Producing Mirror Surfaces on Extruded Aluminum Pipes by the Iinside-Ironing Process

Aluminum pipes with mirror surfaces were successfully produced directly from hot-extruded pipe-workpieces by the inside-ironing method newly devised by the authors. A pipe is set in a steel container with very smooth inner surface, and the inside of the pipe is then ironed by a punch. The grooves with a depth of about 1 (im which were formed on the outer surface of the pipe by extrusion are well flattened and completely disappear through the ironing process. The outer surface of the pipe can be finished to a mirror surface as the replica of the inner surface of container. The working conditions to perform the process were also studied. An axial compresive force Pc should be loaded at the upper end of the pipe during the process to prevent it from slipping off against he container. The force can be reduced as the punch semi-angle decreases and/or the friction at the surface of container increases.