Welding is a process of joining two or more metal parts together using heat and pressure. One of the key elements in welding is the use of a flux, which is a material that is applied to the surface of the metal being welded. The main function of a flux in welding is to protect the welding area from oxygen and other gases in the atmosphere, and to facilitate the flow of the molten metal. In this article, we will discuss the main uses of flux in welding, the different types of flux, and how to choose the right flux for your welding application.
Uses of flux in welding
Protection from Oxygen and Other Gases
One of the main functions of a flux in welding is to protect the welding area from oxygen and other gases in the atmosphere. When metals are heated to high temperatures, they react with the oxygen in the air to form oxides. These oxides can weaken the weld and make it brittle, which can cause it to fail under stress. A flux creates a protective barrier that shields the welding area from the oxygen in the air, preventing the formation of these oxides. This is especially important when welding metals like steel, which is highly reactive with oxygen.
Removal of Impurities
Fluxes also help remove impurities from the metal being welded. When metals are melted, impurities like dirt, rust, and oil can become trapped in the molten metal. These impurities can weaken the weld and make it more likely to fail under stress. Fluxes work by chemically reacting with these impurities, breaking them down into a slag that floats to the surface of the molten metal. The slag can then be easily removed, leaving a clean surface for the weld.
Facilitation of the Flow of Molten Metal
Fluxes also play a crucial role in facilitating the flow of molten metal during the welding process. When metals are heated to high temperatures, they become more fluid and can flow more easily. However, the surface tension of the molten metal can cause it to bead up and resist flowing into the joint being welded. Fluxes work by reducing the surface tension of the molten metal, making it easier to flow into the joint and creating a strong, uniform weld.
Types of Flux
There are many different types of fluxes used in welding, each with its own unique properties and applications. Some of the most common types of flux include:
Active fluxes are designed to chemically react with the metal being welded, producing a slag that helps remove impurities from the weld. These fluxes are commonly used in welding processes like submerged arc welding (SAW) and electroslag welding (ESW).
Inactive fluxes do not chemically react with the metal being welded, but instead create a protective barrier that shields the welding area from the atmosphere. These fluxes are commonly used in welding processes like gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW).
Agglomerated fluxes are made up of a mixture of different materials, including metal oxides, silica, and other compounds. These fluxes are designed to provide a combination of the benefits of active and inactive fluxes, including impurity removal and protection from the atmosphere.
Fused fluxes are made by melting a mixture of different materials together and then cooling them to form a solid. These fluxes are commonly used in welding processes like submerged arc welding (SAW) and electroslag welding (ESW).
Choosing the Right Flux
Choosing the right flux for your welding application is critical to achieving a strong, high-quality weld. When selecting a flux, you should consider a number of factors, including:
The Type of Welding Process
Different welding processes require different types of fluxes. For example, submerged arc welding (SAW) and electroslag welding (ESW) typically require active or fused fluxes, while gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) typically require inactive or agglomerated fluxes.
The Type of Metal Being Welded
The type of metal being welded can also influence the type of flux that is used. For example, active fluxes are often used when welding high-strength steels, while inactive fluxes may be used when welding aluminum or other non-ferrous metals.
The Welding Position
The position of the weld can also affect the choice of flux. For example, when welding in the vertical or overhead position, a flux with good slag control may be needed to prevent the slag from falling onto the weld.
The Required Weld Quality
The required quality of the weld can also influence the choice of flux. For critical applications where the weld must be of the highest quality, a flux with low hydrogen content may be needed to prevent hydrogen-induced cracking in the weld.
Environmental considerations, such as the impact of the flux on the environment and the health and safety of the welder, should also be taken into account when selecting a flux.