Tig Welders are a great asset for the right applications, but before jumping in to buy one, it’s worth learning a bit about the basics.

TIG, stands for Tungsten Inert Gas

You’ve probably also come accross GTAW which stands for Gas Tungsten Arc Welding. This term is used by the Americans, but the process is the same!

How Tig Welders Work

An arc is struck between a Tungsten Electrode and the workpiece. A weldpool will form under the arc, then the torch is moved along and, if necessary, filler wire is added to the weld pool.

The Weldpool is protected from oxidisation by a Gas Shield (usually pure Argon), which is poured over the weldpool by the Torch.

Although, technically, Tig Welding is very different to Gas Welding, the action, and therefore the skillset, is pretty much the same. So if you have experience of Gas Welding, you should take to Tig Welding like the proverbial Duck to Water!

The upside to Tig Welding is that it’s extremely versatile and affords great control. It’s therefore possible to produce very high quality welds on a range of metals.

The downside with Tig Welding is the process is slow and decent quality equipment is not cheap, although prices have come down in recent Years.

Types of Tig Welder

Tig Welders fall into 3 basic categories:

1. DC Output Lift or Scratch Start (cannot weld Aluminium)
2. DC Output with High Frequency Start (cannot weld Aluminium)
3. AC/DC Output with High Frequency Start (CAN weld Aluminium)

DC Lift/Scratch Start Tig Welders

These are the least expensive and most basic form of Tig Welder. They are usually a DC Arc Welder, or an extra Mode on an Inverter Mig Welder.

To strike an Arc, the Tungsten Electrode is touched down onto the job then lifted off to form a welding arc (much the same as MMA welding).

The limitation of such a Tig Welder is that the tungsten electrode will try to stick to the workpiece when it is touched down and the Tig welders torch is permanently live.

I would only suggest this type of Tig Welding equipment to customers who primarily want to arc, or Mig Weld. For occasional, basic DC Tig Welding however, it’s a viable option.

DC with High Fequency Start

This type of Tig Welder uses a burst of high frequency (HF) to establish the welding arc.

This is easier and more precise than a Scratch start or Lift Tig Welder, as the Tungsten Tig Electrode does not have to be touched down.

A High Frequency (HF) start Tig Welder will usually have additional useful features such as Slope Down and Post Gas Flow.

If you’re seriouse about wanting to Tig Weld, you really should buy a High Frequency Start machine!

AC/DC Tig Welders

AC/DC Tig Welders are the most versatile, usually crammed with professional features and therefore, usually the most expensive.

The key thing about AC/DC Tig Welders is that you can weld Aluminium. This is not possible with a DC only Tig Welder because you need an AC output to weld Aluminium and its alloys.

Tig Welder Control Features

Slope Up/Down

Slope Up is where the Tig Welder starts the welding arc at a very low current, then smoothly brings the welding power up to the level set by the operator.

Some Tig Welders have a pre set Slope Up time that cannot be adjusted, some have manual control that allow different Slope Up times to be set.

Slope down works in the same way but at the end of the weld. When the torch trigger is released, the Tig Welder will fade the power down, instead of stopping it suddenly.

Stopping a Tig Welder arc suddenly can cause the centre of the weld to sink (known as “Cratering”). This phenomenon can even lead to a pin hole in the end of the weld. Fading the Tig Welders arc allows the weld pool to solidify more slowly to avoid Cratering.

Pre/Post Welding Gas Flow

Pre Gas Flow is where the Tig Welder turns on the gas before the arc. This ensures a good welding gas shield.

Post Gas Flow is where the Tig Welder keeps the welding gas flowing after the arc has extinguished. This is important as it prevents the hot tungsten electrode and the end of the weld from oxidising as it cools.

Pulse Welding

A Tig Welder with Pulse control allows the operator to weld very thin material with a little more control.

The principle is that the Tig Welder emits a burst of higher power to achieve penetration. The burst of High Power is followed by a burst of lower power to prevent blow through.

Pulse welding can also be used to achieve penetration on thicker material whilst at the same time, limiting weld size.

AC Frequency Control

An AC/DC Tig Welder may have AC Frequency Control.

AC frequency is the speed at which the polarity of the Tig Welding Torch switches from positive to negative and is measured in Hz (Switches per second).

A Tig Welder with fixed frequency usually switches at around 70 – 100Hz.

A Tig Welder with variable frequency control will typically have a range of around 50 – 250Hz.

The effect the frequency has is to “focus” the Tig Welding arc, in the same way you would focus a torch beam.

The higher the frequency, the more focused the welding arc.

Higher frequency would normally be used to gain greater penetration on thick aluminium, repairing a crack in a casting for example. Lower frequency would be used on thinner sheet aluminium where the heat of the welding arc needs to be spread more to avoid blow through.

Tig Welder Control Panels can look quite complex on first sight. But they are not as intimidating as they look, in fact, most are quite intuitive.

Conclusions

Tig Welders have come down a lot in price in recent Years. Yet at the same time, the level of sophistication has gone up!

Given there is a big price difference between DC only and AC/DC output machines, the first place to start is to ask yourself the question:

Do I need/want to weld Aluminium?

To weld Aluminium, you will need to buy an AC/DC Tig Welder. If not, you can buy a DC only Tig Welder.

If you’re going to buy a DC Tig Welder, my heartfelt opinion would be to buy a High Frequency Start machine.

Visit our Tig Welders Page to view our current range.

If you also want a Mig, then a machine like one of our Synergic iMigs are a great choice. These have a mode for Lift/Scratch Start Tig (with optional Torch). But HF Start Tig is always going to be a better if you plan on doing a fair bit of Tig Welding.

I hope you found this blog article about Tig Welders useful. If you did;

Please let me know what you thought by leaving a comment.

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Cheers

Graham