While many welders might be tempted to use a “one size fits all” wire, no single filler metal is suitable for every job. MIG solid wire and flux-cored wire, for instance, have different properties that work better in certain applications.
Although solid wire is effective for many applications, it is slow for out-of-position welding. Flux-cored wire, however, is often faster for out of position and has high deposition rates to maximize productivity.
“One of the biggest reasons to use flux-cored wire is for out-of-position work,” says Jeff Garraux, an applications engineer at ESAB Welding & Cutting Products. “Solid wire is good for flat or horizontal (in-position) work, but for out of position, flux-cored wire has a huge advantage. Not that solid wire can’t work, but typically you have to go to short arc transfer or pulsed MIG, which makes it very slow for out-of-position welding. Flux-cored wire has the slag system on it that helps hold the puddle and the bead shape as the weld cools.”
Spec’ing the job using solid or flux-cored wire depends on many variables. As far as performance is concerned, both wire types produce quality welds with good weld bead appearance when applied correctly and used with the proper settings.
With thinner materials, solid wire is typically the better fit because it provides better heat control, which means less warpage and distortion issues. The thinnest materials for flux-cored wire welding are 3/16 in.
“If you’re welding thin plate, solid wire is just going be a better fit because you can get down into it with a short circuit and that really reduces overall heat,” Garraux says. “It is harder to control the heat input with flux-cored wire on thinner material.”
For welding on thicker materials, however, solid wire may not provide adequate weld penetration, especially if the wire diameter is too small, such as a 0.035-in. wire. Flux-cored wire can be a better solution for welding thick materials.
“For thicker materials, flux-cored wire enables you to increase deposition rates with less heat input,” Garraux says. “With the solid wire, sure you can increase deposition rates but your amperage levels would be so high that eventually you would be destroying metallurgical or mechanical properties. The energy it takes to burn off a 0.045-in. solid wire versus a cored wire is very different amperage-wise.
“Welding out of position with solid wire on thick materials can be done with pulse welding, but it requires a more expensive machine,” he adds. “You can take a basic CV machine and weld in all positions with flux-cored wire.”
Among the reasons solid wire might not be used is the weld prep. Solid wire requires the base material to be free of rust, mill scale, dirt or oil.
“When welding with solid wire, you have to have extremely good metal preparation to remove all impurities plus mill scale,” says Bob Gulas, business product manager at ESAB. “Most people do a lot of grinding or even a pre-blast of the material. The majority of people welding buildings, columns and other structures prefer the flux-cored wire because it requires minimum pre-weld cleanup.”
The common shielding gases for flux-cored wire used for welding steel are 100 percent CO2 or a 75 percent/25 percent argon and CO2 mix. Flux-cored wire operating with CO2 offers better weld penetration, but also tends to create more spatter, whereas wire for a 75/25 mixed gas has reduced spatter, along with a smoother weld bead appearance.
“One thing that a lot of people in the industry overlook is that using flux-cored wire that runs on straight CO2 provides a very big cost savings,” Gulas says. “It is cheaper and it only takes one cylinder. And it’s a reactive gas so it’s going to give you a little better weld penetration and a little better cleaning action.”
Some flux-cored wires that use mixed gas don’t have a comparable CO2 version of that wire, however, so sometimes the type of wire required is the driver for gas selection.
The most current flux-cored wires available today are very user friendly. So much so that even a first-time welder can use them with ease.
“We’ve taken people that have never welded and had them welding out of position very quickly with a flux-cored wire,” Garraux says. “Solid wire takes a lot more skill and a lot more manipulation of the arc to make sure the bead is nice and the profile is good, especially for out-of-position welding.”
Welders must be aware that when switching from solid to flux-cored wire, they must change their habits. Flux-cored wire operates differently and the operator must make adjustments.
Overall, wire manufacturers have recognized how the industry is working and developing products to address this. As more and more welders retire and newer welders come in with little or no experience, it is up to the manufacturing arm of the market to develop products to help those with less experience attain a higher skill level quicker.
“In the past, if you went into a shop, maybe 60 percent of the welders had 20 plus years of experience,” Gulas says. “Today, you walk into a shop and most of the welders have 0 to 3 years of experience. So from our perspective, it’s how can we help those welders achieve better performance faster.”
The newer thinner sheath flux-cored wires, such as ESAB’s Dual Shield X series, are one example. A thinner sheath concentrates the current, which in turn, produces a much more forgiving wire.
A forgiving wire helps the operator obtain good results when:
- Running at the low and high end of the operating ranges
- Running at the low end but still having enough arc energy to prevent spatter
- Welding out of position using a higher top-end current level
- Welding at the high end to maximize travel speeds
- Support of slag system for out-of-position welding
- Ease of slag removal, cleans up without worry of inclusions
However, older technology with thicker sheath wire still has its place.
“When a specific penetration profile is needed, the thicker sheath wires give a little better weld penetration,” Gulas says. “These older wires still have their uses in the industry. When trying to do heavier plates and higher speed welds in the flat or horizontal, we’ve had better luck with the thicker sheath wire.”
And that is an example of where a filler metals expertise can be of value. There are many variables in any given shop doing welding and it is not the practical, or even possible, for designers and welders to keep up with all the available solutions.
“It comes down to what that shop is trying to accomplish,” Gulas says. “We have to drill down to what that shop needs. So we ask questions – what initiatives are you trying to accomplish, what are the tenures of your welders, what are your specific problems. They are receptive because they know we’re not just trying to sell an expensive wire but that we’re trying to help them be better at what they are doing.”