Controlling heat input is key for welding aluminum. If you’re MIG welding aluminum, the transfer mode being used affects the type of problems you may see and, ultimately, your success.
Short-circuit transfer should be avoided on industrial aluminum applications. Unlike when welding steel, conventional short circuit is much more problematic when welding aluminum. As the weld solidifies quickly, it leads to increased lack of penetration/fusion problems as well as increased porosity levels. This is due to the fast-freezing weld pool of aluminum compared to steel.
While thicker sections of aluminum are often welded successfully with conventional MIG spray transfer, thin-gauge aluminum offers little room for error. This is where pulsed MIG can deliver significant benefits.
Pulsed MIG is a modified spray transfer process in which the power source switches between a high peak current and a low background current between 30 to 400 times per second. During this switch, the peak current pinches off a droplet of wire and propels it to the weld joint. At the same time, the background current maintains the arc but has such a low heat input that metal transfer can’t occur. This action differs from a standard spray transfer process, which continuously transfers tiny droplets of molten metal into the weld joint. It also allows the weld puddle to freeze slightly to help prevent burn-through.
Pulsed MIG welding can also allow for faster wire feed and travel speeds while simultaneously reducing heat input and lowering the opportunity for distortion. It provides good directional control over the weld puddle and the ability to control the bead profile.
Learn more about pulsed MIG in this article.