Effect of Double Pulse Resistance Spot Welding Process on DP980 Dual Phase Steel and 15B22 Hot Stamped Boron Steel

Abstract

Double pulse resistance spot welding process by applying a second step welding current is a new pathway to alter the mechanical properties for advanced high strength steels Herein the resistance spot welding (RSW) of dual phase DP980 and hot stamped boron steel 15B22 by one-step and two-step welding with different welding currents is investigated The results of the tensile–shear test size of the weld nugget hardness distribution microstructure and failure mode of different welding parameters are analyzed The weldment of the two-step RSW with a higher heat input exhibits a lower tensile–shear load and lower fracture energy when the size of the weld nugget is large The microstructural study reveals the appearance of a partially melted zone and sub-critical heat affected zone in the weldment where the fracture readily occurred Thus the two-step RSW process weakens the strength of the sample which is attributed to the partial softening in the weldment due to the higher heat input

Date of Award	2021
Original language	English
Supervisor	Hwa-Teng Lee (Supervisor)