CO2 (MAG) welding: a fast process for structures, gates and fences

What CO2 welding is

When people say CO2 welding they usually mean MAG welding (Metal Active Gas). A wire, which is both the electrode and the filler, is fed automatically from a spool through a torch, and the electric arc melts it and joins the parts. The weld is shielded by gas from the same torch: pure carbon dioxide or a mixture of argon and CO2. The mixture gives a calmer arc and less spatter, while pure CO2 is cheaper and penetrates deeper.

Where it is used

Because of its speed and good penetration, CO2 welding is the standard for load-bearing and semi-load-bearing structures in ordinary steel: gates, fences, canopies, staircases, halls and industrial doors. The wire is fed automatically, so welds are run faster than with TIG or stick welding.

Advantages

• High working speed and economy on longer welds
• Good penetration and strong welds in thicker steel
• Suitable for the workshop and for work on site, with protection from wind

Limits

• Metal spatter, which must be cleaned and ground off afterwards
• The weld is coarser than with TIG, so TIG is more often chosen for visible joints
• Wind blows the shielding gas away, so the work area must be sheltered outdoors

What makes a good weld

Quality does not depend on the machine alone. The joint must be free of rust, paint and grease, and the parts correctly fitted and tack-welded. The welding sequence is chosen so that heat does not distort the structure, because long fences and frames deform easily. Current, voltage, wire speed and gas flow are set according to the thickness of the material.

CO2 and TIG: a short comparison

After welding

The weld is cleaned of spatter and slag, ground where needed, and the surface is then prepared for corrosion protection. You can read more in the article on protecting metal after fabrication.

Related services

• Metalwork
• Industry