Submerged Arc Welding

Definition

Submerged Arc Welding (SAW) is an arc welding process where the heat required for welding is generated by an electric arc produced between a bare consumable electrode wire and the workpiece. The arc, the tip of the electrode, and the molten weld pool are "submerged" under a blanket of granular, fusible flux, which protects the weld from atmospheric contamination.

Main Content

1. The Flux Blanket

• The flux is a granular material that provides essential protection against oxidation and nitrogen absorption from the air.
• As the arc melts the flux, it forms a slag that covers the molten metal, slowing the cooling rate and improving the mechanical properties of the weld.

2. The Consumable Electrode

• SAW typically uses a continuous solid wire or metal-cored electrode that is fed automatically into the weld zone.
• Because the process is automated or semi-automated, it allows for high deposition rates and consistent weld quality compared to manual methods.

3. Current and Depth

• The process is characterized by deep penetration into the base metal, which is achieved through high current densities.
• Due to the "submerged" nature of the arc, there is no visible light, sparks, or smoke, making it a "clean" process for the operator, though specialized ventilation is still required.

       Wire Feed Reel
            |
            v
      [Contact Tube]
            |
      ( Flux Hopper )
            |
     [ Granular Flux ]
            |
    ___________________
   |   (Electric Arc)  | <--- Submerged Zone
   |___________________|
    [   Weld Metal    ]

Working / Process

1. Preparation and Setup

• The joint edges are cleaned of rust, oil, or scale to prevent porosity.
• The granular flux is deposited along the joint path just ahead of the advancing arc to ensure full coverage.

2. Arc Initiation and Welding

• The power source is activated, and the electrode wire is fed into the flux. An arc is struck beneath the flux blanket.
• The intense heat melts the tip of the wire and the edges of the base metal, creating a molten pool of metal and liquid slag.

3. Slag Removal and Completion

• As the welding head moves along the joint, the flux solidifies into a brittle slag layer on top of the weld bead.
• Once the weld has cooled, the excess flux is vacuumed for reuse, and the slag is chipped away to reveal the finished, smooth weld bead.

Advantages / Applications

• High Deposition Rates: SAW is significantly faster than manual welding methods, making it ideal for thick plates.
• Deep Penetration: The process provides excellent fusion, often requiring less edge preparation (like V-grooves) for thicker sections.
• Industrial Applications: Widely used in shipbuilding, manufacturing of pressure vessels, structural steel beams, and large-diameter pipe welding.

Summary

Submerged Arc Welding is a high-productivity automated welding process that uses a granular flux to protect the molten weld pool from the atmosphere. It is defined by its deep penetration and ability to produce high-quality, long-run welds in heavy industrial settings. Key terms to remember include: Flux (protective granular coating), Consumable Electrode (the filler wire), and Slag (the solidified protective layer).