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

Oxyacetylene Welding (OAW)

OXYACETYLENE WELDING The Process:- Gas welding is a welding process that melts and joins metals by heating them with a flame caused by the reaction between a fuel gas and oxygen. Oxyacetylene welding (OAW), shown in Figure is the most commonly used gas welding process because of its high flame temperature. A flux may be used to deoxidize and cleanse the weld metal. The flux melts, solidifies, and forms a slag skin on the resultant weld metal. Three different types of flames in oxyacetylene welding: neutral, reducing, and oxidizing , which are described next. Advantages and Disadvantages :- The main advantage of the oxyacetylene welding process is that the equipment is simple, portable, and inexpensive.Therefore, it is convenient for maintenance and repair applications. However, due to its limited power density, the welding speed is very low and the total heat input per unit length of the weld is rather high, resulting in large heat-affected zones and severe distortion.The...
Post a Comment
Read more

Flux-Core Arc Welding (FCAW)

FLUX-CORE ARC WELDING (FCAW) The Process:- Flux-core arc welding (FCAW) is similar to GMAW , as shown in Figure a. However, as shown in Figure b, the wire electrode is flux cored rather than solid; that is, the electrode is a metal tube with flux wrapped inside. The functions of the flux are similar to those of the electrode covering in SMAW , including protecting the molten metal from air. The use of additional shielding gas is optional. Flux-Core Arc Welding (FCAW) (a) overall process (b) welding area enlarged Advantages of FCAW:- High deposition rates Deeper penetration than SMAW High quality welds Less pre-cleaning than GMAW Slag covering helps with out-of-position welds Self-shielded FCAW is draft tolerant Disadvantages of FCAW:- Slag must be removed Higher fume generation than GMAW and SAW Spatter Equipment is more expensive and complex than SMAW FCAW wire is more expensive Types of continuous wire electrodes:-   Read ...
Post a Comment
Read more

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