Research On Hot Drawing Laws And Process Of Water Chamber Head

As a solid forging,the water chamber head of type AP1000 steam generator is one of the high difficultly manufacturing large forgings of nuclear components with the huge blank size,complicated shape structure and high performance requirement.For the whole forging problem of the water chamber head,a new technology of hot drawing forging process using hydraulic press is proposed in this paper,and the deformation process and forging law are studied by finite element numerical analysis and experiment.To study the hot drawing forging process,the othermal constant strain rate compression experiment of SA508-3 steel is carried out using thermo-simulator system Gleeble-3800,and its high temperature flow stress-strain curves and hot forming parameters are tested under the condition of strain rate range of 0.001s-1~0.1s-1 and deformation temperature range of 950℃~1250℃.Then the hot working constitutive model is established and the forging temperature of the water chamber head is determined.A comparative study of the three kinds of forging process scheme which are drawing-nozzle orifice flanging,drawing with nozzle without orifice and drawing with nozzle and support platform is carried out by simulation experiments.Then the pre-forging blank with nozzle orifice and support platform is selected,and a new hot drawing process of the water chamber head by using hydraulic press including technological process and die design are proposed.To study the influence of number and distribution of nozzles,the hot drawing of preformed blanks with four support platforms are conducted by commerical finite element software Forge,which inculding double nozzles biaxial symmetry,three nozzles biaxial symmetry,and double nozzles axisymmetric central symmetry and double nozzles axisymmetric side distribution.The change rule of geometric shape and size,internal deformation temperature and the distribution of stress and strain in the hot drawing process are analyzed,which reveals the deformation characteristics of the nozzles,the deformation principle of thickness,and the deep drawing load curve are obtained.The results show that the deformation of the water chamber head is related to the number and distribution of the nozzles,and the deformation characteristics are obviously non-uniform.It is clearly that the thickness of the forging blank is thinning in the center area,while thickening at the edge area.In the process of hot drawing,the straight-line generator of the nozzles turned into curved,the nozzles in the center of the water chamber head almost keeps unchanged,while the others become ellipses,and their center occurs an offset.The double nozzles single axisymmetric side distributed water chamber head used for nuclear power EPR evaporator is selected as the research object,a physical simulation experiment was conducted,the scale of the experiment is 1:1.5 and the material of the head is aluminium alloy.The experimental samples were tested using scanner FOCUS 3Dx330,the corresponding scan images and point clouds data are obtained.The test results show that the thickness values at the main feature points of the forging are in good agreement with numerical simulation results,which verifies the feasibility of the proposed hot drawing process.