Alloy 39,Low Expansion 39 Alloy,，EFORU

### **Alloy 39 / Low Expansion 39 Alloy (UNS K94600) - Technical Datasheet** --- #### **1. Overview** **Alloy 39** (commercially known as **Low Expansion 39 Alloy**) is a nickel-iron controlled expansion alloy designed to exhibit an extremely low and predictable coefficient of thermal expansion (CTE) at cryogenic to moderate temperatures. This alloy belongs to the family of "Invar-type" alloys, with its composition optimized to minimize dimensional changes over a specific temperature range, typically from -100°C to +200°C. Its primary value lies in its dimensional stability, making it critical for applications where precise dimensions must be maintained despite temperature fluctuations. --- #### **2. Chemical Composition (Weight %)** The composition is precisely balanced to achieve the desired low expansion characteristics. | Element | Content (%) | Role & Benefit | |---------|-------------|----------------| | **Nickel (Ni)** | 39.0 - 41.0 | Primary element controlling the thermal expansion coefficient. The ~39% content targets the minimum CTE in the Fe-Ni system. | | **Iron (Fe)** | Balance | Base element of the alloy. | | **Cobalt (Co)** | ≤ 0.5 | Controlled residual element. | | **Manganese (Mn)** | ≤ 0.50 | Aids in deoxidation during melting. | | **Silicon (Si)** | ≤ 0.25 | Improves fluidity and acts as a deoxidizer. | | **Carbon (C)** | ≤ 0.05 | Kept low to prevent carbide formation and embrittlement. | | **Sulfur (S)** | ≤ 0.020 | Controlled impurity to improve workability. | | **Phosphorus (P)** | ≤ 0.020 | Controlled impurity to prevent embrittlement. | --- #### **3. Physical Properties** The properties are characterized by exceptional dimensional stability. | Property | Value | |----------|-------| | **Density** | 8.11 g/cm³ (0.293 lb/in³) | | **Melting Point** | ~1430°C (2600°F) | | **Specific Heat (20°C)** | 515 J/kg·K | | **Thermal Conductivity (20°C)** | 11.0 W/m·K | | **Mean Coefficient of Thermal Expansion (CTE)** | **≤ 1.5 × 10⁻⁶/°C (20-100°C)**
**~2.5 × 10⁻⁶/°C (20-200°C)** | | **Curie Temperature** | ~230°C (445°F) | | **Electrical Resistivity** | 0.75 μΩ·m | | **Modulus of Elasticity** | 145 GPa (21 × 10⁶ psi) | | **Magnetic Properties** | Ferromagnetic at room temperature | --- #### **4. Mechanical Properties (Annealed Condition)** The alloy provides moderate strength with good machinability. | Property | Value | |----------|-------| | **Tensile Strength** | 510 MPa (74 ksi) | | **Yield Strength (0.2% Offset)** | 280 MPa (41 ksi) | | **Elongation (in 50mm)** | 35% | | **Hardness (Rockwell B)** | 65-80 HRB | --- #### **5. Product Applications** **Alloy 39** is essential in precision instruments and scientific equipment: - **Precision Instrumentation:** - Laser cavity frames and optical mounting systems - Surveying equipment and precision scales - Scientific instrument frames - **Aerospace & Defense:** - Aerospace guidance systems - Inertial navigation platforms - Satellite structural components - **Electronics & Semiconductors:** - Mask alignment systems in photolithography - Critical dimensions in semiconductor manufacturing equipment - **Energy Sector:** - Components in LNG equipment - Cryogenic storage and transfer systems - **Scientific Research:** - Telescope structures - Interferometer components - Metrology equipment --- #### **6. International Standards** The material is covered by various international specifications: | Standard | Specification | |----------|---------------| | **ASTM** | ASTM F1684 - Standard Specification for Iron-Nickel and Iron-Nickel-Cobalt Alloys for Low Thermal Expansion Applications | | **UNS** | UNS K94600 | | **AMS** | AMS 3911 | | **European** | EN 10111:2008 | | **ISO** | ISO 9447:2019 | --- #### **7. Fabrication & Handling Notes** - **Machining:** Can be machined using standard methods for austenitic stainless steels - **Heat Treatment:** Stress relief annealing at 425-540°C (800-1000°F) is recommended after severe forming - **Welding:** Can be welded using GTAW (TIG) and GMAW (MIG) methods with matching composition filler metal - **Cleaning:** Requires thorough cleaning to prevent contamination during high-temperature applications --- #### **Summary** **Alloy 39 (Low Expansion 39 Alloy)** represents a specialized class of nickel-iron alloys engineered for exceptional dimensional stability across temperature variations. Its controlled low thermal expansion coefficient makes it indispensable in precision engineering applications where minimal thermal growth is required. The alloy finds critical use in aerospace guidance systems, scientific instruments, semiconductor manufacturing equipment, and other high-precision applications where thermal dimensional stability is paramount. Governed by international standards including ASTM F1684, it continues to be a fundamental material in advanced technology sectors requiring uncompromising precision.

Packing of 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 1709 gallon liquid totes Special package is available on request.