Refractory Metal Zircaloy-4-BQ (Β-Q)
Heat-treated state
UNS R60804 · ASTM B350/B811
Used for guide tube/end-plug stock and nodular-corrosion resistance; fine Widmanstätten structure with uniformly dispersed Zr(Fe,Cr)2 precipitates.
Values for the BQ condition
Other Zircaloy-4 tempers and conditions
Zircaloy-4 is listed in 5 conditions; see the grade overview at Zircaloy-4.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
RXADefault Fully recrystallization annealed | Standard stocked condition for plate, sheet, bar and structural components; maximum ductility and creep-friendly isotropy. | 330 | 480 | 28 | 89 HRB | — |
BQThis page Β-Q | Used for guide tube/end-plug stock and nodular-corrosion resistance; fine Widmanstätten structure with uniformly dispersed Zr(Fe,Cr)2 precipitates. | 380 | 520 | 18 | 13 HRC | 2.4 % IACS |
Partially recrystallized annealed | Intermediate temper for cladding and spacer strip where a balance of strength, creep and corrosion behaviour is wanted. | 430 | 560 | 20 | 14 HRC | 2.5 % IACS |
CWSR / SRA | Standard condition for PWR fuel cladding and guide tubes (ASTM B811); highest strength and best creep-collapse resistance. | 540 | 640 | 14 | 97 HRB | — |
Cold worked | Intermediate mill condition or springy strip/wire use; highest strength but low ductility and high residual stress. | 670 | 740 | 9 | 24 HRC | 2.4 % IACS |
What is Zircaloy-4-BQ?
Zircaloy-4-BQ is Zircaloy-4 heat treated to BQ — used for guide tube/end-plug stock and nodular-corrosion resistance; fine Widmanstätten structure with uniformly dispersed Zr(Fe,Cr)2 precipitates. Zircaloy-4-BQ has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 520 MPa (75.4 ksi) — stronger than 60% of refractory metal grades. Elongation at break is 18% and the elastic modulus is 99 GPa (14.4 Msi). Zircaloy-4-BQ has a density of 6.56 g/cm³ (0.237 lb/in³), lighter than 71% of refractory metal grades. It melts at 1,760°C (3,200 °F). RXA is the default condition FabDigit quotes; BQ is available on request or by drawing note.
Limitations
- Poor heat conductor — 13 W/m·K (7.51 BTU/hr·ft·°F), worse than 95% of refractory metal grades
- Low electrical conductivity — 2.4 % IACS, worse than 88% of refractory metal grades
- Low stiffness — 99 GPa (14.4 Msi), worse than 79% of refractory metal grades
Zircaloy-4-BQ properties
Typical room-temperature values for Zircaloy-4-BQ; 23 are specific to this condition. Other listed values are Zircaloy-4 reference data and may not represent this condition. Bars are the position among refractory metal grades.
Physical3
Zircaloy-4-BQ has a density of 6.56 g/cm³ (0.237 lb/in³), lighter than 71% of refractory metal grades. It melts at 1,760°C (3,200 °F).
Mechanical15
Zircaloy-4-BQ has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 520 MPa (75.4 ksi) — stronger than 60% of refractory metal grades. Elongation at break is 18% and the elastic modulus is 99 GPa (14.4 Msi).
Thermal6
Zircaloy-4-BQ is rated for continuous service to 400°C (752 °F). It conducts heat at 13 W/m·K (7.51 BTU/hr·ft·°F), worse than 95% of refractory metal grades. Thermal expansion is 6 µm/m·K (3.33 µin/in·°F).
Electrical3
Zircaloy-4-BQ conducts electricity at 2.4 % IACS, worse than 88% of refractory metal grades.
Chemical & Environmental3
Corrosion resistance is excellent (90/100), better than 75% of refractory metal grades.
Sustainability4
Producing a kilogram of Zircaloy-4-BQ takes about 1,400 MJ of energy and emits 90 kg of CO₂ — more than 67% of refractory metal grades. Typical recycled content is 10%.
Manufacturability8
Zircaloy-4-BQ's machinability is poor (27/100, worse than 60% of refractory metal grades); weldability very good (70/100); formability fair (45/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Zircaloy-4-BQ
Is Zircaloy-4 easy to machine?
Machine like CP-titanium: sharp, positive-rake carbide, slow speed, heavy flood coolant, no dwelling — chips are pyrophoric, so collect wet and never dry-grind.
Can Zircaloy-4 be welded?
GTAW, plasma or EB weld only under high-purity argon/helium chamber or full trailing plus back purge; any O/N/H pickup embrittles the weld, and no filler other than matching Zr is acceptable.
Can Zircaloy-4 be formed, bent or molded?
Cold form annealed sheet with generous radii (≥2t) allowing for strong crystallographic texture and springback; hot work 700–800 °C, and tube reduce by cold pilgering with intermediate 550–600 °C vacuum anneals.
What surface finishes work on Zircaloy-4?
Pickle in HNO3/HF then rinse and passivate/autoclave to grow a protective black ZrO2 film; avoid iron contamination from steel tooling, and use dedicated wire brushes and abrasives.
Zircaloy-4 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 |
|---|---|---|
| Snsolid-solution strengthener | 1.2 – 1.7 | 1.45 |
| FeFe+Cr must be 0.28–0.37 | 0.18 – 0.24 | 0.21 |
| Crforms Zr(Fe,Cr)2 precipitates | 0.07 – 0.13 | 0.1 |
| Ospecified/ordered range; main strengthener | 0.09 – 0.16 | 0.12 |
| Nideliberately restricted to limit hydrogen pickup | ≤ 0.01 | — |
| Hfnuclear-grade limit (neutron absorber) | ≤ 0.01 | — |
| C | ≤ 0.03 | — |
| N | ≤ 0.01 | — |
| Si | ≤ 0.01 | — |
| Al | ≤ 0.01 | — |
| B | ≤ 5×10⁻⁵ | — |
| Cd | ≤ 5×10⁻⁵ | — |
| Zrbalance Zr (+ residual Hf within limit) | balance | — |
Zircaloy-4-BQ — frequently asked
What is Zircaloy-4-BQ used for?
Zircaloy-4-BQ is typically used for PWR fuel cladding, guide tubes and fuel assembly spacers. In short: standard PWR cladding alloy; lower hydrogen pickup; nickel-free Zircaloy-2.
What is the yield strength of Zircaloy-4-BQ?
Zircaloy-4-BQ has a typical yield strength of 380 MPa (55.1 ksi) and a tensile strength of 520 MPa (75.4 ksi) — stronger than 60% of refractory metal grades. Strength varies by condition: see the 5 listed tempers.
Is Zircaloy-4-BQ easy to machine?
Not especially — machinability is rated poor (27/100, worse than 60% of refractory metal grades). Machine like CP-titanium: sharp, positive-rake carbide, slow speed, heavy flood coolant, no dwelling — chips are pyrophoric, so collect wet and never dry-grind.
Can Zircaloy-4-BQ be welded?
Yes — weldability is rated very good (70/100). GTAW, plasma or EB weld only under high-purity argon/helium chamber or full trailing plus back purge; any O/N/H pickup embrittles the weld, and no filler other than matching Zr is acceptable.
What surface finishes work on Zircaloy-4-BQ?
Pickle in HNO3/HF then rinse and passivate/autoclave to grow a protective black ZrO2 film; avoid iron contamination from steel tooling, and use dedicated wire brushes and abrasives.
Can Zircaloy-4-BQ be formed, bent or molded?
Cold form annealed sheet with generous radii (≥2t) allowing for strong crystallographic texture and springback; hot work 700–800 °C, and tube reduce by cold pilgering with intermediate 550–600 °C vacuum anneals.
What is the maximum service temperature of Zircaloy-4-BQ?
Zircaloy-4-BQ 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 Zircaloy-4-RXA and Zircaloy-4-CW?
RXA is the default condition — standard stocked condition for plate, sheet, bar and structural components; maximum ductility and creep-friendly isotropy. CW: intermediate mill condition or springy strip/wire use; highest strength but low ductility and high residual stress. Yield strength is 330 MPa in RXA versus 670 MPa in CW.
Sources
- ASTM B350/B350M — Zirconium and Zirconium Alloy Ingots for Nuclear Application — ASTM International (2022)
- ASTM B351 / B352 / B353 — Zr alloy bar/wire, sheet-strip-plate, and tubing for nuclear application — ASTM International (2022)
- ASTM B811 — Wrought Zirconium Alloy Seamless Tubes for Nuclear Reactor Fuel Cladding — ASTM International (2021)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys (Zirconium and Hafnium) — ASM International (1990)
- MATPRO / NUREG-CR Zircaloy thermophysical and mechanical property correlations — US NRC / INL (2003)
- Zircaloy-4 alloy data sheet — ATI Wah Chang (2018)
- IAEA TECDOC — Waterside corrosion and properties of zirconium alloy fuel cladding — IAEA (1998)
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.