Research On Hot Deformation Behaviors And Manufacturing Technology For GH690 Alloy Divider Plate

GH690 alloy is a nickel-based high-temperature alloy with a chromium content of about 30%.At present,the alloy has been widely used to manofacture heat transfer pipe,divider plate and other parts of nuclear power steam generator,and contacted with primary coolant due to its excellent anti-intergranuler corrosion,anti-stress corrosion performance,high strengthen and creep resistance.GH690 alloy contains a large number of alloying elements,and its microstructure is complex,which makes it difficult to control the heat treatment process.Hence,the alloy has great deformation resistance at high temperature and poor plasticity,the cracking occurs easily in the forging process,the temperature range of hot forming is narrow and difficult to control.Moreover,the alloy is a sigle austenitic structure without solide phase transition,and the thermal deformation process is required to be more strict.Therefore,it is necessary to study the microstructure and properties of GH690 alloy during thermal defomation and solution treatment.In this paper,the constitutive model and the dynamic recrystallization model of the alloy in high temperature deformation were obtained through the hot compression test,the forging process of the divider plate was developed,and the main forging processes were simulated and analyzed,the microstructure evolution of GH690 alloy in the process of solution treatment was studied.By studying the thermal deformation behavior of GH690 alloy,friction correction was used to eliminate the error caused by friction force in the thermal compression test,the true stress-strain curve during the hot compression process of the alloy was obtained,the Arrhenius constitutive equation based on Z parameter was established,and its thermal deformation activation energy Q=775290.8946 J·mol^-1 was obtained.The microstructure evolution of the alloy was analyzed,and the Sellars power exponential grain growth model and Kopp dynamic recrystallization volume fraction model were established.The forming process of GH690 alloy divider plate was developed,and the finite element model of divider plate forging process was established.The thermodynamic coupling simulation of the forging process was conducted,and the distribution of strain field,temperature field and the change trend of forming load in the process of GH690 alloy forging were obtained.Through the analysis and simulation results,the forming rules of the divider plate in the forging process were obtained,which provided technical support for the forging production of GH690 alloy slab.The changing rule of grain size,carbides and hardness of GH690 alloy under different solution treatment conditions were obtained.In the process of solution treatment,it was found that the effect of solid solution temperature on the microstructure of the material was more significant than that of solution time.When the solution temperature in 950??1100?,the grain growth is slow,when the temperature is above 1100?,the grain growth speed obviously improved,when the temperature is 1200?,the average microscopic level of grain size is about 3.0.When the solution temperature in 950??1050?,the carbides in the alloys have decreased significantly,when the solution temperature above 1150?,the carbide in the material base could be dissolveed completely.When solution temperature in 950??1000?,the hardness of alloy reduce rapidly,the hardness of alloy reduce slowly after 1000?.