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GMAW Fundamentals

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GMAW Fundamentals
Gas Metal Arc Welding
Metal Inert Gas
By: Wanda Sue Benton
ESAB University & Florence-Darlington Technical College
Introduction
пЃ¶ GMAW is
defined as arc welding using a
continuously fed consumable electrode and
a shielding gas.
пЃ¶ GMAW is also known as MIG (Metal Inert
Gas).
пЃ¶ Produces high-quality welds
пЃ¶ Yields high productivity
Advantages
пЃ¶ Large
gaps filled or bridged easily
пЃ¶ Welding can be done in all positions
пЃ¶ No slag removal required
пЃ¶ High welding speeds
пЃ¶ High weld quality
пЃ¶ Less distortion of work piece
Types of Metal Transfer
The basic GMAW process includes three
distinctive process techniques:
1.
2.
3.
Short Circuit (Short Arc)
Globular Transfer
Spray Arc Transfer
Short Circuit (Short Arc)
пЃ¶ Operates
at low voltages and welding
current
пЃ¶ Small fast-freezing weld puddle obtained
пЃ¶ Useful in joining thin materials in any
position, as well as thick materials in
vertical and overhead positions
пЃ¶ Metal transfer occurs when an electrical
short circuit is established
Globular Transfer
пЃ¶ Welding
current and wire speed are
increased above maximum for short arc
пЃ¶ Droplets of metal have a greater diameter
than the wire being used
пЃ¶ Spatter present
пЃ¶ Welding is most effectively done in the flat
position when using globular transfer
Spray Arc Transfer
пЃ¶ Occurs
when the current and voltage
settings are increased higher than that used
for Globular Transfer
пЃ¶ Used on thick sections of base material, best
suited for flat position due to large weld
puddle
пЃ¶ Spatter is minimal to none
Manual GMAW Equipment
пЃ¶ Three
major elements are :
1.) Welding torch and accessories
2.) Welding control & Wire feed motor
3.) Power Source
пЃ¶ GMAW
equipment can be used either
manually or automatically
WIRE CONTROL
&
WIRE FEED MOTOR
POWER SOURCE
Welding Torch & Accessories
пЃ¶ The
welding torch guides the wire and
shielding gas to the weld zone.
пЃ¶ Brings welding power to the wire also
пЃ¶ Major components/parts of the torch are the
contact tip, shielding gas nozzle, gas
diffuser, and the wire conduit
GAS DIFFUSER
NOZZLE
TRIGGER
CONTACT TIP
INSTALLED
COMPONENTS
Welding Control & Wire
Feed Motor
пЃ¶ Welding
control & Wire feed motor are
combined into one unit
пЃ¶ Main function is to pull the wire from the
spool and feed it to the arc
пЃ¶ Controls wire feed speed and regulates the
starting and stopping of wire feed
пЃ¶ Wire feed speed controls Amperage
WIRE FEEDER
Power Source
пЃ¶ Almost
all GMAW is done with reverse
polarity also known as DCEP
пЃ¶ Positive (+) lead is connected to the torch
пЃ¶ Negative (-) lead is connected to the work
piece
пЃ¶ Provides a relatively consistent voltage to
the arc
пЃ¶ Arc Voltage is the voltage between the end
of the wire and the work piece
POSITIVE
TERMINAL
NEGATIVE
TERMINAL
Shielding Gases
пЃ¶ Purpose
of shielding gas is the protect the
weld area from the contaminants in the
atmosphere
пЃ¶ Gas can be Inert, Reactive, or Mixtures of
both
пЃ¶ Gas flow rate is between 25-35 CFH
пЃ¶ Argon, Helium, and Carbon Dioxide are the
main three gases used in GMAW
FLOW METER
CFH PRESSURE
ADJUSTMENT
KNOB
CYLCINDER
PRESSURE
GAUGE
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