Refractory Metal Zr 706-HW (Hot worked / as-forged)
Heat-treated state
UNS R60706 · ASTM B550/B551 Grade 706
Economical condition for heavy forged bar, flanges and valve bodies where a full anneal is not specified.
Values for the HW condition
Other Zr 706 tempers and conditions
Zr 706 is listed in 4 conditions; see the grade overview at Zr 706.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
HWThis page Hot worked / as-forged | Economical condition for heavy forged bar, flanges and valve bodies where a full anneal is not specified. | 390 | 545 | 21 | 176 HB | 3.1 % IACS |
AnnealedDefault recrystallization annealed (ASTM B550/B551/B523 standard condition) | Default stocked condition for plate, sheet, bar and tube; best ductility and formability with full corrosion resistance. | 400 | 550 | 24 | 180 HB | — |
Cold worked and stress relieved | Pick for tube and bar needing higher strength and stiffness-limited sections; ductility and formability are reduced. | 550 | 660 | 14 | 96 HRB | — |
Solution treated and aged | Special-order high-strength condition for fasteners and small structural parts; corrosion resistance and toughness drop and it is rarely used for pressure vessels. | 750 | 900 | 10 | 32 HRC | — |
What is Zr 706-HW?
Zr 706-HW is Zr 706 heat treated to HW — economical condition for heavy forged bar, flanges and valve bodies where a full anneal is not specified. Zr 706-HW has a yield strength of 390 MPa (56.6 ksi) and a tensile strength of 545 MPa (79 ksi) — stronger than 61% of refractory metal grades. Elongation at break is 21% and the elastic modulus is 97 GPa (14.1 Msi). Zr 706-HW 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). Annealed is the default condition FabDigit quotes; HW is available on request or by drawing note.
Advantages
- Easy to machine — 40/100, better than 93% of refractory metal grades
- Tough — resists crack growth — 62 MPa·√m (56.4 ksi·√in), better than 80% of refractory metal grades
Limitations
- Low stiffness — 97 GPa (14.1 Msi), worse than 91% of refractory metal grades
- Low electrical conductivity — 3.1 % IACS, worse than 78% of refractory metal grades
- Poor heat conductor — 17.1 W/m·K (9.88 BTU/hr·ft·°F), worse than 76% of refractory metal grades
Zr 706-HW properties
Typical room-temperature values for Zr 706-HW; 22 are specific to this condition. Other listed values are Zr 706 reference data and may not represent this condition. Bars are the position among refractory metal grades.
Physical3
Zr 706-HW 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 706-HW has a yield strength of 390 MPa (56.6 ksi) and a tensile strength of 545 MPa (79 ksi) — stronger than 61% of refractory metal grades. Elongation at break is 21% and the elastic modulus is 97 GPa (14.1 Msi).
Thermal6
Zr 706-HW is rated for continuous service to 400°C (752 °F). It conducts heat at 17.1 W/m·K (9.88 BTU/hr·ft·°F), worse than 76% of refractory metal grades. Thermal expansion is 6 µm/m·K (3.33 µin/in·°F).
Electrical3
Zr 706-HW conducts electricity at 3.1 % IACS, worse than 78% of refractory metal grades.
Chemical & Environmental3
Corrosion resistance is excellent (86/100), better than 59% of refractory metal grades.
Sustainability4
Producing a kilogram of Zr 706-HW takes about 1,300 MJ of energy and emits 78 kg of CO₂ — more than 57% of refractory metal grades. Typical recycled content is 20%.
Manufacturability8
Zr 706-HW's machinability is fair (40/100, better than 93% of refractory metal grades); weldability very good (73/100); formability good (55/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Zr 706-HW
Is Zr 706 easy to machine?
Machine like a gummy austenitic stainless — sharp carbide tools, heavy positive rake, slow speed with high feed and flood coolant; never let fine chips accumulate dry (pyrophoric).
Can Zr 706 be welded?
GTAW/plasma or EB with high-purity argon/helium plus trailing shields or a chamber; keep the weld and HAZ below ~200 ppm oxygen pickup and expect bright silver, not straw or blue, welds.
Can Zr 706 be formed, bent or molded?
The low-oxygen 706 chemistry cold-bends and dishes well with generous radii (≥3t) and slow ram speeds; hot form 700–800 °C in inert conditions and pickle scale in HNO3-HF afterwards.
What surface finishes work on Zr 706?
Mechanically polish or abrasive-blast then pickle/passivate for a stable oxide; anodic colouring is possible, and avoid embedding iron from steel tooling to prevent rust staining and localized attack.
Zr 706 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) | 2 – 3 | 2.5 |
| Hfhafnium not removed (industrial, non-nuclear grade) | ≤ 4.5 | 2 |
| Fe+Cr | ≤ 0.2 | 0.1 |
| Otighter than Zr 705 (0.18 max) — source of the higher ductility | ≤ 0.16 | 0.11 |
| C | ≤ 0.05 | 0.02 |
| N | ≤ 0.03 | 0.01 |
| H | ≤ 0.01 | 0 |
| Zr+HfZr+Hf minimum per ASTM B550/B551 | ≥ 95.5 (balance) | — |
Zr 706-HW — frequently asked
What is Zr 706-HW used for?
Zr 706-HW is typically used for critical chemical process components, corrosion-resistant reactor internals and specialty piping. In short: formable Nb zirconium; tighter-chemistry Zr 705; weldable high-strength Zr.
What is the yield strength of Zr 706-HW?
Zr 706-HW has a typical yield strength of 390 MPa (56.6 ksi) and a tensile strength of 545 MPa (79 ksi) — stronger than 61% of refractory metal grades. Strength varies by condition: see the 4 listed tempers.
Is Zr 706-HW easy to machine?
Not especially — machinability is rated fair (40/100, better than 93% of refractory metal grades). Machine like a gummy austenitic stainless — sharp carbide tools, heavy positive rake, slow speed with high feed and flood coolant; never let fine chips accumulate dry (pyrophoric).
Can Zr 706-HW be welded?
Yes — weldability is rated very good (73/100). GTAW/plasma or EB with high-purity argon/helium plus trailing shields or a chamber; keep the weld and HAZ below ~200 ppm oxygen pickup and expect bright silver, not straw or blue, welds.
What surface finishes work on Zr 706-HW?
Mechanically polish or abrasive-blast then pickle/passivate for a stable oxide; anodic colouring is possible, and avoid embedding iron from steel tooling to prevent rust staining and localized attack.
Can Zr 706-HW be formed, bent or molded?
The low-oxygen 706 chemistry cold-bends and dishes well with generous radii (≥3t) and slow ram speeds; hot form 700–800 °C in inert conditions and pickle scale in HNO3-HF afterwards.
What is the maximum service temperature of Zr 706-HW?
Zr 706-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 Zr 706 Annealed and Zr 706-STA?
Annealed is the default condition — default stocked condition for plate, sheet, bar and tube; best ductility and formability with full corrosion resistance. STA: special-order high-strength condition for fasteners and small structural parts; corrosion resistance and toughness drop and it is rarely used for pressure vessels. Yield strength is 400 MPa in Annealed versus 750 MPa in STA.
Sources
- ASTM B550/B550M — Zirconium and Zirconium Alloy Bar and Wire — ASTM International (2020)
- ASTM B551/B551M — Zirconium and Zirconium Alloy Strip, Sheet and Plate — ASTM International (2019)
- ASTM B523/B658 — Zirconium and Zirconium Alloy Seamless and Welded Tube/Pipe — ASTM International (2020)
- ASM Handbook Vol. 2 — Properties of Nonferrous Alloys (Zirconium and Hafnium) — ASM International (1990)
- Zirconium alloy 702/705 industrial grade property sheets — ATI / Wah Chang (2015)
- Corrosion of Zirconium and Zirconium Alloys (ASM Corrosion Handbook Vol. 13B) — 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.