Gas flowed around the arc to keep oxygen and nitrogen out of the weld pool. GTAW uses pure argon, helium or blends; GMAW on steel commonly uses 75 percent argon and 25 percent CO2 (C25), straight CO2, or argon-rich blends for spray. Flows of about 15 to 35 cubic feet per hour are typical; too little or a draft causes porosity, and too much creates turbulence that pulls air in.
Flowmeter says 30 but you've got a fan blowing on the joint, your shielding gas is gone, put up a screen.
Also heard as
- shield gas
- cover gas
- C25
- 75/25
Related terms
GMAW
Gas metal arc welding: a continuously fed wire electrode shielded by gas, known in the shop as MIG.
GTAW
Gas tungsten arc welding: an arc from a non-consumable tungsten electrode under inert gas, known as TIG.
Bottle
Shop word for a high-pressure gas cylinder of shielding gas, oxygen or fuel gas.
Porosity
Gas bubbles trapped in weld metal as it freezes, showing as round holes on the surface or on film.
Purge
Inert gas flowed inside a pipe or behind a joint to keep the back of the weld from oxidizing.