scholarly journals Dilatometric Study of Phase Transformations in 5 Mn Steel Subjected to Different Heat Treatments

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 958 ◽  
Author(s):  
Mateusz Morawiec ◽  
Adam Grajcar ◽  
Władysław Zalecki ◽  
Carlos Garcia-Mateo ◽  
Marek Opiela
Keyword(s):  
Room Temperature ◽  
Intercritical Annealing ◽  
Isothermal Holding ◽  
Heat Treatments ◽  
Medium Mn Steel ◽  
Annealing Step ◽  
Fresh Martensite ◽  
Evolution Of Microstructure ◽  
Hot Rolled ◽  
Mn Steel

The work presents results of phase transformation kinetics of hot-rolled 5% Mn steel subjected to different heat treatments. Three different schedules were introduced: isothermal holding in a bainite region, coiling simulation and intercritical annealing. The evolution of microstructure components was investigated using dilatometric and metallographic analyses. According to obtained results, the medium-Mn steel exhibits high resistance for γ/α transformation during the bainite transformation and coiling simulation (upon cooling from the austenite region). During 5 h isothermal holding, no bainite and/or ferrite formation was detected. This results in the formation of martensite upon cooling to room temperature. Differently, when the steel was subjected to the intercritical annealing at 720 and 700 °C (upon heating from room temperature), a final microstructure consisted of ferrite, martensite and retained austenite. At 700 °C, no fresh martensite formation was detected upon cooling to room temperature. This means that the austenite was enriched in carbon during the intercritical annealing step enough to keep its thermal stability.

scholarly journals Physical simulation and dilatometric study of double-step heat treatment of medium-Mn steel

2020 ◽  
Vol 20 (4) ◽  
Author(s):  
A. Skowronek ◽  
M. Morawiec ◽  
V. Ruiz-Jimenez ◽  
C. Garcia-Mateo ◽  
A. Grajcar
Keyword(s):  
Heat Treatment ◽  
Retained Austenite ◽  
Physical Simulation ◽  
Isothermal Holding ◽  
Heat Treatments ◽  
Double Step ◽  
Dilatometric Study ◽  
Medium Mn Steel ◽  
One Step ◽  
Mn Steel

Abstract The work addresses physical simulation and dilatometric study of one-step and double-step heat treatments of medium-Mn steel designed for automotive sheets. The conventional one-step isothermal bainitic transformation was applied as the reference heat treatment. The newly implemented heat treatment consisted of isothermal holding in a bainitic region followed by additional holding of the material at reduced temperature also in the bainitic range. This step was added to refine the microstructure, which led to the stabilization of the retained austenite. Calculations of equilibrium state and non-equilibrium cooling and simulations of the developed thermal cycles were performed using the thermodynamic JMatPro software. The physical simulations of the heat treatment were performed in the dilatometer. The obtained samples were subjected to microscopic observations using light and SEM microscopy. One- and two-step heat treatments allowed to obtain bainitic structures with high contents of retained austenite. Lowering the temperature of one-step isothermal holding resulted in the bainite refinement and adjacent retained austenite. The increased Mn content in steel increased its susceptibility to form coalesced bainite resulting in the partial formation of thicker plates despite a decrease in a process temperature.

Austenite/ferrite interface movement during intercritical annealing of a medium Mn steel

2021 ◽  
pp. 1-7
Author(s):  
M. K. Bai ◽  
D. P. Yang ◽  
G. D. Wang ◽  
J. H. Ryu ◽  
K. Y. Lee ◽  
...  
Keyword(s):  
Intercritical Annealing ◽  
Medium Mn Steel ◽  
Mn Steel ◽  
Interface Movement

On the intercritical annealing parameters and ensuing mechanical properties of low-carbon medium-Mn steel

2018 ◽  
Vol 733 ◽  
pp. 246-256 ◽  
Author(s):  
G.K. Bansal ◽  
D.A. Madhukar ◽  
A.K. Chandan ◽  
Ashok K. ◽  
G.K. Mandal ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Intercritical Annealing ◽  
Low Carbon ◽  
Medium Mn Steel ◽  
Mn Steel

scholarly journals Enhancing the Robustness and Efficiency in the Production of Medium Mn Steels by Al Addition

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1432
Author(s):  
Maokun Bai ◽  
Dapeng Yang ◽  
Guodong Wang ◽  
Joohyun Ryu ◽  
Kyooyoung Lee ◽  
...  
Keyword(s):  
Tensile Deformation ◽  
Intercritical Annealing ◽  
Industrial Process ◽  
Process Window ◽  
Continuous Annealing ◽  
Austenite Stability ◽  
Medium Mn Steel ◽  
Reverted Austenite ◽  
Cold Rolled ◽  
Mn Steel

The narrow process window during intercritical annealing and discontinuous yielding have limited the commercialization of medium Mn steels. In this study, a double-annealing process based on the commercial continuous annealing line is proposed. The cold-rolled medium Mn steels were first fully austenitized and quenched during the first annealing, followed by intercritical annealing for reverted austenite transformation. The microstructure of duplex lath-shaped austenite and ferrite is produced and steel exhibits a desirable continuous yielding during tensile deformation. Al is added into the medium Mn steel to enlarge the process window and to improve the partitioning efficiency of Mn. The produced steel is more robust with temperature fluctuation during the industrial process due to the enlarged intercritical region. Mn partitioning is more efficient owing to the elevated annealing temperature, which results in the improvement of ductility in the Al-added steel with increased austenite stability.

Sign in / Sign up

Export Citation Format

Share Document