ASTM B338 GR1 Heat Exchanger Tubes
May 20, 2026
What is ASTM B338 GR1?
ASTM B338 GR1 titanium tubes are manufactured for shell-and-tube heat exchangers, surface condensers, and evaporators. GR1 grade provides high ductility for U-bending and excellent corrosion resistance in seawater, chlorides, and chemical process media.
| Property | Value |
|---|---|
| Standard | ASTM B338 |
| Grade | GR1 (Grade 1, CP1) |
| Type | Seamless or welded |
| Outside diameter range | 6.35 mm to 76.2 mm |
| Wall thickness range | 0.5 mm to 3.0 mm |
| Length | 1 m to 30 m (cut lengths or random) |
| Surface finish | Annealed and pickled, bright annealed, as rolled |
Chemical Composition (Grade 1)
| Element | Percentage (max unless noted) |
|---|---|
| Titanium (Ti) | 99.5% minimum |
| Oxygen (O) | 0.18% |
| Iron (Fe) | 0.20% |
| Carbon (C) | 0.08% |
| Nitrogen (N) | 0.03% |
| Hydrogen (H) | 0.015% |
Oxygen is the most critical element. Lower oxygen means higher ductility for bending. GR1 has the lowest oxygen of all commercial pure titanium grades. If oxygen exceeds 0.18 percent, the material is not GR1.
Mechanical Properties
ASTM B338 GR1 tubes meet the following mechanical requirements.
| Property | Requirement |
|---|---|
| Tensile strength | 240 MPa minimum |
| Yield strength (0.2% offset) | 170 MPa to 310 MPa (depending on temper) |
| Elongation | 24% minimum in 50mm |
| Hardness | 120 HV to 200 HV (Vickers) |
For comparison with other grades:
| Grade | Tensile strength (MPa) | Elongation (%) | Oxygen max (%) |
|---|---|---|---|
| GR1 | 240 | 24 | 0.18 |
| GR2 | 345 | 20 | 0.25 |
| GR3 | 380 | 18 | 0.35 |
| GR5 | 895 | 10 | N/A (alloy) |
GR1 provides the best combination of corrosion resistance and formability for heat exchanger U-bends.
Dimensional Tolerances
ASTM B338 specifies tighter tolerances than general purpose specs like B861.
Outside diameter tolerance:
| OD (mm) | Tolerance (± mm) |
|---|---|
| Up to 25.4 | 0.10 |
| 25.4 to 38.1 | 0.13 |
| 38.1 to 50.8 | 0.15 |
| 50.8 to 76.2 | 0.20 |
Wall thickness tolerance:
| Wall thickness (mm) | Tolerance (± %) |
|---|---|
| All | 10% |
For reference, B861 pipe allows 12.5 percent wall tolerance. B338 is tighter.
Length tolerance:
| Length (m) | Tolerance (± mm) |
|---|---|
| Up to 6 | 3 |
| 6 to 12 | 5 |
| 12 to 30 | 10 |
Required Tests per ASTM B338
ASTM B338 requires specific tests depending on whether the tube is seamless or welded.
Tests for seamless tube:
| Test | Purpose | Acceptance criteria |
|---|---|---|
| Chemical analysis | Verify composition | Within specified limits |
| Tensile test | Verify strength and ductility | 240 MPa min, 24% elongation min |
| Flattening test | Check ductility | No cracks after flattening |
| Flaring test | Check expansion capability | No cracks after flaring |
| Hydrostatic or eddy current | Check for leaks | Leak free |
Tests for welded tube:
| Test | Purpose | Acceptance criteria |
|---|---|---|
| Chemical analysis | Verify composition | Within specified limits |
| Tensile test | Verify strength and ductility | 240 MPa min, 24% elongation min |
| Flattening test | Check ductility | No cracks after flattening |
| Reverse flattening test | Check weld seam ductility | No cracks with weld at 90 degrees |
| Flaring test | Check expansion capability | No cracks after flaring |
| Hydrostatic or eddy current | Check for leaks | Leak free |
| Weld seam radiography | Check weld integrity | When specified |
Available Sizes
Standard heat exchanger tube sizes (most common):
| OD (mm) | Wall (mm) | Weight per meter (kg) | Typical application |
|---|---|---|---|
| 12.70 | 0.70 | 0.12 | Small condensers |
| 12.70 | 0.90 | 0.15 | Small condensers |
| 12.70 | 1.00 | 0.17 | Small condensers |
| 15.88 | 0.90 | 0.19 | Standard industrial |
| 15.88 | 1.00 | 0.21 | Standard industrial |
| 15.88 | 1.20 | 0.25 | Standard industrial |
| 19.05 | 1.00 | 0.26 | Most common |
| 19.05 | 1.20 | 0.31 | Most common |
| 19.05 | 1.60 | 0.40 | Most common |
| 25.40 | 1.20 | 0.43 | Large exchangers |
| 25.40 | 1.60 | 0.57 | Large exchangers |
| 25.40 | 2.10 | 0.73 | High pressure |
| 31.75 | 1.20 | 0.54 | High capacity |
| 31.75 | 1.60 | 0.72 | High capacity |
| 31.75 | 2.50 | 1.09 | High pressure |
Seamless vs Welded: Which One to Choose
| Factor | Seamless | Welded |
|---|---|---|
| Manufacturing | Pierced from solid billet | Formed from strip and welded |
| Weld seam | None | Longitudinal weld, full penetration |
| Strength | Uniform throughout | Weld area slightly different |
| Cost | Higher | 15 to 25 percent lower |
| Lead time for custom sizes | 6 to 8 weeks | 4 to 6 weeks |
| Availability | Good | Very good |
| Best for | High pressure, critical service, code applications | Non-critical service, cost sensitive projects |
For U-bend tubes with welded construction:
The weld seam must be placed on the neutral axis of the bend. The neutral axis is the line down the center of the bend where the material neither stretches nor compresses. This minimizes stress on the weld.
U-Bending Service
Bending specifications:
| Parameter | Value |
|---|---|
| Minimum bend radius | 1.5 x OD (for GR1) |
| Standard bend radius | 2.0 x OD |
| Maximum tube OD for bending | 31.75 mm |
| Minimum wall for bending | 0.7 mm |
| Accuracy | ± 1.5 mm on leg length |
| Surface protection | Mandrel to prevent ovality |
U-bend inspection:
Dye penetrant testing on sample bends
Visual inspection of all bends
Dimensional check of leg length and bend radius
Eddy current testing after bending (when specified)
For welded tube U-bends:
We mark the weld seam location before bending. The weld seam is placed on the neutral axis. Reverse flattening test results are provided with each heat.
Applications
Power generation:
Steam turbine condensers
Cooling water heat exchangers
Auxiliary coolers
Chemical processing:
Shell-and-tube heat exchangers for acids and chlorides
Evaporators
Condensers for corrosive service
Marine and offshore:
Seawater cooling systems
Platform heat exchangers
Ballast water treatment systems
Desalination:
Multi-stage flash (MSF) evaporators
Multi-effect distillation (MED) units
Brine heaters
Pharmaceutical:
Sterile cooling systems
Purified water heat exchangers
Clean steam condensers
HVAC:
Condensers for large chiller systems
Evaporators
Corrosion Resistance
Resistant to:
Seawater and brackish water
Chlorides (including high temperature chlorides)
Hypochlorite solutions
Chlorine gas (wet or dry)
Acetic acid
Formic acid
Dilute sulfuric acid (up to 10% at room temperature)
Nitric acid
Chromic acid
Organic acids
Not resistant to:
Hydrofluoric acid (any concentration)
Concentrated sulfuric acid (over 10%)
Concentrated hydrochloric acid (over 3% at elevated temperature)
FAQ
1. What is ASTM B338 GR1 titanium tube?
ASTM B338 is the specification for seamless and welded titanium tubes for heat exchangers and condensers. GR1 is commercially pure titanium with 0.18% oxygen maximum, providing high ductility for U-bending.
2. What is the difference between B338 and B861?
B338 is for heat exchanger tubes with tighter tolerances and required flattening and flaring tests. B861 is for general service seamless pipe with looser tolerances and no flattening requirement.
3. Can I use welded tube for U-bend heat exchangers?
Yes. ASTM B338 allows welded tube. The weld seam must be placed on the neutral axis of the bend. Welded tube costs 15 to 25 percent less than seamless.
4. What is the minimum bend radius for GR1 tube?
1.5 times the outside diameter. For 19.05mm OD tube, minimum bend radius is 28.6mm. Use 2.0 x OD for standard production to reduce crack risk.
5. What tests are required for B338 GR1 tube?
Seamless requires chemical, tensile, flattening, flaring, and hydrostatic or eddy current tests. Welded adds reverse flattening and weld seam radiography when specified.
6. What is the flattening test?
A sample tube is flattened between two plates until the walls touch. No cracks are allowed. This confirms ductility for bending.
7. What is the flaring test?
A sample tube is expanded with a tapered tool to a specified percentage. No cracks are allowed. This confirms ductility for tubesheet rolling.
8. How do I calculate tube weight?
(OD in mm minus wall in mm) times wall in mm times 0.0142 equals kilograms per meter.
9. What lengths are available?
Standard lengths from 1 meter to 30 meters. Cut lengths and random lengths available.
10. Do you stock common sizes?
Yes. 19.05mm OD and 25.40mm OD are typically in stock. Contact us for current gr1 titanium tube in stock list.
11. What is the lead time for standard sizes?
In stock sizes ship within 48 hours. Custom sizes require 4 to 8 weeks depending on OD, wall, and quantity.
12. Can you provide third party inspection?
Yes. SGS, Bureau Veritas, TUV inspection available upon request. Additional charge applies.
13. What surface finish is standard?
Annealed and pickled. This removes mill scale and provides a clean surface. Bright annealed available for applications requiring a smooth finish.
14. How are U-bent tubes packaged?
Individual tube protection on bend areas. Spacers between layers. Secured to prevent spring-back during transit.
