Acoustic phenomena near MS in hypereutectoid steels

Woźniak, T. Z.

doi:10.1016/j.matchar.2007.06.004

Cited by 8 publications

(13 citation statements)

References 22 publications

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“…T.Z. Wozniak proved in his earlier research [5,7] that acoustic effects during midrib formation are many times higher than during the formation of further bainite Shares. In recent years, D. H. Kim et al [38] have proved that there is a significant difference between isothermal transformation above temperature M S , i.e.…”

Section: Discussionmentioning

confidence: 99%

“…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%

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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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Section: Discussionmentioning

confidence: 99%

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

Self Cite

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“…The transformation measured by AE was delayed by about 2 s due to transportation of specimens. An acoustic sensor (5) was installed previously on one of the two movable mandrels (2, 3) serving as a waveguide and connected to an analyzer [9,10]. Signals were recorded by means of an AE analyzer 10/20 kHz -800 kHz.…”

Section: Experimental Setup and Measuring Proceduresmentioning

confidence: 99%

“…Both longitudinal and transverse elastic waves can be generated by an abrupt local force. A unified explanation of the AE source has not been provided yet, but it is usually considered as a process which involves plastic deformation (dislocation movement), crack growth, phase transformations (bainitic and martensitic) [4][5][6][7][8][9][10]. Strongly localized processes during the phase transition lead to the formation of significant shear and dilatation strains, which produce *Corresponding author: tel.…”

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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Analyses of Transformation Kinetics of Carbide-Free Bainite Above and Below the Athermal Martensite-Start Temperature

Yakubtsov

Purdy

2011

Metall Mater Trans A

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The isothermal transformation kinetics of austenite decomposition in Fe-0.4C-2.78Mn-1.81Si was analyzed by an electrical resistivity technique in the temperature interval 723 K to 418 K (450°C to 145°C). The analysis of transformation kinetics of the bainite transformation was performed using the Johnson-Mehl-Avrami-Kolgomorov (JMAK) and Austin-Rickett (AR) approaches. The kinetic parameters, the reaction constant n, rate constant k = k(T), and apparent activation energy Q were evaluated for isothermal transformations below and above the martensite-start temperature M S = 548 K (275°C), which was determined experimentally. The formation of strain-induced martensite, which starts to accompany the bainite transformation at just above M S , increases the rate of transformation and decreases the apparent activation energy of austenite decomposition.

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Acoustic phenomena near MS in hypereutectoid steels

Cited by 8 publications

References 22 publications

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

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

Application of acoustic emission to monitor bainitic and martensitic transformation

Analyses of Transformation Kinetics of Carbide-Free Bainite Above and Below the Athermal Martensite-Start Temperature

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