JPS61115619A - Straightening method of pipe - Google Patents

Abstract

PURPOSE:To elevate the out-of-roundness of a pipe by performing a rolling reduction at the prescribed liquid pressure and by preventing the back flow of the liquid of said device in case of the force that the roll receives from the pipe being above the prescribed pressure when a pipe is straightened passing through rolls pair with hydraulic reduction device. CONSTITUTION:Hydraulic rolling reduction devices 10, 20 are composed of as shown in the figure. A pipe P is transferred in the arrow direction and detected just before the pipe tip enters into a roll 1 and the valve is changed over so as to supply the oil to the pressure reducing valve 13 which is set to the pressure regulated to give the prescribed crush quantity delta0 at the time of the control device being of the pipe outer diameter D. Now the pipe tip is started to be subjected to a rolling reduction simultaneously with its entering into the roll 1 and becomes the roll gap which the hydraulic pressure determined by the valve 13 is obtd. At this time when the roll gap is A and the outer diameter of the pipe tip is D, the crush quantity makes delta0 but because of the rolling reduction load being equal even in case of D'' smaller than the diameter D due to the motion of the valve 13 or A' smaller than the gap A, the crush quantity is constant in delta0. However in case of D' larger than D the oil pressure inside the oil chamber 11 is increased by the action of a check valve 12 and the crush quantity becomes larger than delta0. It is same on rolls 2, 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for straightening a tube using an inclined opposing roll straightening machine, and more specifically to straightening a tube.

The present invention relates to a method for straightening a tube capable of improving roundness, particularly to improving roundness.

[Prior art]

Various types of roll arrangement types are known as tube straightening machines, and for example, as shown in FIG. A type (2-2-2 type) straightening machine with vertical roll arrangement is known. In this straightening machine, among three pairs of opposing rolls, each of the upper rolls 1a, 2a, 3a on the entry side, intermediate side, and exit side and the lower roll 2b in the middle can be moved up and down by a screw type rolling device 4. Each lower roll 1b, 3b is fixed, each roll 1, 2
．． 3 is made slightly smaller than the outside diameter of the tube, pressure (crush) is applied to the tube P, and the middle upper and lower rolls 2a and 2b are moved to the upper and lower rolls 1a and 1b on the entry side and the upper and lower rolls 3a on the exit side, respectively. 3b (offset), bending stress is applied to the tube by the upper rolls la and 3a on the entry and exit sides, and the lower roll 2b in the middle to correct the bending.

In this straightening, the crush amount δ, which is the difference between the tube outer diameter and the roll spacing A, is usually about 3% of the tube outer diameter, so the conventional screw type reduction method does not have sufficient accuracy in setting the roll spacing. However, the amount of crushing fluctuated due to backlash, backlash in the bearings, elastic deformation of the roller support member, etc., combined with variations in the outer diameter of the tube.

FIG. 5 is a graph showing the mill stiffness curve X and the tube plasticity curve Y, with the roll gap and tube outer diameter plotted on the horizontal axis and the load plotted on the vertical axis.

As mentioned above, there is a roll gap A' due to a setting error with respect to the set roll gap A, and there is also a tube outer diameter D' due to variations in the tube outer diameter.

Therefore, the roll gap varies with respect to the amount of crushing δ0 when the roll gap is on the outer diameter of the tube, and this is A', and the amount of crushing when the tube is on the outside diameter is δl, and the outer diameter of the tube varies and this is D' When the roll gap is SA, the crush amount is δ2, which varies from process to process.

Therefore, when the amount of crushing fluctuates in this manner, sufficient correction may not be made, and the amount of crushing may become excessive, resulting in residual stress that may cause stress corrosion cracking in the product. To prevent this residual stress from occurring, the amount of crush is kept constant within a predetermined range during the straightening process.
It is desirable to prevent residual stress from occurring.

The applicant of the present application has proposed a method disclosed in Japanese Patent Application Laid-open No. 128318/1983 in order to properly correct and prevent the generation of excessive residual stress. As shown in FIG. 6, this method uses a hydraulic pressure reducing device, for example, a hydraulic pump 8, for the lower roll tb on the entry side, the lower roll 3b on the exit side, and the upper roll 2a on the intermediate side, which crush the pipes, among the rolls of the inclined opposed roll straightening machine. The pressure oil sent from the is set to a predetermined pressure by the constant pressure valve 9 and then transferred to the rolls lb, 3b, 2.
A device configured to be able to supply to the cylinders 7 attached to each is provided, and the pressure of the constant pressure valve 9 is set based on the amount of Kudefushie desired to be applied to a predetermined outer diameter portion of the pipe and the plasticity curve of the pipe, and this set pressure is kept constant. In this method, the pipe is straightened by a predetermined amount of crush.

[Problems to be solved by the invention]: 'When straightening by this method, the setting pressure is kept constant and the rolling force is kept constant, so the mill stiffness curve shown in FIG. 7 is obtained.

FIG. 7, like FIG. 5, is a graph showing the mill stiffness curve X and the tube plasticity curve Y, with the roll gap and tube outer diameter plotted on the horizontal axis and the load plotted on the vertical axis. As can be understood, the mill stiffness curve has a constant value above the load corresponding to the set pressure of the constant pressure valve 9, and therefore, even after correction, when the outside diameter of the pipe is D', the outside diameter varies with respect to the outside diameter of the pipe. The amount of crushing δ3 is equal to the amount of crushing δ0 when the outside diameter of the tube is reduced.

In other words, the amount of crush is the same at each position regardless of whether the outer diameter of the pipe is large or the circumferential position is small. Therefore, when using this method, residual stress does not occur, but there is a problem in that it is difficult to improve the roundness of the tube.

[Means for solving problems]

The present invention has been made in view of this problem, and it is possible to reduce the pressure of the roll that imparts crushing to the pipe at a predetermined hydraulic pressure using a hydraulic pressure reduction device, and when the force received by the roll from the pipe exceeds the predetermined pressure. The purpose of the present invention is to provide a pipe straightening method that can correct the bending of the pipe, prevent the generation of excessive residual stress, and improve the roundness by preventing the backflow of liquid in a hydraulic pressure reduction device. .

A method for straightening a pipe according to the present invention is a method for straightening a bend in a pipe by passing a pipe between a pair of rolls equipped with at least a hydraulic pressure reducing device, and applying a crush to the pipe. A pressure regulator for the hydraulic pressure in the hydraulic cylinder is provided between the cylinder and the hydraulic pressure source, and the hydraulic pressure in the hydraulic cylinder is lower than the regulated hydraulic pressure by the force applied to the hydraulic cylinder from the roll side. In order to prevent the liquid from flowing back toward the hydraulic pressure source when the pressure rises, and to improve the roundness of the pipe, the pipe is lowered with a regulated hydraulic pressure or a higher hydraulic pressure, It is characterized by adding a crash.

〔Example〕

The present invention will be specifically explained below based on the drawings.

Figure 1 shows the present invention with inclined facing 60 single type (2-2-2 type).
It is a schematic diagram showing the implementation state when it is applicable to a vertical roll arrangement straightening machine, and P in the figure indicates a pipe to be straightened. The pipe P is the entrance roll 1° intermediate roll 2. of the straightening machine. The tube is transferred skinny in the longitudinal direction of the tube axis (in the direction of the white arrow) by the exit roll 3, and the straightening machine can apply a predetermined offset amount and required crassoche amount to the tube P between rolls 1, 2, and 3. It is composed of

Conventional screw-type lowering devices 4, 4.4 are provided on each of the upper rolls la, 3a on the entry side and the exit side, and the intermediate lower roll 2b, respectively, for adjusting the roll position.
, 2b, and 3a are adjusted in height by lowering devices 4, 4.4, respectively, so as to apply a predetermined offset amount to the pipe P.

The pivot support of the lower entry roll lb and the lower exit roll 3b is a single-acting cylinder 11°1 that is part of the hydraulic lowering device 10.10.
1, and the heights of the rolls lb and 3b and the pipe lowering blades are adjusted by a hydraulic lowering device 10.10. Single-acting cylinders 11 and 11 have cylinder rods facing downward and cylinder tubes in rolls xb and 3b, respectively.
The cylinder rod is fixed to the shaft of the cylinder.

The rod advancement oil chamber 11a of the single-acting cylinder 11 receives pressurized oil sent out at a sufficiently high pressure from the hydraulic pump 16 through a throttle valve 15 with a reversing valve that allows the pressure oil to return freely, and has a variable secondary pressure. The pressure oil is supplied to the proportional electromagnetic pressure reducing valve 13 and reduced to the set pressure thereof, and is then supplied via the check valve 12. A bypass passage 10b for returning pressure oil is connected from the cylinder side of the check valve 12 to the pump side of the pressure reducing valve 13, and a check valve 14 is attached to the bypass passage fob.

Therefore, the pressure in the single-acting cylinder 11 of the hydraulic pressure reduction device 10 becomes the pressure set in the pressure reducing valve 13, but the pressure in the single-acting cylinder 1
When the pressure in the oil chamber 11a becomes higher than the set pressure of the pressure reducing valve 13 due to the force received from the roll 1b, the check valve 14
Since the pressure on the pump side is sufficiently high, pressure oil does not return through the check valve 14, and the pipe P is crushed with the same force as the force that the single acting cylinder 11 receives from the roll 1b.

Note that the pressure in the oil chamber 11a is lower than the set pressure of the pressure reducing valve 13.
When both pressures are high and the pressure becomes higher than the pump side pressure, the pressure oil returns to the pump side via the check valve 14 and is discharged to the tank by a leaf valve (not shown) provided on the pump side. It has become.

The pivot portion of the intermediate upper roll 2a is supported by a double-acting cylinder 21 that is a part of the hydraulic lowering device 20 and a fixed screw type lowering device 4, and the height of the roll 2a is determined by the hydraulic lowering device 20. The pipe reduction blade of the roll 2a is adjusted by a hydraulic reduction device 20.

The double-acting cylinder 21 has a cylinder tube attached to the pivot portion of the roll 2a with the cylinder rod facing upward, and the cylinder rod serves as a screw for the lowering device 4. The hydraulic lowering device 20 is configured to be able to press the roll 2a downward and lift it upward, and a hydraulic pump 25 is installed in the (lower) oil chamber 21a for rod advancement of the double-acting cylinder 21.
The pressure oil sent out at a sufficiently high pressure is supplied to the proportional electromagnetic pressure reducing valve 23 with variable secondary pressure, and the pressure oil reduced to the set pressure is supplied via the check valve 22. ing.

Further, a bypass passage 20b for returning pressure oil is connected from the cylinder side of the check valve 22 to the pump line (2) of the pressure reducing valve 23, and a check valve 24 is provided in the bypass passage 20b.

Further, pressure oil sent out from a hydraulic pump 26 is supplied to the (upper side) oil chamber 21b for entering and leaving the roll so as to be maintained at a constant pressure corresponding to the weight of the roll by a constant pressure valve 25.

Therefore, the pressure in the oil chamber 1a for advancing the roll of the double-acting cylinder 21 becomes the pressure set in the pressure reducing valve 23, but
When the pressure in the oil chamber 21a becomes higher than the set pressure in the oil chamber 21a due to the force received from the oil chamber 21a, the pressure on the pump side of the check valve 24 is sufficiently high, so that pressure oil does not return through the check valve 24, and the pressure in the oil chamber 21a increases.
The pipe P is crushed with the same force as the force received from the roll 2a.

Since the pressure in the oil chamber 21b is set to a value corresponding to the roll's own weight, the hydraulic lowering device 20. Double acting cylinder 2
1 is not affected by the roll's own weight, and the reduction blade of the roll 2a to the pipe P can be adjusted by the pressure difference between the oil chambers 21a and 21b.

In addition, optical sensors (
(not shown) is installed, and while these detect the presence of a pipe between each roll, a control device (not shown) that inputs a ratio check signal is connected to a hydraulic pump 16 and an orifice with a check valve. Valve 1
A valve (not shown) provided between the hydraulic pump 16 and the pressure reducing valve 23 is switched between the valve (not shown) provided between the hydraulic pump 16 and the pressure reducing valve 23, and the pressure oil sent from the hydraulic pump 16. supply to.

The straightening method of the present invention, which aims to straighten the bending of a tube and improve its roundness using the straightening machine configured as described above, will be described below. First, transfer of the rolled pipe P is started. When the tip of the pipe P enters the entrance roll 1, an optical sensor (not shown) detects this, and this detection causes the mill stiffness curve X and the pipe plasticity curve Y shown in FIG.
Based on
3. Switch the valve (not shown) to supply fuel.

As a result, the tip of the tube begins to be rolled down as soon as it enters the roll 1, and the rolled down position of the roll 1b becomes a position that is a gap between the rolls where the oil pressure determined by the pressure reducing valve 13 is obtained. As shown in Figure 2, if the roll gap at this time is A and the outer diameter of the tube tip is D, the crush amount will be δ0, but due to the action of reduced pressure #-13, D# is smaller than the tube outer diameter. Also, even if A' is smaller than the roll gap A, the rolling load is uniform, so the crush amount is constant at δ0. However, for example, when D' is larger than D, the check valve 1
Due to the action of 2, the oil pressure in the oil chamber 11 increases, the rolling load increases, and the crush amount becomes δ4 (>δ0).

Now, as the pipe P is transferred and the pipe outer diameter becomes smaller as shown in FIG. The roll gap is maintained [FIG. 3(B)] and becomes smaller [FIG. 3(C)], and a predetermined crush amount δ0 is applied to the pipe P [FIG. 3(D)].

When the outside diameter of the pipe reaches a minimum value and then starts to increase, the presence of the check valve 12 prevents the pressure oil from flowing back, and the roll gap is fixed at A1 when Dl, as shown in Fig. 3 (c). , therefore, after that, the crush amount δ0 in the larger diameter part
A larger amount of crush continues to be applied to the pipe P until the next outer diameter becomes the same outer diameter D1 [Fig. 3 (d)], and the outer diameter of the pipe further decreases until the outer diameter reaches 2 (D2 < I), ). During this period, the roll gap is reduced to A2 by the action of the pressure reducing valve 13, and a crush amount δ0 is applied.

Then, when the pipe diameter becomes larger than D2, the oil pressure in the oil chamber ILa increases again, and the crush amount becomes a value larger than δ0. The mill stiffness curve X at the roll gapper 1 when the minimum value Dl is taken is shown by a two-dot chain line in FIG.
In the change region of ', the plateau of the load is exceeded, and the amount of crushing, for example δ, is larger than δ0.

As described above, the rush is applied in the same manner by rolls 2 and 3. As a result, a crush amount of δ0 or more is imparted over the entire length of the tube, and a large crush amount is imparted to the circumferential portion of the tube where the outer diameter is larger than the diameter of the tip of the tube, resulting in high roundness.

The rear end of the tube is connected to each roll 1. 2. 3, valves (not shown) between the throttle valve with check valve and the hydraulic pump and between the pressure reducing valve and the hydraulic pump are switched to communicate with the tank. As a result, the internal pressure oil in each cylinder 11.21 is removed from the check valve 14.
．． Reflux from 24 to the tank.

Note that the present invention can improve the roundness of a pipe even when the purpose is not to straighten the bend of the pipe and an offset is not applied to the pipe.

The present invention also provides a method for applying crush force to a pipe of a predetermined outer diameter even when the roll gap A' is set or changed to a value different from the target set value A due to variations in the roll gap.
Since rTi is set to a constant value, a predetermined amount of crush can be applied to the pipe within a range below the predetermined pipe outer diameter.
In addition, at a pipe circumferential position larger than a predetermined pipe outer diameter, the crack 7 increases.
You can add a certain amount. Therefore, the present invention can improve roundness even when the roll gap changes or when the roll gap is set differently.

In addition, in the above embodiment, the cylinder tube is attached to the pivot portion of the roll, but the present invention can also be carried out even if the direction of the cylinder iron is reversed from that in Section 111 and the cylinder tube is attached to the pivot portion of the roll. Of course.

Further, in the above embodiment, each hydraulic pressure lowering device 210°20
Check valves 12 and 22 are installed in the pipe, but if the cylinder rod is poorly rounded, the cylinder rod advances and retracts rapidly, causing a delay in the response of the pressure reducing valve, which is the same as check valve 12.22. Since it acts on J, this can be omitted.

Furthermore, the present invention is not limited to the vertical roll arrangement straightening machine of the inclined opposed 60-ru type (2-2-2 type), but also applies to other inclined opposed roll type straightening machines, such as the 50-ru type, the 60-ru type, etc. It goes without saying that the present invention can be applied to straightening machines, horizontal roll straightening machines, etc., and when the present invention is applied to horizontal roll straightening machines, all single-acting cylinders should be used because the weight of the rollers under pressure of the roll tube does not affect the present invention. It can also be implemented.

Moreover, in the above embodiment, pressure oil is used to operate the cylinder, but the present invention is not limited to this and can be practiced using other liquids.

〔effect〕

Next, the effects of the present invention will be explained. The present invention corrects bends in pipes and prevents excessive residual stress from occurring.

In order to improve roundness, the rolling force range for single-acting cylinders is 7.5 to 68 tons, and for double-acting cylinders it is 0 to 60 tons.
Test tubes with different amounts of ellipse were straightened as 51-tons.

Table 1 is a table summarizing the dimensions of the sample tube, its ellipse amount, and the ellipse amount after the above-mentioned correction.For comparison, the same sample tube was straightened by the conventional method of JP-A-55-128318. The results are also shown.

Table 1 As can be understood from this table, in the comparative example, only about 20% of the ellipse before correction is corrected, but in the present invention, the ellipse before correction is small from the beginning.
With the exception of the 5u thick tube, we were able to correct more than 90% of the ellipse before straightening, and we were able to manufacture tubes with high roundness.

As detailed above, the present invention automatically adjusts the amount of correction according to the shape of the outer surface of the pipe so that the amount of crush is larger than the predetermined amount at circumferential positions where the outer diameter of the pipe is large, and the amount of crush is greater than the predetermined amount at circumferential positions where the outer diameter is small. Since the tube is straightened by changing the angle of the tube, it has excellent effects such as high roundness, suppressing residual stress, and making it possible to manufacture a tube without bending.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the implementation state of the present invention, Figure 2 is an explanatory diagram of the roll load of the present invention, Figure 3 is an explanatory diagram of the straightening method of the present invention, and Figures 4 and 6 are conventional straightening. The schematic diagram of the machine, FIGS. 5 and 7, are illustrations of the correction contents. P...Pipe 1,2.3...Roll 10.20...
・Hydraulic pressure Applicant Sumitomo Metal Industries Co., Ltd. Manager Patent attorney Noboru Kono 3 Figure 4 Figure 4 Roll gap, construction outside the pipe Figure 6 Figure 6 Roll gap, pipe diameter 7 ==ri>

Claims (1)

[Claims] 1. In a method of straightening a bend in a pipe by passing a pipe between a pair of rolls equipped with at least a hydraulic pressure reduction device and applying a crush to the pipe, between a hydraulic cylinder that drives the rolls to reduce pressure and a hydraulic pressure source. A pressure regulator for the hydraulic pressure in the hydraulic cylinder is installed on the hydraulic cylinder, and if the hydraulic pressure in the hydraulic cylinder rises above the regulated hydraulic pressure due to the force applied to the hydraulic cylinder from the roll side, the hydraulic pressure source side to prevent backflow of liquid to the
A method for straightening a pipe, characterized in that, in order to improve the roundness of the pipe, the pipe is compressed with a regulated hydraulic pressure or a higher hydraulic pressure to impart a crush.