Invar 36,Alloy 36 Foil,Shim,UNS K93600,E FORU

British Specs:，American Specs: ASTM F1684 MIL-S-16598 Tooling plate ASTM B388 Sheet & strip ASTM B753 K93050 Free-cut Invar，German Specs:WS 1.3912

### **Invar 36 / Alloy 36 Foil & Shim (UNS K93600) - Product Introduction** #### **Overview** Invar 36, also known as Alloy 36 or UNS K93600, is a nickel-iron alloy renowned for its exceptionally low Coefficient of Thermal Expansion (CTE). The **Foil** and **Shim** forms of this alloy represent its thinnest and most precise gauges. **Foil** is typically defined as material under 0.005" (0.127 mm) thick, while **Shim** stock is used as a thin spacer for precise gap-filling. These products are engineered for ultra-precision applications where minimal mass and maximum dimensional stability are paramount. #### **Key Characteristics of Alloy 36 Foil/Shim** * **Ultra-Low Thermal Expansion:** Maintains the characteristic CTE of approximately **1.6 x 10⁻⁶/°C** (20-100°C), even in thin gauges, preventing thermal stress and misalignment. * **Precision Gauge Control:** Manufactured to extremely tight thickness tolerances, essential for applications like shimming and electronic components. * **Excellent Formability:** In the annealed condition, the foil can be easily stamped, blanked, and formed into complex, delicate parts. * **High Surface Quality:** Supplied with a uniform, smooth surface suitable for plating, coating, or direct use in sensitive assemblies. --- #### **1. Chemical Composition** The unique properties of Invar 36 are achieved through a tightly controlled chemical composition. | Element | Content (%) | | :--- | :--- | | **Nickel (Ni)** | 36.0% min | | **Iron (Fe)** | Balance | | **Carbon (C)** | 0.10% max | | **Manganese (Mn)** | 0.60% max | | **Silicon (Si)** | 0.40% max | | **Phosphorus (P)** | 0.025% max | | **Sulfur (S)** | 0.025% max | | **Cobalt (Co)** | 0.50% max | | **Chromium (Cr)** | 0.25% max | --- #### **2. Physical Properties** | Property | Value / Description | | :--- | :--- | | **Density** | 8.11 g/cm³ (0.293 lb/in³) | | **Melting Point** | ~1427°C (2600°F) | | **Thermal Expansion Coefficient (CTE)** | **1.6 x 10⁻⁶/°C** (20-100°C)
2.7 x 10⁻⁶/°C (20-300°C) | | **Thermal Conductivity** | 10.5 W/m·K (at 20°C) | | **Specific Heat** | 515 J/kg·K (at 20°C) | | **Magnetic Properties** | Ferromagnetic at room temperature. Becomes non-magnetic (paramagnetic) above its Curie temperature of ~279°C (534°F). | --- #### **3. Typical Mechanical Properties (Annealed Condition)** *Properties are for annealed foil/shim and can vary with thickness and temper.* | Property | Value | | :--- | :--- | | **Tensile Strength** | 450 - 550 MPa (65 - 80 ksi) | | **Yield Strength (0.2% Offset)** | 250 - 310 MPa (36 - 45 ksi) | | **Elongation** | 20% - 35% (varies with gauge) | | **Hardness (Rockwell B)** | 70 - 85 HRB | --- #### **4. Product Applications** Alloy 36 Foil and Shim are used in the most demanding precision applications across high-tech industries. * **Electronics & Semiconductor Packaging:** * **Micro-electronic Lead Frames:** For ultra-miniaturized components where stability prevents failure during soldering and operation. * **Interposer Layers & Conductive Spacers:** Within high-density circuit assemblies. * **EMI/RFI Shielding Gaskets:** Utilizing both the magnetic and structural properties. * **Aerospace & Aviation:** * **Precision Shims:** For critical alignment in jet engines, airframes, and optical systems where components are subject to wide temperature ranges. The low CTE ensures shim thickness remains constant. * **Honeycomb Core Material:** Foil is often formed into honeycomb structures for lightweight, stable composite panels. * **Advanced Manufacturing & Tooling:** * **Composite Curing Bleeder Plies:** Used in out-of-autoclave (OOA) processes; the foil's stability ensures consistent pressure and vacuum bagging. * **Thermal Management Spacers:** Between components with different CTEs to mitigate thermal stress. * **Scientific & Research Instruments:** * **Cryogenic Seals and Spacers:** In scientific equipment operating at liquid helium or nitrogen temperatures. * **Sensor Diaphragms and Components:** Where thermal stability is critical for measurement accuracy. --- #### **5. International Standards** Invar 36 Foil and Shim are governed by standards for thin strip and foil, with a strong emphasis on dimensional tolerances. | Standard Body | Standard Designation | Title / Scope | | :--- | :--- | :--- | | **UNS** | **K93600** | Unified Numbering System | | **ASTM** | **ASTM F1684** | Standard Specification for Iron-Nickel and Cobalt-Nickel Alloy **Sheet, Strip, and Plate** *(This is the primary specification, covering down to foil thicknesses.)* | | **AMS** | **AMS 7725** | Alloy 36, Sheet, Strip, and Plate (Aerospace Material Specification) | | **EN / Euronorm** | **EN 1.3912 / Ni36** | Wrought Steel Products | | **DIN** | **DIN 1.3912 / Ni36** | German Institute for Standardization | | **JIS** | **JIS NCF 2 / NILO 36** | Japanese Industrial Standards | *Note: For foil and shim products, the **ASTM F1684** standard is critical, but procurement often relies heavily on **customer-specific drawings and tolerance requirements** that exceed standard commercial limits, particularly for thickness, flatness, and surface finish.* --- #### **Conclusion** Invar 36 (Alloy 36) Foil and Shim, UNS K93600, are the pinnacle of precision low-expansion materials. Their ability to be produced in extremely thin gauges while maintaining unparalleled thermal stability makes them indispensable for microelectronics, precision instrumentation, and aerospace engineering. Success in these demanding applications requires not only material certified to standards like **ASTM F1684** but also a supplier capable of delivering the exceptional gauge control and quality that foil and shim products require.

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 2402 gallon liquid totes Special package is available on request.