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 ((O.1-0.4)C-1.5Si-1.5Mn, mass%), the strength-stretch-flangeability balance ( ) 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 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 value of the hole obtained by hote-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.