TIG Welding

 

 

TIG Welding Tutorial

This tutorial is intended to offer practical advice to complete beginner TIG welders but should also be useful to intermediate welders.

There’s no single ‘learn to TIG’ page, instead each page demonstrates aspects of the technique using different joint types. As usual the tutorial is not a substitute for a college course or time with a professional, but it should cover the basics. Feel free to ask on the forum if you get stuck.

Set Up

Just enough information to get the machine set up for the tutorials.

The page details how to grind the tungsten, how far the tungsten should stick out from the shroud, gas flow and machine settings.

Setting up a TIG welder

TIG Amp Chart

Learning to TIG weld is tricky enough without having to guess the amps. We’ve written down the amps, tungsten size and filler rod diameter that we would choose for different joints, materials and thicknesses. You can print them out and stick them to your welder.

There is no definitive chart for this sort of thing – the choice of amps depends a lot on technique and travel speed, but it’s handy to have a starting point.

TIG Amp Chart

TIG Welding Technique

TIG is a very precise process, much more so than MIG or Arc, so if you are moving from those processes pay attention to the tips on how to set up your body position to achieve the necessary precision.

We’ve produced a few videos to illustrate how to TIG weld. The page covers the technique itself and what to aim for.

TIG Welding Technique

Butt Weld and Tacking

Don’t spend too much time laying TIG beads – when you get the hang of moving the weld pool along it’s much more fun and informative to try a joint.

We’ve also covered tacking in this section.

Butt Welding and Tacking

Fillet Welds

Fillet welds are an excellent test of technique. Once you have clicked with fillets all of your other TIG welding should be good.

The earlier pages talk about things like the arc gap and how the filler rod affects the weld. Fillets will force good technique in these areas.

TIG Fillet Welds

Lap Joints

We’ve covered the main techniques so for completeness it’s worth offering some advice on the other types of joint you might want to do. Lap joints are very much like fillet joints, just you are welding end-on rather than side-on to the sheet on top.

The lap joint page covers the trouble that involves.

TIG Lap Joints

Outside Corner Weld

Outside corner joints introduce gas issues as well as positioning issues. That makes them a great way to finish off the technique section of the tutorial.

An inside corner (fillet) will demand more amps and will cope with a smaller shroud than butt welds. An outside corner is the opposite – the gas is not contained by the joint, and there is nowhere for the heat to go so amps need to be reduced.

Outside Corner Weld

Credits

Many thanks to Paul Holland who spent several days helping prepare the material for this tutorial and taught me to TIG weld at the same time.

Thanks also to Weldequip for the loan of an Inverter Fusion 200HF when I was struggling with my Syncrowave. The IFL transformed my TIG welding.

Finally a big thanks to all the forum supporters who funded the tutorial. If you found the tutorial useful don’t hesitate to donate and help fund more useful stuff. Otherwise you can contribute by helping others on the forum.

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TIG Welder Set Up

Setup is covered in more detail in the TIG FAQ. The basic information on this page should be a good starting point apart from for specific joints where alternative set up is detailed in the relevant tutorial page.

Tungsten

For welding steel the tungsten should be ground to a long point with the taper length about 2 or 3 times the diameter of the tungsten. See DC Electrode Preparation. The long taper and sharp tip improve arc stability.

For a butt weld or open corner weld the stick out would be about 5-6mm. Setting the tungsten stick out for fillet welds is covered on the fillet weld page.

Gas Shrouds

For general purpose work on steel a number 7 shroud is a good compromise. A smaller number 4 shroud would be more suitable for fillet welds, and larger shrouds might be used for aluminium. As a rule the larger the shroud the better the gas coverage.

Tundsten set to 5-6mm stick out

Shielding Gas

Pure Argon is normally used as a TIG shielding gas and is suitable for both steel and aluminium welding. The shielding gas must be completely inert – MIG shielding gasses cannot be used as the CO2 would cause the tungsten to oxidise.

Flow Rate

Flow rate will generally be 6 to 7L/min. The rate might be increased slightly to compensate for drafty conditions. TIG uses a lot of shielding gas so it pays to set up the gas flow accurately. A flow meter attached to the regulator will give a more accurate flow reading than the gauge on the regulator (see the regulator page for the set up), or a peashooter type flow meter can be used to measure flow at the torch (see the photo to the right).

Post-Flow Time

Postflow protects the tungsten and the weld as they cool. The tungsten will take longer to cool from higher amps, and a rough rule of thumb is to increase post flow time by 1 second for every 10 amps. We’ve used about 4-5 seconds post flow for everything shown in the tutorial.

Gas flow tester

Polarity

DC TIG Welding is carried out with the torch negative and the work positive. That is also known as DCEN (DC electrode negative) or “straight” polarity for those with older welders.

About two thirds of the heat goes to the positive side or the arc. For TIG the negative torch helps avoid overheating the tungsten.

TIG welding and polarity

Other Settings

The only other setting we have used in the tutorial is slope down (set to 1.5 seconds). This reduces the amps gradually at the end of the weld which helps prevent the formation of a crater. The gas post flow time should be significantly longer than slope down time.

Some expensive TIG welders have an AC option. AC current is used for aluminium, DC for steel.

Many of the other knobs on TIG welders are to do with pulse. We’ve not used pulse at all in the tutorials and it’s best switched off while you get the hang of technique.

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TIG Calculator

The TIG calculator is intended as a print out reference for DIY TIG welders but is only intended as a starting point. Once you get the hang of TIG welding you might find you prefer to weld at higher or lower amps depending on technique and travel speed. Complete beginners might prefer to run maybe 10% lower amps to compensate for slower speed, but if you find you need to reduce amps much more then your arc gap is probably too long.

We’ve only covered up to 3mm in the chart. Beyond that thickness (apart from for specialist applications) you would tend to do multiple runs or just use TIG for the root weld and use Arc or MIG for filling in the remainder of the joint.

Mild Steel

Steel Thickness
(mm)
Filler Rod
(mm)
Tungsten
(mm)


Practice beads


Closed root butt joint


Fillet joint


Open root butt joint (gap is half of material thicknesss)


Lap joint


Outside corner joint

Amps
Amps
Amps
0.8
1.0
1.0 or 1.6 1
25
30
20
1.0
1.0
1.0 or 1.6 1
30
35
25
1.2
1.0
1.6
35
45
30
1.5
1.0
1.6
45
55
40
2.0
1.0 or 1.6 2
1.6
60
75
55
3.0
1.6
1.6
90
110
80

1 A 1.6mm tungsten is OK down to about 30 amps. It can be used on thinner material if the tip is kept very sharp. Reduce the amps a little if using a 1.0mm tungsten.

2 2mm is the transition between 1.0mm and 1.6mm filler rod. The larger filler rod cools the weld pool more than the smaller rod so you might add about 5 amps if using 1.6mm filler rod.

 

Stainless Steel

Stainless is less thermally conductive than mild steel, so heat does not flow away from the weld quite so quickly. The amps required to weld stainless are about 10% lower than the amps used for mild steel. Beginners might find the stainless chart handy for mild steel – the lower amps will compensate for a slower travel speed.

Steel Thickness
(mm)
Filler Rod
(mm)
Tungsten
(mm)


Practice beads


Closed root butt joint


Fillet joint


Open root butt joint (gap is half of material thicknesss)


Lap joint


Outside corner joint

Amps
Amps
Amps
0.8
1.0
1.0 or 1.6 1
20
25
20
1.0
1.0
1.0 or 1.6 1
25
35
25
1.2
1.0
1.6
35
40
30
1.5
1.0
1.6
40
50
35
2.0
1.0 or 1.6 2
1.6
55
70
50
3.0
1.6
1.6
80
100
75

1 A 1.6mm tungsten is OK down to about 30 amps. It can be used on thinner material if the tip is kept very sharp. Reduce the amps a little if using a 1.0mm tungsten.

2 2mm is the transition between 1.0mm and 1.6mm filler rod. The larger filler rod cools the weld pool more than the smaller rod so you might add about 5 amps if using 1.6mm filler rod.

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TIG Welding Technique

Complete beginners to TIG should begin on 2mm or 3mm steel. The weld pool is larger and easier to control on thicker steel which makes it easier to develop technique – trying to learn on thinner material will be more frustrating. We’ve used 2mm steel for this tutorial. The welder was set to 50 amps, and the tungsten and filler rod were both 1.6mm.

Setting up the machine and tungsten grinding and stickout are covered on the TIG set up page. Advice on power settings for different steel thicknesses can be found on the TIG Amp chart.

Find a Steady Position

When TIG welding you need to be able to control the distance between the tungsten and the work to within about 1mm. This is only possible with a good welding position. In the photos the welder has used a few tricks:

  • Just to confuse you we’ve photographed a left handed welder. If you are right handed hold the torch in your right hand.
  • The welder is sitting down and working on a bench. His upper body weight is not supported by the bench – the bench is only used for positioning.
  • In the photo a flexible torch head (very handy) is being used to maintain the angle of the torch with the hand resting lightly on the bench. The hand would need to rest on a piece of wood for the correct angle with a standard torch.
  • The torch lead is wrapped around his arm. This takes the weight of the lead away from the torch and reduces the chance of the lead snagging as the weld progresses.
  • The head is positioned to the side for a good view of the weld pool. It is very common for beginners to hide the weld behind the gas shroud.
  • The lighting is from the side as well as overhead – it allows the welder to see the tungsten position before starting the weld.
  • The torch would move in the direction of the red arrow in the photograph (that one isn’t really a trick but is worth a mention while the photo is there).

Relaxed muscles will aid control of the torch – try not to TIG weld directly after hammering or other physical activity, and ensure the workshop is at a comfortable temperature.

The red dot in the photograph just below the torch shows the area the welder will be looking at while welding. It’s a tiny area, so for a good view his eyes need to be close to the weld. It’s very common for people to discover they need glasses when they first take up TIG welding.

TIG Welding

TIG Welding Body Position

Torch Angle and Movement

The video demonstrates torch angle, position and movement. Above all it shows what a delicate process TIG is. The torch movement is steady in the video and briefly stops while the filler material is added.

The torch is held at about 20 degrees from vertical, tilted so the tungsten points in the direction of the weld. The tilt encourages the weld pool to form ahead of the torch making it easier to add filler rod.

The gap between the tungsten and the work should be maintained at between 1x and 1.5x the diameter of the tungsten. We’re using a 1.6mm tungsten so the gap is about 2mm.

It is good practice to move the torch across the work as a dry run before welding to make sure the torch angle and distance to the work can be maintained naturally, and that there isn’t anything that will impede movement.

Learning to TIG Weld

Begin by starting the arc on steel. Get a feel of the arc and the weld puddle.

Next try welding on the surface of some sheet without using filler rod. This will help you get a feel for how the puddle moves, and practice in maintaining a tight arc length. Finally move on to adding filler wire as in the video below.

We’ve used 1.6mm filler rod, but it would have been much easier to feed 1.0mm filler rod into the pool.

Things to watch for in the video:

The tungsten is positioned about 2mm from the steel. the position can be checked by tapping the tungsten against the work before starting the weld. There is a short pre-flow of gas and then the arc starts using HF (high frequency start).
The torch is kept stationary for a few seconds to allow a weld pool to form. The size of the initial weld pool sets up the width of the weld. A large pool will tend to result in a wide weld with a lot of penetration, and a small pool in a narrower weld with less penetration.
You can see the tip of the tungsten reflected in the weld pool. The arc length can be judged by the distance between the end of the tungsten and the reflection in the pool. As you become more familiar with TIG it becomes easier to judge the arc length by the width and height of the arc itself.
The filler rod is added to the very front of the weld pool – it is the weld pool that melts the filler rod not the arc. Adding filler rod will cool the weld pool.
The filler rod is kept low – too high and the arc would ball it back. If the arc length is too long the filler wire will tend to melt back before it reaches the puddle.
The filler rod is kept under the gas shroud at all times. This keeps it close to the arc to keep it warm and make it easier to melt, and also prevents it from oxidising.
At the end of the weld the torch is brought back a little and switched off. The torch is held in position until the post flow gas has stopped. The post flow protects the tungsten and the end of the weld pool.

It’s not going to go well at the first attempt – there are so many things going on at the same time that you’ll tend to focus on one while the others go astray. It’s best to start with getting the arc gap right. After some practice it will become natural and you can focus on the weld pool and adding the filler rod. Once that’s there look at how wide the weld pool is and adjust speed of travel to control penetration. Only when all of that is in place will you start to achieve the neat welds that TIG is capable of.

Arc Length

Arc length controls the amount of heat in the weld. TIG is a constant current process (the amps you set on the machine are the amps you get), but increasing the arc length will increase the voltage which in turn puts more heat into the weld.

Beginners will tend to have their arc length too long for fear of contaminating the tungsten. It should be maintained at between 1 and 1.5 times the diameter of the tungsten (that’s between 1.6mm and 2.4mm arc length for the 1.6mm tungsten we are using).

Excessive arc length will make the arc difficult to control, and it will also make the tungsten very hot so if you do touch down into the weld pool the tungsten will suck up a fair bit of steel. That’s what happened to the tungstens in the photo and it’s a major frustration for beginners. With a tight arc the tungsten stays cool and touching down hardly even takes the point off the tungsten.

Contaminated tungstens

Size and Speed

The videos and photos do not give a sense of scale. The weld in the video is only 4mm wide which is perhaps half the width of a MIG or Arc bead for the same material thickness.

The travel speed was about 1mm per second, again much slower than MIG or Arc, but faster than you might imagine while you are distracted by all the other things involved in learning to TIG weld.

The weld is quite flat – less than 0.5mm tall. An ideal for a joint would be to have the reinforcing thickness of weld above the work about 10% of the material thickness.

TIG Bead showing width and length
Our weld has not penetrated through the bottom of the 2mm sheet. We’re not aiming for penetration here, just some practice in laying beads.

If your bead penetrates through the rear of the steel before you get the hang of laying a nice bead it is likely that your travel speed is too slow.

The travel speed can be judged by the width of the heat affected zone around the weld (the discoloured part). In the photograph it is quite narrow, maybe 15mm edge to edge.

If the weld had been done at lower amps and a slower travel speed to compensate the heat affected zone would have been much wider. A slow travel speed actually puts more heat into the weld as heat is conducted away from the weld pool before the weld pool is established.

Reverse of bead on  sheet

Feeding TIG Filler Rods

There is so much going on with TIG welding that it’s probably best not to feed the wire for the first few practice beads. Just hold onto the wire and stop adding it before your fingers burn.

Once all the other things are in order feeding the filler rod happens naturally. The wire can be fed in whichever way feels comfortable to you, but here’s a video of an easy way.

You only need to feed the wire to maintain the distance between your fingers and the arc – the feed rate is much slower than shown in the video.

The filler rods are quite long. They are much easier to work with if you cut them in half.

Struggling?

You did start off on 2 or 3mm steel didn’t you? It really is a lot easier than the thin stuff.

The two welds in the photo on the right were made by a beginner TIG welder. In the first photo the welder was struggling to control the weld pool, and was having trouble adding the filler rod.

The second weld was made immediately afterwards with no further training. The only difference is the thickness of the steel (and the amps adjusted to suit). The increased thickness means the weld pool is larger and easier to control, which makes it much easier to add the filler rod.

The plate in the second photo hasn’t been prepared properly – the steel needs to be completely shiny and free of rust or mill scale else the weld will spit steel back at the tungsten and contaminate it as soon as you start the weld.

The ease of welding thicker material makes it easier to understand and develop the technique. Also it provides a big confidence boost. Once you have the technique it is easily transferred to thinner material.

TIG welds on 2mm and 6mm sheet

Next Step

It gets boring laying beads on plate. Once you have the basic technique try some butt welds. They will give much better feedback on travel speed and the amount of filler rod to add. After those try some fillet welds – it was getting those right that made me click with TIG welding.

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TIG Welding Tutorial – Butt Welds

The technique for butt welds is very similar to the technique used in the TIG technique page – if the two sheets were positioned edge to edge with no gap the technique would be exactly the same, and generally that’s what you would do for material thinner than 2mm. On this page we’ve spaced the two sheet of 2mm stainless steel apart by 1mm to create a root gap. See the amp chart for settings.

The root gap increases penetration, and also makes it easier to control the penetration. More filler rod needs to be added during welding to fill the gap, and tacking the two sheets before welding requires a bit of technique.

Tacking

If two sheets are very close together they can be tacked using a tight arc length without problems. If there is a gap between the two sheets then there is a tendency for two separate pools to form, melting away both sheets without joining to form a single weld puddle.

In the photo the tack has been attempted on the edge of the joint. While it would be easier to tack a little distance in from the edge, the edge will need to be welded at some point and it’s easier when it’s cold. Also we avoid the need to weld over the tack as the joint is welded.

SHeet burned back where tacked
To avoid burning back the sheets the filler rod needs to be added very shortly after starting the arc and before the weld pool has had a chance to burn the corners away.

The filler rod has two functions. It bridges the gap between the two sheets allowing a single weld pool to form, it removes heat from the weld pool preventing the sheets from burning away.

In the video the arc is started, filler rod very quickly positioned in the joint. Then the weld is continued for a short distance along the plate. We plan to start the weld on top of the tack, and if the tack is too short it will melt and break apart when the weld is started.

If the tack causes the gap to close up too much a tap with a hammer on the tack should spread the gap again.

Butt Welding

The basic technique is identical to laying beads on the surface of plate in the TIG technique page. A steady torch movement, tight arc, and filler rod added to the very front of the weld pool. In the video the material is 2mm stainless, there is a 1mm root gap, and the weld was carried out at 45amps using 1.0mm filler rod.

When laying a bead on plate or when the two sheets are touching there is no need to add a lot of filler rod. On the technique page the filler rod was just dipped into the front of the weld pool.

The butt weld in the photograph had a 1mm root gap (the two sheets were 1mm apart) and sufficient filler rod had to be added to fill the gap. In the video the filler rod is being fed in with the stamped end first, and later in the video it is possible to see the filler rod being pushed in to the front of the weld pool.

A great deal of heat is drawn from the weld pool to melt the filler rod. Adding the filler material independently of the arc is a big advantage of TIG – the rate at which the filler is added can be used to control the heat in the weld.

The photo shows the keyhole that forms ahead of the weld where the two sheets have burned back a little. The photo exaggerates the size of the keyhole – it’s 3mm plate with V preparation that tapers to a point for the purpose of photographing a keyhole. Normally it would be a lot smaller. The keyhole is visible during welding and is a useful indicator that the weld pool has melted the sheets.

Once the hole has formed the molten filler is attracted to the back of the hole by surface tension to form the weld bead. This closes the keyhole and the hole is advanced forward by manipulation of the torch.

With stainless and critical mild steel joints, back purging would be essential when using this technique.

Keyhole in TIG butt joint

Thick metal

TIG is rarely used for metal over 6mm as it would require multiple runs to add sufficient filler material to complete a join. Thick metal is generally prepared in a V as in the arc welding flat joints page, TIG is often used for the root pass, then Arc welding used to complete the joint.

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TIG Welding Tutorial – Fillet Welds

The torch is angled at 45 degrees to the corner of the fillet (tilt angle) and also angled back about 20 degrees towards the direction of travel (slope angle). The metal is 2mm stainless, and we set the machine to 75 amps (see the tig amp chart).

A smaller shroud than normal is used for fillet welds – we’ve used a number 4. This allows the torch to get closer to the corner of the joint. Gas shielding is poorer with the smaller shroud, but for fillet joints the gas is contained in the corner, making up for the smaller shroud.

The end of the tungsten is about 3mm from the corner of the joint when the torch is in welding position. It’s difficult to judge the distance to the corner. A piece of 1.6mm welding rod in the corner can be used to set the tungsten stick out much more accurately.

Torch position for TIG fillet weld

Autogenous Fillet Weld

Fillet welds are very good for highlighting technique faults. If the arc gap is too large or if too much filler rod is added (building up the weld so the tungsten is too far from the corner) then the weld pool will tend to melt the edges of the sheet and not the corner of the joint. This results in an untidy weld with poor penetration into the root.

Autogenous welds are the way to develop fillet technique. Autogenous just means the welds are carried out with no filler rod. Without the filler if the tungsten is too far from the corner it will arc against one side of the sheet or the other and it will not be possible to maintain a weld pool. It’s well worth trying one while learning as fillets with filler rod are performed with exactly the same technique.

Here’s a video of an autogenous fillet weld. We’ve started on the end of a tack so we have a bit of filler material to make into the weld pool, then the weld pool is manipulated along the joint with no further filler rod added.

 

OK so there’s a touchdown in there. The tungsten is very close to the weld pool so this does happen on occasion, but it’s not the end of the world. The tight arc gap keeps the tungsten cool so it doesn’t pick up excessive metal from the weld pool. A decent inverter TIG welder will cut the power to the tungsten as soon as it dips which further reduces contamination to the tungsten. We’ve kept going and finished the weld.

The edge of the ceramic can be rested on one side of the fillet and used as a guide for the torch.

Autogenous welds are pretty, but not as strong as ordinary TIG welds. The metal in the weld pool comes from the sides of the corner so there is undercutting, and the reinforcement added by the weld is quite small – normally it would be about 0.8 of the thickness of the steel.

This is the same 2mm stainless sheet we started with – it looks much thicker in the photo!

Autogenous TIG fillet weld showing undercut

Fillet Weld with Filler Rod

The main reason to try autogenous first is to get a feel for how the weld should behave. In the photo there is the autogenous weld from the first video to the left, and the fillet from the following video to the right.

The two welds are very similar in size. The filler just being added to replace the metal melted into the weld pool. Too much filler rod will build up the weld excessively and cause the heat to go to the sides of the fillet and not the corner.

We’ve stayed at 75 amps and used 1.0mm filler rod for the fillet.

Comparison of autogenous fillet weld and weld using filler rod
In the video the rod is only touched to the front of the weld pool and not forced in to the pool. You don’t need to add very much filler.

The filler rod replaces the metal used to form the weld pool, so there is no undercutting. Cros section of TIG fillet weld

Fault – Arc gap too long

Every TIG welder who has not had formal tuition will likely suffer from this one. The weld on the right is normal – neat with a straw colour. The one on the left was deliberately done with a 4mm arc gap (much too long) which increased the heat in the weld and generally left a mess.

The arc would form against one sheet or the other, and the torch had to be manipulated between the sheets to make the weld pool form against both sheets. This reduced the speed of the weld and the increased heat input can be seen in the grey colour of the weld and the distance of the bluing on the material from the weld.

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TIG Welding Tutorial – Lap Joint

Lap joints are very much like fillet joints. The torch is angled towards the joint at about 40 degrees from vertical (tilt angle), and about 20 degrees from vertical towards the direction of travel (slope angle). The tungsten is aimed at the bottom sheet slightly away from the corner.

The two sheets need to be tightly clamped together to allow heat from the top sheet to dissipate in the bottom sheet. Otherwise the edge of the top sheet will burn away.

The amps are also reduced to help prevent the top sheet from melting back. We’re set at 50 amps to weld 2mm stainless and are using 1.0mm filler rod.

TIG torch position for Lap Weld
The video isn’t very clear, but the technique is much the same as a fillet weld – a tight arc and very little filler rod needed.

The video is shot from behind the arc. About 2 thirds of the way through you can see the filler material being sucked behind the arc and freezing at the rear of the weld pool.

 

The differences between lap joint and fillet joint technique are aimed at increasing the heat in the lower plate and reducing heat in the overlapping plate where there is less steel to dissipate heat. The torch is aimed slightly more towards the lower sheet, the tungsten is aimed onto the lower sheet a small distance from the corner, and the amps are a lot lower than a fillet joint.

The the photo the top edge of the sheet has been burned into slightly. We’ve used 2mm steel which makes the job very fiddly – the width of the weld bead is only about 3mm.

Lap joints are much easier on 3mm or thicker steel.

Section of lap weld, 2mm sheet

 

 

 

One response to “TIG Welding

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