Titanium Gr 1 Pipes and Tubes for Aerospace and Process Industry
Nov 24, 2025
What Makes Grade 1 Titanium Suitable for Aerospace Tubing
Titanium Grade 1, designated UNS R50250 and Werkstoff 3.7025, is the softest and most formable of the commercially pure titanium grades. At room temperature its crystal structure is hexagonal close packed alpha phase, and it is stabilised only by the small amounts of oxygen, nitrogen and iron that remain within the specified limits. This structure, not the austenitic structure found in stainless steels, is what gives Grade 1 its combination of moderate strength, high ductility and outstanding corrosion resistance.
For aerospace tubing the important consequences are these: the grade offers the lowest strength of the commercially pure family, which means it can be bent, flared and expanded without cracking; it has excellent resistance to chloride attack, aviation hydraulic fluids and atmospheric exposure; and it keeps useful toughness down to cryogenic temperature. Where higher strength is needed, Grade 2 or Grade 5 tubing is substituted, but Grade 1 remains the preferred choice for formed and welded assemblies in hydraulic and pneumatic lines.
Equivalent Grades and Governing Specifications
Grade 1 titanium tube and pipe is produced to the wrought titanium standards below. Seamless and welded tube are covered by ASTM B338 and ASME SB338; seamless pipe by ASTM B861 and ASME SB861; welded pipe by ASTM B862 and ASME SB862. Welded tube made from strip is also covered by ASTM B337.
| Designation | Standard number | UNS | Product covered |
|---|---|---|---|
| Titanium Grade 1 | Werkstoff 3.7025 | R50250 | Commercially pure titanium, low oxygen |
| ASTM B338 / ASME SB338 | Seamless and welded tube | R50250 | Condenser, heat exchanger and general tube |
| ASTM B861 / ASME SB861 | Seamless pipe | R50250 | Corrosion-resistant process pipe |
| ASTM B862 / ASME SB862 | Welded pipe | R50250 | Large diameter welded pipe |
| ASTM B337 | Welded tube | R50250 | Tube produced from strip |
Size Range, Forms and Finishes
Tube and pipe are supplied in a wide range of diameters and wall thicknesses, and both random and fixed lengths can be produced. Round, square, rectangular and oval sections are available, with plain, bevelled or threaded ends depending on the connection method.
| Item | Range |
|---|---|
| Pipe size | 1/2 in NB to 24 in NB, schedule 10 through schedule XXS |
| Tube outside diameter | 1 mm to 254 mm OD |
| Tube wall thickness | 0.1 mm to 20 mm |
| Type | Seamless, ERW, welded, fabricated |
| Form | Round, square, rectangular, oval, hydraulic |
| Length | Single random, double random, fixed length |
| End finish | Plain, bevelled, threaded |
| Schedules | SCH20, SCH30, SCH40, STD, SCH60, SCH80, XS, SCH120, SCH140, SCH160, XXS |
Non-standard diameters, wall thicknesses and tolerances can be produced to drawing, which is common in aerospace programmes where the tube is sized to an existing hydraulic or fuel system envelope rather than to a stock schedule.
Chemical Composition of Grade 1 Titanium
| Element | C | Fe | H | N | O | Ti |
|---|---|---|---|---|---|---|
| Maximum, percent by weight | 0.08 | 0.20 | 0.015 | 0.03 | 0.18 | Balance |
The low oxygen and iron limits are what separate Grade 1 from Grade 2. Keeping interstitial elements at the bottom of the permitted range maximises ductility and impact toughness, which is exactly what a formed and welded tube line requires.
Mechanical and Physical Properties
| Property | Metric | Imperial | Note |
|---|---|---|---|
| Tensile strength, minimum | 240 MPa | 34,800 psi | Annealed tube |
| Yield strength, minimum | 138 MPa | 20,000 psi | 0.2 percent offset |
| Elongation, minimum | 24 percent | 24 percent | 50 mm gauge length |
| Hardness, Brinell | 120 HBW | 120 HBW | Annealed condition |
| Modulus of elasticity | 105 GPa | 15,200 ksi | In tension |
| Density | 4.51 g/cm3 | 0.163 lb/in3 | Room temperature |
| Poisson ratio | 0.37 | 0.37 | Room temperature |
Inspection, Testing and Documentation
Mill test certificates to EN 10204 3.1, with separate chemical and mechanical reports.
Positive material identification on finished tube to confirm the grade before dispatch.
Hydrostatic and nondestructive testing: eddy current, ultrasonic and radiographic examination on request.
Visual inspection reports and third-party inspection for aerospace and defence contracts.
Destructive testing for flaring, flattening and reverse bend to demonstrate formability.
Packing in wooden boxes, plastic bags or steel-strip bundles, with bundle or tube-end marking for traceability.
Applications Beyond Aerospace
The same properties that make Grade 1 a natural choice for aircraft hydraulic lines also serve the petrochemical, oil and gas, chemical, power generation, pharmaceutical, pulp and paper, food processing and refining industries. In these plants the tube carries aggressive process fluids, cooling water or high-purity product, and the passive oxide film on the titanium surface is what prevents both wall loss and product contamination.
Frequently Asked Questions
Q: What is the UNS number and equivalent designation for titanium Grade 1?
Grade 1 titanium is UNS R50250 and Werkstoff number 3.7025. It is a commercially pure grade with a maximum oxygen content of 0.18 percent and a maximum iron content of 0.20 percent.
Q: Is titanium an austenitic alloy?
No. Commercially pure titanium such as Grade 1 has a hexagonal close packed alpha crystal structure at room temperature and does not exhibit the face centred cubic austenitic structure of stainless steels.
Q: Which standards cover Grade 1 titanium tube and pipe?
Seamless and welded tube is specified to ASTM B338, seamless pipe to ASTM B861, welded pipe to ASTM B862, and welded tube made from strip to ASTM B337. ASME equivalents are SB338, SB861 and SB862.
Q: What size range is available?
Pipe is supplied from 1/2 in NB to 24 in NB, and tube from 1 mm to 254 mm outside diameter with wall thickness from 0.1 mm to 20 mm. Custom sizes, lengths and tolerances can be produced to drawing.
Q: What is the minimum tensile strength of Grade 1 tube?
Annealed Grade 1 tube has a minimum tensile strength of 240 MPa, a minimum yield strength of 138 MPa and a minimum elongation of 24 percent.
Q: Why choose Grade 1 rather than Grade 2 for aerospace tubing?
Grade 1 has lower interstitial content, so it is more ductile and easier to bend and flare. Grade 2 is selected where higher minimum strength is needed, while Grade 1 is preferred for heavily formed and welded assemblies.
