Abstract
In brazing, the interfacial conditions between the molten filler material and the solid workpiece are important, yet they cannot be observed experimentally. A two-dimensional axisymmetric simulation was conducted to analyze the behavior of a single droplet of molten aluminum on zinc-coated steel sheet as a simplified brazing process. The simulation models were verified through a comparison with experimental results in terms of bead shape, zinc distribution, and molten metal behavior. The results show that Young’s equation was not valid in explaining the wetting behavior because of the instant solidification. In this respect, the effects of the workpiece thickness and wetting angle on the bead width were negligible. Two periods of time, namely, the times for the temperature difference and solidification and their ratio (interface number), were defined to analyze the temperature behavior at the interface over time as well as the effects of workpiece thickness. The interfacial temperature behaviors tended to be divided into three regions: linear (or inversely proportional), singular, and convergence. The interface number converged to a value of one with the increase in the thickness.
Highlights
Due to environmental issues, high strength steels, aluminum alloys, magnesium alloys, glass fiber reinforced thermoplastics, and their hybrid structures have received much attention in the automotive industry for the light-weight construction of car bodies [1]
The simulation results for the molten metal behavior were in a good agreement with the experimental ones derived from the highspeed camera
The behavior of a single aluminum droplet falling onto zinc-coated steel was studied using Computational fluid dynamics (CFD) simulation
Summary
High strength steels, aluminum alloys, magnesium alloys, glass fiber reinforced thermoplastics, and their hybrid structures have received much attention in the automotive industry for the light-weight construction of car bodies [1]. Most European car manufacturers use ultra-high-strength hot-stamped boron steels (UHSS) because these can significantly reduce the car body weight for a relatively low price. It is necessary to secure welding and joining technologies for the dissimilar materials of steel and aluminum alloy. The methods can be typically divided into mechanical and thermal processes. Unlike mechanical processes, such as riveting and clinching, thermal processes have the advantage of direct material connection, relatively high process speeds, and low process costs.
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