Hydroforming at elevated temperatures

Hydroforming of tubes and blanks with fluid media at room temperature is state of the art for applications like car body structures or exhaust systems and also for special products outside the automotive industry. These parts are mostly made of the steel, mild steel, high strength steel, stainless steel and aluminium. New requirements of the global market demand lightweight designs especially for mobility. The reduction of weight can be achieved by using lightweight materials, materials with higher strengths (1000 MPa or higher), optimised structural design or a combination of those. In any case, advanced forming technologies are required to reach the necessary formability to form these materials in the demand shapes. To meet the new requirements, the forming temperature has been introduced as a variable process parameter. Lightweight materials need elevated temperatures to achieve the necessary formability. These, in turn require increasingly complex geometries. To use the potential of higher forming temperatures it is necessary to deal with temperature resistant forming medias. In the first step, a thermal oil was used up to 300°C, in the second step, gaseous medias, such as nitrogen, were chosen to reach forming temperatures up to 1.000 °C. During this research and development process several test parts as well as real prototypes were realized. New and increased forming limits were achieved and a lot of experienced was gained from the processes planning and simulation, to design the tool set up. Parts in aluminium, magnesium, titanium will be presented. A new development, the combination of media based forming and heat treatment, will be presented on forming of manganese-boron-steel. Like hot stamping of blanks extremely light and strong structures can be achieved to meet future needs.