Research On Internal Pressure Expansion Forming Technology And Equipment Design Of Large Head

The head is the main pressure part of the pressure vessel,and is widely used in large-scale hydrogenation reaction equipment,coal liquefaction reaction equipment and nuclear reactor shells.The traditional head processing process is prone to defects such as cracking and local thinning,and the existing forging equipment can not meet the technical requirements for manufacturing the super-large diameter head,and the internal pressure bulging technology can ensure the surface quality of the head is good,the wall thickness is uniform,and the equipment requirements are low.so it is one of the few options to make a super-large diameter head.In this paper,referencing the technical idea of continuous casting and rolling of steel plate,according to the prin,ciple of equal volume deformation,a Q235 head blank with a slightly convex center is first cast in the metal mould,The outer diameter is 300mm larger than the.final head diameter,When the blank is cooled to about 900?,the blank is transferred to the internal pressure bulging mould for forwar,d stretching and reverse stretching,and the workpiece is deformed by the tension of the material and the high-pressure energy balance of the internal fluid medium.When the final size of the head is formed,the deformation rate of the head in the thickness direction is equivalent to the rolling deformation rate of the corresponding steel sheet.In this paper,the internal pressure bulging process of the head is studied and the design of related equipment has been completed.The specific research contents and results are as follows:(1)The changes and distribution of stress and strain of the head during different forming processes were studied.using the finite element software ABAQUS to simulate the forward and reverse internal pressure bulging stretch forming process of the head,the single internal pressure bulging stretch forming process and the traditional stamping forming process,and obtaining the change of stress and strain during the deformation process of the head.The results show that almost all inner surfaces and fillet radii are subjected to the maximum equivalent stress during the bulging deformation process of the forward and reverse internal pressure,and the equivalent stress distribution is more uniform than that of the single internal pressure bulging deformation process.Compared with the stamping formin,g process,due to the uniform force of the blank,the head obtained by the internal pressure bulging has no wrinkles and severe tensile deformation at the corner radius.(2)The effect of the number of bulging times on the grain size of the head was studied.The grain shape simulation was carried out on the workpieces with single stretch bulging and forward and reverse stretch bulging of the head,and obtaining the average grain size and dimensional change of the final formed head.The results show that compared with the single bulging tensile results,the grain distribution formed by the forward and reverse tensile bulging is more uniform,the grain size is smaller,and the minimum average grain size is 0.334 ?m.(3)The effect of different radius of the mould radius on the quality of the head was studied.The numerical simulation results show that when the radius of the mould fillet is too small,the local stress and strain are concentrated and sharply increased,and the equivalent stress distribution is uneven.When the radius of the mould fillet is too large,the equivalent stress is evenly distributed,but the maximum equivalent strain value of the whole blank is gradually reduced,which is not conducive to the tensile expansion type.It is most suitable to select 300mm of the corner radius of the mould.(4)According to the characteristics of the large hemispherical head internal pressure bulging process and the simulation results,designing a corresponding plastic forming device of internal pressure bulging process,and the strength and fatigue analysis of the parts subjected to internal pressure were carried out.The results show that the device meets the requirements for use;At the same the,the variation of the torque of the structure during the rotation and the vibration occurred during the whole rotation were analyzed and studied,It can provide reference for design selection of subsequent drive devices.Through the summary of the simulation results of the internal bulging process of the large head,the feasibility of the internal pressure expansion forming technology is verified,which has a certain guiding effect on the production of the actual large head.