Aluminum Etc.: Temperature control in welding aluminum is key

Aluminum requires a lot of heat—almost twice as much as steel—to raise its temperature enough to get a puddle. Being able to control heat is the key to successful aluminum welding. Getty Images

If you are embarking on an aluminum project but your comfort zone is working with steel, you’ll quickly realize that everything you know about welding steel successfully will not work when applied to aluminum. It can be very frustrating until you understand some of the main differences between the two materials.

Aluminum requires a lot of heat—almost twice as much as steel—to raise its temperature enough to get a puddle. It has one of the highest thermal conductivity rates. Even though aluminum can take a lot of heat and still remain a solid, that doesn’t mean you should crank up the voltage and hope for the best when welding. You need to follow a set of parameters to achieve the desired results.

Heat and Temperature Control in Welding Aluminum

An easy way to dial in your machine is to increase or decrease the voltage by 5 until you get a shiny-wet puddle within three seconds. If you achieve a puddle in one or two seconds, decrease your voltage by 5 until it happens within three seconds. No puddle within three seconds? Increase the voltage by 5 until you do.

At the beginning of your TIG weld, you’ll need to push down fully on the foot pedal to generate enough heat, but as you start to make your fusion, you’ll need to back off the foot pedal by as much as half. Watching your bead profile will give you visual indications of how much foot pedal pressure you’ll need. If you are using scratch-start (stick welding), you will have to allow the material some time to heat up at the beginning of the weld before you are able to fuse it successfully.

When I am teaching someone, I explain it by saying they need the lowest voltage setting that gives them the best working temperature. Too much heat will likely cause cracking in the weld, oxide inclusion, softening of the heat-affected zone, and porosity—all of which degrade your material and affect the quality of your weld, both structurally and cosmetically.

By having complete control of the heat input, you can regulate and hopefully eliminate these common problems.