TIG

About

Tungsten Inert Gas (TIG) welding, also known as Gas Tungsten Arc Welding (GTAW), is a precise welding process that uses a non-consumable tungsten electrode to produce the weld. Known for its high-quality, clean welds, TIG welding is commonly used on thin materials such as stainless steel and aluminum in industries requiring strong, visually appealing joints.

The TIG torch

Assembly

Collet body screws into the front of the torch body
- Gas lens does the same thing, creates laminar flow for getting into tight spots

Collet goes into the back of the collet body
- Notice slits on collet, acts like springs
- Inside of collet body is tapered, pinches the collet closed

Ceramic gas cup screws on top of collet body

Sharpened electrode goes in through the back of torch
- Grey paint: 2% ceriated is a good all-purpose electrode, ideal for low- and medium-current welding on all metals
- “rule of thumb” for stickout, half the width of your thumb from the cup to the tip of the electrode

Tail cap screws onto back of torch body, seals the collet and electrode

Spare parts

All internal parts are made of copper for its conductivity. Copper is very soft so be careful to never over-tighten anything when assembling the torche. All these parts get worn out over time, they will tarnish due to the heat, slowly losing its conductivity. Brand new parts are very shiny, bright red and conduct electricity very well; you will notice a more stable arc when you replace an old part with a new one.

There are also different sized parts for different applications. Thicker material requires more heat to weld, meaning a thicker electrode to conduct more current, thus needing larger collet and collet body, and more gas to shield, meaning a larger cup. On the other hand, thinner material requires less amperage, and when an electrode is too big for the amount of amperage the arc becomes unstable and difficult to start. Therefore, a smaller electrode, collet, and collet body should be installed, along with a smaller gas cup to concentrate the gas on the smaller weld pool.

Electrode

TIG welding uses a tungsten as an electrode. Tungsten has an extremely high melting point (3422C, 6191F), so when you weld the electrode gets hot but it doesn't melt. This means the electrode is non-consummable, it won’t last forever but it doesn’t melt and become part of the weld (unlike MIG where the electrode melts and becomes filler metal. This is a consumable electrode process)

The color of the electrode indicates the type of tungsten alloy. Some of the more common alloys include:

Grey is 2% ceriated, good choice for all types of welding; providing good arc start and restart characteristics with no spitting. It is ideal for low- and medium-current welding on all metals.

2% lanthanated tungsten (color-coded blue) is a true all-purpose electrode, with excellent arc starting characteristics and the ability to transmit high current without spitting. It provides a stable arc at both high and low current, and works very well on all metals.

Rare earth tungsten (chartreuse) has the very best low-current arc starting characteristics, and it can be used on all metals. This type is often preferred for automated welding.

Zirconiated tungsten (white) is good for welding aluminum and magnesium alloys. It has high current-carrying capacity, and it provides better arc starts and stability than pure tungsten.

Sharpening your tungsten

Make sure to use the left of the two small wheels, labeled for tungsten

Wear gloves, it’ll get toasty

Don't use pliers, not enough grip

Hold the electrode in line with the wheel, pointing up against the rotation

Want grind lines running towards the point to direct the current

If it grabs the wheel, it’ll just push you away

Holding it downward will pull you into the wheel and revoke your finger privileges

Spin it slowly and constantly in your fingers

Looking for a uniform cone, don’t want flat spots

Aim for 30 degrees

Break off the point

Don't want any burrs to throw off our arc

The flat end helps a little with penetration

Machine Setup

Starting the machine

Plug in, flip power switch

Open gas valve, set flow to 15-20CFH

Need to have gas flowing to read flowmeter, press the pedal down

Connect the ground clamp

Set the pedal and torch in a comfortable position

Settings

Amperage

As a general rule of thumb, start by setting the amperage equivalent to the thickness of your part in thousandths of an inch, ie. 1A = 0.001". So for a 1/8" practice coupon, start out at 125A.

However, with more experience you will learn to play around with this setting to suit your particular style. For example, some people might set their amperage to 140A for 1/8" Aluminum to get an extra kick when starting their weld, even though they'll only use 50% of the pedal (70-80A) for the rest of the weld after it's started.

Polarity

AC for Aluminum and Magnesium
- Electrode positive phase, electrons flowing from workpiece to electrode, blows through the back of the oxide layer
- Electrode negative phase, electrons flowing from the electrode to the workpiece, actually melts the pure aluminum inside to make a weld

DC for all other metals

Process

This setting controls how the arc starts.

HF impulse allows to press the pedal and start the arc without needing to touch the workpiece to start the flow of electricity, using high-voltage high-frequency electric pulses

Lift start requires you to touch the tungsten to the workpiece, press the pedal down, then lift off to start the arc

Stick (scratch start) is when the electrode stays live at all times so the arc starts as soon as you make contact

Miller Dynasty front control panel layout. (TIG machines in Brunsfield)

Output

This setting determines what activates the arc.

Remote allows you to use a foot pedal or hand remote

2T hold acts like a toggle function

Pulser

Use this setting to periodically decrease the heat for smaller parts.

PPS stands for pulses per second

Peak time is how long each pulse is at max amperage as a percentage of the PPS

Background amperage is the minimum amperage in between pulses

Sequence

Use this setting in conjunction with the 2T hold setting for when a remote (foot pedal) isn’t available or practical.

Initial amperage is the amount of amps used to initiate the arc, usually based on electrode size

Initial slope is how long it will take to go from initial A to your working amperage

Final slope is how long it will take to decrease from working A to final A

Final A is the amperage right before the arc cuts out

Adjust

Preflow is how long the gas will flow before the weld starts, to clear out any impurities for the start

Postflow is gas flow after the weld, to protect the weld and the electrode as they cool

DIG is used for stick welding, prevents the electrode from sticking to the workpiece

AC Waveshape

Balance changes how much cleaning actions happens to remove the Al oxide. Lower balance has more cleaning action

Frequency changes the width of the AC arc. Higher frequency will have a tighter arc with more penetration

Starting Recipes


Material	0.125" AISI 1018 plate	0.065" AISI 4130 tube	0.125" 6061-T6 plate
Amperage	130A	67A	150A
Polarity	DC	DC	AC
Process	HF Impulse	HF Impulse	HF Impulse
Output	RMT STD	RMT STD	RMT STD
Pulser	off	0.8 PPS, 40% peak t, 25A bkgnd A	off
Sequence	off	off	off
Adjust	0.2s pre-flow, 4s post-flow	0.5s pre-flow, 5s post-flow	0.8s pre-flow, 6s post-flow
AC Waveshape	off	off	70% balance, 80Hz

Start with these settings and play around with them as you practice. Only change one setting at a time until you understand what each one does, that way you can notice the effect of each one.

Troubleshooting

Amperage: The weld bead should be about twice as wide as the thickness of the material. If the bead is wider than that, turn the amperage down. Turn the amperage up if the bead is smaller.
Process: If the arc won't start when you press the foot pedal, check your process setting. If you're in lift arc or stick, the machine expects you to touch the electrode to the workpiece in order to start the flow of current. Use HF Impulse instead for most TIG operations.
Pulser: If you feel like you don't have enough time to reposition between pulses, decrease the PPS value. If you don't have time to add filler and connect the bead during the pulse, increase the peak t value. If the arc is flickering or dying in between pulses, turn up the background amperage.
Adjust: if the weld has any porosity or oxidation, check that the gas flow rate is set correctly on the regulator. If the regulator is set correctly and the issue still arises, increase the post-flow value
AC Waveshape: If the bead is too narrow, decrease the frequency. If it's too narrow AND has poor penetration, increase the amperage instead. If there's too much etching, turn up the balance. If the oxide layer won't break, turn the balance down.

Technique

Before starting

Make sure your tungsten is sharp and your filler rod is a decent length

Stick your electrode out the same amount as the width of the cup

Most joints will use about twice the length of filler as the length of the joint, make sure you have enough

Find a comfortable position. Being comfy is the fastest way to improve your welds

Trace your path to make sure you can reach and see everything you need to

Travel angle is as seen from the side of the weld, work angle is as seen from the end of the weld

Starting the weld

Position your torch so the tip of the electrode is ~1/8” from the surface of the workpiece. Never exceed ¼" (long arcing, poor gas coverage)

Hold the torch at the correct angle

5-15deg lead angle in the plane parallel to the weld, meaning handle tilted back, electrode point in the direction of travel

90deg to the face of the weld, meaning vertical for flat welds or butt joints, 45deg from vertical for lap or T joints

Apply the pedal slowly, develop the puddle

Look for how the heat input affects the width of the puddle

For joints, make a tack weld first. Start the arc in the middle of the gap to create a puddle on either side, increase the heat until they connect

Use filler sparingly at first, make sure the base material fuses fully.

Make a bead

Look for how filler input affects the height of the puddle

Make sure to tie in to your tack or last bead, ie start with some overlap

For joints, use a back-and-forth motion to connect the two pieces

Use enough filler to avoid undercut (where the surface dips down)

Finishing the weld

Finish the last ~¼" without filler to avoid a big glob at the end

Make sure to go all the way over your tack or next bead

Avoid pinholes, lack of fusion

Slowly lift off pedal, hold torch over the weld

Maintains gas coverage while the weld and electrode cool