Refractory Metal R04251
UNS R04251 · ASTM B393 Type 3
R04251 is niobium–1% zirconium with reactor-grade interstitial control, listed as ASTM B393 Type 3 and supplied annealed, stress-relieved or cold-worked in sheet, tube and wire.
Reference datasheet — R04251 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
R04251 tempers and conditions
R04251 is supplied in 3 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault 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?
R04251 is niobium–1% zirconium with reactor-grade interstitial control, listed as ASTM B393 Type 3 and supplied annealed, stress-relieved or cold-worked in sheet, tube and wire. The zirconium addition raises strength and creep resistance over unalloyed niobium — about 140 MPa yield, 250 MPa tensile, 30% elongation and 58 HRB — while retaining a low thermal-neutron cross-section for reactor and liquid-metal service. The 400 °C rating applies to bare exposure in air; higher temperatures require vacuum, inert gas, liquid-metal containment or a silicide/aluminide coating. Commercial R04261 is the lower-cost choice when tight interstitial control is not specified. R04251 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). R04251 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).
What is R04251 used for?
- Nuclear reactor fuel cladding
- Liquid metal heat exchangers
- High-temperature space reactor components
- Sodium-cooled reactor hardware
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 properties
Typical room-temperature values for R04251-Annealed; bars are the position among refractory metal grades.
Physical3
R04251 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 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 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 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 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'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. 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. R04251 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with R04251
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.
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 |
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.
Equivalent designations
Standards and trade names that resolve to Refractory Metal R04251 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- B393 Type 3
- Also called
- Nb-1Zr
How much does R04251 cost?
R04251 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.
R04251 — frequently asked
What is R04251 used for?
R04251 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?
R04251 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 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 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?
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 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?
R04251 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.
How much does R04251 cost?
R04251 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 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; 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.