Micro Warm Coining of Stainless Steel Sheets Using Electric Conductive Heating

Abstract

The motivation of this study is to investigate micro warm coining of metals with high strength (e.g. austenitic steels) in the field of fabricating micro functional surface structures. The current micro cold coining technology, which uses punches made out of steel, is limited to soft metals, such as Al and Cu. Conducting micro cold coining on steels, leads to high tool wear and bad form filling. The approach of this study is integrating electric conductive heating into a micro coining system to realize micro warm coining of stainless steel. This paper presents the experimental and numerical analysis of micro warm coining technology using the material stainless steel 1.4401. A coupled thermal-mechanical model in the commercial Finite-Element-code ABAQUS is used to help analyzing the micro warm coining process. The results are summarized as follows: (1) Open die micro warm coining has been realized. The form filling achieved was 56%, which was three times larger than the form filling of cold micro coining on the same material. (2) Both the experiments and simulations showed that faster processing, by increasing the punch velocity, resulted in a slightly improved form filling (5% from 5 mm/s to 100 mm/s). (3) Surface chilling hindered the filling of thin ribs.