Papers by Keyword: Hot Metal Gas Forming

Abstract: In carbon-free technologies, thin-walled components with microchannels from ultra-thin sheets, such as bipolar plates, cooling plates, and heat exchangers, are widely utilized. Using such components made of high-strength aluminum alloys further reduces the required wall thickness, thereby enhancing their lightweight potential. However, conventional forming methods for ultra-thin sheets, including elastomer-based deep drawing and hydroforming, are limited by process-induced phenomena such as springback, geometrical inaccuracies and reduced formability as well as localized thinning, which can necessitate a higher wall thickness or the use of a lower strength grade alloy. Gas-based hot sheet metal forming of high-strength aluminum alloys is introduced to improve formability and geometrical accuracy. In the present study, an isothermal, gas-based hot sheet metal forming process is developed for forming microchannels from AlMg3 alloy sheets with a thickness of 0.4 mm. A 100 mm × 100 mm blank is heated to 530 °C and formed under nitrogen gas pressure into a heated die featuring various channel geometries. The effects of blank-holder force, maximum gas pressure, wall angle, channel radius, and maximum channel depth on thinning and form filling are investigated. Additionally, the grain size of the final component is analyzed. A full form filling can be reached under a forming pressure of 200 bar. The thinning is dependent on the micro channel geometry and reaches a maximum of 29 % for a channel depth of 1 mm. The grain size increases during the forming process, dependent on the introduced strain into the material. The proposed method enables forming of components without fracture and with high geometrical accuracy.

Abstract: The continuous need of improved performances in automotive in terms of dynamic behaviour, fuel consumption and safety of passengers, have raised the interest for lightweight alloys as well as for the optimization of the design of the structural components of the car chassis. With this twofold aim, many researches are focused in the evaluation of new car designs, materials, and processes to manufacture even more complex components with increased stiffness-to-weight ratio. From that standpoint, the use of shaped hollow parts in the car body in white appears one of the most promising solutions, due to the elevated stiffness of tubular structures and the reduced weight. However, hydroforming processes that have been traditionally used to shape such components have shown several limitations with lightweight alloys, suffering their reduced formability, the temperature limitations of the forming liquids as well as long process time and complex machines. In this paper the recently introduced technology of Hot Metal Gas Forming (HMGF) has been considered, in order to investigate the influence of the process parameters on the formability of AA6060 tubes. The semi-finished tubes were produced through direct hot extrusion, with different temperatures and feed rates process, and tested by HMGF at elevated temperatures. The properties of the final products are investigated through analyses of the microstructure, micro hardness and thickness measurements.

Abstract: A hot gas bulging process of an aluminium alloy tube using resistance heating set into a die was developed. In the developed process, the tube was heated during the forming, and thus the drop in temperature was prevented. The control of the hot gas bulging was simplified by sealing air in the tube. The tube was bulged by thermal expansion of the air sealed in the tube without control of internal pressure during the forming. Hot gas bulging of an aluminium alloy tube without and with the axial feeding was performed. The deformation behaviour of the tube in the die was observed by a heatproof glass plate inserted in the die. The timing of the axial feeding, the feeding velocity and the amount of the axial feeding were optimised.