The core challenges of aluminum welding boil down to three “enemies”: Oxide Film (Al₂O₃), High Thermal Conductivity, and Hydrogen Porosity. Welding aluminum is not an “upgraded version” of welding steel—it is a completely different discipline. From cleanliness and equipment settings to operational techniques, everything must be rethought.
Below is a comprehensive technical framework covering key difficulties, mainstream processes, critical parameters, and practical tips.
I. Three Core Challenges of Aluminum Welding
- Tenacious Oxide Film (Al₂O₃) : Aluminum instantly forms a dense oxide layer on its surface. Its melting point is 2050°C, while the aluminum base metal melts at only 660°C. If this film is not broken, it prevents fusion and causes slag inclusion.
- Rapid Heat Dissipation: Aluminum’s thermal conductivity is approximately 4-5 times that of steel. Heat dissipates quickly to the surrounding area during welding, making arc initiation difficult and penetration shallow. The heat input required for aluminum is typically 2-4 times higher than for steel.
- High Susceptibility to Porosity: Liquid aluminum dissolves a large amount of hydrogen, but its solubility drops sharply upon solidification. If moisture is present on the filler metal or in the environment, the hydrogen cannot escape in time, forming subsurface or through-thickness porosity.
II. Selecting the Mainstream Welding Methods
While several methods exist for aluminum, TIG and MIG are the workhorses, with Friction Stir Welding as a premium option for critical applications.
| Welding Method | Core Characteristics | Typical Applications | Key Considerations |
|---|---|---|---|
| TIG (GTAW) | Must use AC. Utilizes the “cathodic cleaning” action to remove oxide film. Produces aesthetically pleasing welds, no spatter. | Thin sheets (0.5-6mm) , positional welding, root passes, precision components. | More complex equipment, unsuitable for outdoor work; slower travel speed. |
| MIG (GMAW) | High arc power, 2-3 times more productive than TIG. Requires high current and fast wire feed speed to counter heat loss. | Medium-thick plates (≥3mm) , long welds, high-volume structural fabrication. | Semi-automatic; finer wire is more sensitive to porosity; careful with burn-through at high currents. |
| Friction Stir Welding (FSW) | Solid-state process (below melting point). No cracks, porosity, or fumes. Minimal post-weld distortion. | High-integrity applications: aerospace fuel tanks, ship decks, high-speed train bodies. | Requires specialized, dedicated equipment and rigid fixturing; low flexibility. |
| Pulsed TIG/MIG | Uses pulsed current to control heat input, minimizing distortion and HAZ width. | Thin sheets (<2.5mm) , all-position welding, heat-sensitive hard/super-hard alloys. | - |
| Oxyfuel Welding | Simple, inexpensive equipment. | Non-critical components (0.5-10mm) or cast iron repair. | Requires flux; flux residue must be thoroughly cleaned post-weld to prevent corrosion. |
Post time: Feb-12-2026
