R04251 Nb-1Zr Niobium Fittings – Plate-Formed & Fabricated (ASTM B393)
What are R04251 plate-formed niobium fittings?
They are caps, stub ends, large-bore reducers, segmented elbows, headers and other fabricated fittings made from ASTM B393 sheet and plate in UNS R04251 – reactor-grade niobium-1% zirconium (Nb-1Zr, ASTM Type 3). Forming from plate is the practical route for sizes and shapes that cannot be made from tube or bar.
Note on specifications: ASTM B880 is a check-analysis standard for nickel, nickel alloys and cobalt alloys – it does not cover niobium or fittings. The correct material standard for R04251 sheet and plate is ASTM B393.
R04251 Plate-Formed Fittings – Quick Facts
- Grade: UNS R04251, Nb-1Zr reactor grade (Zr 0.8–1.2%)
- Raw material: ASTM B393 sheet (0.13–4.76 mm) and plate (over 4.76 mm)
- Fitting types: caps, stub ends, large-bore and eccentric reducers, segmented elbows, tees and headers, flanged nozzles
- Joining: TIG or electron-beam welding in high-purity argon chamber or vacuum
- Condition: annealed in vacuum, pickled and clean
- Certificate: EN 10204 3.1 with interstitial (C, O, N, H) analysis
ASC LLP, Mumbai, supplies R04251 fittings formed from plate, from tube and from bar. For an overview of both Nb-1Zr grades see Nb-1Zr niobium fittings.
R04251 Chemical Composition
| Element (max %, unless range) | R04251 (reactor grade) | R04261 (commercial grade) |
| Zirconium (Zr) | 0.8 – 1.2 | 0.8 – 1.2 |
| Oxygen (O) | 0.015 | 0.025 |
| Carbon (C) | 0.01 | 0.01 |
| Nitrogen (N) | 0.01 | 0.01 |
| Hydrogen (H) | 0.0015 | 0.0015 |
| Tantalum (Ta) | 0.1 | 0.5 |
| Tungsten (W) | 0.03 | 0.05 |
| Molybdenum (Mo) | 0.010 | 0.050 |
| Iron (Fe) | 0.005 | 0.01 |
| Titanium (Ti) | 0.02 | 0.03 |
| Niobium (Nb) | Remainder | Remainder |
Limits per ASTM B392 / B393 / B394 (same chemistry for all three product forms). R04251 contains only 0.1% tantalum maximum – not 10–15%.
Mechanical Properties – ASTM B393
| Grade (sheet / plate) | Tensile strength (min) | 0.2% yield strength (min) | Elongation (min) |
| R04251 / R04261 (Nb-1Zr) | 195 MPa (28 ksi) | 125 MPa (18 ksi) | 20% |
| R04200 / R04210 (pure Nb) | 125 MPa (18 ksi) | 73 MPa (10.5 ksi) | 20% |
Minimum tensile requirements for sheet and plate per ASTM B393. Welded seams in fabricated fittings are annealed in vacuum to restore ductility.
Plate-Formed R04251 Fitting Types
| Fitting type | Plate-forming / fabrication route |
| Caps | Deep-drawn or spun from B393 sheet / plate |
| Stub ends | Formed from plate or machined from plate rings |
| Large-bore reducers | Rolled cone from plate, longitudinal weld |
| Segmented (mitred) elbows | Rolled and welded segments from plate |
| Tees, laterals & headers | Fabricated from rolled plate with welded branches |
| Flanged nozzles & transitions | Fabricated to drawing from plate |
Small-bore elbows, tees and reducers are normally formed from B394 tube; socket-weld and threaded fittings are machined from B392 bar.
R04251 Plate-Formed Fittings Specifications
| Item | Details |
| Product | R04251 Nb-1Zr niobium fittings formed or fabricated from sheet and plate |
| Material standard | ASTM B393 (strip, sheet, plate) |
| Sheet thickness | 0.005 – 0.1875 in (0.13 – 4.76 mm) |
| Plate thickness | Over 0.1875 in (4.76 mm) |
| Sizes | To drawing – including large bores not available as tube |
| Welding | TIG / EB in argon chamber or vacuum; weld procedure to customer code |
| Testing | Chemical incl. interstitials, dimensional, visual, dye penetrant; radiography of seams on request |
| Certificate | EN 10204 3.1; third-party inspection on request |
Welding & Fabrication Notes
- Atmosphere: weld only in a high-purity argon chamber or vacuum – oxygen, nitrogen or hydrogen pick-up embrittles Nb-1Zr.
- Cleanliness: degrease and pickle plate before forming and welding; handle with clean gloves.
- Forming: Nb-1Zr is ductile and can be cold-formed, spun and deep-drawn; anneal between heavy forming steps.
- Annealing: vacuum or inert-gas anneal after welding – never in air.
Our R04251 / Nb-1Zr Fittings Range
| Page | What it covers |
| Nb-1Zr niobium fittings | Overview of both Nb-1Zr grades (R04251 and R04261) |
| R04251 fittings from tube | Butt-weld elbows, tees and reducers formed from ASTM B394 tube |
| R04251 fittings from bar | Socket-weld, threaded and machined fittings from ASTM B392 bar |
| This page | Caps, stub ends, large-bore and fabricated fittings from ASTM B393 sheet and plate |
Physical Properties of Nb-1Zr
| Property | Value (approx.) |
| Density | 8.6 g/cm³ |
| Crystal structure | Body-centred cubic |
| Coefficient of thermal expansion | ≈ 7 µm/m·°C |
| Oxidation in air | Above about 400 °C – use hot only in vacuum, inert gas or liquid metal |
Applications of R04251 Plate-Formed Fittings
| Industry | Applications |
| Nuclear & space power | Liquid-metal loop headers, vessel caps and large-bore transitions |
| Research & fusion | Vacuum and liquid-metal experimental vessels and manifolds |
| Vacuum furnaces | Hot-zone enclosures, shields and flanged nozzles |
| Chemical processing | Fabricated acid-service components needing more strength than pure niobium |
Nb-1Zr is not used for jet-engine or oil-and-gas parts; it is chosen for high-purity, high-temperature service in vacuum, inert gas or liquid metal.
Why Buy R04251 Fittings from ASC LLP?
- Correct material: R04251 sheet and plate to ASTM B393 with 3.1 certificates showing zirconium and interstitials.
- All three routes: plate-formed, tube-formed and bar-machined fittings from one supplier.
- Matching parts: R04251 flanges and R04251 fasteners; see all niobium fittings.
- Drawings and one-off parts welcome, with clean export packing.
Send drawing, thickness and quantity to sales@amardeepsteel.com or call 022-67439130.
Frequently Asked Questions – R04251 Plate-Formed Fittings
Does ASTM B880 cover niobium fittings?
No. ASTM B880 sets check-analysis limits for nickel, nickel alloys and cobalt alloys. Niobium and Nb-1Zr sheet and plate are covered by ASTM B393, tube by ASTM B394 and bar by ASTM B392.
What is R04251?
UNS R04251 is reactor-grade niobium-1% zirconium alloy (ASTM Type 3), with 0.8–1.2% zirconium and tight limits on oxygen (0.015%), tantalum (0.1%) and other impurities.
Which fittings are made from niobium plate?
Caps, stub ends, large-bore and eccentric reducers, segmented elbows, fabricated tees and headers, and flanged nozzles are commonly formed or fabricated from ASTM B393 niobium sheet and plate.
What is the strength of R04251 sheet and plate?
ASTM B393 requires Nb-1Zr (R04251 / R04261) sheet and plate to have a minimum tensile strength of 195 MPa (28 ksi), yield strength of 125 MPa (18 ksi) and elongation of 20%.
How are Nb-1Zr plate fittings welded?
Nb-1Zr is welded by TIG or electron-beam welding in a high-purity argon chamber or vacuum, then annealed in vacuum or inert gas. Welding in open air would embrittle the joint.
Global Reach
ASC LLP supplies niobium, tantalum and other refractory-metal products to nuclear, research and high-temperature industries worldwide, with secure packing and full documentation. Buyers in the USA, Europe, the Middle East and Asia rely on our R04251 Nb-1Zr niobium fittings for certified material and traceability.
Countries We Export To
UNITED STATES, EUROPE, UK, UAE, SAUDI ARABIA, OMAN, KUWAIT, JORDAN, QATAR, INDONESIA, MALAYSIA, BRAZIL, SPAIN, ITALY, FRANCE, GERMANY, BAHRAIN, SRI LANKA, AZERBAIJAN, AUSTRALIA, AUSTRIA, PHILIPPINES, TURKEY, RUSSIA, IRAN, IRAQ, CANADA, KOREA, JAPAN, YEMEN, FINLAND, ZIMBABWE, HUNGARY, PORTUGAL, VIETNAM, MOROCCO, THAILAND, SOUTH AFRICA, MEXICO, SINGAPORE, GREECE, KUWAIT, POLAND, NEW ZEALAND, SWEDEN, SWITZERLAND, BELGIUM, BHUTAN, BANGLADESH, TAIWAN, ROMANIA, CAMBODIA, KAZAKHSTAN, AFGHANISTAN.
