Effect of YAG laser cutting on stretch-flangeability of TRIP steels

Abstract

The effect of YAG laser cutting on the stretch-flangeability of transformation-induced plasticity (TRIP)-aided dual-phase sheet steels (TDP steels), which had different contents of C, Si and Mn, was examined. In TDP steels in which Si and Mn contents were constant and C content was varied ((0.1-0.4)C-1.5Si-1.5Mn, mass%), the strength - stretch-flangeability balance (TS×λ) of holes obtained by either laser cutting, hole-punching or drilling decreased with increasing C content. When the C content was 0.3 mass% or higher, the λ value in the case of laser cutting, which originally was as good as that in the case of drilling, decreased to a level comparable to that in the case of hole-punching. On the other hand, in TDP steels in which Si and Mn contents were varied and C content was kept constant (0.2C-(1.0-2.0)Si-(1.0-2.0)Mn, mass%), the λ value of the hole obtained by hole-punching was low under high TS; however, the value was greatly improved by laser cutting. Based on the above results, we demonstrated that YAG laser cutting contributes to the improvement of the stretch-flangeability of 980-MPa-class TDP steels with 0.2 mass% C.