Discover a small history
The word aluminium is derived from the ancient Roman alumen (alum). German scientists Porter (JHPott) with alum made of aluminum oxide in 1746. 1807 Englishman David (H.Davy) trying to get electrolysis of molten aluminum metal. In the second year, David named the metal as alumium and changed it to aluminum. In 1825, the Danish scientist HCOersted used potassium amalgam to reduce anhydrous aluminum chloride to obtain a few milligrams of metal aluminum. In 1827, German scientist F. Wohler used potassium to reduce alumina to obtain a small amount of metal aluminum. In 1854, the French scientist SC Deville used sodium to reduce NaAlCl4 with salt to make aluminum, and built a factory to produce some helmets, tableware and toys, which are expensive and equivalent to gold. In 1886 (Hall) and (French) Herult (Heroult) also proposed a cryolite-alumina molten salt electrolytic aluminum method. In 1888, Pittsburgh established the first electrolytic aluminum plant in the United States, and aluminum production entered a new stage. In 1956, the world's aluminum production exceeded copper , ranking first in non-ferrous metals.
1. Natural properties Aluminum is a light metal. Its compounds are widely distributed in nature. The content of aluminum in the earth's crust is about 8% by weight, second only to oxygen and silicon. The metal species, second only to iron and steel, the second largest category of metal. Aluminum has special chemical and physical properties and is one of the most commonly used industrial metals. It is not only light weight, firm in texture, but also has good ductility, electrical conductivity, thermal conductivity, heat resistance and nuclear radiation resistance. An important basic raw material for economic development.
Aluminum has a specific gravity of 2.7 and a density of about 1/3 of that of a general metal. The commonly used aluminum wire has a conductivity of about 61% of copper and a thermal conductivity of half that of silver . Although pure aluminum is extremely soft and ductile, it is reliably cold worked and alloyed to harden it. Bauxite is an important source of aluminum. It takes about two pounds of bauxite to make one pound of alumina, and two pounds of alumina to make one pound of aluminum.
2. Classification of aluminum varieties According to the main component content of aluminum ingots, it can be divided into three categories: high-grade pure aluminum (aluminum content 99.93%-99.999%), industrial high-purity aluminum (aluminum content 99.85%-99.90%), industrial pure aluminum (Aluminum content 98.0% - 99.7%).
3, aluminum quality standards The quality of aluminum ingots must comply with the national standard GB/1196-1993 standard. Among them, the aluminum content of AL99.80 and AL99.70 shall not be less than 99.80 and 99.70. According to the national standard (GB/T1196-93), it should be called “aluminum ingot for remeltingâ€, but everyone is used to “aluminum ingotâ€. It is produced by electrolysis using alumina-cryolite. There are two main categories of aluminum ingots after entering industrial applications: cast aluminum alloys and deformed aluminum alloys. Cast aluminum and aluminum alloys are castings for the production of aluminum by casting ; deformed aluminum and aluminum alloys are processed products of aluminum by pressure processing: plates, strips, foils, tubes, rods, profiles, wires and forgings. According to the national standard for aluminum ingots for remelting, "the aluminum ingot for remelting is divided into six grades according to its chemical composition, namely Al99.85, Al99.80, Al99.70, Al99.60, Al99.50, Al99.00" (Note: The number after Al is the aluminum content). At present, some people call "A00" aluminum, which is actually aluminum with a purity of 99.7%, and is called "standard aluminum" in the London market. Everyone knows that China’s technical standards in the 1950s came from the former Soviet Union. “A00†is the Russian brand in the Soviet national standard. “A†is the Russian alphabet, not the English “Aâ€, nor the Chinese alphabet. "A". When it is in line with international standards, it is more accurate to call "standard aluminum". Standard aluminum is an aluminum ingot containing 99.7% aluminum, which is registered on the London market.
4. Main uses of aluminum For nearly 50 years, aluminum has become one of the most widely used metals in the world. In the construction industry, aluminum is widely used due to its stability in air and excellent appearance after anode treatment; aluminum alloy materials are also widely used in the aviation and defense military departments; high-strength steel wires are commonly used in power transmission. Reinforced aluminum cable; in addition, automotive manufacturing, container transportation, daily necessities, household appliances, machinery and equipment require a large amount of aluminum.
With the rapid development of the national economy, China has gradually become a "global processing base". The basic industries such as steel and nonferrous metals have flourished. In recent years, the output of electrolytic aluminum has soared, making China the largest aluminum producer in the world. [next]
At the same time, China is also playing a major role in the global aluminum market. Due to the strong growth of demand in China in recent years, the changes in China's supply and demand fundamentals directly affect the balance of the world's aluminum market through international trade.
However, there are many uncertainties in China's primary aluminum supply. This uncertainty comes from the continued tight supply of alumina, partly due to the power shortage caused by the shortcomings of the Chinese system. Due to the limitations of its own resources and the lack of investment during the period of mining and primary mineral product development, China has experienced serious shortage of raw materials in recent years. It needs to purchase a large amount of alumina from abroad every year. Ten thousand tons of alumina.
In addition to the raw material alumina and electrical energy issues, the government has begun to impose restrictions on the supply of primary aluminum, which is higher than the domestic consumption growth, in order to control the current overheated electrolytic aluminum industry. But whether it is power shortage or alumina supply, the overall impact on China's aluminum production is limited.
Aluminium nature
The standard electrode potential of aluminum (25 ° C) - 1.662 volts, electrochemical equivalent of 0.3356 g / (ampere hour). The main physical properties of metallic aluminum with a purity of 99.99% are as follows: density (20 ° C) is 2.70 g / cm 3 ; melting point is 660.1 ° C; boiling point is 2520 ° C; average specific heat (0 ~ 100 ° C) is 917 J / kg • K; heat of fusion is 10.47kJ/mol; heat of vaporization is 291.4 kJ/mol (estimated value); thermal conductivity (0-100°C) is 238W/(m•K); resistivity (20°C) is 2.67μΩ/ Cm.
Aluminum resources
The average content of aluminum in the earth's crust is 7.47%, which is the third highest in oxygen and silicon. The world's identified bauxite reserves are about 25 billion tons of industrial reserves, plus a total of about 35 billion tons of prospective reserves. Countries with abundant reserves and large production volumes include Guinea, Australia, Brazil, Jamaica, and India. The bauxites in these countries are mostly high-iron, low-silicon gibbsite-type, suitable for the production of alumina using the simpler Bayer process. China's proven bauxite deposits are mainly distributed in Henan, Shanxi, Guizhou, Shandong, Guangxi and other places. Except for some areas, they are low-iron and high-alumina diaspore. China is also rich in mineral alunite. Zhejiang and Anhui provinces have billion tons of potassium alumite resources, which are raw materials for the production of alumina and potash. In addition, there are abundant nepheline resources found in Yunnan and other places.
Aluminum preparation
The preparation of aluminum includes the production of alumina from ore and the production of metal aluminum from alumina. The alumina production methods mainly include the Bayer process, the soda lime sintering method, and the Bayer-sintering combination method. The Bayer process has been the main method of producing alumina, and its production accounts for about 95% of the world's total alumina production.
Characteristics of aluminum The most important characteristic of aluminum is its light weight, specific gravity of 2.7 and a density of about 1/3 of that of ordinary metals. The conductivity of commonly used aluminum wires is about 61% of copper, aluminum also has a high thermal conductivity, which is half of silver, and the melting point of pure aluminum is 660 degrees Celsius. Although pure aluminum is extremely soft and ductile, it is still reliably cold worked and alloyed to harden it. The commonly used alloying elements are copper, magnesium , manganese , chromium , niobium and iron. Aluminum is a very useful metal because of its resistance to many chemicals and its durability for outdoor use. Clay-like bauxite is an important source of aluminum. Bauxite contains 50-60% alumina. It takes about 10 kilowatts of electricity to make a pound of aluminum, so cheap electricity is very important to the aluminum industry. The largest use of aluminum is in the transportation and construction industries. Aluminum is widely used in the manufacture of various vehicles. In the construction industry, due to the stability of aluminum in air and the excellent appearance after anodizing, it is greatly affected by the application of high-strength steel wire-reinforced aluminum cables. Kitchen utensils are the earliest use of aluminum and are still a very large market today. Based on its chemical resistance, aluminum is particularly suitable for use in the manufacture and storage of chemicals. Aluminum has a high affinity for oxygen and is therefore widely used as an oxygen scavenger for steel and iron. The world's aluminum production is concentrated in the United States, the former Soviet Union, Canada, Australia, Brazil, Norway, and the above-mentioned countries produce more than 60% of global production. In addition to new aluminum, aluminum is also a high proportion of recycled aluminum. The recycled aluminum is divided into old material recovery (mainly from beverage cans and automotive waste) and new material recovery (aluminum chips during the addition process). Two. Due to the increased awareness of environmental protection, the amount of recycled aluminum has reached a new high every year. Since the 1980s, the world aluminum price has been steadily frustrated. The biggest reason is that the Soviet Union dismantled a large amount of aluminum for the West in exchange for foreign exchange. The most obvious impact is that the inventory of LME is 315,600 tons from the end of 1990. It rose to more than 1.44 million tons. Because of its good chemical properties, aluminum has replaced many raw materials, such as beverage cans and building materials. The largest consumption of aluminum in the United States occurs in cans and cans, accounting for 28% of the total US consumption, followed by about 19 in the transportation industry. %, then about 18% of the housing and construction industry.
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