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Flux-Cored or Solid Wire MIG Welding: Determining the Best Fit for Your Application

Flux-Cored or Solid Wire MIG Welding: Determining the Best Fit for Your Application

Today’s guest post is by Ben Romenesko of Miller Electric.

I hear it often from the people purchasing their first MIG welder: “Do I really need to run gas with that?” The answer to that question really boils down to the application that the welder will be using the machine for.

For the purpose of this article, I will refer to flux-cored wire as self-shielded flux-cored wire. When I talk about solid wire, I’m referring to a short circuit transfer using a shielding gas like 75 percent argon/25 percent CO2 or 100 percent CO2.

MIG Welding Appearance

Solid wire will produce a smoother weld puddle, which results in less spatter and cleanup after welding. Solid wire welds generally look better than flux-cored welds. Cleanup is a disadvantage of flux-cored because the slag from the used flux needs to be removed with a chipping hammer or brush after welding. The aesthetics of a flux-cored weld are generally not as smooth as a solid wire weld.

MIG Welding Applications

I like to think of flux-cored welding like Stick welding with an infinite stick electrode that just keeps coming out the end of the torch. Thus, flux-cored welding works very well in many of the same applications as Stick welding.

Using a self-shielded flux-cored wire also means there is no need to haul around a shielding gas bottle so it offers a level of portability that you will not be able to achieve with solid wire. The flux within the wire shields the finished weld very well in outdoor applications where shielding gas coverage with the solid wire process may be inadequate. Flux-cored wire tends to do a little better when welding on dirty material because the flux does a better job than shielding gas to keep an inert environment as the weld heats up contaminants.

On the flip side, there are some strong pros to using solid wire and shielding gas. Solid wire generally requires less heat input to weld a given thickness, so control of the heat-affected zone is smaller than using flux-cored. That also results in being able to weld thinner materials using a solid wire. For example, on our small Millermatic® product we recommend only flux-cored down to 18 gauge, whereas solid wire can adequately weld 24 gauge. Solid wire really shines on body work in the automotive world.

MIG Welding Techniques

There are some slight differences in technique when you look at welding with the two different types of wire. Flux-cored has a flux in the wire that produces slag, so you will want to drag the torch. This minimizes the slag at the front end of the puddle and keeps the arc stable. Solid wire on mild steel can be welded by pushing or dragging, but pushing would be the preferred technique. The stick-out length or distance from the contact tip to the weld puddle also differs between the two wires. A short stick-out (1/4-inch to 1/2-inch) is preferred with solid wire whereas a bit longer stick-out of 1/2-inch to 3/4-inch is preferred with flux-cored.

These are just the basic differences between flux-cored wire and solid wire, but for more information you can check out on Millerwelds.com.

In our Millermatic line of products, the welder has the flexibility of using flux-cored wire or solid wire with a shielding gas, because all of the machines come standard with a gas valve for shielding gas. The equipment does require different setups for flux-cored and solid wire.

The biggest setup change is switching the polarity of the machine from electrode positive to electrode negative. This is done easily on the Millermatic welders by reversing the leads on the output stud of the machine. There is also a label on the inside cover to show the proper configuration.

Another setup change is the drive rolls you use in the wire drive. Knurled drive rolls will help provide enough traction to push the flux-cored wire through the gun without crushing and deforming the wire in the groove of the drive rolls. The flux that flakes off and goes into the gun liner isn’t corrosive like solid wire flakes, so the flux will not cause liner obstructions
like solid wire flakes.

Find the Best Deals on Miller Welders

Visit Baker’s Gas and Welding for deals on MIG welders and welding supplies.

Ben Romenesko has been with Miller for over six years, working with the

Millermatic products and ArcStation products. He originally came to the company as a mechanical engineer and is currently serving as a product manager.

Ed Cyzewski


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