ASTM B862 Ti2 Titanium Welded Pipes for Heat Exchangers
Sep 09, 2025
Scope of ASTM B862
ASTM B862 covers welded titanium and titanium alloy pipe and tube for general, pressure, and heat exchanger service. It is the welded-tube counterpart of ASTM B861, which covers seamless product. The specification defines chemical composition, tensile requirements, dimensional tolerances, and the testing that each lot must pass before shipment. Pipe and tube produced to this standard are commonly supplied in the annealed condition.
Grade 2 (Ti2) Composition and Properties
Grade 2 is a commercially pure titanium grade with a nominal titanium content above 99%. Its specified composition limits per ASTM B862 include:
| Element | Composition (max, %) |
|---|---|
| Carbon | 0.08 |
| Oxygen | 0.25 |
| Nitrogen | 0.03 |
| Hydrogen | 0.015 |
| Iron | 0.30 |
| Titanium | Balance |
Minimum tensile requirements for Grade 2 are 345 MPa (50 ksi) tensile strength and 275 MPa (40 ksi) yield strength, with 20% elongation in 50 mm. Grade 2 offers a good balance of strength, formability, weldability, and corrosion resistance, which is why it dominates heat exchanger tube service.
Manufacturing of Welded Titanium Pipe
Welded titanium pipe is produced from cold-rolled strip or coil. The strip is roll-formed into a tube, then welded longitudinally using a gas tungsten arc welding (GTAW) process, typically without filler metal, which keeps the weld zone close to the parent metal composition. The weld seam is normally flattened or sized, and the tube may be cold drawn or annealed afterward. Because wall thickness is uniform, welded tube often provides better dimensional consistency per meter than seamless product of the same size.
Why Grade 2 Suits Heat Exchanger Service
Heat exchanger tubes see corrosive media, temperature cycling, and vibration. Grade 2 resists general corrosion in seawater, chlorides, and many chemical process streams, and its passive oxide film self-repairs when damaged. The annealed condition preserves ductility for tube rolling and expansion into tube sheets. With a density of about 4.51 g/cm3, Grade 2 tubes also reduce bundle weight compared with copper-nickel or stainless alternatives.
Testing and Certification
Each lot under ASTM B862 is subject to chemical analysis, tensile testing, flattening or flaring tests where applicable, and non-destructive examination such as ultrasonic or eddy-current testing. Hydrostatic or pneumatic pressure testing is also required. For heat exchanger service, buyers commonly request material certificates per EN 10204 Type 3.1, which trace the heat number, chemical results, and mechanical test data back to the mill.
Frequently Asked Questions
What is the difference between ASTM B862 and ASTM B338?
ASTM B862 covers welded titanium pipe and tube generally, while ASTM B338 covers both seamless and welded tube specifically for condensers and heat exchangers. Many mills supply B338 tube that also meets B862 requirements.
Can Grade 2 welded tube be used for seawater service?
Yes. Grade 2 is widely specified for seawater-cooled heat exchangers because of its excellent resistance to chloride pitting and crevice corrosion.
Is welded titanium tube as strong as seamless tube?
With a sound longitudinal weld made without filler metal, welded Grade 2 tube meets the same minimum tensile requirements as seamless tube per the applicable ASTM specification.
What wall thickness is typical for heat exchanger tube?
Common heat exchanger tube sizes range from 12.7 mm to 38 mm outside diameter with wall thicknesses of 0.5 mm to 1.6 mm, though the specification permits a wider range.
Does the weld seam need to be removed?
For most heat exchanger applications the seam is flattened and may be cold worked or annealed; the inside bead is typically removed or minimized for cleanliness and flow performance.
How is the weld quality verified?
Weld quality is verified by eddy-current or ultrasonic testing along the full length, plus hydrostatic or pneumatic testing, as required by the specification.
