Bending
Position the seam on the neutral axis (side of the bend) to reduce strain on the weld. O and H1x tempers in 3003 bend tightly.
Tube and pipe
Welded Aluminium Tube
Welded aluminium tube is made by roll-forming flat strip into a tube and joining the seam, usually by high-frequency (HF) welding. It gives very thin, uniform walls, long lengths and low cost in volume, and it can be made from clad strip for brazed heat exchangers. Metline supplies HF and laser welded round, oval and flat tube in 3003, clad brazing alloys, 5052 and 6063, to customers worldwide.
- Process
- HF or laser seam welding
- Wall
- about 0.2 – 3 mm
- Main grades
- 3003, clad brazing, 5052, 6063
- Standards
- ASTM B313 · EN 1592
What is welded aluminium tube?
Welded tube starts as a coil of slit strip rather than an extrusion billet. The strip is progressively formed by rolls into a round, open tube; its edges are heated to welding temperature by high-frequency current and forged together by squeeze rolls, without filler metal. The outside weld bead is trimmed, the tube is sized to the final shape and cut to length or coiled.
Because the wall thickness comes straight from rolled strip, welded tube can have thinner and more uniform walls than extruded tube, often down to about 0.2 – 0.3 mm. That makes it the standard product for automotive radiators, condensers, heater cores and charge-air coolers, where flat or oval tubes made from clad strip are brazed to fins. It is also used for furniture, ladders, irrigation, antennas and other light structures where cost per metre matters.
The trade-off is the longitudinal seam. A well-made HF weld is a solid-state bond as strong as the parent strip in non-heat-treatable grades, but it is still a feature that the designer and inspector must account for, particularly in pressure service and tight bends.
How welded aluminium tube is made
- Strip preparationCoil is slit to the exact width that gives the tube circumference, with clean, burr-free edges essential for a sound weld.
- Roll formingA series of forming stands bends the strip into an open round section with the edges meeting at the weld point.
- HF weldingHigh-frequency induction or contact welding heats the edges, and squeeze rolls forge them together. Oxide is expelled into the bead, leaving a clean bond.
- Bead removalThe external bead is scarfed flush; the internal bead can be removed or controlled to a set height where the bore must be smooth.
- Sizing and shapingSizing rolls bring the tube to final OD, or reshape it into oval, flat or rectangular forms for heat exchangers.
- Testing and cuttingIn-line eddy current testing checks the seam continuously, then the tube is cut to length or level-wound into coils.
Laser welding is also used for very thin or high-precision tube. Large-diameter welded aluminium pipe is made separately, by arc welding of formed plate or by spiral welding.
Welded tube grades and clad materials
| Material | Character | Typical welded tube uses |
|---|---|---|
| 1050 / 1100 | Highly formable, conductive, low strength | Antennas, decorative tube, light-duty fluid lines |
| 3003 / 3102 | Good formability and corrosion resistance; brazeable core | Refrigerant lines, condenser and heater tube |
| 3003 + zinc arc-spray or Zn-clad | Sacrificial outer layer protects the core from pitting | Automotive condenser and radiator tube |
| Clad brazing strip (4343 or 4045 on 3xxx core) | Filler layer melts in the brazing furnace to join fins and headers | Radiators, charge-air coolers, oil coolers |
| 5052 | Higher strength, good marine resistance | Furniture, marine rails, ladders, structural light tube |
| 6063 / 6061 | Heat-treatable; strength reduced near seam unless re-heat-treated | Furniture, frames, sports goods |
Typical properties follow the parent strip: 3003-H14 is about 150 MPa tensile and 145 MPa yield; 5052-H32 about 228 MPa and 193 MPa. In brazed heat exchangers the tube is softened by the brazing cycle, so designers use post-braze (near O temper) properties, roughly 110 – 130 MPa tensile for 3003, or choose long-life core alloys with higher post-braze strength.
Welded tube shapes, sizes and weights
Typical supply range
- Round tube OD
- about 6 – 150 mm
- Wall thickness
- about 0.2 – 3 mm
- Flat and oval tube
- Widths of roughly 12 – 100 mm and heights from about 1.2 mm for heat exchangers, single or multi-chamber (folded or with inserts)
- Square and rectangular
- Small sections for furniture and frames by reshaping round tube
- Lengths
- Cut lengths from short pieces to about 6 m, or level-wound coils
- Testing
- In-line eddy current; leak, flaring, flattening and burst tests on request
Weight in kg/m = 0.0084823 × (OD − wall) × wall, dimensions in mm, at 2.70 g/cm³.
| OD (mm) | Wall (mm) | kg per metre | metres per 100 kg |
|---|---|---|---|
| 8 | 0.5 | 0.032 | 3144 |
| 10 | 0.6 | 0.048 | 2090 |
| 12.7 | 0.7 | 0.071 | 1403 |
| 16 | 0.8 | 0.103 | 970 |
| 19.05 | 0.89 | 0.137 | 729 |
| 22 | 1 | 0.178 | 561 |
| 25.4 | 1.2 | 0.246 | 406 |
| 32 | 1.2 | 0.314 | 319 |
| 38 | 1.5 | 0.464 | 215 |
| 50 | 1.5 | 0.617 | 162 |
| 63.5 | 2 | 1.043 | 96 |
| 76.2 | 2 | 1.259 | 79 |
| 100 | 2.5 | 2.068 | 48 |
Standards, tolerances and testing
| Standard | Scope |
|---|---|
| ASTM B313 / B313M | Aluminum and aluminum-alloy round welded tubes |
| ASTM B547 / B547M | Formed and arc-welded round tube (larger diameters) |
| EN 1592-1 to -4 | HF seam-welded tubes: delivery conditions, properties and tolerances for round and other shapes |
| EN 573-3 | Chemical composition of the strip alloy |
| Customer drawings | Flat and oval heat-exchanger tube is normally made to OEM drawings with tight height and width tolerances |
- Eddy current testing: continuous in-line seam inspection, with defect marking or automatic rejection
- Mechanical tests: flattening, flaring (expansion) and reverse bend tests verify weld ductility
- Leak and burst: pressure or helium leak testing for refrigerant and coolant tube
- Dimensional: OD, wall, ovality, internal bead height and straightness
- Certification: EN 10204 3.1 certificate with alloy, temper, test and dimensional results
Bending, brazing and joining
Brazing
Clad tube is brazed with fins and headers in controlled-atmosphere (flux) or vacuum furnaces; keep surfaces clean and free of heavy oils.
End forming
Flaring, beading, reducing and expanding are routine; flaring tests confirm the seam can take it.
Fusion welding
3003 and 5052 welded tube can be TIG welded into assemblies; avoid welding directly across the seam where possible.
Corrosion protection
Zinc-diffused or clad outer layers sacrificially protect thin walls in road-salt environments.
Coating
Powder coating and anodising suit furniture and consumer tube in 5052 and 6063.
Where welded aluminium tube is used
- Automotive thermal systems: radiator, condenser, heater core, charge-air cooler and oil cooler tube
- HVAC and refrigeration: refrigerant lines, evaporator and condenser tube
- Furniture and consumer goods: chairs, tables, ladders, strollers, umbrellas and tent frames
- Agriculture: irrigation pipe and sprinkler lines
- Electrical: antennas, conduit and lighting tube
- Construction: lightweight frames, curtain rods and handrails
How to order welded tube from Metline
- SpecifyMaterial and any cladding, temper, shape and dimensions (OD and wall, or flat-tube width, height and wall), internal bead requirement, length or coil, test requirements and quantity.
- QuoteWe confirm alloy, temper, tolerances, certification, packing and delivery terms (EXW, FOB, CIF or DAP) for your destination.
- ProcessTube is produced to the agreed specification, eddy-current tested, cut or coiled, and capped or bagged to keep the bore clean.
- DocumentEach delivery carries a mill test certificate to EN 10204 3.1 with the cast analysis and mechanical results; third-party inspection can be arranged on request.
- ShipPacked in cartons, crates or on coil pallets with moisture protection, and shipped by sea or air on EXW, FOB, CIF or DAP terms.
References and standards
- ASTM B313 – Standard Specification for Aluminum and Aluminum-Alloy Round Welded Tubes
- ASTM B547 – Standard Specification for Aluminum and Aluminum-Alloy Formed and Arc-Welded Round Tube
- EN 1592 – Aluminium and aluminium alloys: HF seam welded tubes
- EN 573-3 – Aluminium and aluminium alloys: chemical composition and form of wrought products
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits for Wrought Aluminum (Teal Sheets)
Welded aluminium (aluminum) tube: frequently asked questions
Is welded aluminium tube as strong as seamless tube?
In non-heat-treatable alloys such as 3003 and 5052, a sound HF weld is close to parent-metal strength and passes flattening and flaring tests. For high-pressure or safety-critical service, seamless or drawn tube is still the safer specification.
What is HF welding?
High-frequency welding uses high-frequency current to heat the strip edges to welding temperature in a fraction of a second; rolls then forge them together without filler metal. It is fast, clean and suited to thin aluminium walls.
Why is welded tube used in car radiators and condensers?
It can be made with very thin, uniform walls from clad strip whose outer layer melts in the brazing furnace to bond the fins, giving light, efficient heat exchangers at low cost per metre.
Can the internal weld bead be removed?
Yes. The internal bead can be removed or controlled to a specified maximum height. State the requirement if the bore must be smooth for fluid flow or inserts.
How is the seam inspected?
Usually by continuous in-line eddy current testing, plus flattening, flaring and pressure or leak tests on samples, as agreed in the order.
Do you supply welded tube in coils?
Yes. Small-diameter welded tube for refrigerant and heat-exchanger use can be supplied level-wound in coils as well as in cut lengths.
Need welded aluminium tube?
Send material, shape, dimensions, testing and quantity. We will reply with options, certification and a delivered price.
