Formation of bainite below the M temperature: Kinetics and crystallography

Samanta, Santigopal; Biswas, P.; Giri, Sushil; Singh, Shiv Brat; Kundu, Saurabh

doi:10.1016/j.actamat.2015.12.027

Cited by 102 publications

(40 citation statements)

References 62 publications

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“…The M s was measured to be ≈350 °C and QT360 contained bainite and martensite because of incomplete bainite transformation, while QT400 consisted of bainite. The formation of bainite in QT240, QT280, and QT320 was attributed to the non‐isothermal transformation below M s that has been reported in the literature . As shown in red circle in Figure a, the bainite was observed to attach to the initial quenched martensite and this indicated that the quenched martensite promoted the formation of bainite, which is consistent with the existing research .…”

Section: Resultssupporting

confidence: 89%

Kinetics of Carbon Partitioning during Non‐Isothermal Treatment and Mechanical Properties of the First Industrial Coils of Hot Rolled Quenched and Partitioned Steel

Chen

Kang

et al. 2019

steel research int.

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In this study, an energy-efficient processing route involving hot rolling, direct quenching, and air cooling partitioning (DQ&P) is proposed for the large-scale industrial production. The carbon partitioning is completed through waste heat of the steel coils. The effect of quenching temperature (QT) and the kinetics of non-isothermal carbon partitioning were investigated in a low carbon steel 0.19C-1.5Si-1.6Mn (wt%). A stable volume fraction of retained austenite (RA) %11.1-13.5% is obtained in the QT range of %240-360 C, which provides a wide quenching window for industrial production. In addition, when the QT was 320 C, the carbon partitioning was adequate at cooing rate of less than 1 C s À1 and the volume fraction of RA was more than 11%. When the cooling rate is increased to 5 and 10 C s À1 , %10% RA with high carbon content of %1.3 wt% is interestingly obtained. A large scale industrial coils of hot Q&P (Quenched and Partitioned) steel is successfully produced using a commercial steel 0.13C-1.2Si-1.5Mn-0.25Cr (wt%). The mechanical properties are uniform for the entire steel coil with tensile strength of %1258-1319 MPa and total elongation of %13.7-16%. The present work confirms the viability to introduce Q&P process in the hot rolling production line.

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Section: Resultssupporting

confidence: 89%

Kinetics of Carbon Partitioning during Non‐Isothermal Treatment and Mechanical Properties of the First Industrial Coils of Hot Rolled Quenched and Partitioned Steel

Chen

Kang

et al. 2019

steel research int.

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“…The CCT curve in Figure b illustrates that the bainitic transformation cannot occur during the cooling process due to the rapid cooling rate of 30 °C s −1 . However, there is a large amount of bainite in the final microstructure shown in Figure c and d. Also, the calculated thermodynamic results in ref . manifest that bainitic transformation can occur even if the isothermal temperature is lower than M S .…”

Section: Resultsmentioning

confidence: 76%

Refined Bainite Microstructure and Mechanical Properties of a High‐Strength Low‐Carbon Bainitic Steel Treated by Austempering Below and Above M_S

Tian

Zhou

et al. 2018

steel research int.

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Four isothermal heat treatment schedules are designed to study the effects of transformation temperature below and above martensite starting temperature (M S ) on bainitic transformation kinetics, microstructure, and mechanical properties of a low-carbon bainitic steel. The results indicate that the product of tensile strength and elongation (PSE) of tested steel do not show any improvement when the samples are austempered at a temperature below M S . Finer bainite microstructure can be observed when the samples are austempered at a temperature below M S , but the highest PSE is obtained in the sample austempered at a temperature above M S (400 C). Lower PSE of the samples transformed below M S is mainly attributed to less bainite and retained austenite (RA) amount and more amount of athermal martensite, as well as the existence of carbide. In addition, with the decrease of the isothermal transformation temperature, the PSE first increases and then decreases. Different from austempering above M S , when the sample is austempered below M S , PSE decreases with the decrease of transformation temperature. Moreover, whether the treatment below M S can improve mechanical property of bainitic steels depends on the composition of steels and transformation temperature.

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“…It can be used to calculate not only the starting temperatures of bainite and martensite based on the thermodynamic calculation, but also the driving force for diffusionless transformation, T-zero carbon concentration and the time-transformationtemperature (TTT) diagram. 24…”

Section: Methodsmentioning

confidence: 99%

Transformation Behavior of Bainite during Two-step Isothermal Process in an Ultrafine Bainite Steel

Tian

Jiang

et al. 2018

ISIJ International

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Formation of bainite below the M temperature: Kinetics and crystallography

Cited by 102 publications

References 62 publications

Kinetics of Carbon Partitioning during Non‐Isothermal Treatment and Mechanical Properties of the First Industrial Coils of Hot Rolled Quenched and Partitioned Steel

Kinetics of Carbon Partitioning during Non‐Isothermal Treatment and Mechanical Properties of the First Industrial Coils of Hot Rolled Quenched and Partitioned Steel

Refined Bainite Microstructure and Mechanical Properties of a High‐Strength Low‐Carbon Bainitic Steel Treated by Austempering Below and Above M_S

Transformation Behavior of Bainite during Two-step Isothermal Process in an Ultrafine Bainite Steel

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Formation of bainite below the M temperature: Kinetics and crystallography

Cited by 102 publications

References 62 publications

Kinetics of Carbon Partitioning during Non‐Isothermal Treatment and Mechanical Properties of the First Industrial Coils of Hot Rolled Quenched and Partitioned Steel

Kinetics of Carbon Partitioning during Non‐Isothermal Treatment and Mechanical Properties of the First Industrial Coils of Hot Rolled Quenched and Partitioned Steel

Refined Bainite Microstructure and Mechanical Properties of a High‐Strength Low‐Carbon Bainitic Steel Treated by Austempering Below and Above MS

Transformation Behavior of Bainite during Two-step Isothermal Process in an Ultrafine Bainite Steel

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Refined Bainite Microstructure and Mechanical Properties of a High‐Strength Low‐Carbon Bainitic Steel Treated by Austempering Below and Above M_S