8. Conclusion

Although the MAG process has been the subject of numerous articles and theses. There are few data available in the literature on MAG welding of sheet metal for the automotive industry. The available data indicate that MAG welding of clinch-welded THR steels produces fractures in four distinct modes:

• The weld strength is equivalent to or greater than that of the base metal;

• fracture in the heat-affected zone: fracture occurs in the heat-affected zone in the vicinity of Ac1, which generally has a hardness well due to the tempering of the hard constituents of the base metal microstructure;

• fracture in the molten zone/heat-affected zone connection zone: the metallurgical mechanism(s) governing this fracture mode have not yet been specified;

• fracture...