Model No: Alloy 902

AMS 5226/ASTM B753 Ni-Span C 902 Alloy

Lork Group supplies Ni-Span C 902 bright bars in the annealed condition (diameters 6–50 mm), as well as aged bright bars and precision-ground bars (h6 tolerance). Pricing is quoted individually based on processing complexity; custom sizes and specific heat treatment requirements are also available upon request.

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Product Introduction

Based on our many years of experience supplying Ni-Span C 902 alloy, we can attest that Ni-Span C Alloy 902 is both expensive and—to put it mildly—temperamental. Its performance characteristics are not inherent simply by virtue of being melted; rather, they must be"tuned"through precise heat treatment processes. If you purchase the wrong temper or apply incorrect heat treatment parameters, it becomes indistinguishable from an ordinary iron bar—or potentially even worse.

So, why do people still pay a premium for it?

Because in certain scenarios, ordinary materials simply cannot withstand the demands:

Does your sensor need to maintain zero drift in its output across a temperature range of -40°C to +80°C? Ordinary spring steel’s elastic modulus fluctuates with temperature, rendering the resulting measurement data completely unreliable.
Is your precision instrument housed in a temperature-controlled laboratory environment? That is still not enough. A mere 1°C temperature fluctuation can cause optical alignment to drift by several microns; you require a material with a coefficient of thermal expansion (CTE) closely matching that of glass or ceramics.
Is your equipment situated near a strong magnetic field (such as those generated by MRI machines, particle accelerators, or navigation systems)? Ordinary stainless steel becomes magnetic after cold working, which can interfere with readings or even lead to equipment failure.

This is the battlefield where Alloy 902 excels. It is not a general-purpose material; rather, it is engineered for precision equipment where the motto is:"Cost is no object; inaccuracy is the only fear."

The Ni-Span C 902 supplied by Lork Group is delivered in strict compliance with AMS 5226 and ASTM B753 standards. Each shipment is accompanied by a comprehensive Certified Material Test Report (CMTR), containing all the critical data you require—including CTE values and heat treatment records.

Chemical Composition

The properties of Ni-Span C 902 are derived from its Fe-Ni-Cr base combined with precipitation strengthening. The following represents the typical composition range, strictly adhering to AMS 5226 / ASTM B753.

Material Type	C	Ai	Ti	Ni	Cr	P / Si / Mn	Fe
Content (%)	≤ 0.05	0.3 - 0.8	2.2 - 2.75	41.0 - 43.5	4.9 - 5.75	≤0.30	Balance

Core Physical Properties

● Temperature Coefficient of Elastic Modulus (βE): Within the range of -45°C to +65°C, it can be adjusted to be nearly zero (within ±1 × 10⁻⁶/°C).

What does this mean? Within this temperature range, the material's"stiffness"remains virtually unchanged regardless of temperature fluctuations. When used to manufacture pressure sensors, accelerometers, or springs, the resulting force or displacement output will not drift due to changes in ambient temperature.

● Coefficient of Thermal Expansion (CTE): Approximately 7.6 – 9.5 × 10⁻⁶/°C within the 20–100°C range.

For comparison: Ordinary steel has a CTE of ~12, while aluminum alloys are ~23. This material exhibits a much better thermal match with glass and ceramics, making it highly suitable for use in optical mounts and packaging materials.

● Magnetic Permeability: Weakly magnetic / Non-magnetic (μ ≈ 1.002–1.01).
What does this mean? When deployed in close proximity to MRI equipment, navigation gyroscopes, or quantum experimental apparatus, it will not interfere with the surrounding magnetic fields.

● Density: Approximately 8.05 g/cm³.

● Curie Point: Approximately 110°C.

Mechanical and Physical Properties

We will discuss Ni-Span C 902 constant modulus alloys based on their heat-treatment states—for the same material, different states result in vastly different properties.

Heat Treatment Condition	Annealed Condition (Solution Treated)	Spring-Tempered Condition (Cold-Worked/Strain-Hardened)	Spring Tempering + Aging Treatment (Final Condition)
Tensile Strength	600 – 800 MPa	900 – 1100 MPa	1300 – 1500 MPa (Typical values can exceed 1450 MPa)
Hardness	–	–	350 – 450 HV (Approx. 37–44 HRC)
Elongation	≥30%	–	≥ 5–6%
Elastic Modulus (E)	–	–	165 – 200 GPa (Varies with heat treatment condition)
Characteristics	Soft and easily machinable (turning, milling, drilling, stamping). The material is typically supplied in the annealed state, allowing you to perform the aging treatment yourself.	Possesses a certain level of inherent strength; the degree of cold-working deformation is precisely controlled. For certain spring applications, this material is purchased and utilized directly in this specific condition.	–
Recommended Purchase	Suitable for purchasing raw materials to be subsequently processed in-house into precision components (such as bellows, diaphragms, and complex-shaped springs).	Suitable for manufacturing"ready-to-use elastic components"(such as sensor elastic bodies and precision springs).	What would be suitable for you to work on is the"Resonant Cavity/Tuning Fork for Temperature-Controlled Crystal Oscillators"(which requires extremely high frequency stability).
What Lork Can Do	We can supply annealed, precision-ground bars manufactured according to your drawings, featuring a surface roughness of Ra ≤ 0.8 μm and a straightness of ≤ 0.1 mm/m, ready for direct machining.	We can provide certain in-house testing services, as well as assist with third-party testing, such as through SGS.	We can provide batch-tested E-T curves (Elastic Modulus-Temperature curves) covering the range from -50°C to +100°C.

If you would like to understand why the information above varies across different heat treatment states—or if you have other specific applications in mind for this constant-modulus alloy (Ni-Span C 902)—we would be happy to discuss the details further.

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Before Placing Your Order, Please Answer These 3 Questions

Purchasing Ni-Span C 902 requires careful consideration—it is not a material you should buy"blindly."To prevent you from selecting the wrong material condition—which could lead to the entire batch being scrapped—please answer the following three questions (alternatively, click the button on the right to contact a technical engineer directly):

Q1: What is your application scenario?
A. Precision Springs / Elastic Components (Focus: Constant Elasticity)
B. Optical / Laser Structural Components (Focus: Low Thermal Expansion)
C. Sensor Diaphragms / Bellows (Focus: High Strength + Constant Elasticity + Machinability)
D. Frequency Components / Resonant Cavities (Focus: Frequency-Temperature Coefficient)
E. Other (Please specify in the comments)

Q2: What is your subsequent processing workflow?
A. Direct Assembly Upon Receipt (Requires Aged Condition + Precision Dimensions)
B. In-house Aging Treatment Upon Receipt (Requires Annealed Condition)
C. Turning / Milling / Drilling Upon Receipt (Requires Annealed Condition; Aging performed after machining)
D. Grinding to Final Dimensions Upon Receipt (Either Aged or Annealed condition is acceptable, but processing methods differ)

Q3: What are your operating temperature range and dimensional stability requirements?
A. Room Temperature (20 ± 10°C) → Standard Condition is Sufficient
B. Wide Temperature Range (-40°C to +80°C) → Requires Measured βE Value
C. Precise Requirements for Expansion Coefficient (Must match glass/ceramics) → Requires Measured CTE Value
D. Strong Magnetic Field Environment → Requires Verification of Measured Magnetic Permeability

Contact the Lork Group Technical Team

Don't place an order based on guesswork. Send us your drawings, operating temperature requirements, and processing specifications; our materials engineers will assist you with"Condition Matching"—completely free of charge.

Email: [daisy@lorkgroup.com]
WeChat/WhatsApp: [+ 86 175 1308 1871]