4J29 Kovar Strip Nickel Iron Cobalt Alloy With Low Coefficient Of Thermal Expansion
Product Introduction
Kovar 4J29 strip is a kind of nickel iron cobalt alloy with low thermal expansion coefficient, which is widely used in electronic packaging, aerospace, precision instruments and other fields. Its coefficient of thermal expansion matches that of borosilicate glass and alumina ceramics. It is especially suitable for glass to metal sealing applications, such as high-power transfer valves, transistor pins and bases, integrated circuit lead frames, and photographic flash bulbs. The alloy has a density of 8.2 g/cm ³, a resistivity of 0.48 μ Ω· m, a thermal conductivity of 17 w/(m · K), and a thermal expansion coefficient of about 4.6 × 10 ⁻⁶/℃ in the temperature range of 20 ℃ to 450 ℃. Kovar 4J29 strip has high permeability at room temperature. After specific heat treatment, its hysteresis loss can be significantly reduced, so it can adapt to more precise electronic applications. Its typical mechanical properties include 345 MPa yield strength, 517 MPa tensile strength, 30% elongation and Rockwell B 68 hardness in the annealed state. These characteristics make Kovar 4J29 strip an ideal material for manufacturing parts with high precision and high strength requirements.
Heat treatment system:
The performance test samples for the expansion coefficient and low-temperature tissue stability specified by the standard are heated to 900 ℃± 20 ℃ in a hydrogen atmosphere, held for 1 hour, then heated to 1100 ℃± 20 ℃, held for 15 minutes, and cooled to below 200 ℃ at a rate not exceeding 5 ℃/min before being taken out of the furnace.
Parameter
Specific Applications
- Electronic packaging: Kovar 4J29 strip is widely used in the field of electronic packaging, especially in the connecting parts with glass and ceramic packaging materials, which can effectively reduce the stress problems caused by thermal expansion mismatch.
- Vacuum electronic devices: in the application of vacuum electronic devices, Kovar 4J29 strip is often used as packaging material due to its high corrosion resistance and high temperature performance to ensure the long-term stability and reliability of the device.
- Optical devices and precision instruments: in optical instruments and precision measuring equipment, Kovar 4J29 strip can ensure the dimensional stability of devices under different temperature conditions due to its stable thermal expansion characteristics, especially in precision structural parts, to avoid deformation due to temperature changes.
Advantages and Characteristics
- Low thermal expansion coefficient: the thermal expansion coefficient of Kovar 4J29 strip is about 4.6 × 10 ⁻⁶/℃ in the temperature range of 20 ℃ to 450 ℃, which matches well with the thermal expansion coefficient of glass and ceramics, which makes it able to effectively avoid structural stress caused by thermal expansion mismatch in high-precision assembly.
- Good mechanical properties: Kovar 4J29 strip has high strength and good ductility. Its tensile strength is usually 450-550 MPa, elongation is 30%-40%, and hardness is between hb140-180. This strength and toughness enable it to adapt to a variety of processing methods, especially in electronic packaging and precision instrument manufacturing.
- Excellent electrical performance: the resistivity of Kovar 4J29 strip is 48-52 μ Ω· cm, and its relatively low resistivity can effectively reduce heat and loss in some high-frequency electrical applications. The stability of conductivity also makes it suitable for long-term operation in extreme environments.
- Good machinability: Kovar 4J29 strip has good machinability and formability. Common processing methods include turning, milling, drilling, etc., and it can maintain high dimensional stability in these processing processes. For the production of precision parts, especially in the field with strict requirements for thermal expansion characteristics, precision machining can ensure the high precision and reliability of components.
Processing performance:
- Melting and Casting: Electric arc furnaces or induction furnaces are usually used for melting, and suitable mold materials and cooling rates are required during the casting process to ensure the uniformity and density of the alloy.
- Heat treatment and annealing: Reasonable heat treatment can significantly improve the ductility and processability of 4J29 alloy, providing favorable conditions for subsequent cold or mechanical processing. The annealing temperature is usually between 850 ℃ and 950 ℃.
- Machinability: It has good cutting and formability, and common machining methods include turning, milling, drilling, etc. It can maintain high dimensional stability during these machining processes.
- Welding performance: High energy density welding methods such as laser welding, electron beam welding, or brazing are usually used to ensure the strength and sealing of the joint. During the welding process, it is necessary to strictly control the temperature gradient and cooling rate to prevent cracks or other defects in the welding area.
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Q&A
1. what material is Kovar 4J29?
Kovar 4J29 is a low expansion Fe Ni Co alloy with a linear expansion coefficient similar to that of hard glass, which is widely used in electronics, aerospace and other fields.
2. what is the chemical composition of Kovar 4J29?
The main components of Kovar 4J29 include nickel (28.50%-29.5%), cobalt (16.8%-17.8%), iron (surplus), and a small amount of carbon, silicon, manganese, sulfur, phosphorus, chromium, copper and other elements.
3. how about the physical performance of Kovar 4J29?
The density of Kovar 4J29 is about 8.36 g/cm ³, the melting point is about 1449 ℃, the resistivity is 0.49 μ Ω· m, and the Curie point is about 435 ℃.
4. what is the thermal expansion coefficient of Kovar 4J29?
The linear expansion coefficient of Kovar 4J29 at 20-450 ℃ is 5.1-5.5 μ M/m · ° C, which is similar to that of borosilicate hard glass.
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