Bar and Rod
Plate and Sheet
Strip
Pipe and Tube
Wire
Welding
Powder Material
Cast Products
Forged Products
Fittings
Fastening
Round Bar:
φ2–500 mm, 1–6 m length
Flat/Square Bar:
4–100 mm thickness/width
Hex Bar:
A/F 3–100 mm
Hollow Bar:
OD 20–300 mm
Sheet:
0.3–6 mm thickness
Medium Plate:
6–25 mm thickness
Heavy Plate:
25–100 mm thickness
Standard Strip:
0.05–3 mm thick,
10–600 mm wide
Precision strip:
0.01–0.5 mm thick,
tight tolerance ±0.005 mm
Foil:
0.005–0.1 mm thick
Seamless Tube:
OD 6–450 mm,
WT 1–50 mm,
1–12 m length
Welded Tube:
OD 10–600 mm,
WT 1–20 mm
Capillary Tube:
OD 1–10 mm,
WT 0.1–2 mm
Wire Form:
Cold Drawn Wire,
Bright Wire,
Spring Wire,
Fine Wire,
Ultra-fine Wire
General Diameter:
φ0.1–10 mm
Coil Weight:
50–500 kg,
customizable tolerance
Solid Wire:
φ0.8–4.0 mm
Flux-cored Wire:
φ1.2–4.0 mm
Welding Rod:
φ2.0–5.0 mm
Powder Form:
AM 3D Printing Powder,
Spherical Powder,
Gas-atomized Powder,
Water-atomized Powder
Particle Size:
10–150 μm
Sphericity:
≥90% for AM grade
Cast Ingot:
φ200–800 mm
Precision Casting:
min wall 0.5 mm
Cast Pipe:
OD 100–600 mm,
WT 10–50 mm
Forged Bar:
Φ35–500 mm
Forged Ring:
OD 200–2000 mm
Forging Weight:
1–5000 kg
Fittings Form:
Elbow, Tee, Reducer, Flange, Cap, Outlet, Lap Joint
Size range:
1/2''–24'' (DN15–DN600)
Wall thickness:
Sch10–Sch160, STD, XS, XXS
Pressure Class:
150–2500 LB
Fastening Form:
Bolt, Nut, Screw, Stud, Washer, Pin, Rivet
Metric: M3–M64
Imperial: #4–2.5''
Length: 6–500 mm
R04251 is a reactor grade niobium alloy containing about 1% zirconium (Type 3). This datasheet presents the material within the American (ASTM / ASME / UNS) standard system.
Niobium (formerly called columbium) is a refractory metal with a high melting point, low density for a refractory metal, excellent ductility and a low thermal-neutron capture cross-section that makes the reactor grade attractive for nuclear service. R04251 contains a nominal 1% zirconium addition that raises strength and elevated-temperature performance relative to unalloyed niobium while retaining good formability and weldability. It offers excellent corrosion resistance in many liquid metals and chemical media, although like all refractory metals it oxidises in air at elevated temperature and requires protection or inert/vacuum service. It is supplied in the annealed condition.
Typical applications include nuclear-reactor components, chemical-process equipment, superconductor substrates, and high-temperature and electronic uses.
| Property | Value | Unit |
|---|---|---|
| Density | 8.57 | g/cm³ |
| Melting point | 2468 | °C |
| Elastic modulus | 105 | GPa |
| Coefficient of thermal expansion (20–100 °C) | 7.3 | µm/m·°C |
| Thermal conductivity (20 °C) | 53.7 | W/m·K |
| Specific heat (20 °C) | 265 | J/kg·K |
| Structure | Body-centred cubic (BCC) | — |
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Niobium | Nb | Balance | — | Base element |
| Zirconium | Zr | 0.80 | 1.20 | Alloying; strength, high-temperature |
| Tantalum | Ta | — | 0.10 | Residual impurity |
| Tungsten | W | — | 0.05 | Residual impurity |
| Oxygen | O | — | 0.015 | Interstitial impurity |
| Carbon | C | — | 0.010 | Interstitial impurity |
| Nitrogen | N | — | 0.010 | Interstitial impurity |
| Hydrogen | H | — | 0.0015 | Interstitial impurity |
Annealed condition, typical values for ASTM B393 R04251.
| Condition | Property | Value |
|---|---|---|
| Annealed | Tensile strength (UTS) | ≥185 MPa (27 ksi) |
| Annealed | 0.2% yield strength | ≥105 MPa (15 ksi) |
| Annealed | Elongation at break | ≥25 % |
| Cold-worked | Tensile strength (UTS) | higher; less ductile |
| — | Elastic modulus | 105 GPa |
Confirm against the mill test report. The 1% zirconium addition raises strength over unalloyed niobium; cold work raises it further.
| Environment | Performance | Notes |
|---|---|---|
| Liquid alkali metals | Excellent | Used in nuclear / heat-transfer service |
| Many acids (non-fluoride) | Excellent | Stable passive oxide |
| Atmospheric / general | Good | Stable at room temperature |
| Oxidizing atmospheres (>400 °C) | Poor | Oxidises in air; must be protected |
| Hydrofluoric acid / hot alkalis | Poor | Attacked |
Niobium resists many acids and liquid metals through a stable surface oxide, but oxidises in air at elevated temperature and is attacked by hydrofluoric acid and hot concentrated alkalis.
A refractory metal; not hardenable by precipitation. Properties are governed by working and annealing.
Anneal Anneal in vacuum or a high-purity inert atmosphere at approximately 980–1200 °C to recrystallise and restore ductility after cold work. Avoid oxygen, nitrogen and hydrogen pickup, which embrittle the metal.
Excellent weldability by inert-gas and high-vacuum processes; the weld and hot metal must be fully shielded from air, because oxygen, nitrogen and hydrogen pickup cause embrittlement.
| Welding Process | Applicability | Notes |
|---|---|---|
| GTAW / TIG | Excellent | High-purity inert shielding or chamber |
| EBW (vacuum) | Excellent | Preferred for clean welds |
| Resistance / spot | Good | — |
Weld under high-purity shielding or in vacuum; protect the cooling weld from atmospheric contamination.
Machining Guidelines
| Parameter | Recommendation |
|---|---|
| Machinability | Soft and gummy; sharp tooling, positive rake |
| Tendency | Galls and smears; avoid built-up edge |
| Coolant | Ample non-chlorinated coolant |
Forming Processes
| Process | Notes |
|---|---|
| Cold forming | Excellent; very ductile when annealed |
| Hot forming | Performed hot under protection from oxidation |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Nuclear | Reactor components | Low neutron capture + corrosion resistance |
| Chemical process | Linings, vessels, heat exchangers | Acid corrosion resistance |
| Superconductors | Substrate / cladding | Ductility + purity |
| Electronics / aerospace | Capacitors, high-temperature parts | Refractory performance |
| Product Form | ASTM Standard | Notes |
|---|---|---|
| Strip, sheet and plate | ASTM B393 | Type 3 (R04251) |
| Bar, rod and wire | ASTM B392 | Type 3 (R04251) |
| Seamless and welded tube | ASTM B394 | Type 3 (R04251) |
| Ingot | ASTM B391 | Type 3 (R04251) |
Reactor grade niobium-1% zirconium alloy (Type 3). UNS R04251.
| UNS | Composition | Grade | Best Used For |
|---|---|---|---|
| R04200 | Unalloyed Nb | Type 1, reactor grade | Reactor-grade niobium; nuclear service |
| R04210 | Unalloyed Nb | Type 2, commercial grade | Commercial unalloyed niobium |
| R04251 | Nb-1Zr | Type 3, reactor grade | Reactor-grade niobium-zirconium alloy; nuclear, high-temperature |
| R04261 | Nb-1Zr | Type 4, commercial grade | Commercial niobium-zirconium alloy |
| R04295 | Nb-10Hf-1Ti | C-103 | High-temperature aerospace/propulsion alloy |
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