Study Of The Macro And Micro Influences Of Mandrel Roller On Titanium Alloy Radial Ring Rolling

Titanium alloy ring is widely applied in the aerospace field because of its excellent mechanical properties. At present, most of titanium alloy ring is manufactured by ring rolling technology, which is an advance plastic forming processing. Titanium alloy ring rolling is a nonlinear, time-varying and unsteady thermal-mechanical coupling process. The mandrel roller is an important component of forming rolling machine. During the rolling process, it has an obvious influence on macro shape and microstructure of the final forming ring. In order to optimize the process and improve product performance, it is necessary to study the effect of mandrel roller on the ring rolling. In this paper, theoretical analysis and numerical simulation methods is adopted to study the influence of mandrel roller on titanium alloy ring rolling. The research contents and results are as follows:A TC4 titanium alloy radial ring rolling model is established by solving some key problem such as roller’s movement, geometric modeling, meshing and boundary conditions. Compared with the theoretical result, the finite element model is proved to be reliable.Based on the software of Absoft Pro Fortran 8.0, a secondary development program on DEFORM is developed. This program is inserted into the finite element mode, which realizes the simulation of heat transfer, deformation and microstructure evolution.A reasonable rolling process with different parameters for titanium alloy ring rolling process is designed. Through the simulation of rolling process, the changing law of temperature, equivalent strain and fishtail coefficient is revealed. Results show that the distribution of temperature and equivalent is uneven and the fishtail coefficient increase gradually during the rolling process. The influence of mandrel roller is studied by changing the mandrel roller size, feed speed and friction coefficient. The results show that with the increase of mandrel roller size, the equivalent strain and temperature distribution can be more uniform under an optimum size, and the fishtail coefficient also reaches the minimum; with the increase of feed speed, the distribution of strain and temperature would be more uniform and the fishtail coefficient would be smaller; with the friction coefficient increase, the distribution of strain would be more uneven and the friction condition has a little influence on temperature and fishtail coefficient.Based on the rolling process, the evolution and distribution laws of dynamic recrystallization volume fraction, grain size and average grain size are studied. The results show that with the rolling process, the recrystallization volume fraction and recrystallized grain size is increased gradually, and the average grain size decreases gradually. The grain of final ring has been refined. The influences of mandrel roller size, feed speed and friction coefficient on the ring microstructure are studied. The results showed that the distributed of recrystallized volume fraction average grain size would be more evenly under an optimum size; with the increase of feed speed, the distribution of recrystallized volume fraction and average grain size would be more evenly; the friction condition has little influence on the distribution of recrystallized volume fraction and average grain size.The research results of this paper provide a theoretical guidance for mandrel roller parameters optimization, forming quality prediction and control.