Invar 36 Strip
Invar 36 strip is a thin,flat-rolled form of a specialized nickel-iron alloy (composed of approximately 36% nickel and 64% iron) renowned for its near-zero thermal expansion.This unique property allows the material to maintain almost completely constant dimensions when subjected to temperature changes.
Key Properties
- Ultra-Low Thermal Expansion:
Its coefficient of thermal expansion is roughly one-tenth that of standard carbon steel.It remains dimensionally stable from cryogenic temperatures up to about 260°C (500°F). - Cryogenic Toughness:
It retains excellent mechanical strength,structural integrity,and resistance to fatigue in extremely cold environments. - Workability:
While it can gum up tools during heavy machining,in strip form it is highly responsive to cold rolling,stamping,and forming operations.
We offer Invar 36 strips and coils in thicknesses of 0.1 – 3.0.We offer not only stainless steel strips but also precision strips made of Hastelloy, Incoloy, Inconel, Monel, and other high-performance alloys.Our products comply with ASTM F1684, EN 10204, ISO 9001, PED 2014/68/EU, CE,and other standards.With over a decade of experience in manufacturing and import/export,we are your best wholesaler in China.
Applications of Invar 36 Strip
- Circuit breakers
- Thermostat metals
- Laser systems
- Optical benches
- Aerospace tooling
- LNG tanks
- Shadow masks
- Precision scales
- Clock pendulums
- Seismic sensors
Chemical Composition of Invar 36 Strip
The chemical composition of Invar 36 Strip is strictly regulated under standard specifications like ASTM F1684 and UNS K93603,keeping a precise target of 36% Nickel and a Balance of Iron to guarantee its iconic low-expansion behavior.
| Ni | Fe | Co | Mn | Si | C | Cr | P | S |
|---|---|---|---|---|---|---|---|---|
| 35.0 – 38.0 | Balance | ≤ 0.50 – 1.00 | ≤ 0.60 | ≤ 0.35 | ≤ 0.05 – 0.10 | ≤ 0.25 – 0.50 | ≤ 0.020 – 0.025 | ≤ 0.020 – 0.025 |
Why Is the Chemistry Controlled So Tightly?
The low thermal expansion of Invar 36 works via a quantum-mechanical balance known as the Invar Effect.If the Nickel level shifts even 1% away from 36%,the alloy’s coefficient of thermal expansion increases sharply.This defeats its purpose in high-precision setups.
How Strip Processing Changes Mechanical
Invar 36 Strip is usually delivered as thin,cold-rolled coils.Because strips are meant to be punched,stamped,or deep-drawn into tiny components,they need specific handling.
- Annealed State:
Strip forms are often shipped fully annealed to bring hardness down (≤ 135 HB) and maximize elongation (＞ 30%).This stops the thin material from cracking while being bent or formed. - Slitting and Flatness:
Precision strips require tight control over slit edges to avoid burrs,alongside specialized leveling to keep the strip flat during automated machine stamping.
Physical & Thermal Performance Breakdown
- Density: Approximately 8.1 g/cm3
- Melting Point: Roughly:Roughly 1430℃ (2600℉).
- Curie Point: The temperature where the alloy changes from magnetic to non-magnetic sits at 230℃ (446℉).Beyond this point, its ultra-low expansion properties stop working.
- CTE: Measures under 1.3 × 10<sup>-6</sup> / ℃ between 20℃ and 100℃,making it roughly ten times more dimensionally stable than standard carbon steel.
Invar 36 Strip Standards & Equivalent Designations
| Invar 36 Alloy (Low Expansion) | |||||
|---|---|---|---|---|---|
| Standard / System | Equivalent Designation | Product Form | GB (China) | GJB (Military) | GOST (Russia) |
| Chinese Standard | 4J36 (Fe-Ni36) | Plates, Sheets & Strips | GB/T 15018 | GJB 1952A | – |
| Russian / CIS Standard | 36N / 36H (36Н) | Bars & Rods | GB/T 14985 | – | GOST 14080 / 10994 |
| ISO Chemical Name | Ni36 / FeNi36 | Seamless Pipes & Tubes | – | – | – |
| UNS System | UNS K93600 / K93603 | Welded Pipes & Tubes | – | – | – |
| Aviation / Aerospace | ASTM F1684 / Werkstoff 1.3912 | Forgings & Rings | – | – | – |
| UK Designation | NILO Alloy 36 / Pernifer 36 | ||||
| Generic Trade Name | Invar 36, Alloy 36, Invar Steel | ||||
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Mechanical Properties of Invar 36 Strip
The mechanical properties of Invar 36 Strip are highly dependent on its material condition (temper)—ranging from the annealed (soft) state for deep drawing and stamping to the cold-rolled (hardened) state for high strength.
| Property | Annealed Condition (Soft) | Cold-Rolled Condition (Hard) |
|---|---|---|
| Tensile Strength | 490 – 550 MPa (71 – 80 ksi) | 690 – 830 MPa (100 – 120 ksi) |
| Yield Strength | 240 – 310 MPa (35 – 45 ksi) | 550 – 760 MPa (80 – 110 ksi) |
| Elongation | 30 – 45% | 2 – 8% |
| Hardness | ≤ 80 HRB (150 HV) | ≥ 95 HRB (220 HV) |
| Modulus of Elasticity | 141 GPa (20.5 × 106 psi) | 148 GPa (21.5 × 106 psi) |
| Poisson’s Ratio | 0.29 | 0.29 |
The Critical Impact of Heat Treatment
When manufacturing components from Invar 36 Strip,cold processing (like rolling, slitting, or punching) introduces internal residual stresses.Residual stress degrades the ultra-low thermal expansion properties.
To restore maximum dimensional stability,a specific three-step stabilization heat treatment is often required after mechanical forming:
- Heating:
Hold at 830℃ (1525℉) for 30 minutes per inch of thickness,followed by water quenching. - Stress Relief:
Re-heat to 315℃ (600℉) for 4 to 5 hours,then air cool. - Stabilization:
Heat to 95℃ (205℉) for 48 hours,then air cool.
Work Hardening Behavior
Invar 36 work-hardens rapidly when subjected to cold working.For thin precision strips,this means that while initial stamping might be easy,continuous deep drawing may require intermediate anneals to prevent the strip from splitting.
Cryogenic Mechanical Excellence
Unlike many carbon steels that become completely brittle at sub-zero temperatures,Invar 36 Strip maintains its excellent mechanical properties under cryogenic conditions.Down to -250℃,its tensile and yield strength actually increase while it retains strong impact toughness and elongation.This makes it a premier option for liquefied natural gas containment components.
Machinability and Slitting Performance
In its annealed state, Invar 36 is “gummy” and tough,resembling austenitic stainless steels (like Grade 316).
- When cutting or slitting Invar 36 thin strips into narrow widths,high-grade tungsten carbide tooling must be used.
- Clearances must be set precisely to avoid generating massive edge burrs,which ruin the strip’s flatness.
Our Advantages in Manufacturing Invar 36 Strip
Precise Chemical Control
We strictly control the nickel content within a razor-thin margin centered right at 36%.By minimizing trace elements like Carbon,Chromium,and Silicon,we eliminate composition drifting.This guarantees that every batch of our Invar 36 strip achieves a near-zero coefficient of thermal expansion,ensuring exceptional dimensional stability for high-precision applications.
Advanced Rolling Capabilities
Equipped with state-of-the-art precision cold-rolling mills,we can manufacture ultra-thin,micro-gauge Invar 36 strips down to 0.1mm (or custom thinness) with exceptionally tight thickness tolerances.Our advanced automated leveling systems ensure impeccable flatness and zero coil set,making our strips ideal for continuous high-speed stamping and deep-drawing processes.
Customized Heat Treatment
Residual internal stresses from rolling can ruin Invar’s low-expansion behavior.We offer optimized,proprietary vacuum annealing and stabilization heat treatments customized to your specific processing needs.Whether you require a fully soft annealed state (≤ 150 HV) for seamless stamping or a stress-relieved condition for micro-machining,we deliver the exact mechanical profile needed.
Flawless Surface Quality
Using top-tier tungsten carbide slitting tools,we slice wide coils into narrow precision strips with near-zero edge burrs and exceptionally clean cuts.Our manufacturing lines operate under strict dust-free controls to ensure a flawless surface finish—entirely free of pits, scratches,or rolling marks—which is critical for electronics,shadow masks,and optical applications.
FAQs About Invar 36 Strip
Cold working (rolling, slitting, stamping) introduces internal stresses that degrade Invar’s low-expansion properties.Annealing and stabilization heat treatments are required to relieve these stresses,lower the hardness (typically ≤ 150 HV),and restore the alloy’s optimal near-zero expansion profile.
Yes.Unlike standard steels that become brittle at sub-zero temperatures,Invar 36 retains excellent cryogenic toughness and ductility down to -250°C.Its tensile strength increases in extreme cold without losing structural integrity,making it a top choice for LNG tank linings and aerospace components.
Invar 36 offers excellent stability around room temperatures up to 260°C.
Super Invar adds cobalt to achieve nearly zero expansion right around room temperature,but its stable temperature window is much narrower.
Kovar is engineered specifically to match the thermal expansion of borosilicate glass and ceramics for airtight electronic sealing.
Invar 36 is mechanically “gummy” and tough,similar to 316 stainless steel.When stamping or slitting thin strips,it can cause rapid tool wear and heavy edge burrs.Utilizing high-grade tungsten carbide tooling and maintaining precise cutting clearances are essential to achieving a clean,burr-free edge.
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