Influence of Cutting Process on the Flanging Formability of the Cut Edge for DP980 Steel

Abstract

Flanging is a key process in the forming of automobile parts and is influenced by the cutting process before it. In this paper, a set of self-designed tools is adopted. The flanging height and flanging radius are specified as the indexes to investigate the influence of the cutting process on the flanging formability of DP980 steel. Microstructure, microhardness, and tensile properties are tested to evaluate the formability of cut edges. The results show that the flanging formability is positively correlated with an increase in flanging height and a decrease in flanging radius. The flanging formability of six cut edges can be ranked as: LC-L > LC-H > WEDM-HS > WEDM-LS > CNC milling > WJC. In the LC process, acicular martensite is formed and the microhardness of the cut edge significantly increases, with a heat-affected zone of about 150 μm. More and larger microvoids are found on the edge of WEDM-LS than WEDM-HS, which reduces the formability to a certain extent. Plastic deformation of the edges is the reason for the decrease in the formability of CNC milling. For WJC, the formation of irregular edge damage and the generation of burrs are the main reasons for the unstable performance. This research is helpful in guiding the selection of the cutting process, and it may contribute to a high part formability for DP980 steel.

Keywords

• flanging formability
• cutting process
• cut edge damage
• microstructural observation
• microhardness