Research On Numerical Model And Deformation Discipline Of Large Diameter Thickness Ratio Disc By Multi Roll Rotary Forging

Rotary forging is an innovative incremental metal forming process,it has many advantages such as high precision,saving materials,low noise.Large-diameter disc parts are key components in nuclear power,petrochemical,coal liquefaction,aerospace,deep-sea exploration and other fields,the nuclear reactor pressure vessel and high-pressure container end plate and head need more than 8 m diameter of the whole disc piece(The diameter/thickness value is more than 100).At present,the forming process of large-diameter disc mainly includes welding and multiple local upsetting of the plate,the disadvantages of these processes are large machining allowance,large tool loss,large hammer impact force and large thickness error of forgings.However,the traditional rotary forging is mainly used to form small and medium-sized parts with a diameter less than 600 mm and large parts can not be formed integrally.Therefore,a new metal plastic forming technology,namely rotary forging with multi-cone rolls(MCRs)is studied to integrally form large-diameter and ultra-thin discs.Rotary forging with MCRs is a rotary forging technology with odd number of rolls and more than 3.Due to the size and distribution of cone roll,the machine body area is effectively reduced and the actual utilization ratio of cone roll is increased,which can be used for forming large-size disc and ring parts.In this paper,two finite element models of 90° coaxial rotary forging with MCRs and non-coaxial rotary forging with MCRs are established by scale simulation of 10 m disc parts.Based on the reliable three-dimensional rigid plastic finite element model,the law of plastic deformation is studied,and it is concluded that the rotary forging with MCRs also is the forming process of gradual infiltration of plastic deformation area as the traditional rotary forging.The axial plastic deformation of 90° coaxial rotary forging with MCRs is similar to that of single roll and double roll rotary forging.There is an unstable stage of axial plastic deformation of multi-cone roller with different axes when the initial diameter of the billet is small,while the axial plastic deformation is similar to that of single roll and double roll rotary forging when the diameter is large.At the same time,the law of metal flow at the step,the stress state of the edge of the workpiece and the influence of different shrinkage ratio on the forming are studied.By adjusting the process parameters,a large number of simulation calculations are carried out,and the influence rules of each process parameter on the forming process,the defects in the deformation process and the force and energy parameters are obtained,it is concluded that the adjustment of process parameters(Feed rate,initial blank temperature,bottom step,roll distance,friction coefficient)can effectively reduce the warpage,center thinning or thickening,flying chip,folding and other defects in the forming,and can also effectively reduce the degree of non-uniform deformation,maximum load and damage.Grooves were made on the original 500 T twin-roll rolling equipment,and the shrinkage forming test of multi-roll rotary forging disc was carried out.By adjusting the process parameters,the metal disc rotary forging parts were obtained,and the finite model and relevant conclusions were verified.The research results are helpful to better understand the metal plastic forming technology of rotary forging with MCRs and provide a reliable forming process for producing large-diameter thin disc parts.