How to Weld Aluminum - Learn To Weld Aluminum

TIG-welding aluminum is done with AC current, rather than DC, which is used to weld steel. Use pure argon as the shielding gas and set the regulator to flow about 15 to 20 cfm. Set the machine to about 110 amps and adjust as needed. Miller's website, millerwelds.com, has a good interactive chart to help you dial in your settings based on the materials and types of joints you're doing. Also check all the connections at your machine. Chancy told us to never take the machine settings for granted. Bad power or ground connections at the welder can be easily misidentified as other problems and you can spend lots of time trying to figure out what you're doing wrong.

Clean the aluminum thoroughly with a stainless steel wire brush and make sure that brush is only used for aluminum, otherwise you risk contaminating your weld. After brushing, wipe the piece with acetone. Rubbing alcohol can be used in a pinch, also. Do this right before you're about to start welding. The oxide layer begins to re-form on the surface of the aluminum in less than 20 minutes.

Set up the torch with about 1/8-inch stick-out, literally how far the tungsten sticks out of the opening in the gas cup, hold the torch in a nearly vertical position about 3/8 inch above the work surface, and maintain that position as you travel across the joint. Of course, different joints require slightly different torch angles and stick-out.

Strike your arc and watch closely for the aluminum to start to melt. Unlike steel, aluminum does not change color as it melts. Instead, you'll see it turn a dull gray and then get very shiny, almost like a mirror. It liquefies right after that. When the puddle forms, dip the filler rod into the puddle and move to the left (if you're right-handed), maintaining enough heat to keep the puddle intact. It's a delicate balance of amperage, torch angle, and travel speed. Chancy likens the torch to a heater and the filler as the coolant. He recommends beginners keep a mental count as they learn the proper rhythm. Perform this dip/move pattern at roughly two-second intervals, traveling about 10 inches per minute. As you reach the end of the joint, reduce the amperage (heat) and feed slightly more filler rod; there is less area for the heat to go at the edge of the joint, and it's easy to burn a hole in the end of the bead.

If the weld puddle cools too quickly, a crater will form in the final bead as it solidifies. Craters are bad because that's where any cracks that can develop in the piece will appear. To prevent this, be sure the bead cools slowly. Ease off the pedal to reduce the heat at the end of the pass and simultaneously add more filler than normal. The extra filler and lower temperature will cause the weld to cool sufficiently enough to not form a crater.