Aluminum is harder to weld than steel due to:
- High thermal conductivity (4× steel) — heat dissipates quickly
- Oxide layer (Al₂O₃, melting point 2050°C vs base Al 660°C) — must be removed
- Hydrogen porosity — molten aluminum absorbs hydrogen 20× more than steel
- Hot cracking — common in 5xxx and 6xxx series alloys
Process | Thickness | Best For | Typical Cost
--- | --- | --- | ---
TIG (GTAW) | 0.5-6mm | Thin sheet, appearance welds | ¥80-150/hr
MIG (GMAW) | 3-25mm | Production welding | ¥60-120/hr
Friction Stir (FSW) | 2-30mm | Long seams, zero porosity | ¥150-300/hr
TIG is most common in Chinese shops for custom fabrication. MIG used for production runs. FSW limited to specialized shops.
Base Alloy | Recommended Filler | Why
--- | --- | ---
6061-T6 | ER4043 (AlSi5) | Good fluidity, crack resistance
5052-H32 | ER5356 (AlMg5) | Matches color, good corrosion
7075-T6 | ER5183 | High strength weld
5083 | ER5183 or ER5356 | Marine-grade, high Mg
Cast A356 | ER4043 | Matches Si content
1. Clean base metal with stainless steel brush (dedicated to Al — never use on steel)
2. Pre-heat to 100-150°C for sections >10mm
3. Use pure argon (99.996% minimum) at 12-18 L/min
4. Keep filler rod 30°C above freezing (no condensation)
5. Remove oxide layer within 2 hours of welding
6. For critical joints, request FSW instead — zero porosity guaranteed