JP6641985B2 - Pipe wall thickness measuring device and wall thickness measuring method - Google Patents

Description

  The present invention relates to a wall thickness measuring apparatus and a wall thickness measuring method, and more particularly to a wall thickness measuring apparatus and a wall thickness measuring method for a seamless pipe manufactured by using three rolls.

  Drawing 1 is a figure showing an example of a manufacturing process of a seamless tube. The billet heated in the heating furnace is pierced and rolled by a piercing machine (not shown) to form the hollow shell 10. The hollow shell 10 is subjected to elongation rolling using a mandrel bar 11 and a mandrel mill 12 composed of a plurality of stands, and the outer diameter and the thickness are adjusted by a sizer 13 and the like, and then rolled to a constant diameter.

  A problem in the process of manufacturing a seamless pipe is the so-called uneven thickness in which the thickness of the pipe in the circumferential direction is uneven. When uneven thickness occurs, the strength is insufficient at a thin portion, which is a thin portion, and when used in a high-pressure environment, it may cause so-called crushing of a pipe that is crushed. As shown in FIG. 2, the uneven thickness has various shapes according to the cause of occurrence.

  One of the causes of the uneven thickness is the elongation rolling process using the above mandrel bar and mandrel mill. FIG. 3 is a view showing the mandrel bar 11 and the two stand mandrel mills 12 as viewed in the pipe axis direction. FIG. 3a shows a two-roll mandrel mill. Two rolling rolls 12a are arranged so as to face each other, and the rolling stands 12a are shifted by 90 ° between adjacent stands. On the other hand, FIG. 3b shows a three-roll type mandrel mill. The three rolling rolls 12a are arranged so as to form 120 ° in the rolling direction, and the rolling stands 12a are shifted by 60 ° between adjacent stands.

  In order to manufacture a tube without uneven thickness, it is necessary that the rolling rolls in each stand are appropriately arranged. However, since the rolling position of a part of the rolling rolls constituting the mandrel mill is shifted from the proper arrangement in the rolling direction and / or the axial direction of the roll, uneven thickness occurs.

  When a two-roll type mandrel mill is used, if the distance between the opposing rolling rolls is reduced in one stand and the distance between the opposing rolling rolls is increased in the adjacent stand, secondary uneven thickness tends to occur. When the distance between the rolling rolls in the stand is narrowed or widened, the fourth thickness unevenness tends to occur. Since the two rolling rolls are opposed to each other, it is easy to adjust the rolls so as not to cause an axial displacement.

  From the above tendency, in the case of a two-roll type mandrel mill, the occurrence state of secondary wall thickness deviation or quaternary wall thickness deviation of the pipe after rolling is investigated, and feedback control is performed based on the result to determine an appropriate rolling position. It becomes possible to produce a pipe without any deviation in thickness.

  On the other hand, in the case of a three-roll type mandrel mill, since the number of rolling rolls increases, the degree of freedom of the positional relationship between the rolls increases, and it becomes difficult to control the rolling position. In addition, with the change in the roll down position of each roll, not only the tertiary thickness variation or the 6th thickness variation, but also the secondary thickness variation or the quaternary thickness variation may occur. The correspondence with the uneven thickness state becomes more complicated.

  The wall thickness of the pipe is determined by the outer diameter of the mandrel bar used, the roll hole diameter of the mandrel mill, and the distance between the mandrel bar and the mandrel. It is not practical to change the mandrel bar and the mandrel mill every time uneven thickness occurs, from the viewpoint of productivity. Therefore, it is necessary to eliminate uneven thickness by adjusting the rolling position of each rolling roll of the mandrel mill to an appropriate arrangement and changing the interval between the mandrel bar and the mandrel mill.

  For example, in Patent Document 1, the thickness of twelve materials to be rolled, which is a position corresponding to a portion shifted from the groove bottom of each rolling roll to both flange portions, is measured, and each rolling is performed based on the measured value. A method for adjusting the rolling position of a rolling roll for adjusting the rolling position of the roll is disclosed.

JP 2005-131706 A

Yutaka Funao, Sei Okumura, Itsuo Matsuoka, Shoichi Murakami, Development of Hot Thickness Gage for Seamless Steel Pipe, Kawasaki Steel Engineering Reports, 1982, Vol. 14, No. 2, p. 156-164

  FIG. 4 is a diagram schematically illustrating an example of a seamless tube rolling device. The rolling device includes a three-roll type mandrel mill 12 and a mandrel bar 11 in which a plurality of stands having three rolling rolls 12a are arranged side by side in the traveling direction of the tube. Further, between the adjacent stands, the rolling directions of the rolling rolls 12a are shifted from each other by approximately 60 °.

  FIG. 5 is a diagram showing a cross section of the mandrel bar 11 and the three rolling rolls 12 a in a direction perpendicular to the axial direction of the mandrel bar 11. As schematically shown in FIG. 5, deviation in the rolling position of each rolling roll from an appropriate arrangement causes uneven thickness.

  Therefore, by grasping the state of uneven wall thickness, that is, the wall thickness distribution after processing, it is possible to determine the deviation in the roll axis direction and the roll reduction direction of the rolling roll. In order to grasp the wall thickness distribution of the pipe, it is ideal to continuously measure the wall thickness over the entire circumference of the pipe. However, it is difficult to continuously measure the wall thickness of the tube during hot working. Therefore, in order to grasp the thickness distribution, a method of discretely measuring a plurality of locations over the entire circumference in the circumferential direction using a thickness measuring device using gamma rays has been used (see Non-Patent Document 1). ).

  FIG. 6 is a schematic diagram for explaining an example of the configuration of the γ-ray thickness gauge 14. In the configuration shown in FIG. 6, it is possible to measure the thickness at nine locations in the circumferential direction. The γ-ray thickness gauge 14 detects γ-rays emitted from the γ-ray source 14a with the γ-ray detector 14b, and measures the thickness of the cross section of the tube that has passed from the amount of γ-ray attenuation. At this time, since γ-rays pass through two places in the cross section of the tube, the total thickness of the two places is obtained. However, since γ-rays emitted from two directions per one place in the cross-section of the tube pass through, The thickness at each location can be determined.

  Here, as shown in FIG. 7, in order to determine the shift in the roll axis direction and the roll reduction direction of the rolling roll, the wall thickness is measured at at least two places in a portion of the pipe corresponding to the rolling roll, and the thickness thereof is measured. It is necessary to calculate the deviation. Further, at a position away from the groove bottom, the curvature of the rolling roll deviates from a certain range, resulting in a large error in the calculation result. Therefore, it is necessary to measure the wall thickness of the pipe at a plurality of positions corresponding to the vicinity of the groove bottom. Therefore, in the case of a three-roll type mandrel mill, if the wall thickness can be measured at a total of 12 locations at two locations at positions corresponding to the vicinity of the groove bottom of six rolling rolls, it is possible to calculate an appropriate rolling position of all the rolling rolls. Becomes

  However, when the above-mentioned gamma ray thickness meter is used, if the number of the measurement points is even, the thickness cannot be calculated, so that the number must be odd (for example, see Non-Patent Document 1). ). Therefore, as described in Patent Literature 1 using a gamma-ray thickness gauge, measurement of the thickness of twelve locations, which is a position corresponding to a portion shifted from the groove bottom of each rolling roll to both flange portions simply. There is a problem that can not be performed.

  An object of the present invention is to provide a pipe thickness measuring device and a wall thickness measuring method capable of accurately grasping the uneven thickness state of a pipe.

  The present invention has been made in order to solve the above-mentioned problems, and has a gist and apparatus for measuring a wall thickness of a pipe described below.

(1) In a section perpendicular to the axial direction of a tube to be measured, k radiation sources for emitting a radiation beam and k detectors to which the radiation beam is incident are provided outside the tube. Arranged alternately along one direction in the circumferential direction of the tube,
An apparatus for measuring the thickness of a tube based on the intensity of a radiation beam emitted from the radiation source, transmitted through the tube, and incident on the detector,
The k radiation sources and the k detectors are:
A radiation beam emitted from each radiation source is incident on the (k + 1) / 2-th detector from the radiation source in the one direction,
A radiation beam emitted from the radiation source and a radiation beam incident on a first detector in the one direction of the radiation source intersect at an intersection within a thick portion of the tube;
The radiation beams emitted from the k radiation sources form the k intersections in the thick portion,
Are arranged such that a regular k-sided polygon is formed when the adjacent intersections are connected by a straight line,
The above-mentioned k is a pipe wall thickness measuring device satisfying the following formula (i).
k = 6n + 3 (i)
Here, n is a natural number of 2 or more.

(2) A three-roll mandrel mill in which a plurality of stands having three rolling rolls are arranged side by side in the traveling direction of the pipe, and between the adjacent stands, the rolling direction of the rolling rolls is shifted by approximately 60 °, and The tube thickness measuring device according to (1), wherein the thickness of the tube rolled by a rolling device including a mandrel bar extending in a traveling direction of the tube is measured.
In a virtual coordinate plane perpendicular to the axial direction of the mandrel bar and having the origin at the center of the mandrel bar, when the direction extending from the origin to the groove bottom of one rolling roll is defined as the reference direction, An apparatus for measuring the thickness of a pipe, wherein an angle between a direction and a direction extending from the origin to each of the thickness measurement points satisfies the following expression (ii).
θ ₁ ⁱ = (2π / k) i−π / 2k (i = 1, 2,..., k) (ii)
Here, θ ₁ ⁱ means an angle between the reference direction and a direction extending from the origin to the i-th thickness measuring point, and the unit is radian, where counterclockwise is positive.

(3) In a section perpendicular to the axial direction of the tube to be measured, k radiation sources for emitting a radiation beam and k detectors to which the radiation beam is incident are provided outside the tube. Alternately arranged along one direction in the circumferential direction of the pipe,
A method of measuring the thickness of a tube based on the intensity of a radiation beam emitted from the radiation source, transmitted through the tube, and incident on the detector,
A radiation beam is emitted from each radiation source, and is incident on the (k + 1) / 2-th detector from the radiation source in the one direction,
A radiation beam emitted from the radiation source and a radiation beam incident on a first detector in the one direction of the radiation source intersect at an intersection within a thick portion of the tube;
The radiation beams emitted from the k radiation sources form the k intersections in the thick portion,
To form a regular k-sided polygon when connecting the adjacent intersections with a straight line,
Arranging the k radiation sources and the k detectors,
A method for measuring the wall thickness of a pipe, wherein k is set so as to satisfy the following equation (i).
k = 6n + 3 (i)
Here, n is a natural number of 2 or more.

(4) A three-roll type mandrel mill in which a plurality of stands having three rolling rolls are arranged side by side in the traveling direction of the pipe, and a rolling direction of the rolling rolls is shifted by approximately 60 ° between adjacent stands, and The method for measuring the wall thickness of a pipe according to the above (3), wherein the wall thickness of the pipe rolled by a rolling device having a mandrel bar extending in the traveling direction of the pipe is measured.
In a virtual coordinate plane perpendicular to the axial direction of the mandrel bar and having the origin at the center of the mandrel bar, when the direction extending from the origin to the groove bottom of one rolling roll is defined as the reference direction, A method for measuring the wall thickness of a pipe, wherein an angle formed between the direction and a direction extending from the origin to each of the thickness measurement points satisfies the following equation (ii).
θ ₁ ⁱ = (2π / k) i−π / 2k (i = 1, 2,..., k) (ii)
Here, θ ₁ ⁱ means an angle between the reference direction and a direction extending from the origin to the i-th thickness measuring point, and the unit is radian, where counterclockwise is positive.

  According to the present invention, the thickness of the pipe can be measured at a plurality of locations at positions corresponding to the respective rolling rolls, so that it is possible to accurately grasp the uneven wall thickness of the pipe after rolling.

It is the figure which showed an example of the manufacturing process of the seamless pipe. It is a figure for explaining the shape of various uneven thickness. It is the figure which showed the mandrel bar and the mandrel mill seen in the pipe axis direction. It is the figure which showed an example of the rolling device schematically. It is a figure showing a section of a mandrel bar and a roll. It is a schematic diagram for explaining an example of composition of a gamma ray thickness meter. It is a figure explaining the method of calculating the deviation of the thickness in two places of the part corresponding to a rolling roll. It is a schematic diagram of a wall thickness measuring device concerning one embodiment of the present invention. It is the figure which showed the cross section of the mandrel bar and the rolling roll in a virtual coordinate plane, and the thickness measurement location. It is the figure which showed the angle which the direction which extends from the origin to each thickness measurement location and the direction which extends to the groove bottom part of each rolling roll forms. It is the figure which showed the angle which the direction which extends from the origin to each thickness measurement location and the direction which extends to the groove bottom part of each rolling roll forms. It is the figure which showed the cross section of the mandrel bar and the rolling roll in a virtual coordinate plane, and the thickness measurement location. It is the figure which showed the angle which the direction which extends from the origin to each thickness measurement location and the direction which extends to the groove bottom part of each rolling roll forms. It is the figure which showed the cross section of the mandrel bar and the rolling roll in a virtual coordinate plane, and the thickness measurement location. It is the figure which showed the angle which the direction which extends from the origin to each thickness measurement location and the direction which extends to the groove bottom part of each rolling roll forms. It is the figure which showed the cross section of the mandrel bar and the rolling roll in a virtual coordinate plane, and the thickness measurement location. It is the figure which showed the angle which the direction which extends from the origin to each thickness measurement location and the direction which extends to the groove bottom part of each rolling roll forms. It is the figure which showed the angle which the direction which extends from the origin to each thickness measurement location and the direction which extends to the groove bottom part of each rolling roll forms. It is the figure which showed the angle which the direction which extends from the origin to each thickness measurement location and the direction which extends to the groove bottom part of each rolling roll forms. It is the figure which showed the angle which the direction which extends from the origin to each thickness measurement location and the direction which extends to the groove bottom part of each rolling roll forms. It is the figure which showed the maximum value of the angle from the groove bottom part of each rolling roll to the 1st measurement point and the 2nd measurement point.

  FIG. 8 is a schematic diagram of a thickness measuring device 14 according to an embodiment of the present invention. The wall thickness measuring device 14 has, on a cross section perpendicular to the axial direction of the tube 10 to be measured, k radiation sources 14a for emitting a radiation beam outside the tube 10 and k radiation sources 14a for receiving the radiation beam. Detectors 14b are alternately arranged along one direction A in the circumferential direction of the tube 10, and the intensity of the radiation beam emitted from the radiation source 14a, transmitted through the tube 10, and incident on the detector 14b is reduced. The thickness of the pipe 10 is measured based on the measurement. Note that k is 15 in the example shown in FIG.

  The radiation source 14a and the detector 14b are arranged so as to satisfy the following conditions (a) to (c).

(A) a radiation beam emitted from each radiation source in one direction A from the radiation source _{14a 1, (k + 1)} / ( in the example shown in FIG. 8, 8 th) 2 -th detector 14b of ₈ is incident.

(B) a radiation beam emitted from the radiation source 14a _1, the radiation beam and is that in one direction A of the radiation source 14a ₁ is incident on the 1 th detector 14b _1, intersections in the thickness portion of the tube intersect to form a B _1.

  (C) The radiation beams emitted from the k radiation sources 14a form k intersections in the thick portion of the tube 10, and form a regular k-sided polygon when adjacent intersections are connected by a straight line (see FIG. 8). In the example, a regular pentagon is formed.

Further, the number k of radiation sources and detectors, that is, the number of wall thickness measurement points must be secured at two or more positions at positions corresponding to each rolling roll, and must be an odd number. Must. In addition, from the viewpoint of analysis accuracy, the number of the thickness measurement points is preferably as large as possible. In order to achieve both analytical accuracy and economy, in the present invention, the number k of radiation sources and detectors must satisfy the following expression (i).
k = 6n + 3 (i)
Here, n is a natural number of 2 or more.

  The reason why the number of k needs to satisfy the above equation (i) will be described in detail below.

FIG. 9 is a diagram showing a cross section of the mandrel bar and the six rolling rolls and a wall thickness measurement point on a virtual coordinate plane perpendicular to the axial direction of the mandrel bar and having the origin at the center of the mandrel bar. It is. R1~R6 in the figure indicates the direction extending groove bottom portion of each rolling roll from the origin, M ₁ ~M ₁₃ indicates the direction extending wall thickness measurement points from the origin. In the figure, the direction of R6 is the reference direction.

The angle formed between the reference direction and the direction extending from the origin to each thickness measurement point on the coordinate plane shown in FIG. 9 is expressed by the following equation (iii), and extends from the reference direction and the origin to the groove bottom of each rolling roll. The angle formed with the direction is represented by the following equation (iv). Note that the angle formed with the reference direction is positive in a counterclockwise direction, and the unit is radian.
θ ₁ ⁱ = (2π / k) i + δ (i = 1, 2,..., k) (iii)
θ ₂ ^j = (2π / 6) j (j = 1, 2,..., 6) (iv)

In the arrangement shown in FIG. 9, the thickness measurement locations are 13 locations (k = 13), and the direction (M ₁₂ ) of the _twelfth thickness measurement location is the same as the direction (R6) of the groove bottom of the sixth rolling roll. They are arranged to match. That, | a ^{_{= 0 | θ 1 12 -θ 2}} 6.

  FIG. 10 is a diagram showing an angle formed between the direction of each thickness measurement point and the direction of the groove bottom of each rolling roll in the above arrangement. FIG. 11 is a view showing the angle formed by the direction of each of the above-mentioned thickness measurement points and the direction of the groove bottom of each rolling roll limited to a range of 30 ° or less.

As can be seen from FIG. 11, it is possible to measure the thickness at two or more locations at the position corresponding to each rolling roll, but for the sixth rolling roll 12a ₆ , the first measuring location is the groove. Although on the bottom, the second measurement point is more than 25 ° away from the groove bottom.

In addition, the thickness measurement points were rotated so that the maximum value of the angle formed between the direction of each thickness measurement point and the direction of the groove bottom of each rolling roll was adjusted to be the smallest in the arrangement shown in FIG. is there. As shown in FIG. 12, the angle formed by the direction (M ₁₀ ) of the _tenth thickness measurement point and the direction (R5) of the groove bottom of the fifth rolling roll, and the direction of the twelfth thickness measurement point ( M ₁₂₎ and sixth direction of the groove bottom of the rolling roll (R6) is an angle formed is rotating to be equal. ^{_{That, | θ 1 10 -θ 2 5}} | = | θ 1 12 -θ 2 6 | become.

FIG. 13 is a diagram showing an angle formed between the direction of each thickness measurement point and the direction of the groove bottom of each rolling roll in the above arrangement. As can be seen from FIG. 13, in addition to the _sixth rolling roll 12a6, the fifth rolling roll also resulted in the second measurement point being separated from the groove bottom by 25 ° or more.

Similarly, in the arrangement shown in FIG. 14, the thickness measurement points are 15 (k = 15), and the direction of the _fourteenth thickness measurement point (M ₁₄ ) is the direction of the groove bottom of the sixth rolling roll. It is arranged so as to coincide with (R6). That, | a ^{_{= 0 | θ 1 14 -θ 2}} 6.

  FIG. 15 is a diagram showing an angle formed between the direction of each thickness measurement point and the direction of the groove bottom of each rolling roll in the above arrangement. As can be seen from FIG. 15, it was possible to secure two measurement points within a range of 25 ° from the groove bottom at positions corresponding to all the rolling rolls.

Further, the thickness measurement points were rotated so that the maximum value of the angle formed between the direction of each thickness measurement point and the direction of the groove bottom of each rolling roll was adjusted to be the smallest, with the arrangement shown in FIG. is there. As shown in FIG. 16, the angle formed by the direction (M ₁₁ ) of the _eleventh thickness measurement point and the direction (R5) of the groove bottom of the fifth rolling roll and the direction of the fourteenth thickness measurement point ( M ₁₄ ) and the sixth roll are rotated so that the angle formed by the direction (R6) of the groove bottom of the roll becomes equal. ^{_{That, | θ 1 11 -θ 2 5}} | = | θ 1 14 -θ 2 6 | become.

  FIG. 17 is a diagram showing an angle formed between the direction of each thickness measurement point and the direction of the groove bottom of each rolling roll in the above arrangement. As can be seen from FIG. 17, it was possible to secure two measurement points within a range of 20 ° from the groove bottom at positions corresponding to all the rolling rolls.

  FIGS. 18 to 20 are diagrams showing angles formed by the direction of each thickness measurement point and the direction of the groove bottom of each rolling roll when the number k of the thickness measurement points is 17, 19, and 21, respectively. In each of the results, the maximum value of the angle formed between the direction of each thickness measurement point and the direction of the groove bottom of each rolling roll was adjusted to be the smallest.

  FIG. 21 summarizes the above results, and shows the case where the number k of the thickness measurement points is 13 to 21 from the groove bottom of each rolling roll to the first measurement point and the second measurement point. It is a figure showing the maximum value of an angle.

  As can be seen from FIG. 21, when k is 15, the angle of the rolling roll from the groove bottom is greatly reduced as compared to when k is 13. In addition, when k was 17 or 19 as compared to when k was 15, the angle of the rolling roll from the groove bottom increased despite the number of measurement points being increased. When k was 21, the angle of the rolling roll from the groove bottom greatly decreased.

The present inventor has further studied based on the above-mentioned new knowledge, and under the condition satisfying the following equation (A), the maximum value of the angle formed between the direction of each thickness measurement point and the direction of the groove bottom of each rolling roll. We investigated about the condition that minimizes.
k = 6n + m (A)
Here, n is a natural number of 2 or more, and m is -1, 1 or 3.

From the above results, when k satisfies the following expression (i), it is possible to measure the wall thickness near the groove bottom of the rolling roll, and to accurately displace each rolling roll in the roll axis direction and the roll reduction direction. It turned out that we could ask for.
k = 6n + 3 (i)
Here, n is a natural number of 2 or more.

  As described above, if the number of locations where the thickness is measured is increased, the analysis accuracy is improved, but the economic efficiency is reduced. In consideration of the balance, the value obtained by multiplying the maximum value of the angle from the groove bottom of each rolling roll to the second closest measurement point by the number k of the thickness measurement points (hereinafter referred to as I) is analyzed accuracy. We consider it as an index to achieve both economy and economy.

  When k was 13, 17, and 19, the value of I was 11π / 6 (rad). On the other hand, when k was set to 15 and 21, so that the above equation (i) was satisfied, the value of I was 3π / 2 (rad). From the above results, it can be seen that when the number k of the thickness measurement points satisfies the above expression (i), both analysis accuracy and economy can be achieved.

Further, in order to adjust the maximum value of the angle formed by the direction of each thickness measurement point and the direction of the groove bottom of each rolling roll to be the smallest, when the above expression (i) is satisfied, the above ( iii) It is preferable to set δ in the formula to −π / 2k. That is, it is preferable to satisfy the following expression (ii).
θ ₁ ⁱ = (2π / k) i−π / 2k (i = 1, 2,..., k) (ii)
Here, θ ₁ ⁱ means an angle between the reference direction and a direction extending from the origin to the i-th thickness measuring point, and the unit is radian, where counterclockwise is positive.

  According to the present invention, the thickness of the pipe can be measured at a plurality of locations at positions corresponding to the respective rolling rolls, so that it is possible to accurately grasp the uneven wall thickness of the pipe after rolling.

10. Hollow shell 11. Mandrel bar 12. Mandrel mill 12a. Rolling roll 12b. Groove bottom 13. Sizer 14. Thickness measuring device 14a. Radiation source 14b. Detector

Claims (4)

A plurality of stands having three rolling rolls are arranged side by side in the traveling direction of the pipe, and a three-roll type mandrel mill in which the rolling direction of the rolling roll is shifted by approximately 60 ° between adjacent stands, A device for measuring the wall thickness of a tube rolled by a rolling device having a mandrel bar extending in the direction,
In a cross section perpendicular to the axial direction of the tube to be measured, on the outside of the tube, k radiation sources for emitting a radiation beam and k detectors to which the radiation beam is incident are provided. Are arranged alternately along one direction in the circumferential direction,
An apparatus for measuring the thickness of a tube based on the intensity of a radiation beam emitted from the radiation source, transmitted through the tube, and incident on the detector,
The k radiation sources and the k detectors are:
A radiation beam emitted from each radiation source is incident on the (k + 1) / 2-th detector from the radiation source in the one direction,
A radiation beam emitted from the radiation source and a radiation beam incident on the first detector in the one direction of the radiation source intersect at an intersection within a thick portion of the tube;
The radiation beams emitted from the k radiation sources form the k intersections in the thick portion,
Are arranged such that a regular k-sided polygon is formed when the adjacent intersections are connected by a straight line,
The above-mentioned k is a pipe thickness measuring device satisfying the following formula (i).
k = 6n + 3 (i)
Here, n is a natural number of 2 or more. A thickness measuring apparatus of the tubes according to 請 Motomeko 1,
In a virtual coordinate plane perpendicular to the axial direction of the mandrel bar and having the origin at the center of the mandrel bar, when the direction extending from the origin to the groove bottom of one rolling roll is defined as the reference direction, An apparatus for measuring the thickness of a pipe, wherein an angle between a direction and a direction extending from the origin to each of the thickness measurement points satisfies the following expression (ii).
θ ₁ ⁱ = (2π / k) i−π / 2k (i = 1, 2,..., k) (ii)
Here, θ ₁ ⁱ means an angle between the reference direction and a direction extending from the origin to the i-th thickness measuring point, and the unit is radian, where counterclockwise is positive. A plurality of stands having three rolling rolls are arranged side by side in the traveling direction of the pipe, and a three-roll type mandrel mill in which the rolling direction of the rolling roll is shifted by approximately 60 ° between adjacent stands, A method of measuring the wall thickness of a tube rolled by a rolling device having a mandrel bar extending in the direction,
In a cross section perpendicular to the axial direction of the tube to be measured, on the outside of the tube, k radiation sources for emitting a radiation beam, and k detectors to which the radiation beam is incident, are provided. Arranged alternately along one direction in the circumferential direction,
A method of measuring the thickness of a tube based on the intensity of a radiation beam emitted from the radiation source, transmitted through the tube, and incident on the detector,
A radiation beam is emitted from each radiation source, and is incident on the (k + 1) / 2-th detector from the radiation source in the one direction,
A radiation beam emitted from the radiation source and a radiation beam incident on a first detector in the one direction of the radiation source intersect at an intersection in a thick portion of the tube;
The radiation beams emitted from the k radiation sources form the k intersections in the thick portion,
To form a regular k-sided polygon when connecting the adjacent intersections with a straight line,
Arranging the k radiation sources and the k detectors,
A method for measuring the wall thickness of a pipe, wherein k is set so as to satisfy the following equation (i).
k = 6n + 3 (i)
Here, n is a natural number of 2 or more. A thickness measuring method of a tube according to 請 Motomeko 3,
In a virtual coordinate plane perpendicular to the axial direction of the mandrel bar and having the origin at the center of the mandrel bar, when the direction extending from the origin to the groove bottom of one rolling roll is defined as the reference direction, A method for measuring the wall thickness of a pipe, wherein an angle formed between the direction and a direction extending from the origin to each of the thickness measurement points satisfies the following equation (ii).
θ ₁ ⁱ = (2π / k) i−π / 2k (i = 1, 2,..., k) (ii)
Here, θ ₁ ⁱ means an angle between the reference direction and a direction extending from the origin to the i-th thickness measuring point, and the unit is radian, where counterclockwise is positive.

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