Bending Parameters in Heat Assisted Air Bending of High Strength Steels

Abstract

The usage of high strength steels is a viable option for improving existing sheet metal constructions manufactured by air bending. This improvement can be achieved through increased payload, lighter structures or enlarged safety margins. Unfortunately, as these materials have limited cold formability, usually high strength steels cannot be formed with the same tooling as used for conventional steels. Thus, in the case of air bending, the forming punch for conventional steels should be substituted by a punch with a bigger radius. This substitution implies changes in the geometry of the final part and leads to redesigning of the complete structure due to the bigger bending radius of formed parts. Additional problems related with the usage of high strength steels are bigger bending forces during the forming process and much higher springback. These issues can be attenuated by heat assisted air bending. In this work, 6 mm plates of two different high strength steels - Strenx 700 MC and Strenx 1300 - are bent with near infrared lamps as a heating method. The experimental campaign has been performed to understand the evolution of following bending parameters: minimal bending radius, bending force, springback and bend allowance. The experimental campaign shows that heat assisted air bending with near infrared lamps is an attractive opportunity for overcoming problems related to bending of high strength steels.