stainlesstec offers mechanised longitudinal seam welding of stainless steel and aluminium for precise parts, small batches and recurring components. The process suits long, straight welds that call for even weld quality and a repeatable process. On request we handle not only the welding but the manufacture and finishing of the parts as well.
In mechanised longitudinal seam welding, a straight joint is located precisely and the process guided along the weld under control. Unlike fully manual welding, feed, position and parameters can be set repeatably – an advantage above all on long straight welds and recurring parts. Depending on part, material and application, this can achieve:
even welds
repeatable weld geometries
constant process conditions
controlled welding speeds
high repeat accuracy
Typical parts for longitudinal seam welding
The process suits parts where two sheet edges are to be joined along a straight line, for example:
cylindrical vessels
tube bodies
sleeves
trays and enclosures
ducts
panelling
elongated sheet metal structures
components for machinery and plant
customer-specific special parts
Whether a particular part suits mechanised longitudinal seam welding depends on geometry, dimensions, material thickness and access to the weld.
Longitudinal seam welding of stainless steel
Longitudinal seam welding of stainless steel combines a repeatable process with the particular demands of the material. stainlesstec processes a range of weldable stainless grades, among them:
1.4301 / AISI 304
1.4307 / AISI 304L
1.4404 / AISI 316L
1.4571 / AISI 316Ti
and other grades as the project requires. Depending on the application we allow for material, thickness, filler metal, heat input and the requirements for weld root and surface.
Aluminium can be longitudinally seam welded too, provided alloy, component geometry and joint configuration suit the process. Its high thermal conductivity and alloy-dependent welding behaviour have to be allowed for when designing the process.
We process the common weldable aluminium alloys, including the AlMg and AlMgSi groups, and others once their weldability has been assessed. With recurring aluminium parts in particular, a controlled mechanised process can bring benefits in evenness and repeatability.
The quality of a mechanised longitudinal weld begins with the preparation of the individual parts. For the process to be repeatable, the edges to be joined have to be located accurately relative to one another. What matters includes:
Edge preparation
The joints have to suit the weld planned.
Joint gap
Large or varying gaps make an even process difficult.
Component geometry
The design has to allow the weld to be located securely and reached reliably.
Material thickness
It affects heat input, welding parameters and the speed that can be achieved.
Component tolerances
With recurring parts, the upstream operations have to create repeatable conditions too.
This is exactly why it pays to align cutting, forming and welding with one another.
Longitudinal welds on vessels and cylindrical parts
A typical field of use is vessels, cylinders and tube bodies formed from sheet: the sheet is first cut and brought into the required shape, then the two longitudinal edges are welded together.
Several factors are decisive here: the edges have to meet cleanly, the diameter or geometry of the part has to be maintained, and heat input must not cause uncontrolled distortion.
The quality of the finished longitudinal weld is therefore always the product of the entire chain – not of the welding operation alone.
Back purging in longitudinal seam welding of stainless steel
With stainless steel, the weld root on the inside of the part can matter as much as the visible face. Where heavy oxidation there is unwanted, the root can be protected from oxygen with purging gas during welding – of interest, for example, where the internal surfaces:
come into contact with media
have to meet heightened corrosion resistance requirements
are difficult to reach later on
have to meet particular cleanliness or surface requirements
Whether back purging is required depends on the material and the part’s later use.
Repeatability in small batches
A key advantage of mechanised longitudinal seam welding is controlled repetition: for recurring parts, location and welding parameters can be defined once and used again for further parts.
That makes the process particularly attractive for small batches, where what counts is not the quality of a single part but consistent execution across the whole run.
Less distortion through controlled process guidance
Long welds can put considerable heat into a part, causing thermal expansion and shrinkage that can distort thin-walled structures in particular.
In longitudinal seam welding, fixturing, welding speed and parameters can be matched to one another under control. The aim is a joint that is as even as possible with heat input kept in check.
Thermal distortion cannot be prevented entirely in every design. But it can be allowed for in the design, in part preparation and in how the process is set up.
From sheet to the longitudinally welded component
stainlesstec can take on the complete manufacture of the part:
That lets us consider at the cutting stage which dimensions and edge geometries the later weld will need. It reduces interfaces and allows production to be planned end to end.
When does longitudinal seam welding make sense?
The process is particularly attractive when:
a long straight weld is required
recurring parts are being made
an even weld finish is important
repeatable process conditions are required
vessels or cylindrical components are being produced
manual welding would introduce unnecessary variation
For complex spatial weld paths, 3D laser welding may be the better answer. For one-offs or widely varying geometries, manual TIG and MIG may suit better.
We therefore choose the process to suit the part, not the other way round.
Technical capabilities
Materials
Stainless steel and aluminium.
Production
Individual parts, prototypes, small batches and recurring components.
Applications
Vessels, cylinders, tube bodies, enclosures and technical components.
Preparation
Laser cutting and forming.
Further processing
Machining and surface finishing.
Welding
Mechanically guided straight longitudinal welds.
Manufacturing limits in longitudinal seam welding
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Maximum weld length
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Material thicknesses
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Component dimensions and diameters
We will add the specific figures in line with our machine specification.
Let’s talk about your project.
Send us your drawing or CAD data by email – together with material, batch size and your requirements. We will come back to you with a sound assessment.
