What is Submerged Arc Welding (SAW)

source;https://www.canadianmetalworking.com/canadianfabricatingandwelding/article/welding/submerged-arc-welding-tech-tips-and-fundamentals

Submerged arc welding (SAW) is an advanced mechanized fusion welding process that leverages the interaction of electrical energy, thermal dynamics, metallurgy, and process control principles.

The process begins by directing a controlled stream of electrical current generated by a power source to a continuously fed consumable electrode. This electrode, constructed of a specific metal or alloy, generates a plasma arc when it encounters resistance (or impedance) from the workpiece, creating an area of high thermal energy.

The heat from this plasma arc is sufficient to induce a state of localized fusion within the workpiece's base metal and the electrode, melting them to create a molten weld pool. The nature and behavior of this molten pool, and hence the properties of the resultant weld, are heavily influenced by the complex metallurgical reactions happening at a microscopic level within this high-temperature zone.

The key feature of this process is the granular flux dispensed from a hopper and completely submerges the area of the plasma arc and the molten weld pool. This flux serves multiple crucial roles.

When the flux material encounters the extreme heat of the plasma arc, it undergoes a physical and chemical change. It produces a gaseous shield that protects the molten metal from potentially harmful atmospheric gases like oxygen and nitrogen, which could lead to weld defects such as porosity and brittleness. It also forms a layer of molten slag on the surface of the weld pool, further acting as a barrier to atmospheric contamination.

Once the molten metal in the weld pool cools and solidifies, it forms a weld bead, fusing the base metals. The slag, which also solidifies on cooling, forms a protective crust over the fresh weld, shielding it during the cooling process and preventing rapid heat loss, which can lead to thermal stresses and distortion.

After welding, the slag is chipped off, revealing a high-quality, full-penetration weld. This weld displays excellent structural and metallurgical properties, including uniformity and mechanical resilience, due to the SAW process's highly controlled and protected atmosphere.

The SAW process, therefore, offers high productivity, excellent weld quality, and deep weld penetration. It is particularly suited to industries requiring large amounts of welding, such as shipbuilding, pipeline, and heavy equipment manufacturing.