GTAW
Definitions







GTAW
gas tungsten arc welding
an electric arc between a non-consumable
electrode and the work piece protected by a
shielding gas
TIG
tungsten inert gas
Inert Gas
a gas that does not chemically combine or react
with another substance


Contamination
tungsten non-consumable electrode coming into
contact with the base metal.
 inert gas not present.
 both these conditions lead to not only
contamination of the tungsten electrode, but also
defects in the weld itself.


Shielding gases
inert
 Argon most popular
 Helium
 Argon combined with Helium
GTAW

Applications

virtually all metals can be welded
aluminum
titanium
stainless steels
carbon steels
copper
mild steels
magnesium







GTAW Equipment
GTAW Welding Process

similar to oxy-fuel welding
 heat source is held in one hand
 if filler is required it is added with the other hand
 requires much more skills than the typical manual
or semi-automatic welding

non-consumable tungsten electrode generates arc
 tungsten electrode has a melting point of 6170
degrees Fahrenheit (the highest melting point of
all the metals)
 the material is also the same type of material used
as a filament in a regular light bulb
 electrode DOES NOT touch the base metal or the
molten puddle


the arc reaches temperatures of 11,000
degrees Fahrenheit
tungsten electrode normally does not melt
in these temperatures because:
• it has the ability to conduct heat well
• touch handle is a good heat conductor

Welding Aluminum or Magnesium

uses AC ( alternating current)
electrons flow in one direction, stop and flow the
other direction for the same period of time
(60-cycle means electrons change directions 60
times per second)
this constant current reversal creates base metal
heating for an instant (negative electron flow),
while metal cleaning the next instant (electron
positive flow)
heat from the arc is more evenly distributed
between the tungsten and the base metal
pure tungsten electrode is used (green end)





Welding other materials

Direct Current Electrode Negative (DCEN)
(same as DCSP in SMAW)
electrons flow from electrode to base metal which
transfers 70% of the heat from the arc to the base
metal
Direct Current Electrode Positive (DCEP)
(same as DCRP in SMAW)
rarely used in GTAW since it produces shallow
penetration and slow travel speeds
this is just the opposite of SMAW and GMAW
which is mostly done with DCRP













electrode does not contain any flux, therefore a
shielding gas is used to protect the weld
if electrode comes in contact with the base metal,
it will become contaminated
after contamination, the electrode must be cleaned
this is done on a grinding wheel (point for
stainless steel, flat for aluminum)
Argon is most common shielding gas
setting is 20 CFH, but may be as high as 30 CFH
when welding aluminum
2% thoriated tungsten electrode used (red end)
Typical Current Ranges
GTAW Tungsten Electrode
Preparation
GTAW Torch Parts
Preparing to Weld










Follow same precautions as GMAW and SMAW
number 10 shade is required (minimum)
always clean base metal prior to welding
clean aluminum with aluminum brush only
clean stainless steel with stainless steel brush only
choose the correct filler for the base metal
always wear gloves on both hands
always hang torch up properly when not in use
always shut off shielding gas when not in use
magnetic fields can from high currents can affect
pacemakers operations