Titanium Alloys :

Titanium ASTM Specifications
 

Introduction to Titanium
Titanium Specifications Characteristics Markets Corrosion Resistance Fabrication and Applications are listed in this section.
It was almost 200 years ago that titanium was first isolated and named after the powerful mythological first sons of the Earth - the Titans. The industry as we know it today is over 40 years old. Titanium is most commonly associated with jet engines and airframes, but the most recent media attention has been given to fittings for prosthetic devices and the artificial heart.
Once judged to be expensive, titanium, in life-cycle costing, is now more often seen to be economical. The key to its cost-effective use is to utilize its unique properties and characteristics in the design rather than to substitute titanium for another metal.
 

Titanium is the world's fourth most abundant structural metal. It is found in North America, South America, Europe, Africa, U.S.S.R, China and Australia in the forms of ilmenite, rutile and other ores. The most widely used means of winning the metal from the ore is the Kroll process which uses magnesium as a reducing agent. Sodium is also used as a reducing agent by some producers.
 

To produce titanium, the basic ore, usually rutile (TiO2) is converted to sponge in two distinct steps First, TiO2 is mixed with coke or tar and charged in a chlorinator. Heat is applied and chlorine gas is passed through the charge. The titanium ore reacts with the chlorine to form TiCI4, titanium tetrachloride, and the oxygen is removed as CO and CO2. The resultant crude TiCI4 produced is a colorless liquid and is purified by continuous fractional distillation. It is then reacted with either magnesium or sodium under an inert atmosphere. This results in metallic titanium sponge, and either magnesium or sodium chloride which is reprocessed and recycled.
 

Melting is the second step. Titanium is converted from sponge to ingot by first blending crushed sponge with the desired alloying elements to insure uniformity of composition, and then pressing into briquettes which are welded together to form an electrode. The electrode is melted in a consumable electrode vacuum arc furnace where an arc is struck between the electrode and a layer of titanium in a water-cooled copper crucible. The molten titanium on the outer surface solidifies on contact with the cold wall, forming a shell or skull to contain the molten pool. The ingot is not poured, but solidifies under vacuum in the melting furnace. To insure homogeneity of the final ingot, a second or sometimes a third melting operation is applied.