Silver is favored by people (especially women) because of its attractive white luster, high chemical stability and collection and ornamental value. Therefore, it has the reputation of women's metal, and is widely used as jewelry, decorations, silverware, tableware, congratulatory gifts, medals, commemorative coins and so on. Silver ornaments have a broad market in developing countries, and silver tableware is welcomed by families. Silver commemorative coins are beautifully designed, with small circulation, and have the function of maintaining and increasing value, which is favored by coin collectors and coin investors. In the 1990s, the amount of silver used for coinage alone remained around 1 1,000 ~11,500t every year, accounting for about 5% of the silver consumption.
Copper is a non-ferrous metal closely related to human beings. Widely used in electric power, light industry, machinery manufacturing, construction industry, national defense industry and other fields, second only to aluminum in the consumption of non-ferrous metal materials in China. Copper is a red metal and a green metal. It is said to be a green metal mainly because it has a low melting point and is easy to be remelted and smelted, so it is quite cheap to recycle.
In our life, iron can be regarded as the most useful, cheapest, richest and most important metal. Iron is the main element of carbon steel and cast iron. In industrial and agricultural production, equipment manufacturing, railway vehicles, roads, bridges, ships, docks, houses and civil engineering are inseparable from steel components. China produces more than 400 million tons of steel and 33.5 million tons of castings every year. The annual output of steel represents the modernization level of a country.
Aluminum and its alloys are one of the most widely used and economical materials at present. Since 1956, the world's aluminum output has surpassed copper, ranking first among non-ferrous metals. At present, the output and consumption of aluminum (in tons) are second only to steel and become the second largest metal used by human beings. Moreover, aluminum is very rich in resources. According to preliminary calculation, the mineral reserves of aluminum account for more than 8% of the components of the crust.
Light weight and corrosion resistance of aluminum are two outstanding characteristics of its performance.
The density of aluminum is very small, only 2.7 g/cm. Although it is soft, it can be made into various aluminum alloys, such as hard aluminum, ultra-hard aluminum, rust-proof aluminum, cast aluminum and so on. These aluminum alloys are widely used in aircraft, automobiles, trains, ships and other manufacturing industries. In addition, space rockets, space shuttles and artificial satellites also use aluminum and its aluminum alloys in large quantities. For example, a supersonic plane is composed of about 70% aluminum and its aluminum alloy. Aluminum is also widely used in shipbuilding, and the amount of aluminum used in a large passenger ship often reaches several thousand tons.
The conductivity of aluminum is second only to that of silver, copper and gold. Although its conductivity is only 2/3 of that of copper, its density is only13 of that of copper, so the quality of aluminum wire is only half that of copper wire when transmitting the same amount of electricity. The oxide film on aluminum surface not only has corrosion resistance, but also has certain insulation, so aluminum is widely used in electrical appliance manufacturing, wire and cable industry and radio industry.
Aluminum is a good conductor of heat, its thermal conductivity is three times that of iron. In industry, aluminum can be used to make various heat exchangers, heat dissipation materials and cookers.
Aluminum has good ductility (ductility is second only to gold and silver), and aluminum foil thinner than 0.0 1 mm can be made at 100℃ ~ 150℃. These aluminum foils are widely used for packaging cigarettes, sweets and so on. It can also be made into aluminum wire and aluminum strip, and can be used for rolling various aluminum products.
Because of the dense oxide protective film on the surface of aluminum, it is not easy to be corroded, and it is often used to manufacture chemical reactors, medical instruments, refrigeration devices, petroleum refining devices, oil and gas pipelines and so on.
Aluminum powder has silvery white luster (generally, the color of metal in powder is mostly black), and it is often used as coating, commonly known as silver powder and silver paint, to protect iron products from corrosion and beautiful.
Burning aluminum in oxygen can release a lot of heat and dazzling light, and it is often used to make explosive mixtures, such as ammonium aluminum explosive (made of ammonium nitrate, charcoal powder, aluminum powder, smoke black and other combustible organic substances), combustion mixture (such as bombs and shells made of thermite, which can be used to attack targets or tanks and cannons that are difficult to catch fire) and ignition mixture (such as barium nitrate 68%, aluminum powder 28% and shellac 4%).
Thermite is often used to melt refractory metals and weld railway tracks. Aluminum is also used as a deoxidizer in steelmaking. Aluminum powder, graphite and titanium dioxide (or oxides of other high-melting metals) are evenly mixed in a certain proportion, coated on the metal, and calcined at high temperature to make high-temperature resistant cermets, which have important applications in rocket and missile technology.
Aluminum plate also has good reflective performance, reflecting ultraviolet rays more strongly than silver. The purer aluminum is, the better its reflection ability is, so it is often used to make high-quality mirrors, such as solar cooker mirrors.
Aluminum has sound absorption performance and good sound effect, so the ceilings of broadcast rooms and modern large buildings are also made of aluminum.
Low temperature resistance, when the temperature is low, the strength of aluminum increases rather than brittleness increases, which is an ideal material for low temperature devices, such as cold storage, freezer, Antarctic snowmobile, hydrogen peroxide production devices and so on.