Rotary Welder for Hot Billets
The use of two-piece billets in aluminium extrusion is often viewed as a necessary evil. A heating system that provides two-piece billets to the press can provide better ingot utilization than a heater which provides single-piece billets. The issues associated with the handling and extruding of two-piece billets are accepted as the price of improved ingot utilization. With the rotary welder, the end of each log segment is joined to the front of the following log by friction welding. The combination of the rotation of the short piece and the pressure applied creates a bond that will maintain one-piece integrity as the billet is conveyed to the press and loaded into the container. The handling issues associated with two-piece billets are eliminated. A unique re-cut cycle removes contaminants from the two weld faces immediately prior to welding. The two ends are precisely aligned and the saw makes a cut that removes the face of the remaining piece and the face of the following log. This re-cut removes debris, oxide and potential trapped air from a less than perfect cut at the cast house. The welding is then performed with the two freshly cut faces. The metallurgical performance is improved by the removal of debris and oxide on the faces. This allows the use of welded billets in some applications that previously required single-piece billets to achieve the necessary structural integrity.
M.S. Dargusch & S.M. Keay
D. Jenista "Rotary Welder for Hot Billets", Materials Science Forum, Vols. 618-619, pp. 245-248, 2009