Lateral extrusion of A6063 aluminum alloy pipes with a lost core

In this paper, the authors report a new bulging process of pipes, which is lateral extrusion with a lost core (LELC) and its application on pipes of A6063 aluminum alloy. The outline of the LELC process is as follows. First, the cavity of the pipe, or channel material, is filled by liquid of low temperature melting material, for instance, low temperature melting alloy, ice (or water) and wax. Then the low temperature melting material is solidified to be a soluble core of the pipe. The authors call this soluble core the ‘lost core’. Third, the material is compressed longitudinally as a composite billet, and extruded in the lateral direction. After deformation, the low temperature melting material is melted and removed. One can also use some soluble materials in some liquid, such as salt, instead of low temperature melting material. In this paper, the authors apply the method to bulge A6063 pipes using a lost core of Bi49Pb18Sn12In21 low temperature melting alloy. The observed maximum bulged diameter is 1.84 times the original pipe diameter when the ratio of the outer diameter to the bulge length l0/d0 is 0.63. Compared with the result of plain bulge forming under hydrostatic pressure by Fuchizawa et al., the forming limit is improved drastically.