Understanding TIG Pulse Settings With Ron Covell

Understanding TIG pulse welding

There has been a quiet revolution in TIG welder design over the last 20 years. Virtually every machine made these days incorporates inverter technology, and that has been a game changer. This technology gives welders and welding engineers the ability to modulate the welding current in ways that were previously not possible. In particular, inverter technology has made pulsing the welding current easier to accomplish and more cost-effective, even on entry-level machines. We’ll take an in-depth look at the benefits of pulsed TIG welding in this article.

When should you use pulsed TIG welding?

Pulsed TIG welding is ideal when excessive heat could cause problems. The more heat that goes into any weldment, the more likely distortion (warping) will become a problem. This is most noticeable on thin metal sheets and on metals with relatively low heat conductivity, like stainless, and high-tech nickel alloys, like Inconel and Hastelloy. When the heat of a weld isn’t dissipated by good conductivity, it keeps the weld and the adjacent heat-affected zone at a higher temperature for a longer time, causing more distortion.

Another instance where pulsing can really help is when welding out of position. Gravity always wants to pull a liquid weld downward, and if you’re welding overhead, this can be quite problematic. Pulsing helps keep the puddle attached to the metal and lessens its tendency to fall toward you as you’re welding. We’re sure you can see the benefit here!

How does a pulsed TIG welder work?

A pulsed TIG welder alternates between two current levels:

• Peak current – the highest amperage in the cycle
• Background current – a percentage of the peak value

On basic machines, you set the peak amperage and the background defaults to about 25% of that value. Pulse frequency — the speed of the cycle — is also adjustable.

Advanced machines offer more control, letting you fine-tune the background percentage and even the time spent at peak versus background. 

For example:

• If the peak is set to 100 amps and the background is 25%, the background current equals 25 amps.
• If the peak is set to 60 amps and the background remains at 25%, the background current equals 15 amps.

This flexibility allows welders to tailor heat input and puddle control for different applications.

Choosing pulse frequency settings

While pulsing at any frequency will lessen the total heat input, there are distinct characteristics available at different points in the spectrum. Some people use a very low pulse frequency (around one pulse per second) to time the addition of filler rod. This is like a musician using a metronome to keep accurate time with the music. Most welders hold the torch stationary and add filler rod during the peak portion of the cycle, then retract the rod and advance the torch during the background period. This is also an excellent way to accentuate the “dime on dime” look that many people prize as the hallmark of a beautiful TIG weld.

How does pulse frequency affect the weld?

Pulse frequency directly influences heat input, weld appearance and control. Here’s how different ranges typically affect the weld:

Very low frequency (one pulse per second)

Very low frequency may be beneficial when making a pass over a weld that has an uneven bead profile. The slow, even pulsing can add a regular ripple pattern that wasn’t there previously. Filler rod is not generally added when using this technique.

Low frequency (two to 10 pulses per second)

In the two- to 10-pulses-per-second range, the arc is considered “soft.” This is ideal if you want a broad bead and deep penetration is not the goal. An outside corner joint is one example where this may be desirable, or a final “wash” pass that caps off multiple root passes.

Medium frequency (10 to 100 pulses per second)

Pulsing between 10 and 30 cycles per second causes a “strobe” condition that many people find upsetting. If you experiment with this range, you may find it disorienting.

One hundred cycles per second is the default setting for many TIG welding power sources. It is a middle-of-the-road option, making it a good choice for a broad range of welding projects. It’s probably a good place to start as you experiment with different pulse settings.

High frequency (100+ pulses per second)

Pulse frequencies above 100 cycles per second tend to make the arc “stiffer" when TIG welding. This can help drive the penetration deeper into a narrow joint. This may also allow faster travel speeds and give the arc better directional control. Some industrial-level machines provide pulsing up to 500 cycles per second, which can maximize these benefits.

Using the background setting for TIG pulse welding

The background setting allows you to control the cooler portion of the cycle. A good starting place is between 25% and 40%. Higher percentages create a more fluid puddle and allow faster travel speeds, while lower percentages provide the greatest reduction in the heat input.

If your machine lets you adjust the time spent at peak current, increasing that percentage adds more heat in the weld, resulting in a wider bead and deeper penetration. However, avoid going too high — remember, the main advantage of pulsing is reducing heat in the base metal. A good place to start is between 40% and 60%.

Finally, you will need to set the amperage higher when pulsing, since the nature of the process reduces the overall heat that enters the metal.

Key takeaways

Pulse frequency helps control heat and weld penetration. The higher the frequency, the longer the weld is exposed to the peak current, creating a stiffer and more focused arc ideal for a deeper penetration and faster travel.

Background settings allow you to control the current between peaks. This helps regulate how much the weld can cool before the next pulse.

Each welder will learn which settings work best for them in various situations. It’s good to experiment and learn which aspects of pulsed TIG welding can benefit the type of work you do. You may be surprised at how many ways pulsing can ease your welding tasks.