Master the challenges of welding aluminum. Learn about cleaning, joint preparation, parameter selection, and techniques for TIG and MIG aluminum welding.
What Buyers Mean by Aluminum Welding
Aluminum welding presents unique challenges due to the oxide layer, high thermal conductivity, and low melting point. At Fulei Metal, our welders are experienced in aluminum welding for automotive, aerospace, and consumer goods clients.
Challenges of Aluminum Welding
Oxide Layer
Aluminum forms a tough oxide layer (melting point 2,070 degrees C vs 660 degrees C for aluminum). Must be removed before welding. AC TIG cleaning action or mechanical removal required.
High Thermal Conductivity
Aluminum conducts heat three times faster than steel. Requires higher amperage. Heat dissipates quickly from the weld zone. Pre-heating may be needed for thick sections.
Low Melting Point
Aluminum melts at 660 degrees C. No color change before melting. Sudden transition from solid to liquid. Risk of burn-through and collapse.
Thermal Expansion
Aluminum expands twice as much as steel. More distortion during welding. Requires proper clamping and sequencing.
Preparation
Cleaning Aluminum Welding
Remove oxide layer mechanically (stainless brush) or chemically (etching). Clean with acetone or solvent. Remove all oil, grease, and contamination. Weld within hours of cleaning.
Joint Preparation
Square butt joints for materials up to 3 mm. Beveled joints for thicker materials. Very tight fit-up required. Gaps cause burn-through.
Filler Metal Selection
ER4043: silicon-based, good flow, crack-resistant, general purpose. ER5356: magnesium-based, higher strength, better color match after anodizing. ER4047: higher silicon, excellent for automotive.
TIG Welding Aluminum
AC Balance
Cleaning action (electrode positive) removes oxide. Penetration (electrode negative) provides heat. Balance control adjusts the ratio. Typically 65-75% penetration.
Amperage
1 mm: 50-80 amps AC. 2 mm: 80-120 amps. 3 mm: 120-180 amps. 6 mm: 200-280 amps. Use pulse for thin materials.
Technique
Keep arc short. Move steadily. Add filler to the front of the pool. Watch the pool, not the arc. Use foot pedal for amperage control.
MIG Welding Aluminum
Wire Feed
Use spool gun or push-pull system. Soft aluminum wire easily tangles. 0.8-1.0 mm diameter for sheet metal.
Key Parameters on Aluminum Welding
1 mm: 60-90 amps, 15-17V. 2 mm: 100-140 amps, 17-19V. 3 mm: 140-180 amps, 19-22V. Use spray or pulsed transfer.
Technique
Push technique only (not drag). Keep stick-out short (6-10 mm). Move steadily. Watch the pool.
Where Aluminum Welding Runs Into Trouble
Porosity: clean thoroughly, check gas coverage, verify gas purity. Cracking: use correct filler metal, control heat input, pre-heat thick sections. Burn-through: reduce amperage, use pulse, improve fit-up. Distortion: clamp properly, sequence welds, control heat input. Lack of fusion: increase amperage, slow travel, clean oxide.
Quality Control for Aluminum Welding
Visual inspection for cracks and porosity. Dye penetrant testing for surface defects. Leak testing for sealed components. Radiography for critical applications.
Closing Notes on Aluminum Welding
Aluminum welding requires understanding its unique properties and proper preparation. At Fulei Metal, our experience ensures quality aluminum welds for international clients.
Filler Choice and Heat Control by Aluminium Alloy
Aluminium is not difficult because it is soft, but because of three properties that behave differently from steel: the oxide layer melts at a far higher temperature than the base metal, thermal conductivity draws heat away from the joint roughly three times faster, and the alloys used for extrusion and sheet lose strength in the heat-affected zone. The table below maps the alloys we see in sheet metal work to the filler and the control that matters most.
| Base alloy | Fusion weldability | Filler | The failure mode to design around |
|---|---|---|---|
| 1050 / 1060 | Excellent | 1100 or 4043 | Low strength in the as-welded condition; design to the annealed properties |
| 3003 | Excellent | 1100 or 4043 | Generally forgiving; distortion from high heat input on thin sheet |
| 5052 | Good | 5356 or 5556 | Magnesium loss if overheated; 5356 matches strength and anodising colour better than 4043 |
| 5083 | Good | 5183 or 5356 | Marine grade; keep interpass low to preserve corrosion resistance |
| 6061 | Fair | 4043 for crack resistance, 5356 for strength | Heat-affected zone softening: a T6 part can lose a substantial part of its strength adjacent to the weld |
| 6063 | Fair to good | 4043 or 5356 | Same HAZ softening, usually less critical because the alloy is used in lower-stressed sections |
| 2024 / 7075 | Not recommended for fusion welding | Not applicable | Hot cracking and severe strength loss; join mechanically or by brazing instead |
Preparation is where most aluminium problems start. The oxide has to come off immediately before welding, using a stainless steel brush kept exclusively for aluminium, or a chemical clean; a brush that has touched steel will deposit iron and cause corrosion later. A laser-cut edge carries the same oxide, which is why cut aluminium is not weld-ready. For sections above roughly 6 mm, a preheat in the 100-150 C range keeps the arc from fighting conductivity, while interpass temperature is held down rather than up, because every extra degree widens the softened zone.
Corrosion behaviour after welding deserves a specific note on 5xxx and 6xxx assemblies. Where a welded aluminium part will be anodised, the filler choice becomes visible in the finished surface, because the weld region anodises to a different tone from the parent material. ER5356 generally gives a closer match on 5xxx alloys, while silicon-bearing ER4043 tends to go darker. If appearance after anodising matters, it should be on the drawing, because it changes the filler we select.
Aluminum Welding: Common Buyer Questions
Should I specify 4043 or 5356 filler for 6061?
It depends which risk you care about. 4043, a silicon-bearing filler, is more resistant to hot cracking and is the usual choice where the joint is restrained. 5356 gives higher as-welded strength and a closer anodising match. If the part will be anodised, say so on the drawing, because the two fillers colour differently.
How much strength does a 6061-T6 part lose next to a weld?
Enough that the heat-affected zone, not the weld metal, usually governs the design. In practice engineers design to the annealed or T4 properties in that region rather than to T6. If the drawing calls out T6 strength across a welded joint, it is worth revisiting before it reaches the shop.
Why do aluminium welds crack along the centreline?
Centreline cracking is usually a combination of restraint, a wide root and a filler that does not dilute the base alloy enough. ER4043 is the standard remedy for 6xxx alloys, along with a slightly convex bead profile and a crater fill at the end of the run.
Questions about a specific part are usually faster to answer against the drawing — send it through the route below.
About these figures. The reference values above come from our own production range; send the drawing for review lists the machines and materials behind them, and welding distortion control explains the adjacent steps that change the result. For your own part, sheet metal welding service is the fastest route to a quote — the earlier we see the drawing, the more of it can still be adjusted without cost. The tolerance context is set out in weld joint types and selection.
What stands behind this quotation
- Manufacturing since 20162,500 m² Ningbo plant — 3 laser cutting machines (including newer TRUMPF), 4 CNC press brakes and 10 welding stations.
- Shipped to more than 30 export marketsEnclosures, cabinets and formed parts supplied to OEM buyers across Europe, North America and Asia.
- 123 documented product casesMedical device housings, HVAC and heat pump enclosures, agricultural and livestock equipment, industrial hydraulics, material handling trolleys and EV charging cabinets.
- Factory evidence you can checkTUV Rheinland audit reference MIC-ASI243729 and Bureau Veritas reference MIC-ASR263630 available for buyer review on request.
Before you send drawings: project confidentiality is default · first-article inspection is carried out before a batch continues · pricing is staged from prototype quantity to repeat volume · pre-shipment photos and packing records are prepared when the project needs them.