Microstructure and fatigue resistance of high strength dual phase steel welded with gas metal arc welding and plasma arc welding processes |
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Authors: | Godwin Kwame Ahiale Yong-Jun Oh Won-Doo Choi Kwang-Bok Lee Jae-Gyu Jung Soo Woo Nam |
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Affiliation: | 1. Department of Materials Science and Engineering, Hanbat University, 125 Dongseo-daero, Yuseong-gu, Daejeon, 305-719, Korea 2. Research & Development Division, Hyundai Motor Group Automotive, 150 Hyundaiyeonguso-ro, Hwaseong, Gyeonggi-do, 445-706, Korea 3. Global Coordination Center-China, Hyundai Motor Group Automotive, 150 Hyundaiyeonguso-ro, Hwaseong, Gyeonggi-do, 445-706, Korea 4. KISTI ReSEAT Program, Korea Institute of Science and Technology Information, 66 Hoegi-ro, Dongdaemun-gu, Seoul, 130-741, Korea
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Abstract: | This study presents the microstructure and high cycle fatigue performance of lap shear joints of dual phase steel (DP590) welded using gas metal arc welding (GMAW) and plasma arc welding (PAW) processes. High cycle fatigue tests were conducted on single and double lap joints under a load ratio of 0.1 and a frequency of 20 Hz. In order to establish a basis for comparison, both weldments were fabricated to have the same weld depth in the plate thickness. The PAW specimens exhibited a higher fatigue life, a gentle S-N slope, and a higher fatigue limit than the GMAW specimens. The improvement in the fatigue life of the PAW specimens was primarily attributed to the geometry effect that exhibited lower and wider beads resulting in a lower stress concentration at the weld toe where cracks initiate and propagate. Furthermore, the microstructural constituents in the heat-affected zone (HAZ) of the PAW specimens contributed to the improvement. The higher volume fraction of acicular ferrite in the HAZ beneath the weld toe enhanced the PAW specimen’s resistance to fatigue crack growth. The double lap joints displayed a higher fatigue life than the single lap joints without changing the S-N slope. |
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