GMAW – MIG Welding

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:

  1. What is MIG Welding?
  2. MIG Welding Equipments.
  3. Working principle of MIG welding.
  4. Modes of GMAW Transfer.
  5. Shielding Gas and Properties.
  6. Gasless GMAW.
  7. Polarity of Electrodes for GMAW.
  8. MAG Welding – Metal Active Gas Welding.
  9. TIG Welding – MIG Welding Comparison.
  10. MIG Welding Advantages and Limitations.
  11. 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.

Circuit diagram of MIG welding equipments
(1) Welding gun (2) Workpiece (3) Power Supply (4) Wire Feed Control Unit (5) Electrode Wire Reel (6) Shielding Gas Cylinder

MIG Welding Equipments:

DC Power Source

MIG welding needs constant voltage DC power source.

Wire Feeder

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

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.

  1. Short Circuit Transfer Mode.
  2. Globular Transfer Mode.
  3. Spray Arc Transfer Mode.

Factors Affecting GMAW Transfer Mode:

  • Shielding gas.
  • Voltage.
  • Current.
  • 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

  • More even welding than globular mode.
  • Not constraint to horizontal surface as no dependency on gravity.
  • Low deposition rate of material.
  • More splatter.

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

  • High material deposition rate.
  • Cheap cost wise, due to use of CO2 instead of Argon.
  • As weld drop falls by gravity. It can be used only for horizontal or flat surface.
  • More splatter.
  • Uneven welding.
  • Causes distortion in workpiece.

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

  • High deposition rate.
  • Good penetration is achieved.
  • Even weld quality and bead.
  • Little splatter.
  • Relatively higher cost shielding gas, Argon, must be used.

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:



  • Process can be used for wide range of metals.
  • MIG welding can be totally automated.
  • Comparatively low-cost method.
  • Easy for new operator.
  • Lower amount of fumes.
  • Not a very portable setup.
  • Outdoors, shielding gas can be inadequate to keep impurities away from weld.
  • Too many parts to maintain.

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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Article by Kiran

Kiran Pagar - Founder of Engiblogger. I get fascinated with Technology advances in world. I love to study and work with those technologies. I am Mechanical Engineer, my main interests are Animation, Software Development and Blogging.
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One Comments

  1. This is a good article to how to use a MIG and I think that you covered the points well, however I think that perhaps a better picture would be better for this article.

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