Invar 42 (1.3917 / UNS K94100) is a nickel-iron alloy containing 41% nickel, specifically engineered to match the thermal expansion characteristics of certain glasses and ceramics used in electronic components. With stable performance from -32°C to 275°C (-25°F to 527°F), it provides reliable hermetic sealing in transformer bushings, lighting systems, and electronic tube applications where thermal cycle integrity is essential .
1. Product Specifications & Physical DataZYTC Alloy supplies UNS K94100 in mill forms suitable for glass-to-metal (GTMS) and ceramic-to-metal (CTMS) sealing applications requiring controlled expansion properties and verified compositional consistency. Available Forms: Bar, rod, sheet, strip, plate, and wire . Specifications: ASTM F30, DIN 17745, GB/T 14985 (4J42), UNS K94100 .
| Chemical Composition (Weight %) | Invar 42 Specification |
|---|
| Nickel (Ni) | 41.0 | | Iron (Fe) | 58.0 (Balance) | | Chromium (Cr) | 0.2 max. | | Manganese (Mn) | 0.2 max. | | Carbon (C) | 0.01 max. | | Phosphorus (P) | 0.01 max. | | Sulfur (S) | 0.007 max. | | Aluminum (Al) | 0.001 max. | | Cobalt (Co) | 0.0 |
| Physical Properties | Metric | Imperial |
|---|
| Density | 8.12 g/cm³ | 0.293 lb/in³ | | Curie Temperature | 360°C (approx.) | 680°F (approx.) | | Thermal Conductivity (RT) | 10.5 W/m·K | 73 BTU·in/hr·ft²·°F |
| Mechanical Properties (Annealed) | Metric | Imperial |
|---|
| Tensile Strength | 490 MPa | 71,000 psi | | Yield Strength (0.2% offset) | 248 MPa | 36,000 psi | | Elongation at Break | >40% | >40% | | Hardness (Annealed) | 130 HB | 130 HB |
2. Operating Conditions & Selection CriteriaInvar 42 is specified when designers require a controlled-expansion alloy that maintains CTE matching with specific glass and ceramic compositions across the -32°C to 275°C service range. Service Temperature Range: Optimized for hermetic sealing applications operating from -32°C to 275°C (-25°F to 527°F); suitable for repeated thermal cycling . Expansion Matching: CTE of 5.4-8.5 µm/m·°C across the 30-450°C range enables reliable sealing with specific glass families used in lighting and electronic tube applications . Curie Point: Magnetic transformation at approximately 360°C (680°F) affects expansion behavior; alloy performance is predictable both below and above the Curie temperature within the specified service range . Surface Quality: Suitable for precise surface preparation required for glass sealing; can be cleaned and prepared for oxide bonding . Purity Control: Extremely low aluminum and cobalt content ensures consistent sealing characteristics and prevents unwanted secondary phases .
3. Fabrication & Material ComparisonInvar 42 offers good fabricability with appropriate techniques, though its controlled-expansion characteristics require careful thermal processing to maintain specified CTE values. Annealing: 788°C (1450°F) with appropriate soaking time, followed by controlled cooling to relieve stresses while maintaining desired expansion characteristics . Hot Working: Forging range 1177-1204°C (2150-2200°F); avoid working in temperature ranges that may cause hot shortness . Cold Working: Good ductility permits stamping, drawing, and forming; cold heading achieves optimal results at Rockwell hardness B90-B93 . Machining: Similar to austenitic stainless steels; responds well to conventional methods with sharp tools . Grinding: Soft silicon carbide wheels recommended (80 grit for optimal results) . Welding: Readily welded using all conventional methods; welding parameters must be controlled to minimize heat-affected zone expansion changes . Glass Sealing: Typically pre-oxidized under controlled conditions to form an adherent oxide layer that bonds with molten glass .
ApplicationsElectrical Components: Transformer bushings, capacitor bushings, high-voltage feedthroughs Lighting Systems: Automotive lighting components, industrial lighting, high-intensity discharge lamp seals Electronic Tubes: Vacuum tube components, cathode ray tube parts, microwave device housings Hermetic Seals: Glass-to-metal seals (GTMS) for electronic packages, ceramic-to-metal seals (CTMS) Instrumentation: Sensors requiring thermal stability, precision measurement devices
Contact ZYTC Alloy for certified Invar 42 (1.3917 / UNS K94100) materials with complete traceability, technical datasheets, and competitive pricing on standard sizes or custom-fabricated components. Email:daisy@zytcsteel.com WhatsApp/WeChat: +86 17335753350 |
