The rate at which gas is caused to flow for oxyfuel cutting or welding, or to provide shielding during arc welding by any of several processes, including gas metal arc welding (GMAW), gas tungsten arc welding (GTAW), flux cored arc welding (FCAW), or electro-gas welding (EGW).
The flow rate is controlled by flow meters that are calibrated either in liters per minute or cubic feet per hour.
The flow rate of shielding gases for GMAW (Mig) should be sufficient to exclude air from the weld location; the flow of gas should maintain adequate and effective coverage of the weld arc. This is influenced by a number of variables:
(1) the shielding gas used,
(3) distance of gas nozzle orifice from the work surface,
(4) size of the gas nozzle,
(5) shape of the gas nozzle,
(6) the presence of drafts or air currents,
(7) inclination of the torch,
(8) arc length,
(9) welding speed,
(10) size of the weld puddle,
(11) position of the workpiece, and
(12) metal or alloy being welded.
A flow rate of 3 Lpm (6 cu ft/hr) for helium and 2 Lpm (4 cu fm) for argon generally provides effective shielding in still atmospheres. While these rates are only about one-third the rates normally used for average welding conditions, they indicate that cost control is possible when all other factors are under control.
Excessive gas flow is not only wasteful, but can also be detrimental to the weld metal and the welding operation. Excessive flow may also cause an unstable arc at low welding currents and result in undercutting the work surface by the weld bead.