SU1342562A1 - Method of bending pipes - Google Patents

Abstract

The invention relates to the field of metal forming, in particular, to the technology of pipe bending, and allows improving the quality of bending and expanding the technological possibilities of bending by providing flexible thin-walled pipes. In the method, before creating the annular plastic zone, the pipe billet is pulled in an oval caliber to (0.3-0.8) 5, where B is the degree of distribution of the pipe, with the crimping plane located from the distribution plane at a distance of 1Г 4 si а tp / 2 where a is the distance between the axis of the gauge and the axis of the roll head; Ep is the length of the rollers of the rolling head; RCD average pipe radius; S is the wall thickness of the pipe; in this case, the bending force is applied in the plane of the major axis of the oval of the pipe, and the ratio of the pulling and rolling speeds is determined from the dependence of p-a / i r r, p (Uf), where V is the pipe pulling speed; V is the rotation speed of the raskat head; p - the number of rollers of the roll head. The use of the invention makes it possible to manufacture thin-walled pipes with a bend radius-to-diameter ratio of less than 30, an ovality of less than 2.5% and with less power consumption. 3 il. (/) I WITH 4 Yu

Description

11342562

The invention relates to the processing of metals by pressure, namely, pipe bending.

The aim of the invention is the expansion of technological capabilities by providing the possibility of bending thin-walled pipes and increasing the quality of bending.

Figure 1 and 2 shows a diagram of flexible pipes; on fig.Z - section aa in figure 1.

The method is carried out as follows.

The pipe 1 is put on the head 2 with the help of oval-gauge drive rolls 3. When the middle end of the pipe 1 approaches the bending roller 4, the pipe stops moving. The rollers of the head 2 are thrust by tension. The head of the roller is rotated at the speed Uc. The tube 1 is crimped with an oval gauge 3, a plastic joint with a length a is formed and the rolls of gauge 3 begin to rotate, which move the tube in the axial direction at a speed V. Simultaneously with the axial movement of the tube, the bending roller 4 begins to bend the tube in the large plane the axis of the resulting oval tube from deformation roll caliber 3.

When rollers roll the inner surface of the pipe, bending-deformations occur, which have a different sign along the thickness of the pipe wall. When the wall thickness of the pipe is small, the plastic deformation from rolling does not cover the entire thickness of the pipe wall and, therefore, the bending force decreases slightly. The zone of plastic deformation can be increased by restricting the movement of the pipe wall from the roll rollers in the non-contact deformation zone. Thus, the roll gauge installed in the zone of non-contact deformation of the roll head increases the plastic strain zone over the pipe thickness. When the tube is compressed by the roll gauge and simultaneously distributing the tube by the roll head, a complex stress state of the tube material occurs, which is characterized by the fact that the thickness of the pipe wall within the distance a changes its sign several times. The distance a between the axis of the roll gauge and the axis of the roll head is selected as follows.

From the theory of shells, it is known that non-contact deformations extend over the length

and with pain

neck lengths are negligible. Therefore, the upper limit of a is taken to be

JS When distance a becomes less than or less, then rolling occurs.

pipe wall, which leads to an increase in working effort. Therefore, the lower limit of the distance a vl I tpca -.

In this way

s

2

(one)

0

five

When the pipe is bent in the plastic hinge area, deformation of the pipe wall is uneven over the cross section. In the plane of bending, the magnitude of deformations is greatest, and on the neutral line - the smallest. This leads to an uneven change in the pipe cross section of the mechanical characteristics of the pipe material, pipe wall thickness and to the appearance of ovality. To reduce these effects, the pipe is ovalized before rolling so that the large shaft axis is in the plane of the bending force.

Q At the same time, the total deformations due to roll-off caliber from the distribution by the rolling head and the bending force are aligned along the cross-section of the pipe, which improves the quality of the bend. On

g of a half-flat installation for bending pipes has established that the degree of pipe rolling, for which the change in the mechanical properties of the pipe after bending does not exceed the allowable, is in the range of 0.0, 05. Rolling gauge ovality (determined by the formula

). (2)

0

  (

. The compression of the tube with an oval gauge 55 is (0.3-0.8) e,

The ratio of the speeds of movement of the tube and the rotation of the rollers of the roll head is determined as follows. For high-quality bending it is necessary that the flow of the pipe is equal to

- per unit of time

did not exceed

OLR,

R

where (X, is the angle between

magnitude

rollers. This condition is met.

at speed ratio

wed

(

(3)

grades V ,.

It is plastic. In this case, when the velocity of displacing pipes V is greater than

 chTG.rTT + her

The cue hinge is working through the helix of the pipe, which degrades the quality of the bend. If the speed V is less, then the performance of the installation decreases.

Thus, the proposed method of bending pipes with the creation of a plastic hinge due to the joint deformation of the pipe in a roll caliber and distribution by the rolling head allows for the bending of thin-walled pipes in a cold state, which expands the technological capabilities of the bending equipment. The bending of the pipe in the plane of the major axis of the resulting oval of the pipe with a roller caliber improves the quality of the bent pipe.

The ratio of the speeds of movement of the pipe and the rotation of the roll head provides maximum installation performance with good bending quality.

Example. The test of the proposed method of pipe bending was carried out at the pilot plant GTR-530 with the bending of pipes with a diameter of 530 mm and a wall thickness of 7.5 mm. The unit has a roll head with five rollers. The rollers are driven by a hydraulic device. As an external gauge using a two-roll rolling mill. The pipe is bent using a hydraulic jack through a lever mechanism.

Initial data for calculation

R 262.2 mm; 0.011

 (6, 3 mm);

S 4.5 mm; Vj 1, 66 m / s.

 100 mm;

342562

According to the formula I, we define the range by changing the value of 1 40: а Ь 50. We accept a 84 mb5.

According to formula 2, we determine the degree of ovality of the caliber V I, 024, and according to formula 3 - the speed of movement of the pipe

in the axial direction - 0.126

ten

Q

five

0

0

V 0.21 m / s.

The method of pipe bending at a pilot plant is taken as the base object, in which the pipe is not crimped by an oval gauge, and the roll head is located a distance of 1 40 mm from the gauge axis.

Compared to this, the proposed method allows bending of thin-walled pipes with a bending radius of less than 30 pipe diameters and with an ovality of less than 2.5%.

During the test, three 5 variants of pipe bending were tested with one bending force -.

In the first embodiment, the compression in the oval caliber was O, the value of a was 250 mm, 0.01 (6.3 mm); in the second, the compression in the oval caliber was equal to 0, the value of a

 150 mm, 0.01 (6.3 mm); on the third - compression in the oval caliber was 2.5 mm, the value of a was 84 mm, 0.01 1 (6.3 mm).

According to the first variant of testing the pipe after bending, it had the following parameters:

The ratio of the bend radius

to diameter

Ovality of the pipe according to the second variant:

The ratio of the bend radius

to diameter

Ovality of the pipe on the third option:

The ratio of the bend radius

to diameter

Ovality pipe

The effect of the speed of movement of the pipe showed that at a speed of V 0.3 m / s, the quality of the flexible pipes deteriorated.

The use of the proposed method of pipe bending allows bending thin-walled pipes with a bend radius ratio to a diameter of less than 30 and an ovality of less than 2.5%, with less power consumption.

five

0

five

00

ten%

62.3 3%

20.5 0.4%.

0

Claims (1)

Invention Formula  A method of bending pipes, including feeding, a pipe billet, creating an annular plastic zone by dispensing with the help of a rotating roll head and applying a force to the free end of the billet, so that, in order to improve the quality of bending and expansion of technological capabilities due to the possibility of bending thin-walled pipes, a section of a pipe placed in front of the rolling head at a distance a determined from the following inequality .but. 2562 Where fO R wed Ep - the length of the working part of the rollers of the roll head; average radius of the pipe; S of the pipe wall is ovalized with a degree of deformation (0.3 ... 0.8) 6, where 6 is the degree of pipe distribution, the force is applied in the plane of the major axis of the resulting oval of the pipe the roll head is determined from the dependency VT pa (ue) -t- V (x) -1 11 i cp 15 where V is the speed of the pipe running; Vjj - the speed of rotation of the rollers roll head; p - the number of rollers of the roll head.  1 (Riga.Z