Experimental Investigations of the In-Die Quenching Efficiency and Die Surface Temperature of Hot Stamping Aluminium Alloys
Department of Mechanical Engineering, Imperial College London, Exhibition Road, London SW7 2AZ, UK
School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083, China
Author to whom correspondence should be addressed.
Metals 2018, 8(4), 231; https://doi.org/10.3390/met8040231
Received: 28 February 2018 / Revised: 24 March 2018 / Accepted: 27 March 2018 / Published: 2 April 2018
(This article belongs to the Special Issue Material and Process Design for Lightweight Structures)
The in-die quenching is a key stage in the hot stamping volume production chain which determines the post-formed strength of lightweight alloy components, tool life, and hot stamping productivity. In this paper, the performance of in-die quenching, reflected by the quenching efficiency (the time of work-piece held within stamping dies) and die surface temperature during the simulated hot stamping process of AA6082, was experimentally and analytically investigated. A range of in-die quenching experiments were performed for different initial work-piece and die temperatures, quenching pressures, work-piece thickness, and die clearances, under hot stamping conditions. In addition, a one-dimensional (1D) closed-form heat transfer model was used to calculate the die surface temperature evolution that is difficult to obtain during practical manufacture situations. The results have shown that the in-die quenching efficiency can be significantly increased by decreasing the initial work-piece and die temperatures. Die clearances are required to be designed precisely to obtain sufficiently high quenching rates and satisfying post-formed strength for hot-stamped panel components. This study systematically considered an extensive variety of influencing factors on the in-die quenching performance, which can provide practical guides for stamping tool designers and manufacture systems for hot-stamping volume production.