1. GTAW

2. 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

3. 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.

4. Shielding gases inert Argon most popular Helium
Argon combined with Helium

5. GTAW Applications virtually all metals can be welded aluminum titanium
stainless steels
carbon steels
copper
mild steels
magnesium

6. GTAW Equipment

7. 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

8. the arc reaches temperatures of 11,000 degrees Fahrenheit
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

9. 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)

10. 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

11. 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)

12. Typical Current Ranges

13. GTAW Tungsten Electrode Preparation

14. GTAW Torch Parts

15. 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