Tungsten, a metal elements. Atomic number 74, atomic weight of 183.84. steel gray or silver white, high hardness, high melting point, room temperature, air erosion; mainly for the purpose of manufacturing filament and high-speed cutting of alloy steel, super hard mold, also used in optical instruments, chemical equipment. China tungsten reserves of the world is the biggest. Tungsten is a metallic element. The tungsten chemical element symbol W, atomic number 74, the relative atomic mass of 183.85 atomic radius 137 picometers, density of 19.35 grams per cubic centimeter, which belongs to the periodic table of the elements in the sixth period (period second) of the VIB group. The main tungsten in nature was six divalent cations, their ion radius is 0.68 * 10-10m. because the W6+ ion radius is small, high price, polarization ability, easy to form anions, tungsten mainly anions form [WO4]2-, Mn2+ and Fe2+ in solution, and in combination with Ca2+ and cationic form of wolframite scheelite or precipitation. After smelting tungsten is silver white shiny metal, high melting point, high hardness, low vapor pressure, the evaporation rate is smaller, the chemical properties are relatively stable. Scope of use At present the world mining tungsten ore, about 50% for the smelting of high-quality steel, about 35% for the production of hard steel, tungsten wire for about 10%, about 5% for other purposes. Tungsten can manufacture guns, rocket nozzle, cutting blades, drill bits, ultra hard mold, wire drawing dies, tungsten use is very extensive, involving mining, metallurgy, machinery, construction, transportation, electronics, chemical industry, light industry, textile, aerospace, military, science and technology, various industrial fields. Contact material and high gravity alloy Made by powder metallurgy of tungsten copper alloy (10% - 40% copper) and tungsten silver alloy, good conductivity of both copper and silver, wear resistance and thermal conductivity of tungsten. Therefore, it has become the manufacturing knife switch, circuit breaker, contactor material components such as spot welding electrode very effective 90% - 95%. Composition of tungsten 1% - 6% nickel, high proportion alloy 1% - 4% copper, iron and copper (5%) alloy for gyroscope rotor, manufacturing aircraft, balance weight control, radioactive isotopes and radiation shield material basket.