What is Flux & Function of Flux in Welding

The terms flux core and welding are closely related words in welding. But what is flux core welding and what are the functions of flux in welding?

Flux is a mixture of minerals, chemicals & specialized materials that protects welds from atmospheric contamination and natural reactive gas such as oxygen & nitrogen. Besides, the role of flux is to prevent further oxidation impurities and increase the wetting process in welding.

In this guide, I will explain the details of flux core and its functions in welding. In the meantime, you will learn the benefits of using flux in welding.

What is Flux?

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Flux is a soldering element made with alloying metal, minerals and chemicals. It surrounds welding electrode that protects welding from different contaminations like oxygen, nitrogen and atmospheric dust. Additionally, flux helps to control various mechanical and arch properties.

The flux melts in the welding area during welding and turns into liquid slag. Then, the slag cover the whole welding operation and protect the molten welding.

As a result, the welding process stays safe from unwanted contamination. But later, the flux cools and solidifies. After welding slags should be removed by chipping, brushing or sanding.

Functions of Flux in Welding

Flux has some core functions in welding. These functions are required to accelerate the welding process, keep the welding area free of contamination and protect the welding with alloying.


The role of flux in shielding is very important. Flux is used during welding that melts in the welding pool. The melted flux produces a protective layer around the welding zone. Every welding has some potential atmospheric contamination that affects the welding quality. However, using flux can help to prevent contamination and protect the welding. Flux work as shielding gas in flux core welding. If you want to weld without gas, then flux helps to do so.


Flux works excellent for deoxidation. First, flux dissolves the existing oxides on the metal welding surface. In the meantime, the molten flux spreads around the welding and covers the surface to prevent oxidation.


Contamination is a common issue in welding zone and it can reduce the welding quality. Flux core mixes with foundries & helps to remove impurities and unwanted contamination from the welding metal surface. Besides, flux is used with titanium as the effective, desirable trace element to remove impurities from the welding surface effectively.


Some certain fluxes, named rosin, acid, and putative, work excellently for smoother welding. These specified fluxes work to improve the quality of welding. Generally, these increase the arch stability and improve the flow of power on molten metal. As a result, the smoke and fumes are reduced in welding, ensuring a smoother & sound welding.

Welding Techniques Utilizing Flux

We will discuss here some specific techniques that uses flux in welding.

Submerged Arc Welding (SAW)

Powdered flux is recommended soldering ingredient for submerged arc welding. The submerged welding process produces a pressure between the electrode and workpiece. That pressure will reduce after using flux. Note that powdered flux layered on the welding surface produces a protective gas shield and slag. As a result, the protective shield protects the welding area from outside dirt’s.

Flux-Cored Arc Welding (FCAW)

Flux core welding
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In this welding process, double shielding gas used. One is flux itself and another external gas (mainly carbon-di-oxide or mixture of co2 & argon). That why it is called duel shield welding process.

Besides, flux cored is fairly similar to metal active gas welding. In Flux-Cored Arc Welding, flux is used as a wire-fed electrode. Mainly, flux is used in arc welding for maximum protection.

Electro slag Welding (ESW)

Electro slag welding is highly effective and productive welding process.  It uses single pass wire to weld thick metal. In this method, the electric wire should be pressurized and fed to the welding point. Then, flux is added to the welding point.

Hence, the added flux on the welding surface creates a protective layer around the welding zone thus protecting the weld from contamination. However, the gaseous shield is also used in electro-slag welding for more protection.

Benefits of Using Flux in welding

We already know that using flux plays an immense role in speeding the welding process. Still, we are discussing certain benefits here so you can understand the advantages of using flux in welding.

Improved weld quality

Using flux in welding helps speed up filler metal’s wetting process. Besides, you can make a strong welding joint with the support of flux material as it reduces external contamination or impurities.

Overall, flux reduces the porosity from the surface and makes a strong welding joint improving welding quality.

Reduced defects

The welding flux drives the arc migration and leads to the uniform migration. Then, the flux operates the uniform heating to reinforce the heat.

As a result, flux melts, making a layer on the welding surface to cover the defects. Consequently, the welding defects are reduced automatically.

Control over the weld pool

Flux can control the weld pool.

First of all, flux produces the shield and protects the welding process. Second, flux improves the arc stability and works for slag formation. Besides, flux is used in welding as an alloying element.

Additionally, flux has great performance in controlling fluidity in welding and removing contamination.

Increases filler rod flow

Flux improves the wetting process of filler metal in welding. It also increases the flow of solder rod during brazing. Overall, flux reduce porosity and make strong bonding in welding joint.

Reduce contamination

The melted flux cover the welding zone and protect the welding surface from atmospheric contamination.

Work on difficult to weld metal

Flus is the most reliable element to weld on difficult metal. For example, many welders want to avoid welding on white or pot metal because of the potential difficulties. But using supper alloy 1 flux can solve this problem and make the welding easy.


Flux is the best supportive solder in the welding process. It has several advantages in welding as we mentioned. Knowing the proper use of flux will make any welding process easier.

Flux protects welding pool from contamination, improves quality and reduces porosity from the welding surface. However, it is necessary to know the rules and fields of use of flux. Otherwise, the flux can hurt your welding.

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