Tips for Flux-Cored Arc Welding

January 10, 2009 12:29 PM


Flux-cored arc welding is performed on the same machine as MIG welding, which uses a continuous solid wire.

Flux-cored arc welding (FCAW) has been around since the 1950s, but a survey of consumers conducted by Miller Electric Manufacturing Company suggests that many potential users have questions about the process. Here are some tips about FCAW from Miller product manager Chris Wierschke and welding engineer Amanda D'Arcy.

What it is. In the FCAW process, a continuous hollow wire is fed through a welding gun. FCAW is performed on the same machine as MIG (metal inert gas) welding, also known as stick welding, which uses a continuous solid wire.

In MIG welding, shielding gas is required to protect the weld pool from the atmosphere. That makes it impractical for outdoor repair jobs because a breeze can blow the shielding gas away. That's where FCAW comes in.

"FCAW uses wire that has flux in the middle—just the opposite of stick welding, which has flux on the outside of the electrode," Wierschke explains.

"The flux protects the weld puddle from the environment, so you can use your wire welder for outside repair jobs, as well as inside the shop. To move from shop to field, you just remove one roll of wire and replace it with another.

"Although there is some technique involved, wire welding is easy to learn, even if you haven't welded before," Wierschke notes.

"For larger welds, you don't have to worry about stopping to insert a new electrode, as with stick welding. There's a lot less waste than with stick electrodes," D'Arcy says.

There are two main differences between using solid wire and FCAW. With solid wire, when you weld with a push angle, the shielding gas is directed ahead of your weld puddle, resulting in greater penetration. With FCAW, you drag the gun, rather than push it.
When changing from MIG welding to FCAW, you must change the polarity. "With solid wire, you run the electrode positive, Wierschke says. "With FCAW, you run it negative. Something to keep in mind when you buy a wire welder is how easy is it to reverse the polarity. Some models have switches. Others models require tools.

"Because FCAW uses softer wire, make sure the drive rolls—the wheels that feed the wire through your welding gun—don't pinch too tightly and deform the wire," Wierschke says. "For flux-cored arc welding, you'll want to use knurled drive rolls. Some welders come with a combination drive roll assembly that has both knurled and V-groove assemblies (for solid wire) on one drive roll."

However, knurled drive rolls can grind off tiny bits of wire, which can accumulate in the liner of the gun, creating a blockage. "If your liner gets clogged, the only thing to do is remove and replace it," Wierschke says.

"Although FCAW is pretty forgiving of grease, rust and paint, clean the area as well as possible before welding," D'Arcy advises.

"FCAW wire is a little more susceptible to taking in moisture than solid wire," she continues. "If you don't weld a lot, buy a smaller spool, and store it in a fairly dry place." If FCAW wire takes in moisture, you'll see rust on the outside of the wire and hear spitting and popping as you weld.

Read your owner's manual and ask your dealer about the best wire for each application. "Once most users use a wire welder, they don't want to set it down," Wierschke says. 

For More Information

For tips on solid wire welding versus flux-cored arc welding, visit

You can e-mail Darrell Smith at

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