Skip to main content

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.

Comments

Post a Comment

Popular posts from this blog

Electroslag Welding (ESW)

ELECTROSLAG WELDING The Process :- Electroslag welding (ESW) is a process that melts and joins metals by heating them with a pool of molten slag held between the metals and continuously feeding a filler wire electrode into it, as shown in Figure. The weld pool is covered with molten slag and moves upward as welding progresses. A pair of water-cooled copper shoes, one in the front of the workpiece and one behind it, keeps the weld pool and the molten slag from breaking out. Similar to SAW , the molten slag in ESW protects the weld metal from air and refines it. Strictly speaking, however, ESW is not an arc welding process, because the arc exists only during the initiation period of the process, that is, when the arc heats up the flux and melts it. The arc is then extinguished, and the resistance heating generated by the electric current passing through the slag keeps it molten. In order to make heating more uniform, the electrode is often oscillated, especially when welding thicker...
Post a Comment
Read more

Gas–Tungsten arc welding (GTAW)

GTAW The Process Gas–tungsten arc welding (GTAW) is a process that melts and joins metals by heating them with an arc established between a non consumable tungsten electrode and the metals, as shown in Figure. The torch holding the tungsten electrode is connected to a shielding gas cylinder as well as one terminal of the power source, as shown in Figure a . The tungsten electrode is usually in contact with a water-cooled copper tube, called the contact tube, as shown in Figure b , which is connected to the welding cable (cable 1) from the terminal. This allows both the welding current from the power source to enter the electrode and the electrode to be cooled to prevent overheating.The workpiece is connected to the other terminal of the power source through a different cable (cable 2). The shielding gas goes through the torch body and is directed by a nozzle toward the weld pool to protect it from the air. Protection fro...
Post a Comment
Read more

Electron Beam Welding (EBW)

ELECTRON BEAM WELDING The Process:- Electron beam welding (EBW) is a process that melts and joins metals by heating them with an electron beam. As shown in Figure 1a, the cathode of the electron beam gun is a negatively charged filament.When heated up to its thermionic emission temperature, this filament emits electrons. These electrons are accelerated by the electric field between a negatively charged bias electrode (located slightly below the cathode) and the anode. They pass through the hole in the anode and are focused by an electromagnetic coil to a point at the workpiece surface. The beam currents and the accelerating voltages employed for typical EBW vary over the ranges of 50–1000mA and 30–175kV, respectively. An electron beam of very high intensity can vaporize the metal and form a vapour hole during welding, that is, a keyhole, as depicted in Figure 1b. 1  Electron beam welding: (a) process; (b) keyhole. Modified from Arata Figure 2 shows that the beam diameter...
Post a Comment
Read more