Study On Roll Extrusion Technology For Long Conical High Strength Steel Shells

Terminal sensitive projectile has become a typical representative of modern intelligent weapon ammunition,because it has the characteristics of traditional ammunition and missile technology.The blank of the projectile body is a typical long conical deep blind hole shell component.Because the long conical warhead cannot be extended,it can only be processed by traditional hot stamping cup forming,with large wall thickness difference and material utilization rate of less than 40%.This makes the design technical indicators forced to give way and restricts the development of new ammunition.In order to meet the requirements of strong protection,lightweight,high reliability and low cost of weapons and equipment in the future war,this paper focuses on the roll extrusion precision forming technology of50 Si Mn VB high strength steel projectile body blank.The hot stamping process was optimized by grasping the high temperature rheological behavior of 50 Si Mn VB high strength steel,establishing hot working diagram and finite element numerical simulation;According to the structural characteristics of shell blank,the roll extrusion precise control forming process and device of long conical cylinder are designed.The mechanical analytical model is established,the die and process parameters are optimized through finite element simulation,and the reliability of roll extrusion device is verified,which provides theoretical support for the application of roll extrusion technology of long conical high-strength steel shell.The main research contents are as follows:1.The accuracy of the existing J-C constitutive equation is verified by studying the high temperature rheological behavior of 50 Si Mn VB high strength steel.The hot working drawing is established,and the optimal forming parameter range is obtained through the hot working drawing.The process parameters of hot stamping are optimized by finite element simulation.The optimum hot stamping process parameters of 50 Si Mn VB high strength steel thick wall deep blind hole cylinder blank are obtained as follows: Temperature: 1150 ° C;Speed: 60mm/ S;Friction coefficient 0.2.2.The mechanical model of roll extrusion of conical part is established through the relevant theory of plastic forming.The conditions for stable operation of roll extrusion are obtained.The flow law of metal is analyzed,and the calculation formulas of forward slip angle and backward slip angle are deduced.Finally,the calculation formula of roll extrusion force is obtained,which provides a theoretical basis for the formulation of precise control forming process and the design of roll group.3.The roller structure with outer spiral groove is designed,and the design criteria of main structural parameters of special-shaped groove roller are obtained.The roller group model and forming process of roll extrusion are optimized through numerical simulation,and the load in the precise forming process of long conical shell by roll extrusion is analyzed.The results show that the flash can be effectively reduced by optimizing the wheel group structure from single row of rollers to multiple rows of rollers and reducing the roller radius from173 mm to 100 mm.At the same time,the optimized roll extrusion process also avoids the problem that the wheel groove edge contacts the blank first,resulting in the inability of accurate forming.The maximum load of the optimized roll extrusion process is only 1290 KN in the conical part and 330 KN in the straight wall part.Compared with the traditional process,the precise control forming process of roll extrusion can greatly reduce the forming load and obtain the workpiece meeting the dimensional requirements.The blank entry angle(width)of special-shaped groove roller is optimized through numerical simulation,and the optimal blank entry angle is 110 °.4.The structural characteristics of the functions required by the roll extrusion precise control forming process are analyzed according to the designed roll group structure.The supporting device design has been completed,including overall design,roll extrusion mechanism design,reset mechanism design,discharging device design,etc.The static finite element analysis of the designed roll extrusion device is carried out by ANSYS Workbench.It is concluded that the maximum stress in the roll extrusion process is 67.1MPa and the maximum displacement is 0.01004 mm,which verifies the reliability of the device.