Wide-spread Law Of The Large Axial-diameter Ratio Workpiece In Roll Forging Process

The length of a certain type of epee sword is 1100mm,the equivalent diameter of the maximum cross section is 14mm,the equivalent diameter of the minimum cross section is 6.2mm,and the axial-diameter ratio is as high as 177.It is an atypical large axial-diameter ratio variable section asymmetric workpiece,which is not suitable for producting by turning and other processing methods.The traditional production mode of free forging combined with manual grinding no longer meets the market development.The automatic and semi-automatic production is expected to be realized by using roll forging and die forging.In roll forging drawing process,the transverse width of the forging metal brings challenges to the drawing efficiency and precision control.Tarnovsky wide-spread model is often used in the design of roll forging die.The existing wide-spread model cannot provide wide-spread coefficient for the design of roll forging die with large-axial ratio workpiece.In this thesis,an experimental study on flat forging of large axial-diameter ratio forgings was carried out on a roll forging machine,and the width spread and elongation coefficient of the workpiece with large axial-diameter ratio were obtained.The influences of billet aspect ratio,reduction rate and initial height on the width spread coefficient were analyzed.The experimental results extended the application range of Tarnovsky wide spread model,and a 14-pass roll forging die for the model epee sword was designed.A rigid-plastic thermo-mechanical coupling finite element model for roll forging process of 60Si₂Mn spring steel with large axial-diameter was established on commercial finite element software,and the fifth roll forging process was simulated.The flow law of metal in deformation area during roll forging was analyzed by stress analysis and strain analysis method.The results show that the width of the forging is basically consistent with the budget width based on Tarnovsky’s width model.The width of the forging in the roll forging process with large axial-diameter is mainly derived from the compression deformation in the direction of the height of the forging in the main deformation area.The wide-spread gradually increases from the center of the forging width to the free wide-spread edge.There exists a tensile deformation region in the direction of roll forging between the front and back rigid ends and the main deformation region,and the tensile deformation in this region is conducive to reducing the wide-spread during roll forging.In order to reduce the transverse flow of the metal in the deformation area to form a wide-spread,tension is applied to the inlet or outlet side of the forging.The simulation results show that the influence range of the tensile deformation area on the inlet side increases significantly and the influence range of the tensile deformation area on the outlet side Narrows,which is conducive to reducing the wide-spread.Only adding unidirectional tension at the outlet side decreases the width of compressive deformation zone at the rear rigid end.The extension area of the entrance side was further expanded by adding tension on both sides simultaneously.The research results can be used to guide the roll forging process and die design of large axial diameter ratio workpiece.In order to reduce the transverse flow of the metal in the deformation area to form a wide-spread,tension is applied to the inlet or outlet side of the forging.The simulation results show that the influence range of the tensile deformation area on the inlet side increases significantly and the influence range of the tensile deformation area on the outlet side Narrows,which is conducive to reducing the wide-spread.Only adding unidirectional tension at the outlet side decreases the width of compressive deformation zone at the rear rigid end.The extension area of the entrance side was further expanded by adding tension on both sides simultaneously.The research results can be used to guide the roll forging process and die design of large axial-diameter ratio workpiece.