Transcript GMAW Fundamentals

GMAW Fundamentals
Gas Metal Arc Welding
Metal Inert Gas
By: Wanda Sue Benton
ESAB University & Florence-Darlington Technical College
Introduction
 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
Advantages
 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
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)
 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
Globular 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 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 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 & 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
GAS DIFFUSER
NOZZLE
TRIGGER
CONTACT TIP
INSTALLED
COMPONENTS
Welding Control & Wire
Feed 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 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
POSITIVE
TERMINAL
NEGATIVE
TERMINAL
Shielding 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
FLOW METER
CFH PRESSURE
ADJUSTMENT
KNOB
CYLCINDER
PRESSURE
GAUGE