| Rotor can is one of the key components in AP1000reactor coolant pump. Its manufacturing precision and assembling quality have an important influence on the normal running of reactor coolant pump. Rotor can is made of Hastelloy C-276thin sheet by cutting and welding. Because AP1000reactor coolant pump rotor can is a super thin cylindrical workpiece with a large length to diameter ratio and diameter to thickness ratio, and its diameter deviation before shrink fitting is±0.076mm, it is very difficult to achieve the manufacturing and assembling of rotor can. On one hand, vacuum hot bulge forming technique was proposed to control the dimension error of rotor can after cutting and welding and make rotor can meet the dimensional precision requirement before shrink fitting. On the other hand, a temperature controlling method for the shrink fitting of reactor coolant pump rotor can was proposed to slow down the decreasing rate of temperature of rotor can during the shrink fitting process properly. Then, the permissible shrink fitting time of rotor can was expanded, which prevents rotor can and rotor from contacting with each other prematurely and make sure the shrink fitting of rotor can can be accomplished successfully.In the dissertation, finite element simulations and experiments were adopted. The finite element software MSC.Marc was utilized to simulate the vacuum hot bulge forming process and the shrink fitting process of reactor coolant pump rotor can. The vacuum hot bulge forming mechanism of rotor can, the vacuum hot bulge forming law of rotor can and the effects of process parameters on the shrink fitting of rotor can were analyzed in depth. The die for the vacuum hot bulge forming of rotor can and the shrink fitting experimental platform of rotor can were designed and manufactured. Then, the vacuum hot bulge forming and shrink fitting experiments were carried out. These works lay a good theoretical foundation and provide necessary data for the dimension error controlling after cutting and welding and the shrink fitting of rotor can. The main research contents and conclusions are as follows:1. A creep constitutive model of Hastelloy C-276was developed based on the stress relaxation experiments. The finite element software MSC.Marc and its subroutine were used to simulate the vacuum hot bulge forming process of reactor coolant pump rotor can. The transient temperature field, redius-direction displacement field and stress-strain field in rotor can and die were calculated. The vacuum hot bulge forming mechanism of rotor can was analyzed in depth. The bulging dimension of rotor can after vacuum hot bulge forming were predicted. 2. On the basis of the developed finite element model of vacuum hot bulge forming of reactor coolant pump rotor can, the effect of wall thickness of die, holding time, holding temperature and bulging clearance between rotor can and die on the bulging dimension of rotor can were studied, and the optimal process parameters were obtained. The simulated results show that the effect of wall thickness of die can be neglected and the optimal wall thickness of die is20.00mm. When holding time and holding temperature are increased, the bulging dimension of rotor can is increased. The suggested holding time is2h-3h and the holding temperature should be in the range from750℃to800℃The bulging dimension of rotor can and the bulging clearance are in near linear correlation and the optimal bulging clearance ranges from0.20mm to0.60mm.3. The die for the vacuum hot bulge forming of rotor can were designed and manufactured and the vacuum hot bulge forming experiments were carried out. The compared results show that the simulated values of the bulging dimension of rotor can agree well with the experimental ones, which verifies the accuracy of the simulated results. In addition, the error of the internal diameter of rotor can between the experimental data and the required value is in the range from-0.04mm to+0.06mm and smaller than±0.076mm, which indicates that the vacuum hot bulge forming technique can be used to control the dimension error of rotor can after cutting and welding precisely and make rotor can meet the high precision requirement before shrink fitting.4. The self-developed steady-state contact heat transfer and transient heat transfer experimental apparatuses were utilized to study the heat transfer behaviours during the shrink fitting process of rotor can. The steady-state thermal contact conductance between Hastelloy C-276and Hastelloy C-276and the transient thermal conductance between Hastelloy C-276/narrow air gap/silicon steel were measured. The effects of interfacial pressure, interfacial temperature, initial temperature of specimen and gap size between specimens were studied which provides necessary data for the finite element simulation of the shrink fitting process of rotor can.5. On the basis of finite element software MSC.Marc, the shrink fitting process of reactor coolant pump rotor can was simulated by programming the heat transfer subroutine. The transient redius-direction shrinkage of rotor can during the shrink fitting process was calculated and the shrink fitting time of rotor can was predicted. In addition, the effects of manufacturing precision of rotor can, shrink fitting temperature and wall thickness of thermal insulation layer on the shrink fitting of rotor can were also studied. The optimal wall thickness of thermal insulation layer is1.00mm-2.00mm.6. A set of shrink fitting experimental platform of reactor coolant pump rotor can was designed and manufactured and the corresponding shrink fitting experiments were carried out. The experimental results indicate that the permissible shrink fitting time of rotor can is expanded effectively by the proposed temperature controlling method for the shrink fitting of reactor coolant pump rotor can. When the wall thickness of thermal insulation layer is1.50mm, the permissible shrink fitting time of rotor can is37s, which reduces the shrink fitting difficulty greatly and can improve the success ratio of the shrink fitting of rotor can. |
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