Improvement of the Electrical Conductivity between Electrode and Sheet in Spot Welding Process by Direct Laser Interference Patterning

Abstract

The effort of automotive industry is the increasingly use of aluminum alloys to reduce the weight of the car. Regarding the lifetime of electrodes and the process reliability resistance, spot welding is not applied for joining of aluminum sheets. Instead, more expensive processes must be used, like riveting with supplementary component. This is caused by the electric isolating oxide layer at the sheet surface. This layer normally shows an irregular topography, causing a locale temperature increase and therefore high electrode wear. In this study, a new concept to increase the electrode lifetime and process reliability is reported. Using Direct Laser Interference Patterning, periodic surface patterns are produced at the contact area between the electrode and the sheet for influencing the contact resistance. The resulting topography and morphology are analyzed by confocal microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The electrical resistance between the contact partners copper and aluminum is measured during spot welding tests and contact resistance studies. A reduction up to 50% of the electrical resistance by treating the electrodes or an increase of more than 100 times by treating the sheets can be achieved compared to the untreated references.

Picosecond Laser Interference Patterning of Periodical Micro-Architectures on Metallic Molds for Hot Embossing

“…It can be seen that the appearance of the laser processed area changes from the shiny untreated metal (bottom left corner) to a matte and dark finish (top right corner). This can be associated with the formation of an oxide layer during the laser process and light scattering and diffraction effects caused by the periodic structures on Cr surface [52]. Furthermore, the areas treated with different laser parameters exhibit different reflected colors, attributed to variations in lateral size and structure heights of the induced structures as well as variation in the oxide layer thickness [53].…”

Dynamic, Adaptive Inline Process Monitoring for Laser Material Processing by Means of Low Coherence Interferometry

“…In the case of classic electrical sheet, several layers of steel and insulation materials are stacked. Electrical steel is used in a wide range of applications, from transformers and sensors to motors and generators [1][2][3][4]. One of the most important aspects of electric steel is the energy density.…”

Prediction of Optimum Process Parameters Fabricated by Direct Laser Interference Patterning Based on Central Composite Design

“…For instance, these well-defined and highly-oriented structures fabricated at the micron and sub-micron scale on surfaces of modern industrial products enable a clear innovation potential to improve products performance significantly [ 3 ]. This upgrade concerns a wide range of applications, such as antifouling [ 4 ], wetting control, [ 5 , 6 ], tribology [ 7 , 8 , 9 , 10 ], electrical conductivity improvement [ 11 ], cell adhesion [ 12 ], as well as surface optical appearance alteration [ 13 , 14 ]. However, the reproduction of these versatile surface structures represents one of the most significant technical challenges today due to their complexity.…”