**6. Conclusions**

The results of simulation and press hardening experiments show that it is possible to produce complex steel sheet components with high strength and ductility by press hardening in combination with a controlled quenching and partitioning treatment. By quenching to a temperature below the *Ms* temperature of the steel, heating to a temperature, e.g., 30 ◦C above *Ms* and holding there, the phase transformation time is shortened, in comparison with a traditional austempering treatment. Consequently, the total processing time is shortened, benefiting productivity. Even though the steel with a carbon content of 0.15 wt % gave yield and tensile strength values lower than those of conventional press hardened boron steel, the steel with the carbon content of 0.26 wt % resulted in a yield strength comparable with that of the boron steel, although with a lower tensile strength. In addition, the elongation to fracture after press hardening in combination with quenching and partitioning is significantly higher than that of conventional press hardened 22MnB5 boron steel.

The microstructure achieved after pressing and QP treatment contains a very fine multiphase structure comprising lath-like ferrite, retained austenite and tempered martensite, which contribute to the good tensile properties achieved for the materials. In comparison with conventional martensitic microstructure achieved by press hardening of boron steels, the structure achieved by QP treatment in combination with pressing enabled the formation of a very refined structure containing a large amount of ferrite laths and interlath retained austenite, which rendered relatively higher ductility besides high strength in the produced components.

**Author Contributions:** The author contributions have been following; Conceptualization, E.P.V.; Methodology, E.P.V. and K.E.; Investigation, E.P.V., A.G.Ö., K.E., F.G.C., and S.A.; Data curation, F.G.C.; Writing—original draft preparation, E.P.V., M.C.S., and J.C.I.; Writing—review and editing, E.P.V., M.C.S., and L.P.K.; Visualization, A.G.Ö., K.E., and E.P.V.; Gleeble test planning and supervision, L.P.K.; Gleeble tests and data analysis, interpretation of hardness data in respect of quenching and partitioning process, M.C.S.; Alloy design based on thermodynamic and kinetics calculations, and microstructure characterization, F.G.C.

**Funding:** The European Research Fund for Coal and Steel, contract RFSR-CT-2008-00021, has funded this work.

**Acknowledgments:** The support of the European Research Fund for Coal and Steel for funding the contract RFSR-CT-2008-00021 is gratefully acknowledged by the authors. Michelle Nicolaus and Farnoosh Forouzan are acknowledged for their assistance in the work.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
