Refractory Metal Zr 705-BQA (Beta quenched and aged)
Precip hard
UNS R60705 · ASTM B550/B551 Grade 705
Specialty high-strength condition for springs, shafts and pressure-tube-type parts; precipitation of β-Nb raises strength but lowers ductility and is not covered by the standard B550 mechanical table.
Values for the BQA condition
Other Zr 705 tempers and conditions
Zr 705 is listed in 4 conditions; see the grade overview at Zr 705.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANNDefault Annealed | Standard stocked condition for plate, sheet, bar and pipe in chemical-process equipment; best ductility/weld-repair behaviour at full corrosion resistance. | 450 | 620 | 20 | 200 HB | — |
Hot worked / as-forged | Heavy forgings, valve bodies and thick bar supplied hot worked where full annealing of the section is not practical. | 490 | 650 | 18 | 210 HB | 3.1 % IACS |
Cold worked and stress relieved | Choose for bar, wire, fasteners and thin tube where higher strength and better dimensional stability are needed and cold formability is not required. | 620 | 760 | 13 | 25 HRC | — |
BQAThis page Beta quenched and aged | Specialty high-strength condition for springs, shafts and pressure-tube-type parts; precipitation of β-Nb raises strength but lowers ductility and is not covered by the standard B550 mechanical table. | 760 | 900 | 10 | 32 HRC | 3 % IACS |
What is Zr 705-BQA?
Zr 705-BQA is Zr 705 in the BQA condition — specialty high-strength condition for springs, shafts and pressure-tube-type parts; precipitation of β-Nb raises strength but lowers ductility and is not covered by the standard B550 mechanical table. Zr 705-BQA has a yield strength of 760 MPa (110 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 88% of refractory metal grades. Elongation at break is 10% and the elastic modulus is 98 GPa (14.2 Msi). Zr 705-BQA has a density of 6.64 g/cm³ (0.24 lb/in³), lighter than 63% of refractory metal grades. It melts at 1,840°C (3,344 °F). ANN is the default condition FabDigit quotes; BQA is available on request or by drawing note.
Advantages
- High strength — 760 MPa (110 ksi), better than 88% of refractory metal grades
Limitations
- Low stiffness — 98 GPa (14.2 Msi), worse than 84% of refractory metal grades
- Low electrical conductivity — 3 % IACS, worse than 81% of refractory metal grades
- Limited formability — 15/100, worse than 80% of refractory metal grades
- Poor heat conductor — 16.8 W/m·K (9.71 BTU/hr·ft·°F), worse than 79% of refractory metal grades
Zr 705-BQA properties
Typical room-temperature values for Zr 705-BQA; 22 are specific to this condition. Other listed values are Zr 705 reference data and may not represent this condition. Bars are the position among refractory metal grades.
Physical2
Zr 705-BQA has a density of 6.64 g/cm³ (0.24 lb/in³), lighter than 63% of refractory metal grades. It melts at 1,840°C (3,344 °F).
Mechanical16
Zr 705-BQA has a yield strength of 760 MPa (110 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 88% of refractory metal grades. Elongation at break is 10% and the elastic modulus is 98 GPa (14.2 Msi).
Thermal6
Zr 705-BQA is rated for continuous service to 400°C (752 °F). It conducts heat at 16.8 W/m·K (9.71 BTU/hr·ft·°F), worse than 79% of refractory metal grades. Thermal expansion is 6.3 µm/m·K (3.5 µin/in·°F).
Electrical3
Zr 705-BQA conducts electricity at 3 % IACS, worse than 81% of refractory metal grades.
Chemical & Environmental3
Corrosion resistance is excellent (90/100), better than 75% of refractory metal grades.
Sustainability4
Producing a kilogram of Zr 705-BQA takes about 1,400 MJ of energy and emits 85 kg of CO₂ — more than 67% of refractory metal grades. Typical recycled content is 25%.
Manufacturability8
Zr 705-BQA's machinability is poor (28/100, worse than 58% of refractory metal grades); weldability fair (45/100); formability poor (15/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Zr 705-BQA
Is Zr 705 easy to machine?
Machine like austenitic stainless but slower: sharp uncoated carbide, positive rake, heavy rigid setups, generous chlorine-free flood coolant; fine chips are pyrophoric so keep them wet and collect separately.
Can Zr 705 be welded?
GTAW/EBW with high-purity argon or helium and full trailing/back purge (or chamber welding); target weld-zone hardness rise <30 HV and keep oxygen/nitrogen pickup minimal — no flux, no air exposure above ~300 °C.
Can Zr 705 be formed, bent or molded?
Cold formability is limited (bend radius ≥3–5t); warm forming at 200–400 °C and generous radii are preferred, and springback is high due to the low modulus.
What surface finishes work on Zr 705?
Pickle in HNO₃/HF to remove oxide and grinding smear before service; can be bead blasted or polished, and anodic coloring/oxide films are used for galling and ID marking.
Zr 705 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 |
|---|---|---|
| Nbcolumbium (niobium), principal alloying addition | 2 – 3 | 2.5 |
| Hfhafnium is not separated in industrial (non-nuclear) grades | ≤ 4.5 | 1 |
| Fe+Cr | ≤ 0.2 | 0.1 |
| O | ≤ 0.18 | 0.11 |
| C | ≤ 0.05 | 0.02 |
| N | ≤ 0.03 | 0.01 |
| H | ≤ 0.01 | 0 |
| Zr+Hfbalance, Zr+Hf min 95.5% per ASTM B550/B551 | ≥ 95.5 (balance) | — |
Zr 705-BQA — frequently asked
What is Zr 705-BQA used for?
Zr 705-BQA is typically used for high-strength process piping, pressure vessel components and fasteners in corrosive service. In short: strongest wrought zirconium; nb-alloyed corrosion grade; fastener-capable zirconium.
What is the yield strength of Zr 705-BQA?
Zr 705-BQA has a typical yield strength of 760 MPa (110 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 88% of refractory metal grades. Strength varies by condition: see the 4 listed tempers.
Is Zr 705-BQA easy to machine?
Not especially — machinability is rated poor (28/100, worse than 58% of refractory metal grades). Machine like austenitic stainless but slower: sharp uncoated carbide, positive rake, heavy rigid setups, generous chlorine-free flood coolant; fine chips are pyrophoric so keep them wet and collect separately.
Can Zr 705-BQA be welded?
With care — weldability is rated fair (45/100). GTAW/EBW with high-purity argon or helium and full trailing/back purge (or chamber welding); target weld-zone hardness rise <30 HV and keep oxygen/nitrogen pickup minimal — no flux, no air exposure above ~300 °C.
What surface finishes work on Zr 705-BQA?
Pickle in HNO₃/HF to remove oxide and grinding smear before service; can be bead blasted or polished, and anodic coloring/oxide films are used for galling and ID marking.
Can Zr 705-BQA be formed, bent or molded?
Cold formability is limited (bend radius ≥3–5t); warm forming at 200–400 °C and generous radii are preferred, and springback is high due to the low modulus.
What is the maximum service temperature of Zr 705-BQA?
Zr 705-BQA 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 Zr 705-ANN and Zr 705-BQA?
ANN is the default condition — standard stocked condition for plate, sheet, bar and pipe in chemical-process equipment; best ductility/weld-repair behaviour at full corrosion resistance. BQA: specialty high-strength condition for springs, shafts and pressure-tube-type parts; precipitation of β-Nb raises strength but lowers ductility and is not covered by the standard B550 mechanical table. Yield strength is 450 MPa in ANN versus 760 MPa in BQA.
Sources
- ASTM B550/B550M Zirconium and Zirconium Alloy Bar and Wire — ASTM International (2018)
- ASTM B551/B551M Zirconium and Zirconium Alloy Strip, Sheet and Plate — ASTM International (2018)
- ASTM B523 / B658 Zirconium Alloy Tube and Pipe — ASTM International (2018)
- Zirconium Alloys 702/704/705 Technical Data — ATI Wah Chang (2016)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys (Zirconium) — ASM International (1990)
- ASM Handbook Vol. 13B — Corrosion: Materials (Zirconium) — ASM International (2005)
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.