Titanium Grade 1 Tube: Composition, Specifications and Size Range
Nov 25, 2025
Titanium Grade 1 tube is wrought tubing made from the lowest-strength, highest-ductility grade of commercially pure titanium, covered by UNS number R50250. It is an unalloyed alpha titanium whose oxygen and iron contents are held to the tightest limits in the commercially pure family, which is exactly what gives it excellent cold formability, high ductility and reliable welding behaviour.
What Defines Titanium Grade 1
Commercially pure titanium is graded mainly by interstitial content. Grade 1 keeps oxygen at 0.18% maximum and iron at 0.20% maximum, the lowest of the common grades, so the material is softer and more formable than Grade 2 while offering the same outstanding corrosion resistance in oxidising and mildly reducing media. Two characteristics matter for tube work. First, density is about 4.51 g/cm³, roughly 57% of the 7.85 g/cm³ of carbon steel, so a Grade 1 tube line weighs a little over half of an equivalent steel line. Second, a protective oxide film forms spontaneously on the surface, and it is stable in seawater, chlorides, oxidising acids and most industrial process streams. The useful service range extends from cryogenic temperatures up to roughly 300 °C for pressure service, where creep and oxidation resistance remain adequate.
Chemistry and Mechanical Properties
| Item | Grade 1 (UNS R50250) | Grade 2 (UNS R50400) for comparison |
|---|---|---|
| Nitrogen, max | 0.03% | 0.03% |
| Carbon, max | 0.08% | 0.08% |
| Hydrogen, max | 0.015% | 0.015% |
| Iron, max | 0.20% | 0.30% |
| Oxygen, max | 0.18% | 0.25% |
| Titanium | Balance | Balance |
| Tensile strength, min | 240 MPa | 345 MPa |
| Yield strength, 0.2% offset, min | 138 MPa | 275 MPa |
| Elongation, min | 24% | 20% |
The high elongation and low yield strength of Grade 1 are the reason it is chosen for tube that must be expanded into tubesheets, bent to a tight radius, or coiled. Where higher strength is needed at the same corrosion resistance, Grade 2 is the usual step up, and where strength is the primary requirement rather than formability, an alloy grade such as Grade 5 (Ti-6Al-4V) or Grade 9 (Ti-3Al-2.5V) is selected instead.
Specifications, Size Range and Product Forms
Grade 1 tube and pipe are ordered to three main ASTM specifications, each with an ASME equivalent for pressure service: ASTM B338 covers seamless and welded tube for condensers and heat exchangers, ASTM B861 covers seamless pipe, and ASTM B862 covers welded pipe; welded pipe is also covered by ASTM B337. Plate, sheet and strip are covered by ASTM B265, bar and billet by ASTM B348, and the unalloyed grades intended for surgical implants by ASTM F67. Common ordering data include:
Nominal size: 15 mm NB to 150 mm NB (1/2 in to 6 in), with outside diameters generally 30 mm to 150 mm.
Wall thickness: approximately 2.5 mm to 25 mm, or a lighter wall for thin-walled heat exchanger tubing.
Schedules: SCH 10, SCH 20, SCH 30, SCH 40, STD, SCH 60, XS, SCH 80, SCH 120, SCH 140, SCH 160 and XXS.
Length: single random, double random or specified cut lengths.
Type: seamless, ERW, welded, EFW, cold drawn welded or fabricated.
Form: round, square and rectangular tube, coiled tube, U-bend, pancake coil and hydraulic tube.
Ends: plain end, bevelled end or threaded.
Certification: mill test certificate to EN 10204 3.1 showing chemical composition and mechanical properties.
Seamless or Welded: Choosing the Right Grade 1 Tube
Seamless Grade 1 tube is produced from a pierced or extruded hollow and then rolled and drawn to size, which removes the longitudinal weld and makes it the default choice for higher pressure, cyclic service and for tubes that will be expanded into a tubesheet. Welded tube is formed from strip and closed with an autogenous weld, then cold worked and annealed where necessary; it is economical for long straight runs, for large diameters and for applications where the seam can be kept out of the highest stress direction. Because Grade 1 has excellent ductility, welded tube can be cold reduced substantially without cracking, so a welded-and-drawn tube approaches seamless properties while remaining cheaper to produce. The decision is normally made on pressure rating, corrosion allowance, the acceptance standard required by the end user and the inspection method that will be applied to the seam.
Applications, Fabrication and Quality Verification
The largest use is heat transfer: condensers, coolers, evaporators and desalination plants, where thin-walled Grade 1 tube gives high heat transfer with a long life in seawater. Chemical and petrochemical plants use it for process lines carrying chlorides and oxidising media; the medical and food industries use it where biocompatibility and cleanliness are essential; marine and offshore projects use it for seawater piping and hydraulic lines; and aerospace and sports equipment use it where low weight matters. Fabrication relies on the same properties that define the grade: it can be rolled, bent, flared and expanded, and it welds cleanly when the joint is shielded from air.
Quality verification for a Grade 1 tube order normally combines a mill test certificate covering chemistry and mechanical properties, dimensional inspection of outside diameter, wall thickness and straightness, a hydrostatic or pneumatic proof test where specified by the standard, eddy current or ultrasonic testing of the wall, and visual inspection of both surfaces. Tubes for heat exchangers are frequently supplied after an air underwater test, and any pickling residue or embedded iron contamination is checked before the tubes are packed, because surface contamination is the main cause of premature corrosion in titanium tube bundles.
Frequently Asked Questions
Q: What is Titanium Grade 1 tube used for?
It is mainly used for heat exchanger and condenser tubing, seawater and chemical process piping, desalination plants, medical and food grade lines and other low-weight, corrosion-resistant applications where formability matters.
Q: What is the difference between Grade 1 and Grade 2 titanium tube?
Grade 1 has lower oxygen and iron, giving higher ductility with minimum tensile strength of 240 MPa, while Grade 2 is stronger at 345 MPa minimum tensile strength with slightly lower elongation.
Q: Which specifications cover titanium Grade 1 tube?
ASTM B338 covers seamless and welded tube for condensers and heat exchangers, ASTM B861 covers seamless pipe, ASTM B862 covers welded pipe, and the ASME SB versions apply for pressure service.
Q: Can Grade 1 tube be welded?
Yes. Grade 1 is readily welded by TIG and similar processes, provided the joint is protected by high-purity inert gas and the surface is free from oil, moisture and oxide contamination.
Q: How much lighter is a titanium Grade 1 tube than a steel tube?
Titanium has a density of about 4.51 g/cm³ against 7.85 g/cm³ for carbon steel, so a Grade 1 tube weighs roughly 57% as much as the same steel section.
Q: What documentation is supplied with a Grade 1 tube order?
Orders are normally supplied with a mill test certificate to EN 10204 3.1 reporting chemical composition and mechanical properties, together with dimensional and non-destructive test results where required.
