The increasing demand for high strength steels regarding light weight construction design for the body in white is enforcing the automotive industry to onset more and more innovative forming technologies due to the reduced formability of such high strength steel grades. The hot stamping of boron manganese steels is hereby one of the main forming processes to be named. Besides the commonly used forming strategy where a homogeneous distribution of the material parameters is achieved, the partial press hardening is an innovative technology to be able to manufacture parts with a locally different strength and ductility profile. The thermal properties needed for this kind of process strategy had been determined using a heatable quenching tool developed at the Chair of Manufacturing Technology and are further discussed in this paper.

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The topic of the paper is the identification of the heat transfer coefficient (HTC) in hot stamping of boron steel sheets under conditions very close to the industrial ones. Two approaches followed by one lab in Germany and one lab in Italy are presented for HTC identification, showing the two experimental apparatuses that were set-up to conduct the tests, the procedures developed and applied to identify the HTC. The obtained results are compared in terms of dependence of HTC from the applied contact pressure, the similarities and the differences of the two approaches are outlined and commented.

In the automotive industry hot stamping of boron manganese steels represents one of the major technologies to manufacture crash relevant structures within body in white considering aspects of light weight construction. Hot stamping can be described as a non-isothermal hot sheet metal forming process. Temperature control in the forming process plays an important role. The process is quite complex as temperature dependent material and process properties such as flow curves, heat transfer and friction coefficients have to be considered. To improve the knowledge about the process the influence of different process parameters and tool coatings on the heat transfer between tool and specimen is investigated. Additionally, the impact of monolayer, multilayer and superlattice coatings on the wear behavior and on friction is characterized. Furthermore, the effect of different austenitization parameter settings is analyzed with regard to the tribological conditions and resulting adhesive wear.

The paper presents results obtained at two labs, on in Germany and one in Italy, in terms of friction coefficient as function of hot stamping process parameters. Even if the testing procedures and analysis tools to evaluate tribological conditions are different for the two labs, both the approaches show a similar trend as regards the friction coefficient dependence from the process parameters.