What is submerged arc welding? An easy guide

Submerged arc welding produces exceptionally clean, spatter-free welds on thick steel. For heavy fabrication work, this welding process continues to deliver reliable results that newer methods struggle to match.

What is submerged arc welding (SAW)?

Submerged arc welding (SAW) joins metal pieces together by creating an electric arc that stays completely hidden under a blanket of granular flux material.

The process works by feeding a continuous metal electrode through a layer of flux powder. Electricity flows through the electrode, generating intense heat that melts both the base metal and the filler wire. The flux powder melts simultaneously, forming a protective gas shield and slag layer around the molten weld pool. Once cooled, the result is a strong, clean joint with minimal defects.

Submerged arc welding is versatile and can join mild steel, low alloy, and stainless steel.

It is commonly used to weld boiler shells, pressure vessels, shipbuilding components, heavy construction equipment, and pipelines.

How does submerged arc welding work?

Submerged arc welding uses an arc between a continuously fed bare metal electrode and the workpiece to melt the metals at the joint.

To understand the process, break it down into several parts:

1. The welding machine: This machine feeds a metal wire and delivers flux powder onto the work area. The wire carries electricity that creates the heat to melt everything.
2. The flux powder: This material consists of granular particles that completely cover the welding area. When it gets hot, it melts and creates gases that protect the weld.
3. The slag layer: After welding, the melted flux turns into a hard crust on top of the finished weld. You can chip this off easily with a hammer, and underneath you'll find a smooth, clean weld.

You can vacuum the flux that doesn't melt and use it again.

Advantages of using the submerged arc welding process

SAW has several advantages over other welding methods for certain jobs.

• No shielding gas is necessary: Most welding uses expensive shielding gases to protect the weld from air. SAW makes its own protective gases from the flux, eliminating the need to purchase, store, or transport gas cylinders.
  
  
• No limits to welding depth: SAW can weld through several inches of metal in a single pass. Other welding methods need to make many passes to join thick pieces. The weld pool is submerged under the flux blanket, so atmospheric conditions do not affect it.
  
  
• Strong welds: The flux creates very clean welds with no air bubbles or weak spots. These welds are often stronger than the original metal pieces. Many industries require this level of quality for safety.
  
  
• Clean process and least post-weld cleaning: Traditional welding methods generate significant spatter that adheres to nearby surfaces. SAW makes almost no mess. The slag peels off cleanly, leaving a smooth surface that needs very little grinding or cleaning.

Disadvantages of using the submerged arc welding

Although SAW has many advantages, it also has some limitations.

• Weld flat or slightly tilted: You can only use it when the workpiece lies flat or at a slight incline. The flux powder would fall off if you tried to weld straight up or upside down. For round pipes, you have to keep rotating the pipe so the welding stays on top.
  
  
• High investment to get started: SAW systems require significant upfront capital investment compared to basic welding equipment. You need flux handling systems, electrical equipment, and often conveyor systems to move the workpieces. Small shops often find the initial investment challenging.
  
  
• Visibility: Since everything happens under the flux, welders can't watch the weld form like they can with other methods. If something goes wrong, they might not notice until the weld is complete.

Where is submerged arc welding used?

Submerged arc welding is used in many heavy industries where thick materials need to be joined together. Some of the most common applications are:

• Steel plate fabrication for shipbuilding
• Pressure vessel manufacturing, including storage tanks and boilers
• Heavy machinery production, e.g., cranes, mining equipment, and heavy-duty vehicles
• Building wind turbines
• Oil and gas pipeline construction
• Fabricating wind towers
• Manufacturing equipment for construction and earthmoving, including bulldozers and excavators
• Industrial fan and turbine construction

Can submerged arc welding be automated?

Yes, in fact, most SAW operations today use robotic and automated systems. SAW is well-suited for automation for several technical reasons:

• The process requires no external shielding gas, simplifying robotic control systems. Robots only manage the welding head movement and flux delivery.
• SAW achieves deposition rates of approximately 8 to 45+ kg per hour. Robotic systems maintain this maximum throughput continuously with consistent quality. Manual welding cannot sustain these rates over extended production runs.
• The welding heads are simple, and automated welding equipment can easily manipulate them. The flux and wire are fed through the welding head, which requires only basic motion control.
• Submerged arc welding doesn’t need tight joint preparation or fit-up. This makes it easier for automated welding equipment to access the joint and deposit weld metal.
• SAW operations typically involve long, repetitive weld seams across large workpieces. Automated welding equipment can consistently deposit extensive weld lengths without variation in quality.

What metals is SAW most useful for?

SAW is mostly used to weld:

• Low and medium-carbon steel
• Low-alloy steel
• Stainless steel

The high deposition rates possible with submerged arc welding make it extremely well-suited for welding thick sheets of metal.

Recent advances with flux-cored wires and tubular electrodes have extended SAW applications to copper alloys and nickel alloys. You can’t use it to weld aluminum, magnesium, zinc alloys, or cast iron.

Should you choose submerged arc welding?

SAW delivers optimal results for specific applications. Choose it when you need:

• Strong welds on thick steel pieces
• Fast straight welding for big projects
• Consistent, repeatable weld quality
• Minimal cleanup and finishing work

Summing up

Submerged arc welding has earned its place in heavy industry by making strong, clean welds on thick steel pieces. While it can't do everything that more flexible welding methods can do, SAW excels in its specialty areas.

With its high deposition rates, deep penetration, and automated capabilities, SAW helps manufacture everything from ships to pipelines to construction equipment.

For operations centered on large-scale industrial fabrication, automating submerged arc welding delivers measurable productivity gains and quality improvements.

The initial capital investment is significant, but automated SAW systems typically achieve positive ROI through increased throughput and reduced labor costs.

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FAQs

1. What are the 4 types of arc welding?

The four main types of arc welding are gas metal arc welding (GMAW/MIG), gas tungsten arc welding (GTAW/TIG), shielded metal arc welding (SMAW/stick), and flux cored arc welding (FCAW). MIG and TIG are the most common methods in modern fabrication shops, while stick welding remains popular for fieldwork and repairs.

2. Is submerged arc welding automatic or semi-automatic?

Submerged arc welding can be both automatic and semi-automatic. SAW typically operates as a fully mechanized or automatic process for production environments, but semi-automatic hand-held SAW guns are also available with pressurized or gravity flux feed delivery systems.

3. Is submerged arc welding AC or DC?

Submerged arc welding uses both AC and DC current, depending on the application. Direct current is most common for single-arc welding, while AC is primarily used for automatic methods and multiple-electrode systems to reduce arc blow and magnetic interference.

4. When should you use submerged arc welding?

Use submerged arc welding for thick materials ranging from 1/2 inch to 5 inches, long continuous welds, and high-volume production work. SAW is ideal for shipbuilding, pressure vessels, pipelines, and structural steel fabrication where you need deep penetration and high deposition rates.

5. Does submerged arc welding use flux?

Yes, submerged arc welding uses granular flux that completely covers the welding arc. The flux shields the molten weld from atmospheric contamination, stabilizes the arc, and forms a protective slag layer over the finished weld. Unused flux can be recycled and reused for cost efficiency.