Research On Rolling-Extrusion And Drawing Technology Of The Large Caliber Projectiles

The production of shells is one of the largest groups of products in militaryproduction.Shells have the largest consumption in the war as the main body of conventionalweapons. The large caliber projectile blank is typical variable wallthickness ofcylinder components. The traditional mode of producing is "stamping-stretch" to form thestraight wall cylinder components, and then cut out different wall thickness, using the methodof machining. This method leads to low material utilization ratio, long processing time, largecutting tool consumption, and high cost. In this paper, in order to solve these quetions, therolling-extrusion and drawing technology is put forward to make the parts with plasticforming methods, with less cutting or no cutting, which not only can greatly improve thematerial utilization and production efficiency, also can make the reasonable distribution ofmetal flow along the contour and improve the mechanical properties of the parts.50SiMnVB alloy steel was analyzed in this paper by means of isothermal compression,optical microscopy, scanning electron microscopy, hardness testing. The deformation behaviorof the alloy steel with different deformation parameters was systematically studied, and theJ-C constitutive model of the alloy steel under the different stress states was established.Based on the dynamic material model, the steel’s two-dimension processing map was created,which showed that the alloy stell has three peak energy dissipation areas:(I)650～750℃，0.01s1(II)800～900℃，0.001s1，(Ⅲ)1050～1150℃，0.01s1～0.1s1.According to theactual production situation，the best choice of process parameters was within temperature1050~1150℃and strain rate0.01~0.1.This provides the reference for choosing theforming parameters.In the study of the principle of the rolling-extrusion and drawing, firstly, the end biteconditions of the workpiece were analyzed, and the formula of limit bite angle and thestability rolling-extrusion conditions were deduced; Secondly, the impact on the biting condition of friction coefficient was analyzed, and the approximate formula of the coefficientof friction was got; the analysis of the metal flow law in the process of rolling-extrusion wasdone. A research is focused on the forward slip and the formula was deduced, according to thecharacters of the shape of the roll grooves. At last, A calculation formula of rolling-extrusionforce was given.The roll grooves were designed based on the principle of precise control on parts size, andthe design criterias of main structure parameters of the rollers were made. According to theresults of finite element numerical simulation, the optimization experiment on roller structureparameters was worked out; using the method of central composite design, and the regressionmodel was established. By response surface analysis and comprehensive evaluation based onthe weighted desire function factor, the optimal roller structure parameters were obtained: theaxis distance189.7475, the apex angle of flash gutter29.9495, the roller width130.1515. Onthis basis, the rolling-extrusion and drawing equipment was designed and manufactured.What’more, and the transformation of the original production line was finished.Through the finite element numerical simulation, analysis of the process parameters onthe distribution uniformity of the field variables was done. The design variables were selected,with impact assessment on the workpiece deformation uniformity as a reference, and theselection of objective function was done with a combined way of shape controland performance control. The experimental scheme of each factor under different level wasdesigned by using the method of BBD, and the three objective function distribution of weightwere got, through the application of response surface method on the analytical hierarchyprocess. The results of grey correlation degrees analysis showed the optimal combination ofprocess: T950C, V32mm/s，0.2.Experiments were carried out to verify the feasibility of the rolling-extrusion and drawingprocess and the correctness of the optimization of process parameters. The results showed thatas compared with the traditional process, the rolling-extrusion process can make the materialutilization rate of projectile blanks be improved9.8%, and make the production efficiency be improved by more than double, along with reducing of the overall production cost, saving ofenergy and reducing consumption, which meet the expected research goal, and powerfullysupported the application of the rolling-extrusion technology.