Low-expansion alloys are mainly used for parts whose dimensions are almost unchanged at a specific ambient temperature. Mainly includes:
(1) components in precision instruments and optical instruments, such as the arm of precision balance, the swing rod of standard parts, the balance wheel, the external compensation of clocks and watches, etc.
(2) Length ruler. Geodetic baseline ruler;
(3) Various resonant cavities, waveguides for microwave communication, standard frequency generators, etc.
(4) blades and support rods of standard capacitors;
(5) storage tanks and pipelines for liquefied natural gas, liquid hydrogen and liquid oxygen;
(6) thermal bimetallic passivation layer;
(7) Shadow mask in high resolution cathode ray tube (CRT);
(8) Moulds for aviation composite parts;
(9) Used in advanced high-tech products such as satellites, lasers and ring laser gyroscopes.
Since Invar alloy came out 100 years ago, its application field of low expansion coefficient has expanded rapidly. Precision instruments and meters made of Invar alloy, swing rods, balance wheels and hairsprings of standard watches and clocks became the most important products in the early days. In the 1920s, Invar alloy replaced platinum as the lead wire for glass sealing, which greatly reduced the cost. In 1950s and 1960s, the application of Invar alloy was expanding, mainly used in radio tubes, thermostats, thermal bimetals for temperature control, length scales, geodetic baseline scales and so on. In the 1980s and 1990s, it was widely used in microwave technology, liquefied gas storage containers, color TV shadow mask steel belts, core materials of overhead transmission lines, vibration cavities, laser collimator cavities and three-step repetitive lithography camera substrates. With the rapid development of space technology in the 2nd/Kloc-0th century, new application fields include space remote sensor, precision laser, optical measurement system as structural parts and waveguide, supporting system of giant lens in microscope and astronomical telescope, and various scientific instruments that need lenses.