Refractory Metal R04251-SR (Stress relieved)
Heat-treated state
UNS R04251 · ASTM B393 Type 3
Pick when dimensional stability and moderate strength are wanted without full softening of cold-worked stock.
Values for the SR 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 |
|---|---|---|---|---|---|---|
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 | — |
SRThis page 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-SR?
R04251-SR is R04251 heat treated to SR — pick when dimensional stability and moderate strength are wanted without full softening of cold-worked stock. R04251-SR has a yield strength of 260 MPa (37.7 ksi) and a tensile strength of 340 MPa (49.3 ksi) — weaker than 68% of refractory metal grades. Elongation at break is 18% and the elastic modulus is 100 GPa (14.5 Msi). R04251-SR 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). Annealed is the default condition FabDigit quotes; SR is available on request or by drawing note.
Advantages
- Readily welded — 78/100, better than 86% of refractory metal grades
R04251-SR properties
Typical room-temperature values for R04251-SR; 21 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-SR 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-SR has a yield strength of 260 MPa (37.7 ksi) and a tensile strength of 340 MPa (49.3 ksi) — weaker than 68% of refractory metal grades. Elongation at break is 18% and the elastic modulus is 100 GPa (14.5 Msi).
Thermal6
R04251-SR is rated for continuous service to 400°C (752 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 53% of refractory metal grades. Thermal expansion is 7.2 µm/m·K (4 µin/in·°F).
Electrical3
R04251-SR conducts electricity at 8.3 % 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-SR 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-SR's machinability is poor (32/100, better than 67% of refractory metal grades); weldability very good (78/100); formability good (65/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with R04251-SR
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-SR — frequently asked
What is R04251-SR used for?
R04251-SR 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-SR?
R04251-SR has a typical yield strength of 260 MPa (37.7 ksi) and a tensile strength of 340 MPa (49.3 ksi) — weaker than 68% of refractory metal grades. Strength varies by condition: see the 3 listed tempers.
Is R04251-SR easy to machine?
Not especially — machinability is rated poor (32/100, better than 67% 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-SR be welded?
Yes — weldability is rated very good (78/100). 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-SR?
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-SR 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-SR?
R04251-SR 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.