Recrystallisation & hot strength
Metallurgical condition as supplied Required by the standard
| Form | Available condition |
|---|---|
| Plate, sheet, strip and foil (default) | Annealed |
| Plate, sheet, strip and foil, when so ordered | Fully recrystallised: 90% minimum recrystallised |
| Cold-worked or stress-relieved | By agreement between purchaser and manufacturer at the time of purchase |
Same requirements as unalloyed tantalum Ta1: annealed by default, with "fully recrystallized" (at least 90 %) available only if the order says so.
⚠ ASTM sets no mechanical property requirements for unannealed (not heat-treated) plate, sheet or strip. Ordering Ta-2.5W plate in a cold-worked condition leaves it without any strength minimum under this specification. The point of Ta-2.5W is precisely its higher strength over unalloyed tantalum (276 against 207 MPa in the thin-sheet band); ordering cold-worked material to push the strength further gives up the guaranteed minima, and the acceptance criteria then have to be agreed separately.
⚠ Worth repeating the contrast with niobium: niobium's 90 % recrystallisation is the DEFAULT, tantalum's has to be CALLED OUT.
Protective annealing atmosphere Informative only — not a basis for acceptance
Not permitted — This specification prescribes no protective annealing atmosphere.
For R05252 the finished-product interstitial limits are the same as for unalloyed R05200: O 0.025, N 0.010, H 0.0015, C 0.020. The 2-3.5 % tungsten does not change how gas pickup is controlled.
Tantalum has to be annealed in high vacuum or high-purity inert gas, and the check is whether the finished product's O, N and H are still inside the finished-product limits, not what the furnace is nominally flowing.
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 | |||
| Ta | Tantalum | Bal. | |
| W | Tungsten | 2 – 3.5% | |
| Element | Name | Content % | |
|---|---|---|---|
| Minor & residual6 elements | |||
| Nb | Niobium | ≤ 0.5% | |
| O | Oxygen | ≤ 0.015% | |
| C | Carbon | ≤ 0.01% | |
| N | Nitrogen | ≤ 0.01% | |
| H | Hydrogen | ≤ 0.0015% | |
| Fe | Iron | ≤ 0.01% | |
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 ≥ % | Other requirements and notes |
|---|---|---|---|---|---|
| Bar and forgings | |||||
| Bar, 3.18–63.5 mm | Annealed | ≥ 276 (40 ksi) | ≥ 193 (28 ksi) | ≥ 20 | |
| Plate, sheet and strip | |||||
| Plate, sheet and strip | Annealed, t <3.175 mm | ≥ 276 (40 ksi) | ≥ 207 (30 ksi) | ≥ 20 | |
| Plate, sheet and strip | Annealed, t ≥3.175 mm | ≥ 276 (40 ksi) | ≥ 152 (22 ksi) | ≥ 25 | |
| Plate, strip and foil | Annealed (M), t 0.2–1.5 mm | ≥ 280 | ≥ 200 | ≥ 20 | Mechanical properties tested only when the contract requires them (longitudinal specimens). |
| Plate, strip and foil | Annealed (M), t ≥1.5–6.0 mm | ≥ 280 | ≥ 180 | ≥ 25 | As above |
| Plate, strip and foil | Cold-worked (Y), t ≥0.2–6.0 mm | ≥ 480 | — | ≥ 2 | Cold-worked: tensile and elongation only, tested only when the contract requires. |
| Wire and filler metals | |||||
| Wire | Annealed, dia. 0.254–0.379 mm | ≥ 276 (40 ksi) | — | ≥ 5 | No yield requirement. |
| Wire | Annealed, dia. 0.381–0.633 mm | ≥ 276 (40 ksi) | — | ≥ 10 | As above |
| Wire | Annealed, dia. 0.635–3.14 mm | ≥ 276 (40 ksi) | — | ≥ 15 | As above |
Where this grade is recommended
Matched in 1 service conditions; ranks and scores computed from the condition-scoring matrix.
| Service condition | Industry | Temperature | Rank | Score |
|---|---|---|---|---|
| HCl & reducing acids | Chemical Processing | 60 – 110 °C | 1 / 8 | 93 |
Designations & equivalents
| UNS | R05252 |
| EN designation | Ta-2.5W |
| Trade name(s) | Tantaline / Ta-2.5W |
| ASTM / AISI | B365 / B521 / B708 |
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
5 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 Ta-2.5W (RO5252)?
Ta-2.5W (RO5252) — Tantalum / Niobium. Strength-upgraded tantalum — hot concentrated HCl/H₂SO₄ exchangers and linings
What is the maximum service temperature of Ta2.5W?
Typically about 400 °C; the practical limit depends on media, stress and design life — acceptance per the governing standard.
What is the tensile strength of Ta2.5W?
The specified minimum tensile strength is 276 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 Ta2.5W?
ASTM B708, ASTM B365, ASTM B521, GB/T 3629, YS/T 751
Where is Ta2.5W typically used?
HCl & reducing acids (Chemical Processing)
In which forms is Ta2.5W 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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