Welded vs Seamless Titanium Tube for Heat Exchanger
May 22, 2026
| If your application requires | Choose this tube type |
|---|---|
| Large diameter (>50mm OD) | Welded tube (seamless not available in large sizes) |
| Small diameter (<20mm OD) | Seamless tube (more readily available in small sizes) |
| Lowest cost / budget sensitive | Welded tube (20-30% cheaper) |
| Highest pressure rating | Seamless tube (no weld seam, consistent wall) |
| Thin wall (0.5-0.7mm) | Both are available – seamless preferred for uniformity |
| U-bent tubes | Both can be bent – seamless more common |
Welded vs Seamless
| Comparison | Welded Titanium Tube | Seamless Titanium Tube |
|---|---|---|
| Production process | Flat strip → TIG welding → Cold working → Annealing | Hollow billet → Piercing → Cold rolling/drawing → Annealing |
| Weld seam | Yes (but cold worked + annealed = parent metal properties) | No |
| Cost | 20-30% lower | Higher |
| OD range | 6.0 – 1219 mm | 1.0 – 508 mm |
| Minimum wall thickness | 0.3 mm | 0.3 mm |
| 100% NDT required | ECT + UT + Reverse flattening | UT + Hydrostatic |
| ASTM B338 acceptance | ✅ Fully accepted | ✅ Fully accepted |
| Typical lead time | Shorter (stock available) | Longer (make to order) |
Welded Titanium Tube
| Advantage | |
|---|---|
| Lower cost (20-30% cheaper) | Large savings on material budget, especially for big projects |
| Larger OD range | Can produce up to 1219mm OD – seamless cannot |
| Tighter dimensional tolerance | Cold worked after welding ensures uniform OD/wall |
| Readily available in stock sizes | Common heat exchanger sizes (19mm, 25.4mm) often in stock |
| ASTM B338 certified | Fully accepted for heat exchanger service |
| Limitation | |
|---|---|
| Weld seam exists | Some buyers have concerns (though properly processed welds are reliable) |
| Requires more NDT | Must pass 100% ECT, UT, and reverse flattening test |
| Not available in very small OD | Below 6mm OD, seamless is preferred |
Seamless Titanium Tube
| Advantage | |
|---|---|
| No weld seam | Eliminates any concern about weld integrity |
| Better for high pressure | Consistent wall thickness, no potential weld weak point |
| Available in small diameters | Down to 1.0mm OD for precision applications |
| Preferred for U-bending | More common for tight radius bends |
| Uniform grain structure | Consistent mechanical properties throughout |
| Limitation | |
|---|---|
| Higher cost | 20-30% more expensive than welded |
| Limited OD range | Cannot exceed 508mm OD |
| Longer lead time | Often made to order, fewer stock sizes |
| Wall thickness variation | Can have slight eccentricity (OD/ID not perfectly concentric) |
How to Choose – By Application
| Application | Recommended Tube Type | Why |
|---|---|---|
| Large diameter heat exchanger (>50mm OD) | Welded | Seamless not available in large sizes |
| Small diameter precision tube (<15mm OD) | Seamless | Better availability, tighter tolerance |
| High pressure service (>5 MPa) | Seamless | No weld seam – highest confidence |
| Cost sensitive project | Welded | 20-30% savings, fully ASTM B338 certified |
| U-bent tubes (19mm, 25.4mm OD) | Both | Seamless more common, welded also works |
| Thin wall (0.5mm) for heat exchanger | Seamless preferred | More uniform wall thickness |
| Standard seawater condenser | Welded | Most cost effective, proven reliability |
For standard heat exchanger tubes (19mm, 25.4mm OD x 0.7-1.5mm wall) – both welded and seamless are acceptable. Choose based on budget and availability.
ASTM B338 Requirements for Titanium Tubes
Chemical Composition
| Grade | N (max) | C (max) | H (max) | Fe (max) | O (max) | Ti |
|---|---|---|---|---|---|---|
| Gr.1 | 0.03 | 0.08 | 0.015 | 0.20 | 0.18 | Balance |
| Gr.2 | 0.03 | 0.08 | 0.015 | 0.30 | 0.25 | Balance |
| Gr.7 | 0.03 | 0.08 | 0.015 | 0.30 | 0.25 | Balance |
Mechanical Properties (Annealed Condition)
| Grade | Tensile Strength (min) | Yield Strength (0.2% offset) | Elongation (min) |
|---|---|---|---|
| Gr.1 | 240 MPa (35 ksi) | 170 MPa (25 ksi) | 24% |
| Gr.2 | 345 MPa (50 ksi) | 275 MPa (40 ksi) | 20% |
| Gr.7 | 345 MPa (50 ksi) | 275 MPa (40 ksi) | 20% |
Not sure which grade to choose? Read our guide: Gr.1 vs Gr.2 vs Gr.7 – Which One for Seawater?
Required Tests
| Test | Purpose |
|---|---|
| Flattening test | Tube flattened to specified height without cracking |
| Flaring test | Tube end flared with 60° tool without cracking |
| Ultrasonic test (UT) | Detect internal flaws |
| Hydrostatic test | Pressure integrity verification |
| Tensile test | Confirm strength and elongation |
| Chemical analysis | Verify composition |
Additional Requirements for Welded Tubes
| Requirement | Purpose |
|---|---|
| Eddy current test (ECT) | Detect surface flaws on weld seam |
| Reverse flattening test | Weld placed at maximum stress to verify integrity |
| Automatic TIG welding | Consistent weld quality |
| Cold work + anneal after welding | Transform cast weld structure to equiaxed grains |
All GNEE titanium tubes meet ASTM B338 requirements. Mill Test Certificates (EN 10204 3.1) provided with every shipment.
FAQ
1. Is welded titanium tube as good as seamless for heat exchangers?
Yes. ASTM B338 welded tube is fully accepted for heat exchangers and condensers. The weld is cold worked and annealed to achieve equiaxed grain structure equal to parent metal.
2. Will the weld seam corrode in seawater?
No. Properly manufactured welded titanium tube has equal corrosion resistance to seamless. The weld zone is not a weak point for corrosion.
3. Which is cheaper – welded or seamless titanium tube?
Welded tube is 20-30% cheaper than seamless for the same size and grade. For large projects, this is significant savings.
4. Can welded titanium tube be used for U-bent heat exchangers?
Yes. Welded tube can be U-bent if properly annealed. Many U-bent heat exchangers use welded tube. The weld seam orientation should be considered during bending.
5. What tests are required for ASTM B338 welded tube?
100% eddy current (ECT), 100% ultrasonic (UT), reverse flattening test, flattening test, flaring test, and hydrostatic test. Seamless does not require ECT or reverse flattening.
6. What diameter range can you supply in welded vs seamless?
Welded: 6.0 – 1219mm OD. Seamless: 1.0 – 508mm OD. For large diameter heat exchangers (>50mm), welded is the only option.
7. Why do some specifications require seamless only?
Some old specifications or conservative engineers require seamless due to concerns about weld integrity. This is often unnecessary but must be respected.
8. Does GNEE supply both welded and seamless titanium tubes?
Yes. GNEE supplies both types in Gr.1, Gr.2, and Gr.7. We can recommend the right type based on your application and budget.
9. How do I know if welded tube is properly made?
Ask for: EN 10204 3.1 Mill Test Certificate showing ECT, UT, reverse flattening results, and cold worked + annealed condition. GNEE provides all.
10. Which one should I choose for my heat exchanger?
Send us your requirements (OD, wall, pressure, budget, quantity). GNEE will recommend welded or seamless based on your specific application.
Our Factory
| Equipment | Capability |
|---|---|
| Cold pilger mills | Seamless tube production, OD 1.0 – 508 mm |
| TIG welding lines | Welded tube production, OD 6.0 – 1219 mm |
| Vacuum annealing furnaces | Stress relief and recrystallization |
| Straightening machines | Dimensional accuracy |
| Eddy current testers | 100% NDT for welded tubes |
| Ultrasonic testers | 100% NDT for seamless tubes |
| Hydrostatic testers | Pressure verification |
| U-bending machines | U-bent tubes for heat exchangers |
SGS Certification
GNEE is an SGS certified manufacturer. SGS third-party inspection is available for every shipment upon request.
