Model No: Invar 36 Strip

Invar 36 Strip

Lork Group offers precision Invar 36 strip. Ideal for semiconductor, laser, aerospace, and cryogenic applications. ASTM F1684 compliant. Available in thicknesses from 0.05mm to 3.0mm, width up to 400mm. Request a quote.

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Product Introduction

This material tackles the arch-enemy known as"thermal expansion and contraction."

Anyone working with precision equipment shares a common nightmare: thermal expansion and contraction.

An optical mount assembled at a room temperature of 20°C sees its optical path misaligned when moved to a 35°C workshop. A precision instrument calibrated in winter yields incorrect readings upon startup at a client's site in summer. Ordinary steel has a thermal expansion coefficient of 12 × 10⁻⁶/°C; for a one-meter-long part subjected to a 50°C temperature change, the dimensional shift is 0.6 mm—rendering a precision instrument useless.

Invar 36 was created to solve this very problem.

Its thermal expansion coefficient is one-tenth that of ordinary steel. For a one-meter-long part, a 50°C temperature change results in a dimensional shift of less than 0.06 mm. This figure is precisely why it commands a premium price.

Who buys it?

Manufacturers of lithography machines, where wafer stages must match the thermal expansion of silicon wafers (silicon's CTE is approximately 2.6 × 10⁻⁶/°C)?
Manufacturers of laser interferometers, where thermal drift in mirror mounts directly impacts measurement accuracy?
Manufacturers of molds for aerospace composites, where mold dimensions must remain constant despite temperature swings of tens of degrees in curing ovens?
Manufacturers of LNG storage tanks, requiring materials that remain dimensionally stable and do not become brittle or crack at -162°C?
Manufacturers of satellite structural components, where parts must not deform despite temperature fluctuations of hundreds of degrees in space?

The Invar 36 precision strip supplied by Lork Group strictly complies with the ASTM F1684 standard and comes with a comprehensive Certified Material Test Report (CMTR), including the measured thermal expansion coefficient curve.

If your parts do not require precision fits, ordinary cold-rolled steel will suffice. However, if your products require repeated rework because they"lose accuracy when the temperature changes"—read on.

Chemical composition: 36% nickel—its"ID card."

The name"Invar 36"is derived from its 36% nickel content—the source of the"Invar effect."If the nickel content deviates by more than 0.5%, the coefficient of thermal expansion changes.

Typical chemical composition supplied by Lork Group (compliant with ASTM F1684 / UNS K93600):

Material Type	C	S / P	Si	Ni	Co	Mn	Fe
Content (%)	≤ 0.01 - 0.05	≤ 0.010 - 0.025	≤ 0.20 - 0.35	35.5 - 36.5	≤ 0.5 - 1.0	0.2 - 0.6	Balance

⚠️ Procurement Tip: When you receive the material specifications, the first thing to verify is the nickel content—it must fall within the 35.5–36.5% range. This is the"soul"of Invar 36; even the slightest deviation means it is no longer the genuine material.

Core performance: Thermal expansion coefficient is the"protagonist"

The mechanical properties of Invar 36 are merely"adequate"; its true value lies in its thermal expansion characteristics.

🔹 Coefficient of Thermal Expansion (CTE) — This is the key metric.

Temperature range	Typical CTE value (×10⁻⁶/℃)	CTE of comparative materials
20 - 100℃	1.2 - 1.8	Carbon steel ~12, stainless steel ~17
-60 - 20℃	~1.0	Silicon ~2.6, glass ~0.5–1.0
20 - 200℃	~1.5	Aluminum alloy ~23
> 230°C (above Curie point)	Sharp rise	–

What does this figure mean? A 100 mm long Invar part expands by only 0.008–0.012 mm when heated from 20°C to 100°C. A steel part of the same dimensions expands by 0.096 mm—a difference of nearly tenfold.

⚠️ Key limitation: The"Invar effect"of Invar 36 vanishes above approximately 230°C (the Curie point), causing the CTE to rise sharply to levels comparable to ordinary steel. Therefore, it is suitable only for an operating range of -250°C to +200°C; do not use it beyond this temperature.

Mechanical Properties (Annealed Strip)

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)
Tensile Strength	450 - 550 MPa
Yield strength	240 - 300 MPa
Elongation	30 - 42%
Hardness (HV)	130 - 160
Density	8.1 g/cm³
Modulus of elasticity	145 GPa

🔹 Corrosion Resistance
Dry indoor environments: Oxidation-resistant; essentially rust-free.

Humid/salt-spray environments: Prone to rusting. As it contains no chromium, it lacks the passivation layer found in stainless steel.

Mildly acidic environments: Usable, though performance is inferior to stainless steel.

⚠️ Procurement Note: If the operating environment is humid or saline, Invar 36 requires surface protection (plating, coating, or oiling)—a detail often overlooked during procurement.

Contact Us

Product Form: Precision strip is the primary form of Invar 36

If you are purchasing Invar 36 strip, you are likely intending to use it for precision stamping, etching, or lamination.

Strip specifications available from Lork Group:

Parameter	Range / Requirement
Thickness	0.05 – 3.0 mm (customizable to thinner gauges)
Width	5 – 200 mm (slittable to narrower widths)
Thickness Tolerance	±0.005 – 0.01 mm (depending on thickness)
Delivery Condition	Annealed (soft) / Cold-rolled (half-hard/hard)
Surface Finish	Bright annealed (Ra ≤ 0.4 μm) / Pickled and passivated
Packaging	Coils / Cut-to-length straight strips / Protective film coating

⚠️ Key Choice:
1. For stamping complex shapes → Choose the annealed state (soft state): Elongation is 30–42%; suitable for stamping, bending, and deep drawing. Note that dimensions may shift slightly if stress-relief annealing is not performed after processing.
2. For higher strength or thinner gauges → Choose the cold-rolled state: Strength increases to 600–700 MPa, but elongation drops to 10–15%, making processing more difficult.
3. For laser cutting → Choose the bright annealed state: Low surface roughness results in a smaller heat-affected zone and minimal burring during laser cutting.

Regarding Price and Delivery Time

Invar 36 is not cheap compared to ordinary stainless steel. Why is it expensive?

1. 36% nickel content; the price of nickel dictates the cost floor.
2. Demanding smelting requirements: nickel content deviation must be controlled within ±0.15%; vacuum melting combined with electroslag remelting (ESR) is the standard process.
3. Difficult rolling process: high work-hardening rate; rolling thin strip involves slow speeds and low yields.

Reference price range (2026 market conditions, annealed strip):
Thin strip (0.05–0.5 mm): Approx. 400–600 RMB/kg (small batches of 10–50 kg)
Medium-to-thick strip (0.5–2.0 mm): Approx. 300–500 RMB/kg
Bulk orders (≥100 kg): 5–8% discount available

⚠️ Additional costs to confirm when inquiring:

Slitting fees (for narrow widths)
Cut-to-length fees
Protective film application fees
Third-party inspection fees (SGS/BV)

Reference lead times:

Standard specifications (in stock): 3–7 working days
Non-standard widths/thicknesses: 2–3 weeks
Custom smelting batches: 4–6 weeks

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]