Welding is the connection of workpieces using heat and / or compression, so that the workpieces form a unit. When welding, the heat source is an arc flame that is generated by the electricity of the welding power supply. Arc-based welding is referred to as arc welding.
The joining of the workpieces can only be based on the heat generated by the arc, so that the workpieces fuse together. This method can be used for example in TIG welding (tungsten inert gas welding).
Usually, however, the workpieces are welded to one another with the aid of an additional material via the weld seam or weld point. For this purpose, a wire feed device is used via a welding torch (MIG / MAG welding) or a welding electrode by means of a manual feed. In these processes, the filler metal must have approximately the same melting point as the material to be welded.
Before welding, the edges of the workpieces are put together so that they form a suitable weld joint, e.g. a V-joint. In the course of the welding process, the arc welds the joint edges to one another via the filler material, which creates a liquid weld pool.
In order to obtain a permanent weld connection, the weld pool must be protected against oxygen enrichment (oxygenation) and influences from the ambient air, e.g. with the help of protective gas or slag. The shielding gas is led to the liquid weld pool via the welding torch. The welding electrode can also be coated with a material that represents a kind of protective bell and serves to ensure that slag forms over the weld pool.
The best known welding materials are metals such as Aluminum, steel and stainless steel. Plastics can also be welded. In plastic welding, the heat source is hot air or an electrical resistance.
How does the arc occur?
The arc required for welding is an electrical discharge between the welding electrode and the workpiece. The arc is generated when a sufficiently large voltage pulse (trigger ignition) develops between the workpieces or the welding electrode is tapped on the material to be welded (contact ignition).
The arc is the basis of arc welding. It welds the starting material and the filler material, producing the weld seam.
Here, the voltage discharges like a lightning strike, allowing electricity to flow through an air gap, resulting in the generation of an arc that is several thousand degrees Celsius at a maximum of 10,000 degrees Celsius (18,000 degrees Fahrenheit). A continuous current to the workpiece is generated by the welding electrode via the welding current supply and for this reason, the workpiece must be earthed in the welding machine via an earth cable before the welding process is started.
In TIG welding, the welding electrode is an unusable tungsten electrode and the filler metal is fed manually to the welding point. In MIG / MAG welding, the electrode is a welding wire that is passed through the welding torch. The wire melts and becomes a filler in the workpiece.
In order to obtain a smooth and permanent weld, the welding arc should be stable. It is therefore important to use a welding voltage and to select a wire feed speed that is suitable for the material to be welded and its thickness.
In addition, the welding technique affects the fineness of the arc and consequently the quality of the weld. The distance from the welding electrode to the seam and uniform speed of movement of the welding torch are important factors for successful welding. Estimating the correct voltage and wire feed speed is an important part of the skills of the welder.
However, modern welding machines offer several options that make the welder's work easier, such as the storage of previously used welding settings or the use of preset synergy curves, which makes it easier to set the welding parameters for the task ahead.
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