Temperature supported hydroforming of stainless steels tubes

Due to their structure, tubes and closed profiles have a high potential for application in components that have to meet the highest demands in terms of lightweight construction, rigidity and manufacturability. They are therefore becoming increasingly important in relevant markets, especially in the automotive and aviation industries, in Europe and worldwide. An established process for the production of such profiles is the process of tube hydroforming (THF). A geometrically simple semi-finished product, e.g. a tube, is formed into the surrounding tool cavity by feeding it with an active medium and building up an internal pressure. It can be used to create geometrically complex, highly rigid components. The manufacture of these parts from steel materials represents a cost- and energy-efficient alternative to the established lightweight materials such as aluminum or fibre-plastic composites.In the project the hydroforming process for the processing of ferritic stainless steel X2CrTiNb18 (1.4509) was considered. Formed at room temperature, this material has a low formability. Many parts must therefore undergo several intermediate forming steps in series production, subsequent heat treatments and washing processes until the final part is obtained. Hot metal gas forming (HMGF) makes use of the material's increased formability at temperatures from 800 °C and above and the process chain can be significantly shortened. The project focus was on improving the manufacturability and quality of complex profile components with high functional integration made of the material 1.4509 by using the HMGF process. At the same time, the process was to be shortened and optimized by developing new tool technology with integrated heating technology and by defining the necessary process parameters.