Punch Edge Topological Design for Reduction of Work Hardening Damage in Shearing of Non-Oriented Electrical Steel Sheets

A new shearing tool is necessary to reduce the iron loss of motor cores by minimizing the work hardening damage on the sheared non-oriented electrical steel sheets. The punch edge topology and the clearance between the punch and the die were controlled to investigate their influence on the sheared surface condition and the work hardening damage of steel sheets. A non-oriented electrical steel sheet with the thickness of 500 µm was used and sheared at the speed of 5 mm/s. After that, the sheared surface was investigated. In particular, hardness mapping was utilized to quantitatively analyze the work-hardened area of the sheared steel sheets and the dissipation of the plastic work. Among the four punch edge topological configurations explored, the nano-grooved punch employed straight along the shearing direction reduced the damage dealt to the sheared steel sheets and the plastic dissipation work to one-third compared to conventional punches.