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
• An article in "Weld Gears" Titled "Can Nitrogen Be Used for MIG Welding"

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

Production

• Mainly Two Methods:
  • Pressure Swing Adsorption (For Nitrogen Mainly, although further processing of the non-nitrogen stream may be worth a look?)
  • Liquid Air Distillation (Can produce anything, even down to Xenon (with huge systems that have enough mass flow to gain a useful volume!), at OSE's scale it will most likely produce Nitrogen, Oxygen, and Argon (which could all be Cryogenic Liquids as well since they will already be in that temperature range, unlike PSA workflows where it would require another processing step)
• Need to see how High Purity Carbon Dioxide is made
  • May essentially be similar to CCS type systems ( Amine Scrubbing ) but with simple burners instead of engines/gas turbines?

References

• Modern Welding Pages:
  • ~176 for GMAW Gases
  • ~246 for GTAW Gases
  • Grab specific quotes maybe 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"
• A Page by "Weld Guru" Titled "Welding Gases: Different Types & Their Uses"
• A Paper Discussing Pressure's Effect on Welding (If i understand the title correctly) ]