Why is it better to use other tungsten electrodes instead of pure tungsten electrodes for welding?
Science and technology have lead to greater revelations and drastically changed our lifestyles. Today, you have more powerful systems and appliances including gadgets that enables better efficiency and performance whatever we tend to do using them. It has revolutionized our lives. The newer power source technologies are way more powerful and efficient than the traditional ones that were once used for the same purposes. They give you better precision and perfection of end results. On this context, welding strategies have also been improvised with the use of higher quality welding equipments. Today, you have more stronger and sturdy welds being produced and the end products have certainly been very efficient and great. On this note, use of traditional pure tungsten electrodes for welding has decreased.
Pure tungsten has the ability to melt down at lower temperatures forming rounded ball at the tip of the welding gun. This ball as it grows in size during the welding obstructs the welder, not allowing focusing on the task. In fact it doesn't allow you to see the weld puddle and the arc which is very significant for producing proper welds goes unstable as a result. Predominantly you end up with poor quality welds.
Ceriated tungsten electrode on the other hand has tremendous capabilities to work in higher temperatures. It also works pretty well with the modern technologies such as the new squarewave and inverters used for providing stability of current supply. It holds the point longer and starts well at low amperages as well. It could be used for both AC as well as DC polarities. It allows welding amperages to be increased by 25-30% when compared to pure tungsten of the same diameter.
Thus predominantly, these days heavy manufacturing industries make use of ceriated, thoriated, lanthanated and zirconiated tungsten electrodes for carrying out welding processes.
Types of Tungsten Electrodes
|
|
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% |
Orange
|
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
|
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
|
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 |
Pure |
Ceriated
Thoriated
Lanthanated |
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
|
|
