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3. TIG WELDING (Tungsten inert gas)
It is a process of arc welding under shield gas, using a torch
with infusible tungsten electrode and which can be run with
or without filler metal in an inert gas atmosphere such as argon
and mixtures thereof. Through this process the arc become
more stable without spatter which guarantees a strong
mechanical resistance of the welding joint.
This Tig process replaces with many advantages the
oxyacetylene on steel, stainless steel, copper, brass DC welding,
the aluminum on AC welding and, in several cases, the MMA and
Mig welding especially when the welding seam remains visible.
Electrode chemical composition
Code
Composition
WP
Pure tungsten
0,35-0,55%
WT4
thorium
0,80-1,20%
WT10
thorium
WT20
1,7-2,3% thorium
WT30
2,7-3,3% thorium
WT40
3,8-4,3% thorium
0,15-0,50%
WZ3
zirconium
0,70-0,10%
WZ8
zirconium
1,0-1,2%
WL10
lanthanum
WC20
1,9-2,3% cerium
Æ Electrode
(mm)
1,6 mm
2,0 mm
2,5 mm
3,2 mm
4,0 mm
5,0 mm
Shield gas: The shield gas is used to:
- Involve the welding arc on an ionizable atmosphere.
- Avoid the seam contamination by the oxygen of the atmosphere.
- Provide the cooling of the electrode.
Argon (Ar) – Is the most common gas used with a purity grade of 99,9%.
Helium (He) – For the copper welding mixed with the argon under percentages between 10%
and 75%.
Hydrogen (H) – Inert gas at environment temperature especially for the use on copper welding.
Inadvisable for welding on closed places; it mixes with the atmosphere oxygen
and changes the air unbreathable.
Type
W
Th
Zr
La
Ce
Chart of electrode diameter and current
Amp. DC
Negative (-)
40-130 A
75-180 A
130-230 A
160-310 A
275-450 A
400-625 A
Color
Welding
Green
AC – Aluminum, Magnesium
Blue
DC
Steel, Stainless steel,
Yellow
Titanium,
Red
Copper
Violet
Orange
Brown
Stainless steel, Nickel, Non
ferric metals
White
Black
All TIG applications
Grey
All TIG applications
Positive (+)
10-20 A
15-25 A
17-30 A
20-35 A
35-50 A
50-70 A
Amp. AC
45-90 A
65-125 A
80-140 A
150-190 A
180-260 A
240-350 A
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