Refractory Metal Zr-2.5Nb
UNS R60901 · ASTM B350/B353
Zr-2.5Nb (UNS R60901, ASTM B350/B353) is a niobium-bearing zirconium alloy strengthened by cold work and stress relief or by beta quenching plus ageing, developed as the pressure-tube material for CANDU-type heavy-water reactors.
Reference datasheet — Zr-2.5Nb is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the Annealed condition
Zr-2.5Nb tempers and conditions
Zr-2.5Nb is supplied in 5 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault alpha-annealed / recrystallised (typ. 550–650 °C) | Pick for plate, sheet, bar and general fabrication where formability, weld ductility and dimensional stability matter more than peak strength. | 430 | 610 | 20 | 185 HB | 3.1 % IACS |
Beta quenched and aged (~500 °C) without cold work | Choose for forgings and thick sections needing strength above annealed levels where cold working is impractical; omega/beta-Nb decomposition provides the strengthening. | 550 | 700 | 15 | 21 HRC | 3 % IACS |
cold worked ~20–30 % and stress relieved (~400 °C/24 h) | Standard high-strength condition for pressure tubes and thin-wall tubing: highest creep resistance and yield strength with acceptable residual ductility. | 620 | 760 | 14 | 22 HRC | — |
Beta quenched, cold worked and stress relieved | Reactor pressure-tube specification route: beta quench refines the Nb-enriched beta phase, then cold pilgering plus 400 °C stress relief gives maximum in-reactor creep and growth resistance. | 650 | 800 | 13 | 250 HB | — |
Cold worked | Cold-worked (typically 20–30 % CW, stress-relieved ~400 °C) Zr-2.5Nb as used for CANDU-type pressure tubing — much higher strength and creep resistance with reduced ductility and anisotropic texture. | 680 | 850 | 14 | 24 HRC | 3.1 % IACS |
What is Zr-2.5Nb?
Zr-2.5Nb (UNS R60901, ASTM B350/B353) is a niobium-bearing zirconium alloy strengthened by cold work and stress relief or by beta quenching plus ageing, developed as the pressure-tube material for CANDU-type heavy-water reactors. It offers 430 MPa yield, 610 MPa tensile, 20% elongation and better creep resistance than the Zircaloys, with 6.55 g/cm³ density, 97 GPa modulus, 17.1 W/m·K conductivity, 3.1% IACS and a 1840 °C melting point. Service is normally capped near 400 °C, machinability is low (32) and remaining formability is limited (55) in cold-worked stock. Zircaloy-4 is the alternative where the extra strength is not needed. Zr-2.5Nb has a density of 6.55 g/cm³ (0.237 lb/in³), lighter than 77% of refractory metal grades. It melts at 1,840°C (3,344 °F). Zr-2.5Nb has a yield strength of 430 MPa (62.4 ksi) and a tensile strength of 610 MPa (88.5 ksi) — stronger than 66% of refractory metal grades. Elongation at break is 20% and the elastic modulus is 97 GPa (14.1 Msi).
What is Zr-2.5Nb used for?
- CANDU reactor pressure tubes
- Nuclear structural tubing
- High-strength reactor components
Advantages
- Tough — resists crack growth — 75 MPa·√m (68.3 ksi·√in), better than 88% of refractory metal grades
- Lightweight — 6.55 g/cm³ (0.237 lb/in³), better than 77% of refractory metal grades
Limitations
- Low stiffness — 97 GPa (14.1 Msi), worse than 91% of refractory metal grades
- Low electrical conductivity — 3.1 % IACS, worse than 78% of refractory metal grades
- Poor heat conductor — 17.1 W/m·K (9.88 BTU/hr·ft·°F), worse than 76% of refractory metal grades
Zr-2.5Nb properties
Typical room-temperature values for Zr-2.5Nb-Annealed; bars are the position among refractory metal grades.
Physical3
Zr-2.5Nb has a density of 6.55 g/cm³ (0.237 lb/in³), lighter than 77% of refractory metal grades. It melts at 1,840°C (3,344 °F).
Mechanical16
Zr-2.5Nb has a yield strength of 430 MPa (62.4 ksi) and a tensile strength of 610 MPa (88.5 ksi) — stronger than 66% of refractory metal grades. Elongation at break is 20% and the elastic modulus is 97 GPa (14.1 Msi).
Thermal6
Zr-2.5Nb is rated for continuous service to 400°C (752 °F). It conducts heat at 17.1 W/m·K (9.88 BTU/hr·ft·°F), worse than 76% of refractory metal grades. Thermal expansion is 6.3 µm/m·K (3.5 µin/in·°F).
Electrical3
Zr-2.5Nb conducts electricity at 3.1 % IACS, worse than 78% of refractory metal grades.
Chemical & Environmental3
Corrosion resistance is excellent (91/100), better than 81% of refractory metal grades.
Sustainability4
Producing a kilogram of Zr-2.5Nb takes about 1,300 MJ of energy and emits 80 kg of CO₂ — more than 57% of refractory metal grades. Typical recycled content is 10%.
Manufacturability8
Zr-2.5Nb's machinability is poor (32/100, better than 67% of refractory metal grades); weldability very good (70/100); formability good (55/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the refractory metal family
Yield strength against density for every refractory metal grade FabDigit runs. Zr-2.5Nb is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Zr-2.5Nb
Is Zr-2.5Nb easy to machine?
Machine like austenitic stainless but slower: rigid setups, sharp carbide or HSS tools, positive rake, heavy flood coolant, no dwelling — fine chips and dust are pyrophoric, so collect wet and never use water-only extinguishers on burning fines.
Can Zr-2.5Nb be welded?
GTAW or EBW with high-purity argon/helium chamber or full trailing and back shielding; keep oxygen, nitrogen and moisture out (any straw/blue/grey tint means embrittling contamination), no flux processes, and stress relieve cold-worked tube after welding.
Can Zr-2.5Nb be formed, bent or molded?
Form in the annealed condition, preferably warm (200–400 °C) for tight bends because of strong hcp texture and springback; cold-worked pressure-tube stock has little remaining formability and is finished by pilgering.
Zr-2.5Nb chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Nbprimary strengthener, beta-Zr stabiliser | 2.4 – 2.8 | 2.5 |
| Ocontrolled interstitial strengthener (900–1600 ppm) | 0.09 – 0.16 | 0.12 |
| Feresidual | ≤ 0.15 | 0.05 |
| Crresidual | ≤ 0.02 | |
| C | ≤ 0.03 | 0.01 |
| N | ≤ 0.01 | 0 |
| Hhydride embrittlement control | ≤ 0 | 8×10⁻⁴ |
| Hfnuclear grade: Hf must be removed for low neutron capture | ≤ 0.01 | 0.01 |
| Zr | balance |
What surface finishes work on Zr-2.5Nb?
Pickle in HNO3/HF to remove oxide and any alpha-case, then passivate or grow an anodic/thermal oxide for galling resistance; the natural oxide is protective, so paint and plating are rarely used.
Equivalent designations
Standards and trade names that resolve to Refractory Metal Zr-2.5Nb in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- R60901
- ASTM
- B350/B353
How much does Zr-2.5Nb cost?
Zr-2.5Nb is a high-cost refractory metal ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Zr-2.5Nb — frequently asked
What is Zr-2.5Nb used for?
Zr-2.5Nb is typically used for CANDU reactor pressure tubes, nuclear structural tubing and high-strength reactor components. In short: strongest common Zr alloy; CANDU pressure-tube grade; best Zr creep resistance.
What is the yield strength of Zr-2.5Nb?
Zr-2.5Nb has a typical yield strength of 430 MPa (62.4 ksi) and a tensile strength of 610 MPa (88.5 ksi) — stronger than 66% of refractory metal grades. Strength varies by condition: see the 5 listed tempers.
Is Zr-2.5Nb easy to machine?
Not especially — machinability is rated poor (32/100, better than 67% of refractory metal grades). Machine like austenitic stainless but slower: rigid setups, sharp carbide or HSS tools, positive rake, heavy flood coolant, no dwelling — fine chips and dust are pyrophoric, so collect wet and never use water-only extinguishers on burning fines.
Can Zr-2.5Nb be welded?
Yes — weldability is rated very good (70/100). GTAW or EBW with high-purity argon/helium chamber or full trailing and back shielding; keep oxygen, nitrogen and moisture out (any straw/blue/grey tint means embrittling contamination), no flux processes, and stress relieve cold-worked tube after welding.
What surface finishes work on Zr-2.5Nb?
Pickle in HNO3/HF to remove oxide and any alpha-case, then passivate or grow an anodic/thermal oxide for galling resistance; the natural oxide is protective, so paint and plating are rarely used.
Can Zr-2.5Nb be formed, bent or molded?
Form in the annealed condition, preferably warm (200–400 °C) for tight bends because of strong hcp texture and springback; cold-worked pressure-tube stock has little remaining formability and is finished by pilgering.
What is the maximum service temperature of Zr-2.5Nb?
Zr-2.5Nb is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Zr-2.5Nb Annealed and Zr-2.5Nb-CW?
Annealed is the default condition — pick for plate, sheet, bar and general fabrication where formability, weld ductility and dimensional stability matter more than peak strength. CW: cold-worked (typically 20–30 % CW, stress-relieved ~400 °C) Zr-2.5Nb as used for CANDU-type pressure tubing — much higher strength and creep resistance with reduced ductility and anisotropic texture. Yield strength is 430 MPa in Annealed versus 680 MPa in CW.
How much does Zr-2.5Nb cost?
Zr-2.5Nb is a high-cost refractory metal ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASTM B350/B350M — Zirconium and Zirconium Alloy Ingots for Nuclear Application — ASTM International (2022)
- ASTM B351/B351M — Hot-Rolled and Cold-Finished Zirconium and Zirconium Alloy Bars, Rod and Wire for Nuclear Application — ASTM International (2021)
- ASTM B353 — Wrought Zirconium and Zirconium Alloy Seamless and Welded Tubes for Nuclear Service — ASTM International (2017)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (Zirconium and Hafnium) — ASM International (1990)
- IAEA TECDOC series on Zr-alloy pressure tube and fuel channel behaviour (Zr-2.5Nb property compilations) — IAEA (2010)
- Zirconium alloy mill product and corrosion data (Zr702/Zr705/Zr-2.5Nb) — ATI / Wah Chang (2020)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.