Ensuring success before striking an arc
May 25, 2012
The push for lighter, corrosion-resistant components has brought aluminum to the forefront of the minds of traditional steel fabricators. Those that approach the material the same as steel often run into weld quality issues that can prove costly. But those who are committed to putting together a topnotch, aluminum-friendly system before striking an arc—from equipment and setup to material preparation and welder education—are better equipped to find success afterward.
What is it about aluminum? The mere mention of welding it causes even the most experienced and talented welders to shake their heads and mumble things like, “Aluminum is a whole other animal.”
The push for lighter, thinner, corrosion-resistant components has brought aluminum to the forefront of the minds of traditional steel fabricators.
“There’s definitely a movement toward thin-gauge, lightweight materials in a lot of different segments, said Wes Doneth, manager tech support USA at Fronius USA LLC. “I would say that roughly 70 percent of the test plates we do are aluminum.”
Those who approach the material the same as they do steel often run into weld quality issues that can prove costly. But those who are committed to putting together a topnotch, aluminum-friendly system before striking an arc—from equipment and setup to material preparation and welder education—are better equipped to find success afterwards.
The rules for welding aluminum are, for the most part, completely different from the rule for welding steel. It’s a hard concept for some to grasp, especially those with extensive training and experience welding steel, said Matt Albright, product manager for welding equipment at The Lincoln Electric Co., Cleveland. But the biggest mistake, he added, is when fabricators don’t fully embrace the nuances that make aluminum welding different than steel welding.
“People approach it with the same techniques they would use to weld steel, and you just can’t. With steel it doesn’t matter if the gun cable is old or twisted in a knot, the grounding path so-so, the gas coverage marginal, the material dirty or the wire greasy. With all of that said, you can still achieve an acceptable weld. But with aluminum that’s just not the case.”
A few things that make aluminum unique is its lower melting temperature compared to steel’s, the oxide layer, and the metal’s ability to draw heat away from the weld quickly.
Some of the other elements that make aluminum different, Doneth added, are the heat input, cleaning methods, and welding techniques.
“Some of the methods that you use to clean steel don’t apply to aluminum. On steel, fabricators are used to just hitting it with a grinder. Well, if you don’t do it correctly on aluminum, you can actually just bury the contaminants. You have to use more of a cutting method to remove the oxide layer from the plate.”
Understanding and indentifying the elements that make aluminum different is only half the battle. The next step is to implement a system—everything from the power source to contact tips, cable setup, gun, and material preparation procedures—that yields a weld with optimum penetration without defect. To do that, however, requires the full commitment of a fabricator’s time and resources to cater specifically to aluminum. Any less of a commitment, said Albright, will not produce the desired results.
“I visited an aluminum welding customer that was experiencing problems with their system. I opened the wire feed and saw that they had a steel drive system in there; they had the spindle crank down so tight that I needed a pair of pliers just to get it open. It’s no wonder they were having issues,” Albright said.
“You have to really get your arms around all of the nuances that are involved with aluminum, and people don’t do that.”
Keep in mind that the system components work in unison, and the system is only as strong as its weakest link.
“You could have a sweet power source and a bad gun; you could have an awesome power source and a good gun and a bad feeder. If there’s something wrong with a component, it is made more obvious in an aluminum setup,” Albright added.
Here are a few things fabricators need to keep in mind for their aluminum welding setup.
Material. Moisture, grease, oxide, and other contaminants must be removed properly before welding. Skimping on these tasks could lead to porosity or costly weld defects.
“If you have moisture on the surface, it makes a huge difference. With the aluminum oxide you risk not even penetrating the plate, and it will cause a lot of porosity in the weld,” said Doneth
Wire feed. As Doneth explained, aluminum wire is soft. Fabricators that use push-only guns can do so successfully as long as the torch cable is relatively short. In general, he suggests a push-pull gun for better feedability.
“It’s absolutely critical that the drive motors be synchronized—you’ve got one at the front of the torch and one at the main feeder. You can damage the wire if the drive rolls slip, because it’s pulling too hard or not hard enough. If that is the case, the wire will crinkle, causing all kinds of feeding problems.”
Gun cable setup also plays an important part in wire feeding. Albright suggests mapping out the setup to allow the cable to lie in big, sweeping curves and safe from interference or being stepped on or run over.
Experience. A dedicated aluminum setup consisting of a state-of-the-art power source, a topnotch gun and wire feed system, and material that has been cleaned and prepared properly is a great start, but it’s not a magic bullet, said Albright. A successful aluminum application needs an experienced operator at the helm.
“If you have an operator who understands how to set up the system, dial in procedures, and how all of those factors weigh on their performance, then you have an operator that will be successful nine times out of 10,”Albright said.