Extension of the limiting drawing ratio in tempered titanium sheet forming with simultaneous energy savings through resistance heating

• Applicants: Dr.-Ing. Sven Hübner; Professor Dr.-Ing. Günter Klawitter
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 573674130

For titanium alloys that are difficult to form at room temperature, higher forming temperatures should be used for deep drawing in order to improve the forming limits. In the case of corrosion and wear-resistant components, the formation of scale must be avoided, as subsequent removal is associated with a deterioration in component quality. Therefore, with regard to the surface, heating should only take place below the scale formation limit. This is approx. 650 °C when heating in a chamber furnace. Scale formation is time-dependent, therefore a shift of the scale limit by approx. 150 °C towards higher temperatures is to be expected with rapid heating. Rapid resistance heating is predicted to save 92 % of the energy, provided it could be used for titanium sheet forming. Virtualised models and model-based control are required for the proposed resistance heating principle in order to fully map the complex thermomechanical interactions. Working hypothesis: As scale formation depends on temperature and time, a higher temperature level can be achieved without scale through resistance heating in a matter of seconds compared to significantly slower furnace heating, which leads to higher achievable degrees of forming in the component. The scale formation history can be described and follows a different temperature-time regime during resistance heating. Resistance heating allows significant energy savings compared to the heating currently used in the chamber furnace and at the same time increases the scale-free formability. Thermodynamic modelling can be used to describe the extension of formability and the scale formation limit. The aim is to prove the working hypothesis with the development of a new process-adapted principle for resistance heating of sheet metal blanks and mould blanks in which no more cold strips remain on the sheet (electrode influence). In particular, the time- and temperature-dependent formation of scale during resistance heating within seconds is to be researched from a fundamental scientific point of view with regard to the formation of a tarnish layer - protective scale layer - lamellar scale, together with a description over time. With this knowledge, a component-relevant scale formation limit is to be defined in order to define the transition from protection to damage during resistance heating for the first time on the basis of transferable criteria. The aim is to be able to produce scale-free components with higher degrees of deformation at higher forming temperatures. This heating principle is intended to save energy and material (scale = material loss). The expansion of the forming capacity is to be scientifically described in a thermodynamically dominated model.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr.-Ing. Bernd-Arno Behrens