymałościowe można uzyskać dzięki rozdrobnieniu ziarna, jak również wygenerowaniu w stali austenitu szczątkowego, którego przemiana powoduje znaczne umocnienie materiału podczas odkształcenia. Koszty produkcji maleją wraz z ograniczeniem zawartości drogich dodatków stopowych. Cechy te wykazują stale średniomanganowe.

EN

Advanced structural materials used in the automotive industry should combine high strength and good formability – a pair of properties which until recently were mutually exclusive. On the other hand, production costs must be relatively low because the economic aspect is extremely important nowadays. The mentioned strength properties can be obtained due to grain refinement as well as the generation of retained austenite in steel, which is transformed during deformation causing the significant strain hardening of the material. Production costs decrease with the reduction of the content of expensive alloying elements. These features are the domain of medium manganese steels.

11

Hartowanie z wymrażaniem stali chromowych przeznaczonych na walce hutnicze

Pawlak Stanisław Jerzy

Stal, Metale & Nowe Technologie

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2019

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nr 9-10

82--86

PL

W pracy analizowano stabilność strukturalną austenitu w stalach: NC7VL, NC7H3VL i NC7H5VL, przeznaczonych na kute walce robocze do walcowania blach na zimno. Hartowanie z wymrażaniem w temperaturze około -100°C prowadzi do obniżenia zawartości austenitu w badanych stalach. Obróbka ta wraz z analizami procesów cieplnych stanowi podstawę technologii produkcji walców roboczych o podwyższonej jakości.

EN

Austenite stability in the NC7VL, NC7H3VL and NC7H5VL steels designed for work rolls for cold-rolling has been studied. Sub-zero quenching at about -100°C leads to the lowering of austenite content in these steels. The heat treatment and the heat exchange analysis are the basis for the production technology of high quality work rolls.

12

Strategie obróbki cieplnej dla zimnowalcowanych i gorącowalcowanych taśm z karoseryjnych stali średniomanganowych

Morawiec Mateusz, Grajcar Adam, Skowronek Adam, Kozłowska Aleksandra

Hutnik, Wiadomości Hutnicze

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2019

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Vol. 86, nr 8

267--271

PL

Przedstawiono strategie obróbki cieplnej dla karoseryjnych taśm ze stali średniomanganowych. Celem części badawczej było zbadanie wpływu temperatury wyżarzania międzykrytycznego z zakresu 680-800°C przez 1h na stabilizację austenitu szczątkowego w stali średniomanganowej. Materiałem wykorzystanym w eksperymencie była stal zawierająca 0,16% C, 4,7% Mn, 1,6% Al, 0,2% Mo, 0,2% Si. Zakres pracy obejmował badania dylatometryczne, twardości oraz obrazowanie na mikroskopie świetlnym i skaningowym. Wyżarzanie międzykrytyczne przeprowadzone w temperaturze 700 oraz 680°C umożliwiło wytworzenie w strukturze stabilnego austenitu szczątkowego.

EN

Heat treatment strategies for autobody medium-manganese steel sheets were presented. The aim of the research work was to investigate an effect of intercritical annealing temperature in a range of 680-800°C for 1h on the stabilization of retained austenite in a medium manganese steel. The material used in the experiment was a steel containing 0.16% C, 4.7% Mn, 1.6% Al, 0.2% Mo, 0.2% Si. The scope of the research included dilatometer tests, hardness tests and imaging using light and scanning electron microscopes. Intercritical annealing carried out at 700 and 680°C allowed forming some stable retained austenite in the structure.

13

Analiza technologii przelotowego nagrzewania walcówki do zakresu temperatur dwuetapowej obróbki cieplnej typu TRIP

Wiewiórska Sylwia, Muskalski Zbigniew, Wieczorek Paweł

Hutnik, Wiadomości Hutnicze

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2019

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Vol. 86, nr 12

370--377

PL

W pracy przeanalizowano możliwość zastosowania szybkiego, oporowego lub indukcyjnego nagrzewania, półwyrobów długich (walcówki i drutów) do temperatury austenityzowania podczas dwuetapowej obróbki cieplnej, mającej zapewnić w materiale strukturę typu TRIP. Wykazano, że taki sposób nagrzewania wsadu do określonego przedziału temperatur z zakresu wyżarzania dwufazowego austenityczno-ferrytycznego zapewni odpowiednią ilość austenitu szczątkowego w strukturze materiału oraz równomierny rozkład własności mechanicznych na jego przekroju. Pozwoli to na skrócenie długości projektowanej linii technologicznej do obróbki cieplnej typu TRIP o ponad 50%.

EN

The work explores the possibility of using fast, resistance or induction heating, long blanks (wire rods and wires) up to the austenitizing temperature during two-stage heat treatment to provide TRIP type structure in the material. It has been shown that this method of heating the feedstock to a specific temperature range in the two-phase austenitic-ferritic annealing range will ensure the right amount of retained austenite in the material structure and uniform distribution of mechanical properties on its cross-section. This will shorten the length of the designed TRIP type heat treatment technological line by over 50%.

14

Fatigue life improvement on 20MnCr5 steel through surface modification for auto transmission application

Srinivasan Ramesh, Natarajan S., Sivakumar V. J.

Archives of Civil and Mechanical Engineering

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2019

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Vol. 19, no. 2

360--374

EN

This research represents a unique approach in improving the fatigue life of 20MnCr5 (89–91 HR15N hardness) shafts which were surface treated through gas carburizing process in a sealed quench furnace followed by double tempering. Crack initiation on 20MNCr5 transmission shafts always occurs at the end of spline location (Location X), propagates longitudinally and finally ruptures at stem location. This was confirmed through optical microscope and SEM (make:Jeol) images. The fatigue experiments were carried out at room temperature in 11,500 Nm torque test machine (Model – MTS-663-144-01). The torque test was carried-out by applying a fully reversed cyclic load with the frequency of 5 Hz for the torsional load of ±3000 Nm. Effect of double tempering, surface roughness, carbon case depth, Microstructure such as retained austenite and non-martensitic transformation products (NMTP) have been investigated in this research. The outcome of the research shows that increase in case depth (CD) (out of increased gas carburising time) resulting in increased inter-granular oxidation (IGO) and NMTP in its microstructure. The presence of retained austenite on the surface of the shaft has not yielded any remarkable improvement in fatigue life of the shaft. Presence of tempered martensite with lesser percentage of retained austenite on the surface improved the fatigue life drastically from 12,000 cycles to greater than 35,000 cycles at high torque load of ±3000 Nm.

15

Some aspects of the determination of retained austenite using the Rietveld refinement

Morawiec M.

Journal of Achievements in Materials and Manufacturing Engineering

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2017

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Vol. 80, nr 1

11--17

EN

Purpose: The aim of the paper is to show the advantage of the application of the Rietveld refinement for determination of retained austenite amount in multiphase microstructure steels. Design/methodology/approach: The steels used for the investigation were thermomechanically rolled and controlled cooled to room temperature. The investigation of the microstructure was carried out using light microscopy. X-ray diffraction investigations of analyzed steel were a major part of the research. The phase identification and quantitative analysis of retained austenite were done using the HighScore Plus software that includes the Rietveld refinement method. The Rietveld analysis takes into account the preferred orientation that occurs during thermo-mechanical processing of steel. Findings: It was found that after the thermo-mechanical processing the microstructure of steel is composed of fine-grained bainitic matrix which includes bainite-austenite constituents, martensite blocks and some fraction of retained austenite. The X-ray diffraction showed that this steel includes phases of Feα (bainite and martensite) and Feγ (retained austenite). The Rietveld analysis showed that the volume fraction of retained austenite is 14.1%. Research limitations/implications: To confirm that Rietveld refinement method is a good tool for the quantitative analysis of retained austenite volume fraction EBSD measurements should be done for comparison purposes. Practical implications: The obtained results can be used for determination of retained austenite fraction in AHSS steels. It is important because the retained austenite content and its mechanical stability decide about a formability level of these steel grades. Originality/value: Some methodological aspects are concerned affecting the final quantitative results of retained austenite volume fraction is AHSS.

16

Using the Principles of Image Analysis in the Assessment of the Proportion of Retained Austenite in the Case Hardened Layers

Váňová P., Sojka J., Kulová T., Jokešová K., Purtátor P., Spinu A.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 2A

577--580

EN

Structures of carburized layers after the surface saturation process in gaseous, liquid or solid medium and after subsequent heat treatment (hardening and low-temperature tempering) consist mainly of high carbon plate martensite with a certain portion of retained austenite. The presence of retained austenite (RA) in carburized layers is mostly considered as undesirable because it decreases hardness of the hardened layer and furthermore, a spontaneous conversion to a ferritic-carbide mixture of a bainitic type, accompanied by a change of properties, dimensional instability and the local increase in internal stress with the possible formation of cracks, can occur. The proportion of retained austenite is, therefore, a significant characteristics of the quality of hardened layers. This work deals with the evaluation of the volume fraction of retained austenite in carburized layers using image analysis on metallographic images.

17

Microstructural Aspects of Bifocal Laser Welding of TRIP Steels

Grajcar A., Grzegorczyk B., Różański M., Stano S., Morawiec M.

Archives of Metallurgy and Materials

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2017

|

Vol. 62, iss. 2A

611--618

EN

This work is concerned with comparative tests involving single-spot and twin-spot laser welding of thermomechanically rolled TRIP steel. The welding tests were carried out using keyhole welding and a solid state laser. In the case of twin-spot laser beam welding, the power distribution of beams was 50%:50%. The changes in macro- and microstructures were investigated using light and scanning electron microscopy. Three main zones subjected to the tests included the fusion zone, the heat affected zone and the intercritical heat affected zone (transition zone between the base material and the HAZ). Special attention was paid to the effect of various thermal cycles on the microstructure of each zone and on martensite morphology. The tests involved hardness measurements carried out in order to investigate the effect of different microstructures on mechanical properties of welds.

18

Mechanical Properties of a Bainitic Steel Producible by Hot Rolling

Rana R., Chen S., Haldar A., Das S.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 4

2331--2338

EN

A carbide-free bainitic microstructure is suitable for achieving a combination of ultra high strength and high ductility. In this work, a steel containing nominally 0.34C-2Mn-1.5Si-1Cr (wt.%) was produced via industrial hot rolling and laboratory heat treatments. The austenitization (900°C, 30 min.) and austempering (300-400°C, 3 h) treatments were done in salt bath furnaces. The austempering treatments were designed to approximately simulate the coiling step, following hot rolling and run-out-table cooling, when the bainitic transformation would take place and certain amount of austenite would be stabilized due to suppression of carbide precipitation. The microstructures and various mechanical properties (tensile properties, bendability, flangeability, and room and subzero temperature impact toughness) relevant for applications were characterized. It was found that the mechanical properties were highly dependent on the stability of the retained austenite, presence of martensite in the microstructure and the size of the microstructural constituents. The highest amount of retained austenite (~ 27 wt.%) was obtained in the sample austempered at 375°C but due to lower austenite stability and coarser overall microstructure, the sample exhibited lower tensile ductility, bendability, flangeability and impact toughness. The sample austempered at 400°C also showed poor properties due to the presence of initial martensite and coarse microstructure. The best combination of mechanical properties was achieved for the samples austempered at 325-350°C with a lower amount of retained austenite but with the highest mechanical stability.

19

Crack resistance of tool steels corresponding with the chemical composition of their matrices

Pacyna J.

Archives of Materials Science and Engineering

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2017

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Vol. 86, nr 1

5--14

EN

Purpose: of the presented investigations was showing that the crack resistance of tool steels depends on their hardenability and phase transformations occurring in the quenched matrix at tempering. The chemical composition of austenite decides on the steel hardenability while phase transformations after tempering can be influenced (apart from the chemical composition) by the heating method. Design/methodology/approach: of investigations was based on the analysis of dilatograms and the achieved aim was to obtain the hard tool steel (app. 500 HV30) for hot works. Samples of a diameter of 10 mm (without a notch) made of this steel were not broken by the Charpy impact test of energy of 30 kGm. Findings: of these investigations are practical. Grain boundaries of prior austenite should be protected against secondary precipitates, which constitute natural nuclei of diffusive structures. It is also possible to control phase transformations at tempering. Research limitations/implications: constitute the availability of the adequate equipment for investigating the kinetics of phase transformations of undercooled austenite and the kinetics of phase transformations after tempering. Practical implications: for the industry are such that the proposed tool steels of a high crack resistance contain molybdenum and nickel. Thus, these steels are very expensive. Originality/value: of these investigations was confirmed in the industrial practice.

20

The effect of chemical composition on microstructure and properties of TRIP steels

Kučerová L., Bystrianský M.

Journal of Achievements in Materials and Manufacturing Engineering

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2016

|

Vol. 77, nr 1

5--12

EN

Purpose: Various alloying strategies can be used to produce advanced high strength steels and this work offers comparison of results achieved for four different low alloyed steels with 0.2-0.4 %C, 0.5-2 %Si, 0.6-1.5 %Mn, 0.03-0.06 %Nb and with 0.8-1.33 %Cr. Microstructures obtained by two methods of thermo-mechanical treatment were analysed for each steel and compared with theoretical predictions of TTT (time temperature transformation) diagrams calculated by JMatPro. Design/methodology/approach: Thermo-mechanical treatment of all steels was carried out at thermo-mechanical simulator. Resulting microstructures were analyses by the means of scanning electron microscopy, mechanical properties were measured by tensile test. Findings: It was found out that microstructures typical for TRIP (transformation induced plasticity) steels can be obtained easily for low carbon steels alloyed by silicon or aluminium-silicon and micro-alloyed by niobium. Chromium addition influenced austenite decomposition causing intensive pearlite formation in low carbon steel and predominantly martensitic microstructure in middle carbon steel. These microstructures were not in agreement with calculated TTT diagrams. Research limitations/implications: To obtain ferritic-bainitic microstructure with retained austenite typical for TRIP steels, chromium alloyed steels require substantial optimisation of processing parameters. This issue should be addressed in future work. Practical implications: JMatPro software is well equipped to calculate TTT diagrams for steels alloyed by manganese, silicon and niobium, however further chromium addition changed behaviour of the steel in a way that the software was not able to predict. Originality/value: Obtained results could be useful for consideration of chemical composition of low alloyed steels with respect to resulting microstructures and properties.