PRESSURED-ASSISTED INJECTION FORGING OF THICK-WALLED TUBES

Numerous engineering components may be created in a hollow form without detracting from their performance requirements; the difficulty, however, is in the conversion of tubular materials into such components. Hollow components may be formed from tubular materials if these can be prevented from collapsing during the forming cycle. Further, die-filling during injection forging, is especially difficult at the terminal stages of the process; the use of a pressurising medium within the material could effect die-filling more effectively. The scope for the forming of thick-walled tubes into hollow components was investigated using different pressurising media to support the material during the forming cycle. A tubular hexagonal form was the basis for the evaluation of the forming requirements of the process. Several pressurising-media were tested experimentally to determine suitability and the process was stimulated using FE techniques to establish the ''optimal'' processing sequence. The pressurising-medium influences the forming sequence for the production of a component of acceptable quality. The forming sequence has three distinct stages. Injection forging of the tube has to be proceeded by an initial internal pressurisation while subsequent injection has to be matched by increases in pressurisation; the final stage is characterised by a rapid increase in pressurisation to complete the filling of the die. Failure to establish the correct sequence will result in different forms of failures; the correct sequence will enable the production of a component of ''uniform'' wall-thickness.