Automotive Design


Titanium: some light relief


4 New ways of working with titanium, making it easier to process, could see it making inroads into the automotive industry. Lou Reade reports.


4 De nouvelles manières de travailler avec le titane, le rendant plus simple à traiter, pourraient voir le jour dans le secteur automobile. Lou Reade témoigne.


4 Neue Arbeitsweisen mit Titan, die die Arbeitsabläufe vereinfachen, haben es in die Automobilbranche geschafft. Lou Reade berichtet.


T Fig. 1. Fraunhofer


researchers have devised a technique to lower the cost of titanium forming.


itanium has many advantages as an industrial material: as well as being 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. 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 forming process that is not economically viable for large-volume production. “This microstructural change can be


avoided at extremely high temperatures,” says Albert. The forming tool, which measures around


1.4 x 1.2m, is made from materials such as nickel-base alloys which remain stable above 800°C without oxidising. A special coating, just a few microns thick, prevents titanium from adhering to the tool, which can lead to component cracking and severe damage to the surface. Above 500°C, titanium reacts readily with


oxygen and nitrogen in the atmosphere. For this reason, shielding gases such as argon are used at very high temperatures to prevent oxidisation. Martin Weber, an expert in tribological


coatings at Fraunhofer IST, says: “After extensive testing with various materials, we developed the ideal coating for the special conditions encountered within the various temperature ranges.”


Oxygen is the enemy


At the same time, a collaborative team in the UK has devised a way to make a welded


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