Free Forging Method Analysis And Forming Technology Research Of Large Blind Hole And Semi Blind Hole Forgings

As an important part of heavy equipment,large forgings are widely used in chemical industry,electric power,metallurgy,shipbuilding,aerospace and other fields.As an important part of large forgings,large hollow forgings have the advantages of material saving and light weight,which are widely used in transportation pipelines,transmission shafts,pressure vessels,etc.As a common structure of large hollow forgings,blind hole and semi blind hole parts have good application prospects and unique structural advantages.However,at present,the research on free forging technology is not systematic and perfect,and there are still problems such as experience-based operation,research is not systematic,lack of data visualization,etc.With the rapid development of computer software and hardware and the maturity of metal plastic forming theory,computer-aided engineering technology based on numerical simulation has been widely used in the field of metal bulk forming,and gradually become the mainstream of the industry.In this thesis,the common large-scale hollow forging is taken as the research object.According to the structural characteristics of the inner hole,it is divided into through-hole forging,blind hole forging and semi blind hole forging.On this basis,the free forging method and forming process of large-scale blind hole and semi blind hole forging are studied.First,according to the ratio of inner hole depth and inner diameter(H/D),the blind hole parts are divided into deep blind hole forgings and shallow blind hole forgings,the semi blind hole parts are also divided into deep semi blind hole forgings and shallow semi blind hole forgings.After analyzing the forming characteristics,tooling structure,advantages and disadvantages of the forming methods of blind hole and semi blind hole parts,a reasonable free forging forming method is found for each kind of forging,which provides the basis for the subsequent forging process of large blind hole and semi blind hole parts.For large forgings with deep blind holes,the punching and drawing method is adopted.In this thesis,two kinds of typical forgings,the equal diameter cylinder forgings and the variable(inner)outer diameter forgings,are selected as the research objects.By means of numerical simulation and partial scale experiment,the important technological parameters in the process,such as the rotation angle,the reduction,the size of the stacking anvil area,the anvil type,the anvil angle and the blank shape,are compared with each other.The forming results are analyzed from the aspects of forming surface quality,strain distribution,forming force,size control,and the reasonable forming parameters are obtained.The numerical simulation of the whole process of the process of the equal diameter forgings is carried out,and the corresponding lead scale experiment is designed to verify.Based on the drawing process of the equal diameter forgings,the structural characteristics of the more complex variable(inner)outer diameter forgings are analyzed.The influences of different forming upsetting dies,different drawing anvils and different drawing sequences on the forming quality are studied.Finally,the punching and drawing process of 446W6181 blind hole wind power spindle is proposed and verified by simulation.Both forgings are well formed,which proves the accuracy of free forging and drawing process parameters and the feasibility of process flow.For the semi blind hole forgings,the forming methods of expanding the hole with variable diameter mandrel and closing the hole using variable diameter mandrel are adopted.The traditional expanding method of saddle forging is improved,and the forming method of symmetrical variable diameter mandrel saddle forging which is sulitable for shallow semi blind hole forging is put forward.The forming method of"one billet into two pieces" can be realized by adopting the this method along with gas cutting,the method can also be used to directly form semi blind hole parts with inner flange structure in the middle of inner hole.For deep semi blind hole forging,the forming method of mandrel drawing and matching with variable diamete mandrel hole-collecting can significantly reduce the machining allowance and better retain the forging streamline.The process of hole expanding and hole closing can be regarded as the superposition of single-step down deformation.Therefore,based on the analysis of single-step down deformation area,the typical forging structure is selected,and the important forming process parameters such as reduction,rotation angle,billet making scheme,flange width,mandrel transition structure,etc.in the two forming processes are compared and simulated,and the final forming process is explored,then the reasonable parameter range is given.The scale experiment scheme of hole-collecting method is designed,and some important process parameters and the whole process are studied.The accuracy of simulation results is verified by comparing with simulation results.For large blind hole forgings with relatively small size,the method of die forging is adopted.The backward extruding and punching processes of the die for the large shallow blind hole forging and the large deep blind hole forging are developed respectively.Taking GP425993 R1 shallow blind hole part as the research object,after analyzing the factors such as material flow and die structure,the defects such as insufficient filling and excessive forming force that are easy to appear in the process are put forward,such solutions as up convex down flat upsetting billet,combined punch and large and large-small punches alternatively press are put forward,which effectively improves the process feasibility.In this thesis,the forming technology of die forging and punching for deep blind hole forging is explored.The billet-making scheme,die structure and process flow of die forging for 446W6181 spindle are designed,and the feasibility of forming large and medium-sized deep blind hole parts by die forging and punching is clarified.