GMAW:Gas Metal Arc Welding

GMAW welding

“GMAW” Gas metal arc welding process is an Arc welding process in which fusion is produced by heating the work along with an electric arc between the continuous filler metal electrode and the weld pool.

Power source used in GMAW welding

“Gas Metal Arc Welding “employs a constant voltage (CV) power supply, and uses either short-circuiting Spray method for transferring work from globular, or electrode to metal and can be operated in semi-automatic or automatic mode also.

Since shielding gas is used in this process, no flux is required. Shielding gas is used to avoid atmospheric contamination from the molten weld pool.

A constant voltage, direct current power source is most commonly used with GMAW, but constant current systems, as well as alternating current, can be used.


Shielding Gases

The argon, helium, or their mixtures may be used as shielding gas whereas, in the co2 welding method, Carbon dioxide is used as the shielding gas, the basic details are as follows:

MaterialsShielding gas
Al, Mg, Cu, Ni, TiArgon
Al, Mg, CuHelium
Mild steelCarbon-dioxide(CO2)
Al, Low alloy, Carbon steel, Stainless steelArgon+(1 to5%)Oxygen
Al, Cu, Ni, and alloysArgon+Helium
The function of Shielding gassesThe helium and CO2 help to increase the penetration, whereas the argon gas reduces spatter loss.

Welding Operation

Before start

Before breaking the arc, the gas and water flow is inspected by the operator. Current and wire feed speeds are determined, and electrical connections are checked. The arc can be struck in two ways.

First method

The first method involves switching on the current and shielding gas flow and as a common practice to grab the arc the electrode is scratched against the job.

Second method

In the second method, the electrode is to be in contact, which is withdrawn and then swept to advance the welding, but before the arc is broken, the gas, water, and current are turned on.

The electrode length is estimated to be approximately 15 mm from the torch before the arc strike.

During welding, the torch is about 10-12 mm away from the work and the arc length should be kept between 1.5 to 4 mm. Arc length is needed to keep constant using the principles.

Self-adjusting arc, and self-controlled arc, respectively, in semi-automatic (manually operated) and automatic welding sets.