Simulation And Optimization Of LP Rotor Heating Process

With the rapid development of computer technology, heat treatment computer simulation is receiving increasing attention, and has become an essential part in the process study and design of current heat treatment technology. As important equipment parts, the demand of large forgings'quality and performance are increasingly higher. To meet the needs, the heat treatment process of large forgings, a method to improve the forges performance, has to be improved. It is difficult to make out the proper heat treatment process by traditional empirical and qualitative method for the large forgings. So, in order to save resources, heat treatment simulation technology has appeared as a new solution way. For large forgings, heat treatment process is of great significance in improving the workpiece performance and reducing the deformation and cracking tendency.Completely considering the temperature field, the microstructure field and the internal stress field of the heating process, a FEM model of heating process has been built based on the software package MSC.MARC. Based on the quenching requirement for the temperature and microstructure, the optimization principles are set, and the old heating processes have been simulated and analyzed. The heating processes of LP rotors with different diameter have been optimized by altering different process parameters, such as heating rate, the middle holding temperature, holding duration, and so on.With the aid of computer simulation, the influence of different process parameters on the microstructure transformation, temperature uniformization and thermal-stress has been analyzed. The results show that: the heating rate of the first heating stage can effectively reduce the first largest temperature difference and the thermal-stress between the surface and center of the rotor; the reduction of the second holding step temperature can slightly reduce the first largest temperature difference and the thermal-stress,and its increasing can effectively decrease the second largest temperature difference and shorten the austenization beginning time gap between surface and center of LP roter; the austenization of the LP rotor is mainly related with the heating rate of the second heating stage, the higher the heating rate, the bigger time interval between austenization beginning time of the surface and center, and the more time needed to lessen the temperature difference between surface and center.Based on the simulation results, the heating process of LP rotor with the diameter of 1768mm and 2826mm are respectively optimized. Although the total heating time increases 20.6 and 60 hours respectively in the optimized heating process, the temperature difference between surface and center of LP rotor can be under 10℃,the whole rotor can be homogeneously austenized, and the biggest thermal-stress can be reduced effectively.