4J29, also known as Kovar alloy, is an Fe-nickel-cobalt alloy that is widely used in industry because of its unique thermal expansion properties.
Chemical composition
The chemical composition of 4J29 is the key factor determining its performance. According to the GB/T 15018-1994 standard, the main components of this alloy include:
| Element Symbol | Element Name | Content Range |
| Ni | Nickel | 28.5% – 29.5% |
| Co | Cobalt | 16.8% – 17.8% |
| Fe | Iron | Allowance |
| C | Carbon | ≤0.03% |
| Mn | Manganese | ≤0.50% |
| Si | Silicon | ≤0.30% |
| P | Phosphorus | ≤0.020% |
| S | Sulfur | ≤0.020% |
| Cu | Copper | ≤0.20% |
| Cr | Chromium | ≤0.20% |
| Mo | Molybdenum | ≤0.20% |
Under the condition that the average linear expansion coefficient meets the standard requirements, the content of nickel and cobalt is allowed to deviate from the range specified in Table 1-2. In addition, the contents of aluminium, magnesium, zirconium and titanium should each not exceed 0.10%, and their total amount should not exceed 0.20%.
Physical properties
The physical properties of 4J29 are as follows:
1. Density: 8.17 grams per cubic centimeter
2· Resistivity: 0.46Ω* square centimeter/meter
3· Conductivity: 2.174 * 1,000,000 S/m
4· Thermal conductivity: 0.046 kcal /cm ³ ℃
These physical property data are crucial for material selection when designing and applying alloys.
Heat treatment system
The heat treatment system of 4J29 has a significant impact on its performance. The performance test samples for the coefficient of expansion and low-temperature microstructure stability as stipulated in 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.
Application Overview
4J29 is mainly used for glass sealing of electronic vacuum components such as emitter tubes, oscillator tubes, igniter tubes, magnetrons, transistors, sealed plugs, relays, lead wires of integrated circuits, chassis, casings, brackets, etc. In application, the selected glass should be matched with the coefficient of expansion of the alloy. Strictly test its low-temperature microstructure stability according to the usage temperature. Appropriate heat treatment should be carried out during the processing to ensure that the material has good deep drawing and drawing performance.
