Refractory Metal Excel-HT (Β-quenched and aged)
Heat-treated state
Highest-strength and best creep-resistant condition for thin-wall pressure tubes; lowest fracture toughness and most sensitive to hydride embrittlement.
Values for the HT condition
Other Excel tempers and conditions
Excel is listed in 4 conditions; see the grade overview at Excel.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Softest, most ductile and most corrosion-stable condition; chosen when formability or maximum toughness matters more than strength. | 470 | 620 | 22 | 205 HV | — |
CWDefault Cold worked | Standard CANDU pressure-tube condition: cold pilgered/drawn then stress-relieved ~400 °C for high strength with retained toughness. | 730 | 850 | 14 | 25 HRC | — |
Cold worked and aged | Ageing after cold work precipitates β/Mo-bearing phases for extra strength and creep resistance at some ductility cost. | 800 | 900 | 12 | 28 HRC | — |
HTThis page Β-quenched and aged | Highest-strength and best creep-resistant condition for thin-wall pressure tubes; lowest fracture toughness and most sensitive to hydride embrittlement. | 870 | 990 | 10 | 31 HRC | — |
What is Excel-HT?
Excel-HT is Excel heat treated to HT — highest-strength and best creep-resistant condition for thin-wall pressure tubes; lowest fracture toughness and most sensitive to hydride embrittlement. Excel-HT has a yield strength of 870 MPa (126 ksi) and a tensile strength of 990 MPa (144 ksi) — stronger than 91% of refractory metal grades. Elongation at break is 10% and the elastic modulus is 97 GPa (14.1 Msi). Excel-HT has a density of 6.57 g/cm³ (0.237 lb/in³), lighter than 67% of refractory metal grades. It melts at 1,780°C (3,236 °F). CW is the default condition FabDigit quotes; HT is available on request or by drawing note.
Advantages
- High strength — 870 MPa (126 ksi), better than 91% of refractory metal grades
Limitations
- Low stiffness — 97 GPa (14.1 Msi), worse than 91% of refractory metal grades
- Low electrical conductivity — 2.2 % IACS, worse than 91% of refractory metal grades
- Poor heat conductor — 15.5 W/m·K (8.96 BTU/hr·ft·°F), worse than 81% of refractory metal grades
Excel-HT properties
Typical room-temperature values for Excel-HT; 11 are specific to this condition. Other listed values are Excel reference data and may not represent this condition. Bars are the position among refractory metal grades.
Physical3
Excel-HT has a density of 6.57 g/cm³ (0.237 lb/in³), lighter than 67% of refractory metal grades. It melts at 1,780°C (3,236 °F).
Mechanical13
Excel-HT has a yield strength of 870 MPa (126 ksi) and a tensile strength of 990 MPa (144 ksi) — stronger than 91% of refractory metal grades. Elongation at break is 10% and the elastic modulus is 97 GPa (14.1 Msi).
Thermal6
Excel-HT is rated for continuous service to 450°C (842 °F). It conducts heat at 15.5 W/m·K (8.96 BTU/hr·ft·°F), worse than 81% of refractory metal grades. Thermal expansion is 6 µm/m·K (3.33 µin/in·°F).
Electrical3
Excel-HT conducts electricity at 2.2 % IACS, worse than 91% of refractory metal grades.
Chemical & Environmental3
Corrosion resistance is excellent (85/100), better than 52% of refractory metal grades.
Sustainability4
Producing a kilogram of Excel-HT takes about 1,400 MJ of energy and emits 85 kg of CO₂ — more than 67% of refractory metal grades. Typical recycled content is 15%.
Manufacturability8
Excel-HT's machinability is poor (22/100, worse than 73% of refractory metal grades); weldability fair (45/100); formability poor (20/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Excel-HT
Is Excel easy to machine?
Slow speeds, heavy positive-rake carbide tooling and flood coolant; fine chips are pyrophoric and must be collected wet.
Can Excel be welded?
GTAW/EBW in high-purity argon or vacuum only — any air, N or H pickup embrittles the weld; heat-treated strength is lost in the HAZ and cannot be restored without full re-solution treatment.
Can Excel be formed, bent or molded?
Cold pilgering and tube drawing are feasible but the alloy work-hardens rapidly, needing intermediate vacuum anneals; hot working done in the α+β range around 800 °C.
What surface finishes work on Excel?
Pickle in HNO3/HF to remove oxide and hydride-rich surface, then autoclave-passivate in steam; anodising gives decorative/identification oxide films only.
Excel 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 |
|---|---|---|
| Snprimary solid-solution strengthener | 3.2 – 3.8 | 3.5 |
| Nbβ-stabiliser | 0.6 – 1 | 0.8 |
| Moβ-stabiliser, creep resistance | 0.6 – 1 | 0.8 |
| Ocontrolled interstitial (900–1300 ppm) | 0.09 – 0.13 | 0.11 |
| Feresidual | ≤ 0.05 | 0.03 |
| Cresidual | ≤ 0.03 | 0.02 |
| Nresidual | ≤ 0.01 | 0 |
| Hfnuclear-grade limit | ≤ 0.01 | 0.01 |
| Zr | balance | — |
Excel-HT — frequently asked
What is Excel-HT used for?
Excel-HT is typically used for CANDU reactor pressure tubes, heavy-water reactor structural components, calandria and channel hardware, high-strength zirconium tubing and reactor pressure-boundary fittings. In short: strongest zirconium pressure-tube alloy; high creep resistance; heat-treatable Zr-Sn-Nb-Mo.
What is the yield strength of Excel-HT?
Excel-HT has a typical yield strength of 870 MPa (126 ksi) and a tensile strength of 990 MPa (144 ksi) — stronger than 91% of refractory metal grades. Strength varies by condition: see the 4 listed tempers.
Is Excel-HT easy to machine?
Not especially — machinability is rated poor (22/100, worse than 73% of refractory metal grades). Slow speeds, heavy positive-rake carbide tooling and flood coolant; fine chips are pyrophoric and must be collected wet.
Can Excel-HT be welded?
With care — weldability is rated fair (45/100). GTAW/EBW in high-purity argon or vacuum only — any air, N or H pickup embrittles the weld; heat-treated strength is lost in the HAZ and cannot be restored without full re-solution treatment.
What surface finishes work on Excel-HT?
Pickle in HNO3/HF to remove oxide and hydride-rich surface, then autoclave-passivate in steam; anodising gives decorative/identification oxide films only.
Can Excel-HT be formed, bent or molded?
Cold pilgering and tube drawing are feasible but the alloy work-hardens rapidly, needing intermediate vacuum anneals; hot working done in the α+β range around 800 °C.
What is the maximum service temperature of Excel-HT?
Excel-HT is rated for continuous use to about 450°C (842 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Excel-CW and Excel-ANN?
CW is the default condition — standard CANDU pressure-tube condition: cold pilgered/drawn then stress-relieved ~400 °C for high strength with retained toughness. ANN: softest, most ductile and most corrosion-stable condition; chosen when formability or maximum toughness matters more than strength. Yield strength is 730 MPa in CW versus 470 MPa in ANN.
Sources
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys (Zirconium and Zirconium Alloys) — ASM International (1990)
- ASM Handbook Vol.13B — Corrosion: Materials (Zirconium) — ASM International (2005)
- ASTM B353 / B811 — Wrought zirconium and zirconium alloy tubing for nuclear service — ASTM International (2018)
- AECL CANDU pressure-tube alloy development literature (Excel Zr-3.5Sn-0.8Nb-0.8Mo) — Atomic Energy of Canada Limited (1990)
- IAEA TECDOC on zirconium alloy properties for water reactor fuel and pressure tubes — IAEA (2010)
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.