Advanced self-piercing riveting of ultra-high-strength steel through rivets with modified material properties

Ultra-high-strength steels like 22MnB5 have now become established in car bodies. As the thickness of parts in 22MnB5 has steadily increased over the past few years due to growing safety demands, especially with regard to the protection of battery packs in electric vehicles, the capability of conventional self-piercing rivets to pierce such parts has been exceeded. This paper thus presents an approach to the advanced self-piercing riveting of ultra-high-strength steel sheets in an increased thickness. By combining experimental and numerical methods, a major improvement in rivet performance can be achieved through a sweeping modification of the rivet material and the heat treatment in combination with a slight adjustment to the commonly used rivet geometry. This advance in rivet capability makes it possible to increase the joinability of 22MnB5 from a thickness of 1.7 mm to 2.3 mm.