Temperature-controlled tools for multi-stage sheet metal forming of high-strength aluminium alloys

Abstract The high-strength aluminium alloys EN AW-6082 and -7075 possess great light-weight construction potential due to their high specific strength. However, their range of applications is limited by the low cold formability and high springback in the ultra-high-strength T6 state. To extend formability, either preconditioned semi-finished products, requiring a subsequent heat treatment or temperature-supported process routes such as warm forming or hot forming die quenching (HFQ) are used. If the forming degrees achievable with these methods are not sufficient, multi-stage forming is required. The forming degrees are limited by strain hardening in case of a cold forming operation of preconditioned semi-finished products and by heat transfer between the component and the tool parts in case of temperature-supported process routes. In order to reduce or even eliminate the cooling of the component in the subsequent forming stages, a four-stage forming tool with temperature-controlled active parts was developed and its influences investigated in more detail. The paper will demonstrate how precise temperature control of the tool components contributes to an extension of the formability. In addition, reproducible and robust process conditions can be guaranteed throughout the entire process chain.