What grades does ASTM B338 cover for heat exchanger tubes?
The ASTM B338 specification covers seamless and welded titanium alloy tubes for condensers and heat exchangers. The following grades are covered in this guide:
| Grade | Type | Key Characteristics |
|---|---|---|
| Gr.1 | Unalloyed titanium | Highest ductility, best formability, excellent corrosion resistance |
| Gr.3 | Unalloyed titanium | Higher strength than Gr.1 and Gr.2 |
| Gr.7 | Unalloyed + 0.12-0.25% Pd | Exceptional corrosion resistance in reducing acids |
| Gr.9 | Ti (3% Al, 2.5% V) | High strength, good weldability |
| Gr.11 | Unalloyed + 0.12-0.25% Pd | Similar to Gr.7 with different processing |
These grades differ in chemical composition and mechanical properties, allowing for a wide range of applications. gr1 titanium tube is the most formable grade among them.
What is the chemical composition of these titanium grades?
| Grade | C | N | H | Fe | O |
|---|---|---|---|---|---|
| Gr.1 | 0.08 | 0.03 | 0.015 | 0.20 | 0.18 |
| Gr.3 | 0.08 | 0.05 | 0.015 | 0.30 | 0.35 |
| Gr.7 | 0.08 | 0.03 | 0.015 | 0.30 | 0.25 |
| Gr.9 | 0.08 | 0.03 | 0.015 | 0.25 | 0.15 |
| Gr.11 | 0.08 | 0.03 | 0.015 | 0.25 | 0.25 |
What are the mechanical properties of ASTM B338 titanium tubes?
| Grade | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) |
|---|---|---|---|
| Gr.1 | ≥ 240 | ≥ 170 | ≥ 24 |
| Gr.3 | ≥ 450 | ≥ 380 | ≥ 18 |
| Gr.7 | ≥ 345 | ≥ 275 | ≥ 20 |
| Gr.9 | ≥ 620 | ≥ 483 | ≥ 15 |
| Gr.11 | ≥ 240 | ≥ 170 | ≥ 24 |
Grade 1 has the lowest strength but highest ductility. Grade 1 titanium yield strength is 170 MPa minimum, with 24% elongation. Grade 9 (3Al-2.5V) offers the highest strength at 620 MPa tensile.
What are the key features of these titanium heat exchanger tubes?
| Feature | Benefit |
|---|---|
| Excellent corrosion resistance | Withstands aggressive chemicals, seawater, and acidic environments |
| High strength-to-weight ratio | Lightweight yet strong, reduces overall equipment weight |
| Thermal stability | Maintains properties at elevated temperatures |
| Efficient heat transfer | Optimized for condenser and heat exchanger duty |
| Seamless construction | No weld seam, eliminates potential failure points |
What industries use ASTM B338 titanium tubes?
| Industry | Application |
|---|---|
| Chemical Processing | Heat exchangers for corrosive chemicals, gr1 titanium reactor components |
| Power Generation | Condensers and heat exchangers in power plants |
| Oil & Gas | Heat exchangers for oil refining and gas processing |
| Aerospace | Aircraft heat exchangers and other aerospace systems |
| Marine | Heat exchangers for seawater desalination and shipbuilding |
gr1 titanium for chemical processing provides excellent resistance to acid and alkali attack. gr1 titanium heat exchanger tubes are the standard choice for marine and chemical applications.
What are possible alternative grades to these titanium tubes?
While ASTM B338 Gr.1, Gr.3, Gr.7, Gr.9, and Gr.11 are widely used, alternative grades are available for specific applications:
| Alternative Grade | Difference |
|---|---|
| Gr.2 | Higher strength than Gr.1 (275 MPa yield), lower ductility (20% elongation) |
| Gr.12 | Contains 0.3% Mo and 0.8% Ni for improved strength and corrosion resistance |
| Gr.16 | Unalloyed titanium with 0.04-0.08% palladium, similar to Gr.7 but lower palladium |
Choose gr1 titanium tube when maximum formability is required. Choose Gr.7 or Gr.11 for enhanced corrosion resistance in reducing acid environments. Choose Gr.9 for high-strength applications.
How is ASTM B338 titanium tube inspected?
| Test | Description |
|---|---|
| Chemical Analysis | Verify titanium grade 1 composition and other grades per ASTM |
| Tensile Testing | Confirm yield strength, tensile strength, and elongation |
| Flattening Test | Per ASTM B338 for tube ductility |
| Flaring Test | Per ASTM B338 for tube expansion capability |
| Ultrasonic Testing (UT) | For seamless tubing |
| Eddy Current Testing (ET) | For welded tubing |
| Hydrostatic Test | Pressure test per standard |
| Dimensional Inspection | Verify OD, wall thickness, and length |
packaged
| Method | Description |
|---|---|
| Individual wrap | Plastic film or VCI paper around each tube |
| Bundling | Steel straps with protective padding |
| Wooden boxes | Export-standard plywood boxes |
| End caps | Plastic caps on both ends |
| Labeling | Grade, heat number, size, PO number |
FAQ
1. What is ASTM B338?
ASTM B338 is the standard specification for seamless and welded titanium and titanium alloy tubes for condensers and heat exchangers. It covers grades including Gr.1, Gr.3, Gr.7, Gr.9, and Gr.11 for thermal transfer applications.
2. What is the difference between Grade 1 and Grade 3 titanium tube?
Grade 1 has tensile strength of 240 MPa and yield strength of 170 MPa with 24% elongation. Grade 3 has higher tensile strength of 450 MPa and yield strength of 380 MPa but lower elongation of 18%. Choose Gr.1 for forming and Gr.3 for higher strength.
3. What is the difference between Grade 7 and Grade 11 titanium tube?
Both contain palladium (0.12-0.25%) for enhanced corrosion resistance in reducing acids. Grade 7 has tensile strength 345 MPa and yield 275 MPa. Grade 11 has tensile 240 MPa and yield 170 MPa, similar to Grade 1 but with palladium.
4. What is Grade 9 titanium tube used for?
Grade 9 (3Al-2.5V) is a high-strength titanium alloy with tensile strength of 620 MPa and yield strength of 483 MPa. It is used in aerospace hydraulic systems, aircraft heat exchangers, and high-pressure chemical processing equipment.
5. What industries use ASTM B338 titanium tubes?
Chemical processing, power generation, oil and gas, aerospace, and marine industries. Specific applications include heat exchangers for corrosive chemicals, power plant condensers, oil refining, aircraft systems, and seawater desalination.
6. What are the equivalent grades for Grade 1 titanium tube?
UNS R50250 and Werkstoff Nr. 3.7025 are the primary equivalents. Grade 1 is also known as commercially pure titanium with low oxygen (0.18% max) and low iron (0.20% max) for maximum ductility.
7. What is the difference between Grade 1 and Grade 2 titanium tube?
Grade 1 has lower yield strength (170 MPa vs 275 MPa) but higher elongation (24% vs 20%). Grade 2 is stronger but less formable. Both have excellent corrosion resistance. Choose Gr.1 for bending and forming; choose Gr.2 for higher pressure.
