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Understanding the Role of Flux in Welding: Its Purpose and Function

May 16, 2023 | News, trade school

Welding is a process that combines materials together at a high heat to melt and form a weldment. Welding is done on metals, thermoplastics, and even wood and is responsible for the creation of many different projects.

Flux welding is a semi-automatic welding process that comes into play when working with thicker materials.

Keep reading this guide to learn more about the purpose and function of flux welding.

What Is Flux Welding?

Flux consists of a mixture of chemicals and other materials that protect molten metal in the weld pool from contamination. The use of flux in welding began in the 1950s and has since become the preferred alternative over stick welding.

Why Is Flux So Important in Welding?

The main reason why flux is so important in welding is that it helps prevent the metal from rusting and oxidizing. Flux also helps the flow of the filler rod which prevents the metals from becoming porous.

Different Types and Composition of Flux

There are three different categories of flux including:

  1. Cellulosic-Based Fluxes: Cellulosic-based fluxes are made up of organic cellulose and a lime binder. The biggest pro of these types of fluxes is that they do not contain heavy slags which could interfere with the welding process.
  2. Rutile-Based Fluxes: Rutile-based fluxes are made out of titanium oxide and are considered the most “welder-friendly” type of flux due to their slag and arc control.
  3. Basic Fluxes: Basic fluxes are made up of either ammonium chloride or resin acids. There are three types of basic fluxes which include low-solids/no-clean fluxes, rosin fluxes, and water-soluble fluxes. The perk of these fluxes is that they are able to create welds at low temperatures.

Properties of Flux

Flux forms a slag and a gas shield which protects and forms the overall structure of the weld. It also works to assist the stability of the arc and interacts with the weld pool to make the metal clean and high-quality.

Flux often contains materials such as limestone, silica, dolomite, lime, borax, and fluorite.

How Does Flux Work?

Flux contains a base material and an activator that works to dissolve the oxides on the surface of the metal and increases the wetness of the liquid solder. By increasing the wetness of the liquid, the solder is able to flow over the surfaces evenly without dewetting in the process.

Without flux, your solder will not stick to the metal surface. This will likely lead to oxidation layers which cause scales on the surface on which you are working. As a result, your welding project will be extremely messy or fail altogether.

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What Arc Welding Processes Use Flux?

These are the three different arc welding processes that use flux:

  • Flux-Core
    Flux-Core welding is a process that’s mostly used when welding materials that are rusted or contaminated. It consists of a tubular electrode, flux, and voltage.
  • Stick Welding
    Stick welding is known as manual arc welding and is great for welding different types of metals like aluminum, copper, nickel, steel, and iron. Stick welding uses a tubular electrode that’s also covered with flux for protection.
  • Submerged Arc Welding
    During submerged arc welding, an electric arc and electrode continuously combine and generate heat. The flux used in this type of welding is powdered and covers the electrical arc.

Difference Between Stick and Flux-Core Welding

While stick welding and flux-core weldings are both similar, there are a few key differences that set the two apart.

Stick welding uses a metal electrode that contains a layer of flux. On the other hand, flux-core welding uses an electrode with flux that is coated in metal.

Stick welding is often the preferred choice for welders completing simple projects. While working with the electrical arc may be tedious, the process itself is relatively simple.

However, when it comes to larger projects and repairs, flux-core welding is the better option. That’s because the speed of the electrodes is faster.

The Welding Industry Is Booming

Did you know that the welding industry is expected to grow from $20.99 billion to $28.66 billion by 2028? One of the great benefits of starting a career in the welding industry is that welders are currently in high demand, and you don’t even need a college degree.

In order to become a certified welder, you will need to enroll in an institution that offers a reputable welding certification program.

You’ll be happy to know that you can start this new career path today at the Erie Institute of Technology with our outstanding welding technology program.

You can either give us a call at (814) 747-5215 or apply online today to get started.


Ross Aresco


Ross Aresco is the CFO of Erie Institute of Technology. Erie Institute of Technology (EIT) is an Erie Pennsylvania technical/trade school providing training programs for medical, computer, electronics, manufacturing, and technology careers. EIT offers programs in many different areas to suit your interests and talents.

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