Stamping axisymmetric forgings

Abstract

As a rule, cylindrical blanks are used in hot bulk stamping of axisymmetric parts. However, cutting the rod into measured lengths is associated with fluctuation in mass of the blank on account of distortion of its end geometry and change in its length. Therefore, seams arise in the stamping of such blanks. A promising approach to the deformation of axisymmetric parts (gears, disks, flanges, etc.) is stamping from spherical blanks obtained by hot rolling of rod on a ball-rolling mill. In the present work, experiments on the seamless stamping of axisymmetric forgings from a spherical blank (diameter 60 mm) are conducted for flanges and lids. The forgings are illustrated in Fig. 1, with the relevant dimensions. In the first stage of our research, the stamping of these forgings is simulated on a computer by the finiteelement method [1]. In the second stage, the model is verified. Computer simulation permits study of the filling of the die’s contours by metal and the deformation over the diametric cross section of the forging; evaluation of the nonuniformity of deformation; and the identification of points of possible defect formation in stamping. By computer simulation, new products may be introduced more rapidly, with smaller outlays. Simulation of the filling of the stamp cavity indicates that it is completely filled with metal; there is no burring. No pinching or cracking of the metal is observed. The distribution of the accumulated strain in the axial plane is shown on the right side of Figs. 1a and 1b for a flange and lid forging, respectively, in the form of lines of equal strain. As is evident from Fig. 1a, the strain distribution over the cross section of the forging is nonuniform. The surface layers of the upper and lower plates in the flange experience the least strain e i = 0.49. The central layers of the hub experience the greatest strain. In stamping the lid (Fig. 1b), the surface layer of the central projection experiences the least strain e i < 0.14, while the internal layers of the forging closer to the bottom experience the greatest strain e i = 1.7. On the basis of the computer simulation, the strain distribution in different cross sections of the forging is plotted. The continuous curves in Fig. 2a denote the strain intensity in cross sections A , B , and C . In cross section C , the least strain is observed in the upper region of the concave hub. In the central part of the hub, the strain rises to a maximum, beyond which it falls. In cross section B , the maximum strain is again in the central region. In horizontal cross section C , the strain falls from e i = 2.48 in the central region to e i = 0.72 in the crown at the edge of the forging.