Aluminum alloys are widely used in industrial products due to their excellent physical properties. Almost all welding methods can be applied to aluminum and its alloys, but their adaptability varies depending on the method. Each welding technique has its specific applications.
Improper selection of welding methods or process parameters can lead to severe deformation of aluminum alloy components after welding. Defects such as porosity, slag inclusion, lack of penetration, cracks, or material looseness in the weld can significantly impact product quality and performance. Below, we analyze the methods and precautions for aluminum alloy welding.
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Three Welding Methods for Aluminum Alloys
1. Tungsten Inert Gas (TIG) Welding
- Primarily used for aluminum alloys, TIG welding offers high-quality results. However, the equipment is complex and unsuitable for outdoor operations.
2. Resistance Spot Welding and Seam Welding
- Suitable for aluminum alloy sheets under 5mm thickness. This method requires complex equipment and high currents but is highly efficient for mass production.
3. Pulsed Argon Arc Welding
- Enhances stability during welding by adjusting parameters to control arc power and weld formation. Ideal for thin plates, all-position welding, and heat-sensitive alloys like forged aluminum, hard aluminum, and super-hard aluminum.
Key Precautions for Aluminum Alloy Welding
1. Surface Preparation: Clean the welding area thoroughly with acetone to remove oil, dust, or contaminants. For thick plates, use a steel wire brush followed by acetone cleaning.
2. Preheating: Preheat thicker plates to prevent lack of penetration. Use low current for crater filling at the end of welding.
3. Standardized Welding: Follow specifications based on plate thickness.
4. Cable Management: Avoid excessively long welding gun cables to ensure stable wire feeding.
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I. Welding Material Requirements
01 Shielding Gas Selection
> Use argon (Ar, purity >99.99%) or helium (He). Argon is most common. Impurity limits: He <0.04%, O₂ <0.03%, H₂O <0.07%.
02 Tungsten Electrodes
> Options include pure tungsten, thoriated tungsten (ThO₂), ceriated tungsten (WCe20), and zirconiated tungsten. Ceriated tungsten is preferred for its stability and low radioactivity.
03 Flux Selection
> Use chloride/fluoride-based fluxes. Avoid sodium-containing fluxes for aluminum-magnesium alloys.
04 Welding Wire Selection
> Match filler alloy to base material (e.g., 5356, 5183, or 5556 wire for 5083 aluminum). Prioritize weld performance based on application requirements.
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II. Pre-Welding Preparation
1. Groove Machining: Use mechanical methods (no plasma/flame). Remove oxidation layers and ensure a smooth, silvery surface.
2. Material Cleaning: Remove oxides using stainless steel brushes or chemical treatments (e.g., NaOH and HNO3 baths).
3. Assembly: Avoid forced alignment to prevent stress. Follow positioning weld specifications:
| Material Thickness (mm) |
Positioning WeldSpacing (mm) |
Positioning Weld Length (mm) |
| <3 |
40–50 |
4–6 |
| 3–6 |
50–60 |
5–10 |
| >6 |
50–80 |
10–12 |
| Takeover or flange |
2-4 dot |
3-8 dot each |
4. Fixture Design: Use carbon steel or stainless steel fixtures for heat dissipation.
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III. Welding Requirements
1. Environment: Avoid welding in dusty, humid (>80%), or windy (>1.5m/s) conditions.
2. Technique: Use AC for TIG welding. Preheat plates >10mm thick (<100°C).
3. Quality Standards:
- Weld Reinforcement: 0–5mm for flat welds; 0–5mm for other positions.
- Defect Limits: No cracks, porosity, or undercutting (max 0.5mm depth for non-pressure vessels).
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IV. Weld Repair and Inspection
1. Defect Analysis: Identify root causes (e.g., hydrogen-induced porosity or cracking).
2. Repair Limits: Maximum two repairs per location.
3. Testing:
- RT (Radiographic Testing): For A/B class welds.
- PT (Penetrant Testing): For surface defects on C/D class welds.
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V. Key Defect Prevention
- Porosity: Control hydrogen sources (clean materials, dry shielding gas, low humidity).
- Cracking: Use crack-resistant filler wires (e.g., Si-containing alloys) and minimize joint restraint.
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VI. NDT Requirements
1. Post-weld inspection for critical joints (e.g., 100% RT for A/B class welds).
2. Surface defects repaired via PT.
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