Abstract
High strength car body components are used in the automotive industry to satisfy the demands of weight reduction and improved crash safety. To produce these products, voestalpine uses the press hardening process. This diploma thesis investigates to what extent crash safety can be improved by retained austenite, which is located in a matrix of martensite or annealed martensite and which transforms into martensite during deformation. For this purpose, three new alloys with different chemical compositionswere investigated, whereby different annealing treatments were considered for each alloy. In comparison with the currently used steel concept, the new alloys use higher contents of silicon and manganese allowing the stabilization of retained austenite. First, TTT-diagrams of all alloys were recorded in order to characterize the phase transformations. This was followed by metallographic examinations of the microstructures and the measurement of the volume contents of retained austenite. Various testing methods were applied for the characterization of the mechanical properties of the new alloys. As commonly applied, a special bending test was used for the evaluation of crash safety; hereby a critical bending angle, taken at maximum load, is taken for the assessment. Furthermore, interrupted bending tests have been performed to analyze the damage evolution during these tests. The results of these tests were compared to those of the currently used materials, in order to check the applicability of the three new alloying concepts.
Translated title of the contribution | Investigation of alternative alloying concepts for press hardening steels |
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Original language | German |
Qualification | Dipl.-Ing. |
Supervisors/Advisors |
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Award date | 28 Jun 2013 |
Publication status | Published - 2013 |
Bibliographical note
embargoed until 31-05-2018Keywords
- press hardening steel
- crash safety
- retained austenite
- annealing treatments
- TTT-diagrams
- microstructure
- critical bending angle