Titanium, the metal of the future, is appreciated for its unique properties. In recent years, it has found use in numerous applications, ranging from surgical implants to airplane wings. This is a lightweight metal, with excellent corrosion resistance and an amazing strength-to-weight ratio. In this article we will focus on the titanium sheet supply route.
Few people know that titanium is one of the most abundant metals on t he planet; however, it is seldom found in pure form. It must be extracted from minerals, a process which is both expensive and difficult. Titanium goes a long way from raw material to part of finished product. Let’s find out more information on the journey of titanium, one that is impressive to say the least.
Titanium as raw material
When you look at a titanium tube, it almost seems impossible to imagine where it all started. Did you know that titanium is extracted from other minerals, such as ilmenite, leucoxene, rutile or anatase? Each of these ores is found naturally on the planet, being used for the production of titanium.
The percentage of titanium dioxide differs from one mineral to the other. Ilmenite, for example, has 85% titanium dioxide, while leucoxene contains 90% of the same metal. Rutile contains the highest percentage, while anatase has the metal in crystalline form.
Where are these ores found? Well, you might not know it, but the beach and sand deposits in general are great sources. The same goes for hard rock deposits, which are commonly used to extract titanium dioxide (along with the other minerals). In producing titanium, one will make use of other compounds, such as magnesium, chlorine gas and carbon.
How is titanium produced?
The production process of titanium includes a number of stages. First, titanium is extracted from the mineral and purified. Then, it is transformed into a sponge, which will be further used for the alloy creation.
The only one that can be used in its natural form is rutile, which has the highest percentage of titanium dioxide. With ilmenite, for example, one must process the material first and remove the iron. This process is achieved with the help of a reactor and additional materials, such as chlorine gas and carbon.
In the reactor, ilmenite is heated up to 900 degrees Celsius, until a chemical reaction occurs. This will cause an impure form of titanium to result, along with carbon monoxide. In the next stage (purification), these impurities will be removed.
Note: it is important to know that the resulted impurities are caused by the fact that pure titanium dioxide was not used in the beginning. Thus, they have to be removed.
The resulting impure metal will now be placed in a distillation tank and heated. This will allow the impurities to be separated, through two difference processes. The first process is fractional distillation, which refers to the separation of a mixture into its various parts. The second is precipitation, which will allow the easier removal of existent metal chlorides (e.g.: magnesium, iron, vanadium, etc.).
In the previous stage, the titanium tetrachloride was purified, reaching a liquid phase. The next step involves the transfer of this liquid to another reactor, where magnesium will be added. The reactor will be heated up to 1.100 degrees Celsius.
In order to remove the air in the reactor and prevent oxygen/nitrogen contamination, argon will be added (through pumping). A chemical reaction will occur between magnesium and chlorine, leading to the formation of magnesium chloride.
At the same time, the titanium will reach a solid state, given the fact that its melting point is higher than the one of the above-mentioned reaction. The removal of the solid titanium is achieved through boring.
Then, the titanium is treated with hydrochloric acid and water. This treatment has the purpose of removing any remaining impurities, such as magnesium and magnesium chloride. What is left is a porous metal, which is also known as a sponge.
The titanium sponge will now be transformed into an alloy, which can be further used for a wide range of products. The transformation will take place in a furnace, where the sponge will be mixed with alloys (additions, scrap metal). For the next step, the mixture will be pressed and welded, leading to the formation of what is known as the sponge electrode.
The sponge electrode will be placed in another furnace to be melted, which leads to the formation of the ingot. Once again, argon will be used to remove the air in the furnace (as an alternative vacuum can be used). The main purpose of this step is to prevent contamination. The ingot might be melted again, in order to gain a more acceptable form (commercial).
As a final step, the ingot will be taken out of the furnace and analyzed in detail (so as to make sure there are no defects). It will then be shipped to a manufacturer, who will use it for the making of various products including titanium sheet.
For what kind of products is titanium sheet used?
These are some of the finished products which contain titanium/titanium alloys:
- Surgical implants – joint replacement (hip); dental implants
- Jewelry – recommended to those with allergies; can be alloyed with gold
- Automobile & motorcycle parts – exhausts, valves, etc.
- Sporting goods – golf clubs, bicycle frames, etc.
- Firearm manufacture – pistol frames, revolver cylinders, etc.
- Industrial – welded titanium pipe (chemical, petrochemical)
- Aircraft and spacecraft components
- Marine – heat exchangers (desalination plants)
- Pigments – paint with titanium dioxide.
What is the future of titanium production?
In the future, the ingot production will be improved and new alloys will be developed. With new extraction and processing methods, we can expect for the production costs to go down. We will also see titanium being used in new industries.
As the demand for titanium increases, it is clear that larger production facilities will need to be developed (so as to produce bigger ingots in a shorter period of time). It is also a challenge to identify optimal compositions of titanium alloys, so that the best results are obtained.
New methods are currently explored, so as to extract titanium directly from titanium dioxide. This would reduce overall production costs, increasing the availability of titanium and titanium alloys.