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Alloy42 (also known as Ni42, Fe-Ni42, UNS K94100, German Standard W. Nr 1.3917, ASTM F30) is a high-performance iron-nickel based constant expansion precision alloy, belonging to the derivative model of Invar alloy series, with 4J42 as its Chinese national standard grade. As a core sealing material in the electro-vacuum industry, Alloy42 has a stable low coefficient of thermal expansion in the wide temperature range of -60℃~400℃, which is highly matched with the expansion coefficient of molybdenum group soft glass, alumina ceramics and other materials. It is widely used in high-end fields such as electronic packaging, precision instruments, aerospace, and is the preferred material that balances dimensional stability and processing performance.
Element | Content Range (%) |
Ni | 41.5~42.5 |
Fe | Balance |
C | ≤0.05 |
Si | ≤0.30 |
Mn | ≤0.60 |
P | ≤0.020 |
S | ≤0.020 |
Performance Indicator | Parameter Value | Practical Description |
Density | 8.2 g/cm³ | Standard value at 20℃, suitable for precision structural design |
Coefficient of Thermal Expansion (20~400℃) | (4.5~5.2)×10⁻⁶/℃ | Highly matched with molybdenum group soft glass, no stress during sealing |
Curie Temperature | Approx. 360℃ | Higher than 4J36/4J40, wider applicable temperature range |
Resistivity | Approx. 0.45 μΩ·m | Standard value at 20℃, suitable for conductive needs of electronic devices |
Thermal Conductivity | 16.7 W/(m·K) | At 20℃, ensuring uniform heat conduction |
Specific Heat Capacity | 502 J/(kg·K) | At 20℃, stable performance when temperature changes |
Melting Point | 1450~1500℃ | Suitable for high-temperature processing and sealing processes |
Performance Indicator | Typical Value | Application Reference |
Tensile Strength | ≥485 MPa | Meet the strength requirements of structural parts |
Yield Strength | ≥205 MPa | Ensure dimensional stability after processing |
Elongation | ≥30% | Facilitate complex processing such as cold rolling and deep drawing |
Hardness (HB) | ≤190 | Easy to cut and form |
Elastic Modulus | 158 GPa | Suitable for precision instrument structural design |
High Matching Constant Expansion: The coefficient of thermal expansion is almost constant in the temperature range of 20~300℃. The interface stress is extremely small when sealing with soft glass and ceramics, ensuring air tightness and long-term structural stability, and solving the problem of sealing cracking.
Stable Organizational Structure: Single-phase austenitic structure, no magnetic transformation, performance is not easy to decay after hot and cold processing, and dimensional accuracy is controllable.
Excellent Corrosion Resistance: It performs well in the atmosphere, fresh water and mild corrosive media, suitable for harsh environments such as electronic packaging and medical equipment.
Excellent Processing Performance: Easy to hot and cold process, weld and cut, can be made into various forms to meet the customization needs of different scenarios.
Hot and Cold Processing: Due to the characteristics of austenitic structure, it can be easily cold-rolled, hot-rolled and forged, and can be made into various forms such as thin plates, strips, wires, bars and pipes.
Welding Performance: Supports arc welding, resistance welding and brazing. The weld performance is consistent with the matrix without obvious performance attenuation, suitable for the manufacture of sealed structures.
Machining Performance: Similar to austenitic stainless steel, it can be cut at low speed with carbide tools, with high processing efficiency and controllable surface accuracy.
Deep Drawing Performance: After soft annealing, it has excellent deep drawing and stretching performance, which can be used to manufacture complex-shaped electronic component frames and seals.
Soft Annealing: Hold at 850~900℃ for 1~2 hours, air cool or furnace cool, mainly used to improve processing performance and facilitate subsequent forming.
Aging Treatment: Aging at 300~500℃ as needed can effectively stabilize the material size and avoid deformation during use.
Pre-sealing Treatment: Bright annealing or pickling is required to ensure the surface is clean and free of impurities, improving sealing quality and air tightness.
