| Development of nuclear power is the inevitable choice to achieve optimization of the energy structure and realize energy-conservation and emission reduction target.Steam generator is the key equipment for heat exchange and transfer between nuclear island primary and secondary circuit of Pressurized-water reactor nuclear power plant.And inside it,primary head,being the primary circuit pressure boundary,is the most critical part with the highest difficulties in manufacture,due to the complicated structure.Welding and heat treatment are the difficult and important technique in manufacture of primary head for the third generation nuclear technology-AP1000,this thesis is focused on research of the typical problems,as to guarantee the manufacture quality of our product meet the design requirements,which is very much meaningful to improve equipment stability and ensure the safety of nuclear power plant operation.By means of welding procedure test which was initiated with various technology parameters,this thesis researched on relationship between heat input and mechanical property of deposited metal for Inconel 52 M welding wire.The main conclusion were as follows:1)When heat input is in the range of 1.0kJ/mm-2.5kJ/mm,room temperature and 350? tensile strength of deposited metal for Inconel 52 M welding wire is significantly reduced with the increase of heat input,while increase of heat input has little effect on tensile strength when heat input is no less than 2.5kJ/mm;2)Heat input should be controlled within 1.6kJ/mm to make sure that mechanical properties of deposited metal of Inconel 52 M welding wire satisfy the designed requirement.Based on the test results,welding parameters of welding procedure was adjusted.And as a result,inspecting of welding materials and welding procedure qualification had successfully accomplished.The problem of mechanical property of deposited metal of Inconel 52 M welding wire of diameter ?1.2mm's failing to meet the designed requirements was successfully solved.By means of stress relief heat treatment test which was initiated with different heat-holding time,this thesis analyzed the influence of various heat treatment on hardness,metallographic structure and ferrite content in stainless steel cladding.The main conclusions were as follows:1)After stress relief heat treatment,hardness value declined slightly then tends to be stable;2)Ferrite in stainless steel cladding decomposed during stress relief heat treatment,in a certain period of time,the longer the heat-holding time,the greater the amount of ferrite decomposed;As the heat holding time reached 6~8 hours,ferrite stopped decomposing and became stable,even heat-holding time was extended to 20 hours in simulated heat treatment,stainless steel cladding still have good resistance to intergranular corrosion.Based on the test results,requirement prescribed by the designe party that heat-holding time of at least 12 hours in stress relief heat treatment of primary head stainless steel cladding is justified feasible,the heat treatment technology can be used for real product,the doubt of heat-holding time in the early stage of manufacturre was eliminated.Quality is the lifeline of nuclear industry.The entire manufacturing process of primary head in AP1000 steam generator,from materials control,quality control of forging process and heat treatment process in forging work to adjustment of the parameters and quality control in welding procedure and heat treatment procedure in manufacturer,is running under the quality monitoring system.Base on the quality control approach and results expounded in this thesis,the quality of primary head is proven to be under controlled,and what's more,the domestic manufacturing ability of AP1000 primary head has risen to a relatively high level. |
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