Effect of reheat temperature on continuous cooling bainite transformation behavior in low carbon microalloyed steel

Lan, Liangyun; Qiu, Chunlin; Zhao, Dewen; Gao, Xiuhua; Du, Linxiu

doi:10.1007/s10853-013-7251-7

Cited by 30 publications

(18 citation statements)

References 26 publications

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“…On the basis of the dilatation curves (some typical examples were given in the literature [11,13]), the transformation start/finish temperatures could be confirmed with a normal extrapolation method [15]. The CCT diagrams for CGHAZ and FGHAZ are constructed together in Figure 2a.…”

Section: Resultsmentioning

confidence: 81%

“…The effect of prior austenite grain size on bainite transformation is also of significance, although the related results seem to be in dispute [6][7][8][9][10][11]. Some studies considered that fine austenite grains accelerate the kinetics of bainite transformation, as the increase in the number of grain boundaries provides more preferable sites for nucleation of ferritic laths.…”

Section: Introductionmentioning

confidence: 99%

“…The bainite start transformation (Bs) temperature is found to be lowered with decreasing austenite grain size under the continuous cooling condition, a very similar trend to that found with the Ms temperature. It is taken for granted that they have a similar mechanism for the decrease in transformation temperature [10,11]. However, it should be noted that the martensite transformation is an athermal transformation, whereas the bainite transformation is, sometimes, regarded as a kind of thermally activated nucleation and growth reaction-it does not seem very convincing that the Hall-Petch strengthening effect in fine austenite grains is considered as a sole factor to decrease the Bs temperature.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Exploring the Difference in Bainite Transformation with Varying the Prior Austenite Grain Size in Low Carbon Steel

Lan

Zhou

Fan

2018

Metals

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The simulation welding thermal cycle technique was employed to generate different sizes of prior austenite grains. Dilatometry tests, in situ laser scanning confocal microscopy, and transmission electron microscopy were used to investigate the role of prior austenite grain size on bainite transformation in low carbon steel. The bainite start transformation (Bs) temperature was reduced by fine austenite grains (lowered by about 30 °C under the experimental conditions). Through careful microstructural observation, it can be found that, besides the Hall–Petch strengthening effect, the carbon segregation at the fine austenite grain boundaries is probably another factor that decreases the Bs temperature as a result of the increase in interfacial energy of nucleation. At the early stage of the transformation, the bainite laths nucleate near to the grain boundaries and grow in a “side-by-side” mode in fine austenite grains, whereas in coarse austenite grains, the sympathetic nucleation at the broad side of the pre-existing laths causes the distribution of bainitic ferrite packets to be interlocked.

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Section: Resultsmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Exploring the Difference in Bainite Transformation with Varying the Prior Austenite Grain Size in Low Carbon Steel

Lan

Zhou

Fan

2018

Metals

Self Cite

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“…Thus, the selection of appropriate heat treatment parameters based on the austenitization process is the only way to obtain the expected microstructure [9,10]. However, because the kinetics of austenitization has not attracted significant attention, there is minimal information regarding the kinetics of austenite transformation for cases other than the decomposition of austenite [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Kinetics of the austenitization in the Fe-Mo-C ternary alloys during continuous heating

Kong

Liu

et al. 2016

Open Physics

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Abstract:The influence of molybdenum on the microstructure and kinetics of the austenization of the Fe-Mo-C ternary alloys is analyzed using differential scanning calorimetry (DSC) and the Johnson-Mehl-AvramiKolmogorov model (JMAK) in the temperature range from 293 K to 1373 K. The as-cast microstructure and microstructure after DSC test are obtained using optical microscopy (OM) and scanning electron microscopy (SEM). It was seen that with an increasing Mo concentration, the lamellar pearlite is spherized and the austenite grain size decreases. In addition, both DSC curves and the JMAK model show that the initial (Ac1) and the final (Ac3) temperature of the phase transition increases with an increasing Mo concentration. It was also seen that increasing the Mo concentration, the diffusion activation energy (DAE) increases and the pre-exponential factor of diffusion (DPEF) decreases due to a change in both the austenitic nucleation rate and the diffusion of the elements caused by the introduction of Mo.

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“…Recently researches showed that the coarse grain HAZ (CGHAZ) adjacent to the fusion line always has the lowest toughness in single pass welding because of the formation of some unfavorable microstructures such as large-size prior-austenite grains and M-A constituents [3,4]. The decrease in toughness arising from the asymmetrical microstructure was also reported in ICHAZ where the transformation of ferrite to austenite occurs particularly [5].…”

Section: Introductionmentioning

confidence: 99%

Microstructure and Mechanical Properties of Intercritical Heat-affected Zone of X80 Pipeline Steel in Simulated In-Service Welding

Cai

Xing

et al. 2015

Acta Metall. Sin. (Engl. Lett.)

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The intercritical heat-affected zone (ICHAZ) of X80 pipeline steel was simulated by using the Gleeble-3500 thermal/mechanical simulator according to the thermal cycle of in-service welding. The microstructures of ICHAZ with different cooling rates were examined, and the hardness, the toughness and corresponding fractography were investigated. Results show that untransformed bainite and ferrite as well as retransformed fine bainite and martensite-austenite (M-A) constituents constitute the microstructure of ICHAZ. The two different morphologies of M-A constituents are stringer and block. Second phase particles which mainly composed of Ti, Nb, C, Fe and Cu coarsened in ICHAZ. Compared with normal welding condition, the toughness of ICHAZ is poor when the cooling time is short under in-service welding condition because of the large area fraction and size of M-A constituents that connect into chains and distribute at the grain boundaries. The Vickers hardness of ICHAZ that decreases with the increase in the cooling time is independent with the area fraction of M-A constituents.

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Effect of reheat temperature on continuous cooling bainite transformation behavior in low carbon microalloyed steel

Cited by 30 publications

References 26 publications

Exploring the Difference in Bainite Transformation with Varying the Prior Austenite Grain Size in Low Carbon Steel

Exploring the Difference in Bainite Transformation with Varying the Prior Austenite Grain Size in Low Carbon Steel

Kinetics of the austenitization in the Fe-Mo-C ternary alloys during continuous heating

Microstructure and Mechanical Properties of Intercritical Heat-affected Zone of X80 Pipeline Steel in Simulated In-Service Welding

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