Rare metals have various excellent properties and therefore occupy an increasingly important position in various sectors of the national economy and in various fields of modern science and technology (such as aerospace, energy, electronics, chemical industry, etc.). In some fields, the application of rare metal materials has even become one of the main factors promoting the development of this field at a certain stage. In aviation and aerospace technology, the application of titanium materials with low density and high high-temperature strength has made it possible to manufacture spacecraft and supersonic aircraft with large Mach numbers.
The amount of nickel on earth is very small, only about 6% of iron. Moreover, nickel is mixed with a variety of elements and is not easy to refine, so nickel is relatively expensive. Nickel is an important material for high-temperature alloys. It has unique corrosion resistance and is a "sauce" that can significantly improve the properties of steel and other metals. It is widely used.
Nickel is a silver-white metal with a density of 8.9g/cm3 and a melting point of 1455°C. It has a face-centered cubic lattice, high strength, good plasticity, poor thermal conductivity, and high resistance. In air, water, seawater, many salt solutions, organic media, especially various alkalis, the nickel surface has a strong corrosion resistance due to the formation of a passivation film protective layer on the surface. Its ability to withstand seawater and hot alkali corrosion is outstanding among metals. Pure nickel is commonly used as magnetic materials and alloys in the production of stainless steel. It is also used in electric vacuum parts and corrosion-resistant parts.
Nickel alloy is formed by adding copper, chromium, aluminum, tungsten, titanium, aluminum, etc. to nickel and is used in high temperature and corrosion-resistant applications. Ni-Cu type alloy, also known as Monel alloy, has no low-temperature brittleness, no magnetism, good weldability, and is easy to be formed by cold and hot forming. It is very suitable for making low-temperature equipment, high-temperature alkali-resistant, seawater-resistant and hydrofluoric acid-resistant equipment, such as heat exchange equipment, reactors, containers, and elastic parts. Ni-Cr alloy, also known as Inconel alloy, has good weldability, hot and cold formability and corrosion resistance, excellent high-temperature oxidation resistance, and outstanding nitric acid corrosion resistance. Mainly used for stress-bearing parts and equipment working at high temperatures, and can also be used to make corrosion-resistant parts，Such as heaters, nuclear power evaporators, electric furnace wires, condensers, corrosion-resistant parts of nitric acid production equipment and high-temperature structural parts that work at around 1000°C, such as jet gas turbine turbine blades and gas nozzles. Ni-Mo alloy, also known as Hastelloy, has both high-temperature corrosion resistance and excellent high-temperature comprehensive mechanical properties. It can work under higher temperatures and stresses and has outstanding resistance to hydrochloric acid corrosion. It is often used in equipment parts that are resistant to corrosion such as hydrochloric acid and equipment parts that work for a long time at around 650°C.
