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Step 1
Select the thinnest wire that is practical. Thinner wire heats the metal less and gives you better control over the weld bead. The deposition rate is also lower, which makes it easier to recover from mistakes. Sheet metal that is less than .04 inches thick should use wire that is .023 inches in diameter. Thicker sheet metal may be welded with .030 inch wire.
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Step 2
Use a high argon shielding gas which will produce less spatter. Argon carries less heat than carbon dioxide and a common mixture for sheet metal is 75 percent argon and 25 percent carbon dioxide.
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Step 3
Keep the arc in the middle of the weld puddle to allow the puddle to protect the base metal from the full force of the arc. This technique is contrary to the normal method of MIG welding, where the arc should remain on the leading edge to achieve greater penetration.
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Step 4
Weld in a straight line with the fastest possible speed that maintains a good bead profile. Sheet metal should not be welded by whipping or weaving the torch, as this will increase the heat of the metal and therefore increase the chances of burn-through and warping.
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Step 5
Keep the heat evenly distributed by skip welding. Make a 1 inch weld and skip 5 inches until you have a series of 1 inch welds along the entire length to be welded. Go back and make a second series of welds next to the first series. Repeat this cycle a total of 6 times until the entire length has a continuous weld.
