Modified press‐hardening processes are very attractive for manufacturing safety‐relevant vehicle body parts from steels with martensitic–ferritic microstructures. In the process developed, the formation of the two‐phase microstructure and the hot sheet forming simultaneously occur subsequently to an intercritical annealing. By contrast, previously used process chains do not integrate setting of a multi‐phase microstructure within the forming step. In order to successfully combine the intercritical annealing with the actual forming, comprehensive knowledge of the microstructural evolution and the resulting mechanical properties is needed. Specifically, different heat‐treating routes are used to obtain different microstructures of ferritic–martensitic dual‐phase steels and partial martensitic steels. As a result of intercritical annealing in the temperature range of Ac1–Ac3, it is possible to vary the martensite volume fractions from 7 to 96 vol%. The data obtained can be employed for numerically describing the microstructural transformation and for designing the heat treatment process. It is demonstrated that this combined process allows for designing steels that feature properties that are similar to complex‐phase steels.

In recent years, high strength steels, particularly press‐hardening steel, have been more extensively employed for manufacturing safety‐relevant structural components in vehicle bodies. These applications require contrasting material properties such as extremely high strengths as well as high forming ductility. Owing to the purely martensitic microstructure, the residual ductility of the conventional press hardened steels is low. Quenching and partitioning heat treatments can fulfil the requirement of an increased residual ductility by stabilizing the retained austenite. Moreover, if the quenching and partitioning heat treatments are carried out after intercritical annealing treatment, then the steel's mechanical properties can be tailored by defining the volume fraction of ferrite in the microstructure. In order to determine the potential of an 1‐step quenching and partitioning heat treatment combined with intercritical annealing processes, elevated contents of retained austenite are produced in ferritic‐martensitic microstructures using the low‐alloyed 22MnB5 steel grade. In addition to a tempered martensitic microstructure, secondary martensite, and a low fraction of retained austenite, the microstructure consists of remaining fractions of ferrite; thus, providing an additional increase in ductility. For this optimized microstructure, a yield stress of 513 MPa and a tensile strength of 1045 MPa are measured with a total elongation of 10.8%.

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A device and the basic technology has been developed for tensile testing pipe sections samples (tensile testing PSS) for quantitative estimating ultimate tensile and yield stresses in ring samples (PSS samples) cut from pipes. This tensile testing device provides the opportunity for compensating frictional forces during the tensile test, and using exchangeable bearings, the device can be adapted to a wide assortment of pipes. Research has been carried out regarding the shape and size of a stress concentrator introduced into the sample. Relationships have been derived between the shape of the tensile loading curves and the characteristic forces for different types of stress concentrators. It is proposed to use PSS with stress concentrators to prevent plastic deformation in one of the supporting sections (this also allows to correlate the applied forces to one section). The concentrator should be introduced into the tube wall of the sample as a drilled hole. This method is comparatively simple with respect to established testing methods.

In the last decade, press-hardening of manganese-boron steels for the manufacturing of safety-relevant components has become a well-established industrial process. Thereby, very high strengths are achieved with pure martensitic microstructures. However, in certain areas of the car body structure more ductile components are necessary to absorb crash energy. For tailoring the material properties, two-or multiphase microstructures can be induced by rolling and heat treatment processes. The press-hardening steel 22MnB5 which is employed in the present study, is used to manufacture three different ferritic-martensitic microstructures. These different materials are characterized by classical mechanical models, based on experimental results. For the mechanical description of the initial yield stress depending on the stress state of different multiphase steels, the Hill model is calibrated. The elastic limit and the kinematic hardening of three various heat treatment conditions are determined using conventional tensile tests and the Galimel test, respectively. Therefore, the applied mathematical relations are derived and adapted for the performed investigations. The relationship between the load conditions and the proper application of the equations are explained. The resulting microstructures are characterized and the ramifications with respect to their energy absorption capability are discussed.

The objective of the current investigation is a cost analysis of spray cooling based on the assessment of a machine-hour schedule. Here, a gear toothed component is used as an example which is induction hardened by means of the simultaneous dual frequency method and compared with conventional polymer quenching. By using hardness measurements and light-microscope examinations, it is demonstrated that comparable results are obtained for the induction hardening by employing spray cooling and those by polymer quenching. By investigating the influence of the spray's parameters on the hardness results, it was possible to draw inferences regarding the ratios of water to air pressures which lead to the desired hardness profiles. Estimating the costs of employing the two quenching methods have shown that the spray cooling is the more cost-effective of the two methods.

The measurement of Barkhausen noise is one of the non-destructive testing methods which allows the use within the production line and within the cycle time at a high production volume. The aim of the present study was to answer the question, whether it is possible to extract the informations that the Barkhausen noise includes, concerning work-piece conditions, from the signal characteristic and more important assigning these findings. Therefore, soft machined and heat treated shaft components made of the ferromagnetic material Cf53 (1.1213) were analyzed to find characteristics in the Signal that allow to separate clearly an increase in temperature of the tested area from a change in the microstructure. For this purpose the shafts were analyzed at higher temperatures (up to 80 °C) and after an additional annealing process (to change the microstructure specifically). Both investigated situations (higher temperature and modified microstructure) showed different characteristic in the Barkhausen signal, thus an assigning is possible. Metallographic investigation and hardness measurements has been carried out to support the results.