Abstract
The production of massive steel-aluminium hybrid components by means of massive (hot) forming following a joining operation requires advanced heat treatment strategies for the adjustment of local material properties with maximum joint strengths. For the given process-step sequence, the challenge is that the heat treatment of the hybrid component can only take place in the joined state and after (hot) forming. Consequently, suitable heat treatment strategies must enable both a T6 heat treatment of the aluminium component and a surface hardening of the steel component. It could be shown that the inductive surface hardening of a steel functional surface in the immediate vicinity of the aluminium component can take place without reducing the bond strength. To achieve the desired hardening result, the use of a field former is required. The bond strength could be increased by up to 20% compared to the friction-welded initial conditions by adjusting the parameters of the T6 heat treatment.
Kurzfassung
Die Fertigung von massiven Stahl-Aluminium-Hybridbauteilen mittels einer auf eine Fügeoperation folgenden (Warm-)Massivumformung erfordert besondere Wärmebehandlungsstrategien zur Einstellung lokaler Werkstoffeigenschaften bei höchsten Verbindungsfestigkeiten. Herausfordernd ist, dass die Wärmebehandlung des hybriden Bauteils aufgrund der Prozessschrittabfolge erst im gefügten Zustand nach der (Warm-)Umformung erfolgen kann. Geeignete Wärmebehandlungsstrategien müssen dementsprechend sowohl eine durchgreifende T6-Wärmebehandlung der Aluminiumkomponente als auch eine Randschichthärtung der Stahlkomponente ermöglichen. Es konnte gezeigt werden, dass das induktive Randschichthärten einer Stahlfunktionsfläche in unmittelbarer Nähe zur Aluminiumkomponente ohne Reduzierung der Verbundfestigkeit erfolgen kann. Zur Erzeugung des gewünschten Härteergebnisses ist der Einsatz eines Feldformers erforderlich. Die Verbundfestigkeit konnte gegenüber reibgeschweißten Ausgangszuständen durch eine Anpassung der Parameter der T6-Wärmebehandlung um bis zu 20% gesteigert werden.
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