Development of laser welded stainless steel sandwich panels for lightweight vehicles: Design, manufacturing and properties

To gather background data for further bus floor structure development, laser welded sandwich panels made of stainless steels have been studied using weight optimizing as well as mechanical and corrosion tests. A PC-program developed for weight optimizing was first used in comparison of various sandwich panels. So called O panels assembled from cover plates and RHS-tubes were further subjected to mechanical tests using point-loading, 4-point-bending and fatigue testing. The corrosion behavior of the panels was studied by salt-spray chamber tests in an ice-control salt (CaCl₂) environment.

The results showed that austenitic EN 1.4301 (AISI 304) stainless steel exhibited a better combination of mechanical and corrosion properties in the O panels than does 12 %Cr alloyed EN 1.4003 steel. Use of 1.4301 steel in cold-worked condition (2H) further improves the point-loading and bending strength of the panels. Fatigue tests showed that laser welding results in considerably higher fatigue resistance than does resistance spot welding. 1.4301 steel shows adequate corrosion resistance in the sheet surfaces, whereas the resistance of 1.4003 steel remains considerably lower. However, the corrosion resistance of 1.4003 in particular, but also 1.4301 to some degree, becomes limited at crevices in the laser welded lap joints. Thus, measures to eliminate crevices from panel structures becomes of primary importance in practical applications.