Electric arc welding processes with gas shielding are widely used in the metal fabrication of welded structures. In MIG MAG welding, the arc is formed with metal transfer. Unlike TIG welding, there is a high concentration of metallic vapours that provide the majority of current-carrying particles in the MIG MAG process.

It is the nature of the shielding gas used that differentiates whether the process is MIG (Metal Inert Gas) or MAG (Metal Active Gas). Thus for MIG welding, only inert gases and inert mixtures are used because generally the nature of the metals to be welded in MIG does not tolerate the presence of active compounds (aluminium and alloys).

Choosing the right shielding gas according to the application for the MIG process avoids generating welding defects. Without appropriate gas shielding of the weld pool, various welding imperfections occur, such as porosity, surface oxidation… or a reduction in the mechanical properties of the molten metal, with significant consequences for the welded structure.

EURO-WELDING can advise you on the most suitable gases for MIG welding depending on your applications. We offer MIG gases in disposable or refillable cylinders according to your needs. Whether it is Argon, Helium, or other more specific mixtures… you can rely on the proven advice of our experts, available at any time to answer all your questions and additional information needs. Do not hesitate to contact us, the world of welding is our passion and offering the best welding equipment and products is our business!

In MIG welding, as in any shielded atmosphere welding process, the shielding gas protects the weld pool against the harmful effects of ambient air composed of oxygen, nitrogen and moisture. This may seem contradictory, as oxygen, hydrogen or nitrogen are in some cases intentionally added to the shielding gas in order to improve operational handling, the appearance of the weld or to achieve specific metallurgical characteristics. Nevertheless, these gas mixtures are only used if the additive gas does not cause negative metallurgical effects in the material.

In addition to its metallurgical role, the gas must also have the necessary properties to create optimal conditions for the electric arc, such as facilitating easy arc starting, being easily ionized to obtain a low-voltage arc, enabling arc root stability, contributing to heat transfer, influencing the behaviour of the weld pool (wettability, fluidity)… all while guaranteeing a quality profile for the weld bead.

The choice of gas or gas mixture thus becomes an important parameter, as its action influences the performance obtained depending on the process implemented. It is therefore necessary to take into account the metallurgical compatibility of a type of gas with the materials to be joined, the effect of a component on arc behaviour, the environmental impact on the welder, without neglecting the cost of the finished product.

The gases used in MIG welding are therefore inert gases, mono-atomic gases: argon, helium and mixtures; regardless of the content, there is no reaction with the molten metal. With an inert gas, there is virtually no reaction with the weld pool, unlike the use of an active gas which directly participates in the welding action. However, the particular feature of MIG welding is that the gas influences the favourable conditions for achieving a metal transfer regime in the arc, as well as the value of the working range.

In the MIG process, the inert gas serves to protect certain elements of the weld; the wire electrode, the arc, the weld pool and the elements surrounding the base material are shielded from atmospheric contamination.

Thus, argon (Ar) is the only inert gas that adapts to virtually all welding applications. Obtained by fractional distillation of the atmosphere, the substance offers easy arc starting and fairly good arc stability. Nevertheless, it is worth knowing that a mixture of argon and carbon dioxide, as well as pure oxygen or pure carbon dioxide, reacts with a liquid weld pool.

For its part, helium (He) is a fairly rare inert gas that comes from the subsoil. It offers the advantage of better penetration with less arc stability. It is more commonly used on materials with high thermal conductivity and on large thicknesses. Lighter than air, helium must also be used in large quantities for adequate shielding. Unlike argon, helium does not contribute to oxygen enrichment or to the quality of the chemical bond of the weld, but it does increase welding speed. Furthermore, helium guarantees much better sidewall penetration. It is for these reasons that helium or a helium/argon mixture is often used for MIG or TIG welding.

What fundamentally differentiates argon from helium is the thermal conductivity of the arc as well as the ionization potential. Thermal conductivity reflects the heat transfer that occurs from the center to the outside of the arc column, and consequently the central axis of the arc, which is the hottest part. Argon has low thermal conductivity and provides a high energy density in the inner zone of the arc. Helium produces a more conductive arc plasma and generates a more uniform heat distribution.

Furthermore, argon, being fairly heavy, can form a covering layer over the weld pool. Helium, on the other hand, being lighter, tends to rise in swirls around the nozzle. It is for this reason that the flow rate of helium must be higher than that of argon.

It is therefore important to clearly differentiate the behaviour of these inert gases in welding and to take into account their physical properties summarised in the table below.

On EURO-WELDING, you will find a range of gases and gas mixtures for MIG welding, gases with the best capabilities to ensure both arc stability, process performance, and the quality of the weld beads obtained, both in terms of their mechanical and metallurgical characteristics and the aesthetics of the welded joint.

For MIG welding of aluminium, we offer for example the Argon 4.5 MobilFlam from LINDE, in a refillable cylinder delivered full, available in 2 capacities: either a 1 m3 cylinder (height 64 cm) weighing 11 kg, or a 2.3 m3 cylinder (height 80 cm) weighing 19 kg. Suitable for all arc modes in MIG welding, the Argon 4.5 MobilFlam from LINDE allows you to obtain a stable arc and easy arc starting. Delivered full, the cylinder does not require a rental or maintenance contract. This product can be offered to you with an integrated flow meter on the cylinder.

Disposable cylinders of PURE Argon gas for MIG aluminium welding are also available in different capacities: 0.95 litre compressed (60 litres expanded), 2.2 litres compressed (240 litres expanded)… These disposable MIG gas cylinders are fitted with an M10 Valve thread.

In addition to MIG gas cylinders, we also offer all the accessories needed for gas cylinders. You will find, for example, mini dual-gauge regulators for refillable cylinders. The flow rate is adjustable from 0 to 30 litres/minute, and these regulators are tested up to 300 Bar. They are designed for use with neutral welding gases such as pure Argon or Argon + CO², and their connection thread is type C. Italian-made, these regulators are perfectly designed in accordance with the EN 585/ISO 2503 standard.