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:: Time for titanium processing
By Whitney MacDonald
Technology with the potential to halve titanium production costs and streamline processing could create an opportunity for Australia to finally manufacture the titanium it mines.
Australia has some of the most significant resources of titanium ore in the world, yet due to costly and complex processing methods, it lacks an associated titanium metal production industry.
However, cutting-edge technology developed by the Light Metals Flagship - an initiative combining the efforts of scientists from CSIRO and industrial research partners - could provide the capacity for local titanium production.
Titanium metal is extraordinarily strong and exceptionally lightweight - as strong as steel with only 60 per cent of the weight - and is bio-inert and resistant to corrosion. However, expensive and complex processing costs are only tolerated by the aerospace and biochemical industries, where the advantages of using titanium outweigh the expense.
Other industries would greatly benefit from titaniumís characteristics, but mostly fall just short of balancing the cost-benefit equation.
TiROTM, the new titanium processing technique developed by flagship researchers, is based on some of the same principles as the Kroll process - the traditional method for producing titanium metal - but is continuous and eliminates many of the middle steps, reducing production costs.
Like the Kroll process, TiRO works by reducing titanium tetrachloride with magnesium to produce titanium metal. However, unlike the Kroll process, TiRO occurs within a temperature window that makes it appropriate to use fluidised bed technology. It exploits the principle that when suspended in a gas, solid particles behave like a fluid and react more rapidly. The result is a titanium powder, produced from a much smaller reactor in a fraction of the time. Minimal waste is produced during the process.
Grant Wellwood, a senior process engineer leading the TiRO project, says the Kroll process generates a lot of waste and is also very expensive.
"The current processes associated with titanium metal are very inefficient. Compounding the metal production inefficiencies are those associated with downstream manufacturing."
For example, he says, it can take 10 kilograms of metal to produce one kilogram of manufactured product. "Although the waste is usually recycled, the rework cost is significant. In aerospace the ratio is even higher, with 'buy-to-fly' ratios of 15:1 common."
The Kroll process produces a 'titanium sponge', a coral-like substance that is an intermediate to the end product. This 'sponge' must be subjected to extremely high temperatures to melt it into a form that can then be shaped for various downstream applications.
"A more efficient approach for many non-aerospace applications is 'near net-shape' manufacture based on powder metallurgy," says Dr Wellwood.
"However on a per-kilogram basis, the powders needed for this approach are currently more expensive than the sponge and even the finished products.
"So while titanium is a candidate for relatively inexpensive and well-established powder metallurgy techniques, the high cost of first producing the titanium in a powder form from the sponge route makes it unviable."
By directly producing titanium metal in the form of a powder, the TiRO process opens the door to using titanium rather than stainless steel, for more mainstream industries.
Titanium offers a particular advantage to the automotive industry: incorporating titanium into cars would mean a significant reduction in weight, translating to better fuel efficiency and environmental benefits.
The cookware industry is another area that could expect to reap the benefits from low-cost titanium production. With health concerns over certain types of cookware, manufacturers are looking for a material that offers the health-promoting trait of a non-stick surface without the associated complications. A reduction of about A$3 per kilogram in the cost of titanium metal could double the market for non-aerospace applications.
The flagship team is establishing a pilot plant that will operate at two kilograms an hour and build on the current proof-of-concept stage.
In conjunction with the International Titanium Association, the team recently held a 'Fundamentals of Titanium' workshop in Melbourne , Victoria , to promote the application of titanium.
Dr Wellwood says the outcomes were very positive, with a lot of government interest.
"Everyone was very enthusiastic and supportive of the flagship titanium initiative; recognising that having a low-cost metal process is the key to setting up an industry in Australia ."
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