Indexed by:期刊论文

Date of Publication:2017-05-25

Journal:APPLIED THERMAL ENGINEERING

Included Journals:SCIE、EI、Scopus

Volume:118

Page Number:266-282

ISSN No.:1359-4311

Key Words:Hot forming; HFQ; IHTC; Beck's method; 7075-T6; Heat transfer mechanism

Abstract:The IHTC (Interfacial-Heat-Transfer-Coefficient) between aluminum alloy and die during HFQ (Heat-Forming-Quenching) process is an important thermal parameter to reflect the heat transfer efficiency. In the present work, the instantaneous heat transfer law for high strength 7075-T6 alloy during HFQ process based on cylindrical-die model was investigated. The accuracy of IHTC calculated by Beck's non-linear estimation method (Beck's method) and heat balance method (HBM) were compared, and instantaneous IHTC of 7075-T6 alloy was acquired in experiment and analyzed in consideration of different contact pressure, surface roughness and lubricate conditions. Furthermore, the obtained IHTC was applied to the simulation process of typical U-type experimental model in order to validate the universality of heat transfer law. The result shows that the average IHTC goes near to 3300 W/m(2).K when pressure is above 80 MPa; Surface roughness can also affect the IHTC in HFQ process, but the effect mechanism is different from the boron steel in hot stamping process. The average IHTC decreases sharply when surface roughness increases in the range of 0.570-0.836 mu m, the value is from 3453 W/m(2).K to 2001 W/m(2).K under 80 MPa. Furthermore, surface lubrication can promote heat transfer efficiency and increase IHTC value when contact pressure is relatively high. (C) 2017 Elsevier Ltd. All rights reserved.