Titanium Extraction and Refining
Titanium is a comparatively common element, and it is the fourth most abundant structural metal on earth (just behind aluminum, iron, and magnesium). Workable deposits are found all over the planet, and yet it remains more expensive than any of those other metals. Unlike gold, the price of titanium isn’t based on its rarity, but on the difficulty in extracting, refining, and processing the raw materials.
Extracting the Titanium
Most titanium mining is done by open pit, meaning that the soil is taken from the ground and sent to factories where the ore can be removed. This process is usually done with a suction bucket wheel on a floating dredge. Mineral-rich sand is sent through its screens, called trammels, which starts filtering out the unwanted or unnecessary elements. The separation is usually gravity powered, and the waste can be removed with a wet spiral concentrator.
At this point, the separated material can be sent through some electrostatic, magnetic, and other gravity-fed equipment to further refine the materials into something useful.
Processing the Material.
So far, this process is not too far removed from other mining and extraction operations. However, this is where things get a little more difficult. Titanium processing is done with something called the Kroll Process which, even when it was first introduced in the 1930s, has never been the most efficient way to go. However, in all that time, no one has been able to develop anything any better.
First, titanium oxide ore is combined with chlorine to make titanium chloride. This step is something most other metals can skip, because they don’t have to turn the oxide into a chloride before it can be processed. It’s an extra step that requires more time and money.
Next, the titanium chloride is reduced using either magnesium or sodium as a reducing agent to form titanium. This part of the process has to take place inside a steel reactor that is welded shut and heated to 1200C. This has to be done because titanium is very reactive and any oxygen in the mix could result in a very brittle metal. (It is usually processed in a controlled environment of argon instead of oxygen.)
Unfortunately, this means that titanium can only be processed in batches, unlike iron and other metals that have a continuous flow in a blast furnace. For titanium, the materials must be added and sealed into the reactor for a couple days before it can be opened up and the titanium removed. In total, extraction and processing can take up to 17 days. The largest reactors can produce about a ton of titanium a day, which isn’t bad, but the big blast furnaces for iron can produce up to 10,000 tons a day.
This extended process is why the cost of titanium is higher than other metals, but research continues to find new, more efficient options.
Fabricating Usable Products
Titanium has an atomic diameter similar to a lot of other common metals (aluminum, iron, etc.), which means it can be alloyed with them to create desirable properties. This can create different capacities for mechanical and corrosion resistance.