Tungsten Inert Gas (TIG) welding—more formally known as Gas Tungsten Arc Welding (GTAW)—is well-suited for welding aluminum. Although the process is significantly slower than GMAW (MIG), TIG welding offers unmatched control of weld penetration and profile. This level of control is enhanced by the features available on modern TIG welders.
Preparing to Weld
Even with modern equipment, welding aluminum is very much like painting: preparation is key. The cause of a lot of headaches when TIG welding aluminum is related to aluminum oxide. This protective oxide layer has benefits for parts in service but must be removed from around the weld joint by using a stainless-steel wire brush—one dedicated to aluminum only—prior to welding. If not removed, the oxide layer may limit weld fusion and overall control in the welding process.
The aluminum oxide layer is also well-suited to trapping and retaining moisture that becomes a source of weld metal porosity. For this reason, preventing condensation formation on both the base metal and filler metal is also critical to achieving good quality. At the very least, allow filler metal and base metal to thermally acclimate to the welding environment before use. Consult with filler metal manufacturers to learn more tips about how to combat porosity when welding aluminum.
“The aluminum oxide layer is also well-suited to trapping and retaining moisture that becomes a source of weld metal porosity.”
Pure tungsten electrodes were once the industry standard for TIG welding aluminum since these electrodes formed a nice “balled” tip that performed well when using alternating current on older transformer-based equipment. However, ceriated tungsten electrodes have become the norm with newer inverter-based power sources. Preparing ceriated tungsten for welding aluminum involves simply grinding the end of tungsten to a point at a 60-degree angle, give or take depending on the desired arc cone.
A Power Source for Everyone
With the right shielding gas and sufficient amperage, it is technically possible to TIG weld aluminum with a power source that is capable of direct current (DC) only, but the job is significantly easier when alternating current (AC, the industry-standard) is employed. Likewise, it is possible to weld aluminum using older transformer-based equipment, but ease of use may be lacking compared to modern inverter-based equipment that typically offers additional features in addition to reduced weight and improved electrical efficiency.
Whether you are a home hobbyist or an industrial fabricator wanting to remain on the cutting edge of technology and productivity, the welding marketplace has appropriately sized equipment loaded with features that satisfies the needs of your particular use case.
“Sizing-Up” Equipment Specifications
Consider the following specifications of the Miller Dynasty 200 AC/DC power source:
- Input Power: 120-480V, 3- or 1-Phase Power
- Amperage Range 1-200 A
- Rated Output: 200 A at 28V, 20% Duty Cycle
Input Power
The ability to use 120-240V 1-phase service can be very useful to the hobbyist welder but also an important consideration when the equipment is to be powered with engine-driven equipment for field repairs.
Amperage Range
The maximum thickness that can be welded is the result of several factors that includes base metal preparation and welding amperage. A range of 1-200 amps provides a lot of potential in the aluminum welding world and should be well suited for welding up to 1/8”-thick material in a single-pass.
It is possible to weld greater thicknesses with this power source, but multiple passes and/or joint preparation should be employed. TIG welding aluminum typically requires the use of wider included angles (more preparation) than steel to achieve adequate fusion. Suggestions for aluminum TIG welding settings and joint preparation can be found from a range of sources such as technical documentation available from equipment and filler metal manufacturers.
Rated Output & Duty Cycle
When choosing a power source, consider the time you have available to accommodate for both duty cycle downtime and base metal preparation. Larger power sources may provide improved duty cycle at the desired amperage, which is attractive in mechanized and high-productivity applications. Larger power sources can also allow thicker aluminum to be welded in fewer passes and with less base metal preparation, both of which can be a significant source of non-welding time. Higher-amperage operation typically requires the use of larger tungsten as well as water-cooling for both the torch and power source.
Features for Aluminum Welding Success
High-frequency starts are a standard option among most TIG welding power sources since this feature greatly improves the process of arc initiation when welding aluminum. However, modern TIG welding equipment has much more to offer. Consider some of these features—a list that is by no means exhaustive—to help custom tailor the welding process to your application:
- Square Wave AC: Improves overall arc stability compared to conventional sine-wave AC by reducing the time spent in the low-amperage “crossover region” between Direct Current Electrode Positive (DCEP) and Direct Current Electrode Negative (DCEN).
- Balance Control: Allows preference of DCEP or DCEN in the AC cycle allowing a greater percentage of the cycle to be spent on that polarity. Emphasizing DCEN polarity helps to maximize weld penetration, while emphasizing DCEP polarity helps to maximize the “cleaning” action of the alternating current.
- Frequency Control: allows an increase or decrease in the number of alternating current cycles per second. Increasing the frequency narrows the arc cone, which can be beneficial for fine tuning the weld bead width and profile.
- Pulsed Current: high current “peaks” can be used to obtain desired penetration for improved travel speeds while background current “valleys” help to keep overall heat input low, preventing burn-through and minimizing distortion.
Successfully TIG welding aluminum is all about preparation: of the welding procedure, of the base metal, and of the welding power source. Red-D-Arc offers a complete line of TIG welder rentals that offer the specifications and features you need, regardless of your application. Contact the pros at Red-D-Arc to learn more about what is new in the welding marketplace and how it can help make you make welds easier, better, and faster.
