6 Flux Core MIG Welding Tips

MIG welding with fluxed core wire is significantly easier to set up than MIG welding with shielding gas. When you enter shielding gas into the mix, you have to make sure you have enough gas flowing into the weld joint in order to shield the metal from impurities. That’s an extra cost for the gas, and not to mention that you’ll have another setting to keep track of while you work.


Flux core MIG welding is also more versatile and portable. If you need to MIG weld outside or you can’t control the environment where you’re working, you’ll do well to keep some flux core MIG wire around for the odd project. However, if you want to use flux core wire for your next MIG project, you need to keep a few things in mind:

Prepare to Clean Your Welds

Flux core MIG wires protect the weld while you burn the electrode down. That saves you from setting up the gas rig before you strike your arc. However, you’ll need to spend more time cleaning off the metal when you’re done welding if you want the weld to look its best. Set aside enough time for clean up when you get to work with a flux core MIG wire. If you need a clean weld, consider a solid core wire and a shielding gas set up that will minimize impurities in the weld puddle.

Flux Core Wire Offers Advantages

Besides the simplicity of MIG welding with flux core wire, it also offers a number of advantages if you’re pushing your welder to the height of its power limit. A flux core wire will give you more penetration into the weld joint if your metal is thick or your welder simply can’t crank out enough amperage for a particular project.

The safety and longevity of your weld depends on getting solid penetration and fusion with the metal work piece, and a flux core wire can offer a slight edge sometimes.

Use DCEN, Electrode Negative with Flux Core Wire

Each package of flux core wire will have specifications about how to use it best, but one common setting change is that flux core MIG welding must be done with DCEN, or electrode negative. While you certainly can still weld on the electrode positive setting, you’ll get a cleaner weld if you’re set at electrode negative.

Every welding machine will be different, but look into how you can swap terminals so that the negative terminal runs to the electrode on your MIG gun. Running on a positive current could result in a lot of spatter that you’ll need to clean up. If you’re in a rush and appearance doesn’t matter, that may not be a big deal, but keep that in mind before striking your arc!

When You Need More Penetration, Weld Vertical Uphill

Flux Core MIG wire is ideal for those situations when you need to get slightly better penetration into thick metal that your welder can’t quite handle with solid core metal. One trick that welders use to get extra penetration with a fluxed core MIG wire is to weld vertically using an uphill motion. By working your way back and forth up a weld joint you’ll get a stronger weld than you would by welding horizontally.

Pre-heat or Weld Both Sides for a Stronger Weld

The more heat you get into the weld joint, the more you can penetrate the metal. If you’re working with flux core wire on a metal work piece that is a bit too large for your MIG welder, consider pre-heating the metal before you get to work. Don’t overheat it, or you could burn through!

When There’s Slag, Drag

Welders often recommend dragging or pulling when working with flux core MIG wire since it often creates more spatter. The motion of the arc being dragged will keep the spatter out of the weld joint, giving you a cleaner, stronger weld.

If you push the MIG gun into the weld joint, you’ll potentially push slag into the weld puddle and make your weld dirty. By pulling your torch across the weld joint the spatter should land on the already completed weld, minimizing any porosity.

Learn More about MIG Welding

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