Recrystallisation & hot strength
Metallurgical condition as supplied Required by the standard
| Form | Available condition |
|---|---|
| Bar, rod and wire (default) | Fully annealed: at least 90% recrystallised |
| Cold-worked or stress-relieved temper | By agreement between purchaser and manufacturer at the time of purchase |
Unless otherwise stated, material is supplied fully annealed, that is, at least 90 % recrystallized.
⚠ The 90 % here is a measurable acceptance figure rather than an adjective, and it is the DEFAULT — it does not have to be called out on the order. That differs from tantalum, where the same 90 % applies only when the order specifies "fully recrystallized". Two refractory metals, the same number, but one gets it by default and the other has to ask.
The tensile minima are tied to that degree of recrystallisation (at least 90 %). Ordering a cold-worked temper takes you outside these minima, and the strength then has to be agreed separately.
⚠ The opposite of molybdenum, which is supplied stress-relieved by default and treats recrystallisation as the failure mode; niobium is supplied recrystallised.
Protective annealing atmosphere Required by the standard, conditionally
Not permitted — No protective annealing atmosphere is prescribed, but end-product interstitial samples (C, O, N, H) must be taken after all thermal and chemical processing.
No furnace gas is specified for niobium; instead, the interstitials in the FINISHED product must still conform after processing, turning the atmosphere question into an outcome check. That is harder to fudge, but it is only performed when the purchaser specifies it.
⚠ Ingot and finished-product limits are two different sets, and the finished-product one is looser: for Type 1 the oxygen limit goes from 0.015 to 0.0250, and for Type 2 from 0.025 to 0.0400. Processing picks up gas, so the finished-product limits are relaxed. Check whether a composition certificate reports ingot or finished-product values.
Chemical composition
Nominal: mid-range where both limits are given, the cap where only a maximum is, balance takes the remainder. Exact specified ranges below.
| Element | Name | Content % | |
|---|---|---|---|
| Main elements2 elements | |||
| Nb | Niobium | Bal. | |
| Zr | Zirconium | 0.8 – 1.2% | |
| Element | Name | Content % | |
|---|---|---|---|
| Minor & residual10 elements | |||
| C | Carbon | ≤ 0.01% | |
| N | Nitrogen | ≤ 0.01% | |
| O | Oxygen | ≤ 0.025% | |
| H | Hydrogen | ≤ 0.0015% | |
| Ta | Tantalum | ≤ 0.5% | |
| Fe | Iron | ≤ 0.01% | |
| Si | Silicon | ≤ 0.005% | |
| W | Tungsten | ≤ 0.05% | |
| Ni | Nickel | ≤ 0.005% | |
| Mo | Molybdenum | ≤ 0.05% | |
Mechanical minima by form
Guaranteed values differ by form, size and delivery condition; quotations confirm the specification, form, size and condition.
| Form | Condition | Rm MPa | Rp0.2 MPa | A ≥ % |
|---|---|---|---|---|
| Bar and forgings | ||||
| Round bar (φ3.18–63.5 mm) | Fully annealed, at least 90% recrystallised, Types 3/4 | ≥ 195 (28 ksi) | ≥ 125 (18 ksi) | ≥ 20 |
| Wire and filler metals | ||||
| Round wire (φ0.51–3.15 mm) | Fully annealed, at least 90% recrystallised, Types 3/4 | ≥ 195 (28 ksi) | — | ≥ 15 |
Where this grade is recommended
Matched in 2 service conditions; ranks and scores computed from the condition-scoring matrix.
| Service condition | Industry | Temperature | Rank | Score |
|---|---|---|---|---|
| Vacuum hot zone & hot dies | Furnaces & Vacuum | 1000 – 1400 °C | 6 / 6 | 82 |
| Vacuum electronics | Semiconductor & Vac-Electronics | 400 – 900 °C | 6 / 8 | 80 |
Designations & equivalents
| UNS | R04261 / R04251 |
| EN designation | Nb-1Zr |
| Trade name(s) | Nb-1Zr |
| ASTM / AISI | B392 / B393 |
For reactor use order Type 3 / R04251; this page follows commercial-grade R04261 (Type 4).
More detail 1
Both contain 0.8–1.2 % zirconium and have the same mechanical minima, but their impurity limits differ.
Cross-references are common near-equivalents for search and shortlisting; substitution across standards requires clause-by-clause verification. All grades in one cross-reference table →
Applicable standards
2 specifications. Name the standard and its edition on the order.
Guaranteed values and required tests differ between specifications — see Mechanical minima by form for the figures per form.
Frequently asked questions
What is Nb-1Zr (RO4261)?
Nb-1Zr (RO4261) — Tantalum / Niobium. Alkali-metal coolant and space nuclear service — high melting point with weldability
What is the maximum service temperature of NbZr1?
Typically about 1200 °C; the practical limit depends on media, stress and design life — acceptance per the governing standard.
What is the tensile strength of NbZr1?
The specified minimum tensile strength is 195 MPa for the main product form. Minima for other forms and sizes are listed under "Mechanical minima by form" on this page.
Which standards cover NbZr1?
ASTM B392, ASTM B393
Where is NbZr1 typically used?
Vacuum hot zone & hot dies (Furnaces & Vacuum); Vacuum electronics (Semiconductor & Vac-Electronics)
In which forms is NbZr1 available?
Tube, plate, strip, bar, forgings, wire and other forms — sizes and delivery condition confirmed per order, with EN 10204 3.1 / 3.2 certification.
Same series
Download PDF datasheet
This grade’s datasheet as an A4 PDF — for filing, printing or forwarding to colleagues.
Download PDF datasheetSupply & enquiry
Tube & pipeφ1 – 219 × 0.25 – 25 mm
Plate4.76 – 80 mm
Barφ8 – 300 mm
Wire & filler metalsφ0.01 – 8 mmFor this grade we can supply, against your service conditions:
- Tube, plate, strip, bar, forgings, wire and more — with size range and lead time
- Chemistry and mechanical test report (EN 10204 3.1 / 3.2)
- Like-for-like alternatives and selection advice
- Applicable standards and inspection scope
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