A precision alloy with abnormal thermal expansion characteristics, also known as thermal expansion alloy. Expansion alloy is divided into low expansion alloy and fixed expansion alloy, the latter is also called sealing alloy. The average expansion coefficient of the low-expansion alloy below the bending point is lower than 3×10-6°C-1; the average expansion coefficient of the constant-expansion alloy below the bending point is about (4-10)×10-6°C-1. In addition to having a specific thermal expansion coefficient, expansion alloys also require good sealing properties, weldability, corrosion resistance, machinability and easy cutting properties according to different uses, and are not allowed to cause expansion characteristics within the use temperature range. Obviously changing phase transition.

1. Iron-nickel-cobalt glass sealing alloy FeNi29Co17

Grade: 4J29 (Kovar) is also called Kovar alloy (Fe54%, Ni29% and Co17%), and its expansion coefficient is 4.7×10-6/℃. Executive standard: YB/T 5231-93, use: used to make matching sealing with hard glass. Suitable for electric vacuum devices such as launch tubes, oscillating tubes, ignition tubes, transistors, tube seal plugs, relay shells, etc. It has a certain linear expansion coefficient in the temperature range of -60℃~+40O℃, which can be matched and sealed firmly with hard glass.

Supply status: strip, wire, round steel, forging [1

2. Porcelain sealing alloy Grades: Vacodil42, 4J42, 4J33, 4J34

Executive standard: YB/T 5234-93

Uses: Used for making and sealing ceramics. Suitable for matching sealing of electric vacuum devices and 95% Al2O3 ceramics. It has a linear expansion coefficient similar to that of 95% Al2O3 ceramics in the temperature range of -60℃~+600℃.

Supply status: strip, wire, round steel, forging.

3. Low expansion alloy FeNi36, FeNi32CO4Cu, Invar, Invar alloy

Grade: 4J32, 4J36 4J38, 4J40, executive standard: YB/T 5241-93 Product performance characteristics are mainly used: 4J32, 4J36 alloys and high temperature and low temperature and low temperature Expanded 4J40 alloy and free-cutting 4J38 alloy. 4J36 has a very low thermal expansion coefficient and can maintain a fixed length in a wide temperature range.

4j29 (Kovar alloy)

The iron-nickel-cobalt glass-sealing alloy 4J29 (also known as Kovar wire kOVAR) is mainly suitable for the glass-sealing alloy for matching and sealing electrical components with hard glass, soft glass and ceramics, and its state is hard and soft. The specification is 0.32mm or more. The grade and chemical composition of the alloy meet the requirements of Table 1.

The tensile strength of the wire meets the requirements of Table 2

The tensile strength of the strip meets the requirements of Table 3

The average linear expansion coefficient of the alloy meets the requirements of Table 4

Typical expansion coefficient of alloy