The lateral extrusion of copper pipes with a lost core of low temperature melting alloy

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 C1220 (Cu 99.9 wt.%; P 0.04–0.01 wt.%). The outline of the process is as follows: first, the cavity of the pipe is filled by liquid of Bi49Pb18Sn12In21 low temperature melting alloy. Then the low temperature melting material is solidified to form soluble core of the pipe. The authors call this soluble core the ‘lost core’. 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. To compare with the results of plain bulge forming under hydrostatic pressure by Fuchizawa et al., the forming limit is improved drastically in the present case. The process can be performed by simple compression machine without sealing of the forming tools.