Zhuojin Pipe Fitting Co., LtdMIG Welding Process Development for Aluminum Busbar 6063
Literature Overview
This paper, authored by Tang Yanling and Wang Zhihong from Shandong Electric Power School, was published in Welding Machine in 2011 (Vol. 41, No. 3, pp. 83-84). The study focuses on the welding process development for 6063 aluminum alloy busbar tubes with a specification of φ250 mm × 10 mm, welded in the horizontal fixed position. The research was conducted for welder training purposes and addresses the critical issue of porosity in aluminum alloy welding. The classification code TG457.1 indicates the focus on arc welding process development.
Weldability Analysis of 6063 Aluminum Alloy
Aluminum alloy 6063 is a heat-treatable alloy in the Al-Mg-Si system, widely used in electrical applications due to its good electrical conductivity and formability. The weldability of 6063 is influenced by several factors:
| Factor | Description | Impact on Welding |
|---|---|---|
| High thermal conductivity | ~200 W/(m·K) | Large heat sink effect; requires high heat input |
| Oxide film (Al₂O₃) | Melting point ~2050°C vs. aluminum ~660°C | Causes incomplete fusion and inclusion defects |
| Hydrogen solubility | High solubility in liquid, low in solid | Primary cause of porosity |
| Low density | 2.7 g/cm³ | Easy to handle but requires precise torch positioning |
| Thermal expansion | High coefficient (~23 × 10⁻⁶/K) | Distortion and residual stress concerns |
The most critical challenge identified in this study is porosity, which arises from hydrogen absorption from moisture in the shielding gas, surface contamination, and the rapid solidification of aluminum. The φ250 mm × 10 mm busbar tube presents additional challenges due to its large diameter, which creates significant heat dissipation through the tube walls and requires careful control of the welding procedure to maintain adequate heat input.
Welding Process Parameters and Technique
The horizontal fixed position welding of the large-diameter busbar tube requires specific technique adjustments compared to flat or vertical positions. The following process parameters and control measures were identified as critical:
| Parameter | Recommended Range | Control Rationale |
|---|---|---|
| Welding current | 180-220 A | Adequate penetration without excessive burn-through |
| Welding voltage | 18-22 V | Stable arc length for consistent heat input |
| Travel speed | 150-250 mm/min | Balance between heat input and distortion |
| Shielding gas flow rate | 15-20 L/min | Prevents atmospheric contamination and porosity |
| Wire diameter | φ1.2 mm | Suitable for 10 mm thickness in single-pass |
| Preheating temperature | 100-150°C | Reduces hydrogen absorption and improves fluidity |
The welding technique involves careful control of the torch angle and travel speed to compensate for gravity effects on the molten pool in the horizontal fixed position. The welder must continuously adjust the torch position to maintain a uniform weld bead profile around the circumference of the tube. The study emphasizes the importance of surface preparation, including thorough cleaning to remove oxide films and organic contaminants, and the use of dry shielding gas to minimize hydrogen pickup.
Quality Verification and Inspection
The welded joints were subjected to a series of inspections and tests in accordance with relevant codes and standards:
- Visual inspection (VT): Checking for surface defects, bead profile, and weld continuity.
- Radiographic testing (RT): Detecting internal porosity, lack of fusion, and other volumetric defects.
- Mechanical testing: Tensile tests to verify joint strength meets or exceeds the base metal requirements.
- Dye penetrant testing (PT): Identifying surface-breaking defects that may not be visible to the naked eye.
All test results met the required acceptance criteria, confirming the adequacy of the developed welding procedure. The successful qualification of this process has enabled its integration into welder training programs, providing practical skills development for power station installation and transmission/distribution equipment aluminum busbar welding.
Key Reflections and Study Insights
This paper, while relatively concise, addresses a practical and important industrial need. The horizontal fixed position welding of large-diameter aluminum busbar tubes is a challenging operation that requires both sound process knowledge and skilled operator technique. The emphasis on porosity control is well-founded, as porosity is the most common and quality-critical defect in aluminum welding. The approach of preheating to reduce hydrogen absorption and using dry shielding gas represents fundamental best practices that are sometimes overlooked in field applications.
From a training perspective, the systematic approach to process development—starting with weldability analysis, proceeding to parameter optimization, and concluding with comprehensive quality verification—provides a replicable framework for developing welding procedures for other aluminum alloy applications. The FMEA approach could be further applied to identify potential failure modes during production welding, such as gas cylinder contamination, improper preheating, or operator technique deviations, and to develop preventive measures for each identified risk.