Automotive Design
New ways of working with
titanium, making it easier to process, could see it making inroads into the automotive industry. Lou Reade reports.
Titanium: some light relief T
itanium offers many advantages as an industrial material: as well as being some 40 per cent lighter than
steel, it is available in abundance, highly corrosion- and temperature- resistant and very malleable.
However, it is difficult to process by metal forming techniques such as deep drawing or hydroforming. It is also very difficult to weld. When processed at high temperature, it has a tendency to react with oxygen and nitrogen in the atmosphere. For this reason, shielding gases such as argon are used to prevent oxidisation. This pushes processing costs sky high.
But several European research teams are working around these disadvantages. At the Fraunhofer Institute in Germany, for example, researchers have developed a cost-effective way of processing titanium that could expand its use in the automotive industry.
In this sector, titanium has only been used for high-end vehicles and motor sport applications, because it is very expensive to process. The new technique could lead to titanium being used in
parts like manifolds, exhaust pipes, catalytic converters and mufflers – which are usually manufactured from high-alloy stainless steel.
“Titanium tends to adhere to the forming tools,” says André Albert, group leader for media- based forming technologies at the Fraunhofer Institute for Machine Tools and Forming Technology (IWU) in Chemnitz, Germany. This, he says, leads to major damage which can cause component failure. The effect is amplified by the fact that titanium must be formed at temperatures of up to 800°C.
In collaboration with colleagues at the Fraunhofer Institute for Surface Engineering and Thin Films (IST) in Braunschweig, Albert has developed a way to hydroform titanium car exhaust systems at high temperatures. It enables forming to be undertaken in a single process stage.
Fig. 1. Researchers have devised a technique to lower the cost of titanium forming.
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Previously, a minimum of three stages was necessary, using intermediate heat treatments which required processing in different locations. The researchers have now developed a process – and a custom tool – that can withstand temperatures above 800°C. This is because forming titanium at room temperature leads to severe cold work hardening of the processed pipe. To prevent cracking, the metal requires frequent treatment by means of recrystallisation – a complex, multi-stage
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