STUDY OF THE INFLUENCE ON THE MECHANICAL PROPERTIES BETWEEN DISSIMILAR SHEETS WELDED WITH GAP IN THE MIG/MAG PROCESS APPLIED TO BODIES IN THE AUTOMOTIVE INDUSTRY

The automotive industry currently accepts, according to DIN EN ISO 5817, 2014, that the joint spacing welded by the MIG / MAG process be 0.2 mm + 0.07x the thickness of the thinner base metal. However, during the industrial process, part of the production must go through rework processes that negatively impact both the costs and the production time of the cars. The present work studies the impact of the spacing between the dissimilar plates widely used in the car body structures. The steels 22MnB5 (DIN EN 10083-3) produced by Hot Stamping and the steels HX 340 LAD (DIN EN 10346) produced by cold rolling were studied. Specimens were subjected to MIG / MAG welding with constant current of 128.0 A, constant welding speed of 7.6 m.min-1 and constant welding voltage of 19.1 Vin robot for KUKA VKRC4 welding, with six axes with a repeatability guarantee of 0.06mm. The samples were studied with spacing of 0.12 mm; 0.36 mm; 0.48 mm; 0.60 mm; 0.78 mm, in addition to those control specimens where the spacing was zero. Mechanical tests on tensile, bending, penetrating liquid and Scanning electron microscopy proved that, regardless of the spacing imposed on welded joints, the mechanical properties are maintained with the breaking of the sheet of lower mechanical strength. The penetrating liquid tests performed after the bending tests showed integral joints without the presence of cracks and clefts in the weld region. Both reported results were confirmed by the micro structural tests performed, where it was observed that the marten site destabilization characteristic of the plates produced by Hot Stamping did not occur.