Gas Metal Arc Welding (GMAW), commonly known as MIG (Metal Inert Gas) or MAG (Metal Active Gas) welding, is one of the most widely used arc welding processes in modern manufacturing and fabrication industries . It is often referred to in Chinese industry as “Er Bao Han” , which specifically denotes CO₂ shielded arc welding.

What is GMAW?

GMAW is a welding process that joins metals by heating them to their melting point using an electric arc established between a continuous, consumable bare wire electrode and the workpiece . The arc and the molten weld pool are protected from atmospheric contamination by an externally supplied shielding gas .

Basic Working Principle

In the GMAW process, the following sequence occurs:

1. Continuous wire feeding – The consumable electrode wire is automatically fed from a spool through a welding gun at a preset speed .
2. Arc establishment – An electric arc is struck between the wire electrode and the workpiece, generating intense heat that melts both the wire and the base metal .
3. Shielding – A shielding gas (such as CO₂, argon, or gas mixtures) flows through the gun nozzle, protecting the molten weld pool from oxygen, nitrogen, and moisture in the air .
4. Weld formation – The molten metal from the electrode is transferred across the arc and deposited into the weld pool, which solidifies to form a strong joint .

Key Characteristics

Advantages

• High productivity – GMAW offers much higher deposition rates compared to processes like SMAW (stick welding) or GTAW (TIG welding) .
• Less welder skill required – The continuous wire feed and self-regulating arc make it easier to learn and operate, especially in semi-automatic mode .
• All-position welding capability – With appropriate parameter selection, GMAW can be performed in flat, horizontal, vertical, and overhead positions .
• Clean process – Since no flux is used, there is no slag to chip away between passes, making it ideal for multi-pass welding