Processing of laser joined aluminum-steel tailored blanks in overlap and butt joint configuration

Abstract

The formability is an essential requirement for future applications of laser joined aluminum - steel tailored blanks in the automotive industry e.g. for the deep drawing of floor panels. A laser joining process for aluminum-zinc-coated steel tailored blanks was developed and improved in recent years at BIAS. Generally, tailored blanks can be joined in butt and overlap configuration. However, the formation of intermetallic phases during the thermal joining of dissimilar materials has a significant influence on the mechanical properties of the joint and therefore also on the formability of the tailored blanks. The phase formation results in a deterioration of the mechanical properties of the joint. With locally restricted energy input and high joining speeds by application of the laser technology, the thickness of such phases can be minimized in both butt and overlap joining techniques below 2 µm. For the characterization of the seam morphology, optical and electron microscopy have been carried out in addition to the mechanical and formability characterization. Thereby fracture stresses of 166 N/mm2 at butt joints and 180 N/mm2 at overlap joints in combination with a promising forming behavior have been achieved.Within this paper both butt and overlap techniques will be presented. This includes the process technologies, the problems of the intermetallic phase formation and the resulting formability of the tailored blanks.The formability is an essential requirement for future applications of laser joined aluminum - steel tailored blanks in the automotive industry e.g. for the deep drawing of floor panels. A laser joining process for aluminum-zinc-coated steel tailored blanks was developed and improved in recent years at BIAS. Generally, tailored blanks can be joined in butt and overlap configuration. However, the formation of intermetallic phases during the thermal joining of dissimilar materials has a significant influence on the mechanical properties of the joint and therefore also on the formability of the tailored blanks. The phase formation results in a deterioration of the mechanical properties of the joint. With locally restricted energy input and high joining speeds by application of the laser technology, the thickness of such phases can be minimized in both butt and overlap joining techniques below 2 µm. For the cha...