Numerical Study of the Effect of Workpiece Thickness on the Interfacial Behavior of a Molten Aluminum Droplet on a Zinc-coated Steel Sheet

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.

Metallurgical Analysis as a Useful Method for Fire Investigation: the Case of Galvanized Steel Sheets

In this work, fire simulations were carried out on zinc-coated steel sheets usually employed for the structural parts of furniture, transformer rooms and aeration pipes. The thermal alteration induced by the fire was simulated by heating samples at 13 different temperatures (from 20° C to 1050° C) and for different exposure times (1 h and 6 h) in a laboratory furnace. The metallurgical investigation concerned the surface coloring by photographic analysis, the morphology and chemical composition of the surface oxides by SEM and EDS and the microstructure modifications as a function of the temperature by LOM. The influence of the different parameters was discussed by a statistical approach. The obtained results allowed to associate the temperature to one or more alteration of the steel microstructure and of the color, the morphology and the chemical composition of the surface oxides.

Microstructure and mechanical properties of 6082-T6 aluminum alloy–zinc coated steel braze-welded joints

The laser braze-welding technique was aimed to join a low alloyed zinc coated steel used in automotive industry, with a deformable, aging hardenable aluminum alloy from the 6xxx series using as filler material a AlSi12 wire. The heterogeneous joint was obtained by welding of aluminum alloy with the filler wire and by brazing of molten aluminum alloy together with the filler wire on the surface of a zinc coated steel which remained in solid state. The results showed that by using a proper heat input, the zinc coated steel was brazed without a melting process by the aluminum alloy which was in liquid state. On the interface between the zinc coated steel and the welded seam, a thin layer (the thickness was 6 to 8 μm) formed consisting of star (Al-Fe-Si) or needle shape (Mg-Al-Fe-Mn) intermetallic phases.

Experimental studies of the adhesion force between a zinc-coated steel plate and concrete

Introduction. The co-authors present the findings of experimental studies of the adhesion force arising between a zinc-coated steel plate and concrete. Four specimens were used in testing. Rectangular plates, embedded in a concrete parallelepiped, had different types of surfaces. They were smooth, perforated with holes, or they had connecting elements such as bolts or spikes. The behavior of specimens under loading is analyzed; graphs, describing the dependency between displacements and loading are provided, and the design resistance is determined to analyze the adhesion force between concrete and a zinc-coated steel plate. Materials and methods. Four specimens were used in testing. Each specimen represented a zinc-coated steel plate embedded in a concrete parallelepiped. A test bench, consisting of a load frame and a hydraulic cylinder, which pulled the steel plate out of a concrete parallelepiped, was used in the experiment. Results. Deformation dependences of specimens were obtained, graphs describing the dependence of displacement on loa­ding were drawn for four types of surfaces, loading values that trigger the failure of specimens and dependence between the loading value, that triggers the failure, and the structure of the embedded part of the plate, are identified. The nature of the concrete failure at the interface with a zinc-coated plate is tracked. Conclusions. The results of the experiment enable us to conclude that the joint action of concrete and a steel beam is possible without the use of additional elements in composite structures that have bent profiles. The adhesion properties of materials and the stamped part of the profile are capable of absorbing shear forces arising in structures. For a more accurate analysis of floor slabs that contain bent profiles, additional experimental studies are to be conducted. Specimens, having bent profiles embedded in concrete, will be tested in the course of these experiments.