If you are currently looking into giving the more exotic flux core wire a try for TIG welding but not sure how to set it up or what to expect from the wire, I compiled a couple of useful information. This Info will help you to create a decent weld and get the full benefit of this special filler material!
So, how to TIG weld with flux core wire? A general recommendation for welding flux-cored TIG wire is to use a current slightly below the setting for solid wire. Also, the welding plant needs to be configured for DCEN. Extra cleaning of the weld is necessary when welding multiple passes, as the flux core creates a slag.
That was the bare bone answer, but there is much more to it, so if you want to get all the details right. If you are still interested in giving flux core wires for TIG welding a try, please continue!
What is a Flux Core wire and what is it used for?
Before we start, it is helpful to understand what a flux core wire is and what it contains. A flux core wire is similar to a stick electrode, where the metal rod is covered with a powder that creates the slag, the shielding gas, and different additives to the welding process when ignited. For the flux core wire, this is very much the same. The main difference is that the powder is enclosed in the hollow wire tube. Regular electrodes and filler wires are solid rods.
So a flux core wire is basically an inside out stick electrode.
Elements of the powder are for example slag building materials, arc stabilizing additives, additional alloying elements, metal powder and gas releasers. Every additive in the filler powder has its reason: The slag building material protects the weld from oxidation while cooling down. The arc stabilizer stabilizes the welding arc, creating an easier environment to weld. The additional alloying elements will diffuse into the weld when molten and improve the metallurgy of the weld. More metal powder is added, because the powder is easier to melt than solid material, and that increases the overall welding speed with less energy input.
Applications for flux-core TIG welding are for example welding a butt root on stainless steel requires a back purge. The slag created shields off the weld from oxidation. Or in pipe welding, it can be an alternative to stick welding.
Flux Core wire, a general ingredient list
The answer to this question depends on the kind of flux core wire you use. However, here are some of the commonly used elements that are manufactured in flux core wires and there purpose in the powder mixture:
- Titanium dioxide TiO2 – rutile ingredient
- Calcium carbonate CaCO3 – purification of iron/ Improving the metallurgy
- Sodium fluoride NaF – Improving the metallurgy
- Boron B – Additive
- Sodium Aluminum Fluoride Na3AIF6 – Improving the metallurgy
- Aluminium oxide Al2O3
- Molybdenum Mo – Additive alloying element
- Silicon Si
- Manganese Mn – Additive alloying element
- Iron Fe – Base alloy
- Magnesium oxide MgO – Releases additional chemical energy to the process
- Calcium fluoride CaF2
The ingredients differ, and every supplier adds there a secret sauce to the mix or leaves out an additive, depending on the alloy. However, this gives you an idea what you would find inside the flux core wire if you would cut it open.
The special manufacturing process of Flux Core wire
Flux core wire starts as a thin band of metal which is then brought into a “U”-share through bending rolls. After that, the powder is filled continuously into the shape. The last step is closing the wire tube and reducing the diameter by milling to the desired dimensions. There are flux core wires without a visible joint. These wires were manufactured slightly different. By welding the thin metal band together as the first step of the process, the tube appears joint less. The tricky bit is inserting the powder now. Vibration is used to get the powder into the thin tube. This procedure is the more complicated way to do it, and therefore, the wire will be more expensive. However, because the wire is more evenly produced, it is slightly easier to process.
Tips for the welding process
Advantages of TIG welding with Flux Core wire
FCAW, Flux Cored Arc Welding, the higher-level term for TIG flux core welding, is commonly used when the strength and advantages of flux core wire outweigh the additional costs. Above I already listed frequently added micro-alloy elements, slag building chemicals, gas building elements, and additives that are blended in the powder. All of them add special advantages to the welding process. Here are the main advantages:
Deposition Rate: The main and probably most widely used advantage is the higher deposition rate with the same amps compared to a solid wire.
Appearance: Flux cored welds appear smooth and uniform with displaying of a good contour.
Welding in all positions: Flux core wire is allowed for all welding positions. The extra gas that is built by the filler material is helping with the gas coverage from a close distance.
Where you have advantages, there are disadvantages. To decide for yourself if you are willing to accept that in your welding process, have a look at the overview:
Cleaning: Normally, TIG welding does not create a slag. However, flux-core welding does. This means for your weld that you have to get rid of that slag layer. Especially before you continue a multilayered weld! The slag needs to be completely removed without residues. Otherwise, the slag particles will create inclusions in your next pass. So not cleaning properly can nullify all the time savings you had through the higher deposition rate.
Cost: If you have read this far, you probably have noticed that flux-core wire is a bit more complex to manufacture than your everyday solid TIG weld wire. Also, flux-core for TIG welding is less common than for welding processes like MIG welding. Both of these factors contribute to the much higher wire price compared to a similar solid TIG wire. A price of 90$/80€ per pound is not unusual.
Cleaning: Normally, TIG welding does not create a slag. However, flux-core welding does. This means that you have to get rid of that slag layer. Especially before you continue a multilayered weld! The slag needs to be completely removed without residues. Otherwise, the slag particles will create inclusions in your next pass. So not cleaning properly can nullify all the time savings you had through the higher deposition rate.
Is there a flux-cored TIG wire that doesn’t require any Argon gas?
Technically, flux-cored TIG wire generates its shield coverage. However, it is not recommended to weld completely without Argon shield gas support from the torch. Because the wire is not as continuously fed and molten into the weld puddle as with MIG flux-core, a propper shielding gas coverage is tough to achieve. However, you might reduce the Argon flow when welding with a flux core. Give it a try and see what works for your welding job.
How to identify a Flux Core wire?
Types of steel that can be welded with flux wire
18%Cr-8%Ni type stainless steel.
for dissimilar joints between stainless and mild
steel or medium carbon steels.
18%Cr-12%Ni-2%Mo stainless steel.
18%Cr-8%Ni+Nb stabilized stainless steel.
welding duplex 1.4462 stainless steel.
Alternatives for using a flux-core wire
Depends why you were looking into giving the flux-core wire a shot in the first place.
Rooting butts without back purge
Increased deposition rate