Q: Does shielding gas affect the quality of the finished weld?

A: For most mild steel applications, CO2 will provide adequate shielding, but when you must have a flatter bead profile, less spatter or better wetting action, you may want to consider adding 75 to 90% argon to your CO2 shielding gas mix.

Why? Argon is essentially inert to the molten weld metal and therefore will not react with the molten weld metal. When CO2 is mixed with Argon, the reactivity of the gas is reduced and the arc becomes more stable. But, Argon is more expensive. In production welding, selecting the perfect shielding gas can be a science of its own. Attributes such as material thickness, welding position, electrode diameter, surface condition, welding procedures and others can affect results.

Common gas mixes for the home hobbyist and small fabricator would be: [ul][*]100% CO2 -Lowest price, generally greatest penetration, and higher levels of spatter. Limited to short circuit and globular transfer.[*]75% Argon - 25% CO2 -Higher price, most commonly used by home hobbyist and light fabricator, lower levels of spatter and flatter weld bead than 100% CO2. Limited to short circuit and globular transfer.[*]85% Argon - 15% CO2-Higher price, most commonly used by fabricators, with a good combination of lower spatter levels and excellent penetration for heavier plate applications and with steels that have more mill scale. Can be used in short circuit, globular, pulse and spray transfer.[*]90% Argon - 10% CO2- Higher price, most commonly used by fabricators, with a good combination of lower spatter levels and good penetration for a wide variety of steel plate applications. Can be used in short circuit, globular, pulse and spray transfer.[/ul]
TRY C-25 SHIELDING GAS (75% Argon, 25% CO2 )

Q: Are there any other tips you can provide for higher quality MIG welding?

A: Try a smaller diameter wire. Although the most common diameters of welding wire are .035” and .045”, a smaller diameter wire usually will make it easier to create a good weld. Try an .025” wire diameter, which is especially useful on thin materials of 1/8” or less. The reason? Most welders tend to make a weld that is too big - leading to potential burn through problems. A smaller diameter wire welds more stable at a lower current which gives less arc force and less tendency to burn through. If you keep your weld current lower, you will have a greater chance of success on thinner materials. This is a good recommendation for thinner materials; but be careful using this approach on thicker materials (>3/16”) because there may be a risk of lack of fusion. Whenever a change like this is made, always verify the quality of the weld meets its intended application.