In case you haven’t heard, the use of aluminum in car and truck bodies is drastically changing the collision repair landscape. Once reserved for only the most exotic, lightweight vehicles, automakers are increasingly turning to aluminum to improve the fuel efficiency of their most popular models. And as fuel efficiency regulations become more stringent, the use of aluminum will only increase.
There’s no need to worry about these changes, though, because welding aluminum is no more difficult than welding steel. You just need the right tools, training and a basic understanding of some of the differences between the two metals.
Difference #1: Aluminum acts differently than steel when welded.
The composition of aluminum makes it act differently than steel when welded. It has twice the thermal expansion of steel, and it also shrinks when it re-solidifies after being welded. These characteristics can cause cratering – when not enough filler material is added to the weld – and even cracking.
Fortunately, your welder can take all the worry out of the aluminum welding process. Advanced models like the Chief MultiMig 522 welder come with an automatic crater fill function. The MultiMig 522 and Chief MultiMig 511 feature synergic curves that preset weld parameters so users can start welding aluminum immediately, with little setup time or specialized training. Their synergic pulsed technology is required by most OEMs for aluminum welding because it reduces burn-through on very thin aluminum while providing full penetration through thicker aluminum sheets.
Difference #2: Aluminum wire is much softer than steel wire.
Steel welding wire is robust. In a traditional MIG welder, it can be “pushed” by the rotating feed roll all the way to the welding gun tip without collapsing on itself.
If you try to load aluminum wire into the same welder, you will likely end up with a jammed gun. That’s because softer aluminum wire will fold and tangle if it is pushed even a short distance. This forces the technician to stop welding and cut out the tangle, resulting in costly downtime.
Some of today’s aluminum-specific welders are available with push-pull torches that eliminate tangles and breakage. While these welders still push the wire from the reel, a secondary “pulling” feeder is located in the torch that maintains constant, uniform tension on the wire.
Difference #3: Aluminum conducts heat much faster than steel.
Aluminum’s thermal conductivity is six times that of steel, so it rapidly transfers heat away from the weld area. This can lead to incomplete fusion of the metal due to insufficient weld temperature. The most problematic area is often the start of the weld, where there is not enough retained heat in the material.
To prevent incomplete fusion, you may have to start your aluminum weld using a higher current than is necessary for the rest of the weld. This will quickly heat the metal up to a proper temperature.
When shopping for an aluminum welder, look for a torch that allows you to increase and decrease current on the fly, or a cold-start feature that eliminates any guesswork.
Keep these three differences in mind as you prepare your shop for welding aluminum on the vehicles of today and tomorrow. With the right equipment, the transition will be quick and easy.