These slides were presented at the NAFEMS World Congress 2025, held in Salzburg, Austria from May 19–22, 2025.

Abstract

In hot ironing process, cup shaped work piece is pushed through a set of dies with decreasing inner diameters. A punch applies pushing force from inner cavity while supporting work piece. The thickness of the work piece is determined by punch and ring diameters. Cylindrical parts with precision thickness can be manufactured using this process. When reduction ratio which is defined as final thickness over initial thickness is high, more than one die is used and the thickness of work piece is gradually thinned. Maximum punch force should be carefully considered for successful design of manufacturing operations. One of the parameters limiting maximum force is machine load capacity while another aspect is structural capacity of the work piece since it is at elevated temperature. Inner surface of the dies interacting with work piece endure contact pressure, work piece sliding and elevated temperature. Final dimensions of the work pieces is affected by die inner profile and temperature change during process. The speed of punch movement is another important parameter since material behavior is strain rate dependent at elevated temperatures. Also, contact time between work piece, dies and punch is important for temperature change in the dies. Die inner profile consists of die angle at the entrance and exit as well as diameter of inner opening. In addition, stiffness of die and its surrounding is important for final work piece outer diameter. Under the action of punch movement, a process force with axial and radial load components is exerted on the dies. Therefore, radial expansion must be controlled for precise dimensioning of final work piece. Successful operation of ironing process depends on different parameters such as work piece temperature change, friction, deformation of dies. Understanding effect of parameters and interaction between them can be achieved by accurate numerical modeling of whole process. In this study, a finite element model of multi stage hot ironing process was constructed and verified with experimental study. Dimensions of the final part and process force was compared with numerical results. After finite element model was verified, effect of parameters such as axial distance between dies, friction, punch speed, die inner profile was investigated. Maximum punch force, die wear, die temperature and deformation are important output parameters monitored under different configurations. Since complete production environment was included in the finite element model, complex interaction between parameters of a complicated production process can be identified.