Joining method cuts weight

Honda's new technology could contribute to fuel economy improvements

Japanese carmaker Honda has developed a method of joining steel and aluminium that it plans to apply to mass-production vehicles.

The first application of the technique was with an aluminium outer door panel, which was conventionally made of steel, to join it to a steel inner door panel.

The joining process involves the simultaneous establishment of several different technologies to prevent electrical corrosion and thermal deformation caused by the different expansion rates of the two materials.

The joining of the materials involved the adoption of a 3D Lock Seam structure, where the steel panel and aluminium panel were layered and hemmed together twice. 

Electrical corrosion was prevented by the use of highly anti-corrosive steel for the inner panel and a new form that assures the complete filling of the gap with adhesive agent. Finally, thermal deformation was controlled by adoption of an adhesive agent with low elastic modulus and the optimised position of the 3D Lock Seam. 

Honda said that the advantages of the new technologies included elimination of a spot welding process required to join conventional steel door panels. Moreover, the new approach does not require a dedicated process. As a result, existing production lines can accommodate the new technologies.

In everyday use, the joining technology could contribute to the improvement of fuel economy and dynamic performance of the vehicle by reducing door panel weight by approximately 17% compared to the conventional all-steel door panel. In addition, weight reduction at the outer side of the vehicle body concentrates the point of gravity further towards the centre of the vehicle, contributing to improved stability in manoeuvring.

Honda said it would introduce the technology on the North American version of the all-new Acura RLX but plans to expand its application to other models later.