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.

No abstract

A hot metal gas forming process for an aluminium alloy tube using sealing pressure and resistance heating was developed. In this process, the sealed tube is bulged by resistance heating without controlling internal pressure. A hot metal gas forming process for an aluminium alloy tube without and with axial feeding was carried out. The deformation behaviour of the tube inside the die was observed through a heatproof glass plate attached to the side wall of the die. The sealing pressure, current density, timing of axial feeding, feeding velocity and amount of axial feeding were optimized. For excessive sealing pressure, fracture occurred, and the tube partially melted at a small sealing pressure and a large current density. Since the temperature of the tube rapidly drops after coming into contact with the die, the axial feeding before the contact is effective in preventing fracture. A ceramic die with a small thermal conductivity is useful for improving the temperature decrease and die filling.