GTAW/TIG welding involves an arc between a non-consumable tungsten electrode and the workpiece, with an inert gas shielding the weld area from contamination. It allows for welding of many materials with high quality and precision. The document discusses the equipment, parameters, applications, materials and safety considerations for GTAW welding. It notes the process provides welder control but is also more complex and slower than alternatives like GMAW.

1. GTAW/TIG WELDING
Made By:
Farasat Ali Jutt 14MME-S1-317
Abdul Hannan 14MME-S1-319
Hamza Munir 14MME-S1-320
Aoun Hussnain 14MME-S1-328
Jahanzaib Mukhtar 14MME-S1-334
Uzair Naveed Chishti 14MME-S1-350

2. Contents
 What is TIG/GTAW welding?
 Operation
 Equipment
 Welding Parameters
 Applications
 Materials
 Safety
 Advantages and limitations
 Conclusion

3. What is GTAW welding?
 Gas tungsten arc welding (GTAW) also known as tungsten inert gas (TIG) welding is
an arc welding process that uses a non-consumable tungsten electrode to lay the
weld.
 The weld area is protected from atmospheric contamination example oxygen by an
inert shielding gas either argon, helium or a mixture of both.
 A filler metal is also normally used. A constant-current welding power supply
produces energy which is conducted across the arc through plasma.
 Used to weld thin sections of stainless steel as well non-ferrous metals such as Al,
Mg and Cu alloys.

4. Operation
 GTAW is considered the most difficult among welding processes, because the welder
must maintain a short arc length, great care and skill are required to prevent contact
between the electrode and the workpiece. Both hands are used one to feed the filler
metal and the other to move the welding torch.
 To strike the welding arc, a high frequency generator provides a spark which allows
the arc to be initiated while the electrode and the workpiece are separated, typically
about 1.5–3 mm apart.
 An alternate way to initiate the arc is the "scratch start". Scratching the electrode
against the work with the power on also serve to strike an arc. However, scratching can
cause contamination of the weld and electrode. Some GTAW equipment is capable of
a mode called lift arc.
 When a spark is present, the equipment immediately increases power and converting
the spark to a full arc.
 The welder moves the torch in a small circle to create a welding pool, the size of which
depends on the size of the electrode and the amount of current

5. Operation
 The operator then moves the torch back slightly and tilts it backward about 10–15
degrees from vertical while maintaining constant separation.
 Filler metal is added manually to the front end of the weld pool.
 As the weld nears completion, the arc current is often gradually reduced to allow
the weld crater to solidify and prevent the formation of crater cracks at the end of
the weld.

6. Equipment
1. Power supply
2. Welding Torch
3. Electrodes
4. Shielding gas

7. 1. Power Supply
 Gas tungsten arc welding uses a constant current power source, meaning that the
current remains relatively constant, even if the arc distance and voltage change.
This is important because most applications of GTAW are manual or semiautomatic
and maintaining arc distance is difficult.
 GTAW can use a positive direct current, negative direct current or an alternating
current, depending on the power supply set up.

8. 1. Power Supply
 DCEN causes a stream of electrons to collide with the surface, generating large
amounts of heat. This creates a deep, narrow weld. Used for steel, nickel, titanium
etc.
 In DCEP the electrode is connected to the positive power supply terminal,
positively charged ions flow from the base metal to the tip of the electrode instead,
so the electrode overheats. A longer electrode is used to prevent softening. A
shallow, wide weld is produced from this mode, with minimum heat input.
 Alternating current, commonly used when welding aluminum and magnesium
manually or semi automatically. It gives a combination of negative and positive
modes, giving a cleaning effect and imparts a lot of heat as well.

9. 2. Welding Torch
 GTAW welding torches are designed for either automatic or manual operation and
are equipped with cooling systems using air or water. The torches are connected to
the power supply and shielding gas source with cables.
 The internal metal parts of a torch are made of hard alloys of copper/brass to
transmit current and heat. The tungsten electrode must be held firmly in the center
of the torch with an appropriately sized collet, and ports around the electrode
provide a constant flow of shielding gas. The size of the welding torch nozzle
depends on the amount of shielded area desired.
 Collets as well as the size of the gas nozzle will depend upon the diameter of the
electrode.
 The body of the torch is made of heat resistant, insulating plastics covering the
metal components while the nozzle is made up of ceramic material usually
(alumina).

10. 3. Electrodes
 The electrode used in GTAW is made of tungsten or a tungsten alloy, because
tungsten has the highest melting temperature among pure metals, at 3,422 °C. The
electrode is not consumed during welding, though some erosion can occur.
Electrodes can have either a clean finish or a ground finish.
 A number of tungsten alloys have been standardized by the International
Organization for Standardization and the American Welding Society.
 Pure tungsten electrodes (WP or EWP) are general purpose and low cost
electrodes.
 Cerium oxide or lanthanum oxide as an alloying element improves arc stability and
ease of starting while decreasing burn-off.
 Electrodes containing zirconium oxide increase the current capacity while
improving arc stability and starting and increasing electrode life.

11. 3. Electrodes
 Thorium oxide alloy electrodes were designed for DC applications and can
withstand somewhat higher temperatures while providing many of the benefits of
other alloys. However, it is somewhat radioactive.

12. 4. Shielding gas
 Shielding gases are necessary in GTAW to protect the welding area from
atmospheric gases such as nitrogen and oxygen, which can cause fusion defects,
porosity, and weld metal embrittlement. The gas also transfers heat from the
tungsten electrode to the metal, and it helps start and maintain a stable arc.
 The selection of a shielding gas depends on several factors, including the type of
material being welded, joint design, and desired final weld appearance.
 Argon is the most commonly used shielding gas for GTAW, since it helps prevent
defects due to a varying arc length. When used with alternating current, the use of
argon results in high weld quality and good appearance.
 Helium another shielding gas is most often used to increase the weld penetration
in a joint, to increase the welding speed, and to weld metals with high heat
conductivity, such as copper and aluminum. A significant disadvantage is the
difficulty of striking an arc with helium gas, and the decreased weld quality
associated with a varying arc length.

13. 4. Shielding gas
 Argon-helium mixtures are also utilized in GTAW, since they can increase control of
the heat input while maintaining the benefits of using argon. Normally, the
mixtures are made with helium 75% and argon 25%. These mixtures increase the
speed and quality of the AC welding of aluminum, and also make it easier to strike
an arc.
 Another shielding gas mixture, argon-hydrogen, is used in the mechanized welding
of light gauge stainless steel, but because hydrogen can cause porosity, its uses are
limited.

14. Welding Parameters
1. Current
The current is adjusted proportionally to the tungsten electrodes diameter being
used. The higher the current the deeper the penetration and fusion. Too much current
leads to spatter, too less current leads to sticking of filler metal.
2. Voltage
The voltage of the TIG is variable only by the type of gas being used and changes in
arc length. Can be fixed or adjusted accordingly depending on equipment.
3. Polarity
The polarity used for steels is always DCEN as most of the heat is concentrated at the
positive pole, this is required to keep the tungsten electrode at the cool end of the arc.
When welding aluminum and its alloys AC current is used.
4. Pulsed current
The welding current rapidly alternates between two levels. The higher current state is
known as the pulse current, while the lower current level is called the background
current. During pulse current, the weld is heated and fusion occurs but in the
background current the weld area is cooled and solidified.

15. Applications
 While the aerospace industry is one of the primary users of gas tungsten arc
welding, the process is used in a number of other areas. Many industries use GTAW
for welding thin workpieces, especially nonferrous metals. It is used e in the
manufacture of space vehicles, and is also employed to weld thin-wall tubing such
as those used in the bicycle industry. In addition, GTAW is often used to make root
or first pass welds.
 It is used to repair tools and dies and for maintenance purposes.
 No other welding process permits the welding of so many alloys in so many
product configurations.
 Filler metal alloys, such as elemental aluminum and chromium, can be lost through
the electric arc from volatilization. This loss does not occur with the GTAW process.
Because the resulting welds have the same chemical integrity as the original base
metal.
 GTAW welds are highly resistant to corrosion and cracking over long time periods,
GTAW is the welding procedure of choice for critical welding operations like
sealing spent nuclear fuel canisters before burial.

16. Materials
 Gas tungsten arc welding is most commonly used to weld stainless steel and
nonferrous materials, such as aluminum and magnesium, but it can be applied to
nearly all metals, with notable exceptions being lead and zinc. Its applications
involving carbon steels are limited not because of process restrictions, but because
of the existence of more economical steel welding techniques, such as GMAW and
SMAW. Furthermore, GTAW can be performed in a variety of other-than-flat
positions, depending on the skill of the welder and the materials being welded.
 For Al and Mg alloys, power supply is of concern (AC or DCEP) must be used which
makes cleaning easier.
 For GTAW of carbon and stainless steels, the selection of a filler material is
important to prevent excessive porosity. A DCEN power source is normally used,
and thoriated electrodes, tapered to a sharp point, are recommended. Pure argon
is used for thin workpieces, but helium can be introduced as thickness increases.
 For copper alloys shielding gas is provided on the root side of the weld and special
backing tape is used to prevent air reaching molten metal.

17. Safety
 GTAW can be dangerous if proper precautions are not taken. The process produces
intense ultraviolet radiation which can cause skin cancer. Flying sparks and droplets
of molten metal can cause severe burns and start a fire if flammable material is
nearby.
 It is essential that the welder wear suitable protective clothing, including leather
gloves, jacket and a suitable welding helmet to prevent retinal damage called arc
eye.
 Additionally, the tungsten electrode is heated to a white hot state adding greatly to
the total radiated light and heat energy. Transparent welding curtains dyed in order
to block UV radiation are used for shielding purpose.
 Ventilation is necessary to protect the welder due to the presence of harmful
particulates and gases such as ozone or poisonous phosgene.

18. Advantages and Limitations
Advantages
 Grants welder more control over the
weld allowing for stronger welds
compared to SMAW and GMAW.
 Used in all positions even with
intricate geometries.
 No flux is required as shielding is
done by an inert gas.
 Used for nearly all metal and alloys
except zinc and lead.
 No gas or fumes is generated in this
welding.
Limitations
 More complex and difficult to master.
 Significantly slower than other
welding techniques.
 Lowest deposition rates compared to
all other arc welding techniques.
 Brighter UV rays are generated this
can lead to cell deterioration and
cancer in longer run.
 If the amount of current used
exceeds the capability of the
electrode, tungsten inclusions in the
weld may result known as tungsten
spitting.

19. Advantages and Limitations
Advantages
 GTAW welding is preferred because
of its low-hydrogen properties and
the match of mechanical and
chemical properties with the base
material.
 Higher weld quality can be
maintained by cleaning operations
which are free from defects.
 Can be used with or without filler
metal.
Disadvantages
 If the electrode is not well protected
by the gas shield it can become dirty
or contaminated. This often causes
the welding arc to become unstable,
requiring that electrode be
grounded.
 Low heat input can limit penetration
while high heat input leads to
excessive penetration and spattering.
 This process is costly compared to
other arc welding processes.

20. Conclusion
 GTAW is preferred over other arc welding processes due to it being able to weld
almost all metals/alloys. It also have a wide range of electrodes to be used
depending on the workpiece. Can weld small cross section pipes and tubes.
Despite it being costly we cannot ignore its many advantages. It even has good
precision thus this welding technique is also used in aerospace industry.
Technology is advancing every year and it is possible to find even better
techniques however we are stuck with it for the time being.
No questions shall be entertained.
Best of luck
THANK YOU