Ni-Span C Alloy 902 (ASTM F30, UNS K94610)

– Precision Constant‑Elasticity Alloy Tube

Ni‑Span C Alloy 902 (UNS K94610) is a nickel‑iron‑chromium precision alloy, also classified as an elastic alloy or constant‑elasticity alloy. Its core value lies in the fact that its elastic modulus (Young’s modulus E) varies very little over a specified temperature range (typically –50°C to +70°C), and it exhibits an extremely low temperature coefficient of elastic modulus (βE).

When you encounter Ni‑Span C, you have entered a highly specialised, high‑value‑added niche market. The procurement logic here is no longer about “strength” or “corrosion resistance,” but rather “precision elasticity” and “constant elasticity.” Ordinary stainless steel pipe costs around $4–7 per kilogram, while Ni‑Span C 902 alloy tube costs dozens of times more. Customers are paying for this special physical property—an elastic modulus that hardly changes with temperature.

Core procurement logic: Purchasing Ni‑Span C alloy tube is essentially purchasing “an elastic modulus that is nearly independent of temperature” – the Elinvar property.

Chemical Composition

Ni‑Span C 902 achieves precipitation hardening through the addition of aluminium (Al) and titanium (Ti). Its main chemical composition (based on UNS K94610 / ASTM F30 requirements) is as follows:

Key Performance Parameters

Constant‑Elasticity Properties (Core Value)

After optimal heat treatment, Ni‑Span C 902 can achieve an extremely low temperature coefficient of elastic modulus (e.g., ±1×10⁻⁵/°C), ensuring that spring stiffness and sensor sensitivity remain stable over a wide temperature range.

Mechanical Properties

Physical Properties

Applicable Standards and Specifications

Procurement note: You must explicitly state in your enquiry: “Material must meet the requirements of AMS 5226E.”

Dimensional Range and Delivery Condition

Dimensional Range

Precision applications demand extremely tight dimensional tolerances – OD, ID, wall thickness, roundness, and straightness often specified at the micrometre level.

Delivery Condition (Critical Clause)

⚠️ Must be specified: “Delivered in the solution‑treated and age‑hardened condition.”

This is the only way for Ni‑Span C 902 to achieve its constant‑elasticity property. Any other delivery condition cannot guarantee the required performance.

Special Requirements (Optional)

• Non‑Destructive Testing: 100% eddy‑current or ultrasonic inspection to ensure defect‑free material.

• Performance Test Report: Require the supplier to provide a temperature‑coefficient‑of‑elastic‑modulus (βE) test report for each batch.

• Packaging: Individual moisture‑proof and shock‑proof protective packaging.

Heat Treatment – The “Golden Touch” for Constant Elasticity

Heat treatment is the critical process for obtaining constant‑elasticity in Ni‑Span C 902:

Solution Treatment

• Temperature: Approximately 120 – 190°C (actual solution treatment may be higher, but typical commercial practice often uses a lower‑temperature stabilisation; the standard age‑hardening temperature is around 650°C)

• Purpose: To fully dissolve alloying elements

Age Hardening (Precipitation Hardening)

• Temperature: 550 – 850°C (typically 650°C)

• Time: 2 – 5 hours

• Cooling: Air cool

Appropriate combination of cold work and heat treatment enables the alloy to achieve a substantially constant elastic modulus over the temperature range of –50°F to +150°F.

Key note: Temperature and time control must be extremely precise, typically requiring a dedicated vacuum or protective‑atmosphere furnace, and may involve complex multi‑stage aging processes.

ZYTC Alloy – A Professional Chinese Supplier of Precision Alloy Tubes

Tianjin ZYTC Alloy Technology Co., Ltd. (ZYTC Alloy) is a comprehensive supply chain management company with over 30 years of experience in the specialty metals industry. Headquartered in Tianjin, China, ZYTC integrates melting, forging, rolling, heat treatment, precision machining, non‑destructive testing, and logistics distribution into one seamless service platform.

ZYTC Alloy offers the following core strengths in precision alloys:

ZYTC Alloy deeply understands the special nature of precision alloys like Ni‑Span C 902 – customers are not just buying material, but also “performance guarantee terms” and “completeness of the technical data package.” Each batch is supplied with a full mill test report (including chemical composition, mechanical properties, and temperature‑coefficient‑of‑elastic‑modulus test data).