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Different types of welding

Gas-shielded metal arc welding (MIG / MAG)

MIG / MAG welding is one of the more recent arc welding processes. It comes from the USA, where it was first used in 1948. A short time later it came to Europe. At first it was only used with inert gases or with argon, which only contained small amounts of active components (e.g. oxygen), and was therefore called SIGMA welding for short. This is the abbreviation for “shielded inert gas metal arc”. From 1953, the Soviet Union then used an active gas for welding, namely carbon dioxide (CO2). This was only possible because wire electrodes have also been developed in the meantime, which took into account the higher burn-off of alloying elements in active gas welding.

MIG / MAG (metal inert gas; inert gases) / (metal active gas; active gases) is also an arc welding process in which the melting welding wire is continuously tracked by a motor at a variable speed. At the same time, the welding point is filled with carbon dioxide or a noble gas via a nozzle (this gas protects the liquid metal under the arc from oxidation, which would weaken the weld seam2) on the one hand ensures better heat dissipation, on the other hand it causes a slight enrichment of the weld metal with carbon. ' MIG means metal inert gas welding. In this case, no active gas, but only an inert gas (usually argon, but also helium) is supplied to keep atmospheric oxygen away from the weld seam. These shielding gases are required to weld high-alloy steels, non-ferrous metals and aluminum alloys.

In metal active gas welding (MAG) either pure CO2 or a mixed gas of CO2, argon and O2 is used in order to influence the welded joint according to the special technological requirements. The MAG welding process is used for unalloyed and higher alloyed steels. In addition, the melting cladding forms slag. This is lighter than liquid steel and is washed onto the weld seam. This results in slow cooling and thus lower shrinkage stresses.

Tungsten inert gas welding (TIG)

Tungsten inert gas welding (TIG welding process) originated in the USA and was known there in 1936 under the name Argonarc welding. It was only introduced in Germany after World War II. In English-speaking countries the process is called TIG after the English "Tungsten" for tungsten. The TIG welding system consists of a power source, which in most cases can be switched to direct or alternating current welding, and a welding torch, which is connected to the power source by a hose package. The hose package contains the welding current line, the shielding gas supply, the control line and, in the case of larger torches, the supply and return of the cooling water.

There are two ways to ignite the arc, contact and high frequency ignition. With contact ignition (stroke or scribed ignition), similar to electrode welding, the tungsten electrode is briefly touched on the workpiece, thus creating a short circuit. After the electrode is lifted off the workpiece, the arc burns between the tungsten electrode and the workpiece. A major disadvantage of this process is that some material from the workpiece gets stuck to the tungsten electrode each time it is ignited. Due to the high temperatures at the tip of the electrode, a “tungsten-workpiece alloy” is formed which is liquid at these temperatures, causing the needle-sharp tip to melt. As a result, fine weld seams are difficult to carry out with this method.

With high-frequency ignition, the gas between the electrode and the workpiece is ionized with the aid of a high-frequency igniter, which applies an extremely high voltage to the tungsten electrode, thereby igniting the arc. The high-frequency detonator has a safe current.

Manual arc welding

Electrode hand welding, or MMA welding for short, is one of the oldest welding processes that is still used today. It goes back to the experiments of Slawjanow, who in 1891 was the first to use a metal rod instead of the carbon electrodes that had been used for arc welding until then, which was both an arc carrier and a welding filler. The first stick electrodes were not covered and therefore difficult to weld because the weld was unprotected from oxidation with the air. Later, the electrodes were covered with materials that made welding easier, protected the weld metal and had a metallurgical effect on the process. The first patent for a covered stick electrode dates back to 1908.

In this welding process, an electric arc that burns between an electrode and the workpiece is used as a heat source for welding. Due to the high temperature of the arc, the material is melted at the welding point. At the same time, the stick electrode melts as a filler material and forms a weld bead