Editing Titanium (section)

====Kroll process====
[[File:Sample of Titanium tetrachloride 01.jpg|thumb|right|Sample of Titanium tetrachloride]]
The processing of titanium metal occurs in four major steps: reduction of titanium ore into "sponge", a porous form; melting of sponge, or sponge plus a master alloy to form an ingot; primary fabrication, where an ingot is converted into general mill products such as [[bar stock|billet]], bar, [[plate (metal)|plate]], [[sheet metal|sheet]], strip, and [[tube (fluid conveyance)|tube]]; and secondary fabrication of finished shapes from mill products.<ref>{{harvnb|Donachie|1988|loc=Ch. 4}}</ref>

Because it cannot be readily produced by reduction of titanium dioxide,<ref name=Stwertka1998/> titanium metal is obtained by reduction of [[titanium tetrachloride]] (TiCl<sub>4</sub>) with magnesium metal in the Kroll process. The complexity of this batch production in the Kroll process explains the relatively high market value of titanium,<ref name=Barksdale1968p733>{{harvnb|Barksdale|1968|p=733}}</ref> despite the Kroll process being less expensive than the Hunter process.<ref name=Roza2008p9/> To produce the TiCl<sub>4</sub> required by the Kroll process, the dioxide is subjected to [[carbothermic reduction]] in the presence of [[chlorine]]. In this process, the chlorine gas is passed over a red-hot mixture of rutile or ilmenite in the presence of carbon.
After extensive purification by [[fractional distillation]], the TiCl<sub>4</sub> is reduced with {{convert|800|C}} molten magnesium in an [[argon]] atmosphere.<ref name=TICE6th/>
:<chem>2FeTiO3 + 7Cl2 + 6C ->[900^oC] 2FeCl3 + 2TiCl4 + 6CO</chem>
:<chem>TiCl4 + 2Mg ->[1100^oC] Ti + 2MgCl2</chem>