Microstructure and Tensile properties of Laser Welded Joints between DP590 Steel and Plain Low Carbon Steel

Document Type : Research Paper

Authors

Faculty of Chemical and Materials Engineering, Shahrood University of Technology, Shahrood 3619995161, Iran

10.22034/ijissi.2024.2019085.1275

Abstract

In this study, effect of laser power on the microstructure and tensile properties of dissimilar joints between DP590 steel and AISI 1012 steel were investigated. For this propose, three joints were prepared by laser welding using the laser powers of 400, 450 and 500 W. Results showed the formation of a mixture of Widmanstätten ferrite (WF), polygonal ferrite and ferrite-carbide aggregate in the fusion zone (FZ). Although no trace of martensite phase was detected in the FZ and heat affected zone (HAZ) of the AISI 1012 steel side, but Formation of martensite in the HAZ of the DP590 steel side resulted in the local hardening, while tempering of the pre-existing martensite in the subcritical HAZ of the DP590 steel side led to the formation of a softened zone. Furthermore, the hardness gradually increased from the AISI 1012 steel base metal (BM) to the FZ due to grain refinement and formation of WF. The sample welded with a laser power of 400 W failed from the FZ at early stages of tensile testing due to a lack of penetration defect, while the samples welded with laser powers of 450 and 500 W exhibited ultimate tensile strength values slightly above that of the AISI 1012 steel, and a significantly reduced total elongation value compared to both BMs.

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