How to Set the Gas on an MIG Welder

by C.L. Rease
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Tara Novak/Demand Media

Ensuring the proper gas flow rate is essential to the quality of the weld. Shielding gas protects the molten weld puddle from the gases in the atmosphere that cause pinhole imperfections, or porosity, in the weld. The standard shielding gas for carbon steel contains 75 percent argon and 25 percent carbon dioxide. There are other MIG welding shielding gases used on stainless steel and aluminum; however, setting the gas flow remains the same for all shielding gases.

Step 1

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Secure the bottle of shielding gas to the MIG welder by setting the bottle in the holder, and hooking the chain around the bottle.

Step 2

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Inspect the hoses attached to the gas regulator for signs of damage. If you find damage, exchange the regulator assembly for one that is undamaged.

Step 3

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Quickly open and close the valve handle located on the top of the shielding gas bottle to clear debris and contaminants from the bottle valve.

Step 4

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Insert the nipple of the gas regulator into the threaded valve area of the gas bottle. Turn the locking nut clockwise until hand-tight. Adjust the adjustable wrench to fit the locking nut.

Step 5

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Tighten the locking nut with the adjustable wrench and turn on the gas valve that you cracked in Step 3.

Step 6

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Feel around the gas regulator, hoses and connections for gas leaks. Although the shielding gas is inert, leakage results in gas loss and in a confined area can result in asphyxiation.

Step 7

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Turn on the MIG welder.

Step 8

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Press the trigger on the MIG gun to activate the gas valve. Read the PSI on the left regulator gauge; it should read between 25 and 30 cubic foot-hours.

Step 9

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Turn the handle located below the left regulator gauge, while depressing the MIG gun trigger until the pressure reads between 25 and 30 cubic foot-hours.

Step 10

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Trim the excess wire that extended from the MIG gun tip while you were adjusting the gas pressure.

Step 11

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Adjust the gas pressure as needed if the conditions change. A higher gas pressure is required when there is wind or a breeze from a fan. Take caution: Gas pressure that is set too high will result in turbulence around the weld puddle. This will result in porosity, which will compromise the strength of the weld.

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