GMAW FundamentalsGMAW Fundamentals
Gas Metal Arc Welding
Metal Inert Gas
By: Wanda Sue Benton
ESAB University & Florence-Darlington Technical College
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 weldsYields high productivity
AdvantagesAdvantages
Large gaps filled or bridged easilyWelding can be done in all positionsNo slag removal requiredHigh welding speedsHigh weld qualityLess distortion of work piece
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
Short Circuit (Short Arc)Short Circuit (Short Arc)
Operates at low voltages and welding current
Small fast-freezing weld puddle obtainedUseful 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
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
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
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
WIRE CONTROL&
WIRE FEED MOTOR
POWER SOURCE
Welding Torch & AccessoriesWelding Torch & Accessories
The welding torch guides the wire and shielding gas to the weld zone.
Brings welding power to the wire alsoMajor components/parts of the torch are the
contact tip, shielding gas nozzle, gas diffuser, and the wire conduit
TRIGGER
INSTALLED
COMPONENTS
NOZZLE
CONTACT TIP
GAS DIFFUSER
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
WIRE FEEDER
Power SourcePower Source
Almost all GMAW is done with reverse polarity also known as DCEP
Positive (+) lead is connected to the torchNegative (-) lead is connected to the work
pieceProvides a relatively consistent voltage to the
arcArc Voltage is the voltage between the end of
the wire and the work piece
POSITIVETERMINAL
NEGATIVETERMINAL
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 CFHArgon, Helium, and Carbon Dioxide are the
main three gases used in GMAW
FLOW METER
CYLCINDERPRESSUREGAUGE
CFH PRESSURE ADJUSTMENT KNOB