Effects of Shielding and Drainage Gas Flow Rates on Weld Quality, Microstructure and Mechanical Properties of 304NG Stainless Steel in Local Dry Underwater Laser Welding
Abstract
1. Introduction
2. Materials and Methods
3. Results and Analysis
3.1. Analysis of Weld Bead Morphology and Microstructure
3.1.1. Characteristics of the Weld Cross-Section
3.1.2. Microstructural Analysis of Joints with Optimal Weld Bead Configuration
3.2. Mechanical Properties of Welded Joints
3.2.1. Hardness Distribution in Joints
3.2.2. Tensile Properties of Joints
4. Discussion
5. Conclusions
- (1)
- This study conducted preliminary research into the effects of argon flow rate and drainage air flow rate on the weld formation, microstructure, and mechanical properties of 304NG stainless steel joints produced by local dry underwater laser welding.
- (2)
- The impact of both gas parameters on the quality of welds within the tested range was found to be significant. The optimal conditions for this experiment were established as 30 litres of shielding gas and 80 litres of drainage gas per minute, which resulted in the optimal weld appearance and the highest average maximum tensile load of 4314.4 N.
- (3)
- In optimal conditions, the weld metal primarily exhibited austenitic and ferritic phases, and the hardness distribution along the weld depth remained relatively stable, with an average value of approximately 180 HV.
- (4)
- The drainage gas was found to primarily encourage water removal and enhance local dry cavity stability. In contrast, the shielding gas was observed to improve molten-pool protection and weld stability. It was therefore imperative that the two gas flow rates were matched appropriately in order to enhance the quality of the welds and the performance of the joints.
- (5)
- Since this study was performed under shallow laboratory conditions without in situ diagnostics, the effects of water environment, cavity evolution, and molten-pool dynamics were not directly examined. Further work is needed to clarify the coupled mechanisms involving gas flow, cavity stability, laser energy transfer, bubble behavior, and molten-pool flow.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
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| Element | C | Si | Mn | P | S | Cr | Ni | Cu | N | Fe |
|---|---|---|---|---|---|---|---|---|---|---|
| Percentage % | 0.035 | 0.98 | 2.0 | 0.030 | 0.015 | 18.9 | 9.48 | 0.95 | 0.060 | Bal. |
| Number | Process Parameters | Drainage Gas (Air) Flow Rate (L/min) | Laser Shielding Argon Gas Flow Rate (L/min) |
|---|---|---|---|
| S1 | Laser Power 3.0 kW Welding Speed 8 mm/s | 80 | 30 |
| S2 | 40 | 15 | |
| S3 | 40 | 30 | |
| S4 | 80 | 15 | |
| S5 | 0 | 15 |
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© 2026 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license.
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Luo, S.; Yang, Y.; Dong, J.; Yang, Y.; Luo, Z. Effects of Shielding and Drainage Gas Flow Rates on Weld Quality, Microstructure and Mechanical Properties of 304NG Stainless Steel in Local Dry Underwater Laser Welding. Metals 2026, 16, 423. https://doi.org/10.3390/met16040423
Luo S, Yang Y, Dong J, Yang Y, Luo Z. Effects of Shielding and Drainage Gas Flow Rates on Weld Quality, Microstructure and Mechanical Properties of 304NG Stainless Steel in Local Dry Underwater Laser Welding. Metals. 2026; 16(4):423. https://doi.org/10.3390/met16040423
Chicago/Turabian StyleLuo, Shuyue, Yue Yang, Jianwei Dong, Yang Yang, and Zhen Luo. 2026. "Effects of Shielding and Drainage Gas Flow Rates on Weld Quality, Microstructure and Mechanical Properties of 304NG Stainless Steel in Local Dry Underwater Laser Welding" Metals 16, no. 4: 423. https://doi.org/10.3390/met16040423
APA StyleLuo, S., Yang, Y., Dong, J., Yang, Y., & Luo, Z. (2026). Effects of Shielding and Drainage Gas Flow Rates on Weld Quality, Microstructure and Mechanical Properties of 304NG Stainless Steel in Local Dry Underwater Laser Welding. Metals, 16(4), 423. https://doi.org/10.3390/met16040423
