Non-isothermal Austenitisation Kinetics and Theoretical Determination of Intercritical Annealing Time for Dual-phase Steels.

Nath, S. K.; Ray, S.; Mathur, V. N. S.; Kapoor, M. L.

doi:10.2355/isijinternational.34.191

Cited by 22 publications

(18 citation statements)

References 2 publications

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“…Some investigators [16][17][18] use the modified version of JMA model (Eq. (1)) to calculate volume fraction of austenite at different times.…”

Section: )mentioning

confidence: 99%

“…[7][8][9][10][11][12][13][14][15] It was shown that formation austenite in dual phase steels is a diffusion-controlled growth 8,9) and some of researchers proposed that [16][17][18] the empirical equation of Johnson-Mehl-Avrami (JMA) with Kolmogorov modification (JMAK) can be used for austenite transformation during intercritical annealing. The modified version of JMA model is as follows 19,20) : where f g is austenite volume fraction, t is annealing time, n is Avrami's exponent and k is the rate constant.…”

Section: Introductionmentioning

confidence: 99%

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Kinetics of Austenite Formation in Dual Phase Steels

2008

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In this research study a low carbon steel with composition of Cϭ0.11 %; Mnϭ1.30 %; Crϭ0.45 %; Siϭ0.20 %; Alϭ0.03 % and Feϭbal. was cast and used in hot rolled condition. After intercritical annealing at different temperatures for different times, dual phase structures with various volume fraction of martensite were produced. Then the volume fraction of martensite for different samples were measured.Study of the relationship between temperature and time of intercritical annealing and martensite volume fraction showed that a new equation as f g /f e ϭ1Ϫexp(Ϫkt n ) can be used to give variation of martensite volume fraction with temperature and time of annealing. Also it is found that k coefficient changes exponentially with annealing temperature.

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“…Some investigators [16][17][18] use the modified version of JMA model (Eq. (1)) to calculate volume fraction of austenite at different times.…”

Section: )mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Kinetics of Austenite Formation in Dual Phase Steels

2008

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“…Alternatively, the JMAK approach has been applied to the isothermal austenitization kinetics and used to predict with some success for plain carbon steels intercritical annealing times for holding at the peak temperature. 147) A recent study by Caballero et al 148) indicates limitations of these approaches since the austenite formation from ferrite is in general non-additive. This observation is consistent with the work of Huang et al 133) on a DP600 steel (0.06wt%C-0.155wt%Mo-1.86wt%Mn) where it was not only demonstrated that the austenite formation kinetics is non-additive but that it can be further complicated by an overlap with ferrite recrystallization.…”

Section: Austenite Formationmentioning

confidence: 99%

Computer Simulation of Microstructure Evolution in Low Carbon Sheet Steels

Militzer

2007

ISIJ Int.

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Models of microstructure evolution in steels are reviewed. The emphasis of the review is on low carbon sheet steels both hot-rolled and cold-rolled and annealed. First the state-of-the-art on industrial microstructure process models is presented. The individual model concepts for grain growth, recrystallization, precipitation and phase transformations are briefly discussed. The development from empirically-based models to physically-based models is identified as a key issue to have increased predictive capabilities for these models over a wider range of steel grades and operational conditions. The challenges in the development of the next generation of models are delineated. In particular, new aspects of microstructure evolution associated with novel processing routes and advanced high strength steels are evaluated. Further, the majority of the currently employed models are on the macro-scale but future microstructure models will increasingly be meso-scale models that predict actual microstructures rather than a number of average parameters (e.g. grain size, fraction transformed) to describe microstructure evolution.KEY WORDS: mathematical model; microstructure; steel; hot rolling; annealing; grain growth; recrystallization; precipitation; phase transformation. © 2007 ISIJ Reviewvates the development of advanced microstructure models that provide an increased insight into the underlying physical metallurgy principles. Further, AHSS are frequently produced as cold-rolled annealed and/or coated sheets. Here, the intercritical annealing step assumes a crucial role to obtain the desired complex, multi-phase microstructures. Intercritical annealing constitutes a paradigm shift from annealing of conventional steels where no cycling through the transformation region occurs. The added complexity of the annealing routes for AHSS requires the development of novel annealing models that also address austenite formation which has received comparatively little attention in process models.Currently available microstructure models for the production of sheet and other steels are usually formulated on the macro-scale, i.e. the microstructure is described with a number of so-called internal state variables such as grain size, fraction recrystallized and fraction transformed. However, the advances in computer technology make it now feasible to routinely conduct modelling of the microstructure on the meso-scale if not on the atomistic level. In particular the meso-scale approach appears to open a new era of modelling the microstructure evolution in sheet steels. In this methodology actual microstructures can be predicted rather than mean values which have traditionally been used to characterize microstructures. The significance of these new modelling strategies is also fueled by the realization that material properties may markedly depend on morphology and spatial distributions of microstructure constituents. [22][23][24] In this paper, first the models proposed for hot strip rolling are reviewed. Special attention is given to the ...

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“…Such models have been developed to describe recrystallization [14][15][16][17] and austenite formation. [17][18][19][20] Models describing decomposition of intercritical annealing have received less attention as compared to decomposition from a fully austenitic state. [21][22][23][24][25] Several attempts have been made to couple these separate models to describe the entire microstructure evolution during intercritical annealing.…”

Section: Introductionmentioning

confidence: 99%

A Microstructure Evolution Model for Intercritical Annealing of a Low-carbon Dual-phase Steel

2014

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A model was developed to describe the microstructure evolution during intercritical annealing of a lowcarbon steel suitable for industrial production of DP600 grade dual-phase steel on a hot-dip galvanizing line. The microstructure evolution model consists of individual submodels for ferrite recrystallization, austenite formation and decomposition constructed using the Johnson-Mehl-Avrami-Kolmogorov approach and the additivity principle. The submodels for recrystallization and austenite formation are adopted from a previous study. The present paper provides a detailed analysis of the model development for the decomposition of intercritical austenite. The overall microstructure evolution model is validated using simulated industrial thermal paths for intercritical annealing. Model validation is expedited by in-situ measurements of the recrystallization completion temperature using laser ultrasonics and the intercritical austenite formation and decomposition using dilatometry.

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Non-isothermal Austenitisation Kinetics and Theoretical Determination of Intercritical Annealing Time for Dual-phase Steels.

Cited by 22 publications

References 2 publications

Kinetics of Austenite Formation in Dual Phase Steels

Kinetics of Austenite Formation in Dual Phase Steels

Computer Simulation of Microstructure Evolution in Low Carbon Sheet Steels

A Microstructure Evolution Model for Intercritical Annealing of a Low-carbon Dual-phase Steel

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