RU2387515C1 - Method for obtaining heat-exchange tubes with shaped ends - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: radial crimping of tube end is performed with detachable matrix segments. Matrix has final and preliminary prints. Crimping is performed on a mandrel with shaping and working teeth by detachable matrix segments. At that, in preliminary matrix print on the shaping tooth of the mandrel there formed on the tube is external annular stiffness. Then matrix is opened and tube is moved in axial direction till it contacts the matrix edge shoulder. Annular constriction of tube end is performed after external annular stiffness by applying radial force to matrix segments. At the same time, there died is internal annular stiffness which restricts axial flow of tube material to matrix preliminary print. Then by mandrelling the tube with working tooth of the mandrel there formed is annular projection and end of the tube with thickened wall.

EFFECT: improving the quality of obtained items.

6 dwg

Description

The invention relates to the field of metal forming, in particular, to processes for producing heat exchange tubes with shaped ends obtained using the effect of localized directed plastic deformation of the pipe material.

A known method of producing heat transfer pipes with shaped ends, including placing the end of the pipe in a detachable matrix, fixing it from possible movement and the subsequent formation of an annular protrusion by applying axial compressive force to the pipe end (RU No. 2160175 C2, IPC B21D 39/06).

The disadvantages of this method include the need to use hydraulic presses with high nominal forces, since the formation of annular protrusions is carried out by plastic flow of pipe material from the axial force applied to its end.

There is also known a method of producing heat exchange tubes with profiled endings, including preparing the pipe by straightening it, cutting to the extent and cleaning the outer surface of the ends, radial crimping of the pipe end by segments of a split matrix having a fine engraving in the form of an annular groove of a trapezoidal cross section and preliminary engraving in the form of an annular excavation, and the formation on the pipe of an annular ledge (RU 2202431 C2, 04.20.2003, B21D 53/08, 41/00, bull. No. 11 - prototype).

The disadvantage of this method should include the axial flow of the material with a radial crimp of the end of the pipe, which does not lead to the preliminary filling of the final engraving of the matrix. Therefore, the burning process will be limited by the forces of friction between the working surface of the split matrix and the outer surface of the pipe end. As a result, for high-quality shaping of the annular protrusion, a mandrel with a large working tooth in diameter is required, which means that there will be a thinning of the tip blade.

The objective of the invention is to develop such a method for producing heat exchange tubes with profiled endings, which would ensure high-quality shaping of the annular protrusion and did not lead to unregulated thinning of the blade.

The technical result is achieved by the fact that in the method for producing pipes with shaped ends, including preparing the pipe by straightening it, cutting to the extent and cleaning the outer surface of the ends, radial crimping of the pipe end by segments of a split matrix having a fine engraving in the form of an annular groove of a trapezoidal cross section and preliminary engraving in the form of an annular recess, and the formation of an annular protrusion on the pipe, according to the invention, the radial crimping of the end of the pipe is carried out on a mandrel with forming and working teeth and segments of a detachable matrix with an end collar, into which a pipe is installed with its end placed in the plane of the inner edge of the final engraving, and by applying a radial force to the segments, external ring stiffness is formed on the pipe in a preliminary engraving of the matrix on the mandrel tooth, then the detachable matrix is opened and move the pipe in the axial direction to contact with the end face of the matrix with the location of the formed external ring stiffness opposite the final engraving of the matrix s, the pipe is fixed from possible movements and applying a radial force to the segments of the matrix, annular pinch of the end of the pipe behind external ring stiffness is performed with simultaneous stamping on the pipe of internal ring stiffness, limiting the axial flow of the pipe material into the preliminary engraving of the matrix, and preliminary filling of the material of the pipe with a fine engraving of the matrix then an annular protrusion is formed on the pipe by its mandrel mandrel mandrel with the final tooth of the mandrel with the final filling of the material pipe h Stow engraving matrix, whereupon the pipe burnishing working tooth mandrel continue with providing a pipe extrusion material in pre-forming and engraving matrix pipe ending with a thickened wall.

Implementation of the proposed method for producing pipes with profiled endings allows you to get high-quality annular protrusions without causing unregulated thinning of the web wall.

This is due to the fact that they use the effective design of the pre-shaped ending, as a result of which it became possible to use the operation of the local ring clamping of the pipe, reaching:

- effective limitation of the deformation zone by the location of the inner edge of the final engraving of the split matrix;

- partial filling of the volume of the fine engraving of the matrix with external ring stiffness and pipe material extruded in the axial direction;

- translation of the processed pipe material into a plastic state by axial bending deformation of its web.

The invention is illustrated by drawings, where in Fig.1 - shows the initial position of the die tooling and heat transfer pipe before performing the operation of stamping external ring stiffness; figure 2 is the stage of completion of the stamping operation of the external ring stiffness; figure 3 - the initial position of the die tooling and pipes with external ring stiffness before performing the operation of the ring clamping; figure 4 is the same after the operation of the ring clamping and stamping of the inner ring stiffness; figure 5 - shows the stage of completion of the formation of the annular protrusion and thickening in the canvas by the operation of burnishing; Fig.6 is a profiled ending containing an annular protrusion and a thickening in the canvas.

An embodiment of the invention is as follows.

On the heat exchange pipe 1, operations are performed to prepare the outer surface of its ends for profiling: straightening pipes in a Kosovalkovy machine, measuring length cuts and cleaning the surface of the ends to a metallic sheen.

Next, profiling of the ends of the pipe is carried out.

The heat exchange pipe 1 is installed in the cavity of the detachable matrix 2, containing the finishing 3 and preliminary 4 engravings (figure 1). The pipe is installed by placing its end in the plane of the inner edge of the fine engraving. Pipes are fixed from possible movements (shown by an arrow outside the matrix). Then, from the side of the free end of the matrix, a mandrel 5 is installed, having a forming 6 and working 7 teeth. In this case, the forming tooth is placed opposite the preliminary engraving of the split matrix.

Further, applying a radial force to the segments of the split matrix (there are 3 of them), they radially crimp the end of the pipe, giving it an inner diameter equal to the diameter of the mandrel rod. Note that this operation leads to local deformation of the pipe in the transverse direction and the formation of external ring stiffness (Fig.2).

Next, open the segments of the matrix and move the pipe in the axial direction, providing contact of its end with the end collar of the matrix. Thus, the external ring stiffness is located opposite the final engraving of the matrix. The forming tooth of the mandrel remains in the same position. Applying a radial force to the segments of the matrix, perform a local annular clamping of the pipe with the simultaneous stamping of the inner ring stiffness on the forming tooth of the mandrel. In this case, the volume of pipe material caused by axial deformation during ring clamping leads, along with stamping of the internal ring stiffness, to the preliminary filling of the fine engraving. The inner ring stiffness prevents the extrusion of the pipe material into the preliminary engraving (figure 4).

Further, applying axial force to the mandrel, cause its movement and, as a result, the final shaping of the annular protrusion in the fine engraving of the split matrix. Burning continues until the conical surface of the working tooth of the mandrel comes out of contact with the inner surface of the pipe (figure 5). In the latter case, a leaf with a thickened wall located in the preliminary engraving is formed in the tip.

After removing the pipe from the die tooling, it will have two compensation volumes in the form of an annular protrusion and a thickened web wall with regulated thinning of the end wall outside the compensation volumes (Fig.6).

A pilot test of the developed method was carried out upon receipt of profiled endings on pipes made of steel 10 with a cross section of ⌀ 25 × 19.8 mm, intended for the manufacture of tube bundles.

Profiling was carried out in the technological equipment of a double-action hydraulic press, developing a maximum force of 0.6 MN. After the radial crimping operation, the compressed section of the pipe had the following geometric dimensions: outer diameter - 24.3 mm, inner - 18.98 mm, length 7 mm. The width of the transition conical section was 2 mm. The crimping force at the final stage was 328 kN. The Deform 2D simulation program allowed us to estimate the volume of elongation of the pipe material during crimping, which amounted to 25 mm ³ . This makes it possible to better pre-fill the free volume of the fine prints of the split matrix. The stress intensity in the pipe material, which is in the final engraving of the detachable matrix, at the stage of preliminary filling is not lower than the yield strength. Ending cavities of the endings was carried out by a stepped mandrel with a diameter of working and forming teeth equal to 19.6 mm. The force of burnishing did not exceed 90.6 kN.

The technological equipment for obtaining profiled endings was made of hardened steel U8 with an accuracy of 9th grade and HRC hardness after hardening of at least 56 units.

It has been established that the preliminary profiling of the pipe ends and their subsequent local clamping provide for the preliminary filling of the fine engraving of the matrix with the pipe material and translate the processed material into a plastic state. The operation of the burnishing of the cavity of the end of the pipe ensures the reproduction of annular protrusions with the dimensions specified by the executive dimensions of the die tooling.

The invention is applicable in the manufacture of tube bundles of heat exchangers for oil refining, petrochemical, gas and other industries.

Claims (1)

A method of producing heat exchange tubes with profiled endings, including preparing the pipe by straightening, moderately cutting and cleaning the outer surface of the ends, radial crimping of the pipe end by segments of a detachable matrix having a fine engraving in the form of an annular groove of a trapezoidal cross section and preliminary engraving in the form of an annular recess, and the formation on the pipe of an annular protrusion, characterized in that the radial crimping of the end of the pipe is carried out on the mandrel with forming and working teeth segments of the split matrix with an end collar into which the pipe is mounted with its end placed in the plane of the inner edge of the fine engraving, and by applying a radial force to the segments, external ring stiffness is formed on the pipe in a preliminary engraving of the matrix on the mandrel tooth, then the split matrix is opened and the pipe is moved to axial direction to contact with the end face of the matrix with the location of the formed external ring stiffness opposite the final engraving of the matrix, the pipe is fixed against possible displacements and applying a radial force to the segments of the matrix, annular pinch of the end of the pipe for external ring stiffness is performed with simultaneous stamping on the pipe of internal ring stiffness, limiting the axial flow of the pipe material into the preliminary engraving of the matrix, and preliminary filling of the pipe with the finishing material of the matrix engraving, then forming on the pipe annular protrusion with its mandrel working mandrel mandrel with the final filling of the pipe material of the final engraving of the matrix, after burnishing its working tooth tube mandrel continue with providing a pipe extrusion material in pre-forming and engraving matrix pipe ending with a thickened wall.

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