Continuous cooling transformation behaviour and bainite formation kinetics of new bainitic steel

Zheng, Y. F.; Wu, Riming; Li, X.-C.; Wu, Xiao Chun

doi:10.1080/02670836.2016.1224608

Cited by 15 publications

(13 citation statements)

References 40 publications

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“…However, as the cooling rate was more than 0.08 °C/s, the volume fraction of RA in the carburised layer is higher than that of matrix. The bainite transformation Kinetics under non-isothermal conditions has been modeled by the modified Johnson-Mehl-Avrami (JMA) equation, which is expressed as follows [24][25][26],…”

Section: Discussionmentioning

confidence: 99%

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Continuous Cooling Transformation Behaviour and Bainite Transformation Kinetics of 23CrNi3Mo Carburised Steel

Song

Lei

Wan

et al. 2020

Metals

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In this study, the phase transformation behaviour of the carburised layer and the matrix of 23CrNi3Mo steel was comparatively investigated by constructing continuous cooling transformation (CCT) diagram, determining the volume fraction of retained austenite (RA) and plotting dilatometric curves. The results indicated that Austenite formation start temperature (Ac1) and Austenite formation finish temperature (Ac3) of the carburised layer decreased compared to the matrix, and the critical cooling rate (0.05 °C/s) of martensite transformation is significantly lower than that (0.8 °C/s) of the matrix. The main products of phase transformation in both the carburised layer and the matrix were martensite and bainite microstructures. Moreover, an increase in carbon content resulted in the formation of lamellar martensite in the carburised layer, whereas the martensite in the matrix was still lath. Furthermore, the volume fraction of RA in the carburised layer was higher than that in the matrix. Moreover, the bainite transformation kinetics of the 23CrNi3Mo steel matrix during the continuous cooling process indicated that the mian mechanism of bainite transformation of the 23CrNi3Mo steel matrix is two-dimensional growth and one-dimensional growth.

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Section: Discussionmentioning

confidence: 99%

“…During continuous cooling, the particular activation energy for each transformed volume fraction (f b ) may inconsistent, this is different from isothermal process. The activation energy corresponding to a fixed f b was used to describe the variable activation energy, calculated by a Kissinger analysis [23,24],…”

Section: Kinetics Of Matrix Bainite Transformationmentioning

confidence: 99%

Continuous Cooling Transformation Behaviour and Bainite Transformation Kinetics of 23CrNi3Mo Carburised Steel

Song

Lei

Wan

et al. 2020

Metals

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“…Ef as a function on the volume fraction of transformed phase f was calculated using Equation (3) from [ 8 , 10 , 11 , 12 , 13 ]:

where T f is the temperature corresponding to the volume fraction of transformed phase f , and C is a constant, which is determined in [ 21 ] as

, where

is a state variable.…”

Section: Resultsmentioning

confidence: 99%

Kinetics of Austenite Decomposition in 54SiCr6 Steel during Continuous Slow Cooling Conditions

et al. 2023

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In this study, dilatometry and metallography were used to investigate the effect of silicon and copper alloying on the decomposition kinetics of 54SiCr6 steel during continuous slow cooling. It is different from the published literature for using the approach of the local activation energy of the austenite decomposition Ef and the local Avrami exponent n of the volume fraction of the transformed phase f to study the kinetics of austenite-pearlitic transformation in cooled 54SiCr steel at slow cooling rates. The Johnson–Mehl–Avrami equation was used to determine the dependence of the local activation energy for austenite decomposition Ef and the local Avrami exponent n on the volume fraction of the transformed phase f. The mechanism of the austenite decomposition was analysed based on the calculated values of n. Both the local and average activation energies were used to evaluate the alloying effect, and the results were compared with those obtained from other methods. The type of microstructure formed as a result of cooling at rates of 0.5 K/s, 0.3 K/s, 0.1 K/s and 0.05 K/s was determined. The effects of changes in the cooling rate and the content of silicon (1.5–2.5 wt.%) and copper (0.12–1.47 wt.%) on the dimension of nucleation and growth kinetics of the transformed phase were studied. It was revealed that the pearlite microstructure was formed predominantly in 54SiCr6 steel as a result of continuous cooling at slow cooling rates. It was also found that alloying this steel with copper led to a significant decrease in the value of Ef, as well as to a change in the mechanism of the kinetics of the austenite-pearlite transformation, which was realised in predominantly two- and three-dimensional nucleation and growth at a constant nucleation rate. At the same time, alloying this steel with silicon led only to a slight change in Ef. The results of the study of 54SiCr steel presented the dependence of the activation energy of transformation and the local Avrami exponent on the volume fraction of the transformed phase at a given cooling rate at different copper and silicon contents. In addition, the study provides insight into the mechanism of kinetics in cooled 54SiCr steel as a function of the cooling rate.

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“…During the fabrication of large plastic mould steel blooms, the low impact toughness of the product is a major quality issue. Through microstructural analysis, this phenomenon is attributed to the coarse grain and nonuniform grain size [1][2][3]. As the most important manufacturing process for plastic mould steel, microstructural control in free forging processes determines product quality.…”

Section: Introductionmentioning

confidence: 99%

Microstructural Evolution in Large-Section Plastic Mould Steel during Multi-Directional Forging

Chen

et al. 2022

Metals

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To obtain excellent mechanical properties from large cross-sections of plastic mould steel (SDP1), we conducted multi-directional forging (MDF) to control the microstructure of ingots. To investigate the microstructural evolution of SDP1 steel during MDF, we performed hot forging at 1150 °C using a THP01–500A hydraulic press. The dimensions of the specimens were Φ38 mm × 80 mm. The microstructure of the specimens after forging was observed under a metallographic microscope. Furthermore, the results of the finite element method (FEM) simulations were employed to improve the quality of the forgings. The predicted results agreed well with the experimental ones, indicating that FEM is effective for analysing microstructural evolution during MDF. Thus, MDF for large cross-sections of SDP1 steel (Φ1000 mm × 2200 mm) was simulated. The results showed that the average grain size of SDP1 steel at the core of an ingot after MDF ranged from 40.6 to 43.3 μm. Although this was slightly higher than the grain size of the sample after traditional upsetting and stretching forging (TUSF) (35.7–46.0 μm), the microstructure of the SDP1 steel sample after MDF was more uniform than that after TUSF. Compared with TUSF, MDF not only refines the grain size but also improves the microstructure uniformity of the sample.

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Continuous cooling transformation behaviour and bainite formation kinetics of new bainitic steel

Cited by 15 publications

References 40 publications

Continuous Cooling Transformation Behaviour and Bainite Transformation Kinetics of 23CrNi3Mo Carburised Steel

Continuous Cooling Transformation Behaviour and Bainite Transformation Kinetics of 23CrNi3Mo Carburised Steel

Kinetics of Austenite Decomposition in 54SiCr6 Steel during Continuous Slow Cooling Conditions

Microstructural Evolution in Large-Section Plastic Mould Steel during Multi-Directional Forging

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