Other types of ores not commercially acceptable are sphene and perovskite. Both contain TiO2 and calcium. The problem is that calcium is really difficult to remove, rendering both ores impractical economically. Sphene is even more difficult to work with as it has silicone on top of calcium. A titanium material is made from some compounds as well, including magnesium and chlorine.
Mining of the raw material is the first step. Usually sand that contains rutile or ilmenite ores is extracted from the beaches or hard rocks. Rutile, TiO2, is processed in its natural state while ilmenite, FeTiO3, undergoes a special process to remove iron (Fe). After the removal, FeTiO3 has no less than 85% titanium dioxide. Ilmenite and retile ores containing titanium dioxide are added to chlorine gas, carbon and chemical reactors (also fluidized bed reactors). The mixture is heated at about 900゜C.
This results to a more contaminated titanium tetrachloride (TiCl4). A carbon monoxide gas also results. All the unnecessary metal chloride impurities must be extracted to make TiCl4 purer. So there comes the purification step. The reacted metal is placed in big distillationtanks. Then it is heated to separate impurities from TiCI4 via fractional distillation and precipitation method. Impurities in this case entail metal chlorides like magnesium, silicon and iron among others.
After the purification, titanium manufacturer must produce the sponge. So the purified TiCI4, often in liquid form, is put into a vessel containing a stainless steel chemical reactor. Then magnesium is added and heat is turned on up to 1100゜C. To create a vacuum in the vessel, argon is pumped into it. This is done to eliminate potential contamination of TiCI4 liquid with nitrogen or oxygen. A reaction between magnesium and chlorine produces liquid magnesium chloride.
Because the melting point of Ti is higher than that of the reaction, pure and solid titanium is recovered in the end. This solid item is removed from the reactor via a boring method. Then it is treated in a mixture of water and hydrochloric acid. This causes removal of extra magnesium chloride and magnesium mineral. Eventually a spongy, metal that is both hard and porous is attained.
To change pure titanium metal sponge into an alloy, it is thrown into an electrode arc furnace. At this point the sponge is blended with the desired scrap metals and alloys. The mass is then compressed to form compacts that are soldered together to form a sponge electrode. This sponge is added to a vacuum arc furnace (VAF) to be melted into an ingot. This alloyed titanium ingot is melted one or two times to be economically viable. It is eventually removed from the VAF and taken through thorough quality assurance standards.
Stanford Advanced Materials
Stanford Advanced Materials