A perfect TIG Weld takes patience and practice.
Your Guide to Achieve High-Quality Welds that Look as Good as They Perform
Aluminum is often the favored metal for manufacturing products. It is most known for its low weight to size ratio and performance in cold temperatures. This makes aluminum well-suited for use across a broad range of industries and applications. From boat components to HVAC piping and automotive applications, aluminum often reigns supreme. In this guide, you will learn the ins and outs of how to TIG weld aluminum.
Yet, despite these overwhelming benefits, TIG welding aluminum is wrought with challenges. Handling oxide layers and controlling heat input can be difficult.
When it comes to aluminum welds, Gas tungsten arc welding (GTAW) has long been the preferred approach. GTAW results in a unique combination of aesthetics and weld integrity.
This guide will provide you with the fundamentals and best practices necessary to achieve a high-quality result when TIG welding aluminum.
Follow these strategies and you’ll be TIG welding aluminum into the much-admired ‘stacked dimes’ appearance in no time.
How to TIG Weld Aluminum: The Challenges of GTAW
GTAW certainly isn’t the approach welders take if time takes precedence over appearance and quality. Due to its laborious nature and time-consuming process, GTAW is not commonly found in high production applications or facilities. However, it remains one of the best options for TIG welding aluminum.
Using gas tungsten arc welding enables the welder to precisely control the release of filler metal. This controlled release enables welders to control the puddle and achieves an ideal level of penetration prior to the addition of filler metal.
TIP: With greater control comes a higher chance of welder error, requiring more skill than would be necessary for a GMAW weld.
A precise GTAW takes more practice than a GMAW weld.
Why not Use Gas Metal Arc Welding (GMAW)?
GMAW has its own downsides. Most importantly, GMAW is known as a ‘cold start’. This means the immediate application of filler metal is released with the squeeze of the gun trigger. This practice often results in a lower quality of fusion and reduced penetration.
The Right Temperature: A Mission-critical Aspect of GTAW
TIG welding aluminum with GTAW requires just the right temperature, and aluminum doesn’t make this easy. Due to its relative conductivity, the level of heat achieved in the weld puddle can quickly dissipate as it’s pulled away. Because of this, the weld puddle must be established with an excessive amount of heat. Simultaneously it needs to be controlled to prevent burn-through or a wandering puddle.
Remember, heat is the result of voltage and amperage. When TIG welding, the greater the arc voltage, the greater the power transferred to the metal.
TIP: A longer arc will indeed result in greater voltage, and as a result, an increase in heat. However, this also results in heating a larger surface area on the target, increasing the chances of having your puddle get away from you. By contrast, a little patience with a shorter arc will allow you to localize the heat and prevent runaway puddles.
Use a shorter arc to localize heat and prevent runaway puddles.
The Right Polarity Matters: A Lot
Those with little TIG welding aluminum experience often fail to realize that this process generates a layer of oxide. This is significant for a couple of reasons. One, this oxide layer (aluminum oxide) has a melting point that measures around three times that of the base material. Secondly, oxidation on aluminum typically results in a dull silver-like color that is more difficult to identify.
Prior to welding, aluminum should be inspected for any oxidation or oxidized layers. If noted, this oxide layer should be removed with either a carbide cutter or stainless-steel wire brush.
TIP: Despite steps taken to properly prepare the surface of the aluminum, oxidized layers will often reform quickly. These layers obstruct your line of sight with regard to the weld puddle. To overcome this challenge, utilize AC polarity and GTAW when working with aluminum. This strategy results in a current flow that is in a state of constant alternation. The AC polarity acts as a cleaning agent to remove any oxide layers that form.
Making Adjustments for Balance Control
Every good TIG weld of aluminum requires making adjustments for optimal balance control. Welding in AC polarity results in both an EP (electrode-positive) and an EN (electrode-negative) cycle.
EP is ideal for removing or cleaning up any oxide formation. The EN part of the cycle is typically best for making the weld.
Most modern TIG welding equipment will feature a balance control module. This enables you to make adjustments to the ratio of EN and EP as you see fit.
TIP: Older equipment without such control is usually factory set to a true balance of 50:50. Modern equipment, by contrast, usually comes preset to a balance of 75:25 (EP to EN).
TIP: The appearance of black specks or flakes (known as ‘peppering’) in the weld puddle is indicative of a poorly adjusted balance control. In order to reduce this peppering effect, adjust the ratio of EN to EP so that there is more EP and less EN.
TIP: When working with welding material that has been exposed to the elements you may need to adjust the EN down. This will establish a better clearing action. However, be advised that doing so will end up transferring more heat to the tungsten. This often causes the tip to ‘ball back’, impacting arc placement and direction.
Setting the AC Output Frequency
The output frequency of your unit refers to the number of times (per second) that your source of power alternates polarity. Modern equipment is generally set to an output frequency of 120-Hz, while older power sources are often standardized to 60 Hz.
The greater the output frequency of the AC, the more stable your arc will be. This results in a narrower arc column and greater control. This is especially important when TIG welding in tight spaces and/or where precision is of high importance. To achieve a tighter cone and more accurate placement, adjust the AC frequency to between 150-250 hertz. Alternatively, there are cases where a wider arc cone may be ideal. Attempting to weld an outside corner joint is one such case. To achieve this, simply turn down the AC to between 80-90 hertz.
TIP: When working with thicker materials (3/8” or thicker), a lower AC frequency between 80-120 hertz is ideal.
Higher AC frequency will result in a tighter cone and more accurate placement.
Using the Appropriate Amperage
When using GTAW, it is always advisable to set the maximum amperage on your equipment prior to use. The amperage setting is typically controlled by either fingertip control or foot pedal during use.
TIP: A good standby if uncertain, is to use 1 amp for every 1000th (0.001) of thickness.
TIP: As your target material gets thicker, you may deviate from the 1 amp per 0.001” of thickness rule. Less amperage is typically necessary for thicker materials.
TIP: Another factor that can affect the ideal amount of amperage is joint geometry. For example, a T-joint usually requires more heat due to the tri-directional flow of heat.
Independently Setting the AC Amperage
This feature, available on some modern-day power sources, enables you to adjust the AC amperage independently. The benefit of this feature is that it assists you with achieving improved penetration as well as efficiency.
When available, this option allows you to make changes to the amperage during the EN segment of the cycle. This results in enhanced weld penetration.
TIP: Independent amperage settings are more often seen with higher-amperage applications.
Achieving the ‘Stacked Dimes’ Look with Metal Filler
When using GTAW with aluminum welds, adding metal filler is a simple way to accomplish the oft-desired ‘stacked dimes’ appearance on your welds.
The addition of ‘filler’ metal results in a cooling effect on the opposite side of the weld puddle. This produces a favored aesthetic appearance on the finished product. Use less filler for a smoother appearance, and more for an increasingly pronounced ‘stacked’ look.
A perfect example of the 'stacked dimes' appearance.
Final Thoughts: Always Take a ‘Safety First’ Approach to Your Work
GTAW is generally a ‘clean’ welding process. This results in little to no splatter when done right. However, personal protective gear should still be worn at all times.
When TIG welding aluminum, always wear proper gloves, glasses, a welding jacket, and a welding helmet. Remember, given aluminum’s reflexive qualities, the intense arc can and will cause sunburn to any exposed skin.