RU2559623C1 - Forming of thin-wall tee-bands - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to metal forming, particularly, to forming of pipe side surface branches and can be used for fabrication of thin-wall tee-bands from pipe blanks. This method comprises forming of the branch on pipe blank side surfaces by internal pressure of preset magnitude at simultaneous axial compression of the blank, boring blank bottom and flanging by tiff male die. Bore diameter is specified by mathematical relationship. After fitting of stiff male die in bore of branch inside, bore flanging is performed at simultaneous axial compression of the blank by application of excess pressure set by mathematical relationship.

EFFECT: higher efficiency of the process.

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Description

The invention relates to the field of metal forming, in particular to methods of forming processes on the side surface of the pipe, and can be used for the manufacture of thin-walled tees from a tube billet.

A known method of forming tees in which the manufacture of a tee is carried out by molding the lateral process with internal fluid pressure while axially compressing the tube stock with axial punches (Davydov O.Yu., Egorov V.G., Nevstroyev Yu.A. Stamping unequal tees from tube blanks into demountable dies. - Procurement in mechanical engineering, No. 6, 2005. P. 40-44).

The disadvantage of this method is the low height of the process of the finished product. When the process’s bottom is cut along with the bottom, the zone of the radius transition from the bottom to the process’s walls is also removed, which reduces the height of the finished process. For the implementation of this scheme of blank forming, specialized presses for hydraulic stamping are required, which have limited application.

The closest in technical essence to the claimed method, which is adopted as a prototype, is a method that is carried out as follows (Lukyanov V.P., Matkava I.I., Boyko V.A. Stamping, bending of parts for welded vessels, apparatuses and boilers M.: Engineering, 2003, p. 386, Fig. 166). On the side surface of the tube billet, the process is molded with a bottom with internal pressure during axial compression of the tube billet with filler. After that, a hole is cut in the bottom of the process, which is then flanged by a rigid punch. Since the diameter of the punch for flanging is slightly larger than the diameter of the hole in the bottom of the process, there is an increase in the diameter and extension of the walls of the process. The height of the appendix during flanging of the hole increases. There is no need to remove the radius zone of rounding of the molded process.

The internal pressure with which the process of molding is carried out must be of a certain regulated value. Exceeding this pressure leads to the destruction of the process in its pole at the stage of formation of the process.

The disadvantage of this method also lies in the low height of the manufactured process on the side surface of the tube stock.

The task of the invention is to increase the height of the stamped process and reduce labor costs for the manufacture of parts.

The problem is solved due to the fact that in the method of forming thin-walled tees, which includes forming a process on the side surface of a tube stock with internal pressure of a regulated value of P _regl with simultaneous axial compression of the workpiece, then making a hole in the bottom of the process and flanging it with a rigid punch, according to the claimed method, the diameter a bore _holes in the bottom of the ridge, is made a value determined by the relationship:

D _hole = D _neg / e ^δ

where D _OTR - diameter of the finished process of the tee;

δ is the relative uniform elongation of the tee material when tested for uniaxial tension;

and after installing a rigid punch in the hole of the internal cavity of the appendix, the subsequent flanging of the hole is carried out with simultaneous axial compression of the workpiece by applying excessive internal pressure of

P _huts = (1.2-1.25) P _regl

The final stage of the tee forming process, in which the hole is flanged, in addition to simple flanging, is accompanied by axial compression of the pipe billet, in contrast to the prototype. This allows you to continue drawing metal into the lateral process from the body of the pipe, while continuing to increase the height of the process due to molding. At this stage, the height of the process increases due to two processes: an increase in the height of the bead as a result of flanging and an increase in the height of the process as a result of the supply of metal from the body of the pipe billet. This leads to an increase in the total height of the stamped process. The stamping method is illustrated by drawings:

In the figure 1 to the left of the axis of symmetry shows the initial position of the deformable workpiece, and on the right - the completion of the preliminary stage of the formation of the appendix on the side surface of the pipe using the internal pressure of the regulated value R _reg .

Figure 2 shows a blank, in which process is made bottom opening diameter D _{of holes.} A punch is installed in this hole, and an excess pressure P _gage is created in the inner cavity of the workpiece.

The figure 3 shows the end of the process of forming a hollow tee, in which the process of molding and flanging of the hole in the bottom of the tee is completed.

In the drawings, the following notation.

On the plane of the connector of the semi-matrices 1, a working die is made, which consists of a through cylindrical cavity for accommodating the initial tube billet 2 and a cavity perpendicular to it for molding the process. Axial punches 5 are located inside the working die of the semi-dies. On the cylindrical surface of the axial punches there are ledges, on which the ends of the pipe billet are supported and with which axial compression of the deformable billet is carried out. Inside the workpiece 2 is a combined punch consisting of a metal insert 3 and an elastic segment 4, complementing each other to the circumference. From the ends of the workpiece 2 are stepped punches 5, which are initially in contact with the elastic segment 4 and the upper protruding end of the tube stock 2.

The working ends of the axial punches 3 have a stepped shape of the working surface. The protruding part of the working surface of the punches compresses the elastic element 4, while the ledge of the punch fixes the position of the rigid inner insert 3.

The manufacture of the tap on the side surface of the tubular billet in the inventive device is carried out simultaneously as a result of two processes - forming the tap by thinning and stretching the workpiece in the deformation zone and the additional metal volume entering the deformation zone as a result of axial compression of the workpiece. For the successful process of stamping the tee, a regulated amount of internal pressure P _regl from compression of the elastic element is necessary, which should also be connected by a certain ratio with the amount of movement of the end face of the workpiece.

As the axial punches 5 move towards each other, they begin to compress the elastic segment 4, creating internal pressure in the inner cavity of the deformable workpiece 2. The pressure is determined by the ratio between the size of the rigid metal insert 3 and the elastic segment 4. The larger the cross section of the elastic segment 4, the a large amount of the displaced volume of the elastic element is fed into the inner cavity of the preform 2, the greater the pressure is created inside the deformable preform. The required pressure value at the preliminary stage of the appendix formation should be a well-defined regulated value, which prevents the destruction of the workpiece. This pressure value is created by a combined punch consisting of a metal segment and complementing it to the circumference of the elastic segment (see USSR author's certificate No. 1238824. Device for forming hollow products with bends. Publish. June 23, 86, bull. No. 23).

The rigid mandrel 3, which is included in the composite punch, plays a dual role. Firstly, it preserves the shape of the workpiece during the formation of the branch and prevents distortion of the shape of the workpiece. Secondly, with a change in its cross-sectional area, it becomes possible to adjust the amount of internal pressure from compression of the elastic element.

A regulated value of internal pressure can be considered one in which the values of the displaced volumes of the elastic element supplied from the ends of the workpiece and entering the internal cavity of the formed process should be approximately equal.

The steps made on the cylindrical surfaces of the axial punches 5 simultaneously with the compression of the elastic element 4, carry out the axial compression of the workpiece 2, feeding the metal into the deformation zone of the metal during molding of the process.

The value of the regulated pressure P _regl can be determined

in a first approximation according to the following methodology (Isachenkov EI Stamping with rubber and liquid. M: Mechanical Engineering, 1967. p. 171, formula 207):

q = S (σ ₁ / R ₁ + σ ₂ / R ₂ )

q is the pressure required to deform the workpiece;

S is the thickness of the deformable workpiece

σ ₁ - the magnitude of the voltage acting in the meridional direction;

R ₁ is the radius of curvature of the workpiece in the meridional direction;

σ ₂ is the magnitude of the stress acting in the tangential direction;

R ₂ is the radius of curvature of the workpiece in the tangential direction;

After the process of forming the process with access to the cylindrical section of the workpiece, the lateral surface of the process adhered to the matrix and became rectilinear, we can assume that uniaxial tension and σ ₂ = 0 act in this area (see Romanovsky V.P. Handbook on cold stamping . L.: Mechanical Engineering, 1971. p. 108, Fig. 92). Then the second term in this equation becomes zero.

R ₁ - the radius of curvature of the workpiece in the meridional direction is equal to the radius of the rounding of the transition zone from the bottom to the cylindrical wall of the process. Typically, this radius is not performed at a low pitch and taken equal to R ₁ = (5-6) S of the thickness of the deformable billet (see Romanovsky V.P. Handbook of cold stamping. L .: Mechanical Engineering, 1971. p. 226, table 87) .

σ ₁ - the value of the strain stress, taking into account the strain hardening of the material, can be taken equal to the conditional tensile strength of the workpiece material σ _b .

Then, taking into account the foregoing, the regulated pressure value necessary for stable molding of the process on the lateral surface of the tube stock can be defined as a first approximation as

P _regl = (0.16-0.2) σ _b ;

where: σ _b is the conditional tensile strength of the workpiece material σ _b .

If you create a pressure for molding the process is much greater than this value, this can lead to excessive thinning and destruction of the workpiece.

If the molding pressure is less than this value, then wrinkles and corrugations will arise on the cylindrical wall of the tube stock from the action of the axial compression force of the blank.

Under the action of P _regl at the preliminary stage of deformation of the workpiece on the side surface of the tube billet is formed a process of height H _neg . At this point, strain hardening of the metal being stamped occurs and further deformation of the workpiece begins to occur unstable and be accompanied by certain difficulties. Therefore, at this point, further deformation of the workpiece is stopped, it is annealed to restore the original ductility.

The process is made bottom opening diameter D _{of holes,} whose value is determined depending on

D _hole = D _neg / e ^δ

where D _OTR - diameter of the finished process of the tee;

δ is the relative uniform elongation of the tee material when tested for uniaxial tension;

The use of such a hole allows you to get the maximum possible value of the height of the process after flanging holes and, of course, to reduce the total labor costs for the formation of the tee.

The fact is that when a hole is flanged in the workpiece, a complex stress-strain state is observed (see Popov EA, Fundamentals of the theory of sheet stamping. Textbook for high schools. M .: Mashinostroenie, 1977. p. 239, Fig. 89). The maximum tensile strain is observed in the annular element of the hole with a minimum radius located on the edge of the hole. It is on this element that the destruction of the workpiece begins when the ultimate strain is exceeded. The maximum tensile strain of this element to fracture depends mainly on the plastic properties of the metal of the deformable workpiece. The plastic properties of the workpiece material are determined during uniaxial tensile testing and are characterized by the relative uniform elongation δ (see Melnikov EL, Cold stamping of bottoms. M .: Mashinostroenie, 1976. p. 17, table 2). If the tensile strain of the annular element of this value is exceeded, the destruction of the workpiece begins.

The maximum tensile value at the edge of the initial hole is defined as

ε _θ = lnD _Neg / W _holes

where: D _OTR - diameter of the finished process of the tee;

D _{of holes} - hole diameter, manufactured in the bottom ridge. This deformation cannot be larger than the relative uniform elongation δ for a given material. I.e

ε ₀ = 8

Knowing the predetermined value of the finished process of diameter on the tee and the mechanical properties of a formed metal (relative uniform elongation δ), one can determine the initial hole diameter D _{of holes,} at which the distribution will not occur the destruction of the workpiece and the deformation amount flanging, and hence the height of the ridge will maximize .

D _hole = D _neg / e ^δ

Using this dependence allows you to maximize the plastic properties of the metal. For low-plastic materials, it helps to prevent the destruction of the workpiece during flanging, and for high-plastic materials it is possible to achieve maximum deformation during obturation of the hole and to produce a process of the maximum possible height.

After making a hole in the bottom of the process and heat treatment of the workpiece to restore the initial plasticity, a flat punch for flanging 6 and then an elastic element 7 is installed in the cavity of the process in the cavity of the process. The process of deforming the workpiece continues by compressing the elastic element 7 with axial punches 8, which They already have a flat end for compression, and not a step, as in the previous stage. With their stepped steps, the punches 8 compress the workpiece 2 while continuing to push it into the deformation zone, increasing the height of the process on the workpiece. That is, there is a combination of the process of molding the process with axial compression of the tube stock.

At this stage of the process, the combined punch, consisting of a rigid insert 3 and an elastic segment 4, is replaced by a continuous elastic punch 7, which completely covers the entire cross section of the workpiece. When such a punch 7 is compressed by axial punches 8 with flat ends, the volume of the displaced volume from the side of the ends of the workpiece becomes larger than the amount of the displaced volume required to form the process below the punch for flanging.

As a result of this, the pressure inside the workpiece begins to increase in comparison with the previous P _{regl value} . This overpressure begins to act on the flange punch. Under the influence of this excess pressure, the process of flanging of the hole made in the bottom of the preformed process begins. The diameter of the hole begins to increase, and the height of the process begins to increase.

Thus, after installing the punch for flanging, two processes begin to occur simultaneously. One is the molding of the process during axial compression of the tube billet (as it was at the initial stage of the workpiece forming), which increases the height of the process. The second is the flanging of the hole and the straightening of the walls with an increase in the height of the process.

As studies have shown, as a result, the height of the process increases by 15-25% compared with the height carried out in the prototype of the invention.

As a result of the fact that the value of the displaced volume supplied from the end face of the preform with a flat punch increases when the rigid metal insert is removed compared to the initial stage of the process, the pressure inside the tube preform increases by 20-25% depending on the thickness and the degree of deformation of the flanging of the hole.

Studies have shown that as a result of the claimed stamping method, the plastic properties of the metal are used to the maximum when flanging, and the process height is added as a result of pushing during axial compression at the final stage of the tee shaping process, the process height is increased by 15-25% compared to height carried out in a traditional process.

Claims (1)

A method of forming thin tees comprising forming process on the lateral surface of the tubular billet by internal application of pressure regulated value R _Reglami while axially compressing the preform, fabrication holes in the bottom of the process and its subsequent flanging rigid punch, characterized in that the determined diameter D _{of holes} openings, manufactured in the bottom of the appendix, according to:
D _hole = D _neg / e ^δ
where D _OTR - diameter of the finished process of the tee;
δ is the relative uniform elongation of the tee material when tested for uniaxial tension,
establish a rigid punch in the said hole of the internal cavity of the process and carry out the flanging of the hole by applying excessive pressure P _form = (1.2-1.25) P _reg with simultaneous axial compression of the workpiece.

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