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Experimental and Numerical study on Resistance Spot Welding of Aluminum to Aluminum Clad Steel Sheet

Ahmadi, Reza | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56758 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Movahedi, Mojtaba; Serajzadeh, Siamak
  7. Abstract:
  8. Resistance spot welding is one of the types of sheet metal joining processes used in many industries, such as automotive, home appliances, and aviation. In the direct welding of aluminum to steel, brittle intermetallic compounds are formed, which is necessary to control the thickness of these intermetallic compounds to improve welding properties. Using an aluminum-clad layer can effectively reduce the thickness of intermetallic compounds by reducing the heat generation at the steel-aluminum interface. This research aims to investigate experimentally and theoretically the welding of aluminum-clad steel sheet to Al-Mg aluminum sheet by resistance spot welding process with finite element method and Abaqus software. At first, a layer of commercially pure aluminum was cladded on the steel sheet by the rolling process and then investigated experimentally and theoretically the welding of aluminum-clad steel sheet to Al-5083 sheet. This research investigated the effect of welding current (11-16 kA) and thickness of the aluminum clad layer (3.0 mm and 1 mm) on the size and microstructure of the weld nugget and the percent of electrode indentation in the base sheets. The results showed that the metallurgical bond between the steel sheet and the aluminum-clad layer reduced the electrical contact resistance and heat generation. As a result, no melting was formed in the steel sheet. For welding with two different aluminum-clad layer thicknesses, it was found that with the increase of the welding current due to the rise of the input heat, increase in the size of the weld nugget, and the percent of electrode indentation in the sheets. Also, by reducing the thickness of the aluminum clad layer, heat loss is reduced, increasing the size of the weld nugget and the percent of electrode indentation. The ratio of the temperature gradient in the solidification front to the growth rate of the solidification front was calculate. To predict the microstructure of the weld nugget, and it was in acceptable agreement with the experimental results. The results showed that with the increase in welding current, the distance between the electrode and the molten pool decreases, and the structure of the weld nugget changes from a columnar structure to an equiaxed grain structure. In measuring the diameter of the weld nugget, the way the nugget grows, and the percentage of electrode indentation in the sheet, an acceptable agreement was obtained between the simulation and experimental results. However, with the increase of the welding current and the occurrence of melt expulsion, the difference between the simulation results and the experimental results increased
  9. Keywords:
  10. Simulation ; Resistance Spot Welding ; Aluminum ; Aluminum Clad Steel Sheet ; Electrode Indentation ; Residual Stress ; Metallic Interconnect

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