Refractory Metal Nuclear Grade Hafnium (R1)-HW (Hot Worked)
Heat-treated state
UNS R01001 · ASTM B737
Mill condition for heavy bar, billet and plate that will be machined or re-annealed by the fabricator.
Values for the HW condition
Other Nuclear Grade Hafnium (R1) tempers and conditions
Nuclear Grade Hafnium (R1) is listed in 5 conditions; see the grade overview at Nuclear Grade Hafnium (R1).
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
As cast | Melting-stock condition (consumable-arc or electron-beam ingot) sold for onward forging, rolling or alloy additions. | 220 | 400 | 16 | 150 HB | 5.2 % IACS |
ANNDefault Annealed | Standard stocked condition for control-rod bar, plate and sheet; best ductility and dimensional stability under irradiation. | 240 | 445 | 25 | 160 HB | — |
HWThis page Hot Worked | Mill condition for heavy bar, billet and plate that will be machined or re-annealed by the fabricator. | 285 | 480 | 20 | 175 HB | 5.2 % IACS |
Cold Worked + Stress Relieved | Compromise condition: keeps most cold-work strength while removing residual stress for tight-tolerance machined rod and tubing. | 480 | 600 | 12 | 19 HRC | 5 % IACS |
Cold worked | Pick when higher strength and straightness are needed in wire, thin strip or tubing and no post-weld ductility is required. | 550 | 650 | 8 | 22 HRC | 5 % IACS |
What is Nuclear Grade Hafnium (R1)-HW?
Nuclear Grade Hafnium (R1)-HW is Nuclear Grade Hafnium (R1) heat treated to HW — mill condition for heavy bar, billet and plate that will be machined or re-annealed by the fabricator. Nuclear Grade Hafnium (R1)-HW has a yield strength of 285 MPa (41.3 ksi) and a tensile strength of 480 MPa (69.6 ksi) — weaker than 63% of refractory metal grades. Elongation at break is 20% and the elastic modulus is 140 GPa (20.3 Msi). Nuclear Grade Hafnium (R1)-HW has a density of 13.31 g/cm³ (0.481 lb/in³), heavier than 77% of refractory metal grades. It melts at 2,233°C (4,051 °F). ANN is the default condition FabDigit quotes; HW is available on request or by drawing note.
Limitations
- Heavy — 13.31 g/cm³ (0.481 lb/in³), worse than 77% of refractory metal grades
- High embodied carbon — 95 kg CO₂/kg, worse than 75% of refractory metal grades
Nuclear Grade Hafnium (R1)-HW properties
Typical room-temperature values for Nuclear Grade Hafnium (R1)-HW; 22 are specific to this condition. Other listed values are Nuclear Grade Hafnium (R1) reference data and may not represent this condition. Bars are the position among refractory metal grades.
Physical3
Nuclear Grade Hafnium (R1)-HW has a density of 13.31 g/cm³ (0.481 lb/in³), heavier than 77% of refractory metal grades. It melts at 2,233°C (4,051 °F).
Mechanical12
Nuclear Grade Hafnium (R1)-HW has a yield strength of 285 MPa (41.3 ksi) and a tensile strength of 480 MPa (69.6 ksi) — weaker than 63% of refractory metal grades. Elongation at break is 20% and the elastic modulus is 140 GPa (20.3 Msi).
Thermal6
Nuclear Grade Hafnium (R1)-HW is rated for continuous service to 400°C (752 °F). It conducts heat at 23 W/m·K (13.3 BTU/hr·ft·°F), worse than 61% of refractory metal grades. Thermal expansion is 5.9 µm/m·K (3.28 µin/in·°F).
Electrical3
Nuclear Grade Hafnium (R1)-HW conducts electricity at 5.2 % IACS, worse than 55% of refractory metal grades.
Chemical & Environmental3
Corrosion resistance is excellent (87/100), better than 60% of refractory metal grades.
Sustainability2
Producing a kilogram of Nuclear Grade Hafnium (R1)-HW takes about 1,400 MJ of energy and emits 95 kg of CO₂ — more than 67% of refractory metal grades.
Manufacturability8
Nuclear Grade Hafnium (R1)-HW's machinability is poor (30/100, better than 54% of refractory metal grades); weldability good (60/100); formability fair (45/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Nuclear Grade Hafnium (R1)-HW
Is Nuclear Grade Hafnium (R1) easy to machine?
Machine like reactor-grade zirconium: slow speeds, heavy positive-rake sharp carbide tools, deep cuts and flood coolant — fine chips and dust are pyrophoric and must be kept wet and collected separately.
Can Nuclear Grade Hafnium (R1) be welded?
GTAW, plasma or EBW in a purged chamber or with full trailing/back shielding of high-purity argon or helium; keep oxygen, nitrogen and hydrogen out or the weld embrittles — bright silvery bead is the acceptance clue.
Can Nuclear Grade Hafnium (R1) be formed, bent or molded?
Bend and roll warm (150–400 °C) with generous radii because of the hcp texture; heavy reductions need intermediate vacuum anneals around 700–800 °C.
What surface finishes work on Nuclear Grade Hafnium (R1)?
Pickle in HNO₃–HF to remove oxide and forming lubricants, then rinse and passivate; avoid iron contamination and do not plate — the natural HfO₂ film is the corrosion barrier.
Nuclear Grade Hafnium (R1) 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 |
|---|---|---|
| Zrreactor-grade R1 limit; some buyers specify ≤2.0 % | ≤ 4.5 | 2 |
| O | ≤ 0.13 | 0.08 |
| C | ≤ 0.02 | 0.01 |
| N | ≤ 0.01 | 0 |
| H25 ppm max | ≤ 0 | 0 |
| Feoften specified with Cr as Fe+Cr | ≤ 0.08 | 0.03 |
| Cr | ≤ 0.01 | — |
| Ni | ≤ 0.01 | — |
| Ti | ≤ 0.01 | — |
| Al | ≤ 0.01 | — |
| Cu | ≤ 0.01 | — |
| Mo | ≤ 0.01 | — |
| Nb | ≤ 0.01 | — |
| W | ≤ 0.01 | — |
| U3 ppm max, nuclear purity | ≤ 3×10⁻⁴ | — |
| Hfbalance, hafnium plus permitted zirconium | balance | — |
Nuclear Grade Hafnium (R1)-HW — frequently asked
What is Nuclear Grade Hafnium (R1)-HW used for?
Nuclear Grade Hafnium (R1)-HW is typically used for reactor control rods, neutron absorber components, nuclear submarine reactor internals and control rod cladding. In short: strong neutron absorber metal; nuclear-purity, low-zirconium hafnium; control rod reference grade.
What is the yield strength of Nuclear Grade Hafnium (R1)-HW?
Nuclear Grade Hafnium (R1)-HW has a typical yield strength of 285 MPa (41.3 ksi) and a tensile strength of 480 MPa (69.6 ksi) — weaker than 63% of refractory metal grades. Strength varies by condition: see the 5 listed tempers.
Is Nuclear Grade Hafnium (R1)-HW easy to machine?
Not especially — machinability is rated poor (30/100, better than 54% of refractory metal grades). Machine like reactor-grade zirconium: slow speeds, heavy positive-rake sharp carbide tools, deep cuts and flood coolant — fine chips and dust are pyrophoric and must be kept wet and collected separately.
Can Nuclear Grade Hafnium (R1)-HW be welded?
Yes — weldability is rated good (60/100). GTAW, plasma or EBW in a purged chamber or with full trailing/back shielding of high-purity argon or helium; keep oxygen, nitrogen and hydrogen out or the weld embrittles — bright silvery bead is the acceptance clue.
What surface finishes work on Nuclear Grade Hafnium (R1)-HW?
Pickle in HNO₃–HF to remove oxide and forming lubricants, then rinse and passivate; avoid iron contamination and do not plate — the natural HfO₂ film is the corrosion barrier.
Can Nuclear Grade Hafnium (R1)-HW be formed, bent or molded?
Bend and roll warm (150–400 °C) with generous radii because of the hcp texture; heavy reductions need intermediate vacuum anneals around 700–800 °C.
What is the maximum service temperature of Nuclear Grade Hafnium (R1)-HW?
Nuclear Grade Hafnium (R1)-HW 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 Nuclear Grade Hafnium (R1)-ANN and Nuclear Grade Hafnium (R1)-CW?
ANN is the default condition — standard stocked condition for control-rod bar, plate and sheet; best ductility and dimensional stability under irradiation. CW: pick when higher strength and straightness are needed in wire, thin strip or tubing and no post-weld ductility is required. Yield strength is 240 MPa in ANN versus 550 MPa in CW.
Sources
- ASTM B737 — Hafnium and Hafnium Alloy Bar, Rod and Wire — ASTM International (2021)
- ASTM B776 — Hafnium and Hafnium Alloy Strip, Sheet and Plate — ASTM International (2021)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials — ASM International (1990)
- Hafnium metal — reactor grade technical data — ATI Wah Chang (2018)
- CRC Handbook of Chemistry and Physics — elemental properties of hafnium — CRC Press (2022)
- Hafnium metal price series / — USGS MCS & SMM (2025)
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.