Basic knowledge

MIG welding and MAG welding explained in simple terms

| Editor: Theresa Knell

Arc Tig: The mechanized TIG solution from Fronius enables high-quality results at high welding speeds.
Arc Tig: The mechanized TIG solution from Fronius enables high-quality results at high welding speeds. (Source: Fronius)

Puts together what belongs together: welding. A combination of heat, pressure and filler materials permanently connects two workpieces.

Welding involves various processes which differ in their special properties. An important welding process is the so-called metal inert gas welding. It differs further in additional types, which we would like to explain to you in this article. In addition, you will learn everything about the so-called electric arcs, which are essential for welding.

Definition: Metal inert gas welding (MIG welding)

This electric-arc welding process, which is often referred to simply as arc welding, is elementary for metal processing because it allows almost all materials suitable for welding to be joined together in different material thicknesses. Welding can be carried out either manually, i.e. by hand, or automatically, i.e. with the help of welding robots, using the appropriate tools.

Inert-gas shielded welding: How does it work?

Arc Tig: The mechanized TIG solution from Fronius enables high-quality results at high welding speeds.
Arc Tig: The mechanized TIG solution from Fronius enables high-quality results at high welding speeds. (Source: Fronius)

The procedure can be roughly explained as follows: A wire electrode, which is located under a shielding gas cover, melts during the welding process due to strong heat. The molten metal solidifies again when cooled and thus reliably connects the metal parts. A gas, for example carbon dioxide (CO2), protects the welding point from the ambient atmosphere such as the room air. This is because it contains gases such as oxygen (O2), water vapor (H2O) and impurities (dust, etcetera) can influence the reaction, which is to be avoided.

Metal inert gas welding is divided into MIG welding (use of inert gases) and MAG welding (use of active gases) according to the gas used and the metal to be welded.

Procedures: MAG welding and MIG welding in detail

Metal inert gas welding (MIG welding)

In this process, so-called inert gases are used. These are, for example, nitrogen (N) or noble gases such as helium (He), neon (Ne) and argon (Ar). The selection of the gas is usually based on the costs: Some gases are cheaper than others. They are called "inert" because their special chemical structure prevents them from reacting with other compounds or elements under the present conditions. Therefore, they are very important for the welding process. The metals that can be joined by MIG welding are, for example, precious metals or aluminum.

Metal active gas welding (MAG welding)

View into a Tru Laser Weld 5000 from Trumpf for automated welding.
View into a Tru Laser Weld 5000 from Trumpf for automated welding. (Source: Trumpf)

This process is characterized by the fact that so-called active gases are used during welding. These gases include, for example, carbon dioxide (CO2) or a mixture of carbon dioxide with an inert gas such as argon. In contrast to the inert gas, an active gas participates in the reaction: Among other things, it has a stabilizing effect on the so-called electric arc. The metal that can be joined in MAG welding is alloyed and unalloyed steel.

Overview: Major differences between MIG and MAG welding

MIG welding:

  • Gas used: Inert gas, for example argon (cheap) or helium (expensive)
  • The gas reacts with the weld metal: no
  • Used for the following metals: Precious metals such as stainless steel, aluminum, titanium or copper

MAG welding:

  • Gas used: Active gas such as CO2 or a mixture of active gas and inert gas such as CO2 and argon
  • The gas reacts with the weld metal: Yes
  • Used for the following metals: alloyed and unalloyed steel

When to use which procedure?

When choosing between MAG and MIG welding, welders primarily opt for a process based on the metals to be welded.

The DVS - German Association for Welding and Allied Processes is a technical-scientific professional association which is active in all areas of joining technology.

New key technology has many advantages - Lorch makes the Cobot the new welder in the team. With the Cobot Welding Package, welding processes can be automated quickly and effectively.
New key technology has many advantages - Lorch makes the Cobot the new welder in the team. With the Cobot Welding Package, welding processes can be automated quickly and effectively. (Source: Lorch)

Electric arcs in welding and their properties

No arc, no welding. This arc is "a self-sustaining gas discharge", which is noticeable by a bright glow and which supplies the heat for the welding process. It burns between the wire electrode and the workpiece.

Welding will be the focus of the two trade fairs Schweißtec in Stuttgart and the Schneiden & Schweißen in Essen.

Arc welding can be divided into different types, such as short arc, transition arc, spray arc and impulse arc.

The short arc

The short arc produces only a small amount of heat during welding. This also only leads to a low deposition rate, but this is the best choice for many applications. It is used, for example, for thin sheet metal up to a thickness of 3 mm. With regard to the welding position, it is recommended for so-called forced positions, i.e. the melting metal should not flow downwards with gravity. This position is therefore not optimal, but the short arc offers a good solution.

The short arc is also used for root welding. It is also a technique for inert gas-shielded welding, in which only the underside of a weld seam is welded. Spatter formation during this welding is low, the material transition is characterized by coarse droplets. The arc is ignited by a deliberately generated short circuit.

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The transition arc

This arc offers an average heat output during welding, thus providing more energy for arc welding. Due to the higher energy output, welders can also weld thicker plates of medium thickness. As with the short arc, the transition arc is used for constrained positions. This type can also be ignited by means of a short circuit, but there are also other possibilities for ignition. A disadvantage of the process is the comparatively strong spatter formation. The other arcs presented here perform much better during welding.

The Mega Arc 2 series with Focus Arc and SDI-Plus for MAG welding from Rehm. Focus Arc shortens and focuses the arc.
The Mega Arc 2 series with Focus Arc and SDI-Plus for MAG welding from Rehm. Focus Arc shortens and focuses the arc. (Source: Rehm)

The spray arc

The spray arc is characterized by the highest deposition rate during MIG welding and MAG welding. This means that not only sheets of medium-thickness can be welded, but also thicker ones. The spray arc is used for shielded arc welding for the so-called filler and cover layers. Remember The short arc is used for root welding. The filler and cover layers represent the layers built up on them during welding. The spray arc can be ignited completely without a short circuit and offers the welder a very fine droplet material transition. As with the short arc, the spatter formation is low.

Welding technology: High Pulse 452 DW from Merkle with wire feeder in the shipyard version for the Meyer shipyard.
Welding technology: High Pulse 452 DW from Merkle with wire feeder in the shipyard version for the Meyer shipyard. (Source: Merkle)

The impulse arc

The impulse arc offers a low heat input. However, it is even higher than with the short arc. This allows the arc to be used in a wide range of applications. The thickness of the sheets to be welded can range from thin to thick. In addition, the impulse arc, like other arcs, is also suitable for constrained positions. A further advantage of the process is the very low spatter formation: It is lower than all other arcs. The impulse arc is also ignited without a short circuit.

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This article was first published by belchnet.

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