JPH0316604B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a radiographic wall thickness measuring device for tubular materials, and in particular, the cross-sectional a radiation source for irradiating a wide radiation beam with a width exceeding the outer diameter of the tubular material, suitable for use in measuring the average wall thickness; and a radiation source located on the opposite side of the radiation source across the tubular material. , a radiation detector for detecting the wide radiation beam incident through the entire cross section of the tubular material, and the cross-sectional average wall thickness of the tubular material is determined based on the amount of attenuation of the wide radiation beam by the tubular material. The present invention relates to an improvement of a radiographic thickness measuring device for tubular materials, which measures the thickness of tubular materials.

[Conventional technology]

Generally, manufacturing (rolling) of tubular materials in the steel industry
When controlling this wall thickness in the process, highly accurate wall thickness measurement is required. In addition, in order to increase productivity, it is important to be able to measure wall thickness online without stopping the manufacturing process, and non-contact measurement is also possible in hot processes where tubular materials are exposed to high temperatures. Not only is it possible, but it is desirable to be able to measure from a position as far away from the tubular material as possible. As shown in FIG. 9, a radiographic wall thickness measuring device that satisfies these conditions has already been developed, as shown in FIG.
a radiation source 12 for irradiating 4; and a tubular material 10.
placed on the opposite side of the radiation source 12 across the
and a radiation detector 16 for detecting the wide radiation beam 14 that passes through the entire cross section of the tubular material 10 and is incident, and detects the width of the tubular material 10 based on the amount of attenuation of the wide radiation beam 14 by the tubular material 10. The one that calculated the cross-sectional average wall thickness was published in JP-A-58
−158510. That is, in this radiation transmission type thickness measuring device, the wide radiation beam 1
If the tubular material 10 is not present in the radiation detector 4, the distribution of radiation reaching the radiation detector 16 will be
On the other hand, if the tubular material 10 is present, the result will be as shown in Figure 10A (the radiation dose detected at this time is taken as the total radiation dose No.). The detected radiation dose is defined as the signal radiation dose Ns), and the cross-sectional average wall thickness of the tubular material 10 is determined from the ratio (Ns/No). Such a radiographic wall thickness measuring device is suitable for measuring the wall thickness of small-diameter seamless steel pipes, where it is not necessary to measure the wall thickness at each point during rolling control, and it is sufficient to know the average wall thickness of the cross section. This is particularly effective.

[Problems to be solved by the invention]

However, in general, for small-diameter seamless steel pipes, the standard outside diameter changes greatly within the same rolling line. Therefore, when the effective measurement width L of the wide radiation beam 14 is constant, the outside diameter of the tubular material 10 When D changes, the ratio of the amount of attenuation by the tubular material 10 (No - Ns) to the total radiation dose No does not become an appropriate size, and there is a problem that sufficient measurement accuracy may not be obtained. was. That is, when the width L of the wide radiation beam 14 is made large to match a small diameter seamless steel pipe with a relatively large diameter of about 180 mm in outer diameter, for example, the width L of the wide radiation beam 14 is increased to match a small diameter seamless steel pipe with a relatively small diameter of about 30 mm in diameter. When measuring the amount of attenuation (No−Ns) relative to the total radiation dose No.
The ratio may become too small and the necessary measurement accuracy may not be obtained. In order to solve such problems, the applicant has already proposed in Japanese Patent Application No. 58-241560 that the effective measurement width of the wide radiation beam 14 is changed to It is proposed that it can be changed according to the outer diameter D. However, for example, the radiation source 12 is configured by a plurality of individual radiation sources arranged in parallel in the width direction of the wide radiation beam 14, and the irradiation of the wide radiation beam 14 is performed by changing the interval between the individual radiation sources. If the width L is made changeable, the intensity distribution in the width direction of the wide radiation beam 14 is not necessarily uniform, which not only makes it impossible to sufficiently improve measurement accuracy, but also causes measurement errors due to center runout of the tubular material 10. This has the problem that it may occur.

[Purpose of the invention]

The present invention was made to solve the above-mentioned conventional problems, and even if the standard of the tubular material changes or core runout occurs in the tubular material, it is possible to perform appropriate measurements according to the outer diameter of the tubular material. It is an object of the present invention to provide a radiation transmission type wall thickness measuring device for a tubular material, which can increase adaptability to an outer diameter range and improve measurement accuracy.

[Means to solve the problem]

The present invention provides a radiographic wall thickness measuring device for a tubular material, which includes a plurality of individual radiation sources each generating a fan-shaped radiation beam, which are arranged in parallel in a direction parallel to the radial direction of the tubular material; radiation source position changing means for changing the irradiation width of a wide radiation beam formed by combining the plurality of fan-shaped radiation beams by changing the interval of the individual radiation sources according to the radiation source; a radiation intensity changing means for making the widthwise intensity distribution of the wide radiation beam uniform by changing the radiation intensity of at least a portion of the radiation source; , a radiation detector for detecting the wide radiation beam transmitted through the entire cross section of the tubular material, and detecting the average cross-sectional thickness of the tubular material based on the amount of attenuation of the wide radiation beam by the tubular material. The above objective has been achieved in the desired manner.

[Effect]

In the present invention, the radiation source is composed of a plurality of individual radiation sources that are arranged in parallel in a direction parallel to the radial direction of the tubular material and each generates a fan-shaped radiation beam. By changing the interval between the radiation sources, the irradiation width of the wide radiation beam formed by combining the plurality of fan-shaped radiation beams is changed. It can be changed according to the diameter, the ratio of the attenuation amount (No-Ns) to the total radiation dose No can always be set to an appropriate value, and both the outer diameter range compatibility and measurement accuracy can be improved. Furthermore, by changing the radiation intensity of at least a portion of the individual radiation sources, the width direction intensity distribution of the wide radiation beam is made uniform, which not only improves measurement accuracy but also improves the width of the tubular material. There is no measurement error caused by center runout.

【Example】

Embodiments of the present invention will be described in detail below with reference to the drawings. As shown in FIG. 1, in this embodiment, a plurality of (three in the figure) individual fan-shaped radiation beams are used to irradiate a wide radiation beam 14 with a width L exceeding the outer diameter D of the tubular material 10. Radiation sources 22A, 22
A radiation source 20 in which B and 22C are arranged in parallel in a direction parallel to the radial direction of the tubular material 10 in a radiation source container, and the individual radiation source 2 in accordance with the outer diameter D of the tubular material 10.
2A, 22B, and 22C to change the irradiation width L of the wide radiation beam 14 formed by combining the plurality of fan-shaped radiation beams; a radiation intensity changing device 26 for making the width direction intensity distribution of the wide radiation beam 14 uniform by shielding the individual radiation sources 22B; and a tubular material 10.
disposed on the opposite side of the radiation source 20 across the
a radiation detector 30 for detecting the wide radiation beam 14 that passes through the entire cross section of the tubular material 10 and enters through the slot 28; and the radiation source 2.
0 and a movable stand 40 for supporting the radiation detector 30 and the like. The radiation source position changing device 24 includes a fixedly arranged central individual radiation source 2, as shown in detail in FIG.
Individual radiation sources 22 arranged above and below 2B
A, 22C includes a threaded rod 24A with oppositely threaded upper and lower threads. Therefore, by rotating the screw rod 24A, the upper and lower individual radiation sources 22A and 22C can be moved toward or away from the fixed individual radiation source 22B at the same time. This changes both the irradiation width L of the wide radiation beam 14 and its widthwise irradiation density. As shown in detail in FIGS. 3 and 4, the radiation intensity changing device 26 has a plurality of thicknesses (three types in the figure) for changing the radiation intensity of the central fixed individual radiation source 22B. three thicknesses of the shield 26A and four types of no shielding by rotating the shield 26A in a horizontal plane containing the central individual radiation source 22B. Radiation intensity can be selected. In addition, instead of preparing multiple thicknesses of the shielding material 26A, it is possible to prepare multiple types of materials for the shielding material,
Alternatively, it is also possible to use both together. As shown in detail in FIG. 5, the radiation detector 30 includes two scintillators 32A and 32B arranged in series in the width direction of the wide radiation beam 14, and arranged at the outer ends of the scintillators 32A and 32B, respectively. Two photomultiplier tubes 34A, 34B
It is composed of. Note that if the maximum outer diameter of the tubular material 10 is relatively small and therefore there is no possibility that the output of the scintillator will be saturated, it is sufficient to provide one set of a scintillator and a photomultiplier tube. Furthermore, instead of the combination of a scintillator and a photomultiplier tube, it is also possible to use other radiation detectors such as an ionization chamber or a GM tube. The effects of the embodiment will be explained below. In the measurement, first, the threaded rod 24A is rotated in accordance with the outer diameter D of the tubular material 10, and the irradiation width L of the wide radiation beam 14 is larger than the outer diameter D of the tubular material 10, and The irradiation width L is adjusted so that the ratio of the attenuation amount (No-Ns) to the total radiation dose No becomes an appropriate value. Next, the individual radiation sources 22A, 22B, 22
Depending on the distance between C and C, the radiation intensity of the central individual radiation source 22B is adjusted by rotating the shield 26A in order to make the radiation intensity distribution in the width direction of the wide radiation beam 14 uniform. Figures 6 to 8
The figure shows the ratio of the radiation intensity of the individual radiation source 22B in the center to the individual radiation sources 22A and 22C at both ends to make the radiation intensity distribution uniform in the width direction and to prevent the center runout of the tubular material 10. This shows whether the measurement error is minimized. In this experiment, the individual radiation sources 22A, 22
The distance between B and 22C is 40 mm, and the tubular material 10 has a diameter of 50 mm and a wall thickness of 5 mm. Figure 6 shows the case where the intensities of the individual radiation sources 22A, 22B, and 22C are all the same (xc _i ). , FIG. 7 shows the intensity of the central radiation source 22B compared to the radiation sources 22A on both sides,
When the intensity (xc _i ) of 22C is set to 1/10, FIG. 8 shows the case where the central individual radiation source 22B is omitted. In the case of this experiment, when the intensity of the central radiation source 22B was set to 1/10 of the intensity of the radiation sources 22A and 22C on both sides, the center runout error was minimized and good results were obtained. Recognize. Next, a predetermined standard sample is inserted into the position of the object to be measured, a wall thickness measurement scale is formed, and then online measurement is performed. Although the present invention is suitable for measuring the wall thickness of small-diameter seamless steel pipes at the entrance and exit sides of a stretch reducer, the scope of application of the present invention is not limited to this, and can be applied to the cross-section of general tubular materials. It is clear that it can be used for wall thickness measurements as well.

【Effect of the invention】

As explained above, according to the present invention, the effective measurement width and the width direction intensity distribution of the wide radiation beam can be changed in accordance with the outer diameter of the tubular material. Therefore, by always setting the ratio of the attenuation amount to the total radiation dose to an appropriate value and always making the width direction intensity distribution of the wide radiation beam uniform, both the outer diameter range compatibility and the measurement accuracy can be improved. Can be done.
In addition, it has excellent effects such as being able to reduce the minimum error due to center runout of the tubular material.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the configuration of an embodiment of the radiographic wall thickness measuring device for tubular materials according to the present invention, and FIG.
The figure is a front view showing the configuration of the radiation source position changing device used in the embodiment, FIG. 3 is a plan view showing the configuration of the radiation intensity changing device, and FIG.
Similarly, FIG. 5 is a front view showing the configuration of the radiation detector, and FIGS. 6 to 8 show the intensity of the central individual radiation source in the above embodiment for explaining the principle of the present invention. Figure 9 is a diagram that compares and shows how the center runout error changes when changing.
FIG. 10 is a cross-sectional view showing the basic structure of a conventional radiographic thickness measuring device, and is also a cross-sectional view for explaining the measurement principle. 10... Tubular material, D... Outer diameter, 14... Wide radiation beam, L... Irradiation width, 20... Radiation source,
22A, 22B, 22C...Individual radiation source, 24
...Radiation source position change device, 24A...Screw rod,
26... Radiation intensity changing device, 26A... Shielding,
30... Radiation detector.

Claims (1)

[Claims] 1. Arranged in a direction parallel to the radial direction of the tubular material,
a plurality of individual radiation sources each generating a fan-shaped radiation beam; and a wide radiation beam obtained by combining the plurality of fan-shaped radiation beams by changing the interval between the individual radiation sources in accordance with the outer diameter of the tubular material. radiation source position changing means for changing the irradiation width of the radiation source; and radiation source position changing means for making the widthwise intensity distribution of the wide radiation beam uniform by changing the radiation intensity of at least a part of the individual radiation sources. and a radiation detector disposed on the opposite side of the radiation source across the tubular material to detect the wide radiation beam incident through the entire cross section of the tubular material, A radiographic thickness measuring device for a tubular material, characterized in that the average cross-sectional wall thickness of the tubular material is determined based on the amount of attenuation of the wide radiation beam.