GMAW is Gas Metal Arc welding or MIG or Metal Inert Gas Welding. This is most popular welding process among Modern Welding Technologies.
Article Coverage – GMAW:
- What is MIG Welding?
- MIG Welding Equipments.
- Working principle of MIG welding.
- Modes of GMAW Transfer.
- Shielding Gas and Properties.
- Gasless GMAW.
- Polarity of Electrodes for GMAW.
- MAG Welding – Metal Active Gas Welding.
- TIG Welding – MIG Welding Comparison.
- MIG Welding Advantages and Limitations.
- MIG Welding Applications.
What is MIG Welding?
MIG welding or Gas Metal Arc Welding or GMAW is welding process in which fusion of workpiece and filler metal occurs due to heat generated by electric arc under the shield of inert gas. Here, filler metal is endless metal wire which itself acts as electrode.
MIG Welding Equipments:
DC Power Source
MIG welding needs constant voltage DC power source.
This is constant speed wire feeder that feeds the wire to welding gun as it is consumed for welding. This is the element that makes MIG welding far efficient and better than stick welding.
Welding gun holds electrode, provides ports for fitting gas hoses and eases the welding process with its ergonomic shape.
Gas Cylinder and Hoses
Unlike Gas Welding, here gas cylinder contains non-explosive inert gas. Hoses are needed for carrying gas from cylinder to welding gun.
Working Principle of MIG Welding
Electrode gets heated by electric current and melts. Molten electrode is used as filler for welding process. To continue this process in loop, a reel of consumable electrode wire is used. Weld puddle is always covered under shield of inert gas to avoid any inclusion of atmospheric gases in the weld.
GMAW Transfer Modes:
What is GMAW Transfer Mode?
It is the mode by which electrode metal wire transfers from gun to weld puddle and settle to complete the join.
- Short Circuit Transfer Mode.
- Globular Transfer Mode.
- Spray Arc Transfer Mode.
Factors Affecting GMAW Transfer Mode:
- Shielding gas.
- Electrode diameter.
- Feed speed of electrode wire.
Short Circuit Transfer Mode
In short-circuit transfer, electrode directly comes in contact with workpiece and electrode tip gets heated. Then molten tip detaches and becomes part of weld. This cycle repeats many times in each second to complete the welding.
Advantages of Short Circuit Transfer Mode
Disadvantages of Short Circuit Transfer Mode
Globular Transfer Mode
Electrode melts and a droplet of molten metal gets collected at tip of electrode. This drop falls into puddle by gravity. It uses CO2 – carbon-dioxide as shielding gas.
Advantages of Globular Transfer Mode
Disadvantages of Globular Transfer Mode
Spray Arc Transfer Mode
This is most desirable mode of GMAW transfer. Spray of molten metal runs from tip of electrode to puddle along the welding arc.
Advantages of Spray Arc Transfer Mode
Disadvantages of Spray Arc Transfer Mode
Shielding Gas and Properties for MIG Welding
Shielding gas protects the weld quality by isolating the weld from atmospheric contents like oxygen, dust etc. Most desirable gas for MIG welding is Argon. It is heavy and covers weld puddle properly. Apart from Argon, Helium, Carbon dioxide and mixture of CO2 and Argon are used.
Gasless GMAW – MIG Welding:
GMAW is Gas Metal Arc Welding. Name GMAW denotes that gas must be used in the process.
Purpose of using gas in GMAW is to shield weld puddle. This purpose can be solved by using flux coated electrode reel. When arc is stuck between electrode and workpiece, flux gets converted into gas which covers the weld puddle. So, no need to have shielding gas, hence called gasless GMAW.
Electrode Polarity for GMAW:
Normal GMAW: Electrode positive.
Gasless GMAW: Electrode negative.
MAG – MIG Welding Comparison
MAG is Metal Active Gas Welding.
In MIG welding, shielding gas does not take any part in welding and that is necessary too. But in MAG, gas participation is expected to complete the weld. Depending upon the workpiece, electrode composition Active Gas can be used.
TIG – MIG Welding Comparison
TIG welding is Tungsten Inert Gas Welding or GTAW.
Major difference between TIG and MIG welding is electrode. TIG uses, non consumable tungsten electrode. Tungsten has very high melting point. So, arc formed between Tungsten electrode and work generates the heat enough to melt work and filler rod.
Apart from that, TIG welding is considered to be one of most difficult welding process while MIG is considered to be easiest.
Advantages and Disadvantages of MIG Welding:
MIG Welding Applications:
- Being low-cost, easy and wide material coverage MIG welding is very useful in Automotive industry.
- For any workshop, MIG welding is equally important as that of Lathe Machine or Drilling Machine.
- Pipe welding.
- Robotic welding. MIG welding can be totally automated to produce the output at very high rate and quality.
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