RU2192324C2 - Method for making sharply bent tubular products - Google Patents

Abstract

FIELD: plastic metal working, possibly manufacture of tubular products, for example toroidal vessels, coils, sharply bent elbows. SUBSTANCE: method comprises steps of pulling tubular blank with rod- shaped filler of easy-to-melt material simultaneously into shaping cavities of two detachable draw plates due to moving both draw plates mutually opposite until their butt jointing; preliminarily making symmetrical tapered end portions inclined relative to lengthwise axis of end portions of tubular blank and filler; upon pulling tubular blank with rod filler to draw plates at first bending tapered end portions along shaping cavities of draw plates; then stepwise pulling out-of-plate zones of tubular blank along unclamped near-draw plate portions of blank; determining length values of those portions, length of tapered zones of end portions of blank and rod according to given mathematical formulae. EFFECT: lowered labor and energy consumption at making tubular products. 2 cl, 11 dwg

Description

 The invention relates to the processing of metals by pressure, in particular to the bending of steeply curved tubular products, and can be used in the manufacture of parts such as containers of toroidal shape, coils, steeply curved elbows, etc.

 A known method of bending pipes, including the operation of filling the tube stock, securing it in the stream of the bending template and running the free end with a roller with a stream [1].

 The disadvantage of this method is that it does not provide the manufacture of bent pipe products in which the bending radius is less than the diameter of the billet.

 The closest technical solution is a method for manufacturing steeply curved tubular products by pushing a tubular workpiece into the mold cavity of a demountable die, where it is bent by the pushing force, and the pressure created by the filler inside the workpiece prevents buckling of the workpiece when it is bent [2].

The disadvantage of this method of bending pipes is the low technological capabilities, as well as significant energy consumption to overcome the friction forces during deformation of the pipe and filler when bending the workpiece by 180 ^o .

 The technical problem, the solution of which the claimed invention is directed, is to reduce energy consumption and complexity in the manufacture of products.

To solve the problem in a known method of manufacturing steeply curved tubular products, including pushing a tube billet with a filler into the mold cavity of a detachable die, a filler is made of a bar of fusible material, the bevels are preliminarily performed at the end sections of the tube billet and the rod, and the tube billet is filled with a filler in the forming cavity of the specified die is carried out simultaneously with pushing it into the forming cavity of the second detachable die by simultaneously moving both dies in the opposite direction until they close, using a tube stock of length L _Σ , determined from the dependence
L _Σ = β _g • (Do + R g),
where β _g is the bending angle of a bent product;
Do is the outer diameter of the tube billet;
Rg is the bending radius of a steeply curved product;
the bevels at the end sections of the tube stock and the rod are symmetrical and positioned at an angle to the longitudinal axis of the tube stock, the value of which α is determined from the following expression:
α = arctan (2 / β _g ),
wherein the tubular blank being pushed with a rod into the die initially folded their beveled end portions of cavities shaping the latter, and a subsequent pushing of vnefilernyh zones billets is performed in stages nezazhatym okolofilernym portions, which length l _binding is determined from the following relation,
l _St = 200 • (S ₀ ² / Do),
where S ₀ is the wall thickness of the pipe billet.

In addition, the forming cavities of closed dies are made in the form of a toroidal surface of the product with a diameter Do, a bending radius Rg and a bending angle β _g = π, with the junction plane of the dies being angled βcm = π / β, and the connector surface of each die is cylindrical, radius which is set according to
Rraz = Rg + Do / 2,
the axis of the cylindrical surface of the die connector is oriented along the axis of the product, and the coverage angle of the forming cavity of each die is β times taken
β times = π / 2.
Figure 1 shows the initial position of the workpiece with filler; figure 2 - position after bending of the end sections of the workpiece; figure 3 - position of the workpiece after closing the dies with a wide bracket; figure 4 - position after replacing a wide bracket on the middle bracket; figure 5 - position after closing the dies with the middle bracket; figure 6 - position after replacing the middle bracket on a narrow bracket; figure 7 - position before closing the dies; on Fig - position after closing the dies and manufacturing products; figure 9 - position before pushing the product from the device; figure 10 - position before removing the product from the device; figure 11 - section. A-A with a view of the open bracket (dashed lines) and the closed bracket.

A device for the manufacture of bent pipe products contains two plates 2 fixed on the table 1, which serve as guides for two dies, respectively containing such main details as:
- a platform 3 with receiving cavities 4 and pushers 6 interacting with the ejectors 5 (the drive of which is conventionally not shown);
- stationary half-matrix 7 and rotary half-matrix 8, the interaction of which is ensured by a rotary joint in the pivots 9 and 10, the holes of the latter being pierced by axial rods 11, and the fastening of the half-matrix 7 and 8 is provided by cylindrical rods 12 inserted into the corresponding holes in the rotary half-matrix 8 and plates 13 attached to stationary semi-matrices 7 (Fig.9).

 For orientation and mounting in the device of the pipe billet 14 with a bar of low-melting metal 15, brackets 16, 17 and 18 are provided (see Figs. 1, 4, 6 and 11), covering the central part of the pipe billet at the corresponding stages of forming the pipe billet 14, moreover each of the brackets 16, 17 and 18 consists of three sections pivotally connected to each other by means of the axes 19, 20 and 21 (see Fig. 11).

 The tube billet 14 and the rod 15 assembled with a female bracket 16 are installed on the stand 22 at the initial stage of shaping the product (see Fig. 11), and this stand 22 is not used in the subsequent stages of shaping the product.

 The essence of the proposed method for manufacturing steeply curved pipe products is established from the consideration of the steps below for shaping the workpiece 14 with filler 15 into the corresponding product 23. The geometric parameters of the pipe workpiece 14 are established from the condition that the coverage arcs β of the product are equal when its outer and inner radii Rn = Rg + Do and Rin = Rg to the corresponding segments of the forming blank, i.e.

откуда угол наклона скосов в трубной заготовке составляет
α = arctg(2/β) (3)
Установленные согласно (1) и (2) соответствующие параметры заготовки 14 и наполнителя 15 принимают за основу для изготовления заготовки и наполнителя, которые корректируются из условия нормального протекания процесса формообразования изделия. Полученную трубную заготовку 14 и наполнитель 15 устанавливают на раскрытую скобу 16 (фиг.1 и 11 - пунктирные линии), смыкают боковые секции скобы 16, скрепляют ее установкой оси 20 в соответствующие отверстия последней, полученную подсборку размещают на подставке 22 и ориентируют относительно двух фильер (фиг.1). При включении рабочего хода устройства его приводы (условно не показаны) обеспечивают встречное перемещение фильер, при котором скошенные участки заготовки 14 формируются по рабочим поверхностям полуматриц 7 и 8, а при достижении положения согласно фиг.2 (обеспечивающего формообразование концевых участков длиной Lк) рабочий ход приостанавливают и подставку 22 удаляют. Этим обеспечивают подготовку к последующему вталкиванию свободных, не охваченных скобой 16 участков заготовки длиной l_св, которая не приводит к потере устойчивости трубной заготовки.L _Σ = β • (Rg + Do) and Lц = β • Rg, (1)
which gives reason to establish the following obvious relationships:

where the angle of inclination of the bevels in the pipe billet is
α = arctan (2 / β) (3)
The respective parameters of the workpiece 14 and filler 15 established in accordance with (1) and (2) are taken as the basis for the manufacture of the workpiece and filler, which are adjusted from the conditions of the normal course of the product forming process. The resulting tubular billet 14 and the filler 15 are mounted on the open bracket 16 (dashed lines in FIGS. 1 and 11), the side sections of the bracket 16 are closed, fastened by installing the axis 20 in the corresponding holes of the latter, the resulting subassembly is placed on the stand 22 and oriented relative to the two dies (figure 1). When you turn on the working stroke of the device, its drives (not shown conditionally) provide onward movement of the dies, in which the beveled sections of the workpiece 14 are formed on the working surfaces of the semi-matrices 7 and 8, and when reaching the position according to Fig. 2 (ensuring the formation of end sections of length Lк), the working stroke suspend and stand 22 is removed. This provides preparation for the subsequent pushing of free, not covered by the bracket 16 sections of the workpiece with a length of l _sv , which does not lead to a loss of stability of the tube billet.

 The execution of bevels in the tube stock 14 and the filler 15 according to the given parameters ensures the tube stock deformation in two stages: at the 1st stage, the end sections are bent without a neutral line and, therefore, practically without elongation of the beveled layers of the tube stock and therefore with little resistance to deformation of the stock and filler, and therefore at low contact pressures and friction forces of the workpiece 14 in the semi-matrices 7 and 8, which reduces energy consumption at this stage of forming; at the 2nd stage, the presence of a neutral layer during bending of the central part of the billet Lс leads to stretching of the outer and compression of the inner layers of the tube billet. However, due to the small bending radii Rg, the length of these deformation centers is small, which again leads to a reduction in energy consumption at the 2nd stage of bending of the product. In addition, the noted two-stage bending of the tubular billet contributes to a significant decrease in the bending radii of the products, both due to the reduction of the bending center of the billet with a closed section, and due to its small length due to the small bending radii Rg of the products.

 Subsequent movement of the dies to the closure of their half-matrix 7 and 8 with the bracket 16 according to figure 3 provides pushing the tube billet 14 with the filler 15 without loss of stability. Moreover, by closing here and hereinafter we should understand the oncoming movement of the half-matrices 7 and 8 until they touch them with brackets 16, 17 and 18 (without pinching them between the half-matrices).

 In order to proceed to the next stage of product formation, it is necessary to remove the bracket 16 from the zone of the central part of the workpiece and install the bracket 17 in its place, for which the axis 20 is first removed from the bracket 16, which allows the bracket 16 to be opened and removed from under the central part billets and then insert the open bracket 17 there and cover the tube billet 14 with it, and then insert the axis 20 according to FIG. 4 into it.

Subsequent onward movement of the dies with their approaching 2 • l _St. leads to the position according to Fig.5. The cessation of the onward movement of the dies allows the same methods to remove and remove from the working area of the device brackets 17 and to install the brackets 18 according to Fig.6. Further rapprochement of the dies before touching them with the bracket 18 and then stopping their oncoming movement, and then performing the above methods allows you to remove the bracket 18 from the interfilter space (see Fig.7), after which the dies are moved until they are closed according to Fig.8, providing manufacture of a curved product 23.

Removing the product from the device is as follows:
- cylindrical rods 12 are pulled out from the corresponding half-matrix 8 and from the brackets 13 welded to the lower half-matrix 7;
- the left and right half-matrix 8 are rotated around the axis 11, respectively, counterclockwise and clockwise according to Fig.9;
- provide the working stroke of the hydraulic actuator (not shown conditionally), the rods 6 of which act on the ejectors 5, which ensures the removal of the end sections of the product 23 from the receivers 4 and, as a result, the product 23 is ejected with a filler 15 and with their removal from the working area of the device, then the resulting stamping is placed in a bath of boiling water to melt the fusible metal from the product 23, and the dies are returned to their original position according to figure 1 for the next cycle of shaping the product.

 Thus, according to the proposed technical solution, the cylindrical part of the workpiece 14, when pushing into the die, is subjected to combined loading by axial compression and constant internal pressure, at which the stability of a thin-walled cylindrical shell with the formation of one or two axisymmetric folds is possible. The forms of shell stability loss are shown in Fig. 29 [3]. In this case, there is a coincidence of the forms of stability loss of shells of different geometric values of Do, So, and L, which are predicted theoretically and observed experimentally (p. 106 [3]).

For example, when bending pipes with induction heating, the annular zone of the pipe is softened by heating the ring heater to a predetermined temperature, and the width of the annular zone of softening a is performed according to the dependence a = (4-6) • So, where So is the initial pipe thickness (see . 10 [4]), thereby eliminating the loss of pipe stability when bending it in the deformation zone. Thus, creating a tubular blank portions of different resistance to deformation of the material and with different resistance it to buckling, can ensure the production knuckle products without folding the tube blanks, which we proposed okolofilernye portions of the workpiece to perform the length l _binding is not greater than a critical length Lcr. at which there is a loss of stability (l _St = Lcr), and the rest of the cylindrical part of the tube billet is overwhelmed by the brackets 16, 17, 18 covering it with cylindrical surfaces.

In view of the above, the length of the near-filter portion of the workpiece l _sv (not subject to buckling) is determined according to the dependence
l _St. = 200 • (S ₀ ² / To) (4)
This, as well as the fact that the rest of the tube billet is covered with brackets 16, 17, 18 by covering it with a cylindrical surface, allows the billet 14 to be freely pushed into counter-moving dies at the steps of forming the product according to FIGS. 2, 4, 6 and 7 until it closes dies and manufacture of the product 23, and this contributes to the implementation of the brackets 16, 17, 18 three-section, which, together with the use of the stand 22 (see 11) allows:
- to carry out the subassembly of the pipe billet 14, filler 15 and the bracket 16, place it on the stand 22 and orient relative to the nozzles according to figure 1;
- change the brackets 16 to 17 and 17 to 18 using the fact that the height of the segment f in each of the sections of the brackets 16, 17, 18 is less than the thickness h of the stand 22 (see Fig. 11).

The forming cavity of the dies in the closed position is performed according to the shape of the toroidal surface of the product with a diameter D0, a bending radius Rg and a bending angle β _g = π. In this case, the plane of closure of the dies is located at an angle β _cm = π / 2 to the horizontal plane of one and a half, and the surface of the connector of the dies is made of a cylindrical radius Rraz = Rg + Do / 2.

The axis of the cylindrical surface of the die is oriented along the axis of the product, and the angle of coverage of these cavities is β times = π / 2.
The result is the simplicity and convenience of removing the stamped product and filler from the die working area for subsequent melting of the fusible metal from the product into the filler in a boiling water bath. As a fusible metal, for example, Wood's alloy (Tm = 60.5 ^o C), Goutry alloy (Tm = 45 ^o C), Lipovitsa alloy (Tm = 70 ^o C), D'Arce alloy (Tm = 140 ^{o) can be used} C) and others.

For the proposed method for manufacturing steeply curved pipe products, the use of a low-melting metal filler according to [5] has a number of technological advantages. Firstly, it is cheaper than other alloys, as contains less bismuth, and the expensive component - tin is absent in it. Secondly, the melting point of this alloy is below 100 ^o C and therefore, to melt this working medium from the obtained bent product can be used boiling water. Thirdly, the content in the fusible alloy according to [5] of zinc in 1.0, 2.0 and 3.0% provides Brinell hardness of 13.9, 15.1, 17.0 HB, respectively, which allows the use of this alloy to prevent folding of tube billets both in the end sections and in the central section of the billet when stamping steeply bent products with a wide range of mechanical properties of the material of the tube billets.

An example implementation of the method. For the manufacture of toroidal cylinder, using for this purpose two knuckle knee aluminum alloy AMg6 (σ _in = 340 MPa) for round billet diameter Up = 120 mm, the original thickness of SO = 3 mm, bending knee radius Rg = 60 mm and the angle β coverage = π = 180 we determine:
- the length of the tube billet and its central part according to the formula (1) L _Σ = β (Rg + Do) = 3.14 • (60 + 120) = 565.2 mm and Lс = β • Rg = 188.4 mm;
- bevel angle α of the tube billet and filler according to the formula (2) tan α = Up to / [(α-Lс) • 0.5] = 120 / [(565.2 - 188.4) • 0.5] = 188, 4 mm and L _Σ = arctan 120 / 188.4 = arctan 0.64 = 32.45;
- the length of the free section of the pipe, not subject to loss of stability, according to the formula (4): l _cv = 200 • (S ² / Up) = 200 • (3,5 / 120) = 20 mm (according to the formula 4);
- the number of brackets for the manufacture of one and a half m = (Lс-l _cv ) / 40 = 168.4 / 40 = 5 brackets, and the length of the corresponding brackets is L ₁ = 160, L ₂ = 120, L ₃ = 80 and L ₄ = 40 mm, and l _st = 28.4 mm;
- the radius of the cylindrical surface of the nozzle connector Rraz according to the formula (5): Rraz = Rg + Up / 2 = 60 + 60 = 120 mm.

These calculated data to establish the size and shape billets and filler deformable fusible metal, by definition okolofilernogo portion length billet, l _{communication} not liable to buckling, the number and staples parameters as well as the establishment of a cylindrical surface of radius spinnerets connector ensure the implementation of the proposed method manufacturing steeply curved tubular products.

Sources of information
1. Patent of Russia 1646115, cl. B 21 D 7/02. "A method of bending pipes and a device for its implementation", ed. Ustinets V.A. Published March 20, 1996, Bull. N8.

 2. Gorbunov M.N. The technology of procurement and stamping in the manufacture of aircraft. - M.: Mechanical Engineering, 1981, fig. 3.24, a.

 3. Korolev V. I. Elastic-plastic deformations of shells. - M.: Mechanical Engineering, 1971.

 4. Popov A.V. Bending of thin-walled pipes and profiles with local induction heating. - M .: NIAT, 1964, p. 10.

 5. A.S. 1396858 USSR. Fusible alloy based on bismuth. Munasipov Kh. M., Doronchenkov V.K., Moskovsky O.A., Leontiev Yu.M.

Claims (2)

1. A method of manufacturing steeply bent tubular products, comprising pushing a tube stock with a filler into the mold cavity of a demountable die, characterized in that a rod of low-melting material is used as a filler, the bevels are preliminarily performed at the end sections of the tube stock and the rod, and the tube blank is filled with a filler in the forming cavity of the specified die is carried out simultaneously with pushing it into the forming cavity of the second detachable die by simultaneously eremescheniya both dies in the opposite direction up to their clamping, this time with blank pipe length L _Σ, determined from the relationship
L _Σ = β _g • (Do + R g),
where β _g is the bending angle of a bent product;
Do is the outer diameter of the tube billet;
Rg is the bending radius of a steeply curved product,
the bevels at the end sections of the tube stock and the rod are symmetrical and positioned at an angle to the longitudinal axis of the tube stock, the value of which α is determined from the following expression:
α = arctan (2 / β _g ),
wherein the tubular blank being pushed with a rod into the die initially folded their beveled end portions of cavities shaping the latter, and a subsequent pushing of vnefilernyh zones billets is performed in stages nezazhatym okolofilernym portions, which length l _binding is determined from the following relationship:
l _St = 200 • (S _about ² / Do),
where So is the wall thickness of the tube billet. 2. A method of manufacturing a steeply bent pipe product according to claim 1, characterized in that the forming cavities of the closed dies are made according to the shape of the toroidal surface of the product with a diameter Do, a bending radius Rg and a bending angle β _g = π, and the closing plane of the dies is placed at an angle βcm = π / 2, and the connector surface of each die is cylindrical, the radius of which is set according to
Rraz = Rg + Do / 2,
moreover, the axis of the cylindrical surface of the die is oriented along the axis of the product, and the angle of coverage of the forming cavity of each die β times is taken equal to π / 2.

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