Role of inductance in short circuit cycle in GMAW welding

Inductance controls the rise in amperage (current) between the time the electrode contacts the base metal and then pinches off. The higher the inductance is set, the longer the arcing period. Both short-circuit cycles shown in figure shows the same amount of time. As the inductance increases, the rise in amperage is hindered, thus increasing the amount of time the electrode wire is in contact with the base metal while decreasing the amount of time the open arc occurs, which increases the puddle fluidity. Provided the voltage and amperage are set correctly and if the inductance is set correctly, the puddle will be fluid with little spatter. Voltage and amperage (wire feed speed) are the primary parameters to set. Inductance can be thought of as the final stage to fine-tune the arc. If the inductance is set too high, the rise of amperage is hindered, and the electrode will have poor arc starting stability. The electrode wire will stumble, and the operator will feel the welding gun push back. If the inductance is set too low, the rise of amperage is not hindered, and the short-circuit cycle is fast and violent, producing a great deal of spatter. In worse cases, the short circuit is so violent that the electrode wire snaps back and fuses to the contact tip.

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Today’s modern power sources have a usable range of inductance and have eliminated the problem areas at the extreme high and low ends. For carbon steels, 30% inductance is sufficient to reduce spatter and provide good wetting at the weld edges. Inductance settings for stainless steels are set significantly higher in order to reduce spatter, and a 50% setting is desired. The higher inductance tends to ball the end of the electrode, which must be cut before restarting the arc.

Keep reading, happy welding

Thank you,

KP Bhatt

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