The article and images on short circuit metal transfer were created by Steve Bliele and he gave us exclusive rights to use it on our website...
Short Circuit is considered to happen at voltage settings under 22 volts and is the most common type of metal transfer for general purpose GMAW (MIG) wire feed welding. The welding wire continually touches the base metal and arcs in an "arc on/ arc off" cycle that allows the molten weld puddle to cool enough so that welds can be made in any position, flat, horizontal, vertical, and overhead.
When the wire feed gun trigger is pulled, shielding gas begins to flow, the welding wire is energized, and the drive rolls feed wire:
As the wire touches the metal, electrical resistance causes the welding wire to heat up until it pinches off, creating an arc:
Electrically energized gasses surrounding the arc form a molten weld pool, fusing the filler metal and base metal:
The continuously fed wire overcomes the heat of the arc touching the metal again until it heats up, pinches off, and arcs:
This Short Circuit "arc on arc off" cycle happens 50 to 250 times a second depending on voltage and wire speed settings:
The welding machine should be set up to produce the maximum number of Short Circuit cycles. This can be achieved by adjusting either the voltage or the wire-speed to produce the smoothest sounding arc.
While the "arc on arc off" cycle does allow
the puddle to cool enough for all position welding, there is potential
for lack of weld fusion. Welding machine settings, metal preparation,
good welder technique are important in constantly making good welds.
The recommended Wire Extension (from the contact tip to the base metal) is 1/4" to 3/8". Pulling the gun away increases the wire extension and causes the wire to pre heat, reducing the amperage necessary to burn off the wire and reducing the energy (heat) at the weld. Holding the gun closer increases the amperage and heat at the weld:
GMAW (MIG) Short Circuit can either be "pushed" or "pulled". Pulling the weld, with the wire on the leading edge of the puddle, will produce better penetration and build up more weld. Pushing the weld, with a slightly faster travel speed, tends to flatten the weld and reduce penetration for welding thinner gauge metals:
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