Influence of the substrate on the laser brazing ability of typical products developed for the automotive industry

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Influence of the substrate on the laser brazing ability of typical products developed for the automotive industry

Bailly, Nicolas / Cretteur, Laurent / Koltsov, Alexey

In Europe, laser brazing is nowadays standard to realise visible joints on exposed parts for targeted applications such as boot lids and roofs. One issue of this advanced joining technology is the formation of random external porosities in brazed joints. Because this process is dedicated to visible parts, no external defect can be allowed. This paper describes the experimental method developed by ArcelorMittal to characterise the robustness of this advanced joining technology on automotive products: hot-dip-galvanised steel sheets (Gl 8 micrometer), electrogalvanised steel sheets (EG 8 micrometer) and bare steel. It was experienced that the Gl coating nowadays remains the best product solution to stabilise the laser brazing process on exposed panels thanks to its wider process windows in comparison with EG and bare steel. In other words, Gl is less sensitive to small process variations which could potentially have an impact on the seam quality in body shops. In contrast, uncoated steel sheets are more sensitive to the formation of external porosities due to the presence of iron oxides on the sheet surface.