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Gas–Metal Arc Welding (GMAW)

GAS–METAL ARC WELDING (GMAW)

 The Process:-
Gas–metal arc welding (GMAW) is a process that melts and joins metals by heating them with an arc established between a continuously fed filler wire electrode and the metals, as shown in Figure. Shielding of the arc and the molten weld pool is often obtained by using inert gases such as argon and
helium, and this is why GMAW is also called the metal–inert gas (MIG) welding process. Since non inert gases, particularly CO2, are also used,GMAW seems a more appropriate name. This is the most widely used arc welding process for aluminium alloys. Unlike in GTAW, DCEP is used in MAW. A stable arc, smooth metal transfer with low spatter loss and good weld penetration can be obtained.With DCEN or AC, however, metal transfer is erratic.
Gas-Metal Arc Welding
Gas–metal arc welding: (a) overall process; (b) welding area enlarged.
GMAW
What Is GMAW ?
•A Fusion Welding Process – Semi Automatic
•Arc Between Consumable Electrode &Work
•Arc Generated by Electric Energy From a Rectifier / Thyristor / Inverter
•Filler Metal As Electrode Continuously fed From Layer Wound Spool.
•Filler Wire Driven to Arc By Wire Feeder through Welding Torch
•Arc & Molten Pool Shielded by Inert Gas through Torch / Nozzle 

Types Of Wire Feeding In GMAW

•Push Type
–Wire fed in to The torch by Pushing through Flexible Conduit From A Remote Spool
•Pull Type
–Feed Rollers Mounted on The Torch Handle Pulls the Wire From A Remote spool
•Self Contained
–Wire Feeder & The Spool On the Torch

Shielding Gases For GMAW
•MIG:      Argon Or Helium
          For SS, CS, LAS & Non-ferrous Mt & Al
•MIG:     Ar + 1 to 2 % O2, Wire With Add. Mn & Si
         For SS, CS, LAS & Non-ferrous Mt & Al
•MIG:     Ar + 5 to 20 % Co2 Wire With Add. Mn & Si
         For SS, CS, LAS & Non-ferrous Mt & Al
•MAG:   Co2 With Solid Wire
         For CS & LAS
•FCAW: Co2 With Flux Cored Wire
       For CS, LAS & SS  Overlay 

Advantages and Disadvantages of GMAW:-
Like GTAW,GMAW can be very clean when using an inert shielding gas.The main advantage of GMAW over GTAW is the much higher deposition rate, which allows thicker workpieces to be welded at higher welding speeds. The dual-torch and twin-wire processes further increase the deposition rate of GMAW . The skill to maintain a very short and yet stable arc in GTAW is not required. However, GMAW guns can be bulky and difficult-to-reach small areas or corners.

 GMAW Capabilities:-

  • It gives more deposition rate than SMAW and GTAW as continuous filler wire is used.
  • Contamination of weld metal is less.
  • Different modes of metal transfers can be achieved.
  • Difficult to weld metals like aluminium, copper etc. can be weld with this process


 GMAW Limitations:-

  • Spatter level is more.
  • Improper gaseous shielding leads to surface defects.

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