Microstructure and Mechanical Behaviors of Fiber-Laser-Welded QP980-QP1180 Steels
Abstract
:1. Introduction
2. Materials and Methods
2.1. Materials and Laser Welding Process
2.2. Microstructural Characterizations
2.3. Mechanical Characterizations
3. Results and Discussion
3.1. Metallographic Characterization
3.1.1. Microstructure of BMs
3.1.2. Microstructure of Laser-Welded 1.2 mm QP980 and 1.5 mm QP1180 Steels
3.2. Mechanical Characterization
3.2.1. Microhardness Measurement
3.2.2. Tensile Tests
3.2.3. Erichsen Tests
3.3. Fractography
4. Conclusions
- (a)
- Laser welding 1.2 mm QP980 and 1.5 mm QP1180 steels resulted in a microstructure that consisted of a lath M phase in FZ. The microstructure of QP980 and QP1180 steels consists of the M phase at the supercritical HAZ and is transformed into a microstructure that consists of RA, F, and M in the sub-critical HAZ.
- (b)
- The hardness of the BMs of QP980 and QP1180 were measured as 380 Hv and 400 Hv, respectively. The microhardness of the FZ of the joint was measured as 510 Hv. This value is considerably higher than those of both BMs. The hardness value of the HAZ reflected a limited variation through the HAZ of both the QP980 and QP1180 sides. The HAZ hardness values decreased sharply to the BM hardness levels by the end of the sub-critical HAZ.
- (c)
- The yield and tensile strengths of the welded steels were measured as 816.6 MPa and 1194.2 MPa, respectively. The uniform elongation and elongation at break values of these steels were determined as 6.9% and 9.3%, respectively.
- (d)
- The laser-welded pair showed an Erichsen index of 6.98 mm, which is 70% of that of the 1.2 QP980 steel. This value is acceptable for industrial applications of QP steel. The lower Erichsen index of the pair is mainly attributed to the full M microstructure of the weld seam, leading to the early onset of fracture at the biaxial tensile loading of the Erichsen test.
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
Abbreviations
AHSS | Advanced High-Strength Steel |
BIW | Body in White |
BM | Base Metal |
EBSD | Electron Backscatter Diffraction |
EL | Elongation |
F | Ferrite |
FZ | Fused Zone |
HAGB | High Angle Grain Boundaries |
HAZ | Heat-Affected Zone |
Hv | Microhardness Vickers |
LME | Liquid Metal Embrittlement |
M | Martensite |
QP | Quenching and Portioning |
RA | Retained Austenite |
TM | Tempered Martensite |
TRIP | Transformation-Induced Plasticity |
UTS | Ultimate Tensile Strength |
YS | Yield Strength |
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Steel Grade | Coating | Thickness |
---|---|---|
QP980 | Uncoated | 1.2 mm |
QP1180 | GI (hot-dip galvanized coating) | 1.5 mm |
Sample | Yield Strength (MPa) | Tensile Strength (MPa) | Uniform Elongation (%) | Elongation to Failure (%) | Fracture Location | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1.2 QP980 | 801.3 | ± | 2.3 | 1050.7 | ± | 2.3 | 14.7 | ± | 0.2 | 17.2 | ± | 0.5 | BM | |
1.5 QP1180 | 1042.4 | ± | 25.8 | 1180.0 | ± | 5.5 | 9.7 | ± | 0.4 | 12.4 | ± | 0.5 | BM | |
1.2 QP980–1.5 QP1180 | 816.6 | ± | 45.8 | 1194.2 | ± | 21.9 | 6.9 | ± | 2.6 | 9.3 | ± | 1.7 | QP980-BM |
Sample | Punch Force (F) (kN) | Erichsen Index (mm) | Fracture Location | ||||
---|---|---|---|---|---|---|---|
1.2QP 980 | 60.81 | ± | 1.9 | 9.99 | ± | 0.4 | BM |
1.5QP 1180 | 71.79 | ± | 1.9 | 8.62 | ± | 0.2 | BM |
1.2 QP980-1.5 QP1180 | 42.55 | ± | 10.2 | 6.98 | ± | 1.0 | Weld seam |
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Çelik, H.; Saray, O. Microstructure and Mechanical Behaviors of Fiber-Laser-Welded QP980-QP1180 Steels. Metals 2025, 15, 174. https://doi.org/10.3390/met15020174
Çelik H, Saray O. Microstructure and Mechanical Behaviors of Fiber-Laser-Welded QP980-QP1180 Steels. Metals. 2025; 15(2):174. https://doi.org/10.3390/met15020174
Chicago/Turabian StyleÇelik, Hafize, and Onur Saray. 2025. "Microstructure and Mechanical Behaviors of Fiber-Laser-Welded QP980-QP1180 Steels" Metals 15, no. 2: 174. https://doi.org/10.3390/met15020174
APA StyleÇelik, H., & Saray, O. (2025). Microstructure and Mechanical Behaviors of Fiber-Laser-Welded QP980-QP1180 Steels. Metals, 15(2), 174. https://doi.org/10.3390/met15020174