What Is Submerged Arc Welding? SAW Process, Flux Types, and Uses

Submerged arc welding (SAW) is a wire-fed process commonly used for long, repeatable welds. The arc forms under a layer of granular flux, so you cannot see the arc or weld pool. If you know MIG or stick welding, that can feel strange at first.

SAW starts making sense when the weld is measured in feet rather than inches. That is why it is common on pipe, pressure vessels, ship panels, and other large fabrications. On a long joint, the setup can pay for itself. On a short repair, it usually will not.

This guide explains how the SAW process works, what the flux does, and when to use it.

Before Choosing SAW, Remember:

• Granular flux covers the arc and weld pool, so no external shielding gas is normally needed.

• Continuous wire feed suits long, repeatable seams.

• SAW works best when the weld stays flat or the work rotates.

What Is Submerged Arc Welding?

Submerged arc welding (SAW), also called sub arc welding, forms an arc between a continuously fed electrode and the workpiece. The arc melts the wire and joint edges to create a weld pool. Some flux melts into slag, while the rest remains loose over the joint.

“Submerged” describes the covered arc. It does not mean underwater welding.

Most SAW systems use solid wire. Metal-cored wire and strip electrodes are used for special welding and cladding jobs. The operator monitors joint tracking, controls flux flow, and checks weld quality.

How Does the SAW Process Work?

Once the joint and machine are ready, SAW runs in a steady cycle:

1. Flux and wire feed: The system spreads flux over the joint. At the same time, it feeds wire toward the workpiece.

2. Arc and weld pool: The arc starts under the flux. It melts the wire and base metal to form a weld pool.

3. Shielding and slag: Part of the flux melts around the pool. It blocks air, steadies the arc, and forms liquid slag.

4. Cooling and inspection: The metal cools under the slag. The slag is then removed so the bead can be checked.

Most systems move the welding head along the joint. For pipe welding, the pipe may turn while the head stays still. Both methods support automated welding .

What Equipment and Settings Does SAW Use?

A SAW system has five main parts: a power source, wire feeder, welding head, flux hopper, and carriage or positioner. The feeder keeps the wire moving, the hopper covers the joint with flux, and the carriage moves the head along the seam. On pipe or tanks, a positioner may turn the work instead.

Larger systems may add flux recovery, joint tracking, or multiple electrodes. Once the machine is moving at a steady rate, the settings control the bead:

Current: More current usually melts the wire faster and increases penetration.

Voltage: More voltage normally makes the bead wider and flatter.

Travel speed: Faster travel puts less heat into each inch of the joint and makes a smaller bead.

Stick-out: A longer electrode extension can increase wire melt-off and deposition rate, but excessive extension may affect arc stability and weld penetration.

Polarity also changes the result. DCEP is often used when deeper penetration is needed. DCEN can increase wire melt-off with less penetration, while AC helps reduce arc blow. Do not treat these trends as a settings chart. Use the welding procedure specification (WPS) and the wire-flux data sheet for the actual values.

What Does SAW Flux Do?

SAW flux does much more than cover the arc. While the weld is hot, the flux keeps air away and helps the arc burn smoothly. As the weld moves forward, some flux melts, shapes the bead, and forms a layer of slag over the cooling metal. Certain fluxes can also help clean the weld pool or add alloying elements.

This is why the wire and flux must be chosen as a pair. Change the wire or flux, and the result may change even when the machine settings stay the same. The bead may look different, the slag may be harder to remove, and the weld may not have the same strength or toughness.

Main Types of Submerged Arc Welding Flux

SAW flux names describe two things: how the flux is made and how it affects the weld metal. A product may carry one label from each group. For example, it can be both agglomerated and neutral.

By Manufacturing Method

Fused flux is melted, cooled, crushed, and screened. It generally absorbs less moisture but offers fewer formulation choices.

Agglomerated flux is made from powdered ingredients formed into grains and baked. It allows more control over the formula but must be kept dry.

Mixed flux is a manufacturer-controlled blend of finished fluxes. Do not make your own mixture from leftovers.

By Effect on Weld Chemistry

Neutral flux adds little manganese or silicon compared with active flux. It is commonly used for multipass welds where consistent chemistry matters.

Active flux contributes more manganese or silicon and is often used for fast single-pass or limited-pass welding. Voltage changes can affect the result.

Alloying flux adds selected elements for cladding, surfacing, or hardfacing.

Advantages and Limitations of SAW

SAW earns its place on long production welds, but it is not the right process for every job.

The hidden weld pool is the main challenge. If the wire moves off the joint, the error may continue before it appears in the finished bead. Clean fit-up and reliable joint tracking are essential.

What Metals and Joint Types Can SAW Weld?

SAW mainly joins carbon steel and low-alloy steel. Matching wire-flux combinations are also available for stainless steel and some nickel alloys.

Typical joints include flat butt welds, horizontal fillets, and long straight or circular seams. A positioner can rotate round parts to keep the weld near the top.

Gravity is the practical limit. If the part cannot lie flat or rotate, another process is usually the better choice.

Applications of SAW

SAW is widely used to build large steel products.

• Pipe welding : Straight or spiral seams on large pipe.

• Pressure equipment: Boilers and pressure vessels.

• Shipbuilding: Panels, decks, and hulls.

• Structural steel: Bridges, heavy beams, and columns.

• Energy projects: Wind towers, offshore structures, and storage tanks.

SAW vs. MIG, Flux Core, and Stick Welding

Here is how SAW compares with MIG, flux core, and stick welding in everyday use.

Common SAW Defects and First Checks

A defect may have more than one cause. Check one area at a time, record each change, and keep all settings within the WPS.

Submerged Arc Welding Safety Tips

The arc is hidden, but the danger is not. Wear eye protection, gloves, safety footwear, and flame-resistant clothing. An exposed start or shallow flux bed can still expose workers to arc radiation.

Control fumes and flux dust with ventilation. Inspect cables and moving equipment, keep combustibles away, and treat slag as hot. Never enter a vessel without an approved confined-space plan and atmospheric testing.

Conclusion

For jobs that can be set up once and welded continuously, SAW is worth a close look. Long tank seams and pipe sections give the process room to work. The head keeps moving, stops are few, and weld metal goes down fast.

Frequent repositioning, changing joint directions, and short repairs reduce the advantages of SAW. MIG, flux core, or stick will often finish those jobs sooner.

Keep one rule in mind: use SAW when the job lets the machine keep moving.

🧐 Frequently Asked Questions

1. Does submerged arc welding need shielding gas?

No. In normal SAW, granular flux covers the arc and weld pool, provides shielding, and forms slag over the finished weld. External shielding gas is not normally required.

2. How is SAW different from flux-core welding?

SAW uses loose granular flux outside the electrode and is usually mechanized. Flux-cored arc welding uses tubular wire with flux inside it. FCAW may be self-shielded or require external shielding gas.

3. Can SAW flux be reused?

Yes, when the flux manufacturer and welding procedure allow it. Unmelted flux must remain clean, dry, and properly screened before reuse. Chipped slag should never be mixed back in with unused flux.

4. Can SAW weld thin metal?

Yes, but it requires a carefully developed procedure. SAW normally uses high current and heat input, which can burn through or distort thin sheet. For that reason, the process is more commonly used on thicker material.

5. Is SAW suitable for a home workshop?

Usually not. The equipment, flux handling, joint positioning, and setup time make SAW better suited to industrial production. MIG, flux core, or stick welding is more practical for most home repairs and small projects.

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