Welding Gases

Basics

• Most modern forms of welding use some form of Shield Gas to protect the Weld Pool from the atmosphere
• In the simplest form this is a pure Inert Gas
• In some instances, various aspects of the weldment can be modified via using a gas mixture, often with a Reactive Gas
  • In the older terminology (Pre-GMAW ), there was Metal Inert Gas (MIG) and Metal Active Gas (MAG)

How They are Utilized

• Shield Gas on the Weld Torch / Welding Gun
• Purge Gas (Welding) ( ~pg 628 of Modern Welding )and Secondary Shielding (Welding) and Backing Shielding / Backing Gas ( ~pg 595 of Modern Welding ) (only really needed for Titanium Welding and other odd metals/alloys
• Can also be used in essentially a Glove Box but for welding ~pg 282 and 596 in Modern Welding (Called it a Controlled Atmosphere Chamber ?)
• This page will not cover gasses used for Weld Heat Treatment which are typically just the same as one would use for an Oxy-Fuel Torch / Air-Fuel Torch

List

Pure Gases

Argon

• Used in all GTAW (short of potentially in conjunction with gases such as Helium) and nearly all non-ferrous GMAW welds,

CO2

• Used for carbon, and some low allow steels

Helium

• Conducts heat Better than
• Thus used for a "Hotter Arc"
• Sometimes used with thick non-ferrous metals, and highly heat conductive metals like aluminum and copper which rapidly carry heat away from the Weld Pool and thus require more heat to achieve a good weld
• However it floats away from the weld pool, and thus requires more gas usage
• Also very' expensive, and comparatively scarce (See Peak Helium / World Helium Reserves / Helium Production )

Nitrogen

• Can this be done?
• Nitrogen as Shield Gas

Gas Mixes

Argon-Carbon Dioxide

• Often referred to as "75-25' since it is 75% argon and 25% carbon dioxide
• Cheaper than pure argon, and allows f

References

• Modern Welding Pages:
  • ~176 for GMAW Gases
  • ~246 for GTAW Gases
  • Grab specific quotes maube even, as of now it's just paraphrasing
    • The book doesn't really mention why gas mixtures do what they do, so some papers may be of use for that aspect

External Links

• A TWI Page Titled "What is the Difference Between MIG and MAG"
• An Article by "Welding Pros" Titled "Different Types Of Welding Gases"