Influence of Micro Crack to Hole expansion behavior of High Strength Steel Sheet

Abstract

The hole flange ability can be evaluated by limiting hole expansion ratio from hole expansion test. High strength steel grade 590 and 780 with 1.2 mm of thickness were used in this research. This results showed that the hole cut by laser and pierced by piercing punch which cause changing in microstructure thus increasing hardness introduced low ability of hole flanging. From experimental results, it was found that the hole making by wire cut process shows highest hole expansion ratio. The hole from piercing with counter punch can be increased the hole expansion ratio more than hole from piercing process.