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Obtaining microstructures of hot-rolled dual-phase steel plates Cover

Obtaining microstructures of hot-rolled dual-phase steel plates

Materials Science-Poland
Volume 43 (2025): Issue 2 (June 2025)
By: Victor Gaytán,  Nancy López,  Constantin Hernández,  José Ramos,  Emmanuel Gutiérrez and  Nicolás Herrera  
Open Access
|Jun 2025

Figures & Tables

Figure 1

Thermomechanical process used to obtain hot-rolled DP steel plates.
Thermomechanical process used to obtain hot-rolled DP steel plates.

Figure 2

(a) Cooling system designed for cooling of steel after the hot rolling process, (b) diagram of the metal support and plate instrumented with thermocouples, and (c) cooling system conditions [19].
(a) Cooling system designed for cooling of steel after the hot rolling process, (b) diagram of the metal support and plate instrumented with thermocouples, and (c) cooling system conditions [19].

Figure 3

Scheme of distribution hardness measurements in cross sections of steel.
Scheme of distribution hardness measurements in cross sections of steel.

Figure 4

Cooling rate achieved with conditions shown in Figure 2(c).
Cooling rate achieved with conditions shown in Figure 2(c).

Figure 5

CCT diagram calculated using the chemical composition of the experimental steel.
CCT diagram calculated using the chemical composition of the experimental steel.

Figure 6

Effect of thickness reduction during hot rolling on the γ → α + α′ phase transformation for the experimentally produced steel: (a) 10% (953.0°C), (b) 20% (812.7°C), (c) 30% (783.6°C), and (d) 40% (744.0°C). Cooling rate was kept constant at 30°C s−1.
Effect of thickness reduction during hot rolling on the γ → α + α′ phase transformation for the experimentally produced steel: (a) 10% (953.0°C), (b) 20% (812.7°C), (c) 30% (783.6°C), and (d) 40% (744.0°C). Cooling rate was kept constant at 30°C s−1.

Figure 7

Effect of thickness reduction, applied during hot rolling, on the amount of ferrite.
Effect of thickness reduction, applied during hot rolling, on the amount of ferrite.

Figure 8

Hardness values obtained for samples subjected to different hot rolling conditions.
Hardness values obtained for samples subjected to different hot rolling conditions.

Figure 9

Vickers microhardness profile made throughout the thickness of sample 4, which is composed of ∼55%α + 45%α´.
Vickers microhardness profile made throughout the thickness of sample 4, which is composed of ∼55%α + 45%α´.

Figure 10

Stress vs strain graph corresponding to steels processed under different hot rolling conditions to 10% (953.0°C), 20% (812.7°C), 30% (783.6°C) and 40% (744.0°C).
Stress vs strain graph corresponding to steels processed under different hot rolling conditions to 10% (953.0°C), 20% (812.7°C), 30% (783.6°C) and 40% (744.0°C).

Figure 11

SEM photomicrographs of the DP steel corresponding to sample 4 after being subjected to the impact test: (a) specimen 1, (b) specimen 2, and (c) specimen 3.
SEM photomicrographs of the DP steel corresponding to sample 4 after being subjected to the impact test: (a) specimen 1, (b) specimen 2, and (c) specimen 3.

Processing variables used during hot rolling_

SampleNumber of passesReduction (%)Final thickness (mm, initial = 15.20)Finishing temperature (°C)
1110.0013.62953.0
2219.7212.21812.7
3431.1710.38783.6
4539.619.42744.1

Some of the chemical compositions used for the simulation of the CCT diagrams to obtain a DP steel_

CMnSiCrMoNbTiAlBPS
10.111.80.52.750.60.005—1—0.040.04
20.151.80.3—0.60.0030.50.90.00050.050.05
30.151.50.50.80.60.0050.510.00010.050.05
40.151.80.5—0.50.0050.510.00050.050.05
50.150.50.50.5—0.003—0.90.00010.050.05
⁞⁞⁞⁞⁞⁞⁞⁞⁞⁞⁞⁞
370.180.750.50.25—0.005—10.00010.050.05
380.1210.4—0.250.005—10.00030.020.02
390.150.250.3——0.003—0.90.00010.020.02
400.150.750.5——0.005—10.00050.020.02

Results obtained from microhardness measurements_

LimitMicrohardness
UL437 HV
BL396 HV
Mean414 HV
Standard deviation8.45

Chemical composition proposed from the computational study and composition of the experimental steel_

CMnSiNbAlBPS
Chemical composition proposed from the behavior of CCT diagrams
Min.0.140.50.30.0030.30.0003——
Máx.0.161.00.50.0050.90.00050.020.02
Chemical composition of the experimental steel (wt%)
0.151.040.440.0060.40.00050.0140.03

Phases and mechanical properties calculated with the chemical composition of the experimental steel_

Properties/phaseResults
Cooling rate30°C s−1
Hardness37.7 HRC
Vickers hardness 400 HV
UTS900.2 MPa
Ferrite46.18%
Martensite52.15%
Bainite1.52%
Pearlite0.13%
Austenite0.02
DOI: https://doi.org/10.2478/msp-2025-0022 | Journal eISSN: 2083-134X | Journal ISSN: 2083-1331
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Language: English
Page range: 101 - 112
Submitted on: Mar 5, 2025
|
Accepted on: Jun 29, 2025
|
Published on: Jun 30, 2025
Published by: Wroclaw University of Science and Technology
In partnership with: Paradigm Publishing Services
Publication frequency: 4 issues per year
Keywords:
Dual-phase steel,
Hot rolling,
Controlled cooling,
CCT diagrams,
Mechanicals properties,
Alloying elements
Related subjects:
Materials sciences,
Materials sciences, other,
Nanomaterials,
Functional and smart materials,
Materials characterization and properties

© 2025 Victor Gaytán, Nancy López, Constantin Hernández, José Ramos, Emmanuel Gutiérrez, Nicolás Herrera, published by Wroclaw University of Science and Technology
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

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