GTAW Welding of Aluminum and Other Non-Ferrous Metals
This domain tests GTAW of aluminum and other non-ferrous metals, focusing on oxide removal, AC settings, filler selection, and heat control.
Core rules
- Aluminum forms a refractory oxide that melts at a much higher temperature than the metal. Clean mechanically with a dedicated stainless brush and solvent, then weld before oxide reforms.
- Use AC for aluminum. The electrode-positive portion provides cleaning action, while electrode-negative provides penetration. Set balance, frequency, and current according to thickness and WPS.
- Aluminum conducts heat rapidly. Thick sections may need preheat per the WPS; thin sections need low current and fast travel to avoid melt-through.
- Select filler by base alloy and service: ER4043 is common for many cast and 6xxx alloys, while ER5356 is used for 5xxx alloys and where higher strength or anodizing color match matters. Follow the WPS.
- Argon is standard; helium or argon-helium mixes may be used for thick aluminum or copper because they increase heat input. For copper alloys, DCEN and preheat are common; magnesium alloys often use AC.
- Keep stainless steel and aluminum tools separate. Do not use a carbon steel brush on aluminum.
Worked example
A 3 mm 6061 aluminum butt joint is to be welded. The welder degreases, brushes with a stainless-only brush, selects AC, sets cleaning balance per the WPS, uses a 2.4 mm tungsten and ER4043 filler, and maintains a short arc with fast travel. If the weld is sooty or the oxide is not breaking down, cleaning action or gas coverage is insufficient. If the plate melts through, current is too high or travel is too slow.
Traps that cost marks
- Using DCEN and expecting aluminum oxide cleaning.
- Brushing aluminum with a carbon steel brush.
- Overheating thin aluminum and causing melt-through.
- Choosing filler without checking the base alloy and WPS.
- Using too little gas flow or too long an arc.