2013 Volume 54 Issue 626 Pages 272-276
Hole expansion test using a flat-bottomed cylindrical punch was carried out to clarify the effects of the difference in microstructure between two types of complex-phase high-strength hot-rolled steel sheet on stretch flangeability, in which ferrite-pearlite steel and ferrite-bainite steel of 590 MPa tensile strength were used. The results showed that the hole expansion ratio λ in the case of the hole of a reamer edge depended on fracture limit strain, which changed with the fracture behavior. Moreover, by investigating the correlation between the quality of material around the hole and λ of the sheared hole, it was clarified that the λ of ferrite-bainite steel is affected by work hardening, and that the λ of ferrite-pearlite steel is affected by microvoids generated in piercing.
