Modeling kinetics of the austenite simultaneous decomposition into two bainitic products in the range of swing back

Woźniak, T. Z.

doi:10.1016/j.msea.2005.08.148

Cited by 10 publications

(14 citation statements)

References 25 publications

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“…In the regions where the carbon concentration is higher, midribs can form if the conditions determined by Oka and Okamoto are met [11]. As a result, a growth in the transformation rate of bainite occurs due to formation of the martensite plates of a midrib morphology [11,13,30,36].…”

Section: Acoustic Emission Induced By the Evolution Of Midribs And Camentioning

confidence: 97%

“…The studies suggest that each type of transformation product, as well as isothermal martensite [20,21], has a separate C-curve. There is an extensive evidence about the 'Swing Back' phenomenon [11,13,30]. It is a distinct austenite decomposition acceleration just near the M S below the nose of the bainitic transformation.…”

Section: Swing Back Phenomenon In the Remaining Austenite Transformationmentioning

confidence: 99%

“…Midrib formation is also related to the swing back effect in the bainitic transformation kinetics. Although the nature of the midrib is still not fully understood, it has been concluded that a midrib thin plate is the first area of bainite sheaves [11][12][13][14]. The mechanism of bainite formation has been the subject of numerous original research papers and reviews.…”

Section: Introductionmentioning

confidence: 99%

“…Implementation of new heat treatment schemes that are based on martensitic and bainitic transformations requires a strict control of processed elements in order to provide high quality steel. The suggested treatment method is based on phenomena that occur in high-carbon steels at the temperature near the M S which is typical of so-called 'swing back in kinetics' [11,13]. The present invention relates to new control methods of heat treatment for bearing steel components.…”

Section: Introductionmentioning

confidence: 99%

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Application of acoustic emission to monitor bainitic and martensitic transformation

Woźniak¹,

Rożniatowski²,

Ranachowski³

2011

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The paper concerns acoustic emission (AE) measurements during isothermal martensitic and bainitic heat treatments in 100CrMnSi6-4 bearing steel. A distribution of the total RMS voltage in arbitrary unit (AU) during austempering together with the MS temperature results was determined. MS represents the temperature at which martensite starts being formed. This temperature was determined with the use of the dilatometric method. The Short Time Fourier Transform algorithm was used for displaying the signal values on spectrogram graphs. AE signals were attributed to a midrib. Midrib is a thin-plate isothermal martensite formed before lower bainite nucleation. The evolution of midribs in remaining austenite was investigated with AE measurements at the temperature near MS. Macroscopic effects of elongation changes and their division into various intensity stages related to a martensite transformation were analyzed. A comparison of the AE curves and dilatometric results suggests that the AE method determines a relatively initial stage of the martensite transformation, during which additional processes of austempering and carbon partitioning occur. Lower bainite containing the midrib was found to evolve in two stages. K e y w o r d s : bearing steels, phase transformation kinetics, acoustic methods, isothermal heat treatments, midrib, bainite

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Section: Acoustic Emission Induced By the Evolution Of Midribs And Camentioning

confidence: 97%

Section: Swing Back Phenomenon In the Remaining Austenite Transformationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Application of acoustic emission to monitor bainitic and martensitic transformation

Woźniak¹,

Rożniatowski²,

Ranachowski³

2011

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“…This process requires both cooling austenite below the temperature when the martensitic transformation starts and enriching the unchanged austenite into carbon. Then the austenite is transformed into lower-bainite, similarly to the "swing back" effect [2][3][4][5][6][7][8]. The phenomenon shows clear rapid austenite decomposition near M S temperature.…”

Section: Introductionmentioning

confidence: 99%

The Application of Neural Networks for Studying Phase Transformation by the Method of Acoustic Emission in Bearing Steel/ Zastosowanie Sieci Neuronowych Do Badania Przemian Fazowych W Stali Łożyskowej Metodą Emisji Akustycznej

Woźniak¹,

Ranachowski²,

Ranachowski³

et al. 2014

Archives of Metallurgy and Materials

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The research was carried out on steel l00CrMnSi6-4 under isothermal austempering resulting in forming the duplex structure: martensitic and bainitic. The kinetics of transformation was controlled by the acoustic emission method. Complex phase transformations caused by segregation and carbide banding occur at the low-temperature heat treatment of bearing steel. At the temperature close to M S , a certain temperature range occurs where an effect of the first product of prior athermal martensite on the bainitic transformation can be observed. In the registered signal about 15 million various events were registered. There were considered three types of acoustic emission events (of high, medium and low energy), with relatively wide sections and with different spectral characteristics. It was found that the method of acoustic emission complemented by the application of neural networks is a sensitive tool to identify the kinetics of bainitic transformation and to show the interaction between martensitic and bainitic transformations.Keywords: Bearing steel, austempering, lower bainite, acoustic emission, neural networks Badania realizowano na stali l00CrMnSi6-4 poddanej hartowaniu izotermicznemu, prowadzącemu do utworzenia struktury duplex: martenzytyczno-bainitycznej. Kinetykę przemian kontrolowano metodą emisji akustycznej. Przy niskotemperaturowej obróbce cieplnej stali łożyskowej występują złożone przemiany fazowe spowodowane segregacją i pasmowością węglików. W temperaturze zbliżonej do M S , występuje pewien zakres temperatury, gdzie zaznacza się oddziaływanie wcześniejszego produktu przemiany martenzytycznej na przemianę bainityczną. W zarejestrowanym sygnale zarejestrowano około 15 milionów różnych zdarzeń. Uwzględniono trzy rodzaje zdarzeń emisji akustycznej (o wysokiej, średniej i niskiej energii) o względnie szerokich przedziałach, o różnej charakterystyce widmowej. Stwierdzono, że metoda emisji akustycznej uzupełniona o zastosowanie sieci neuronowych jest czułym narzędziem do identyfikacji kinetyki przemiany bainitycznej oraz oddziaływania przemiany martenzytycznej na przemianę bainityczną.

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Accelerated Isothermal Phase Transformation and Enhanced Mechanical Properties of Railway Wheel Steel: The Significant Role of Pre‐Existing Bainite

Gao

Tan

Tian

et al. 2021

steel research int.

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Exploring possible ways to accelerate bainite transformation kinetics and enhance mechanical properties, especially for large‐scale parts, attracted much attention both in industrial manufacturing and fundamental research. Herein, prior continuous cooling transformed bainite is introduced to promote isothermal transformation and improve strength toughness matching of bainite railway wheel steel. Phase transformation study by dilatometer indicates that the time–temperature–transformation curves of tested steel swing back at lower isothermal temperature. This acceleration effect is due to the formation of leaf‐shaped bainite at initial isothermal transformation stage. By tailoring the cooling rate, leaf‐shaped bainite can also be obtained during continuous cooling. It is confirmed that the formation of leaf‐shaped bainite during continuous cooling stage accelerates the subsequently isothermal bainite transformation. In situ microstructure evolution observation demonstrates that prior bainite/ austenite interface provides favorable nucleation site for initial isothermal bainite transformation. Moreover, pre‐existing bainite formed during continuous cooling stage can effectively divide the original austenite grain size. Concurrent enhancement of tensile strength and impact toughness in bainite wheel steel can be achieved by controlling the cooling rate.

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Modeling kinetics of the austenite simultaneous decomposition into two bainitic products in the range of swing back

Cited by 10 publications

References 25 publications

Application of acoustic emission to monitor bainitic and martensitic transformation

Application of acoustic emission to monitor bainitic and martensitic transformation

The Application of Neural Networks for Studying Phase Transformation by the Method of Acoustic Emission in Bearing Steel/ Zastosowanie Sieci Neuronowych Do Badania Przemian Fazowych W Stali Łożyskowej Metodą Emisji Akustycznej

Accelerated Isothermal Phase Transformation and Enhanced Mechanical Properties of Railway Wheel Steel: The Significant Role of Pre‐Existing Bainite

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