Study On Simulation And Intelligent CAPP Of Forging Process For Steam Turbine Rotor

As a typical product of intensive technology among heavy forgings, the rotor of a steam turbine is large, heavy, high quality-demanded, of many metallurgical defects & long cycle and difficult to manufacture. The forging process simulation and intelligence are researched on the rotor of a steam turbine, which is of great significance to contribute to enrich and develop theories and technologies of forging process and to design the forging process of rotors reasonably and automatically.Stretching is the main process of heavy forgings upon which the quality of heavy forgings depends. Chamfering is the indispensable process of turning rectangular blanks into round ones but under negligence. Guided by the new forging theories and technologies, 3D elastoplastic FEM is applied to research of stretching and chamfering. Stress status of flat tool stretching is determined with various tool width ratios and blank width ratios. Not only axial tense stress that depends upon tool width ratio but also transverse tense stress that relies on blank width ratio exists in bodies stretched between flat tools. The critical tool width ratio without axial tense stress and the critical blank width ratio without axial tense stress are obtained and their relationship is discussed. Conclusions are theoretical base for determination of right stretching process. Flat tool chamfering is researched to make sure distribution of inner stress & strain and the flow law of metals. Tense stress is found at inner bodies under flat tool chamfering. As for the possibility of emergence and expansion of micro-crack, Chamfering should be under high temperature unilaterally and progressively, and each reduction ratio should be less than 10 percent. The results of simulation are supported by experiments.Combined with research results of numerical simulation, developed theories and technologies of forging process are applied to reexamine and revalue the existing forging process of rotors of steam turbines hi light of systematology. Some problems are uncovered and new process design criteria and process sequence are presented. Compared with the current process, the new process excludes once JTS after which upsetting could be deleted. The weakening effects on consolidation put by successive upsetting procedure are avoided. Replacing WHF method, LZ forging method and new FM method assure that there is not two-direction tense during every sequence. In addition, controlling thermal mechanical parameters eliminates mixed crystal during forging. As a result, the new process is of explicit purpose, marked forging stages and global process parameters optimization.Experience of domain experts in process design and results of numerical simulation are extracted into process rules to establish a knowledge base. A process design expert system is developed on Windows platform with the object-oriented Delphi language. The system contains the newest theories and technologies of forging process and owns the function of automatic process design and check against rationality of traditional process. The developing model of forging CAPP expert system is created and object-oriented technology is applied to system analysis. The method of forging feature modeling and feature-based forging process design is researched. Integrated deduction method is produced of case-based concept design and rule-based detailed design. Technologies are discussed including the drawing of CAPP process chart, the management of process database & knowledge base and the filling, editing and modification of database-based process cards.Applying comprehensively with theories of forging process, technologies of numerical simulation, artificial intelligence expert system, CBR, object oriented, feature and database, the forging CAPP system is enabled to be advanced, applicable to guide design and to serve enterprises.The research is significant to guide how to improve the forging process design of rotors and forging quality generally.