JP2009285709A - Manufacturing apparatus of electric resistance welded tube excellent in buckling resistance property - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem of not sufficiently improving buckling resistance property of an electric resistance welded tube by conventional technology. <P>SOLUTION: In the manufacturing method of the electric resistance welded tube, a steel strip is roll formed while it is being passed, both abutted ends of the strip in a width direction are electric-resistance-welded to form a tube, heat treatment is applied to an electric resistance welded area, and then the tube is straightened by a rotary straightening machine. The rotary straightening machine is not a general one but one 1 having a plurality of stands and allowing the distance between these stands to be variable. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus for manufacturing an ERW pipe excellent in buckling resistance, and in particular, manufacturing an ERW pipe excellent in buckling resistance that is not easily affected by an earthquake or frozen soil even after laying as a line pipe. Relates to the device.

In many cases, UOE steel pipes are applied to pipelines for transporting oil, natural gas, and the like, and JCO, spiral steel pipes, seamless steel pipes, and partly electric-welded pipes are also applied.
The ERW tube is a workpiece (work object) made of hot-rolled strip made of an open tube by continuously rounding the plate width by roll forming, and both ends of the rounded plate width converge to a V shape. The seam is manufactured by electro-welding. However, since the work cross-sectional shape cannot be made to be a perfect circle during the roll forming, the ERW pipe has mechanical characteristics that are not uniform in the circumferential direction compared to other steel pipes. Therefore, after making the pipe by electro-welding, it was further corrected with a sizer to bring it closer to the target roundness, but the non-uniform distortion in the circumferential direction remained.

  As a result, laying ERW pipes as line pipes has the problem of local buckling and damage to the pipes when an earthquake occurs. Due to the ground change, the compressive force acts in the longitudinal direction of the pipe, and the pipe tends to buckle and bend easily, and also has a problem that leads to breakage. Therefore, when an electric resistance welded pipe is applied to a line pipe, the installation condition of the electric resistance welded pipe is greatly restricted. Therefore, the penetration rate of the electric resistance welded pipe has to be lower than that of a UOE steel pipe.

Conventionally, in order to popularize ERW pipes, for example, as shown in Patent Documents 1 and 2, etc., API standard X80 steel pipes with excellent low-temperature toughness due to improved materials and steel materials for line pipes having mechanical composite characteristics Technology development is underway.
JP 58-34133 A Japanese Patent No. 3903747

However, all of the above conventional techniques change the average mechanical properties of the material or the steel pipe, and do not equalize the mechanical characteristics due to non-uniform strain generated during the forming in the pipe circumferential direction. Absent.
When the present inventors examined the circumferential direction mechanical characteristics of the ERW pipe line pipe, when the work was roll-formed, in particular, the center part of the plate width, that is, approximately 180 on the opposite side of the welded part after becoming a pipe. The strain is concentrated near the bottom of the plate and the mechanical characteristics are lowered, which is a major cause of non-uniform characteristics in the pipe circumferential direction. Moreover, since the sizer that corrects only by a small amount of diameter reduction by a hole-type roll without rotating the tube is often used to correct the tube after pipe making, distortion concentrated on a specific part in the circumferential direction of the tube is used. It cannot be dispersed at all. That is, the conventional technique cannot sufficiently improve the buckling resistance performance of the ERW pipe, and this is a problem.

This invention is for solving the said subject, The summary structure is as follows.
(Claim 1)
Roll forming while passing the strip, electro-sewing welded both ends of the abutted plate width to form a pipe, heat-treating the electro-welded weld, and then straightening the pipe with a rotation straightener The rotating straightening machine has a plurality of stands, and the distance between the stands is variable. The manufacturing apparatus for an electric resistance welded tube having excellent buckling resistance.
(Claim 2)
The rotation correction machine is characterized in that the distance between the stands can be set to a value different from a material passing direction distance per (N / 2) ± 0.025 rotation of the pipe, where N is a natural number. The manufacturing apparatus of the electric resistance welded tube which is excellent in the buckling-proof performance of 1.
(Claim 3)
The rotation straightener has a total of 3 or more stands, the front stage is the entrance stand, the last stage is the exit stand, and the stand between them is the central stand. The roll resistance of the central stand can be raised or lowered within a range of +1 mm or more and +40 mm or less with respect to that of both the entrance side and exit side stands. An electro-resistance tube manufacturing device with excellent buckling performance.

  According to the present invention, it is possible to obtain relatively uniform mechanical characteristics in the circumferential direction of the ERW pipe, and the ERW pipe is less susceptible to buckling due to earthquakes and frozen soil even after laying as a line pipe. Can be manufactured.

  FIG. 3 is a schematic diagram showing an example of a conventional electro-welded pipe manufacturing apparatus. The apparatus of FIG. 3 includes an uncoiler 8 for discharging the strip, a leveler 9 for correcting the strip that has been discharged, a roll forming machine 11 that rolls the corrected strip so as to round the plate width, and a roll. A fin path stand 10 that is in charge of the final stage of the molding machine 11 and abuts both ends of the plate width; and an induction heating means 12 comprising contact tips that inductively heat the abutted both ends (seams before welding); Pressure welding means 13 comprising a squeeze roll for joining the induction-heated seam before welding. This induction heating and joining is called electric resistance welding. The band plate becomes a pipe 17 by electro-welding.

  3 further includes a bead part cutting machine 14 for cutting the bead part of the pipe 17 after the electric seam welding, and an electric seam welded part of the pipe 17 after the bead part cutting (the seam after welding and its surroundings). A seam annealer (not shown) that heat-treats the heat-affected zone), a sizer 18 that adjusts the outer diameter of the pipe 17 after the heat treatment of the ERW weld section, and the pipe 17 after the outer diameter adjustment is cut to a predetermined length A tube cutting machine 16. Reference numeral 20 denotes a material passing direction of the pipe 10 (taken in the pipe longitudinal direction).

  FIG. 2 is a schematic view showing an example of an electro-welded pipe manufacturing apparatus referred to in the present invention. 2 is configured in the same manner as in FIG. 3 from the uncoiler 8 to the seam annealer, but the configuration downstream from the seam annealer is different from that in FIG. That is, the apparatus of FIG. 2 includes a tube cutting machine 16 that cuts the pipe 17 after the ERW welding to a predetermined length on the exit side of the seam annealer, and a rotation straightening machine that rotates and corrects the pipe 17 after the cutting. And 15.

In general, the rotation corrector 15 is used to correct the roundness and bending of a pipe. This rotation straightening machine consists of a series of three or more stands with a total of 3 rolls of hourglass rolls whose surface shape is a rotational hyperboloid shape, and the material passing direction while rotating the pipe with the drum rolls. It has a mechanism for feeding in the (longitudinal direction of the tube).
The present inventors have intensively studied the behavior of the material (work that has become a tube) in rotation correction, and as a result, in rotation correction using a plurality of stands, compression strain accumulates in the longitudinal direction of the tube between the stands, Alternatively, it has been found that compressive strain and tensile strain are alternately applied in the longitudinal direction. These suggest that the effect of reducing the yield stress of the material, called the Bauschinger effect in the longitudinal direction of the tube, works effectively. If compressive strain is applied in the longitudinal direction, the yield stress can be easily reduced in subsequent material tests in which tensile strain is applied. If compressive / tensile strain acts alternately in the longitudinal direction, movable dislocations increase within the material, yielding. Stress is easily reduced. Moreover, the strain tends to be uniform in the circumferential direction of the tube due to the rotation of the tube.Furthermore, when examining the circumferential distribution of the yield stress, not only the yield stress of the entire tube is reduced, but also It was understood that the strain tends to equalize in the circumferential direction.

  On the other hand, in conventional ERW pipe manufacturing, roll forming is performed so that the width of a workpiece made of a strip is continuously bent along an arc shape, and the workpiece cross section is shaped along a perfect circle during the roll forming. Therefore, the uneven strain in the circumferential direction remained. According to the investigation results of the present inventors, the cause was that the sizer was frequently used. Since the sizer corrects only by a small amount of diameter reduction by the hole-type roll without rotating the tube, the strain concentrated at a specific portion in the circumferential direction of the tube could not be dispersed at all.

  Therefore, by utilizing the above-mentioned useful action in rotation correction and applying rotation correction to the ERW pipe after pipe making, the yield stress of the ERW pipe that is not uniform in the circumferential direction can be made uniform, The buckling resistance can be greatly improved. As a result, when this ERW pipe is laid as a line pipe, it will be difficult to buckle locally even in the event of an earthquake, and the pipe will not be damaged. Withstands the compressive force applied in the longitudinal direction of the pipe due to the ground change that freezes, the pipe is less likely to buckle and bend.

  In order to make the bausinger effect as uniform as possible in the circumferential and longitudinal direction of the tube with a rotation straightener, not only increase the number of contact between the tube and the roll, but also different parts of the tube contact the roll sequentially. It is necessary to do so. This is because if the same part of the tube is always in contact with the roll of each stand of a multi-stand rotation corrector, the strain concentrates only on the local part of the tube, and the strain is uniform in the circumferential and longitudinal directions of the tube. This is because it cannot be dispersed.

  Therefore, the present inventors examined means for sequentially bringing different portions of the pipe into contact with the roll, and as a result, the distance between the stands in relation to the outer diameter D of the pipe and the roll inclination angle α. I came up with the idea that it should be excluded from a specific range. In the rotation corrector, as shown in FIG. 4, the hourglass roll 21 is inclined and the tube 17 is advanced by the feed speed in the material passing direction 20 generated along with the rotation of the roll. Further, the minimum diameter portion a at the central portion in the roll axis direction of the hourglass roll 21 is substantially synchronized to rotate the pipe 17 in the pipe circumferential direction. Therefore, if the number of rotations of the tube while the tube is advanced by the distance between the stands is substantially equal to a natural number multiple of a half rotation, the tube is locally divided into a portion that always contacts the roll and a portion that does not always contact the roll. That is why.

Therefore, if the number of rotations of the tube during the advancement of the tube by the distance between the stands does not become a value substantially equal to a natural number multiple of a half rotation, different positions in the outer surface of the tube will be in the roll of any one of the stands. It is possible to make contact with and to distribute the strain in the circumferential direction of the tube.
For this purpose, such a setting is facilitated if the distance between the stands is variable. Therefore, in the present invention, for example, as shown in FIG. 2, roll forming is performed while passing a strip, and both ends of the abutted plate width are electroformed and welded to form a pipe, and the electroformed weld is heat treated. After that, in the electric sewing tube manufacturing apparatus for correcting the pipe with the rotation straightening machine 15, the rotation straightening machine 15 having a variable distance between the stands is used. In order to make the distance between the stands variable, it is preferable to place the stands on a rail so that the stands can move in parallel.

  FIG. 1 is a schematic view showing an example of a rotation straightening machine 1 having a variable distance between stands used in the present invention. The rotation straightening machine 1 is composed of three stands, and a pair of upper and lower drum-shaped rolls 3 that are brought into contact with the pipe 17 is arranged on each stand 2 at a predetermined roll inclination angle with the material passing direction (pipe longitudinal direction) 4. Has been. By passing the pipe 17 between the upper and lower rolls 3, the pipe 17 goes straight in the pipe longitudinal direction 4 and rotates in the pipe circumferential direction 5. Each stand 2 rides on the rail 6, and the distance 7 between the stands can be changed by moving the stand 2 as it is.

Further, as described above, in order to prevent the number of rotations of the tube during the advancement of the distance between the stands from being a value substantially equal to a natural number multiple of half rotation, It is preferable that the distance between the stands can be set to a value different from a material passing direction distance per (N / 2) ± 0.025 rotation of the pipe, where N is a natural number.
That is, the preferable setting range of the distance between the stands is within the establishment range of the inequality given by the following equation (1).

L ≠ D × π × tan α × A (1)
Here, L is the distance between the stands of the rotation corrector [mm], D is the outer diameter of the tube [mm], π is the circumference [−], α is the roll inclination angle of the rotation corrector, that is, the roll axis direction. An angle [degree or radian] formed by the direction in which the pipe passes through, and A is a number [−] within a range of (N / 2) ± 0.025, where N is a natural number, and this “(N / 2) ± 0.025 "Range" corresponds to the value range of "a value approximately equal to a natural number multiple of half rotation".

  In addition, the rotation correction machine is usually composed of 3 or more total stands, each stand has 2 rolls of upper and lower totals, the front stage is the entrance stand, the last stage is the exit stand, and the stand between them is the central stand, Make the roll height of both the entrance and exit stands almost the same (the same when the error is less than 1 mm), and raise or lower the roll height of the central stand with respect to these roll heights to cause bending strain in the longitudinal direction of the tube. Add.

  Therefore, the present inventors diligently studied means for further effectively reducing the yield point of the material due to the Bauschinger effect using a rotation corrector. As a result, the roll height of the central stand is higher than the roll height of the entry stand of the rotation straightening machine (abbreviated entry roll height) and the roll height of the exit stand (abbreviated exit roll height). It has been found that the height (abbreviated as the center roll height) may be raised or lowered within a range of +1 mm or more and +40 mm or less.

That is, if the amount of increase or decrease in the central roll height relative to the heights of both the entry side and the exit side is less than +1 mm, the compressive strain in the longitudinal direction of the pipe is insufficient and is within the elastic deformation of the material. Remarkably low. Further, if the amount of increase or decrease in the height of the central roll exceeds +40 mm, the flattening amount due to the bending of the tube becomes remarkably large, and the roundness of the tube is impaired.
Therefore, the rotation correction machine used in the present invention has a total of three or more stands, the front stage being the entrance side stand, the last stage being the exit side stand, and the stand between them as the central stand. It is preferable that the height is substantially the same, and the roll height of the central stand can be raised or lowered within the range of +1 mm or more and +40 mm or less with respect to both the entrance side and exit side stands. Note that the amount of increase or decrease in the center roll height relative to the height of both the entry side and the exit side rolls is abbreviated as the center roll increase amount or the center roll decrease amount.

  In view of the above, the best mode of the device according to the present invention (the device of the present invention) is to form a pipe by roll forming while passing a strip, and welding both ends of the butted plate width together to form a pipe. An electric sewing tube manufacturing apparatus for correcting a pipe with a rotation straightening machine after heat-treating a sewing weld, wherein the rotation correction machine has a total of three or more stands and a distance between the stands of these stands is The distance between the stands can be set to a value different from the material passing direction distance per (N / 2) ± 0.025 rotation of the pipe, where N is a natural number, and the first stage is on the input side. Stand, the last stage is the exit stand, and the stand between them is the central stand, the roll height of both the entrance and exit sides is almost the same, the roll height of the center stand is the entrance and exit both stands Rise in the range of + 1mm to + 40mm The other is made of is capable lowered.

The device of the present invention (Example device) as an example is the device of the present invention in which the rotation straightening machine is of the best mode in the device shown in FIG. In addition, an Example apparatus is variable in the range whose center roll raise amount is more than 0 mm and +50 mm or less. A usage example of the embodiment apparatus and a usage example of the conventional apparatus (shown in FIG. 3) will be described.
In these use examples, the strips having a steel composition containing 0.05% C, 0.2% Si and 1.2% Mn in mass% are used as raw materials, and the straightening conditions after forming a pipe are shown in Table 1. No. An electric resistance welded tube having an outer diameter D of 600 mm and a wall thickness of 19.1 mm was manufactured under the conditions shown in columns 1 to 4. Ten JIS No. 13 tensile test pieces in the longitudinal direction of the pipe from the position of approximately 90 degrees in the circumferential direction and approximately 180 degrees (corresponding to the arc-shaped plate bottom) from the welded part of the manufactured ERW pipe Cut out and conducted a tensile test to determine and evaluate the mechanical properties.
(No. 1) As an example of use of the example apparatus, the distance L between the stands of the rotation correction machine and the amount of increase in the center roll are respectively No. 1 in Table 1. The values shown in the first column were set. The roll inclination angle was 30 degrees. The establishment range of the formula (1) here is L ≠ 600 × π × tan30 ° × {(N / 2) ± 0.025} = 1088.279 × {(N / 2) ± 0.025}. When 517 to 571 [mm], N = 2, L ≠ 1061 to 1115 [mm], when N = 3, L ≠ 1605 to 1660 [mm], when N = 4, L ≠ 2149 to 2203 [mm], and so on. Therefore, within this range, L = 1800 mm.
(No. 2) As an example of use of the example apparatus, the distance L between the stands of the rotation correction machine and the amount of increase in the center roll are respectively No. 2 in Table 1. The values shown in column 2 were set. The roll inclination angle α was 50 degrees. Here, the establishment range of the equation (1) is L ≠ 600 × π × tan50 ° × {(N / 2) ± 0.025} = 2246.402 × {(N / 2) ± 0.025}. From 1067 to 1179 [mm], when N = 2, L ≠ 2190 to 2303 [mm], and so on. Therefore, L = 1150 mm outside this range.
(No. 3) As an example of use of the example apparatus, the distance L between the stands of the rotation correction machine and the amount of increase in the center roll are respectively No. 3 in Table 1. The values shown in column 3 were set. The roll inclination angle α was 2 degrees. Here, the range of establishment of equation (1) is L ≠ 600 × π × tan2 ° × {(N / 2) ± 0.025} = 65.824 × {(N / 2) ± 0.025}. From 1644 to 1647 [mm], when N = 51, L ≠ 1677 to 1680 [mm], and so on. Therefore, L = 1678 mm outside this range.
(No. 4) As an example of use of the conventional apparatus, the sizer in FIG.

  No. above. Table 1 shows the results of determining the mechanical properties of the electric resistance welded tube manufactured under each correction condition of 1-4. Table 1 shows that the yield stress YS in the vicinity of the 180 degree position is the conventional example device in the electric resistance welded tube according to the usage example (No. 1) in which the stand interval of the rotation correction machine and the central roll ascent amount in the example device are set to suitable ranges. It is lower than the above example of use and shows a value close to that in the vicinity of the 90-degree position, and is excellent in buckling resistance. On the other hand, the usage example (No. 2) of the electric sewing tube and the conventional example device according to the usage example (No. 2) in which the stand interval of the rotation correction machine in the example device is out of the preferable range and the central roll ascent amount falls outside the preferable range. .4), the yield stress YS in the vicinity of the 180 degree position is higher than that in the vicinity of the 90 degree position, and the buckling resistance performance is inferior. Further, in the correction condition of the usage example (No. 3) in which the stand interval of the rotation correction machine in the embodiment apparatus is out of the preferable range and the central roll rising amount is out of the preferable range, there is a large flatness when the rotation of the pipe is corrected. At the same time, the threading speed was remarkably reduced, and the ERW tube as an acceptable product could not be manufactured.

It is the schematic which shows an example of the rotation correction machine used for this invention. It is the schematic which shows an example of the manufacturing apparatus of the electric resistance welded tube used as the reference of this invention. It is the schematic which shows an example of the manufacturing apparatus of the electric sewing tube used frequently conventionally. (A) is a top view which shows roll arrangement | positioning of the rotation correction machine used for this invention, (b) is a definition explanatory drawing of a roll inclination angle.

Explanation of symbols

D Outer diameter of tube α Roll inclination angle 1 Rotational straightener used in the present invention 2 Stand 3 Hourglass roll 4 Pipe longitudinal direction (direction of material passing)
5 Pipe circumferential direction 6 Rail 7 Stand pipe distance 8 Uncoiler 9 Leveler
10 Fin pass stand
11 Roll forming machine
12 Induction heating means (contact chip)
13 Pressure contact means (squeeze roll)
14 Bead cutting machine
15 Rotating straightener
16 pipe cutting machine
17 tubes
18 Sizer
20 Feeding direction
21 Hourglass roll
21a, 21b Roll axis
22 Pass line

Claims (3)

  Roll forming while passing the strip, electro-sewing welded both ends of the abutted plate width to form a pipe, heat-treating the electro-welded weld, and then straightening the pipe with a rotation straightener The rotating straightening machine has a plurality of stands, and the distance between the stands is variable. The manufacturing apparatus for an electric resistance welded tube having excellent buckling resistance.   The rotation correction machine is characterized in that the distance between the stands can be set to a value different from a material passing direction distance per (N / 2) ± 0.025 rotation of the pipe, where N is a natural number. The manufacturing apparatus of the electric resistance welded tube which is excellent in the buckling-proof performance of 1.   The rotation straightener has a total of 3 or more stands, the front stage is the entrance stand, the last stage is the exit stand, and the stand between them is the central stand. The roll resistance of the central stand can be raised or lowered within a range of +1 mm or more and +40 mm or less with respect to that of both the entrance side and exit side stands. A device for manufacturing ERW pipes with excellent buckling performance.

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