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Submerged arc welding

From Academic Kids

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A submerged arc welder used for training.
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Close-up view of the control panel.

Submerged Arc Welding (SAW) is a common arc welding process. It requires a continuously fed consumable solid or tubular (metal cored) electrode. The molten weld and the arc zone are protected from atmospheric contamination by being “submerged” under a blanket of granular fusible flux. When molten, the flux becomes conductive, and provides a current path between the electrode and the work.

SAW is normally operated in the automatic or mechanized mode, however, semi-automatic (hand-held) SAW guns with pressurized or gravity flux feed delivery are available. The process is normally limited to the 1F, 1G, or the 2F positions (although 2G position welds have been done with a special arrangement to support the flux). Deposition rates approaching 100 lb/h (45 kg/h) have been reported — this compares to ~10 lb/h (5 kg/h) (max) for shielded metal arc welding. Currents ranging from 200 to 1500 A are commonly used; currents of up to 5000 A have been used (multiple arcs).

Single or multiple (2 to 5) electrode wire variations of the process exist SAW strip-cladding utilizes a flat strip electrode (e.g. 60 mm wide x 0.5 mm thick). DC or AC power can be utilized, and combinations of DC and AC are common on multiple electrode systems. Constant Voltage welding power supplies are most commonly used, however Constant Current systems in combination with a voltage sensing wire-feeder are available.


Contents

1 Additional reading

Material applications

  • Carbon steels (structural and vessel construction);
  • Low lloy steels;
  • Stainless Steels;
  • Nickel-based alloys;
  • Surfacing applications (wearfacing, build-up, and corrosion resistant overlay of steels).

Advantages of SAW

  • High deposition rates (over 100 lb/h (45 kg/h) have been reported);
  • High operating factors in mechanized applications;
  • Deep weld penetration;
  • Sound welds are readily made (with good process design and control);
  • High speed welding of thin sheet steels at over 100 in/min (2.5 m/min) is possible;
  • Minimal welding fume or arc light is emitted.


Limitations of SAW

  • Limited to ferrous (steel or stainless steels) and some nickel based alloys;
  • Normally limited to the 1F, 1G, and 2F positions;
  • Normally limited to long straight seams or rotated pipes or vessels;
  • Requires relatively troublesome flux handling systems;
  • Flux and slag residue can present a health & safety issue;
  • Requires inter-pass and post weld slag removal.


Key SAW process variables

  • Wire Feed Speed (main factor in welding current control);
  • Arc Voltage;
  • Travel Speed;
  • Electrical Stick-Out (ESO) or Contact Tip to Work (CTTW);
  • Polarity and Current Type (AC or DC).

Other factors

  • Flux depth/width;
  • Flux and electrode classification and type;
  • Electrode wire diameter;
  • Multiple electrode configurations.

Additional reading

American Welding Society, Welding Handbook, Vol 2 (9th ed.)

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