How Does Submerged Arc Welding (SAW) Works?

Submerged arc welding SAW is a welding techniques that involve the formation of an arc between a continuously fed electrode and the workpiece to be joined. The SAW process creates a flux in the form of a blanket of powder that surrounds and covers the arc serving as a shield to the weld. This is also used to add alloying elements to the weld pool.

The SAW welding techniques offer an extremely high metal deposition rate, high weld accuracy, fusion quality, a low rate of weld discontinuities, and depth of penetration. MIG and Flux-cored welding offer similar qualities, but they can’t match the deposition rate of submerged arc welding.

The difference between SAW and SMAW is that the SAW process uses an external flux that is delivered at the arcing area to protect or act as a shield to the weld. On the other hand, the flux-coated electrode used in SMAW helps to shield the welding process from any atmospheric interaction.

Well, in this reading, we’ll explore what SAW is, its applications, parts, equipment, diagram, and how it works. We’ll also explore the advantages and disadvantages of submerged arc welding.

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What is submerged arc welding (SAW)?

Submerged arc welding is another type of arc welding process that uses a continuously fed consumable tubular electrode. It can be operated in the automatic or mechanized mode. It can also be operated on semi-automatic (hand-held) SAW guns with the delivery of pressurized or gravity flux fed. This process is not suitable for flat or horizontal filler welding positions the horizontal position has been done with a special arrangement in order to support the flux.

In this welding process, the arc zone and weld pool are protected from atmospheric contamination, due to the blanket of granular flux consisting of lime, silicon, manganese oxide, calcium fluoride, and some other compounds. The molten flux becomes conductive and creates a current between the electrodes and the base metal. The thick flux layer covers the metal completely, preventing sparks and spatters, and supporting the intense ultraviolet radiation and fumes that are part of the welding process.

SAW was the first patent in the year 1935 and covered an electric arc beneath a bed of granulated flux. It was originally developed by Jones, Kennedy, and Rothermund.

Applications of SAW

The Submerged Arc Welding (SAW) process is a versatile welding method suitable for various industries, including structural and vessel construction, low alloy steels, stainless steels, nickel-based alloys, and surfacing applications. It is particularly suitable for welding pressure vessels like boilers, achieving a smooth weld pool from the continuously fed electrode.

SAW is also suitable for shipbuilding, as it can be performed both indoors and outdoors, creating long, straight welds for heavy metals in ship parts. It is also suitable for automotive and military industries due to its speed and efficiency, offering the option to have multiple or single-pass welds based on the metal’s thickness.

Lastly, the SAW process allows deep weld penetration, making it attractive for the railway industry. Overall, SAW is a versatile and efficient welding method that offers numerous applications in various industries.

Related: How Does ElectroSlag Welding (ESW) Works?

Parts and Equipment of SAW

SMAW is a submerged arc welding process that utilizes a welding head, flux hopper, and electrode to create a weld. The welding head supplies filler and flux metal to the welding joint, while the flux hopper stores and controls flux deposition. The granulated flux protects the weld from atmospheric contamination, cleans the metal, and modifies its chemical contamination.

The electrode, which is typically 1.6mm to 6mm thick, is used to feed the filler material to the welding joint. This process is a significant advancement in arc welding technology. Well, let’s further explore the parts and equipment.

Wire Electrode

A wire electrode is a crucial component in welding systems, feeding the wire into the weld. The wire electrode, typically between 1.6mm and 6mm thick, can be solid, twisted, or cored and can be operated using various power sources.

Modified wire electrodes and systems may be needed to achieve the desired weld profile, such as twin-wire, multiple wires, single wire with hot/cold addition, metal powder additive, or tubular wire. Additional wires are used to add more deposition to the weld pool.

Flux

Flux is a crucial component in various applications, including bonded flux, molten flux, and granular flux. Granular flux, composed of oxides like aluminium, calcium, magnesium, manganese, silicon, titanium, and zirconium, is suitable for electrodes due to its chemical reaction.

Bonded flux, produced by drying and baking the composition, can contain alloying elements and offer flexibility and protection against rust. Fused flux, produced by melting the composition in an electric furnace, forms homogenous particles, making it ideal for consistent welds along the bead.

Power Source

Submerged arc welding (SAW) utilizes multiple electrode systems to manipulate weld results. These systems allow wires to be run at different power sources, allowing for better control of bead profile and penetration. There are products that offers stability and penetration, and also increases deposition rates. AC is the middle ground, achieving a balance between these two.

Diagram of Submerged Arc Welding (SAW)

Submerge Arc Welding  SAW

How Does Submerged Arc Welding (SAW) Works?

Submerged-arc welding (SAW) is a versatile arc welding process that creates an arc between a continuously fed electrode and the workpiece. A powdered flux blanket generates a protective gas shield and slag, protecting the weld zone. The electrode can be a solid or cored wire or a strip made from sintered material.

The flux can be formed by fusing constituents to form a glassy slag or by agglomerating the constituents using a binder and corning process. The chemical nature and size distribution of the flux help determine arc stability and the mechanical properties of the weld metal and the shape of the bead.

SAW is typically operated as a mechanized process, with factors such as welding current, arc voltage, and travel speed affecting bead shape, depth of penetration, and chemical composition. The operator relies heavily on the parameter setting and positioning of the filler wire.

Variants of SAW include using two or more wires, adding chopped wire to the joint, and using metal powder additions. Feeding a small diameter non-conducting wire into the leading edge of the weld pool can increase deposition rates by up to 20%.

Related: How Does Flux-Cored Arc Welding (FCAW) Works?

Advantages and Disadvantages of Submerged Arc Welding

Submerged arc welding (SAW) offers numerous advantages such as strong, sound welds, minimal welding fume, and arc light, suitable for both indoor and outdoor work, less distortion, deep weld penetration, minimal edge preparation, high deposition rates, and the ability to weld thick materials.

However, it has some disadvantages, such as its limited use in flat or horizontal welding positions, limited use for ferrous metals like steel and stainless steel, and its limitations in long straight seams or rotated pipes and vessels.

Additionally, it requires backing strips for proper penetration and is limited to high-thickness materials. Despite these disadvantages, SAW offers advantages such as automation, less smoke, edge training, and no chance for oxide sparks due to its submerged nature.

However, it also has disadvantages such as incomplete processes for certain metals, tedious flux usage, potential health issues due to flux, and the need for slag removal after welding.

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