How to Set the Gas on an MIG Welder

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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.

How to Set the Gas on an MIG Welder
(Tara Novak/Demand Media)

Things You'll Need

  • 1 bottle of 75/25 gas
  • MIG welder
  • Gas regulator
  • Adjustable wrench
  • Wire cutters
Step 1

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

Tara Novak/Demand Media
Step 2

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.

Tara Novak/Demand Media
Step 3

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.

Tara Novak/Demand Media
Step 4

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.

Tara Novak/Demand Media
Step 5

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

Tara Novak/Demand Media
Step 6

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.

Tara Novak/Demand Media
Step 7

Turn on the MIG welder.

Tara Novak/Demand Media
Step 8

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.

Tara Novak/Demand Media
Step 9

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.

Tara Novak/Demand Media
Step 10

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

Tara Novak/Demand Media
Step 11

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.

Tara Novak/Demand Media

References

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