How TIG Welding Works

The acronym TIG stands for Tungsten Inert Gas and describes what this process is essentially all about. Also called gas tungsten arc welding (GTAW), the process uses a tough tungsten electrode to produce the weld. Similarly to MIG welding, TIG uses a shielding gas, but for this type of welding the gas is usually argon.

Unlike MIG welding, there is no flux included as standard. Many TIG applications will rely on metal workpieces melting enough to be fused together, known as an autogenous weld. If a larger weld is required then the welding torch can be used with a filler rod, a thin piece of metal that can be fed into the arc to form a bead.

The main advantages of using TIG welding over the other types we have considered in this guide are that the welds created are not only strong and airtight, but also very neat. Very delicate, small welds can be performed with this method that would not be possible with the other methods and the rubbing back and tidying up at the end of welding is substantially reduced.

The Equipment

1. Welding torch

The TIG welding torch is shaped like a T and is equipped with a cooling system, either with air or water. The torch is connected with lines to the power supply, the shielding gas and, if used, to the coolant. Inside the torch, the tungsten electrode is surrounded by hard alloys of copper and brass, which help transmit the heat and current effectively. Outside of this heat resistant insulating plastics protect the welder.

2. Power supply

In the same vein as MIG welding, TIG welding uses a constant current power supply, which makes life a good deal easier for the operator. The polarity of the power supply is adjustable, and the preferred setting will depend greatly on what types of metal are being welded.

3. Electrode

The electrode used in this welding process is made from tungsten or a tungsten alloy. This is because of tungsten’s very high melting point, meaning there is no consumption of the electrode during welding. There are a number of different diameter electrodes and alloys available and advice should be taken regarding selection depending on your particular job.

4. As with MIG welding, the use of a shielding gas is necessary to protect the electrode, arc and workpiece from harmful atmospheric gasses. Argon is the most frequently used gas for TIG welding, although argon mixed with helium is sometimes used to increase the control of the heat output.

The process

TIG welding is considered one of the trickiest processes in the industry. The welder needs to maintain a very short arc length for prolonged periods, so needs a steady hand and a great deal of skill. If using a filler rod, the welder will also need to use his second hand to feed the rod into the arc, so needs to have twice the control as with the other processes.

Striking the arc is done in the same manner as with stick welding. Once the arc is present, the welder can either perform an autogenous weld by moving the arc in a small circle to create a welding ‘pool’ and then moving this along the length of the weld. If they are using a filler rod, the rod is introduced to the arc once the welding ‘pool’ has been created and molten metal added as it is needed.

TIG welding – Step by step

1. Set up the TIG machine

– Check AC or DC current, depending on the type of metal you are welding

– Check the frequency setting if there is one

– Set the amperage correctly for the piece you are welding

2. Check the shielding gas is connected and the flow ready to go

– Aim for a good 5 seconds of gas both before and after the weld

3. Set up the TIG torch and electrode

– Take advice from online or an expert if you are unsure about this

4. Prepare your workpiece, area and PPE equipment

– Ensure your workpiece is properly cleaned with wire wool / brush or a chemical treatment

– Use clamps to secure your workpiece to your bench

5. Start the arc and create a welding pool to begin the weld

– It can be a good idea to ‘tack weld’ the two pieces together for extra stability before you start

6. Move the welding pool along the length of the weld until complete

– If you are doing a larger weld or need to add additional strength to your weld, use the filler rod to add extra metal to the welding pool as you go

Tips for better operation

With TIG welding being the hardest process to master, perfection is going to take some practice. Here are some of the most common problems and their likely remedies:

• If your weld bead is porous or a bad colour, you may have condensation on the metal. Be sure to blow out all condensation from the lines before you start and properly clean down your metal, particularly if it has been stored in a cold environment.

• If you notice yellow powder or smoke, your tungsten electrode is being damaged. Check if your gas flow rate is adequate and that you are using the correct mix of gas, as well as making sure you are leaving the gas on for long enough after the weld is done.