PRESSURED-ASSISTED INJECTION FORGING OF THICK-WALLED TUBES

Numerous engineering components may be created in a hollow form withou t detracting from their performance requirements; the difficulty, howe ver, is in the conversion of tubular materials into such components. H ollow components may be formed from tubular materials if these can be prevented from collapsing during the forming cycle. Further, die-filli ng during injection forging, is especially difficult at the terminal s tages of the process; the use of a pressurising medium within the mate rial could effect die-filling more effectively. The scope for the form ing of thick-walled tubes into hollow components was investigated usin g different pressurising media to support the material during the form ing cycle. A tubular hexagonal form was the basis for the evaluation o f the forming requirements of the process. Several pressurising-media were tested experimentally to determine suitability and the process wa s stimulated using FE techniques to establish the ''optimal'' processi ng sequence. The pressurising-medium influences the forming sequence f or the production of a component of acceptable quality. The forming se quence has three distinct stages. Injection forging of the tube has to be proceeded by an initial internal pressurisation while subsequent i njection has to be matched by increases in pressurisation; the final s tage is characterised by a rapid increase in pressurisation to complet e the filling of the die. Failure to establish the correct sequence wi ll result in different forms of failures; the correct sequence will en able the production of a component of ''uniform'' wall-thickness.