2023 Volume 41 Issue 1 Pages 42-51
Spot welding has stable quality, easy operation, and excellent productivity. Therefore, it is often used in vehicles and electrical products that use several thin sheets. The bonding principle is based on the nugget formed using joule heating. Furthermore, in recent years, the welding of steel and aluminum alloy has been used to improve the fuel efficiency of vehicles. The blowhole may occur in the bonding area. Moreover, as Fe2Al5 thickens, the interface likely becomes brittle. The growth of an intermetallic compound (IMC) depends on the temperature during joining. Considering that heat is generated by joule heating, the current density and other factors also affect the formation of IMCs. Another factor affecting IMC formation is the generation of the blowholes at the interface. If the contact pressure between the steel and the aluminum alloy is high, then the generation of blowholes may be suppressed. In investigating the effects of the electrode shape on IMC formation, numerical simulations of spot welding were performed using the DR6 electrode with a tip curvature of R40, hereafter referred to as DR6 (R40), and the DR12 electrode with a tip curvature of R400, hereafter referred to as DR12 (R400). During spot welding of steel and aluminum alloy, the blowholes were observed when melting the aluminum using DR6 (R40) and DR12 (R400) electrodes, and the coarse blowholes were observed in the central part of the electrode during the experiment using the DR12 (R400) electrode. The normal stress acting at the interface of the joint was also investigated using numerical simulations to examine the occurrence of the blowholes caused by the difference in electrodes.
