JPS5839285B2 - Calibration method of ultrasonic dimension measuring device - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for calibrating an ultrasonic dimension measuring device.

In recent years, automatic measurement of the inner and outer diameters and wall thicknesses of various pipes over their entire length has become convenient by using ultrasonic dimension measuring devices.

The ultrasonic dimension measuring device is configured as follows, for example.

That is, as shown in FIGS. 1 and 2, the front and rear walls 21a of the water tank 20.

21b is provided with an inlet 22a and an outlet 22b for sending in and out the pipe to be measured (hereinafter simply referred to as "pipe") 1, and these inlets and outlets 22a, 22b are designed to prevent water from leaking without interfering with the movement of the pipe 1. It is sealed by appropriate sealing mechanisms 23a and 23b that can prevent this.

The tube 1 is fed in the axial direction while being rotated around the axis by spiral feeding rollers 24 provided before and after the tank 20.

The tank 20 has a temperature sensor 25 for measuring water temperature and a water circulation nozzle 26.
In addition to equipment to maintain a uniform and constant water temperature in the tank, there are also equipment on both sides of the passage of the tube 1 (measuring probes 27a,
27b, and a slug 28a and a water temperature guarantee probe 28b are provided on both sides above the slug 27b.

Then, the ultrasonic waves emitted by the measurement probes 27a and 27b are perpendicular to the surface of the tube 1.
．． S2 and bottom echo 13tt 5 B125 B13・
・And B21? B2□, B23... are generated.

Surface echo S1. S2 is generated when the incident wave is reflected on the surface of the tube 1, and the bottom echo Bll, B12 j
B13...and B21, B22 j B23・
. . . is generated when an inward incident wave of the tube 1 is reflected by the inner circumferential surface of the tube 1.

The distance W1 between the probe 27a and the tube 1 is determined by the time interval between the oscillation pulse O1 on the measurement probe 27a side and the surface echo S1, and the distance W1 between the probe 27a and the tube 1 is
The wall thickness T1 on this side of the tube 1 is determined by the time interval t between the bottom echo B1□ and the bottom echo B1□.

Similarly, from the measurement probe 27b side, probe 2
Distance W2 between 7b and tube 1 and wall thickness T2 on this side of tube 1
is found.

If the constant corresponding to the probe spacing is C, then the outer diameter of the tube 1 is O
D, wall thickness WT, and inner diameter ID are OD2c-(W1
+W2) WT=T.

ID=OD-(T1+'r2) It is required.

Since this device measures dimensions based on the above principle, it is extremely sensitive to changes in water temperature.

Therefore, in order to keep the water temperature uniform throughout the tank, the water circulation nozzle 26 (thus circulates the water), and the water temperature guarantee probe 28bI is installed so that the constant C remains constant even if the water temperature changes. Therefore, an automatic correction is made.

By the way, in order to measure the dimensions of tubes that require extremely strict dimensional accuracy, such as Zircaloy cladding tubes for nuclear reactors, the dimensional accuracy of the limit gauge for calibrating the measuring device must also be high.

However, according to research conducted by the inventors, in order to improve measurement accuracy, it is not only necessary to simply increase the dimensional accuracy of the limit gauge, but also to sufficiently select the material of the gauge part and set the processing conditions. It is extremely important to take this into account, and we have therefore completed this invention after conducting various studies from this perspective.

That is, the present invention provides the following features when measuring dimensions using ultrasonic waves:
At least the gauge part should be made of a material with the same composition as the Sugagasa object to be measured, and among the processing conditions for the object to be measured, at least the working degree during rolling, the Q value, and the heat treatment conditions should be the same.
This is a method for calibrating an ultrasonic dimension measuring device, characterized in that calibration is performed using a limit gauge processed by a strainer.

Next, this will be explained in detail.

3 and 4 show a limit gauge used in the practice of the present invention, and this limit gauge 10 has two joints 11 interposed at the connecting portion.
short (20 to 40 mm) circular tubular standard test pieces 12a,
12b and two elongated circular tubular length supplementary members 13-a, 13b sandwiching these test pieces 12a, 12b into one elongated tubular shape (these are arranged continuously, and these test pieces 12a, 12b,
Length supplementary member 13at13b and joint 11...
- and length supplementary member 13a.

An oak N6 screwed onto both ends of a bolt 15 passing through washers 14a and 14b fitted on each end of the bolt 13b.
a, 16b (in particular, each of the above members 11.1)
2a, 12b, 13a, 13b.

14a and 14b are fixed in a disassembly manner.

This example shows a limit gauge for inner diameter, with the test piece 12a serving as the lower limit size gauge part and the test piece 12b serving as the upper limit size gauge part.

These test pieces 12a and 12b are the pipe 1 to be measured.
It is made using a material with the same composition as the pipe 1, and its processing conditions match those of the pipe 1 to be measured in at least three respects: degree of processing during rolling, setting of Q value, and setting of heat treatment conditions. It is designed as follows.

Since it is preferable to avoid differences even under other processing conditions, attempts are made to match them as much as possible.

An example of a limit gauge for calibration when measuring the dimensions of a Zircaloy reactor cladding tube for a nuclear reactor (to explain this more specifically, first, using a material with the same composition as tube 1, and under rolling conditions) By rolling this with a strainer so that the working degree (4) and Q value of
This is machined so that its thickness is uniform over its entire length.

If there is no space for machining, this machining step may be omitted, or polishing may be performed as the case requires.

Next, place this tube for test piece into tube 1 so that the crystal grain size of the tube for test piece here is the same as that of tube 1.
Heat treated under the same conditions as .

At this stage, the heat-treated material for the test piece obtained in this way was examined for its texture by X-ray (positive polarization method) and its crystal grain size was measured.
2) Confirm that there is no difference in the pole figures, that is, that the texture is the same as that of tube 1, and that there is no difference in grain size, that is, that the metal structure is the same as that of tube 1.

Next, in order to uniformly pickle only the inner surface of the heat-treated material for the test piece over the entire length, a vinyl hose was connected to both ends of the heat-treated material, and nitric-hydrofluoric acid was flowed inside to pickle the inner surface with a 0.0.
Chemically polish only a small amount of about 0.05 mm.

Next (close both ends of this heat-treated test piece with rubber stoppers, immerse it in nitric-fluoric acid solution in a beaker, and rub the outer surface with a cloth to remove a very small amount of about <0.005 degrees). Only chemical polishing.

When the chemical polishing is completed in this way, the obtained test piece is precisely measured using a dimension measuring machine such as a universal length measuring machine manufactured by Carl Zeiss Jena of West Germany, and then assembled into the limit gauge 10 as described above. .

On the other hand, FIG. 5 shows an example of a conventional limit gauge, and when making this limit gauge 2, a raw pipe with a wall thickness sufficiently E than the target wall thickness of the gauge parts 2a and 2b is used. First, it was rolled, and then the circumferential surfaces of both ends were machined to remove the wall thickness surrounded by the chain lines in FIG. 5, thereby forming the gauge portion 2a t 2b.

As mentioned above, the limit gauge 10 used in the practice of this invention
The gauge part of the test piece 12at12b is obtained by rolling so that it has the same working degree and Q value as the pipe 1, whereas the conventional limit gauge 2 has a thick wall (which is obtained by rolling). Therefore, its Q value is different from that of tube 1.

Therefore, the metal structure of the gauge parts 2a and 2b of the conventional limit gauge 2 is different from the metal structure of the tube 1.

In this case, the sound speed of the ultrasonic waves traveling inside the gauge parts 2a and 2b and the sound speed of the ultrasound waves traveling inside the tube 1 will not be equal, so that the dimension indication values will differ.

If the material is Zircaloy, the difference in texture is (
This appears as a difference in the (0002) plane X-ray intensity, and the difference between this (0002) plane X-ray intensity and each dimension indication value of the micrometer and ultrasonic dimension measuring device for the same object, that is, the dimension indication difference value. The relationship between
It can be seen that the dimension difference value differs by 14μ.

From this, it is easily understood that the gauge part of the limit gauge needs to be processed so that the working degree and Q value during rolling are the same as the working degree and Q value of the object to be measured.

Figure 7 also illustrates the relationship between heat treatment conditions and inner diameter indicated difference values for Zircaloy, where I is the as-rolled material that has not been heat treated (related data, and ■ is 4
Data related to the stress relief material f obtained by heat treatment at 500C, and (■) data related to the recrystallized material obtained by heat treatment at 580C.

As seen in this figure, when the heat treatment conditions change, the crystal grain size changes and the sound velocity inside the material changes, so the inner diameter indicated difference value is approximately 2μ between the as-rolled material and the stress-relieved material, and the difference between the as-rolled material and the recrystallized material. There is a difference of about 4μ between the two materials (580°C).

From this, it is easily understood that the gauge part of the limit gauge needs to be heat treated under the same conditions as the object to be measured.

When performing ultrasonic measurement, this invention uses a material having the same composition as the object to be measured for at least the part that becomes the gauge part as described above, and among the processing conditions, at least the processing degree during rolling and the Q value. The limit gauge is processed so that the heat treatment conditions are the same as those of the object to be measured (this is how the calibration is performed, so the calibration accuracy is significantly improved, and compared to the previous method (which has produced excellent measurement results). It is possible to obtain.

Recently, demand for Zircaloy fuel cladding for nuclear reactors has increased.

Furthermore, an extremely high level of finishing dimensional accuracy is required.

However, if the method of this invention is put into practice, this can be fully met.

The present invention can also be applied to cold-rolled materials such as titanium and stainless steel in addition to the above-mentioned cold-rolled Zircaloy materials.

[Brief explanation of drawings]

Fig. 1 is a front sectional view showing an ultrasonic dimension measuring device during pipe dimension measurement and the pulse waveform obtained from it, Fig. 2 is a side sectional view of the same device, and Fig. 3 is a limit gauge used in the actual implementation of this invention. FIG. 4 is a side view of the same limit gauge, FIG. 5 is a partially cut-away side sectional view of the conventional limit gauge,
Figure 6 is a chart showing the relationship between the (0002) plane X-ray intensity and the dimension difference value for Zircaloy. Figure 7 is a chart showing the relationship between the heat treatment conditions and the inner diameter difference value for Zircaloy. Yes. 10... limit gauge, 12at12b...
...Standard test piece that becomes the gauge part.

Claims (1)

[Claims] 1. When measuring dimensions by ultrasonic waves, at least the gauge part should be made of a material with the same composition as the object to be measured, and among the processing conditions for the object to be measured, at least the degree of working during rolling, the Q value, and the heat treatment conditions should be the same. A method for calibrating an ultrasonic dimension measuring device, characterized in that calibration is performed using a limit gauge processed using