ASTM B862 Grade 2 Welded Titanium Pipe: UNS R50400 GTAW Data
Sep 09, 2025
What ASTM B862 Covers
ASTM B862 is the specification for welded titanium and titanium alloy pipe for general corrosive service, and ASME SB862 is its code equivalent. Unlike the seamless product of B861, B862 pipe is made by forming strip or plate into a cylindrical shell and welding the longitudinal seam. It offers larger diameters and thinner walls at lower cost than a seamless pipe of the same size. Grade 2, UNS R50400, is the grade most frequently ordered against this specification.
Grade 2 welded pipe is chemically identical to Grade 2 seamless pipe: commercially pure titanium, nominally 99.2 % titanium minimum excluding intentional additions, with iron limited to 0.30 %, oxygen to 0.25 %, nitrogen to 0.03 %, carbon to 0.08 % and hydrogen to 0.015 %.
The ERW Label and How Titanium Pipe Is Actually Welded
Catalogue descriptions of this product frequently use the term ERW, borrowed from carbon steel practice where the seam is produced by electric resistance welding. Titanium is not joined that way. Its high chemical reactivity at temperature and its low electrical resistivity make resistance welding impractical, and commercial production uses gas tungsten arc welding, plasma welding or laser welding with full inert-gas protection on both the face and the root of the seam. The label should therefore be read as longitudinally welded pipe. A buyer who specifies ERW in the carbon-steel sense is specifying a process that does not exist for titanium.
Mechanical Requirements and Weld Qualification
Minimum annealed properties for Grade 2 welded pipe are 345 MPa (50 ksi) tensile strength, 275 MPa (40 ksi) yield strength at 0.2 % offset, and 20 % elongation. Testing is arranged so that the welded joint, not only the base metal, is shown to reach these levels. Density 4.51 g/cm3, elastic modulus near 103 GPa and thermal conductivity about 15-16 W/(m*K) apply as for the seamless product.
| Product | Standard | Construction | Typical ordering basis |
|---|---|---|---|
| Welded pipe | ASTM B862 / ASME SB862 | Longitudinal seam, GTAW, plasma or laser | Nominal pipe size and schedule |
| Seamless pipe | ASTM B861 / ASME SB861 | Extruded and cold finished, no seam | Nominal pipe size and schedule |
| Tube | ASTM B338 / ASME SB338 | Seamless or welded, heat-transfer service | Outside diameter and wall thickness |
Manufacturing Sequence and Weld Quality
Strip or plate is cut, edge-prepared and formed by rolling. The longitudinal seam is welded with a trailing shield and a backing purge so that neither the face nor the root is exposed to air. ERTi-2 filler is used when the wall is thick enough to require it. Weld appearance is a practical quality indicator: a bright silver seam indicates adequate shielding, while straw, blue or grey oxide indicates contamination that must be removed or the pipe rejected. After welding, the pipe may be sized, straightened and annealed, the anneal being performed under vacuum or inert gas to restore ductility and to prevent hydrogen pickup.
Inspection, Testing and Size Range
B862 requires tensile testing of the welded joint, flattening tests, and either a hydrostatic test or an approved non-destructive alternative such as eddy-current or ultrasonic examination of the seam. Radiographic examination of the longitudinal weld is specified for critical service, and weld-bead requirements determine whether an as-welded or a finished flush seam is delivered. Welded Grade 2 pipe is generally offered from NPS 1/2 up to NPS 24, with walls from about 1.2 mm to 12 mm; larger diameters are produced by welding rolled plate, and additional tests may be requested where the pipe will be expanded, rolled or bent.
Applications and Selection Notes
Typical applications include chemical-process lines, seawater cooling systems, desalination plants, flue-gas desulphurisation piping, offshore utility piping and air or gas ducting in corrosive atmospheres. The welded product is normally selected where the diameter is too large or the wall too thin to be economical in seamless form, and where a longitudinal weld is acceptable under the governing design code. Where cyclic pressure or severe bending is expected, the seamless specification should be reviewed against the welded option before ordering.
FAQ
Q: Is B862 pipe the same as B861 pipe?
No. Both are pipe specifications for corrosive service, but B861 is seamless and B862 is welded with a longitudinal seam, so weld testing requirements and cost structure differ.
Q: Is titanium pipe really ERW?
No. Titanium pipe is produced by gas tungsten arc, plasma or laser welding; ERW is legacy catalogue terminology inherited from carbon steel pipe descriptions.
Q: What is the minimum tensile strength of Grade 2 welded pipe?
345 MPa (50 ksi) in the annealed condition, with 275 MPa (40 ksi) minimum yield strength and 20 % minimum elongation.
Q: What filler metal is used for the seam?
ERTi-2 filler is used where the wall thickness requires filler; thin walls are welded autogenously, with the same inert-gas shielding on face and root.
Q: How is the weld inspected?
Typically by eddy-current or ultrasonic examination of the seam, tensile and flattening tests, and hydrostatic pressure testing, with radiography added for critical service.
Q: Can welded Grade 2 pipe be used in seawater?
Yes. It is widely used in seawater and brine systems, provided the weld was made with adequate shielding and the crevice conditions at joints are managed.
