Welding aluminum is tough. Aluminum’s higher thermal conductivity, lower melting temperature and oxide coating can lead to welding problems. TIG welding is one of the most common processes for aluminum. Because the operator is in such control with TIG welding, it can help lead to high quality. However, TIG welding aluminum tends to be one of the harder welding processes to perform because the operator has to control so many variables at the same time, such as the heat input, angle of the torch, travel speed and addition of filler metal.
One shop that knows about TIG welding aluminum well is Out Back Aluminum Welding, which performs aluminum pontoon and other boat repair work in the Lake of the Ozarks region in Missouri. After learning about welding from his father, Garry Euler launched the business in 1997 with one welder. Looking for work, the surrounding marinas advised him to focus on welding aluminum.
As the business grew, Garry’s son Darryll, who was interested in welding from a young age, eventually joined. Leading into the fourth generation, Darryll’s oldest son is starting to utilize his welding skills, as well.
A commitment to quality work has contributed to the success of Out Back and its continued, steady growth. One of the reasons for this success is its use of Miller Dynasty TIG welding equipment, specifically the Dynasty 280, 200, 350 and 700. The welders provide Out Back with the performance and portability it needs for TIG welding aluminum on pontoon boats – in the shop or out in the field.
TIG welding equipment with advanced features like those offered by the Dynasty series provides greater TIG welding aluminum success. Andrew Pfaller, product manager with the TIG Solutions group at Miller Electric Mfg. Co., explains the challenges that welders can face.
“When you are welding aluminum, you have to put a lot of heat into the workpiece quickly in order to establish a weld puddle,” Pfaller says. “If you try adding heat too slowly, you heat the area around your weld so when your puddle starts to establish, it tends to grow very quickly. So that is where the benefits of new inverter-based welders start to come in.”
Warpage can be a big issue when working with aluminum. And Garry and Darryll know those issues first-hand.
“You really have to be aware,” Darryll says. “No matter the thickness, every time you weld aluminum it shrinks, causing bending and movement. So you have to watch your heat input and take a step back to allow the weld area to cool properly.”
He notes that most aluminum on pontoon boats is around 0.090 to 0.100 in. Smaller parts can be as small as 0.060 in. For many repairs, material that is 3/16 in. is added.
The Dynasty welders allow Out Back to adjust the AC frequency to focus the arc into a smaller area, which means driving more heat into that area. This allows the weld puddle to be established more quickly so it is more controllable.
Another feature Dynasty welders offer is AC waveshape, which offers four waveforms.
“In addition to controlling the arc, we offer secondary benefits from the way we control the wave shape,” Pfaller says.
The advanced square waveform offers the most aggressive arc. This allows a welder to add a lot more heat in a shorter period of time.
“Using that waveform and focusing with the AC frequency, you get more heat into the workpiece much more quickly than traditional sinusoidal or transformer-based welding equipment,” Pfaller says.
However, the advanced square creates a harsh tone from an audible standpoint. The soft square waveform greatly reduces that harsh noise while still offering benefits such as fast heat input and good directional control.
“It’s a good all-around product and that is what most of our equipment goes out with as the standard setting,” Pfaller says.
The sine waveform offers a slower arc and is for heating a larger work area, such as surfacing on a piece of aluminum plate. “The waveform mimics how traditional welding equipment works and does not really provide the benefits of why you would buy an inverter,” Pfaller says.
The triangular waveform is generally used on thin aluminum. Due to the nature of the waveform, there is not a lot of heat but there are still brief periods of higher amperage. Amperage drives penetration so the operator can get the penetration he needs, but less heat helps control the weld puddle on thin aluminum.
Balance control – referring to the amount of time spent in electrode negative and the balance of the time in electrode positive – is a feature most welders have. In electrode positive, more cleaning of oxides off the aluminum surface occurs, while electrode negative has traditionally been known as the heating or welding portion of the cycle.
“Being able to separate the positive from the negative side allows us to go way deeper and still make it work on the side we need the cleaning on and still keep the weld looking good,” Darryll says.
It should be noted that while balance control helps with cleaning oxides off the surface, it does not take the place of proper material prep. It is only to aid in fine tuning how much oxide removal action the welder is providing in the arc.
Cleanliness, however, isn’t the only benefit to balance control. It can also be used to maintain tungsten electrode geometry.
“Traditional welding equipment didn’t have the ability to adjust the balance as far as the welders of today,” Pfaller says. “That meant it put a lot of heat back into the tungsten, which melted it and gave it a balled up shape. This affected arc performance and the ability to focus it into a small area.”
With newer inverter welders, the operator can adjust the balance setting to significantly reduce the melting of the tungsten, maintaining the shape ground onto the tungsten electrode prior to welding. Maintaining that shape helps the operator focus the arc in the area he wants on the workpiece.
According to Pfaller, another benefit of an inverter welder is that “it’s more efficient at processing power that you pull off of the wall and delivering that power to the workpiece in the form of heat so you don’t need a draw as much electricity off of the wall.”
“It doesn’t use that much electricity because of the inverter technology,” Garry adds. “So your electric bill is actually substantially less for your arc time.”
Proper electrodes and gas
For TIG welding aluminum, it’s common to start with a blunt tip on the tungsten electrode. “We recommend a truncated tip,” Pfaller says. “Grind the electrode to a point and then knock the tip off of the point. Putting a blunt end on the tip, up to a third of the diameter of the electrode, can help focus the heat more effectively.”
He adds that traditionally with TIG welding aluminum the operator had to melt a ball on the tungsten up to 1 1/2 times the diameter of the electrode, which made it uncontrollable and tend to wander around. While becoming less common with the inverter technology, a few operators still feel the need to ball the tungsten up and weld like they did with traditional welding equipment, which does not allow them to take full advantage of what the technology can provide and is, therefore, not recommended.
The filler metal used with TIG welding aluminum is dependent on the base material. Many aluminum alloys are available, but typically 6061 is the base material and the two common filler metals are 4043 and 5356.
A number of factors need to be considered for the filler metal such as if the part will be anodized or going into a high-temperature application, color matching importance, strength and flexibility, corrosion resistance and impact toughness. Filler metal charts provide the best way to decide which one fits the job.
While Out Back does TIG weld 6160, the aluminum used for pontoon boat logs and hulls is 5052. “We use 5356 almost exclusively on the sheet goods stuff,” Garry says. “It’s stronger and harder than 4043.”
For buildup on castings and casting repair, Out Back uses new Hobart MaxalTig 4943 rod in place of 4043. “This 4943 is the stuff,” Garry says. “For our specific needs, the 4943 is stronger and harder to bend than 4043. It is a good match for the 356, which is what most castings are made from.”
He notes that 356 is almost the same chemical makeup as 6061, and Out Back uses 4943 for 6061 as well. The extrusions on the pontoon boat, such as the cross members, are 6061.
Typically, 100 percent argon gas is preferred for the shielding gas for TIG welding aluminum. Some operators still use helium because it provides certain characteristics they need for their operation. Pfaller notes one aspect operators struggle with regarding shielding gas is the gas flow rate.
“A lot of people think that more shielding gas is better,” he says. “So they will turn their gas flow up, which can cause almost a Venturi effect – think of a carburetor in an old sports car – causing oxygen to be sucked in the shielding gas stream. Having too high a flow rate can actually hurt you more than possibly having a lower flow rate.”
According to Miller, a good starting point is 15 to 20 cubic feet per hour for most applications. The gas flow rate might be higher for higher amperages or a bit lower if the application suits it.
“But, if you are hearing the air really rushing, you know it’s probably too high,” Pfaller says.
One big challenge Out Back faces with TIG welding on boats is accessibility. “A lot of people want the repair done right there on their boat lift,” Darryll says. “But many times to make the repairs properly, we have to do it in the shop. Typically, what looks like the problem, where it is leaking, is just a symptom. So we dissect that general area to discover the real cause of the problem, and weld the damaged area and then weld it all back together. We can’t do those repairs over the open water.”
Garry notes that what makes Out Back stand out is aesthetics. They have the ability to make welds that are beautiful – “that row of dimes everyone looks for.”
Aesthetics isn’t all that Out Back is known for, though. The company also has a reputation for solving problems.
“We’re known for re-engineering or improving parts that break all the time,” Garry says. “We want to make it better than it was when it came from the factory. With aluminum, manufacturers tend to use thinner materials because they are thinking lightweight rather than what will hold up in the real world with every day use. We go in and change it to what we think it should have been in the first place so we don’t have to fix the same issue twice.”
Garry notes that Miller helps them with more than just equipment. “They provide the support, advice and warranties,” he says. “None of their features are fluff. They aren’t playing catchup. They are leading their industry.”