scholarly journals Continuous Cooling Transformation Kinetics of Steels

1982 ◽  
Vol 68 (3) ◽  
pp. 383-392 ◽  
Author(s):  
Minoru UMEMOTO ◽  
Imao TAMURA
Keyword(s):  
Transformation Kinetics ◽  
Continuous Cooling Transformation ◽  
Continuous Cooling ◽  
Kinetics Of

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

Metals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 48
Author(s):  
Wenjun Song ◽  
Min Lei ◽  
Mingpan Wan ◽  
Chaowen Huang
Keyword(s):  
Phase Transformation ◽  
Volume Fraction ◽  
Austenite Formation ◽  
Steel Matrix ◽  
Transformation Kinetics ◽  
Bainite Transformation ◽  
Continuous Cooling ◽  
The Matrix ◽  
Dimensional Growth ◽  
Kinetics Of

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.

Effect of boron on the continuous cooling transformation kinetics in a low carbon advanced ultra-high strength steel (A-UHSS)

2012 ◽  
Vol 1485 ◽  
pp. 83-88 ◽  
Author(s):  
G. Altamirano ◽  
I. Mejía ◽  
A. Hernández-Expósito ◽  
J. M. Cabrera
Keyword(s):  
Research Work ◽  
High Strength Steels ◽  
High Strength ◽  
Microstructural Characterization ◽  
Low Carbon ◽  
Transformation Kinetics ◽  
Cooling Rates ◽  
Continuous Cooling Transformation ◽  
Continuous Cooling ◽  
Cct Diagrams

ABSTRACTThe aim of the present research work is to investigate the influence of B addition on the phase transformation kinetics under continuous cooling conditions. In order to perform this study, the behavior of two low carbon advanced ultra-high strength steels (A-UHSS) is analyzed during dilatometry tests over the cooling rate range of 0.1-200°C/s. The start and finish points of the austenite transformation are identified from the dilatation curves and then the continuous cooling transformation (CCT) diagrams are constructed. These diagrams are verified by microstructural characterization and Vickers micro-hardness. In general, results revealed that for slower cooling rates (0.1-0.5 °C/s) the present phases are mainly ferritic-pearlitic (F+P) structures. By contrast, a mixture of bainitic-martensitic structures predominates at higher cooling rates (50-200°C/s). On the other hand, CCT diagrams show that B addition delays the decomposition kinetics of austenite to ferrite, thereby promoting the formation of bainitic-martensitic structures. In the case of B microalloyed steel, the CCT curve is displaced to the right, increasing the hardenability. These results are associated with the ability of B atoms to segregate towards austenitic grain boundaries, which reduce the preferential sites for nucleation and development of F+P structures.

Transformation Kinetics of Bainite during Isothermal Holding and Continuous Cooling

1982 ◽  
Vol 68 (3) ◽  
pp. 461-470 ◽  
Author(s):  
Minoru UMEMOTO ◽  
Kazunari HORIUCHI ◽  
Imao TAMURA
Keyword(s):  
Isothermal Holding ◽  
Transformation Kinetics ◽  
Continuous Cooling ◽  
Kinetics Of

scholarly journals Dilatometric Analysis of the Austenite Decomposition in Undeformed and Deformed Low-Carbon Structural Steel

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5443
Author(s):  
Mateusz Morawiec ◽  
Adam Skowronek ◽  
Mariusz Król ◽  
Adam Grajcar
Keyword(s):  
Phase Transformation ◽  
Structural Steel ◽  
Transformation Product ◽  
Low Carbon ◽  
Transformation Kinetics ◽  
Continuous Cooling Transformation ◽  
Continuous Cooling ◽  
Phase Transformation Kinetics ◽  
Microscopic Studies ◽  
Carbon Structural Steel

This paper aims to analyze the effect of deformation on the phase transformation kinetics of low-carbon structural steel. The steel used for the investigation was subjected to two different dilatometric analyses using a DIL 805A/D device. The first analysis was to determine the phase transformation kinetics without deformation of austenite before cooling. Then, the analysis under deformation conditions was conducted to investigate the deformation effect on the transformation kinetics. Microscopic studies by light microscopy were performed. The essential part of the research was hardness analysis for different cooling rates and the creation of continuous-cooling-transformation (CCT) and deformation continuous-cooling-transformation (DCCT) diagrams. It was found that the deformation of the samples before cooling increases a diffusion rate in the austenite resulting in the corresponding increase of ferritic, pearlitic, and bainitic start temperatures, as well as shifting the austenite transformation product regions to a longer time. The increase of the transformation area and a decrease in grain size are observed for the deformed samples.

Influence of the Chemical Composition on the Ausferritic Transformation in Carbide-Free Bainitic Cast Steel

2014 ◽  
Vol 793 ◽  
pp. 85-91
Author(s):  
Alejandro D. Basso ◽  
Nicolás E. Tenaglia ◽  
Roberto Enrique Boeri ◽  
Juan M. Massone
Keyword(s):  
Chemical Composition ◽  
Cast Steel ◽  
Isothermal Transformation ◽  
The Other ◽  
Chemical Compositions ◽  
Transformation Kinetics ◽  
Continuous Cooling ◽  
Cast Steels ◽  
High Silicon ◽  
Kinetics Of

This work focuses on the study of the solid state transformations that take place during the austempering of high silicon carbide-free bainitic cast steels with different chemical composition. In order to get this objective three cast steel melts with different chemical compositions were produced, evaluating the influence of Cr, Mn, Ni, Al and Co. For each of these steels, samples were subjected to an austempering heat treatment at 340 oC varying the austempering time from 5 sec to 120 sec. The results show that small regions of free ferrite were obtained during continuous cooling from the austenitising to the austempering temperatures in unalloyed high silicon cast steels. At short austempering time (5 sec), the presence of a small fraction of ausferrite was observed. Austempering for 60 sec showed a larger amount of ausferrite. However, the ausferritic reaction is incomplete, and some martensite also was present, mainly located in last to freeze (LTF) zones. After an austempering of 120 sec, a fully ausferritic matrix was obtained. The addition of Cr and Mo avoided the initial precipitation of free ferrite, and lowered the isothermal transformation kinetics. On the other hand the use of Al and Co increase the presence of ferrite formed during continuous cooling and accelerates the kinetics of the ausferritic reaction.

Modelling the Transformations Kinetics from Work-Hardened Austenite in a TRIP Steel

2007 ◽  
Vol 539-543 ◽  
pp. 4339-4344
Author(s):  
F. Fazeli ◽  
Matthias Militzer
Keyword(s):  
Experimental Study ◽  
Trip Steel ◽  
Mixed Mode ◽  
Integrated Model ◽  
Transformation Model ◽  
Transformation Kinetics ◽  
Continuous Cooling Transformation ◽  
Cooling Path ◽  
Proposed Model ◽  
Kinetics Of

Using physical concepts, an integrated transformation model to describe the kinetics of ferrite and bainite formation from work-hardened austenite has been developed for a Mo-TRIP steel. The ferrite sub-model assumes a mixed-mode kinetics under paraequilibrium condition and accounts explicitly for the effect of alloying elements by considering their interaction with the moving ferrite-austenite interface. To predict the onset of bainite formation, which corresponds to the cessation of ferrite reaction along a given cooling path, a criterion based on a critical driving pressure is formulated. Regarding the kinetics of the subsequent bainite reaction, the proposed model adopts the Zener-Hillert diffusional approach. The proposed integrated model has been employed to describe the continuous cooling transformation kinetics for a 0.19C-1.5Mn-1.6Si- 0.2Mo (wt%) TRIP steel that had previously been subjected to a systematic experimental study. The predictive capabilities of the model and the challenges for further model improvements are delineated.

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