All that You Need to Know About Welding Flux
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The term flux, in the English language, means a continuous flow. In the world of welding, flux denotes a mixture of materials, typically carbonate and silicate. The key use of flux in welding is to protect the weld metal from contamination by atmospheric gases.
The flux ingredients are usually: calcium, calcium carbonate, calcium fluoride, magnesium, potassium and manganese oxides, sodium, silica, and aluminium oxide. The flux ingredients come together to help stabilize the arc and have more control over the mechanical properties.
What are the functions of Welding Flux?
A shielding agent: The welding flux has a lesser density than the weld metal. Therefore, while welding, the welding flux melts and floats around the weld and deposits itself.
Prevents oxidation: The welding flux, upon heating, produces gases that push back the atmospheric gases and prevents oxidation as well as any potential reactions that could occur with nitrogen.
Creates slag for further shielding: The remains of welding flux solidify to create slag, which adds to the protection of the welded area.
Usage as a coating in electrodes: Many forms of arc welding use welding flux, i.e, Shielded Metal Arc Welding (SMAW), Submerged Arc Welding (SAW), and Flux Cored Arc Welding or FCAW.
Use of Flux in Welding Processes
SAW
Submerged Arc Welding or SAW uses welding flux, also commonly known as SAW flux here, to provide the shielding properties mentioned above. SAW flux is usually granular in nature to provide higher deposition rates. The mechanical properties of the weld are also determined by the flux.
The SAW flux also controls the heat in while welding, which helps in concentrating the heat and furthering deeper weld penetration.
SMAW
Shielded Metal Arc Welding or SMAW uses solid core wires for its electrode. The welding flux is coated to the bare electrode by a process called extrusion. The coated electrode aids in arc striking, arc stability, and slag removal apart from the functions of the welding flux.
FCAW
Flux Cored arc Welding, as the name suggests, uses welding flux as a core part of its process. The flux-cored wire used in this welding has flux at its core.
The flux-cored wires are further divided into gas-shielded and self-shielded. These are self-explanatory - the gas-shielded ones require additional shielding against atmospheric gases while welding. Other common subtypes of flux-cored wires include low alloy steel flux.
Flux-cored wire consumables have many benefits wherein they have high deposition rates and can be used in all welding positions. They result in stronger and cleaner welds when compared with other forms of welding. This makes Flux Cored Arc Welding ideal for welding outdoors, in windy conditions, and for welding contaminated materials with scale and rust too!
While there are many types of welding, which type of welding to be used is determined by the scale and nature of the project, the outcome required, and the welding positions suitable.
Never let the materials available be a deciding factor. All your welding materials and welding consumables are available at D&H Sécheron. Among the many welding products that D&H Sécheron has to offer, you can find many types of welding flux in our MAXFLUX range and Flux Cored Arc Welding at our website.
Arc welding flux consists of minerals, alloying materials, and chemical additives. Its primary purpose is to prevent harmful reactions of the molten metal and filler material with atmospheric gasses as an alternative to shielding gas.
Manufacturers often apply or integrate the flux into a consumable electrode for ease of use. Simply weld, and while the consumed electrode fills the joint, the flux becomes consumed, giving all its benefits depending on its added minerals, chemicals, and alloying elements.
No need to select, buy, handle, or apply the flux separately. For this reason, arc welders use the pre-manufactured flux/electrode combo for most welds. But specialty applications may use flux in many other ways.
Flux protects welds from reactive gasses in the atmosphere and provides arc stability. This combination of features aids in creating strong, decent-looking welds with no need for shielding gas.
However, arc welding uses many flux mixtures, depending on the metal, and various techniques can employ the flux. The assembled information in this article presents what flux is and how it shows up in arc welding.
What Is Flux?
A close-up image of flux-coated stick electrodes
Flux is a complex composition made from both organic and inorganic materials.
The different ingredients have specific uses, such as producing shielding gas or creating slag designed for specific applications.
For example:
- Silica and lime: flux agents that remove iron and impurities during steel production
- Titanium dioxide and iron powder: can produce slag when added; iron powder also increases the heat in the welding arc, increasing penetration and travel speed
- Ammonium chloride, resin acids, zinc chloride, hydrochloric acid, and borax: can enhance or impart certain properties in the mixture
- Wood flour, limestone, and cellulose: generate gasses that shield the weld from atmospheric gasses
Serious chemistry is happening inside a flux mixture. The actual flux mixture depends on the metal and its specific alloy. So, having the right flux for the weld is important.
How Does Flux Work?
Flux &#;melts&#; into the weld pool, rising to the top and creating slag. It simultaneously reacts with the heat and releases a shielding gas.
So, the slag and gas formation protects the weld from the natural reactive gasses in the atmosphere.
Hardened slag peeling from a SMAW weld
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But slag formation also purifies the weld, which is a good thing. But once the weld has hardened, the welder must remove the slag using a wire brush, chipping hammer, or an angle grinder.
The resulting slag is why some welders refer to any welding process using flux as &#;slag welding.&#;
What Arc Welding Processes Use Flux?
The procedures used to employ flux while arc welding can vary. But the two most common types of flux involve factory application of the flux to stick electrodes (SMAW) or a flux-cored wire (FCAW)
Another common method used in the pressure vessel industry involves casting the flux as a blanket over the arc, known as submerged arc welding (SAW).
Let&#;s take a closer look at all three.
Flux-Core Welding (FCAW)
How flux-cored welding works
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Flux-core welding (FCAW) uses a flux-cored wire where the consumable electrode is a hollow wire with an interior flux core.
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With a metal outer &#;sleeve,&#; called a sheath, this flux-cored wire produces welds like MIG welding (GMAW).
An added benefit is welding without a gas bottle while providing the simple, fast wire feed to achieve high production rates that stick welding (SMAW) cannot match.
Cross section of flux-cored wire
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Sometimes, people call flux-cored welding gasless MIG, and it&#;s popular for applications like windy conditions where shielding gas is useless as the wind blows away.
As mentioned, it&#;s similar to MIG welding, minus the gas tank. But it&#;s almost as easy to learn, which is why it&#;s popular for the beginner welder.
Also, in general, flux-core wire produces less slag than stick welding. This aspect makes it easier and quicker to remove.
Read more: Flux Core vs. MIG Welding: Differences Compared
Stick Welding (SMAW)
How stick welding works
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Stick welding (SMAW) rods have a solid, consumable electrode at their center, with an external flux coating. The composition varies depending on the weld, so the welder must buy an electrode designed for the metal.
Having chosen the correct welding rod for the application, a consumable electrode center is the filler material.
Plus, since the manufacturer applied the correct flux mixture at the factory to the outside of the electrode, it&#;s the proper flux.
Popular Stick Welding Electrode (E) used for general-purpose fabrication, construction, pipe welding, and shipbuilding
The flux melts at a lower temperature than the base metal and rises to the top of the molten weld. When cooled, the flux forms into something called &#;slag.&#;
Flux rising to the top facilitates the shielding gas, removes impurities from the weld, and forms a protective slag, which protects the hot joint.
Stick welding is a classic process used in the shop or the field, and the necessary equipment is not that expensive. These features make it another popular flux-based choice among welders.
Submerged Arc Welding (SAW)
Submerged arc welding example close-up
While not as popular as the prior two flux uses just discussed, submerged arc welding is a fairly common practice. This method continuously feeds an electrode into the joint, just like flux-cored welding. But the major difference is in the application of the flux. It&#;s not in or on the electrode.
The flux used is a granular powder, and it acts as a layer over the arc via a separate feed tube attached to a flux hopper. Since the process is applicable when high volumes of welding are necessary, this process is usually automated.
FAQs
Is Flux Hard To Use?
Flux-core wire feed systems don&#;t feel as smooth as a regular MIG machine. However, after running a few beads, it becomes clear that it isn&#;t much harder.
Shielded metal arc is tricky for many new welders. The electrodes have a lot to do with it. Welding rods with more flux are easier to work with.
Each rod has a specific purpose, which is something to remember when choosing an electrode.
Are Flux Welds Of Good Quality?
When using flux-cored wire, it can be harder to see the weld puddle, potentially resulting in less pleasing welds. But with practice, anyone can make decent-looking welds.
Likewise, stick welding will produce ugly welds when done with insufficient skill. It can also make beautiful welds when done properly. After removing the slag, the true character of the welds becomes visible.
Can You Use Flux Indoors?
Using flux-core wire gives off more potentially toxic fumes than using a normal MIG machine. The flux itself releases gasses strong enough to shield molten metal.
When welding indoors, keep the area as well-ventilated as possible and/or wear the proper respirator.
Do Flux-Based Methods Make Strong Welds?
Yes, the welds can be of high strength. The welds will be as strong as any other welding method with proper care and attention. Penetration is typically deeper when using flux, which helps provide added strength.
Are Flux-Based Techniques Easy Enough For A Hobbyist To Use?
Using flux-cored wire is a great way to learn the skill of welding. It&#;s a straightforward way to get the hang of a new skill.
Learning to stick weld depends on the electrode. For flat, horizontal welds on heavy material, is the best choice. So, that&#;s a good place to start. Then making the jump from to electrodes for vertical welds isn&#;t that large of a jump.
Wrapping It Up
Flux-aided welds play an important role in arc welding. The mixtures can be complex and vary, so a welder must have the right flux for the welding metal and position.
But for stick or flux-cored welding, the flux is &#;preinstalled&#; as long as the electrode/wire for the joint is right.
Since flux mixtures produce slag and gas, they protect the hot, molten metal instead of shielding gas. That means no gas bottle to lug around and no correctly setting gas flow rates. So, stick and flux-cored welding are popular with many welders who have learned the value of using flux-based methods.
Yes, there will be no pretty stacked dimes like a TIG (GTAW) weld. But flux does provide strong, contaminate-free joints when done right and, with a little practice, can make decent-looking welds.
Plus, since there&#;s no gas, things like welding in windy conditions are possible. MIG (GMAW) and TIG (GTAW) welding struggle to do that.
So, there are advantages to flux-aided arc welds, and it&#;s well worth the time and effort to learn about and practice with methods that use flux. It&#;s a valuable welding skill to have at one&#;s disposal and well worth learning.
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