Microstructure and Mechanical Properties of Narrow Gap Laser-Arc Hybrid Welded 40 mm Thick Mild Steel
Abstract
:1. Introduction
2. Experimental
3. Results and Discussion
3.1. Microstructure
3.2. Microhardness
3.3. Tensile Strength and Impact Toughness
4. Conclusions
- (1)
- An accepted weld of 40 mm thick mild steel was obtained by narrow gap laser-arc hybrid welding with nine passes at a 6 mm width narrow gap. The weld was with smooth layer transition and free of visible defects.
- (2)
- The weld could be characterized by some typical layers with different microstructure, which are the laser zone of the root layer, the arc zone of the root layer, the filler layer, and an overlapped interlayer between filler layers. The laser zone of the root layer had the lowest content of acicular ferrite within the fusion zone (48.9%), while the arc zone of root layer had the highest content of acicular ferrite (60.3%).
- (3)
- At the laser zone of the root layer, the fusion zone had the highest microhardness, 20–40 HV0.2 higher microhardness than the fusion zone of other layers. The microhardness transition was smooth from the fusion zone to the base metal along the horizon direction of the laser zone, while an obvious hardening zone appeared in other layers because the microhardness of their fusion zone was lower than their heat affected zone. The microhardness deviation of all filler layers along weld thickness direction was no more than 15 HV0.2, indicating that no temper softening appeared during multiple heat cycles.
- (4)
- The lower part of the weld had the lowest mechanical properties because of the lowest amount of acicular ferrite, but its ultimate tensile strength and impact absorbing energy were still 49% and 60% higher than those of base metal, respectively, indicating that the weld had a good performance.
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Materials | Compositions (wt %) | Mechanical Properties | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
C | Si | Mn | P | S | Others | Fe | YS (MPa) | UTS (MPa) | EL (%) | IAE (J) | |
BM | 0.12 | 0.15 | 0.44 | 0.015 | 0.008 | ≤0.3 | Bal. | ≥235 | 450 | 26 | 120 |
Filling wire | 0.08 | 0.92 | 1.52 | 0.020 | 0.015 | ≤0.5 | Bal. | ≥420 | 550 | 30 | 150 |
Parameters | Root Layer Welding | Filler Layer Welding |
---|---|---|
D (mm) | 3 | 3 |
Δf (mm) | −2 | −2 |
α (°) | 55–60 | 55–60 |
CTWD (mm) | 10–12 | 10–12 |
P (W) | 3000 | 800 |
I (A) | 210 | 230 |
U (V) | 24.1 | 24.9 |
Vf (m·min−1) | 7.2 | 7.7 |
PF (Hz) | 177.4 | 188.7 |
T (s) | - | 300 |
v (m·min−1) | 0.4 | 0.4 |
Location | UTS | IAE | |
---|---|---|---|
FZ | HAZ | ||
Whole weld | 712.5 ± 15.0 | - | - |
Upper specimen | 697.6 ± 14.6 | 208.3 ± 12.3 | 181.7 ± 10.7 |
Middle specimen | 695.3 ± 14.6 | 205.7 ± 12.1 | 179.0 ± 10.6 |
Lower specimen | 671.4 ± 14.1 | 192.3 ± 11.3 | 158.3 ± 9.3 |
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Zhang, C.; Li, G.; Gao, M.; Zeng, X. Microstructure and Mechanical Properties of Narrow Gap Laser-Arc Hybrid Welded 40 mm Thick Mild Steel. Materials 2017, 10, 106. https://doi.org/10.3390/ma10020106
Zhang C, Li G, Gao M, Zeng X. Microstructure and Mechanical Properties of Narrow Gap Laser-Arc Hybrid Welded 40 mm Thick Mild Steel. Materials. 2017; 10(2):106. https://doi.org/10.3390/ma10020106
Chicago/Turabian StyleZhang, Chen, Geng Li, Ming Gao, and XiaoYan Zeng. 2017. "Microstructure and Mechanical Properties of Narrow Gap Laser-Arc Hybrid Welded 40 mm Thick Mild Steel" Materials 10, no. 2: 106. https://doi.org/10.3390/ma10020106
APA StyleZhang, C., Li, G., Gao, M., & Zeng, X. (2017). Microstructure and Mechanical Properties of Narrow Gap Laser-Arc Hybrid Welded 40 mm Thick Mild Steel. Materials, 10(2), 106. https://doi.org/10.3390/ma10020106