Refractory Metal R04251 Annealed
Temper · default condition
UNS R04251 · ASTM B393 Type 3
Standard stocked condition for forming, deep drawing, tube reducing and welded reactor/alkali-metal hardware.
Values for the Annealed condition
Other R04251 tempers and conditions
R04251 is listed in 3 conditions; see the grade overview at R04251.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefaultThis page vacuum recrystallization annealed (ASTM B393 Type 3, annealed condition) | Standard stocked condition for forming, deep drawing, tube reducing and welded reactor/alkali-metal hardware. | 140 | 250 | 30 | 58 HRB | — |
Stress relieved | Pick when dimensional stability and moderate strength are wanted without full softening of cold-worked stock. | 260 | 340 | 18 | 133 HB | 8.3 % IACS |
Cold worked | Choose for maximum room-temperature strength and springiness in foil, wire and thin strip that will not see recrystallization temperatures. | 470 | 520 | 7 | 92 HRB | — |
What is R04251 Annealed?
R04251 Annealed is R04251 in the Annealed temper — standard stocked condition for forming, deep drawing, tube reducing and welded reactor/alkali-metal hardware. R04251 Annealed has a yield strength of 140 MPa (20.3 ksi) and a tensile strength of 250 MPa (36.3 ksi) — weaker than 96% of refractory metal grades. Elongation at break is 30% and the elastic modulus is 100 GPa (14.5 Msi). R04251 Annealed has a density of 8.6 g/cm³ (0.311 lb/in³), heavier than 54% of refractory metal grades. It melts at 2,410°C (4,370 °F).
Advantages
- Readily welded — 80/100, better than 92% of refractory metal grades
- Forms and bends easily — 90/100, better than 91% of refractory metal grades
- Ductile — tolerates forming and impact — 30%, better than 86% of refractory metal grades
Limitations
- Low strength — 140 MPa (20.3 ksi), worse than 96% of refractory metal grades
R04251 Annealed properties
Typical room-temperature values for R04251 Annealed; 11 are specific to this condition. Other listed values are R04251 reference data and may not represent this condition. Bars are the position among refractory metal grades.
Physical3
R04251 Annealed has a density of 8.6 g/cm³ (0.311 lb/in³), heavier than 54% of refractory metal grades. It melts at 2,410°C (4,370 °F).
Mechanical12
R04251 Annealed has a yield strength of 140 MPa (20.3 ksi) and a tensile strength of 250 MPa (36.3 ksi) — weaker than 96% of refractory metal grades. Elongation at break is 30% and the elastic modulus is 100 GPa (14.5 Msi).
Thermal6
R04251 Annealed is rated for continuous service to 400°C (752 °F). It conducts heat at 45 W/m·K (26 BTU/hr·ft·°F), better than 56% of refractory metal grades. Thermal expansion is 7.2 µm/m·K (4 µin/in·°F).
Electrical3
R04251 Annealed conducts electricity at 8.5 % IACS, better than 57% of refractory metal grades.
Chemical & Environmental3
Corrosion resistance is excellent (85/100), better than 52% of refractory metal grades.
Sustainability4
Producing a kilogram of R04251 Annealed takes about 900 MJ of energy and emits 55 kg of CO₂ — less than 59% of refractory metal grades. Typical recycled content is 15%.
Manufacturability8
R04251 Annealed's machinability is poor (28/100, worse than 58% of refractory metal grades); weldability very good (80/100); formability excellent (90/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with R04251 Annealed
Is R04251 easy to machine?
Very gummy and galling — use sharp, high-positive-rake carbide or HSS tools, slow speeds, heavy positive feeds and copious chlorinated or sulfurized oil, then degrease thoroughly to avoid hydrogen/carbon pickup.
Can R04251 be welded?
Excellent by GTAW in a purged glove box, EBW or laser in vacuum; the weld and heat-affected zone must be shielded until below ~200 °C or the joint embrittles from O/N/H pickup.
Can R04251 be formed, bent or molded?
Outstanding cold formability — deep draws, spinning and >90% cold reductions are practical with clean tooling and Nb-friendly lubricants; interanneal in vacuum at 1100–1250 °C.
What surface finishes work on R04251?
Chemically polish or electropolish (HF/HNO3-based or sulfuric-HF electrolytes); anodizes to durable colored Nb2O5 films; avoid pickling residues and always vacuum-degas before high-temperature service.
R04251 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 |
|---|---|---|
| Zrprimary alloying addition | 0.8 – 1.2 | 1 |
| Creactor-grade interstitial limit | ≤ 0.01 | 0.01 |
| Oreactor-grade interstitial limit | ≤ 0.02 | 0.01 |
| Nreactor-grade interstitial limit | ≤ 0.01 | 0 |
| Hreactor-grade interstitial limit | ≤ 0 | 5×10⁻⁴ |
| Tarestricted for low neutron cross-section | ≤ 0.1 | — |
| Wrestricted for low neutron cross-section | ≤ 0.05 | — |
| Hfrestricted for low neutron cross-section | ≤ 0.02 | — |
| Mo | ≤ 0.01 | — |
| Ti | ≤ 0.02 | — |
| Fe | ≤ 0.01 | — |
| Ni | ≤ 0.01 | — |
| Si | ≤ 0.01 | — |
| Nbbalance; limits above are ASTM B393 Type 3 reactor-grade maxima | balance | — |
R04251 Annealed — frequently asked
What is R04251 Annealed used for?
R04251 Annealed is typically used for nuclear reactor fuel cladding, liquid metal heat exchangers, high-temperature space reactor components and sodium-cooled reactor hardware. In short: reactor-grade Nb-1Zr; low neutron cross-section; stronger than pure niobium.
What is the yield strength of R04251 Annealed?
R04251 Annealed has a typical yield strength of 140 MPa (20.3 ksi) and a tensile strength of 250 MPa (36.3 ksi) — weaker than 96% of refractory metal grades. Strength varies by condition: see the 3 listed tempers.
Is R04251 Annealed easy to machine?
Not especially — machinability is rated poor (28/100, worse than 58% of refractory metal grades). Very gummy and galling — use sharp, high-positive-rake carbide or HSS tools, slow speeds, heavy positive feeds and copious chlorinated or sulfurized oil, then degrease thoroughly to avoid hydrogen/carbon pickup.
Can R04251 Annealed be welded?
Yes — weldability is rated very good (80/100). Excellent by GTAW in a purged glove box, EBW or laser in vacuum; the weld and heat-affected zone must be shielded until below ~200 °C or the joint embrittles from O/N/H pickup.
What surface finishes work on R04251 Annealed?
Chemically polish or electropolish (HF/HNO3-based or sulfuric-HF electrolytes); anodizes to durable colored Nb2O5 films; avoid pickling residues and always vacuum-degas before high-temperature service.
Can R04251 Annealed be formed, bent or molded?
Outstanding cold formability — deep draws, spinning and >90% cold reductions are practical with clean tooling and Nb-friendly lubricants; interanneal in vacuum at 1100–1250 °C.
What is the maximum service temperature of R04251 Annealed?
R04251 Annealed 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 R04251 Annealed and R04251-CW?
Annealed is the default condition — standard stocked condition for forming, deep drawing, tube reducing and welded reactor/alkali-metal hardware. CW: choose for maximum room-temperature strength and springiness in foil, wire and thin strip that will not see recrystallization temperatures. Yield strength is 140 MPa in Annealed versus 470 MPa in CW.
Sources
- ASTM B393 — Niobium and Niobium Alloy Strip, Sheet, and Plate — ASTM International (2020)
- ASTM B392 / B394 — Niobium and Niobium Alloy Bar, Rod and Seamless/Welded Tubing — ASTM International (2019)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (Refractory Metals) — ASM International (1990)
- ASM Specialty Handbook: Heat-Resistant Materials / Refractory metal design data — ASM International (1997)
- Nb-1Zr niobium-zirconium alloy mill product data — / ATI-type refractory metal producers (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.