RU2540287C2 - Device for forming thin-wall axially symmetric parts shaped to truncated cone - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to cold sheet forging, particularly, to shaping of thin-wall axially symmetric shells and can be used for production of large-size thin-wall truncated cone-shape parts at dual-action presses. Stretching forces are developed along billet generatrix directed from smaller diameter to larger one by resilient variable-depth element.

EFFECT: higher quality of shells.

1 dwg

Description

The invention relates to cold sheet stamping, in particular to the formation of thin-walled axisymmetric shells, and can be used in the manufacture of large-sized thin-walled parts of a truncated tapering shape on double-acting presses.

A known method of distribution of the shell (A. S. 1563813 USSR, MKI ⁵ B21D 41/02, publ. 15.05.90, Bull. No. 18) to obtain a cylindrical shell from a pipe billet of a smaller diameter. According to the proposed solution, the method is implemented in two stages: at the first stage of distribution, the preform is deformed into a convex shape until a circumferential deformation in the central part of 95-98% is reached, at the ends 0.2-1% of the required strain value. During the wedge, sections of the expanding tool are moved apart in the radial direction. At the second stage, the center of plastic deformation extends from the ends of the workpiece to its central part until it is given the desired cylindrical shape. Distribution is carried out by two expanding tools using a wedge.

The disadvantage of this method is obtained by shaping the distribution of the facet of the part and the repetition of the process with the rotation of the workpiece in a circle after each transition, or the presence of an additional process of heat setting. This leads to an increase in labor intensity, additional energy costs.

The closest in technical essence is the method of stamping axisymmetric parts with an elastic tool of variable stiffness (A.S. 755378 USSR, MKI4 B21D 22/10, publ. 1980, Bull. No. 30), in which the sequential deformation of the workpiece occurs in the form of a directed wave. At the same time, at the beginning of the process, a small portion of the workpiece is formed by local pressure of the elastic medium, the value of which ensures stability. With increasing press force, the loading zone of the workpiece and the deformation zone are sequentially distributed along the axis of the workpiece until the part is completely formed along the matrix contour. The process diagram is carried out during one stroke of the press using a punch consisting of elastic ring elements (washers) with different compression characteristics, i.e. with variable compression stiffness. In the process of forming parts at any given time, a small section of the workpiece is deformed with dimensions that do not allow loss of stability. The part of the preform lying below this section is already a molded and pressed elastic medium to the matrix, and the upper part is not yet in contact with the punch. In the molding process, it is freely pulled into the deformation zone, which reduces the thinning of the part wall and increases the limiting degree of the workpiece forming in one transition.

The disadvantage of this method is the excessive complexity of manufacturing due to the low utilization of the material; the need for significant additional shaping efforts due to the large area of the elastic medium from the side of the application of efforts for shaping.

(где S - толщина заготовки; D - средний диаметр), приводящих к смятию. Не исключены гофрообразование, потеря устойчивости свободной части, так как она деформируется в условиях напряженно-деформируемой схемы, близкой к процессу вытяжки, где действуют сжимающие тангенциальные напряжения.The quality of the obtained part is reduced due to the arising compression friction forces between the workpiece and the elastic medium for thin-walled workpieces $$\frac{S}{D}\le 0,008$$

(where S is the thickness of the workpiece; D is the average diameter) leading to collapse. Corrugation, loss of stability of the free part are not ruled out, since it is deformed under the conditions of a stress-deformable circuit close to the drawing process, where compressive tangential stresses act.

The objective of the invention is to obtain high-quality thin-walled axisymmetric tapering parts without cutting in one stroke of the press, increasing the utilization of the material.

The problem is solved due to the fact that in the method of forming thin-walled axisymmetric parts of a truncated tapering shape from cylindrical workpieces by applying uniformly circumferential internal pressure according to the invention create tensile forces along the forming workpiece, directed from a smaller diameter to a larger one.

The method is implemented using the device and is illustrated in the drawing.

The device contains under the upper plate of the stamp 1 sliding sectors 2, an elastic element 3, a matrix 4, a cone with guide grooves 5, a support ring 6 mounted on the plate of the stamp 7. The workpiece 8.

The method is as follows:

The support ring 6 is raised up. The matrix is taken up to a height that ensures the installation of the workpiece. The sliding sectors 2 are raised upward together with the elastic element 3. In this position, a cylindrical workpiece is mounted on top of the elastic element. The elastic element is made in the form of a conical shell of variable thickness. Moreover, the greatest thickness is made in the zone of small diameters, and the smallest - in the zone of large diameters. The blank is used in the form of a cylindrical shell with a radius:

r _zag = const.

To obtain a uniform wall thickness of the part, it is necessary to create such external conditions that allow to obtain the same strain in thickness due to the meridional, tangential tensile stresses. The result is achieved during deformation due to the ongoing increase in the inner diameter of the elastic element. In the proposed arrangement, the elastic element moves in the direction from a smaller to a larger diameter of the deformable workpiece, creating tensile forces along the forming workpiece, directed from a smaller diameter to a larger one and increasing from a free end with a large diameter to a smaller diameter pressed against the working surface of the matrix, which allows thinning elements in the zone of small diameter of the workpiece. Due to tensile stresses, the deformation in thickness can reach values as for elements in the zone of the largest diameter, although tangential deformation is less for elements of a smaller workpiece than for elements of a larger diameter.

Claims (1)

A method of forming thin-walled axisymmetric parts of a truncated tapering shape from cylindrical billets, comprising applying uniform internal pressure to the circumference and creating tensile forces along the generatrix of the deformable billet, directed from its smaller diameter to the larger one, characterized in that the tensile forces are created by means of an elastic element made in the form conical shell of variable thickness, which is installed with the largest diameter in the zone of smaller diameter emoy preform and is moved in the direction from the smaller to the larger diameter of the deformable preform.