The Effects Welding Speed and Focal Length on Mechanical Characteristic of Fiber Laser-Welded Structures of DP600 Dual Phase Steel

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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  • Aktarer, S. M., Küçükömeroğlu, T., & Davut, K. (2019). Friction stir processing of dual phase steel: Microstructural evolution and mechanical properties. Materials Characterization, 155, 109787. doi:10.1016/j.matchar.2019.109787
  • ASTM International. (2010). Standard Test Methods for Tension Testing of Metallic Materials (ASTM E8/E8M-21) doi:10.1520/E0008_E0008M-16A
  • ASTM International. (2012). Standard Test Methods for Coating Mass and Chemical Analysis of Zinc-Nickel Alloy Electrolytically Coated on Steel Sheet (ASTM E1659-12) doi:10.1520/E1659-12
  • Alves, P. H. O. M., Lima, M. S. F., Raabe, D., & Sandim, H. R. Z. (2018). Laser beam welding of dual-phase DP1000 steel. Journal of Materials Processing Technology, 252, 498-510. doi:10.1016/j.jmatprotec.2017.10.008
  • Çavuşoğlu, O., Toros, S., & Gürün, H. (2019). Microstructure based modelling of stress–strain relationship on dual phase steels. Ironmaking & Steelmaking, 46(4), 313-319. doi:10.1080/03019233.2017.1371959
  • Dai, J., Meng, Q., & Zheng, H. (2020). High-strength dual-phase steel produced through fast-heating annealing method. Results in Materials, 5, 100069. doi:10.1016/j.rinma.2020.100069
  • Farabi, N., Chen, D. L., & Zhou, Y. (2011). Microstructure and mechanical properties of laser welded dissimilar DP600/DP980 dual-phase steel joints. Journal of Alloys and Compounds, 509(3), 982-989. doi:10.1016/j.jallcom.2010.08.158
  • Ferreira, C. C. de A., Braga, V., de Siqueira, R. H. M., de Carvalho, S. M., & de Lima, M. S. F. (2020). Laser beam welding of DP980 dual phase steel at high temperatures. Optics and Laser Technology, 124, 105964. doi:10.1016/j.optlastec.2019.105964
  • Fonstein, N. (2017). 7 - Dual-phase steels. In: R. Rana & S. B. Singh (Eds.), Automotive Steels (pp. 169-216). Woodhead Publishing. doi:10.1016/B978-0-08-100638-2.00007-9
  • Gong, H., Wang, S., Knysh, P., & Korkolis, Y. P. (2016). Experimental investigation of the mechanical response of laser-welded dissimilar blanks from advanced- and ultra-high-strength steels. Materials & Design, 90, 1115-1123. doi:10.1016/j.matdes.2015.11.057
  • Hong, K., & Shin, Y. C. (2017). Prospects of laser welding technology in the automotive industry : A review. Journal of Materials Processing Technology, 245, 46-69. doi:10.1016/j.jmatprotec.2017.02.008
  • ISO (2016). Resistance welding - Destructive testing of welds - Specimen dimensions and procedure for cross tension testing of resistance spot and embossed projection welds (ISO 14273:2016) www.iso.org/standard/61273.html