Master the challenges of welding aluminum. Learn about cleaning, joint preparation, parameter selection, and techniques for TIG and MIG aluminum welding.
Introduction
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
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.
Parameters
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.
Common Problems
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
Visual inspection for cracks and porosity. Dye penetrant testing for surface defects. Leak testing for sealed components. Radiography for critical applications.
Conclusion
Aluminum welding requires understanding its unique properties and proper preparation. At Fulei Metal, our experience ensures quality aluminum welds for international clients.