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Welding Starter Guide : Metal Inert Gas Welding (MIG)

MIG welding

MIG welding, or metal inert gas welding, is the most popular welding process today. If you caught our post on “Welding Deconstruction with DIY Network,” you already know that most robotic manufacturing use the MIG process. MIG welds are even responsible for keeping your car together!

So what is MIG welding? How does it work? What gases are commonly used in MIG welding? These questions and more are answered in this welding starter guide.

This guide was inspired by content from GoWelding.org, one of the ultimate resources for understanding the core aspects of welding. 

What Is Metal Inert Gas Welding?

Metal Inert Gas welding, or MIG, is a “semi-automated” process developed in the 1940s. “Semi-automated” in that the MIG welding machine “will continuously keep filling the joint being welded” while the welder uses his/her skills to create the perfect welds. Both man/woman and machine work in the MIG welding process.

The MIG welding machine controls the wire feed by “feeding the wire from a spool to the weld joint.” The welder pulls the trigger on the handle to get the wire going.

Are there other names for MIG welding?

Whether you’re looking for a welding job or trying to pass a written welding test, it’s important to know the different names for MIG welding.

Gas Metal Arc (GMA) – the original name for MIG welding, also known as Gas Metal Arc Welding (GMAW). The names are based on the type of gas used: inert gas or non-inert gas.

How does the MIG welding process work? 

There are three components to MIG welding:

  1. Electricity – needed to produce heat
  2. Electrode – needed to fill the joint
  3. Shielding gas – needed to protect the weld from air


MIG welding is done using a very small electrode that is fed continuously, while the operator controls the amount of weld being done. In some cases when a robot takes over this process, it becomes automatic welding.


What is the right MIG electrode type to use?

While there are other factors to consider, the main factor for choosing an electrode is the type of metal being used. The electrode you use should match the type of metal you’re welding. Other factors to consider include:

  • Type of transfer
  • Position to be welded
  • Resistance to abrasion

Commonly, the ER 70s-6 wire is used when welding carbon steel.

The manufactures of these electrodes use a standard code to identify the type of electrode. For example the code on the label ER 70S-6 represents the following:

  • ER– An electrode or filler rod that is used in either a wire feed or TIG welding.
  • 70– A minimum of 70,000 pounds of tensile strength per square inch of weld.
  • S -Solid wire.
  • 6– The amount of deoxidizing agent and cleansing agent on the electrode.


MIG electrodes range in thickness from .023 to .045. Common sizes are:

  • .023
  • .030
  • .035
  • .045

Tell me about common MIG welding gases.

  • Argon
  • CO2 / Carbon Dioxide
  • O2 / Oxygen
  • Helium (least common)

The type of gas you use should be based on the welding wire being used, what is recommended by the manufacturers of that wire, and/or the cost of the gas. You can also get help from your welding supply store.

Which gas should be used with each metal?

Here is a basic guideline for choosing which gas to use on certain metals.



Carbon steel
  yes, can be used alone   yes – mixture of 2-25% carbon dioxide and the rest argon

Stainless steel
      C2 or 2% carbon dioxide and 98% argon – or –90% helium, 7.5% argon and 2.5% carbon dioxide

yes, can be used alone     if aluminum is thicker than a 1/2 inch, you can add helium to the mix

Exotic metals (such as copper, copper alloys, magnesium, nickel, nickel alloys, titanium)
yes, can be used alone      
Visit GoWelding.org for more detailed instruction and information on MIG welding.



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