Discover a small history
China used tin sill to make tin as early as 3,000 years ago (12th century BC). Warring States "Weekly • Research" details the various uses of tin bronze copper ratio. Ming Dynasty "Heavenly Creations • five gold articles" detailed tin metallurgy technology. The ancient tin-making places in Europe are mainly Cornwall, Bohemia, and Saxony. G. Agricola describes the blast furnace for smelting in the 16th century in the "The Metallurgy", and Concord used tin refining furnaces in the early 18th century.
The nature of tin
Tin is one of the first metals discovered and used by humans. It is silvery white at normal temperature and has three homologous bodies with temperature. It is α tin (gray tin) at 13.2 ° C or lower, β tin (white tin) at 13.2 to 161 ° C, and γ tin (brittle tin) at 161 ° C or higher. Beta tin (white tin) belongs to the tetragonal system.锡 tin (grey tin) is a diamond -type equiaxed crystal system. When β-tin is converted into α-tin, it is powdery. This phenomenon is called “tin plagueâ€. In 1911-1912, the British explorer Scott (RFScott, 1868-1912) went to the Antarctic expedition. He and four assistants arrived at the Antarctic Center on January 7, 1912. Upon returning to the supply point, it was found that tin tanks welded at the supply point were broken in the cold weather, causing the loss of fuel oil and food contamination by oil, which led to the tragedy of the death of Scott and others. At room temperature, a dense oxide film is formed on the tin surface to prevent the continued oxidation of tin. At red heat, tin oxidizes rapidly and volatilizes.
Tin resources
Tin in nature predominantly natural elements, intermetallic present, oxides, hydroxides, sulfides, carbonates, silicates, borates and the like. Has been found to tin and tin-containing minerals fifty types of minerals, mainly minerals of industrial importance are: cassiterite, yellow tin, cylindrical tin, sulfur, lead, tin ore, tin-lead ore stibnite. The countries with rich tin resources in the world are Malaysia, Indonesia, Brazil, and the former Soviet Union. Their reserves are 1.11 million tons, 680,000 tons, 650,000 tons, 300,000 tons, and the total reserves are 100 million tons. The output is more than 25 tons. Ten thousand tons. China's tin reserves are abundant, with an annual output of more than 50,000 tons, one-third of metal tin and one-half of tin concentrate for export.
Preparation of tin
The grade of tin ore is very low, such as 0.2% tin in veins and 0.04% tin in sand mines. Mined ore beneficiation outputs tin 40% -70% of the concentrate. Since the 1970s, in addition to concentrates in China, some minerals containing 1%-5% tin have been selected. This kind of medium ore is difficult to be further enriched by the general beneficiation method, and is replaced by a fumigating furnace to obtain 50% tin-containing soot, thereby improving the total recovery rate of the beneficiation. The tin concentrate selected from sand ore contains less impurities and can be directly smelted; the tin concentrate selected from veins contains more impurities, and some factories first carry out pre-refining treatment and then smelt. The tin-smelting process is usually divided into three stages: pre-refining treatment, reduction smelting and crude tin refining.
Use of tin
Pure tin with weak organic acids slow action, and therefore used in the manufacture tin plate (belt), commonly known as horse iron, as food packaging materials. Pure tin can also be used as a coating for certain mechanical parts. Tin is easy to process into tubes, foils, wires, strips, etc., and can also be made into fine powder for powder metallurgy. Tin can be alloyed with almost all metals, and is used more with solder, tin bronze, babbitt, lead-tin bearing alloys and lead alloys. Many tin-containing specialty alloys, such as zirconium-based alloy, a nuclear fuel cladding material for nuclear industry; titanium based alloys for aviation, shipbuilding, nuclear, chemical, medical equipment and other sectors; between niobium tin intermetallic compound, as superconducting material; tin-silver amalgam, as a dental metal material. The important compounds of tin are organic compounds of tin dioxide, tin dichloride, tin tetrachloride and tin, which are used as ceramic enamel raw materials, mordants for printing and dyeing silk fabrics, heat stabilizers for plastics, and also as fungicides. And pesticides.
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