Özet:

In this study, the effect of welding speed (3, 3.5, 4 m/min) and focal length (0, 1.4 mm) on the mechanical properties of the welded structure was investigated in the overlap type joining of 1.2 mm sheet thickness DP600 dual phase steel sheet material by fiber laser welding method. For this purpose, tensile-shear tests were performed on the samples joined by laser welding method, and the tensile strength and elongation amounts were determined. Microstructure investigation and microhardness measurements of the welded area were carried out. It is determined that weld joint shape and penetration depth changes according to focal length distance and welding speed, and with the maximum welding speed specimens has the minimum penetration depth. Tensile-shear strength values decreased depending on the increased welding speed for both focal length specimens. It is observed that the microhardness results were affected by welding speed and focal lengths. In 0 mm focal length distance specimens’ hardness values increased according to the increased welding speed, but for –1.4 mm focal length distance the microhardness values decreased with an increased welding speed. The fracture zones and fracture surface morphology also affected by welding speed and focal distance. In 0 mm focal length, all the specimen fractured in base metal with a ductile fracture morphology, but in the –1.4 mm focal length, specimens fractured from the zones which are closer to HAZ and FZ with a brittle fracture morphology.

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