Transfer Metal Wire Mig Welder
The metal wire, fusing, he moved to the weld pool with just three ways: Short-circuit transfer, Transfer to drops, Spray transfer. In the first case the current in the wire is not sufficiently high to lead to the melting temperature, so the wire comes into contact with the bath, causing a short circuit between the two metals, which would increase the current, it fuses the ends of wire, ie the metal is transferred across the arc.
Typically how often they occur, the short circuit is maintained between 20 and 200 per second. In this way you generate a series of small “puddles” that solidify quickly, given the relatively low temperature. So this mode of transfer is particularly suitable for soldering small thickness, welding position (vertical or sopratesta) or to close openings formed in response to treatment or repairs. Generally, avoid using this form of transfer, since it causes very high levels of spatter.
In the second case, the wire melts into drops with a diameter greater than the electrode, which are transferred into the bathroom essentially due to the force of gravity, so this transfer method may be used only in flat position. With this transfer method, you must have an arc long enough to allow the drops to fall in the bathroom without causing short circuits, which, to disintegrate, would cause the metal adjacent sprays.
In the latter case, the wire melts, forming a large number of small drops, streams are higher than those required for the transfer to droplets. In this way you get a transfer over a very stable, virtually no spatter. The current above which does this kind of transfer is indicated as the current transition to spray on this current transfer rate is changed from a few drops per second at 200-300 drops per second.
Since the size of the drops are much smaller than those generated in the transfer drops, the force of gravity is lower than the electrical forces resulting from the arch, so this mode can be used (with difficulty) in positions other than horizontal. This mode of transfer, requiring high currents, and therefore a high heat input, it is not recommended when children are welded thickness.
To overcome the difficulties linked to the high heat input that characterizes the spray transfer welding machines for MIG / MAG have been modified to work with the current pulse. In practice, the machine generates a certain percentage (usually 70% but may be increased or decreased depending on the circumstances) for the period (determined on the machine) a current below the current transition to spray.
At this stage the wire gets hot, but does not produce droplets that are transmitted, while the arc is maintained that heats the weld pool. After the break, the current is raised (usually a step) to a value greater than the current transition, so for some time (few ms) transfers the wire into the bath-mode spray. In most modern welding machines you can change the waveform (for example, managing the reduction of current after the transfer spraying). This way of using the machine to pay has significantly reduced the difficulty to weld with this technology, and low cost of electronics has allowed to contain within acceptable limits the cost of the machines themselves.
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