A study of the heat transfer mechanism in resistance spot welding of aluminum alloys AA5182 and AA6014
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ORIGINAL ARTICLE
A study of the heat transfer mechanism in resistance spot welding of aluminum alloys AA5182 and AA6014 Michael Piott1 · Alexandra Werber1 · Leander Schleuss2 · Nikolay Doynov3 · Ralf Ossenbrink3 · Vesselin G. Michailov3 Received: 3 March 2020 / Accepted: 16 June 2020 / Published online: 25 September 2020 © Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract This work investigates heat transfer mechanism of aluminum resistance spot welding process. The main target is to determine thermal contact conductance and heat transfer coefficients for natural convection and thermal radiation at ambient air and forced convection inside the water-cooled electrodes. For this purpose, the heat transfer of hot sheets in a welding gun for aluminum alloys AA5182 and AA6014 is analyzed experimentally and numerically. The transient temperature field is measured by several thermocouples in a simplified experimental setup. Subsequent thermal-mechanical coupled finite element simulations of the experiments were used to calibrate the heat transfer coefficients. The heat transfer coefficient for natural convection and thermal radiation to ambient air is 13 mW 2 K and the heat transfer coefficient for forced convection of electrode water-cooling is 25,000 mW . The results indicate that the thermal contact conductance can be assumed ideal 2K for welding process. Additionally, the finite element model is validated by the measured and calculated dissipated heat due to forced convection. Finally, a sensitivity analysis is performed to compare the influence of maximum and minimum heat transfer coefficients of forced convection (water-cooling) on transient temperature field and dissipated heat of sample AA5182. Keywords Aluminum resistance spot welding · Heat transfer · FE simulation · Thermal contact conductance · Electrode water-cooling
1 Introduction The use of light metal alloys plays a key role for reducing weight and in this way emissions and fossil fuel consumption of vehicles. Thus, the use of aluminum alloys in car bodies is increasing and the joining of aluminum alloys becomes more important. In the present day, the most frequently used joining process in the body in white shop is resistance spot welding (RSW) because of advantages in automation, low cost, and short cycle time in high-volume production [1–3]. Michael Piott
[email protected] 1
Mercedes-Benz AG, Sindelfingen, Germany
2
Institute of Low-Carbon Industrial Processes, German Aerospace Center (DLR), Cottbus, Germany
3
Department of Joining and Welding Technology, Brandenburg University of Technology (BTU) Cottbus-Senftenberg, Cottbus, Germany
Different material properties, especially higher electrical and thermal conductivity, lead to different welding behavior of aluminum alloys, compared with conventional steel materials. For the extended integration of aluminum RSW into the body in white shop, an improved process understanding, including all essential effects and interdependencies for aluminum alloys, is required. Finite ele
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