Ni-Span-C 902 (UNS N09902, W.Nr. 2.4964, Vacon 10) is a precipitation-hardenable nickel-iron-chromium constant-modulus alloy developed for applications where elastic stability across fluctuating temperatures is non-negotiable. Its defining feature is the Elinvar effect—a near-zero TEC that keeps the elastic modulus essentially unchanged over -50 to +150°F (-45 to +65°C). Unlike conventional spring steels whose stiffness drifts with every degree of temperature change, Ni-Span-C 902 delivers frequency stability and load-deflection repeatability that no quench-and-temper alloy can match. This thermal invariance makes it the material of choice for precision springs, resonant vibrating elements, pressure-sensing diaphragms, and inertial navigation components across aerospace, horology, and industrial instrumentation. At FUSHUN METAL, we melt Ni-Span-C 902 via VIM for precise chemistry, refine through VAR for inclusion control, and optionally apply PESR for superior ingot solidification structure. The triple-melt route guarantees cleanliness levels well below AMS 5225 limits and eliminates the centerline segregation that can shift the alloy’s delicate thermoelastic balance. Every heat ships with full traceability under our ISO 9001 and AS9120B quality management system, and we tailor aging cycles to lock in the exact TEC each application demands—whether a watchmaker needs minimum hysteresis or an aerospace OEM specifies a zero-crossing frequency-temperature curve.
Equivalent Grades of Ni-Span-C 902
| Standard Body | Designation / Grade |
|---|---|
| UNS | N09902 |
| SAE AMS | AMS 5221 / AMS 5223 / AMS 5225 |
| SAE HS | HS 261 |
| DIN / W.Nr. | 2.4964 (Vacon 10) |
| GB | 3J53 (Ni42CrTiAl) |
| GOST | 42НХТЮ (42NKhTYu) |
| JIS | Sumispan-3 / EL-3 |
| AWS | AWS 080 |
| UK | Elinvar Extra |
FUSHUN METAL stocks and produces to all above specifications. Cross-certification with dual marking (e.g., AMS 5225 + GB 3J53) is standard upon request.
Chemical Composition of Ni-Span-C 902 per AMS 5225
| Element | Min (%) | Max (%) |
|---|---|---|
| Carbon (C) | — | 0.06 |
| Manganese (Mn) | — | 0.80 |
| Silicon (Si) | — | 1.00 |
| Phosphorus (P) | — | 0.04 |
| Sulfur (S) | — | 0.04 |
| Nickel + Cobalt | 41.00 | 43.50 |
| Chromium (Cr) | 4.90 | 5.75 |
| Titanium (Ti) | 2.20 | 2.75 |
| Aluminum (Al) | 0.30 | 0.80 |
| Cr + (Ti – 4C) | 7.10 | 8.10 |
| Iron (Fe) | Balance (~45%) | |
The critical Cr + (Ti – 4C) band directly governs precipitation-hardening response. FUSHUN METAL verifies every heat with OES and wet chemistry, holding internal targets tighter than AMS 5225 tolerances under ISO 9001 and AS9120B.
Applications of Ni-Span-C 902
Precision Timekeeping
Watch hairsprings, mainsprings, balance wheels, chronometer escapements, marine chronometer springs
Aerospace & Defense
Gyroscope flexures, accelerometer elastic elements, inertial navigation springs, satellite resonator diaphragms
Pressure & Force Sensing
Bourdon tubes, aneroid capsules, pressure transducer diaphragms, load cell springs, torque sensor elements
Resonant Systems
Tuning forks, vibrating reed frequency standards, mechanical bandpass filters, sonic delay lines, resonator bars
Industrial Weighing
Precision balance springs, electronic scale flexures, check-weigher elastic pivots, mass comparator strips
Valve & Diaphragm
Cryogenic valve springs, burst disc diaphragms, petrochemical regulator membranes, relief valve springs
Medical Devices
Surgical instrument springs, implantable sensor diaphragms, precision pump flexures, orthopedic measurement cells
Scientific Instruments
Seismograph springs, gravimeter flexures, magnetometer suspensions, microbalance beams, dilatometer strips
Supply Range — Ni-Span-C 902 from FUSHUN METAL
FUSHUN METAL supplies Ni-Span-C 902 in all conventional mill forms, manufactured from VIM–VAR ingots with optional PESR refinement. Our hot-rolling mill covers mid-size diameters while the open-die forging press handles large-section orders up to 1200 mm diameter. Cold-rolling and drawing lines produce precision strip and wire down to 0.05 mm thickness. For Bourdon tube and diaphragm applications, we offer tight-thickness-tolerance strip with surface finish controlled to better than 0.8 μm Ra. All product ships with a 3.1 certificate per EN 10204, and we can supply 3.2 witness-tested certification when required by aerospace quality clauses.
| Product Form | Process | Size Range | Delivery Condition |
|---|---|---|---|
| Rolled Round Bar | Hot Rolled / Cold Finished | ∅3 – 200 mm | Annealed, Spring Temper, Aged |
| Rolled Flat Bar | Hot / Cold Rolled | T 3–60 mm x W 10–400 mm | Annealed, Cold Rolled |
| Forged Round Bar | Open-Die Forged | ∅80 – 1200 mm | Solution Annealed, Rough Turned |
| Forged Flat / Block | Open-Die Forged | T 15–500 mm x W 80–2000 mm | Solution Annealed |
| Cold Rolled Strip | Precision Cold Rolling | T 0.05–3.0 mm x W up to 400 mm | Annealed, 10%/50% Cold Reduced |
| Wire | Cold Drawn | ∅0.10–12.0 mm | Spring Temper, Annealed, Aged |
| Seamless Tube | Cold Pilgered / Drawn | OD 3–219 mm x WT 0.5–20 mm | Annealed, Cold Worked |
Ultrasonic testing per AMS-STD-2154 Class A, surface quality inspection, and dimensional checks are performed on every lot before release. Cut-to-length and custom rough machining are available.
Mechanical Properties of Ni-Span-C 902
The mechanical response of Ni-Span-C 902 is governed by two synergistic strengthening mechanisms: cold work and precipitation hardening. Titanium and aluminum, held within the critical Cr + (Ti – 4C) window, form coherent gamma-prime (Ni3Al,Ti) precipitates during aging that pin dislocations and elevate strength while preserving the Elinvar characteristic. Unlike martensitic spring steels that sacrifice modulus stability for hardness, Ni-Span-C 902 achieves both simultaneously through this metallurgical design. The table below summarizes properties across the most commonly supplied conditions, from soft annealed strip for deep drawing to fully aged spring temper for maximum load-bearing capacity.
| Condition | Heat Treatment | Tensile (MPa) | Yield 0.2% (MPa) | Elong. (%) | Hardness |
|---|---|---|---|---|---|
| Annealed | As solution-annealed per AMS 5221 | 585 – 800 | ~276 | 20 – 35 | HRB 75 – 90 |
| Spring Temper | None — work-hardened only | 965 – 1105 | ~896 | 4 – 7 | HRC 26 – 33 |
| 50% Cold Rolled | 50% reduction, per AMS 5225 | ~965 | ~896 | ~6 | HRC 29 |
| Spring Temper + Aged | Aged 663–704°C (1225–1300°F), 2–3.5 h, air cool | 1380 – 1515 | ~1240 | 5 – 9 | HRC 37 – 42 |
| Stress Equalized + Aged | Stabilize 400°C / 2 h + age 650°C / 2 h, air cool | 1300 – 1450 | ~1170 | 6 – 10 | HRC 36 – 40 |
FUSHUN METAL’s in-house lab maps the full TEC-vs-temperature curve for each production lot using resonant-frequency sweep methodology. Aging cycles between 500–750°C are adjusted per application—lower temperatures favor minimum hysteresis and reduced drift in watch springs, while higher temperatures push ultimate tensile strength past 1500 MPa for aerospace diaphragms and gyroscope flexures. Every reported tensile and hardness data point is traceable to AS9120B and ISO 9001 accredited testing protocols, and the corresponding mill certificate carries the lab’s NADCAP-equivalent scope approval.
