Invar 36,Alloy 36,UNS K93600,E FORU

### **Invar 36® / Alloy 36 / UNS K93600

** **Iron-Nickel Alloy with Ultra-Low Thermal Expansion for Precision Applications

** --- #### **1. Overview

** **Invar 36**, also known as **Alloy 36**, is an iron-nickel alloy renowned for its exceptionally low coefficient of thermal expansion (CTE) at ambient temperatures. This unique property, known as the "Invar Effect," results from a carefully balanced composition that minimizes dimensional changes with temperature fluctuations. Developed over a century ago, Invar 36 remains the material of choice for applications requiring dimensional stability across varying thermal conditions, from cryogenic temperatures up to approximately 400°C. 

 --- #### **2. Chemical Composition (Weight %

)** The typical chemical composition of Invar 36 is outlined below. The balance is Iron (Fe). 

| Element | Content (%) | Key Function | 

| :--- | :--- | :--- | 

| **Iron (Fe)** | Balance | Forms the base matrix of the alloy. | 

| **Nickel (Ni)** | 35.0 - 37.0 | Critical for achieving the low thermal expansion characteristic through the Invar Effect. | 

| **Manganese (Mn)** | 0.35 - 0.65 | Aids in deoxidation and improves hot workability. | 

| **Silicon (Si)** | 0.20 - 0.40 | Enhances fluidity during casting and improves oxidation resistance. | 

| **Carbon (C)** | 0.05 max | Kept low to minimize aging effects and maintain stability. | 

| **Chromium (Cr)** | 0.20 max | Controlled impurity. | 

| **Cobalt (Co)** | 0.20 max | Controlled impurity. | 

| **Copper (Cu)** | 0.20 max | Controlled impurity. | 

| **Aluminum (Al)** | 0.10 max | Controlled impurity. |

| **Molybdenum (Mo)** | 0.10 max | Controlled impurity. | 

| **Sulfur (S)** | 0.015 max | Impurity, kept low to prevent hot shortness. | 

| **Phosphorus (P)** | 0.015 max | Impurity, controlled to maintain ductility. |

 --- #### **3. Physical Properties** 

| Property | Value / Condition | 

| :--- | :--- | 

| **Density** | 8.11 g/cm³ (0.293 lb/in³) | 

| **Melting Point** | ~ 1427 °C (2600 °F) | 

| **Mean Coefficient of Thermal Expansion** | 20 - 100°C (68 - 212°F): **1.3 x 10⁻⁶/°C** (0.7 x 10⁻⁶/°F)
20 - 200°C (68 - 392°F): **2.7 x 10⁻⁶/°C** (1.5 x 10⁻⁶/°F)
20 - 300°C (68 - 572°F): **4.9 x 10⁻⁶/°C** (2.7 x 10⁻⁶/°F) | 

| **Thermal Conductivity** | 10.5 W/m·K (73 Btu·in/hr·ft²·°F) at 20°C (68°F) | 

| **Specific Heat Capacity** | 515 J/kg·K (0.123 Btu/lb·°F) at 20°C (68°F) | 

| **Electrical Resistivity** | 0.82 μΩ·m at 20°C (68°F) | 

| **Modulus of Elasticity (Young's Modulus)** | 141 GPa (20.5 x 10⁶ psi) at 20°C (68°F) | 

| **Curie Temperature** | ~ 279 °C (534 °F) | 

| **Magnetic Properties** | Ferromagnetic below Curie temperature | 

 --- #### **4. Mechanical Properties 

(Typical for Annealed Condition)** 

| Property | Value at Room Temperature | 

| :--- | :--- | 

| **Tensile Strength** | 450 MPa (65 ksi) | 

| **Yield Strength (0.2% Offset)** | 280 MPa (41 ksi) | 

| **Elongation (in 50 mm / 2 in)** | 35% | 

| **Reduction of Area** | 70% | 

| **Hardness (Rockwell B)** | 70 HRB | 

| **Vickers Hardness** | 140 HV | 

 --- #### **5. International Standards

** Invar 36 complies with the following international specifications: 

 *   **ASTM:**   

 *   **F1684:** Standard Specification for Iron-Nickel and Iron-Nickel-Cobalt Alloys for Low Thermal Expansion Applications 

*   **AMS:**    

*   **AMS 7725:** Sheet, Strip, and Plate 

*   **UNS:** K93600 

*   **ISO:**    

*   **ISO 19960:** Iron-nickel low expansion alloys 

*   **EN:**    

*   **EN 10140:** Cold rolled narrow steel strip 

*   **JIS:**    

*   **JIS G 2311:

** Iron-nickel thermal expansion alloys 

 --- #### **6. Product Applications

** Invar 36 is critical in applications requiring exceptional dimensional stability: 

 *   **Aerospace & Defense:

**    *   Satellite structural components    

*   Precision optical mounting systems    

*   Laser and radar alignment frames    

*   Cryogenic fuel tank components 

*   **Scientific Instruments:

**    *   Telescope and microscope frames    

*   Metrology equipment standards    

*   Seismograph components    

*   Laboratory measurement apparatus 

*   **Electronics & Semiconductors:

**    *   Lead frames for integrated circuits    

*   Microwave cavity resonators    

*   Mask frames for photolithography    

*   Chip mounting substrates 

*   **Energy Industry:

**    *   LNG transport and storage systems    

*   Pipeline compensation loops    

*   Nuclear reactor instrumentation 

*   **Precision Manufacturing:

**    *   Gauge blocks and calibration standards    

*   Precision ruler and tape blades    

*   Watch and clock components

 --- #### **7. Key Characteristics & Advantages

** *   **Ultra-Low Thermal Expansion:

** Exceptionally low CTE (1.3 x 10⁻⁶/°C) at room temperature 

*   **Excellent Dimensional Stability:

** Maintains precise dimensions across temperature variations 

*   **Good Mechanical Strength:

** Adequate strength for structural applications 

*   **Superior Cryogenic Performance:

** Maintains properties at extremely low temperatures 

*   **Good Fabricability:

** Can be machined, formed, and welded using standard techniques 

*   **Predictable Behavior:** Well-characterized thermal and mechanical properties 

*   **Proven Reliability:

** Over a century of successful applications in critical systems 

*   **Cost-Effective Stability:

** Provides unparalleled dimensional stability at reasonable cost

 --- **Disclaimer:

** *Invar® is a registered trademark of ArcelorMittal. The values provided are typical and for informational purposes only. For critical applications, always consult the official material data sheets from the supplier and relevant design codes. Proper heat treatment may be required to achieve optimal dimensional stability for specific applications.*

Packing of Invar 36,Alloy 36,UNS K93600

Standard Packing: 

Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and steel drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 1681 gallon liquid totes Special package is available on request.