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WIRE WELDING Maintaining the arc.

The basic principle of all arc welding is that an electric arc melts the surface of the work piece (joint), and whatever filler material introduced into the melt pool. In processes where the arc is established between a filler material which is continuously fed into the arc, and the work piece, the arc length and thereby the arc voltage must be kept at a constant value to obtain a uniform weld. This can be obtained in two ways: 1. By adjusting the filler material feed speed to exactly the same speed as it melts.

2. By adjusting the amperage to exactly the value needed to melt the quantity of filler material. When welding with coated electrodes (SMAW) the welder's task is to feed the electrode according to alternative 1, while the power source provides constant current.

used, it will supply relatively constant current regardless of arc length. Alternative 2 above is therefore not applicable. A wire feeder, which automatically adjusts the filler material feed speed (alternative 1 above) is therefore required.

The combination of such a wire feeder and a constant current power source is a fully acceptable solution when welding in the spray-arc area, and especially when flux cored wires are used. It is not, however, possible to use such a combination if welding in the short-arc area is required, as the mechanical adjustment of feed speed will be to slow to maintain a proper short-arc.

Constant voltage power source.

To maintain a proper short-arc requires the combination of a constant voltage power source and a constant speed wire feeder. The constant In GMAW welding both parameters voltage characteristic of the power are guided by the equipment, thereby source will automatically maintain the demanding less from the welder's skill arc length by adjusting the amperage but more from the equipment. according to need, once the arc voltage and thereby the arc length has been selected. The constant voltage Constant current power source characteristic is also suitable for If a traditional power source with spray-arc welding, but cannot be used constant current characteristic is for any other arc welding processes.

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