Gas metal arc welding

Gas metal arc welding (GMAW)

1. GMAW FundamentalsGMAW Fundamentals
Gas Metal Arc Welding
Metal Inert Gas
By:
Satha Siva Pandian . M
2
nd
yr MECHANICAL “B”

2. IntroductionIntroduction
GMAW is defined as arc welding using a
continuously fed consumable electrode and
a shielding gas.
GMAW is also known as MIG (Metal Inert
Gas).
Produces high-quality welds
Yields high productivity

3. Principles of the GMAW Principles of the GMAW
ProcessProcess

5. Types of Metal TransferTypes of Metal Transfer
The basic GMAW process includes three
distinctive process techniques:
1.Short Circuit (Short Arc)
2.Globular Transfer
3.Spray Arc Transfer

7. Short Circuit (Short Arc)Short Circuit (Short Arc)
Operates at low voltages and welding
current
Small fast-freezing weld puddle obtained
Useful in joining thin materials in any
position, as well as thick materials in
vertical and overhead positions
Metal transfer occurs when an electrical
short circuit is established

8. Globular TransferGlobular Transfer
Welding current and wire speed are
increased above maximum for short arc
Droplets of metal have a greater diameter
than the wire being used
Spatter present
Welding is most effectively done in the flat
position when using globular transfer

9. Spray Arc TransferSpray Arc Transfer
Occurs when the current and voltage
settings are increased higher than that used
for Globular Transfer
Used on thick sections of base material, best
suited for flat position due to large weld
puddle
Spatter is minimal to none

10. Manual GMAW EquipmentManual GMAW Equipment
Three major elements are :
1.) Welding torch and accessories
2.) Welding control & Wire feed motor
3.) Power Source
GMAW equipment can be used either
manually or automatically

12. WIRE CONTROL
&
WIRE FEED MOTOR
POWER SOURCE

13. Welding Torch & AccessoriesWelding Torch & Accessories
The welding torch guides the wire and
shielding gas to the weld zone.
Brings welding power to the wire also
Major components/parts of the torch are the
contact tip, shielding gas nozzle, gas
diffuser, and the wire conduit

14. TRIGGER
INSTALLED
COMPONENTS
NOZZLE
CONTACT TIP
GAS DIFFUSER

16. Welding Control & Wire Welding Control & Wire
Feed MotorFeed Motor
Welding control & Wire feed motor are
combined into one unit
Main function is to pull the wire from the
spool and feed it to the arc
Controls wire feed speed and regulates the
starting and stopping of wire feed
Wire feed speed controls Amperage

17. WIRE FEEDER

19. Power SourcePower Source
Almost all GMAW is done with reverse
polarity also known as DCEP
Positive (+) lead is connected to the torch
Negative (-) lead is connected to the work
piece
Provides a relatively consistent voltage to
the arc
Arc Voltage is the voltage between the end
of the wire and the work piece

20. POSITIVE
TERMINAL
NEGATIVE
TERMINAL

21. Shielding GasesShielding Gases
Purpose of shielding gas is the protect the
weld area from the contaminants in the
atmosphere
Gas can be Inert, Reactive, or Mixtures of
both
Gas flow rate is between 25-35 CFH
Argon, Helium, and Carbon Dioxide are the
main three gases used in GMAW

22. Shielding gas can affect
–Weld bead shape
–Arc heat, stability, and
starting
–Surface tension
–Drop size
–Puddle flow
–Spatter
Ar Ar-He
He CO
2

23. FLOW METER
CYLCINDER
PRESSURE
GAUGE
CFH PRESSURE
ADJUSTMENT
KNOB

25. AdvantagesAdvantages
Large gaps filled or bridged easily
Welding can be done in all positions
No slag removal required
High welding speeds
High weld quality
Less distortion of work piece

26. DisadvantagesDisadvantages
CostCost
Portability Portability
Outdoor Welding Outdoor Welding
Clean Base MaterialClean Base Material

27. Thank You!Thank You!