Shipbuilding is one of the most welding-intensive industries in the world. A single commercial vessel can require hundreds of thousands of weld passes — spanning hull plates, structural frames, piping systems, deck assemblies, and more. Each joint must be watertight, oil-tight, and structurally sound enough to withstand open-ocean conditions for decades.
Because no single welding process can handle every application aboard a ship, shipyards rely on a range of techniques — each selected based on material type, joint configuration, access constraints, and quality requirements. This guide breaks down the main types of welding used in the shipbuilding industry, how each process works, and where it’s applied.
Types of Welding in Shipbuilding: Quick Reference
| Welding Type | Process Category | Best Application | Key Advantage |
| SMAW (Stick) | Arc | Grillages, tanks, panels | Versatile; works in all positions |
| Submerged Arc | Arc | Long flat seams, heavy plates | High deposition; excellent joint purity |
| Stud Welding | Arc | Fastening studs/bolts to hull | Fast; no through-hole needed |
| TIG (GTAW) | Gas | Thin plates, precision joints | Clean weld; no spatter |
| MIG (GMAW) | Gas | Aluminum deckhouses, membrane tanks | High speed; continuous wire feed |
| Spot Welding | Resistance | Sheet metal assemblies | Cost-effective; no filler needed |
| Seam Welding | Resistance | Continuous watertight seams | Consistent; high-speed production |
| Projection Welding | Resistance | Multi-point contact joints | Energy-efficient; strong welds |
| Friction Stir | Specialized | Side shell joints, aluminum panels | Low heat input; minimal distortion |
| Laser Welding | Specialized | Precision hull components | Minimal deformation; high speed |
| Plasma Welding | Specialized | Extremely thin metals | Precise heat control |
| Thermit Welding | Specialized | Large steel forgings, stern frames | No external power needed |
| Orbital TIG | Automated | Pipes, tubes, cylindrical joints | Repeatable; code-quality welds |
Arc Welding Techniques
Arc welding is the foundation of shipbuilding fabrication. The process works by connecting a metal electrode to an electrical power source and bringing it close to the workpiece. The current jumps the gap between the electrode and the base metal, forming an intensely hot electric arc that melts both surfaces and fuses them together.
Because the arc is exposed to the atmosphere, shielding is critical — without it, oxygen and moisture contaminate the weld pool, producing porous, brittle joints. Shipyards use two main shielding approaches: inert gas shielding and slag shielding (flux). The most common arc welding processes in shipbuilding are:
Shielded Metal Arc Welding (SMAW) — Stick Welding
SMAW, commonly called stick welding, is the most widely used manual arc welding process in shipbuilding. A flux-coated electrode rod is held against the workpiece, and as the arc burns, the flux coating decomposes to generate a shielding gas and form a slag layer over the weld pool. This slag protects the molten metal from atmospheric contamination until it solidifies.
For shipbuilding applications, the most common electrode core material is mild steel. Electrode coatings typically include silicates, hydrocarbons, and mineral oxides — compounds that produce stable arcs and clean, well-protected welds.
SMAW is the preferred method for:
- Grillage fabrication (the structural grid supporting decks and bulkheads)
- Tank units and double-bottom structure
- Prefabricated panel assemblies
- Repair and maintenance welding throughout the vessel
Its versatility across positions (flat, horizontal, vertical, overhead) and its ability to work in field conditions make SMAW indispensable in shipyards worldwide.
Submerged Arc Welding (SAW)
Submerged arc welding is the high-productivity workhorse for long, straight weld seams on flat or slightly inclined surfaces. Unlike SMAW, the arc in SAW is completely buried under a layer of granulated flux deposited ahead of the electrode — which is why there’s no visible arc flash during operation.
The process works as follows:
- A hopper deposits a continuous layer of granulated flux along the weld joint
- A continuously fed wire electrode follows behind, driven by a motorized roller system with an adjustable feed rate
- The arc forms beneath the flux layer, providing complete isolation from the atmosphere
- Unused flux is recovered and recycled after welding
The result is exceptional arc consistency, deep penetration, high deposition rates, and superior joint purity — making SAW the go-to downhand welding process for heavy plate work in shipyards. It is commonly used for:
- Butt welds on deck plates and shell plating
- Longitudinal seams on large structural sections
- High-volume fabrication runs where automation is feasible
Stud Welding
Stud welding is a specialized arc process used when a bolt, stud, or threaded fastener must be permanently attached to a metal surface without drilling or through-holes. A stud is placed against the parent metal, a controlled arc melts both the stud base and the contact area, and the stud is then pressed into the melt under spring force. The electrical supply cuts off instantly as the stud seats, and the joint solidifies in milliseconds.
The combination of rapid arc time and full-face contact produces a strong, clean weld with no visible fastener on the opposite side of the plate. In shipbuilding, stud welding is used for:
- Fastening insulation panels to bulkheads
- Attaching timber flooring to deck plates
- Securing pipe hangers, cable trays, and outfitting brackets
- Any application requiring a surface-mounted fastener without through-bolting
Gas Welding Techniques
Gas shielded arc welding processes replace flux-based shielding with a continuous flow of inert or semi-inert gas that blankets the arc and weld pool, preventing contamination from oxygen and moisture. These processes produce cleaner, lower-spatter welds than slag-shielded methods and are well-suited for lighter structural components and precision applications aboard ships.
TIG Welding (GTAW) — Tungsten Inert Gas
TIG welding uses a non-consumable tungsten electrode to generate the arc. Because the electrode does not melt, a separate filler rod is manually fed into the weld pool by the welder — or the process runs autogenously (without filler) for very thin materials. A ceramic nozzle directs a continuous flow of inert shielding gas — typically argon — around the arc and weld pool.
The inert gas blanket prevents oxidation, stabilizes the arc, and produces exceptionally clean, spatter-free welds with excellent mechanical properties. In shipbuilding, TIG welding is used for:
- Thin-gauge plate and sheet metal assemblies
- Stainless steel pipe and tube joints in mechanical systems
- Precision structural components where weld quality and appearance are critical
- Root pass welding on pipe systems before filling with MIG or SMAW
TIG welding is slower than MIG or SMAW, but the resulting weld quality is unmatched for applications where strength, cleanliness, and visual inspection are required.
MIG Welding (GMAW) — Metal Inert Gas
MIG welding shares TIG’s gas shielding principle but uses a consumable wire electrode fed continuously and automatically through the welding torch. The wire serves as both the electrode (conducting current to maintain the arc) and the filler material (melting into the weld pool). An electrical contact tube inside the torch connects the wire to the power source, while a separate gas line delivers the shielding gas — most commonly carbon dioxide or a CO₂/argon mix in shipbuilding applications.
Because the wire feed is motorized and continuous, MIG welding is significantly faster than TIG or SMAW and is well-suited for production environments. In shipbuilding, MIG welding is used for:
- Fabrication of aluminum deckhouses and superstructures
- Circular membrane tanks in liquefied gas tankers
- General structural assembly where production speed is prioritized
- Semi-automated and robotic welding systems in modern shipyards
Resistance Welding Techniques
Resistance welding bonds metals using a combination of pressure and electrical current — no filler material, flux, or shielding gas is required. When current passes through the contact interface between two metal sheets, electrical resistance at that point generates concentrated heat, melting and fusing the metals together. Resistance welding is fast, repeatable, and cost-effective for sheet metal fabrication.
Spot Welding
Spot welding is the most common resistance welding process. Two copper electrode tips clamp the metal sheets together under pressure, and a burst of current flows through the contact point, creating a localized weld nugget. The process takes a fraction of a second and requires no consumables.
In shipbuilding, spot welding is used for thin sheet metal assemblies, interior outfitting components, and prefabricated panels where dozens of small attachment points are more practical than continuous seams.
Seam Welding
Seam welding is a continuous variation of spot welding. Instead of point electrodes, rotating copper wheel electrodes roll along the joint, applying pressure and current in a rapid sequence that produces overlapping weld nuggets — forming a continuous, gas-tight or watertight seam. Seam welding is used for tank fabrication and any application requiring a leak-proof joint in thin-gauge material.
Projection Welding
Projection welding concentrates the weld current at one or more pre-formed projections (raised bumps or ridges) on one of the workpieces. As current flows and the projections collapse under electrode pressure, weld nuggets form at each contact point simultaneously. This allows multiple welds to be made in a single press cycle, making projection welding highly energy-efficient with increased weld strength at each joint. It is used for brackets, clips, and multi-point fastening applications throughout the ship.
Specialized Welding Processes
Beyond the standard arc, gas, and resistance categories, shipyards employ several specialized welding processes for specific structural challenges and material requirements.
Plasma Arc Welding
Plasma arc welding operates on a principle similar to TIG welding, but the arc is constricted through a fine copper nozzle that ionizes the gas into a high-velocity plasma jet. This produces a hotter, more focused arc than standard TIG — making it suitable for extremely thin metals and precision applications where conventional TIG would introduce too much heat. The tungsten electrode remains recessed inside the nozzle and does not contact the workpiece.
Laser Welding
Laser welding uses a focused beam of high-intensity light — generated by CO₂ lasers or neodymium yttrium aluminum garnet (Nd:YAG) crystals — to melt and fuse the base metals with minimal heat input. Because the heat-affected zone is extremely narrow, laser welding produces far less distortion than conventional arc processes, making it valuable for precision hull components and thin structural panels. Modern shipyards increasingly adopt laser welding and laser-arc hybrid systems for their combination of speed, accuracy, and low deformation.
Thermit Welding
Thermit welding uses an exothermic chemical reaction — igniting a mixture of aluminum powder and iron oxide — to generate sufficient heat to fuse large steel sections together without any external power source. The reaction produces molten steel that flows into a mold surrounding the joint, forming the weld as it solidifies. Thermit welding is reserved for the largest, most structurally demanding joints in shipbuilding — such as the ship’s stern frame — where conventional arc processes cannot deliver adequate penetration or where access to electrical power is restricted.
Friction Stir Welding
Friction stir welding (FSW) is a solid-state process — the metal never reaches its melting point. A rotating pin tool is plunged into the joint between two workpieces and traversed along the seam. Friction between the spinning pin and the base metal generates enough heat to plasticize (soften without melting) the material, which the tool stirs together to form a solid-state weld.
FSW is particularly well-suited for shipbuilding because:
- It produces low-distortion welds with excellent mechanical properties
- It works vertically, enabling friction welding of side shell joints between ship blocks
- It is highly effective on aluminum — a material that is difficult to weld with conventional arc processes without porosity or cracking
- There is no filler material, flux, or shielding gas required
Multiple Pass Welding
When welding thick plates — generally anything over 6mm — a single weld pass cannot fill the full joint depth and achieve complete penetration. Multiple pass welding involves laying successive weld beads, one on top of another, until the joint is fully filled. Each pass must be cleaned (slag removed for SMAW, surface inspected) before the next is deposited. Multiple pass welding is standard for heavily beveled fillet welds and butt joints in structural sections throughout the ship.
Tack Welds
Tack welds are short, intermittent weld beads placed at regular intervals along a joint before the primary welding pass begins. They hold the plates in correct alignment and prevent them from shifting or warping due to thermal expansion and contraction during the main weld. Tack welds use the same electrode and process as the final weld run and are typically incorporated into the finished joint rather than removed.
How Shipyards Select the Right Welding Process
No single welding process is optimal for every joint on a ship. The selection depends on a combination of factors:
- Material type and thickness — mild steel, high-strength steel, stainless steel, and aluminum each respond differently to heat input and electrode chemistry
- Joint geometry and access — overhead and vertical joints limit process options; tight spaces may require manual SMAW over automated SAW
- Production volume — high-volume flat seams favour SAW or MIG; one-off repairs favour SMAW
- Quality and inspection requirements — pressure vessels, fuel tanks, and piping systems require higher weld integrity than non-structural outfitting
- Distortion tolerance — thin panels and precision components need low heat input processes (laser, TIG, FSW) to avoid warping
For critical applications — particularly piping and tube systems running throughout the vessel — orbital TIG welding delivers the repeatability and code-compliance that manual processes cannot consistently achieve.
Orbital TIG Welding for Ship Piping and Tube Systems
For tubes, pipes, fittings, and cylindrical components aboard ships, orbital welding automates the TIG process by rotating a non-consumable tungsten electrode 360° around the workpiece. Every pass is controlled by pre-programmed weld parameters — arc gap, travel speed, current, and gas flow — eliminating the variability of manual technique and ensuring consistent, full-penetration welds on every joint.
SEC Automation supplies orbital welding equipment — including fusion welding machines, power supplies, and weld heads — purpose-built for tube and pipe applications in demanding industries. Whether you need to purchase, rent, or get support for orbital welding systems, our team is ready to help you spec the right solution. Schedule a call with our team today.
Frequently Asked Questions
What type of welding is most commonly used in shipbuilding?
Shielded Metal Arc Welding (SMAW) is the most widely used manual welding process in shipbuilding due to its versatility across joint positions and materials. Submerged Arc Welding (SAW) dominates for high-volume flat seam work on heavy plates. MIG welding is standard for aluminum structures such as deckhouses.
What is submerged arc welding used for in shipbuilding?
Submerged arc welding is used for long, flat weld seams on heavy structural plates — including deck plating, shell plating, and longitudinal structural members. Its high deposition rate, deep penetration, and excellent joint purity make it the preferred downhand process for production welding in shipyards.
Why is stud welding used in the shipbuilding industry?
Stud welding allows bolts, studs, and fasteners to be permanently attached to ship surfaces without drilling or through-holes. It is used to fasten insulation panels to bulkheads, timber flooring to deck plates, and a range of outfitting components, providing strong fastening points with a clean, flush surface on the opposite side.
What welding process is used for aluminum in shipbuilding?
MIG (GMAW) and TIG (GTAW) welding are the primary processes for aluminum in shipbuilding. MIG is used for aluminum deckhouses and large structural sections due to its speed. TIG is used for thinner gauge aluminum and precision joints. Friction Stir Welding (FSW) is increasingly used for aluminum panels due to its low heat input and minimal distortion.
What is orbital welding and where is it used on ships?
Orbital welding is an automated TIG process where the electrode rotates 360° around the pipe or tube joint. It is used for piping and tube systems throughout the vessel — including fuel, hydraulic, cooling, and gas distribution lines — where consistent, repeatable, full-penetration welds are required to meet code specifications.
What welding processes produce watertight seams in shipbuilding?
Seam welding (resistance), submerged arc welding, and MIG welding are the primary processes used to produce continuous, watertight seams. For pipe and tube systems, orbital TIG welding delivers leak-tight, full-penetration joints that meet the stringent integrity requirements of marine applications.
