5 Tips for Improving GTAW Efficiency

Knowledge, training, and practice will lead to high-quality welds

Even though the gas tungsten arc welding (GTAW) process is relatively slow, it is also very versatile. In addition to being able to weld aptly on thin materials (due to its low heat input), it can be used to weld more materials than any other welding process, even exotic and heavily alloyed metals. The GTAW process also produces high-quality, aesthetic welds. Achieving these advantages, however, isn’t always easy. It takes training, practice, and a bit of know-how.

Consider these tips for improving GTAW efficiency and obtaining good welding performance with the process.

Tip 1: Use an inverter power source

Inverter power sources provide precise arc-starting capabilities and include advanced output controls, such as pulse and AC parameter adjustments, that allow you to fine-tune the welding output for your desired results.

The frequency feature on an inverter power source helps improve welding efficiency by narrowing the focus of the arc. This feature, in turn, creates a narrower weld bead, minimizes the heat-affected zone (HAZ), and reduces the risk of distortion or burn-through. These machines also allow for faster travel speeds and require less time and filler metal to complete a weld.

Inverter power sources also feature better AC balance controls that precisely control the amount of cleaning action the arc generates. This feature is especially useful when welding aluminum. Fine-tuning the cleaning action puts more heat into the work for faster travel speeds and longer tungsten life.

Tip 2: Select the right GTAW torch

Determine whether an air- or water-cooled GTAW torch is best for the application. Air-cooled models are better for applications below 200 amps and for welding very thin materials (less than 3/16 in.). Air-cooled GTAW torches are also portable because they do not require an external cooler, making them a good option for welding in multiple locations.

For applications higher than 200 amps, use a water-cooled GTAW torch, as it helps prevent overheating and allows for increased travel speeds.  A water-cooled torch also works well for more delicate work, because it is smaller than an air-cooled model and offers better dexterity and control.

Consider the type of joints and angles that you need to weld. Most GTAW torch manufacturers offer models with flexible necks that are good for welding in particularly tight joints or awkward positions. Some torch body styles also have a modular design, which allows a flexible neck and different head angles to be added. These kits may help you gain better joint access and lower downtime associated with changing over different torches for multiple applications. Plus, they minimize the cost of purchasing and maintaining inventory.

Tip 3:  Use a gas lens

A gas lens allows you to extend the tungsten electrode farther from the nozzle to gain better visibility of the joint and arc. This electrode extension also helps provide greater torch control and better weld quality, especially on critical applications and hard-to-reach areas such as T, K, and Y joints.

A gas lens is particularly helpful for GTAW on alloys that are highly reactive to atmospheric contaminants or on materials used in high-temperature applications. They also can be used with all types of shielding gases and are available for both air- and water-cooled torches.

GTAW Lens

Figure 1

The gas lens replaces the collet body in a torch to hold the tungsten in place. It also creates the electrical contact necessary for proper current transfer. Most gas lenses contain a copper and/or brass body with layered mesh stainless steel screens that help distribute the shielding gas evenly around the tungsten and along the weld puddle. This even shielding gas flow protects against contaminants that could lead to weld defects and downtime for rework.

Tip 4: Use the correct tungsten electrode size, type, and shape

To ensure consistent arc starts, and prevent arc wandering and related problems, follow these steps when selecting a tungsten electrode.

First, take into account the power source being used for the application (whether it is a conventional or inverter machine), as this will determine the shape of tungsten electrode to use. Next, consider the base material, which will determine the type of tungsten electrode to use, along with the welding amperage and material thickness. The latter determines the appropriate size tungsten electrode for the application. (see chart).

For grinding and preparation, use the following guidelines:

1. Grind the tungsten electrode on a borazon or diamond grinding wheel specially designated for the purpose (see Figure 1), or use a tungsten grinder.

2. Grind the taper on the tungsten electrode to a length of no more than 2.5 times the electrode diameter (for example, with a 1/8-in. electrode, grind a surface 1/4 to 5/16 in. long).

When grinding tungsten electrodes, be sure to control and collect the dust; have an adequate ventilation system at the grinding station; and follow the manufacturer’s warnings, instructions, and material safety data sheets.

A pointed tungsten electrode works well when welding with lower amperages on thin materials (0.005 to 0.040 in.), because it allows the welding current to transfer in a focused arc that helps prevent distortion. Pointed ceriated tungsten electrodes in particular work well when welding aluminum using an inverter power source; they provide 30 to 40 percent more amperage capacity than pure tungsten electrodes before beginning to melt. This shape also provides the stable arc needed to achieve good welding performance and quality.

On higher-current applications, grinding the tungsten electrode to a truncated tip (to a point with a small, flat end) can help improve welding performance by preventing it from balling. First, grind the tungsten electrode to a taper, and then grind a 0.010- to 0.030-in. flat land on the end of it.

Tip 5: Don’t overweld

Overwelding occurs when more weld metal is placed in a joint than necessary to obtain the desired weld strength. It is typically the result of poor joint fit-up, lack of preparation, or improper weld parameters and causes an excessive use of shielding gas and filler metal. It also increases arc-on time and the risk of burn-through or distortion by placing too much heat into the base material. The result is often more downtime for rework and finishing or grinding, as well as additional and unnecessary costs.

To prevent overwelding, be certain that the weld is sized appropriately according to the material thickness. A good rule of thumb is to make the leg of a fillet weld no wider than the thickness of the thinnest plate and weld accordingly. For example, joining a 1/8-in.-thick plate to a 1/4-in.-thick plate would require a 1/8-in. weld bead. Also, know the size of the joint being welded. When in doubt, use a fillet gauge.

While GTAW isn’t the fastest process, it doesn’t have to be inefficient. Making good decisions about equipment and implementing proper weld preparation can help improve welding performance and get the job done faster.

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