30CrMnSiA Large-diameter Cylindrical Parts Counter-wheel Spinning Technology Research

As science and technology developed,aerospace technology has gradually become a symbol of a country’s national strength.In 2015 China proposed the "Made in China 2025",pointing out that more efforts will be focused on the research of large launch vehicle and heavy lift launch vehicle to improve the ability to enter space.As an important component of large and heave launch vehicle engine shell,the large diameter cylinders are usually formed by the "counter-roller spinning" technology,which can be used to produce any cylinders within a certain range.So it can save a series of similar size molds costs and enhance the flexible manufacturing level.At present,the "counter-roller forming" technology has been successfully applied in the aerospace field.For example,the manufacture of booster shell of European “Ariane 5” rocket and the manufacturing of shell of American Ares rocket solid rocket motor both have adopted this technology.Domestic research on "counter-roller spinning" technology is mostly about light alloy or small-diameter cylindrical parts,but there is few research on "counter-roller spinning" technology of steel cylinder with large diameter and high strength.Therefore,it is of great significance to carry out numerical simulation and technological test of large-diameter and high-strength steel cylinder for the development of large launch vehicle in China.Firstly,this paper discussed the property of high-strength steel 30CrMnSiA materials,analyzed the effects of different heat treatment methods on microstructure and mechanical properties of 30CrMnSiAthrough heat treatment experiments.And based on the the conclusion of heat treatment,spinning test of cylindrical parts under different heat treatment conditions is launched.In conclusion,under isothermal spheroidizing the mechanical property and rotationally of 30CrMnSiA are the best.Therefore,in this paper isothermal spheroidizing is appied for the cylinders to carry out the follow-up test of "counter-roller spinning".Then based on the finite element software Abaqus,a finite element original scale model of the 30CrMnSiA large-diameter cylinders to counter-roller spinning is established.The cylinder is rotating,and the four pairs of inner and outer rollers are used for axial feed motion.Meanwhile the wall thickness is thinned by the friction force between the parts and the rollers.The model is meshed by the explicit linear 3D Stress hexahedral element C3D8 R to the numerical simulation of the counter-roller forming process of the 30CrMnSiA cylindrical part.And the simulation reveals the stress-strain distribution of the counter-roller spinning process which shows the primary and secondary order of the influence of the spinning parameters on the roundness error are: roller fillet radius > thinning rate > feed ratio > forming angle,the primary and secondary influences of spinning parameters on wall thickness deviation are: feed ratio > forming angle > roller fillet radius > thinning rate.A set of optimal process parameters are roller fillet radius 12 mm,forming angle 25°,feed ratio 0.9mm/r,and thinning rate 25%.It provides a reference for the selection of parameters for the spinning test.Combined with the results of numerical simulation,a BP neural network model with process parameters as input and forming precision as output is established.With the simulation results as sample to train the neural network,the prediction model of process parameters,including feed ratio,thinning rate,round radius of the wheel,forming angle,for forming quality are obtained.It realizes the prediction of roundness error and wall thickness deviation.Moreover,the error between predicted and simulated results is not more than 2.6%.Finally,the counter-roller spinning test of 30CrMnSiA large diameter cylindrical parts is carried out.Firstly,this paper develops the the structure design of the counter-roller blank and manufacture of blank.Then,the counter-roller forming process test of 30CrMnSiA large diameter cylinders is carried out to verify the influence of process parameters on the forming quality.And the optimal process parameters selected by numerical simulation are used as the test parameters to realize the spinning process.The wall thickness of 30CrMnSiA cylinder with diameter of 2m decreases from 30 mm to 13.5mm.The deviation of wall thickness is 0.025 mm in the first pass,which meets the requirement of spinning accuracy.