The Joining Process

The EJOWELD® Process

EJOWELD® is a thermomechanical process where energy is generated through rotatory friction between an element and the base plate. This leads to plastic deformation of the joining element and welding with the base plate. The cover plate is simply penetrated and fixed between the element head and base plate. The connection results from a combination of form-fit, force closure and adhesive bond.

Advantages of EJOWELD®

  • No pre-hole
  • No pre or post treatment of the joining materials
  • No brittle intermetallic phases, as there is no thermal adhesive bond between aluminium and steel
  • The technology of the joint is a combination of form closure, force closure and adhesive bond control of the linear expansion differences between aluminium and steel induced by temperature changes
  • A high number of material thickness combinations can be joined without modifications to the equipment

The Joining Process

The steel friction element penetrates the upper layer (e.g. aluminium) and welds onto the base plate, which is made of high-strength or ultra-high strength steel. The friction, which is generated by the appropriate process control and application of mechanical forces, acts directly on the friction element. The produced frictional heat affects the element and the base plate without reaching their melting temperature. An adhesive bond is only created between the friction element and the base plate. Between the friction element and the upper layer, force and form closure is achieved. When the head of the element has reached the upper plate, the rotation stops and an increased axial force is applied onto the friction element. Only then the friction welding process is completed. The upper layer is now fixed between the head of the friction element and the base plate. The friction element thus fulfils two separate tasks during the joining process. First task is to penetrate the cover sheet without altering its properties, and secondly to reliably generate the frictional heat to create a steel to steel bonding.