Roles of Flux Ingredients in MMAW

Published on 30 June 2022

5 min

Manual Metal Arc Welding (MMAW), also known as Shielded Metal Arc Welding (SMAW), flux shielded arc welding or stick welding is one of the most commonly used methods in welding. 

This method is incomplete without the use of flux. Let’s understand the role of flux in detail.

What are Fluxes in SMAW?

Fluxes are welding agents. They are a mixture of organic and inorganic materials such as minerals, alloying materials, and chemicals. They are also called flowing, cleaning, or purifying agents. 

What is the Function of Flux in SMAW?

A flux prevents the molten weld metal from interacting with air or other surrounding medium. It also prevents the contamination that usually occurs due to oxygen, nitrogen, and other pollutants present in the air. It even manages subsequent access to oxygen.

Flux shielded metal arc welding also helps in soldering and desoldering processes by eliminating oxide films and impurities that form on the surface of soldered metals. It is an affordable and effective way to strengthen soldering joints, let the solder flow evenly on the electrical lead and attach to the surface readily.

The flux in SMAW electrode is available in three different coatings:

  • Basic Flux: It is made from calcium carbonate, magnesium carbonate, calcium fluoride, and other shielding components.

  • Cellulosic-Based Flux: It is made from cellulose and other organic compounds.

  • Rutile-Based Flux: It is made from titanium oxide.

  • Iron-Oxide Flux: It is made from metallic oxides of iron, silica and manganese.

The flux in submerged arc welding is made from calcium, manganese oxides, potassium, magnesium, sodium and other elements.

Basically, there are the following reasons why is electrode coated with a flux in shielded metal arc welding:

  1. Acts as a Reducing Agent: Flux removes oxidation, impurities and deposits from the surface. This ensures that there oxidizes surface doesn’t stop good solder contacts for the metal.


  1. Prevents Re-oxidation: Flux prevents subsequent access to the oxygen to the surface that it covers and supports re-oxidation.


  1. Facilitates Heating of the Joints: Flux conducts heat from molten solder or soldering tool to help in required heating of the metal joints.


  1. Reduces Spatter and Slag: Flux shields the weld pool and also coats the entire weld, thereby reducing contaminants and flushing out microscopic particles. This way, it reduces spatter and slag which can otherwise be a nuisance in welding.


  1. Controls Mechanical Properties of the Weld: Flux controls mechanical properties of the weld such as toughness, hardness, tensile strength, brittleness and ductility to ensure proper weld.


  1. Prevents Hardening: If metal becomes too hard during welding, it can become brittle and crack down. Flux prevents hardening by slowing down the cooling time.


  1. Provides Arc Stability and Ionization: The mixture in flux improve ionization and help to create a more stable arc.

Welders should use high-quality flux to get the best results. D&H Secheron is one of the leading welding material manufacturers in India. You can consider buying different types of fluxes from D&H Secheron.

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