ASTM B338 Titanium Alloy Tubes

Grade 1 has the lowest strength but highest ductility. Grade 1 titanium yield strength is 170 MPa minimum with 24% elongation. Grade 5 offers the highest strength at 895 MPa tensile.

Delivery Conditions: As Rolled, Cold Drawn, Hot Finish, Stress Relieved, Annealed, Hardened, Tempered

Surface Coatings: Electropolish, Mechanical Polish, Satin Finish, Passivated

Gr1 titanium tube is recommended when maximum formability is required. Grade 2 is suitable for most general applications due to ready availability.

1. What is ASTM B338?
ASTM B338 is the standard specification for seamless and welded titanium and titanium alloy tubes for surface condensers, evaporators, and heat exchangers. It covers 28 grades including Grade 1, 2, 3, 5, 7, 9, 11, 12, and 23.

2. What is the difference between Grade 1 and Grade 2 titanium tube?
Grade 1 has lower oxygen (0.18% vs 0.25%) and lower iron (0.20% vs 0.30%), resulting in lower yield strength (170 MPa vs 275 MPa) but higher elongation (24% vs 20%). Choose gr1 titanium tube for forming; choose Grade 2 for higher pressure.

3. What is Grade 5 titanium tube used for?
Grade 5 (Ti-6Al-4V) has tensile strength of 895 MPa and yield strength of 828 MPa. It is used in aerospace, high-performance automotive, medical implants (Grade 23 ELI), and demanding industrial applications requiring high strength-to-weight ratio.

4. What is the difference between ASTM B338 and ASTM B861?
ASTM B338 specifically covers tubes for condensers and heat exchangers. ASTM B861 covers seamless titanium pipe for general pressure applications. ASTM B862 covers welded titanium pipe. Gr1 titanium pipe can be ordered to any of these standards.

5. What filler metal is needed to weld Grade 1 titanium tube?
Use AWS A5.16 ERTi-1 filler metal with automatic arc-welding process. Shielding must be 100% argon with back purge. Welded tube must be cold worked to final size to transform the cast weld microstructure.

6. What is Grade 7 titanium tube?
Grade 7 is unalloyed titanium with 0.12-0.25% palladium. It offers enhanced corrosion resistance in reducing acid environments compared to Grade 1 or Grade 2. Grade 11 is similar but with lower strength (same as Grade 1 with palladium).

7. What tests are required for ASTM B338 welded tubing?
Welded tubing must undergo: reverse flattening test, non-destructive electromagnetic test (eddy current), ultrasonic test, and hydrostatic or pneumatic test. The weld must be sufficiently cold worked to achieve equiaxed microstructure.

8. What is the chemical composition of Grade 1 titanium?
Grade 1 requires: nitrogen 0.03% max, carbon 0.08% max, hydrogen 0.015% max, iron 0.20% max, oxygen 0.18% max, titanium balance. Residuals each 0.1% max, total 0.4% max.

9. What is Grade 23 titanium (Ti-6Al-4V ELI)?
Grade 23 is extra low interstitial (ELI) version of Grade 5 with lower oxygen (0.13% max) and hydrogen (0.0125% max). It has tensile strength 828 MPa, yield 759 MPa, elongation 10%. Used for medical implants and critical aerospace components.

10. What is the difference between seamless and welded titanium tube?
Seamless tube is made from hollow billet by cold reducing or cold drawing with no weld seam. Welded tube is made from flat-rolled product by automatic arc-welding, then cold worked to final size. Both meet ASTM B338 specifications.