JPS60100706A - Method and device for measuring shape of conductive material - Google Patents

Abstract

PURPOSE:To measure the shape and thickness of a body to be detected with high precision regardless of the temperature of the object of measurement by generating an alternating magnetic field near the body to be detected by an exciting coil, and utilizing the intensity of the magnetic field near the exciting coil or the height or phase of the density of leak magnetic flux from the body to be detected. CONSTITUTION:Voltages detected by detection coils 2 and 3 are amplified by amplifiers 5 and 6, whose outputs V1 and V2 are inputted to a gain phase gauge 7, which outputs the gain G1 and phase difference psi1 of the V1 and V2 to a computing element 9. Signals G2 and psi2 relating to the thickness are linearized and processed to output a voltage V01 proportional to the thickness. Further, the G2 and psi2 are processed similarly to output a voltage V02 proportional to the gap between the detection coil 2 and a pipe. Plural detection coils 2 and 3 are arranged circumferentially to measure the position and thickness of the pipe at an installation point, thereby knowing the outward appearance and the shape of the thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method and apparatus for measuring the shape of a conductive material, such as the outer diameter and wall thickness of a hot steel pipe.

(Prior art) As a means for measuring the outer diameter of steel pipes, for example, the technical document "Working and Optimal Utilization of Sensors" (March 1982)
There are measurement means using image sensors and lasers, such as the one disclosed in Gijutsu Hyoronsha (published on August 10th). However, these technologies are for when the object to be measured is at room temperature; if the object to be measured is at a high temperature, a device to remove water or water vapor, or a device to cool the sensor is required. The disadvantage is that the equipment is complicated and expensive.

On the other hand, as means for measuring the wall thickness of steel pipes, for example, methods using ultrasonic waves and methods using radiation are in practical use. However, thickness measuring means using ultrasonic waves uses water,
It requires the presence of an acoustic coupling medium such as oil and cannot be applied when the object to be measured is at a high temperature. Also, thickness measuring means that utilize radiation have the disadvantage of being very expensive.

(Objective of the Invention) The purpose of the present invention is to provide a method and apparatus that have a simple structure and can measure the shape and thickness of an object with high precision regardless of the temperature of the object to be measured.

(Structure of the Invention) The method for measuring the shape of a conductive material according to the present invention generates an alternating magnetic field near a subject using an excitation coil, and
A first magnetic field detection coil detects the strength or phase of the magnetic field near the excitation coil, and a second magnetic field detection coil provided apart from the first magnetic field detection coil detects the intensity or phase of the magnetic field from the subject. detecting the height or phase of the leakage magnetic flux density of the excitation coil, and detecting the difference between the strength or phase of the magnetic field generated by the excitation coil and the strength or phase of the magnetic field detected by the first magnetic field detection coil. In addition to measuring the distance between the excitation coil and the subject, the strength or phase of the magnetic field detected by the first magnetic field detection coil and the leakage magnetic flux density from the subject detected by the second magnetic field detection coil are measured. The device is characterized in that the thickness of the object is measured from the difference in height or phase, or a signal equivalent thereto, and the device for measuring the shape has an alternating magnetic field in the vicinity of the object. an excitation coil that generates an alternating current; an AC oscillator that supplies an alternating current to the excitation coil;
A first magnetic field detection coil for detecting a magnetic field is provided, and a second magnetic field detection coil is provided separated from the second magnetic field detection coil for detecting leakage magnetic flux from the subject, and further includes a second magnetic field detection coil for detecting leakage magnetic flux from the subject. Which of the first magnetic field detection coils receives a signal from one side and a signal from the second magnetic field detection coil and outputs the gain and phase difference between these signals, and the AC oscillator and the first magnetic field detection coil. and a gain phase meter that receives signals from the excitation coil and outputs the gain and phase difference between these signals, and a gain phase meter that receives signals from each of the gain phase meters and calculates the distance between the excitation coil and the object and the distance between the excitation coil and the object. The present invention is characterized in that it includes a calculation unit that calculates the thickness of the specimen.

The present invention will be explained in detail below.

(Embodiments of the Invention) First, the measurement principle of the present invention will be described. As shown in FIG. 1, the strength of the magnetic field is Ho (Hz in the Z direction), and the magnetic permeability is μ (
If the atmosphere is μ0 and the steel is μ), and the conductivity of the steel is K, then
The magnetic field within the steel material is given by the following equation:

When a magnetic field advances into a steel material, its magnitude attenuates exponentially, and a phase delay occurs that corresponds to its depth.

Cylindrical coil l that generates an alternating magnetic field as shown in Figure 2
If, for example, a non-magnetic vibrator 13 is in NfI, the magnetic field distribution will be as shown in the figure (however, only a - example is shown).

The magnetic field strength and phase at point A in Figure 2 are approximately determined by the distance β between coil 1 and the vibrator, and the magnetic field strength and phase at points B and 0 are determined by the distance β and the path of the magnetic field within the vibrator, that is, the wall thickness of the vibrator. It is decided. Therefore, by calculating the difference, ratio, and phase difference in magnetic field strength between point A and point B or point 0, a signal related only to the wall thickness can be extracted. FIG. 3 shows the difference (phase difference) ψ2 between the phase in the excitation coil shown in FIG. 2 and the phase of the magnetic field at point A, and the distance l between the excitation coil 1 and the pipe 13 that is the subject shows the relationship between

In addition, FIG. 4 shows the difference (phase difference ψ1) between the phase of the magnetic field at point A shown in FIG. 2 and the phase of the magnetic field at point B or point 0.
) and the wall thickness of the pipe being tested.

A specific measuring device is shown in FIG.

The excitation coil 1 has a cylindrical shape and is connected to an AC oscillator 4, so that the excitation coil 1 generates an AC magnetic field. The detection coil 2 is installed immediately beside the excitation coil 1, and the detection coil 3 is installed at a distance from the detection coil 2. The detection coils 2 and 3 are for detecting leakage magnetic flux from the excitation coil 1 and the pipe, and are very small coils.

Since the voltage detected by the detection coil 2.3 is small, it is amplified by the amplifier 5.6. Their voltage output Vl, V
2 is input to a gain phase meter 7, which outputs a gain G1 and a phase difference ψ1 of vl and 2, which are input to an arithmetic unit 9. The output V1 of the amplifier 5 and the AC oscillator 4 are input to the gain phase meter 8,
The outputs thereof, the gain 1MG2 and the phase difference ψ2, are also input to the calculator 9.

The computing unit 9 outputs a voltage proportional to each purpose. The arithmetic unit 9 receives a signal G + related to wall thickness.

By linearizing and calculating ψ1, a voltage VOI proportional to the wall thickness is output. Further, G2゜ψ2 performs similar processing and outputs a voltage VO2 proportional to the distance l between the detection coil 2 and the pipe.

By arranging the detection coils 2.3 at several locations in the circumferential direction, the position and wall thickness of the pipe at the installation point can be measured, and by arithmetic processing of this, the external shape and wall thickness can be determined.

For hot pipe measurements, heat resistance of the coil is required.
As shown in FIG. 6, a coil is wound around a ceramic 10 and cooled with cooling water 11. Since the scale of the pipe falls inside the ceramic 10, the scale is blown away by the air purge 12.

As a measuring method, the method shown in FIG. 8 may be used. Figure 8 is the 5th
This is a modification of the measurement method shown in the figure. The output (G2.ψ2) of the gain phase meter 8 shown in FIG. 8 is the same as that shown in FIG. The gain phase meter 7 outputs the relationship between the excitation coil 1 and the detection coil 3 (G3.ψ3). The arithmetic unit 14 calculates the gain phase difference (ΔG
, Δψ). The calculation formula is as follows.

ΔG = 02 G 3゜Δψ=92-93 ΔG and Δψ correspond to G+ and ψ1 in FIG. is outputting. Next, the results of implementing the present invention will be shown.

Implementation results: Excitation frequency IKHz Excitation coil Inner diameter 70φ Winding width 50 600T Detection coil 27φ 150T Detection coil 38φ 200T Detection coil 1.2 spacing L-151 Measurement object SUS pipe Wall thickness 2 to 8 dragon temperature 600
Figure 7 shows the results measured under specifications of around °C or higher. It can be seen that the thickness of the object can be measured with extremely high accuracy.

(Effects of the Invention) As described above, the present invention measures the position and wall thickness of a pipe by detecting leakage magnetic flux, and has the following features.

■) Capable of measuring from cold to hot conditions, particularly effective and accurate for hot conditions (non-magnetic materials).

2) In the case of pipes, the external shape and wall thickness of the pipe can be measured at the same time.

3) Can also be applied to measurements of thick plates, shaped steel, etc.

4) It is cheaper and easier to maintain than other methods (ultrasound, radiation, etc.).

5) The wall thickness measurement range can be selected by changing the measurement frequency.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the magnetic field within the steel material, FIG. 2 is a diagram showing the magnetic field distribution of the pipe and the measurement principle of the present invention, and FIG. 3 is a diagram illustrating the magnetic field within the steel material. Fig. 4 is a graph showing the basis of the measurement method of the present invention, Fig. 5 is a block diagram showing an embodiment of the invention, and Fig. 6 is a sectional view of a hot coil which is a modification of the invention. FIG. 7 is a graph showing hot measurement results, and FIG. 8 is a block diagram showing another embodiment of the present invention. 1: Excitation coil, 2: Detection coil, 3: Detection coil,
4: AC oscillator, 5: amplifier, 6: amplifier, 7: gain phase needle, 8: gain phase meter, 9: arithmetic unit, 10: ceramics, 11: cooling water, 12: air purge, 13: pipe. Applicant Nippon Steel Corporation Patent Attorney Minoru Aoyagi Figure 1 Figure 2 Section 1 Figure 3 Figure 4 Thickness □

Claims (2)

[Claims] (1) An excitation coil generates an alternating magnetic field near the subject, and a first magnetic field detection coil generates an alternating magnetic field near the subject.
The intensity or phase of the magnetic field in the vicinity of the excitation coil is detected, and a second magnetic field detection coil provided apart from the first magnetic field detection coil is used to detect the height or the leakage magnetic flux density from the subject. detects the phase, and determines the distance between the excitation coil and the subject from the difference between the strength or phase of the magnetic field generated by the excitation coil and the strength or phase of the magnetic field detected by the first magnetic field detection coil. and the difference between the strength or phase of the magnetic field detected by the first magnetic field detection coil and the height or phase of the leakage magnetic flux density from the subject detected by the second magnetic field detection coil. A method for measuring the shape of a conductive material, characterized in that the thickness of a subject is measured from a signal equivalent thereto. (2) an excitation coil that generates an alternating magnetic field near the subject; and an alternating current oscillator that supplies an alternating current to the excitation coil;
A first magnetic field detection coil for detecting a magnetic field is provided in the vicinity of the excitation coil, and a second magnetic field detection coil for detecting leakage magnetic flux from the subject is provided at a distance from the second magnetic field detection coil. and a gain phase meter that receives signals from the AC oscillator and the first magnetic field detection coil and outputs the gain and phase difference between these signals, and a signal from either the AC oscillator or the first magnetic field detection coil. and a gain phase meter that receives the signals from the second magnetic field detection coil and outputs the gain and phase difference between these signals; An apparatus for measuring the shape of a conductive material, comprising a computing unit that calculates the distance between specimens and the thickness of the specimen.