SAW · Submerged Arc Welding
Submerged Arc Welding
Submerged arc welding buries the arc under a blanket of granular flux, giving enormous deposition rates with no visible arc, no spatter and no arc flash — the process for heavy plate and long seams.
- SAW
- DCEP most commonly; DCEN for higher deposition; AC on multi-wire systems to control arc blow
- 300–1500 A, and higher on multi-wire installations
- Granular flux blanket, no gas
How submerged arc welding works
A continuously fed bare wire runs into a joint that has been covered ahead of it with granular flux. The arc strikes beneath that blanket, so it is never visible. Part of the flux melts to form a protective slag over the weld; the rest is vacuumed up and recycled. Because the flux blanket contains the heat and the arc, current densities far beyond any open-arc process become practical.
At a glance
| AWS designation | SAW — Submerged Arc Welding |
|---|---|
| Also called | SAW, Sub arc |
| Polarity | DCEP most commonly; DCEN for higher deposition; AC on multi-wire systems to control arc blow |
| Typical amperage | 300–1500 A, and higher on multi-wire installations |
| Typical voltage | 25–45 V |
| Positions | Flat and horizontal fillet only — the flux will not stay in place otherwise |
| Deposition rate | The highest of any common arc process, up to 100 lb/hr on multi-wire systems |
| Shielding | Granular flux blanket, no gas |
| Skill level | Mechanised or automatic; the skill is in setup and procedure rather than torch handling |
Machine configurations
| Mode | Description | Typical use |
|---|---|---|
| Single wire DCEP | The standard configuration. Deep penetration and good bead shape for most plate work. | General heavy plate and vessel seams |
| Single wire DCEN | Higher deposition rate with shallower penetration — used for cladding and build-up. | Surfacing and overlay |
| Tandem and multi-wire | Two or more wires in line, often with the lead wire on DC and the trail wires on AC to manage arc blow. Used for pipe mills and heavy vessel seams. | Very high production seam welding |
Shielding gas selection
| Gas | Used for | Notes |
|---|---|---|
| None — granular flux | All SAW | Fluxes are classified as fused, bonded or agglomerated. Bonded fluxes can carry alloying elements; fused fluxes cannot but resist moisture better. |
Starting settings
Starting points only — every machine, joint and position shifts them. Adjust by arc sound and bead profile.
| Wire | Amps | Volts | Travel | Use |
|---|---|---|---|---|
| 5/64 in (2.0 mm) | 300–500 | 26–32 | 14–24 ipm | Thin plate, fillets |
| 3/32 in (2.4 mm) | 350–600 | 27–34 | 12–22 ipm | General plate |
| 1/8 in (3.2 mm) | 450–800 | 28–36 | 10–20 ipm | Heavy plate |
| 5/32 in (4.0 mm) | 600–1000 | 30–38 | 8–18 ipm | Very heavy sections |
| 3/16 in (4.8 mm) | 700–1200 | 32–40 | 8–16 ipm | Vessel and pipe mill seams |
Advantages
- Deposition rates far beyond any open-arc process
- No arc flash, no spatter and very little fume at the operator's position
- Deep penetration, so thick joints need less preparation
- Highly repeatable weld quality on long seams
- Unused flux is recovered and reused
Limitations
- Flat and horizontal fillet positions only
- The arc cannot be seen, so the operator relies on instruments and procedure
- Equipment is large and not portable
- Only practical on long, regular seams — not for short or intricate welds
- Flux must be kept dry, and damp flux causes porosity and hydrogen cracking
Where it is used
- Pressure vessel longitudinal and circumferential seams
- Pipe mill seam welding
- Shipbuilding panel lines
- Structural beam and girder fabrication
- Corrosion-resistant cladding on heavy plate
Submerged Arc Welding — common questions
Why is it called submerged arc welding?
The arc burns beneath a blanket of granular flux and is never visible. The flux submerges the arc, which is what eliminates arc flash, spatter and most of the fume.
Can submerged arc weld out of position?
No. The granular flux is held in place only by gravity, so the process is limited to the flat position and horizontal fillets. Parts are positioned or rotated to suit.
How fast is submerged arc welding?
A single wire typically deposits 15 to 30 pounds per hour, and multi-wire installations reach 100 pounds per hour or more. That is several times what a skilled welder achieves with flux-cored wire.
Does SAW flux need to be dried?
Yes. Flux absorbs moisture, and moisture in the flux means hydrogen in the weld. Fluxes are held in heated hoppers and rebaked per the manufacturer's instructions when exposed.
What is the difference between fused and bonded SAW flux?
Fused flux is melted and crushed, is chemically homogeneous and resists moisture well, but cannot carry alloying additions because they would oxidise. Bonded flux is agglomerated at lower temperature, so it can carry deoxidisers and alloys, but it picks up moisture more readily.