Mechanical Characterization of the Welded Region of Tailor Welded Blanks (TWB) from the Microhardness Profile

Abstract

Tailor Welded Blank (TWB) are plates of different specifications welded before forming. The narrow weld length may hamper its characterization in the welded region by conventional tensile methods. New methodologies and alternatives are analyzed. This work aimed to mechanically characterize the welded region of an internal vehicle door panel, manufactured by TWBs. Indirect mechanical characterization of the welded region was performed from micro hardness test - ASTM-E140 and ISO 18265-2013 - and the direct conversion of hardness to ultimate tensile strength (UTS) equation. The results were correlated with tensile test of the base materials, showing the best conversion. ISO 18265-2013 was the one that came closest to the direct test, with a maximum deviation of 30% and a minimum of 9%, with the most pronounced deviation as the mechanical strength of the material increases. In other methods, the maximum deviation can reach 40%, being smaller (11% to 18%, for equation) when the material has lower UTS. Despite the observed deviation, the technique used proved to be useful for predicting the deformation states and the extent of the weld zone (WZ) and the heat affected zone (HAZ) of a TWB.

Key-words:
Forming; Laser welding; Tailor Welded Blank; Auto industry