Relationship of the method of obtaining the original billet with the accuracy of manufacturing of the extended axisymmetric bodies

Abstract

A comparative description of the technology for producing blanks for the artillery shell cases or the rocket shell bodies using flat rolled stock or rolled tubular products is given. It is noted that the lower cost of flat rolled stock leads to its wider application for stamping blanks of cartridge caps or bodies, including cutting a circle from flat rolled stock, convolution and several transitions of drawing, alternating with heat treatment. It is noted that the disadvantage of this technology are the errors in the shape of the blanks, amounting to 0.75÷1.5 of the tolerance for diametrical dimensions. When machining, these errors decrease according to the laws of copying the errors, however, the anisotropy of the material of the part blank leads to the appearance of errors in the shape-ovality and curvature of the pipe, which lead to the formation of a large radial runout of the prefabricated rocket body. It has been found that the scattering fields of all output quality parameters exceed the existing tolerances: radial runout of the assembled body by 1.3 times; ovality of the middle centering bulge by 2.15 times. It is shown that the technological process of manufacturing prefabricated housings using initial blanks from flat rolled stock does not provide the required precision technology reliability. For the manufacture of monolithic extended axisymmetric bodies, hot-rolled thickwalled pipes are used as an initial billet. The operations are performed in the following sequence: cutting pipes into dimensional workpieces; machining (turning, boring); heat treatment (quenching, tempering); machining (fine turning, boring); rotary drawing (first and second transitions); crimping the thickening; low temperature annealing. Statistical studies have found a regression equation showing at a confidence level β = 0.95, dependence of the diameter of the base hole of the workpiece after drawing in from the current value of the diameter before drawing.