Here are three gas flow adjustments that stop weld cracking on aluminum tube lines.
Adjustment 1: Increase Shielding Gas at the Weld Box
Aluminum is sensitive to oxygen. Even a tiny amount of air in the weld zone creates aluminum oxide in the seam, which is brittle and cracks under the cooling stress. Most aluminum tube lines run argon at 15-20 liters per minute. If you see soot or discoloration near the weld, bump the flow to 25 L/min. Also check for drafts—an open bay door can blow away your shielding gas. A simple cardboard shield around the weld head works wonders.
Adjustment 2: Check Gas Purity
Not all argon is the same. “Industrial grade” might be 99.8% pure. That 0.2% of oxygen, nitrogen, or moisture is enough to contaminate an aluminum weld. Switch to welding-grade argon (99.997% pure) on your aluminum tube line. The cost difference is small. The crack reduction is large.
Adjustment 3: Adjust Tacking Gas Before the Main Weld
On a steel tube mill machine, you don’t worry about tack welds. Steel forgives. Aluminum doesn’t. The pre-heat or tacking stage before the main weld needs its own gas shield. If your aluminum tube production line uses a tack welder or a pre-heat inductor, make sure it has separate gas nozzles. No gas at tacking means oxidized edges going into the main weld. Those edges won’t fuse properly, and the seam will crack under the roll forming machine stress downstream.
One More Check
Look at your cooling section. If water or coolant drips onto the hot weld, thermal shock can crack an otherwise perfect seam. Shield the weld from coolant until the tube temperature drops below 200°C.
Your aluminum tube welds don’t have to crack. Adjust gas flow, check purity, shield the tack zone, and protect the hot seam from coolant. Your scrap pile will shrink, and your steel tube mill machine operator will stop complaining about aluminum dust in the forming rolls. Run clean, weld clean, stay crack‑free.
