JPH06160068A - Radiation transmission type measuring method for thickness of pipe-like material - Google Patents

Abstract

PURPOSE:To control measuring errors caused by decentering, a center deviation and outer diameter variation of a pipe-like material by measuring the center deviation and outer diameter of the pipe-like material, finding values of an outer radius center position and an outer radius and furthermore discovering thickness from the other values of an inner radius and an inner radius center position. CONSTITUTION:A pipe like material P is carried in the direction of an arrow mark F with a carrying roller 5 driven with a drive motor 6. A pulse generator 8 is connected to a shaft 9 of the drive motor 6 and an outer diameter measuring value is tracked up to a thickness measuring point. A thickness measuring device 20 composed of a laser type center deviation and outer diameter measuring device 10 constituted of four light casting devices and a light receiving device and three groups of radiation transmission type thickness gages narrows distance L as close as possible and is provided. When measuring signals transmitted from the generator 8, the measuring device 10 and the other measuring device 20 are input to an operation device 30, the operation device 30 serves to find a coordinate of an outer radius center point and the outer radius from the center deviation and the outer diameter of the pipe-like material P really measured with the measuring device 10 and correct a really measured value determined with the other measuring device 20 by means thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation transparent wall thickness measuring method for tubular materials.

[0002]

2. Description of the Related Art Conventionally, as a means for measuring the wall thickness (hereinafter simply referred to as wall thickness) of a seamless steel pipe or the like in the hot state of Azroll, for example, as disclosed in Japanese Patent Publication No. 44602/1985. There is a wall thickness measuring method. Here, the contents of the above Japanese Patent Publication No. 60-44602 will be described below. First, the principle will be described with reference to FIG. 5. In the case where the wall thickness dimensions t ₁ , t ₂ and t ₃ at points A, B and C that divide the pipe circumference in the cross section of the tubular material P into three equal parts are obtained by measurement. , A radiation source 1 for emitting a measurement radiation beam 3, a radiation source container 2 for accommodating the radiation source 3 for directing the radiation beam 3 in a predetermined direction, and a tubular member P. A measurement system including a detector 4 for detecting the radiation beam transmitted through the tube wall is provided. Each code numeral is suffixed with the letters A, B or C representing the measurement system to which it belongs. Also, the detector 4 for the beam that has passed through the tube wall
The detection outputs from A to 4C are I ₁ to I _3, and the detection outputs when there is no tube wall are I _1O and I, respectively.
_2O and I _3O .

Therefore, between the output I of the detector 4 and the wall thickness dimension t, the following relational expression is established as a basic expression of a general radiation transmission type thickness gauge. I ₁ = I _1O exp {−μk (t ₁ + t ₃ )} ………… (1) I ₂ = I _2O exp {−μk (t ₂ + t ₁ )} ………… (2) I ₂ = I _3O exp {-μk (t ₃ + t ₂ )} ………… (3) where μ is the linear absorption coefficient of the radiation used for the tube wall material, and k is the tube wall of the radiation beam passing through the measurement point. It is a value obtained by dividing the transmission length S by the wall thickness dimension t at that point. If the angle θ between the transmission direction of the radiation beam and the diameter direction of the tubular member at the measurement point is zero, k becomes 1.

When the above equations (1) to (3) are used as simultaneous equations and the solution is obtained, the equations (4) to (6) are obtained.

[0005]

[Equation 1]

Therefore, the detector output I of the radiation beam
_The wall thickness dimensions t ₁ , t ₂ and t ₃ can be calculated from _1O , I ₁ , I _2O , I ₂ , I _3O and I ₃ and the constants μ and k. Although the above description has been made on the case of three measurement points, in general, the above-mentioned measurement method can be extended to the case of n measurement points. That is, assuming that the wall thickness dimensions at the n measurement points are t ₁ , t ₂ , ... T _n , a constant relational expression (simultaneous equations) that cyclically changes between the respective thickness dimensions, such as equation (7). Is established. This relational expression is obtained by logarithmically converting the above expressions (1) to (3).

[0007]

[Equation 2]

By the way, although the above-mentioned coefficient k (= S / t) can be known in advance, it is very difficult to consider it strictly, so in the above Japanese Patent Publication No. 60-44602,
The thickness in the oblique direction is measured using the following procedure. That is, as shown in FIG. 6, the radius dimension of the average outer diameter centering on the point O of the measurement points A, B, C of the tubular material P is R _o, and similarly, the radius dimension of the average inner diameter is R _i, the intersection a of the radiation beam, B, the radius of the virtual true circle D that put C on the circumference and R _c, and each radiation beam 3A, 3B, 3C the measuring points a, B, and C If the diagonal thicknesses along each beam when passing are ξ ₁ , ξ ₂ , and ξ ₃ , and the triangle ΔABC with the measurement points A, B, and C as vertices is an equilateral triangle, The measured values are three quantities d ₁₂ , d ₂₃ and d _{31 in} the following formula.

Ξ ₁ + ξ ₂ = d ₁₂ (8) ξ ₂ + ξ ₃ = d ₂₃ (9) ξ ₃ + ξ ₁ = d ₃₁ (10) From the equation, ξ ₁ , ξ ₂ , and ξ ₃ can be theoretically accurately and easily solved as follows.

Ξ ₁ = (d ₁₂ −d ₂₃ + d ₃₁ ) / 2 (11) ξ ₂ = (d ₂₃ −d ₃₁ + d ₁₂ ) / 2 (12) ξ ₃ = (D ₃₁ −d ₁₂ + d ₂₃ ) / 2 (13) Then, the wall thickness dimensions t ₁ , t ₂ , t ₃ of the tubular material P at the measurement points A, B, C are calculated by the following equations. You can ask for it.

T ₁ = R _o −√ {R _o ² − (A−ξ ₁ ) ξ ₁ } ... (14) t ₂ = R _o −√ {R _o ² − (A−ξ ₂ ). ξ ₂ } ……………… (15) t ₃ = R _o −√ {R _o ² − (A−ξ ₃ ) ξ ₃ } ………… (16) However, A = 2√ {R _o ² − (R _c sin θ) ² } (17) In this case, the angle θ is given as π / 6.

[0012]

However, in the above-described measuring method, the eccentricity and the runout of the tubular member P,
Alternatively, there is a drawback that a large measurement error occurs when there is a variation in the outer diameter. That is, as shown in FIG. 7, the outer radius center position O of the tubular member P is displaced from the measurement center position O ′ by a distance f due to center runout, or the outer radius center position O and the inner radius center position O ″ are decentered. Assume that and are displaced by a distance g.

Therefore, a geometrical perpendicular line is drawn from the original center point O to each of the radiation beams 3A, 3B, 3C, and their lengths are set to h ₁ , h ₂ , and h ₃ , respectively, and the respective radiation beams form a tube wall. The wall thickness at the passing position is t ₁₂ , t ₁₃ ,
Assuming t ₂₁ , t ₂₃ , t ₃₁ , and t ₃₂ , the above equation (7) can be expressed as equation (18).

[0014]

[Equation 3]

In these equations, the unknowns are t ₁₂ to t _32.
Since there are 3 equations for 6 of the above, it cannot be solved as it is. Therefore, as is clear from the above equations (14) to (16),

[0016]

[Equation 4]

As a result, it is decided to seek. That is,
This means that the uneven thickness caused by the eccentricity g is ignored.
Further, by using the nominal outer diameter D ₀ and the nominal wall thickness t ₀ , it follows that h ₁ = h ₂ = h ₃ = (D ₀ −t ₀ ) / 4 (20) This means that the error due to the shake f is ignored.

Furthermore, since the radius R _o of the outer diameter is used as _{R o = D 0/2 ...............} (21), so that ignoring the error factors due to the outer diameter fluctuation. According to the result of simulation by the inventor, the measurement error of the eccentricity ratio due to the eccentricity is several%, and the influence of the center runout is, for example, ± 10 mm, and the thickness error is several mm, and the eccentricity ratio is The error is several 10%,
Further, regarding the outer diameter variation, it has been confirmed that, for example, in the case of a variation of ± 20 mm, the thickness error is several mm and the uneven thickness ratio error is several tens%. Here, the uneven thickness ratio is (maximum wall thickness-
It is an index expressed by (minimum wall thickness) x 100 / average wall thickness (%).

It is an object of the present invention to provide a radiation transmission type wall thickness measuring method for a tubular material, which solves the above problems of the prior art.

[0020]

The present invention comprises at least 3
The radiation beams of the book intersect with each other, and the beams are projected so that regular polygons are formed with the intersections as vertices, and the vertices of the polygons are all included in the thick portion of the tubular material. The tubular material is positioned, the intensity of the radiation beam after passing through the thick portion of the tubular material is measured, and the thickness of the tubular material at the position of the apex of the polygon is measured from the measured value. In a radiation transmission type wall thickness measuring method for a tubular material, which is obtained by calculation as a wall thickness, a step of actually measuring the core runout and the outer diameter of the tubular material to obtain the outer radius center position and the value of the outer radius, and the obtained outer radius. Using the center position and the outer radius value to determine the inner radius value and the inner radius center position, and using the obtained outer radius center position and the outer radius value and the inner radius center position and the inner radius value of each pipe wall Characterized by the addition of a process to determine the wall thickness A radiation transmissive wall thickness measurement method of the tubular member to be.

[0021]

[Operation] According to the present invention, since the function of correcting the eccentricity and the center runout of the tubular material is added to the conventional radiation transmission type wall thickness measuring method, It is possible to suppress the measurement error.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a plan view showing an embodiment of the present invention. In the figure, 5 is a conveyance roller that conveys the tubular material P in the direction of the arrow F, 6 is a drive motor that drives the conveyance roller 5 via a rotary shaft 7, and 8 is a shaft 9 of the drive motor 6.
Is a pulse oscillator coupled to. This pulse transmitter 8
Has a function of tracking the measured value of the outer diameter up to the wall thickness measurement point.

Further, 10 is, for example, four light projectors 11, 12, 13 and 14 shown in FIG. 2 and four light receivers 15, 16 provided respectively facing these light projectors 11, 12, 13 and 14. 17, 18
Laser transmission type core runout / outer diameter measuring device consisting of
20 is a wall thickness measuring device consisting of three sets of radiation transmission type thickness gauges shown in FIG. 4, 30 is a pulse transmitter 8, core runout / outer diameter measuring device 10, and measurement signals from the wall thickness measuring device 20. Is a calculation device for calculating the wall thickness of the tubular material P by inputting.

Here, it is assumed that the distance L between the runout / outer diameter measuring device 10 and the wall thickness measuring device 20 is as close as possible. As a result, the runout of the tubular material P can be regarded as the same between both devices. The calculation procedure of the wall thickness of the tubular material P having the nominal outer diameter D ₀ and the nominal wall thickness t ₀ by the calculation device 30 will be described with reference to FIGS. 3 and 4. First, in FIG. 3, by measuring the core runout and the outer diameter of the tubular material P by the core runout / outer diameter measuring device 10, the coordinates (x _o , y _o ) of the outer radius center point O _o and the outer radius R are measured.
ask for _o . Coordinates (x _o , y _o ) of the obtained outer radius center point O _o
And the outer radius R _o , the transmission lengths l ₁ , l ₂ and l ₃ of the radiation beams 3A, 3B and 3C which are transmitted through the tube wall are given by (2
Geometrically determined by the formula (2).

[0025]

[Equation 5]

Further, each of the radiation beams 3A, 3B,
Transmission amount of 3C I₁, I₂, I₃By measuring
The radiation beams 3A, 3B, 3C other than the tube wall.
Excessive length m ₁, m₂, m₃Is calculated by the following formula (23).

[0027]

[Equation 6]

On the other hand, the coordinates (x _i , y _i ) of the center point O _i of the inner radius geometrically satisfy the following equations (24), (25), (26). Here, R _i is the inner radius.

[0029]

[Equation 7]

However, since it is difficult to understand as it is,
As a similar solution, x in equation (26)_i→ x_o, Y_i→ y_oWhen
Then R_iThen, from equations (24) and (25), y_iAnd x_iTo
Ask. X obtained_o, Y_o, R_oAnd x_i, Y_i, R_iAnd
And the arrangement of each radiation beam 3A, 3B, 3C
From the viewpoint of wall thickness t of 6 points on each tube wall₁₂, T₁₃, T_{twenty one}, T _{twenty three}, T
₃₁, T₃₂Ask for.

That is, in FIG. 4, the x-axis and the y-axis are measured.
Radiation is assumed to cross at the coordinates (0,0) of the constant center point O
When the line beams 3A, 3B and 3C pass through the tubular material P,
Each intersection P with the inner wall₁₂, P₁₃, P_{twenty one}, P_{twenty three}, P₃₁, P₃₂
The coordinates of (x₁₂, Y ₁₂), (X₁₃, Y₁₃),
(X_{twenty one}, Y_{twenty one}), (X_{twenty three}, Y_{twenty three}), (X₃₁, Y₃₁),
(X₃₂, Y₃₂), The respective coordinates are as follows.
You can ask.

First, the equation of the straight line of the radiation beams 3A, 3B and 3C can be expressed by the following equation calculated from its geometrical position. _{y = √3x + (D o -t} o) / 2 ............... (27) y = -√3x + (D o -t o) / 2 ............... (28) y = - (D o - t _o ) / 2 (29) Further, the relationship between the inner radius R _i and x _i , y _i is expressed by the following formula (30).

(X−x _i ) ² + (y−y _i ) ² = R _i ² (30) Therefore, the coordinates (x ₁₂ , y ₁₂ ) at the intersection points P ₁₂ , P ₁₃ of the radiation beam 3A. ), (X ₁₃ , y ₁₃ )
From the two expressions (27) and (30), the intersection point P _{21 of} the radiation beam 3B,
Coordinates of _{P 23 (x 21, y 21} ), (x 23, y 23) above (28) for, (30) from the intersection P ₃₁ of the radiation beam 3C, the coordinates in the P ₃₂ (x _31, y ₃₁ ) and (x ₃₂ , y ₃₂ ) are obtained from the above equations (29) and (30), respectively.

Next, regarding the wall thickness of the pipe wall,
Intersection P₁₂Thickness t at₁₂Is calculated using the following equation (31).
Can be turned on. t₁₂= R_o−√ {(x₁₂-X_o)²+ (Y₁₂-Y_o)²} …………… (31) Do the same for other intersections P₁₃, P_{twenty one}, P_{twenty three}，
P₃₁, P₃₂Thickness t at ₁₃, T_{twenty one}, T_{twenty three}, T₃₁, T₃₂
Can be asked.

The method of the present invention is applied to an outer diameter of 177.8-406.4 mmφ
When applied to the thickness measurement of a seamless steel pipe of 5.5 to 55.0 mmt, the error of the eccentricity ratio is about 0.1% for an eccentricity eccentricity of ± 10%, which is several tenth of that of the conventional method. It was confirmed that the measurement can be performed with high accuracy. Moreover, the error of the uneven thickness rate due to the runout and the variation of the outer diameter was less than 0.01%.

[0036]

As described above, according to the present invention,
Measurement errors due to eccentricity and runout of the tubular material and fluctuations in the outer diameter can be eliminated, which greatly contributes to the improvement of product quality.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of the present invention.

FIG. 2 is a front view showing the configuration of a core runout / outer diameter measuring device used in the present invention.

FIG. 3 is a schematic diagram illustrating the first step of the procedure for calculating the wall thickness according to the present invention.

FIG. 4 is a schematic diagram illustrating a second step of the procedure for calculating the wall thickness according to the present invention.

FIG. 5 is a schematic diagram showing the principle of a conventional method for measuring the wall thickness of a tubular material.

FIG. 6 is a conceptual diagram of a measurement system of a conventional method.

FIG. 7 is a schematic diagram for explaining the influence of eccentricity and runout in the conventional method.

[Explanation of symbols]

 1 Source 2 Source container 3 Radiation beam 4 Detector 5 Conveyor roller 6 Drive motor 8 Pulse transmitter 10 Core runout / outer diameter measuring device 11, 12, 13, 14 Emitter 15, 16, 17, 18 Light receiver 20 Meat Thickness measuring device 30 Computing device P Tubular material

Claims (1)

[Claims] 1. At least three radiation beams intersect each other, and the beams are projected so that a regular odd-numbered polygon is formed with these intersections as vertices, and all the vertices of the polygons are made of a tubular material. The tubular member is positioned so as to be included in the portion, the intensity of the radiation beam after passing through the thick portion of the tubular member is measured, and the tubular portion at the position of the apex of the polygon is determined from the measured value. In a radiation transmission type wall thickness measuring method for a tubular material, which is obtained by calculating a wall thickness dimension of the material as a tube wall thickness, a step of actually measuring a core runout and an outer diameter of the tubular material and obtaining a value of an outer radius center position and an outer radius. And a step of obtaining the inner radius value and the inner radius center position by using the obtained outer radius center position and the outer radius value, and the obtained outer radius center position and the outer radius value and the inner radius center position and the inner radius value. Use to calculate the wall thickness of each pipe wall A radiation transmission type wall thickness measuring method for a tubular material, characterized in that: