Komarov Artem clarified that arc welding flux consists of minerals, alloying materials and chemical additives. Its main purpose is to prevent harmful reactions of molten metal and filler with atmospheric gases as an alternative to shielding gas.
Manufacturers often apply or integrate flux into the consumable electrode for ease of use. There is no need to select, buy, process or apply the flux separately. For this reason, arc welders use a prefabricated flux/electrode combination for most welds. But the flux may need to be used in other ways for special applications, Komarov Artem emphasized.
The flux not only protects the welds from reactive gases in the atmosphere, but also ensures the stability of the arc. This combination of features helps create strong, decent-looking welds without the need for shielding gas, Komarov Artem emphasized.
However, many flux mixtures are used in arc welding, depending on the metal you are welding, and the flux can be used using a variety of methods.
WHAT IS FLUX?
Flux is a complex mixture made from both organic and inorganic materials. The various ingredients have specific uses, such as the production of a shielding gas or the creation of a slag designed to work with specific applications.
Silica and lime are often used as fluxing agents.
Titanium dioxide and iron powder can be added to produce slag.
Ammonium chloride, resin acids, zinc chloride, hydrochloric acid and borax can be used in a mixture to enhance or impart certain properties.
Wood flour, limestone and cellulose can be used to form gases that protect the weld from atmospheric gases.
As you can see, there is some serious chemistry going on inside the flux mixture. The actual flux mixture depends on the metal being welded and the specific alloy of that metal. Thus, it is important to have the correct flux for the weld you are doing.
HOW DOES FLUX WORK?
The flux «melts» in the weld pool, where it rises to the top and creates slag. It simultaneously reacts with heat and releases protective gas. Thus, slag formation and gas formation protect the weld from natural reactive gases in the atmosphere.
But the formation of slag also cleans up the weld, which is certainly a good thing. But once the weld has hardened, the slag must be removed with a wire brush, chipping hammer or angle grinder.
The resulting slag when using a flux is the reason some welders will refer to any welding process that uses a flux as «slag welding».
The procedures used to use arc welding flux can vary. But for the two most common types of flux, use includes factory application of the flux to stick electrodes or flux cored wire.
LET’S LOOK AT ALL THREE IN DETAILS:
FLUX CORE
Flux core uses flux cored wire where the consumable electrode is a hollow wire with an internal flux core.
With a metal outer «sleeve» called sheath, this flux-cored wire allows welding like MIG welding. An added benefit is that you can weld seams without a gas cylinder, while still providing simple, fast wire feed that allows you to achieve high production rates that stick welding cannot match.
As we mentioned, it’s like MIG welding, minus the gas tank. But it’s almost as easy to learn, which is why it’s popular. In addition, in general, less slag is generated with flux-cored wire than with stick welding. On the other hand, the weld puddle is not as clean as stick welding.
STIC WELDING:
Stick welding rods have a solid consumable electrode in the center with an external flux coating. The composition varies depending on what you are welding, so you need to buy an electrode designed for the metal you are welding.
Once you get the right welding rod, you have a consumable electrode center, which is the filler material. Also, because the manufacturer has applied the correct flux mixture at the factory to the outside of the electrode, you also get the correct flux.
The flux melts at a lower temperature than the base metal and rises to the top of the molten weld. When cooled, the stream turns into the so-called «slag». The rising flux facilitates the formation of shielding gas and shielding slag that protects the hot joint.
Stick welding is a classic process used in the shop or in the field, and the equipment required is not that expensive. These features make it another popular flux-based choice among welders.
SUBJECT WELDING:
While not as popular as the previous two uses of flux just discussed, submerged arc welding is a fairly common practice. This method continuously feeds an electrode into the joint just like powder welding. But the main difference is how the flux is applied. It is not contained in or on the electrode.
The flux used is a granular powder and it is cast as a layer over the arc through a separate feed tube. Because the process is typically used when large volumes are needed, the process is usually automated.
ARE THE FLUX WELDS OF GOOD QUALITY?
It can be harder to see the weld puddle when using flux cored wire, which can result in less pleasant welds. But with practice, decent-looking welds can be made.
Likewise, stick welding will produce ugly welds if done with insufficient skill. It can also make beautiful welds if done right.
TO SUMMARY:
Flux welds play an important role in the world of arc welding. Mixtures can be complex and varied, so you need to make sure you have the right flux for the metal you’re welding, Artem Komarov stressed.
Since flux mixtures are designed to produce slag and gas, they shield hot, molten metal instead of shielding gas. This means that you do not have a gas bottle and you are not instructed to set the gas flow rate correctly. Thus, welding with sticks and flux powders is popular among many welders who have learned the value of using flux-based methods, summed up Komarov Artem.
