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Page 5 of 6
How do I TIG weld?
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| "How-To Weld" Summary |
- Establish an arc.
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- Create a weld puddle.
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- Add filler metal "dip" into the puddle while pushing the weld puddle along the weld joint.
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- End the arc and leave the torch over the weld puddle to protect it until the puddle cools.
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How do I prepare my weld joint?
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- 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. |
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How do I position my TIG torch for different types of joints?
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Butt welds
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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.
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Lap joint
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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.
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T-joint
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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.
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Corner joint
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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.
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What can I do to improve arc starting?
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- Use the smallest diameter tungsten possible for the amperage you are using. Match the tungsten electrode size with the collet size.
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- Purchase the highest quality tungsten available - ask your distributor for Miller-branded tungsten.
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- Use a premium quality torch and work leads.
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- Keep the torch and work leads as short as possible and move the power source as close as possible to the work.
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- Make sure the Stick electrode holder is detached from the machine before TIG welding.
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- Check and tighten all connections.
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- Keep the torch cable from contacting any grounded metal.
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- Use 100% argon shielding gas.
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- When welding aluminum, use AC current and a ceriated
 (orange identifying band) or lanthanated  (blue identifying band) tungsten.
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- When welding steel and stainless steel, use DC-Straight Polarity (DCEN) and a 2% thoriated
 (red identifying band) tungsten . Prepare a pointed-end.
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- Always use a push technique with the TIG torch.
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- When welding a fillet, the leg of the weld should be equal to the thickness of the parts welded.
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Why would I use Ceriated or Thoriated tungsten instead of Pure?
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With the introduction of new power source technologies, the use of pure tungsten is decreasing.
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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.
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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.
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Types of Tungsten Electrodes
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Remarks
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Pure
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Green
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Provides good arc stability for AC welding. Reasonably good resistance to contamination. Lowest current carrying capacity. Least expensive. Maintains a balled end. |
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Ceriated
CeO2
1.8% to 2.2%
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Orange
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Similar performance to thoriated tungsten. Easy arc starting, good arc stability, long life. Possible replacement for thoriated. |
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Thoriated
ThO2
1.7% to 2.2%
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Red
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Easier arc starting. Higher current capacity. Greater arc stability. High resistance to weld pool contamination. Difficult to maintain balled end on AC. |
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Lanthanated
La2O3
1.8% to 2.2%
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Blue
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Similar performance to thoriated tungsten. Easy arc starting, good arc stability, long life, high current capacity. Possible replacement for thoriated. |
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Zirconiated
ZrO2
0.15% to 0.40%
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Brown
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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
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| DCEN |
70% Penetration |
(50/50) Balanced Wave AC |
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Ceriated
Thoriated
Lanthanated
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Pure
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Ceriated
Thoriated
Lanthanated
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Pure
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Ceriated
Thoriated
Lanthanated
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| .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 |
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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).
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Recommended Current Type, Tungsten and Gas for TIG Welding
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Metal
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Thickness
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Type of Current
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Tungsten
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Shielding Gas
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| Aluminum |
All
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AC
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Pure
Ceriated
Thoriated
Lanthanated
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Argon
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All
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AC Squarewave
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Ceriated
Thoriated
Lanthanated
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Argon
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over 1/4"
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AC
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Ceriated
Thoriated
Lanthanated
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Argon
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| Copper, copper alloys |
All
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DCEN
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Ceriated
Thoriated
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Argon
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| Magnesium alloys |
All
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AC
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Ceriated
Thoriated
Lanthanated
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Argon
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| Plain carbon, steels |
All
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DCEN
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Ceriated
Thoriated
Lanthanated
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Argon
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| Stainless steel |
All
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DCEN
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Ceriated
Thoriated
Lanthanated
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Argon
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Additional TIG Resources from Miller
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TIG Handbook 
Download or order Miller's TIG Handbook - includes the fundamentals of TIG welding, as well as, practical information on techniques used to produce a good weld. A well illustrated 86-page textbook that also contains a wide range of related subjects such as joint design, weld symbols, weld defects, troubleshooting, and safety.
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TIG Welding Articles
Read TIG related welding articles from Miller's Welding Library:
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TIG Guidelines Booklet
Download Miller's Guideline to Gas Tungsten Arc Welding (GTAW) Handbook (PDF). This 16-page booklet is a guide to TIG welding basics. Sections on Process, Arc Shaping, Tungsten Electrodes, and Shielding Gases give you the essentials.
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Safety Quick-Guide
Download and read our Safety Quick-Guide (PDF) for welding and cutting the safe way! Practical, easy-to-read advice covering a wide range of hazardous situations.
Owner's Manuals
Get the most from your Miller welder by downloading the specific Owner's Manual for your unit. From safety, operations/setup, & maintenance to troubleshooting & parts.
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