Metallurgy and Materials Engineering Department, University of Punjab Lahore

1. Group Members:
Shahbaz Ahmed E12-341
Adil Ashraf E12-342
Javaid Iqbal E12-343

2.  May be called GMAW (Gas Metal Arc Welding)
 Avoid cutting in drafty or windy conditions
 Molten pool is shielded by the inert gas
envelope
 Joints are stronger, more ductile, and more
corrosion resistant
 Flux center wire has slag; Solid wire has no
slag, thus eliminating slag inclusion
 Welded metal does not readily distort

3.  MIG is the welding process in
which arc is produced
between the base metal and
the consumable electrode
wire which is provided
through the base metal
through power hose along
with the inert gas for
shielding of the weld bead
whose rates i-e speed of wire
and the gas flow rate can be
controlled from the power
unit…

4. 4
Travel direction
Electrode
1
Arc
2
Weld Puddle
3
Shielding Gas
4
5
Solidified Weld Metal
Generally, drag on thin sheet metal
and push on thicker materials

5.  A GMAW electrode is:
• A metal wire
• Measured by its
diameter
5
GMAW electrodes are
commonly packaged on
spools, reels and coils
ranging from 1lb to 1000lbs

6.  An electric arc
occurs in the gas
filled space between
the electrode wire
and the work piece
6
Electric arcs can
generate temperatures
up to 10,000°F

7.  As the wire electrode
and work piece heat
up and melt, they
form a pool of molten
material called a
weld puddle
 This is what the
welder watches and
manipulates while
welding
7
.045” ER70S-6 at 400
ipm wire feed speed and
28.5 Volts with a 90%

8.  GMAW welding
requires a shielding
gas to protect the
weld puddle
 Shielding gas is
usually CO2, argon,
or a mixture of both
8
The gauges on the
regulator show gas flow

9.  The welder “lays a
bead” of molten
metal that quickly
solidifies into a weld
 The resulting weld is
slag free
9
An aluminum
weld done with the
GMAW process

10.  Cleaning: It is essential that surfaces of the work piece
be thoroughly cleaned by some suitable medium
either mechanically or chemically.
 Position of weld: MIG can be an automatic process or
may be termed as semi automatic process which can
be used at any position of the welding.
 Arc Length: Maintain a Contact Tip to Work Distance
(CTWD) of 3/8” to 1/2”.
 Welding current : DCRP Is almost always used neither
A.C current nor direct current straight polarity should
be used.

11. Penetration: High penetration can be achieved
by Direct current straight polarity.
Joint, Design, preparation and jigging:
It is important that parts to be joint by this process, be
properly designed, prepared and jigged if satisfactory
results are to be assued.
Working operation:
To start, welding the trigger switch is depressed this
start the gas flow which purges the lines.
 Next the electrode which should project ½ inch to ¾
inch from the gas nozzle, is scratched on the work piece.

12.  When arc voltage is established, the controls
operate to energize the feed motor and deliver filler
metal
When using the contactor, the trigger switch is used
for starting and stopping the welding.
The electrode holder is held so that it points ahead
in the direction of welding. To terminate a weld when
no welding current contactor is used, the arc is
broken with a quick snap.

14.  Porosity can be avoided by the purging
inert gas as compared with other processes
MIG has very few defects that’s why it is
used for high tech applications and aviation
industries.
Materials that can be welded:
 MIG welding is useful because you can use
it to weld many different types of metals:
carbon steel, stainless steel, aluminum,
magnesium, copper, nickel, silicon bronze
and other alloys.

15. Defects:
Porosity can be avoided by the purging inert gas as
compared with other processes MIG has very few
defects that’s why it is used for high tech applications
and aviation industries.
Materials that can be welded:
MIG welding is useful because you can use it to weld
many different types of metals: carbon steel, stainless
steel, aluminum, magnesium, copper, nickel, silicon
bronze and other alloys.

16. Inert Gases for Shielding
Argon
Cheap – comes from air
Heavier than air –
blankets weld well
Provides clean welding of
Aluminum and
Magnesium
Best with AC
Helium
Arc voltage is greater
Hotter arc
Deeper Penetration
Fast Speed
Less Distortion
May spatter more than
Argon
Carbon Dioxide
Cooling effect
Low cost
Produces Spatter
Deep penetration
Not same inert
characteristics as Argon
and Helium

17.  Welding can be done in all positions
 High rates of metal deposition
 Excellent filling ability for poor-fit joints
 High weld Quality
 No electrode stub loss
 Less distortion due to narrow, deep weld
profile
 Easier process to learn and use

18.  Welding power source expensive
 Shielding gas expensive
 Higher electrode wire cost
 Most machines require three-phase input power
 Not as versatile as SMAW for maintenance
• Welding cast iron
• Cutting
• Carbon arc torch applications

19.  MIG (metal inert gas) welding is the most
widely used of the arc welding processes,
suitable for everything from hobbies and
small fabrications or repairs, through to
large structures, shipbuilding and robotic
welding.
 MIG can be used on a broad range of
materials and thicknesses.
 MIG is also used extensively in automotive
and general repair workshops.
 MIG welding is widely used in shipbuilding
and ship repair yards.

20.  Always use eye shield before start the
welding
 Always keep your mind on your job
 Always use over coat during the welding
operation
 Always use Helmat during the welding
operation
 Protect your self from the intense heat
 Before start the welding operation parent
matel is cleaned by some suitable method
bither by mechanical or chemical means.

21.  Always use gloves during the welding
 Always use jigs and fixtures during the
welding.
 Preheating may be carried out for
avoiding internal streses.
 Post weld heat tretment is carried on if
the material is stressed internally.
 To avoid from the different welding
defects properly designed and prepare
the objects.