Abstract
Press-hardening is a comparatively time consuming forming process since both forming as well as quenching is performed in the die tool. In order to accelerate this process, an alternative cooling strategy is considered which is based on spray cooling outside the die tool. The object of our investigation is 22MnB5 material. Quenching tests show that sufficient cooling rates greater than 50 K/s can be obtained by means of water-air spray cooling using two-component nozzles. The strength values and fracture strains realised here correspond to the mechanical properties attainable during press-hardening. Furthermore, a plant design is presented which is suitable for cooling vehicle body parts such as tunnels in order to reduce the turnaround time by means of prematurely removing the components from the die-forming tool and subsequently cooling in a spray field.
Kurzfassung
Presshärten ist ein vergleichsweise zeitaufwändiges Umformverfahren, da im Werkzeug sowohl die Umformung als auch das Abschrecken erfolgt. Um diesen Prozess zu beschleunigen, wird eine alternative Abkühlstrategie außerhalb eines Werkzeuges auf der Basis einer Sprühkühlung betrachtet. Untersuchungsgegenstand ist der Werkstoff 22MnB5. Abkühlversuche zeigen, dass sich hinreichende Abkühlgeschwindigkeiten von mehr als 50 K/s mittels einer Wasser-Luft-Sprühkühlung unter Verwendung von Zweistoffdüsen einstellen lassen. Die erzielten Festigkeiten und Bruchdehnungen entsprechen den beim Presshärten erzielbaren mechanischen Eigenschaften. Zudem wird ein Anlagenkonzept aufgezeigt, dass zur Sprühkühlung von Karosserieelementen, wie Tunneln, geeignet ist, um eine Taktzeitverkürzung mittels frühzeitiger Entnahme des Bauteiles aus dem Umformwerkzeug und nachfolgende Kühlung in einem Sprühfeld zu realisieren.
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