Product Code: PIC2008_304

Fialure Mechanisms of Laser Welds of Dp980 and Hsla450 Steels in Formability Testing
Authors:
M. Xia, University of Waterloo; Waterloo ON Canada
Norman Zhou, University of Waterloo; Waterloo Canada
Z. Tian, Central Iron & Steel Research Institute; Beijing Peoples Republic of China
Michael Kuntz, University of Waterloo; Waterloo Canada
Presented at PICALO 2008

In this paper, two steels, dual phase (DP) with banded martensite and high strength low alloy (HSLA) with almost isotopic mechanical properties, were investigated with YAG laser welding process in terms of formability with Limited Dome Height (LDH) testing method. The failure mode and dome height at fracture were examined on parent metal and welded blanks. It was found that rolling direction determined the failure mode of DP parent metal. The microcrack in testing initiates between ferrite/martensite or martensite/martensite interface. For welded blanks, the formability was totally controlled by the soft zone. The fracture for welded HSLA blanks in formability testing invariably initiated at fusion zone due to its ductility decrease caused by hardening. Two steels show markedly different sensitivity to welding process in terms of formability. DP blanks shows a significant decrease of formability height after welding while HSLA welded blank possess almost the similar as its parent metal.