TITANIUM & TITANIUM ALLOYS

Metallic titanium was first isolated in impure form in 1887 and with higher purity in 1910. However, it was not until the 1950's that it began to come into use as a structural material. This was initially stimulated by aircraft applications. Although the aerospace industry still provides the major market, titanium and titanium alloys are finding increasingly widespread use in other industries due to their many desirable properties. Notable among these is their low densities, which fall between those of aluminum and iron and give very attractive strength to weight ratios. In addition, titanium and titanium alloys readily form stable protective surface layers which give them excellent corrosion resistance in many environments, including oxidizing acids and chlorides, and good elevated temperature properties up to about 440 degrees C (1022 degrees F) in some cases.

Titanium is abundant in the earth's crust and is extracted commercially from the ore minerals rutile (titanium dioxide) and ilmenite (iron-titanium oxide). The commercial extraction process involves treatment of the ore with chlorine gas to produce titanium tetrachloride, which is purified and reduced to a metallic titanium sponge by reaction with magnesium or sodium. The sponge, blended with alloying elements (and reclaimed scrap) as desired, is then vacuum melted. Several meltings may be necessary to achieve a homogeneous ingot which is ready for processing into useful shapes, typically by forging followed by rolling. For many applications the cost of titanium alloys can be justified on the basis of desirable properties.

TITANIUM PRODUCTION

Titanium is the fourth most abundant metallic element in the earth's crust. It occurs chiefly as an oxide ore. The commercially important forms are rutile (titanium dioxide) and ilmenite (titanium-iron oxide) the former being richest in titanium content.