Research on a hydro-pressing process of tubular parts in an open die

Abstract

To solve the problems involving in the closed die hydro-pressing process, such as flash and difficulty in taking the part out of the die cavity, an open die hydro-pressing process was proposed. The cross-sectional dimensional accuracy and the corner deformation were experimentally researched. Then, an analysis was employed to reveal the reason for uneven deformation of the section corners, and an effective solution was adopted. The reason is that an obvious difference exists in the bending moment between the four corners due to the existence of the friction. The values of the bending moment and circumferential force decrease gradually along the direction opposite to the movement direction. As a result, the uneven deformation between cross corners appears. A double-pass pressing process was put forward to counter-balance the effects of the friction by converting the direction of the friction force. It is demonstrated by the experiment that the rectangular cross section with high dimensional accuracy can be directly formed from a circular tube blank using the open die hydro-pressing process.