Submerged Arc Welding | Definition, Principle, and Application

Definition :

It is an arc welding process where in coalescence is produced by heating with an electric arc or arcs set up between a bare metal electrode/electrodes and the job. The arc, end of the electrode and molten pool remain completely hidden and are invisible being submerged under a blanket of granular material (flux). The continuously fed bare metal electrode melts and acts are filler rod. No pressure is applied for welding purposes.

Principle :

In submerged arc welding process, instead of a flux covered electrode, granular flux and a bare (or copper coated) electrode is used. Arc between the electrode and job is the heat source and remains buried under the flux The flux serves as a shield and protects the molten weld pool from atmospheric contamination. The process may be semi-automatic or automatic.

Submerged Arc Welding Operation

Advantages :

  • Molten flux provides very suitable conditions for high current to flow. Great intensities of heat can be generated and kept concentrated to weld thicker sections with deep penetration.
Weld backing Technique
  • Because of high heat concentration, considerably higher welding specs can be used.
  • Because of high heat concentration and faster welding speeds, weld distortion is much less.
  • High metal deposition rates can be achieved. Single pass welds can be made in thick plates with normal equipment.
  • Welding is carried out without sparks, smoke, flash or spatter.
  • Weld metal deposited possesses uniformity, good ductility, corrosion resistance and good impact strength.
  • Very neat appearance and smooth weld shapes can be got.
  • The submerged-arc process can be used for welding in exposed areas with relatively high winds.
  • Practically, no edge preparation is necessary for materials under 12 mm in thickness.

Disadvantages :

  • Since the operator cannot see the welding being carried out, he cannot judge accurately the progress of welding. Therefore, accessories like jigs, fixtures, pointers, light beam focussing devices or roller guides may be used to ensure proper welding at the joint.
  • The flux needs preplacing of the same on the joint which is not always possible.
  • The process is limited to welding in flat position and on metal more than 4.8 mm thick. In small thicknesses burn through is likely to occur.
  • The process requires edge preparation and accurate fit up on the joint. Otherwise the flux may spill through the gap and arc may burn the work piece edges.
  • Flux is subject to contamination that may cause weld porosity.
  • Weld metal chemistry is difficult to control. A change in welding variables especially when using alloyed fluxes may affect weld metal com position adversely.
  • Cast iron, Al alloys, Mg alloys, Pb and Zn cannot by welded by this process.

Application :

  • Fabrication of pipes, pen-stocks, pressure vessels, boilers, structural shapes, rotary kiln, rail road, and earth moving equipment, cranes, bridge girders and under structure of railway coaches and locomotives.
  • Automotive, Aviation, ship-building and nuclear power industry.
  • Rebuilding of worn out parts and depositing wear resisting alloys. Hard facing of tractor rollers and idlers, and crane pulleys.
  • For welding metals like mild steel, medium and high tensile low alloy steels.

References : A Textook of Welding Technology by O. P. Khanna

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