Liquid Metal Embrittlement Cracking in Uncoated Transformation-Induced Plasticity Steel during Consecutive Resistance Spot Welding
Abstract
:1. Introduction
2. Materials and Methods
3. Results and Discussion
3.1. LME Cracks in the Uncoated TRIP Steel Joints
3.2. Formation Mechanism of the LME Cracks in the Uncoated TRIP Steel Joint
3.3. Statistics of the LME Cracks in the Consecutive Welding
4. Conclusions
- (1)
- Small cracks were observed at the surface of the uncoated steel joints with a maximum length of about 30 µm and 50 µm in Location A (weld center) and Location B (shoulder of the weld), respectively, which were confirmed to be LME cracks.
- (2)
- During the consecutive welding, the electrode experienced metallurgical degradation or contamination with Zn (formation of different Cu-Zn phases) from the galvannealed steel. When welding the uncoated steel, owing to the heat generation at the electrode/sheet interface, the Cu-Zn phases melted, exposing the uncoated steel surface to liquid Zn and Cu, leading to LME cracking.
- (3)
- The occurrence and characteristics of the crack formation differed for each location as the number of welds increased due to the variation in Zn content. Type A cracks did not form when the number of welds was less than 280. However, several cracks with a total length of approximately 30 μm were formed between 280 and 400 welds. On the other hand, type B cracks began to appear after 40 welds. However, the number and size of these exhibited inconsistency as the number of welds increased.
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Chemical Composition (wt. %) | Mechanical Properties | |||||
---|---|---|---|---|---|---|
Fe | C | Si | Mn | Ultimate tensile strength (MPa) | Yield strength (MPa) | Elongation (%) |
Bal. | 0.2 | 1.5 | 2.4 | 980 | 625 | 21 |
Electrode Force (kN) | Welding Current (kA) | Time (Cycle *) | ||
---|---|---|---|---|
Squeeze | Weld | Hold | ||
4 | 9 | 45 | 30 | 5 |
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Kim, J.W.; Manladan, S.M.; Mahmud, K.; Jin, W.; Krishna, T.; Ji, C.; Nam, D.-G.; Park, Y.-D. Liquid Metal Embrittlement Cracking in Uncoated Transformation-Induced Plasticity Steel during Consecutive Resistance Spot Welding. Metals 2023, 13, 1826. https://doi.org/10.3390/met13111826
Kim JW, Manladan SM, Mahmud K, Jin W, Krishna T, Ji C, Nam D-G, Park Y-D. Liquid Metal Embrittlement Cracking in Uncoated Transformation-Induced Plasticity Steel during Consecutive Resistance Spot Welding. Metals. 2023; 13(11):1826. https://doi.org/10.3390/met13111826
Chicago/Turabian StyleKim, Jae Won, Sunusi Marwana Manladan, Kaisar Mahmud, Woosung Jin, Tejaswin Krishna, Changwook Ji, Dae-Geun Nam, and Yeong-Do Park. 2023. "Liquid Metal Embrittlement Cracking in Uncoated Transformation-Induced Plasticity Steel during Consecutive Resistance Spot Welding" Metals 13, no. 11: 1826. https://doi.org/10.3390/met13111826