International Journal of Iron & Steel Society of Iran

International Journal of Iron & Steel Society of Iran

Effect of Laser Power on Microstructure and Tensile Properties of Laser Welded DP590 Steel Joints

Document Type : Research note

Authors
Hamid Ashrafi 1
Amir Reza Shahsavari 1
Ariyan Ghandi 2
1 Faculty of Chemical and Materials Engineering, Shahrood University of Technology, Shahrood 3619995161, Iran
2 Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran
10.22034/ijissi.2024.2008540.1269
Abstract
 This study investigated the effects of varying laser power on the microstructure and tensile properties of DP590 steel joints. Three joints were prepared using three different laser power levels (400W, 450W, and 500W), while keeping all other factors constant. The results indicated that laser welding resulted in the formation of martensite in the fusion zone, leading to a notable increase in hardness. However, with increasing the laser power, the hardness increment decreased due to the presence of acicular ferrite and Widmanstatten ferrite alongside martensite. The heat-affected zone (HAZ) of all welds exhibited a region where hardness dropped below that of the base metal (BM) due to partial tempering of martensite. This softening effect intensified with higher laser power. The sample welded with a laser power of 400W failed early in the tensile test due to lack of penetration. Conversely, the other two samples failed within the softened zone, showing yield strength values similar to the BM and high joint efficiency values (92.5% for 450W and 89.5% for 500W) but with a noticeable reduction in elongation. Both DP590 steel and welded joints exhibited a two-stage work hardening behavior consisting of a transient stage followed by a stage III hardening. 
Keywords
Dual-phase steel
laser welding
laser power
microstructure
tensile properties
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International Journal of Iron & Steel Society of Iran
Volume 20, Issue 1
June 2023
Pages 44-52