Refractory Metal NbTi-ANN (Annealed)
Heat-treated state · default condition
Standard stocked condition for NbTi billets, extrusion feedstock, rod and sheet; maximum ductility for subsequent co-extrusion and drawing.
Values for the ANN condition
Other NbTi tempers and conditions
NbTi is listed in 4 conditions; see the grade overview at NbTi.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANNDefaultThis page Annealed | Standard stocked condition for NbTi billets, extrusion feedstock, rod and sheet; maximum ductility for subsequent co-extrusion and drawing. | 350 | 620 | 25 | 160 HB | 12 W/m·K |
Hot worked (extruded / forged) bar, as-worked | Choose for as-forged or as-extruded NbTi bar and monofilament preform stock where partial work hardening is acceptable. | 520 | 720 | 18 | 12 HRC | 2.9 % IACS |
Cold worked | Bare NbTi filament or fine wire after heavy drawing reduction, before or between precipitation heat treatments; highest strength, low ductility. | 900 | 1,000 | 4 | 28 HRC | 2.7 % IACS |
Cold drawn with intermediate α-Ti precipitation heat treatments | The functional condition of finished superconducting filaments: 3–5 heat treatments near 400 °C interleaved with drawing to create α-Ti flux-pinning ribbons and maximum Jc. | 930 | 1,050 | 5 | 26 HRC | 2.7 % IACS |
What is NbTi-ANN?
NbTi-ANN is NbTi heat treated to ANN — standard stocked condition for NbTi billets, extrusion feedstock, rod and sheet; maximum ductility for subsequent co-extrusion and drawing. NbTi-ANN has a yield strength of 350 MPa (50.8 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 57% of refractory metal grades. Elongation at break is 25% and the elastic modulus is 65 GPa (9.43 Msi). NbTi-ANN has a density of 6.05 g/cm³ (0.219 lb/in³), lighter than 87% of refractory metal grades. It melts at 1,900°C (3,452 °F).
Advantages
- Forms and bends easily — 92/100, better than 95% of refractory metal grades
- Lightweight — 6.05 g/cm³ (0.219 lb/in³), better than 87% of refractory metal grades
Limitations
- Low stiffness — 65 GPa (9.43 Msi), worse than 100% of refractory metal grades
- Poor heat conductor — 12 W/m·K (6.93 BTU/hr·ft·°F), worse than 98% of refractory metal grades
- Low electrical conductivity — 2.9 % IACS, worse than 83% of refractory metal grades
- Difficult to machine — 20/100, worse than 77% of refractory metal grades
NbTi-ANN properties
Typical room-temperature values for NbTi-ANN; 12 are specific to this condition. Other listed values are NbTi reference data and may not represent this condition. Bars are the position among refractory metal grades.
Physical3
NbTi-ANN has a density of 6.05 g/cm³ (0.219 lb/in³), lighter than 87% of refractory metal grades. It melts at 1,900°C (3,452 °F).
Mechanical10
NbTi-ANN has a yield strength of 350 MPa (50.8 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 57% of refractory metal grades. Elongation at break is 25% and the elastic modulus is 65 GPa (9.43 Msi).
Thermal6
NbTi-ANN is rated for continuous service to 400°C (752 °F). It conducts heat at 12 W/m·K (6.93 BTU/hr·ft·°F), worse than 98% of refractory metal grades. Thermal expansion is 8 µm/m·K (4.44 µin/in·°F).
Electrical3
NbTi-ANN conducts electricity at 2.9 % IACS, worse than 83% of refractory metal grades.
Chemical & Environmental3
Corrosion resistance is excellent (85/100), better than 52% of refractory metal grades.
Sustainability3
Producing a kilogram of NbTi-ANN takes about 700 MJ of energy and emits 45 kg of CO₂ — less than 65% of refractory metal grades. Typical recycled content is 10%.
Manufacturability8
NbTi-ANN's machinability is poor (20/100, worse than 77% of refractory metal grades); weldability fair (45/100); formability excellent (92/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with NbTi-ANN
Is NbTi easy to machine?
Machines like commercially pure titanium — gummy and work-hardening; use sharp uncoated carbide, low speed (15–30 m/min), heavy positive rake, flood coolant and never dwell.
Can NbTi be welded?
Weld only by EB or GTAW in high-purity argon/vacuum chambers; O/N/H pickup above ~300 °C causes embrittlement and destroys superconducting performance near the joint.
Can NbTi be formed, bent or molded?
Outstandingly cold-drawable — area reductions of 10^5 with intermediate 400 °C precipitation treatments; co-extrude in a copper can at 600–700 °C, avoid intermetallic-forming barriers (use Nb diffusion barrier with Cu).
What surface finishes work on NbTi?
Chemically etch/pickle in HNO3-HF, then anodize for coloured insulating oxide; copper cladding is normally left bright or given a thin Sn/Ag or Formvar/polyimide insulation.
NbTi 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 |
|---|---|---|
| TiNb-47Ti nominal; Nb-46.5Ti and Nb-50Ti also produced | 46.5 – 48 | 47 |
| Tatypical superconductor-grade limit | ≤ 0.1 | — |
| Fe | ≤ 0.03 | — |
| Ointerstitials controlled to preserve drawability | ≤ 0.06 | — |
| C | ≤ 0.02 | — |
| N | ≤ 0.01 | — |
| H | ≤ 0 | — |
| Nb | balance | — |
NbTi-ANN — frequently asked
What is NbTi-ANN used for?
NbTi-ANN is typically used for MRI magnet wire, particle accelerator superconducting coils, fusion reactor magnets (e.g. ITER) and superconducting cables. In short: standard NbTi superconductor wire; formability score 92; cold-drawn, not welded.
What is the yield strength of NbTi-ANN?
NbTi-ANN has a typical yield strength of 350 MPa (50.8 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 57% of refractory metal grades. Strength varies by condition: see the 4 listed tempers.
Is NbTi-ANN easy to machine?
Not especially — machinability is rated poor (20/100, worse than 77% of refractory metal grades). Machines like commercially pure titanium — gummy and work-hardening; use sharp uncoated carbide, low speed (15–30 m/min), heavy positive rake, flood coolant and never dwell.
Can NbTi-ANN be welded?
With care — weldability is rated fair (45/100). Weld only by EB or GTAW in high-purity argon/vacuum chambers; O/N/H pickup above ~300 °C causes embrittlement and destroys superconducting performance near the joint.
What surface finishes work on NbTi-ANN?
Chemically etch/pickle in HNO3-HF, then anodize for coloured insulating oxide; copper cladding is normally left bright or given a thin Sn/Ag or Formvar/polyimide insulation.
Can NbTi-ANN be formed, bent or molded?
Outstandingly cold-drawable — area reductions of 10^5 with intermediate 400 °C precipitation treatments; co-extrude in a copper can at 600–700 °C, avoid intermetallic-forming barriers (use Nb diffusion barrier with Cu).
What is the maximum service temperature of NbTi-ANN?
NbTi-ANN 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 NbTi-ANN and NbTi-CW?
ANN is the default condition — standard stocked condition for NbTi billets, extrusion feedstock, rod and sheet; maximum ductility for subsequent co-extrusion and drawing. CW: bare NbTi filament or fine wire after heavy drawing reduction, before or between precipitation heat treatments; highest strength, low ductility. Yield strength is 350 MPa in ANN versus 900 MPa in CW.
Sources
- Handbook of Superconducting Materials (Cardwell & Ginley) — IOP Publishing (2003)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials — ASM International (1990)
- NIST Cryogenic Material Properties Database — NIST (2020)
- NbTi superconducting wire and NbTi alloy rod datasheets — Supercon Inc. / Luvata / Bruker EAS / WST (2023)
- IEC 61788 series — Superconductivity: critical current and mechanical test methods — IEC (2020)
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.