Experimental Investigation of Oxide Layer Formation Depending on Temperature Holding Time during Inductive Heating of Annealed 16MnCr5

Abstract

Fine blanking is a highly productive process of industrial mass production of high quality components in particular for the automotive industry. The manufacturing process faces a limit at elevated tensile strengths of the materials to be processed. Consequently, high-strength steels can currently only be fine blanked to a limited extent. This can be overcome by lowering the flow stress of high-strength steels by means of inductive heating. Heating a steel sheet which is not self-passivating creates an oxide layer on the sheet surface. An oxide layer can affect a subsequent fine blanking process by changing the material properties of the processed steel sheet. In order to avoid this, the process could be carried out under protective gas atmosphere. However, to reduce cost, it would be preferable to perform the process without a protective gas atmosphere. It is thus necessary to investigate the oxide layer formation of steel sheets depending on temperature holding time during inductive heating of steel sheets prior to fine blanking. This was done for soft-annealed 16MnCr5 steel sheets using material characterization methods as well as SEM and EDX. The dependence of the oxide layer formation on the temperature holding time could be determined. In addition, the resulting oxide layer was characterized with regard to its manifestation and physical properties.