Submerged Arc Welding buries the arc under a blanket of granular flux. The arc is invisible, the deposition is enormous, and the welds are code-grade clean — the workhorse of heavy fabrication.
SAW feeds a bare wire electrode continuously through a contact tip into a joint covered by granular flux. The arc burns beneath the flux, which melts into slag over the weld and completely blocks light, spatter, and air. Flux shields better than any gas — so currents climb far beyond what MIG can carry.
The process is mechanized: a tractor or fixed head rides the joint while the operator monitors voltage, travel, and flux. Deposition runs 10–25 lb/hr single-wire, and multiple electrodes push it far beyond. SAW is flat-position only, which suits plate fabrication, pressure vessels, and pipe mills perfectly.
EM12K wire, neutral flux — the everyday carbon steel setup.
| Plate | Wire | Amps | Volts | Travel in/min | Flux depth |
|---|---|---|---|---|---|
| 1/4 in | 3/32 in | 350–450 | 28–30 | 25–35 | 1–1.5 in |
| 1/2 in | 3/32 in | 450–600 | 29–31 | 20–30 | 1–1.5 in |
| 3/4 in | 1/8 in | 550–750 | 30–32 | 18–25 | 1.25–1.75 in |
| 1 in | 1/8 in | 650–850 | 31–33 | 15–22 | 1.25–1.75 in |
| 1.5 in | 5/32 in | 800–1000 | 32–34 | 12–18 | 1.5–2 in |
| Wire | Flux | Service |
|---|---|---|
| EM12K | F7A2 neutral | General structural steel |
| EH14 | F7A4 active | Higher strength, thicker plate |
| EM13K | F6A2 | Fillets and fast travel |
| ER308L | SS flux | Stainless cladding and joins |
Flux names like F7A2-EM12K encode strength, condition, and the paired wire. Neutral fluxes keep chemistry stable; active fluxes add alloy.
600–1500 A constant-voltage DC or AC source. One machine feeds the whole cell.
Browse power sources →Heavy-duty feeder with two or four drive rolls for 3/32–5/32 in wire on 60 lb coils.
Browse feeders →Carriage that rides the plate or rail, holding the head, hopper, and flux nozzle.
Browse automation →Vacuum that reclaims unfused flux and screens out slag — reusing flux cuts consumable cost.
Keeps the joint flat and feeds it to the head — the real productivity secret of SAW.
Browse positioners →Copper backing bars and clamps control root penetration on open joints.
No arc flash, but flux and heat fly — dark lens, gloves, long sleeves, respirator for flux dust.
Browse PPE →Preheat torches and temp sticks for thick plate — heat input must match the code.
SAW is a flat-position process by design — the flux blanket is gravity-bound. The work comes to the weld.
The natural home of SAW — full current, full deposition, perfect puddle control.
Tee and lap joints laid with the head tilted slightly — the other standard SAW joint.
Uphill up to ~10–20° increases penetration for thick roots; downhill speeds thin plate.
Pipe mills rotate the pipe under a fixed head — the joint is always flat to the arc.
Mechanized doesn't mean automatic — the operator sets the geometry that makes or breaks the weld.
Straight pass at constant travel — the bread and butter of SAW fills and fillets.
Oscillate the head side to side up to 3 in wide for deep groove fills in fewer passes.
Even bead layers, each cleaning the previous — slag-free between passes is non-negotiable.
Two electrodes in one joint — lead wire carries current, trail wire shapes the bead. Double speed.
Wide flat stringers lay stainless or hardfacing overlay on carbon steel — pressure vessels and rolls.
Stick-out ~10 wire diameters; keep the nozzle clear of slag buildup for a stable arc.
SAW defects are a four-way argument between amps, volts, travel, and flux. Read the bead, change one.
Appearance
Glassy slag trapped inside the weld or between passes.
Causes
High voltage, fast travel, thick flux, or dirty interpass.
Prevention
Lower volts, slow down, right flux depth, clean between passes.
Appearance
Holes from the surface down — gas bubbles that never escaped.
Causes
Damp flux, rusted plate, or flux too deep for gas to vent.
Prevention
Dry flux, clean metal, correct flux depth.
Appearance
A straight crack down the middle of a wide bead.
Causes
Concave bead cross-section plus high restraint.
Prevention
Lower voltage, slower travel, wider bead with a flat crown.
Appearance
Bead sits on the bevel face with a dark unfused line at the toe.
Causes
Low amps or travel faster than the puddle can wash the walls.
Prevention
Raise amps, slow travel, center the arc in the groove.
Appearance
Groove melted along the bead toe, thinning the plate.
Causes
Too many amps or too much voltage for the travel speed.
Prevention
Balance volts/amps to travel — add filler or adjust speed.
Appearance
Molten metal fell through the root — holes on the back side.
Causes
High amps on a thin root face or wide gap.
Prevention
Root face and backing bar, lower amps on the first pass.
Appearance
A ridged, humped bead — the puddle couldn't keep up.
Causes
Travel too fast for the deposition rate.
Prevention
Slow the travel or raise the amps to match.
Appearance
Visible arc flash — the flux cover broke — leaving marks and surface porosity.
Causes
Flux too shallow or a draft blowing the blanket aside.
Prevention
Deep enough flux and shield the arc from wind.
The documents that govern SAW wire, flux, and qualification.
| Standard | Covers |
|---|---|
| AWS A5.17 | Carbon steel wire and flux for SAW — the F7X-EM12K system |
| AWS A5.23 | Low-alloy steel wire and flux |
| AWS D1.1 | Structural steel — SAW procedures, preheat, and inspection |
| ASME Section IX | Procedure and welder qualification for pressure equipment |
| API 1104 | Pipeline welding including SAW line pipe seams |
| ISO 14171 | International standard for wire and flux combinations |
| AWS B2.1 | Procedure qualification of welding processes |
| ASME VIII | Pressure vessel construction rules that lean on SAW |
All-in-one machine settings helper for a fast SAW starting point.
Volts × amps × 60 ÷ travel — the number codes audit on thick plate.
Match wire class and flux to base metal and strength grade.
Amps by wire size and plate thickness for clean penetration.
Which wire, amps, and passes fit 1/4 in vs 2 in plate.
See tractor setup, flux handling, and bead profiles on real plate.
Watch the technique sections — tractor setup, flux control, and multi-pass fills — on real plate.
Watch VideosA shop-floor cheat sheet with the parameter table, wire/flux chart, and defect guide.
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