Titanium is a chemical element, chemical symbol Ti, atomic number 22, in the periodic table of chemical elements in the fourth cycle, Group IVB. Is a silver-white transition metal, which is characterized by light weight, high strength, with metallic luster, moisture-resistant chlorine corrosion. But titanium can not be used in dry chlorine, even if the temperature below 0 ℃ dry chlorine, there will be a violent chemical reaction, the formation of titanium tetrachloride, and then decomposition of titanium dioxide, or even combustion. Only when the moisture content of chlorine gas is higher than 0.5%, titanium in which to maintain a reliable stability. 
Titanium  is considered to be a rare metal, due to its dispersion in nature and difficult to extract. But its relatively rich, in all the elements in the tenth place. Titanium ore mainly ilmenite and rutile, widely distributed in the crust and lithosphere. Titanium is also present in almost all creatures, rocks, water bodies and soil. Extraction of titanium from the main ore requires the use of the Crow method or the Hunt method. The most common compound of titanium is titanium dioxide, which can be used to make white pigments. Other compounds include titanium tetrachloride (TiCl4) (as a catalyst and for the manufacture of smoke screens for aerial cover) and titanium trichloride (TiCl3) (for the production of catalyzed polypropylene)
Content distribution: the surface of the earth 10 km thick layer, containing titanium up to six thousandths, more than copper 61 times in the crust in the content ranked tenth (crust element rankings: oxygen, silicon, aluminum, iron, calcium , Sodium, potassium, magnesium, hydrogen, titanium), casually grabbed a soil from the ground, which contains thousands of tons of titanium, the world's reserves of more than 10 million tons of titanium is not rare.
The earth has hundreds of millions of tons of gravel, titanium and zirconium two kinds of gravel heavy minerals, mixed in the gravel, after thousands of years of sea water day and night constantly panning, the heavier ilmenite And zircon sand ore together, in the long coast, forming a piece of titanium and zirconite layer. This layer of mineral is a black sand, usually a few centimeters to several centimeters thick. Titanium is not ferromagnetic, with titanium construction of nuclear submarines do not have to worry about the magnetic mine attack
1940 Luxembourg scientists W.J.Kroll with magnesium to reduce the TiCl4 made of pure titanium. Since then, the magnesium reduction method (also known as the Khorger method) and the sodium reduction method (also known as the Hunt method) has become an industrial method for producing sponge titanium. The United States in 1948 with magnesium reduction system made 2 tons of titanium sponge, from the beginning of the industrial production of titanium.
In 1947, people began to smelting titanium in the factory. That year, the output is only 2 tons. 1955 production surge to 20,000 tons. In 1972, the annual output reached 200,000 tons. The yield strength of titanium is higher than that of steel, and its weight is almost half that of the same volume of steel. Although titanium is slightly heavier than aluminum, its yield strength is twice as high as that of aluminum. Titanium than the strength of aluminum and steel, than the modulus and aluminum, steel is very close. In the universe rockets and missiles, a large number of titanium instead of steel. According to statistics, the world's annual use of titanium for navigation, has reached more than 1,000 tons. Very fine titanium powder, or rockets good fuel, so titanium known as the universe of metal, space metal.
Titanium at high temperatures and easy to react with the air, but the melting point of up to 1668 ℃. At room temperature, titanium is not afraid of aqua regia and dilute nitric acid corrosion, but intolerance of more than 5% concentration of sulfuric acid and 7% hydrochloric acid corrosion. Titanium is not afraid of the temperature of the sea, it was a piece of titanium sink to the bottom of the sea, five years later take a look, above the sticky many small animals and seabed plants, but it is not rusty, still shining.
People began to use titanium to create submarines - titanium submarines. Because titanium is very strong, can withstand high pressure, this submarine can be deep in the deep sea of 4500 meters.