GTAW quick tips

How do I TIG weld?

"How-To Weld" Summary

1.Establish an arc.


2.Create a weld puddle.


3.Add filler metal "dip" into the puddle while pushing the weld puddle along the weld joint.


4.End the arc and leave the torch over the weld puddle to protect it until the puddle cools.



How do I prepare my weld joint?

Clean Cleaning both the weld joint area and the filler metal is an important preparation. Remove all oil, grease, dirt, paint, etc. The presence of these contaminants may result in arc instability or contaminated welds.

Clamp Clamping may be required if the work piece cannot be supported during welding.

Tack weld Make short 1/4 in. tack welds along the work pieces to hold them together.

How do I position my TIG torch for different types of joints?

	Butt welds
	When welding a butt joint, center the weld pool on the adjoining edges. When finishing, decrease the heat (amperage) to aid in filling the crater.
	Lap joint
	For a lap weld, form the weld pool so that the edge of the overlapping piece and the flat surface of the second piece flow together. Since the edge will melt faster, dip the filler rod next to the edge and make sure you are using enough filler metal to complete the joint.
	T-joint
	When welding a T-joint, the edge and the flat surface are to be joined together, and the edge will melt faster. Angle the torch to direct more heat to the flat surface and extend the electrode beyond the cup to hold a shorter arc. Deposit the filler rod where the edge is melting.
	Corner joint
	For a corner joint, both edges of the adjoining pieces should be melted and the weld pool should be kept on the joint centerline. A convex bead is necessary for this joint, so a sufficient amount of filler metal is needed.

What can I do to improve arc starting?

Use the smallest diameter tungsten possible for the amperage you are using. Match the tungsten electrode size with the collet size.

Purchase the highest quality tungsten available - ask your distributor for Miller-branded tungsten.

Use a premium quality torch and work leads.

Keep the torch and work leads as short as possible and move the power source as close as possible to the work.

Make sure the Stick electrode holder is detached from the machine before TIG welding.

Check and tighten all connections.

Keep the torch cable from contacting any grounded metal.

Use 100% argon shielding gas.

When welding aluminum, use AC current and a ceriated (gray identifying band) or 1.5% lanthanated (gold identifying band) tungsten.

When welding steel and stainless steel, use DC-Straight Polarity (DCEN) and a 2% thoriated (red identifying band) tungsten . Prepare a pointed-end.

Always use a push technique with the TIG torch.

When welding a fillet, the leg of the weld should be equal to the thickness of the parts welded.

Why would I use Ceriated or Thoriated tungsten instead of Pure?

With the introduction of new power source technologies, the use of pure tungsten is decreasing.
	Pure tungsten melts at a lower temperature causing it to easily form a rounded ball at the tip. When the ball grows too large, it interferes with your ability to see the weld puddle and causes the arc to become unstable.
	Ceriated tungsten can withstand higher temperatures and works very well with the new squarewave and inverter machines for the following reasons: Holds a point longer and starts well at low amperages. Can be used on both AC and DC polarities. When welding aluminum, it has become very acceptable to grind a point on ceriated tungsten (especially when welding on thinner materials). Allows welding amperages to be increased by 25-30% compared to Pure tungsten of the same diameter.

Types of Tungsten Electrodes

Type of Tungsten (Alloy)	Color Code	Remarks
Pure	Green	Provides good arc stability for AC welding. Reasonably good resistance to contamination. Lowest current carrying capacity. Least expensive. Maintains a balled end.
Ceriated CeO2 1.8% to 2.2%	Gray	Similar performance to thoriated tungsten. Easy arc starting, good arc stability, long life. Possible replacement for thoriated.
Thoriated ThO2 1.7% to 2.2%	Red, Yellow	Easier arc starting. Higher current capacity. Greater arc stability. High resistance to weld pool contamination. Difficult to maintain balled end on AC.
Lanthanated La2O3 1.3% to 1.7%	Gold, Black, Blue	Similar performance to thoriated tungsten. Easy arc starting, good arc stability, long life, high current capacity. Possible replacement for thoriated.
Zirconiated ZrO2 0.15% to 0.40%	Brown	Excellent for AC welding due to favorable retention of balled end, high resistance to contamination, and good arc starting. Preferred when tungsten contamination of weld is intolerable.

Typical Current Ranges for Tungsten Electrodes

Tungsten Diameter	Gas Cup (Inside Dia.)	Typical Current Range (Amps)
		Direct Current, DC	Alternating Current, AC
		DCEN	70% Penetration		(50/50) Balanced Wave AC
		Ceriated Thoriated Lanthanated	Zirconiated Pure	Ceriated Thoriated Lanthanated	Zirconiated Pure	Ceriated Thoriated Lanthanated
.040	#5 (3/8 in)	15–80	20–60	15–80	10–30	20–60
.060 (1/16 in)	#5 (3/8 in)	70–150	50–100	70–150	30–80	60–120
.093 (3/32 in)	#8 (1/2 in)	150–250	100–160	140–235	60–130	100–180
.125 (1/8 in)	#8 (1/2 in)	250–400	150–200	225–325	100–180	160–250
All values are based on the use of Argon as a shielding gas. Other current values may be employed depending on the shielding gas, type of equipment, and application. DCEN = Direct Current Electrode Negative (Straight Polarity).

Recommended Current Type, Tungsten and Gas for TIG Welding

Metal	Thickness	Type of Current	Tungsten	Shielding Gas
Aluminum	All	AC	Pure Ceriated Thoriated Lanthanated	Argon
	All	AC Squarewave	Ceriated Thoriated Lanthanated	Argon
	over 1/4"	AC	Ceriated Thoriated Lanthanated	Argon
Copper, copper alloys	All	DCEN	Ceriated Thoriated	Argon
Magnesium alloys	All	AC	Ceriated Thoriated Lanthanated	Argon
Plain carbon, steels	All	DCEN	Ceriated Thoriated Lanthanated	Argon
Stainless steel	All	DCEN	Ceriated Thoriated Lanthanated	Argon

source:millerwelds.com