Markus Pfestorf

The use of dry film lubricants in aluminum sheet metal forming

Abstract In the process of aluminum sheet metal forming, the tribological system is mainly influenced by the surface texture, the surface of the draw die and process parameters such as deformation rate and lubrication. Because of their high deep drawing performance today’s production process is mainly based on liquid lubricants. Due to the very sensitive surface of aluminum blanks dry film lubricants were developed in order to protect the blank surface during transportation and handling. Now dry film lubricants show advantages over conventional oil lubricants because of their higher deep drawing performance, especially on complex shaped body panels. Beyond that a cleaner process within the press shop can be established. In this paper the effect of dry film lubricants on the deep drawing process of aluminum alloys is shown. This is proven by fundamental experiments on the tribological properties in a stretch forming test and drawing investigations on complex shaped automotive body panels. The characterization of the blank surface is based on 3D surface parameters which are more appropriate for the classification of tribological properties of a surface texture than conventional 2D parameters. To show the great step forward in formability, some series applications in the press shop are presented.

Manufacturing of High Strength Steel and Aluminum for a Mixed Material Body in White

Sophisticated materials like high strength steel or even multi phase steel as well as aluminum require more efforts within the manufacturing process than conventional steel sheets as they have been used in the body in white recently. The manufacturing process itself as well as engineering of the parts, material of the forming tools as well as cold and warm joining technologies must be regarded separately. For forming tools coated steel inserts or sometimes even cooling is essential in terms of high-volume car series production. In mixed material solutions using steel in combination with aluminum, the common used resistance spot welding process does not work any more. To maintain high process stability of cold joining technologies combined with adhesive bonding a new process must have been developed. Other items for weight and cost savings are tailored rolled blanks or sophisticated joining technologies. Regarding the manufacturing costs, a cost effective combination of the mentioned high-sophisticated alloys with conventional material should be achieved. Developing a design concept due to crash, stiffness and driving performance, basic requirements have to be considered. This aims to check the high potential of cost intensive materials wherever high functional benefit is necessary under commercial aspects.

Crash Behaviour of Various Modern Steels Exposed to High Deformation Rates

The increasing call for significant safety improvements of new cars requires, among other important relevant aspects, the application of high strength materials for the body in white. Quenchable manganese boron alloyed steels like 22MnB5 offer superior strength values, complex shapes and enhanced accuracy. For the evaluation of the crash appropriateness specimens in different annealed states are deformed in a so called drop test bench and hereupon judged in terms of absorbed energy, maximum deformation and other aspects like wrinkling behaviour. Microscopic analysis complements the evaluation of crash-appropriateness.