Invar 36 (UNS K93600 / 1.3912) is a nickel-iron alloy containing 36% nickel, specifically engineered to achieve an exceptionally low coefficient of thermal expansion—approximately one-tenth that of carbon steel at temperatures up to 204°C (400°F). This near-zero expansion characteristic makes it the preferred material for applications requiring extreme dimensional stability across temperature fluctuations, including precision tooling, cryogenic components, optical systems, and bimetallic devices .
1. Product Specifications & Physical DataZYTC Alloy supplies Invar 36 in comprehensive mill forms for aerospace, metrology, and industrial applications requiring verified low-expansion properties. Available Forms: Round bar, sheet, plate, tube, and pipe . Specifications: ASTM F1684, DIN 17745, GB/T 14985 (4J36), UNS K93600 .
| Chemical Composition (Weight %) | Invar 36 Specification |
|---|
| Nickel (Ni) | 35.0 - 38.0 | | Iron (Fe) | Balance | | Carbon (C) | 0.10 max. | | Manganese (Mn) | 0.60 max. | | Silicon (Si) | 0.35 max. | | Phosphorus (P) | 0.025 max. | | Sulfur (S) | 0.025 max. | | Chromium (Cr) | 0.50 max. | | Molybdenum (Mo) | 0.50 max. | | Cobalt (Co) | 1.0 max. |
| Physical Properties | Metric | Imperial |
|---|
| Density | 8.1 g/cm³ | 0.293 lb/in³ | | Melting Range | 1430 - 1450°C | 2605 - 2640°F | | Curie Temperature | 277°C (approx.) | 530°F (approx.) | | Thermal Conductivity (RT) | 10.1 W/m·K | 70 BTU·in/hr·ft²·°F |
| Mechanical Properties (Annealed) | Metric | Imperial |
|---|
| Tensile Strength | 490 MPa | 71,000 psi | | Yield Strength (0.2% offset) | 240 MPa | 35,000 psi | | Elongation at Break | 42% | 42% |
2. Fabrication & Material ComparisonInvar 36 (UNS K93600 / 1.3912) requires careful thermal processing to maintain its low-expansion characteristics, as cold working and improper heat treatment can alter the coefficient of thermal expansion. Annealing: Full annealing at 830°C (1525°F) followed by slow cooling to relieve stresses and restore stable expansion properties. Time at temperature depends on section size . Hot Working: 1010-1095°C (1850-2000°F); avoid working in the 538-760°C range where hot shortness may occur . Cold Working: Good ductility permits forming; work-hardening rate moderate. Cold working increases strength but may affect CTE; final anneal recommended for critical dimensional applications . Machining: Similar to austenitic stainless steels with moderate work-hardening; sharp tools and rigid setups recommended . Welding: Readily welded using GTAW, GMAW, and resistance welding; matching filler metal recommended (ERNiFe-36). Welding causes local CTE changes in heat-affected zone; post-weld annealing may be required for critical applications . Material Comparison: vs. Standard Steels: CTE approximately 10× lower than carbon steel below 200°C; selected where thermal distortion cannot be tolerated . vs. Invar 39/42: Higher nickel content shifts expansion curve; 36 offers the lowest expansion near room temperature . vs. Super Invar (32Ni-4Co): 36 has better machinability and fabricability; Super Invar offers even lower expansion over narrower range . vs. Kovar: 36 prioritized for minimal absolute expansion; Kovar prioritized for expansion matching with glass/ceramics .
3. ApplicationsTooling & Dies: Composite molds, layup tools for aerospace composites, precision measuring instruments, gauge blocks Cryogenic Components: LNG storage and transport equipment, cryogenic tanks, piping systems Laser & Optical Systems: Laser housings, optical benches, telescope components, alignment structures Aerospace & Defense: Structural components requiring dimensional stability, satellite components, instrument housings Electronics: Microwave cavities, semiconductor equipment, precision electronic housings Bimetallic Systems: Thermostatic strips, compensating elements in timing devices
Contact ZYTC Alloy for certified Invar 36 materials with complete traceability, ASTM F1684 specifications, technical datasheets, and competitive pricing on standard sizes or custom-fabricated components. Email: daisy@zytcsteel.com WhatsApp/WeChat: +86 17335753350 |
