JPS60165543A - Magnetic powder flaw detecting method of steel tube - Google Patents

Abstract

PURPOSE:To improve the accuracy of detection by insertig a copper pipe which has a slit part and incorporates an iron core into a steel pipe placed between two series coils in the same direction, feeding a rectified wave current to electrode plates at both ends, and supplying an alternating current to the coils. CONSTITUTION:The two coils 4 and 4' connected in series in the same winding direction are added to both ends of the steel tube 1 to be inspected, and the copper pipe 2 which has the slit part 2a bored axially and incorporates the iron core 3 is inserted. Then, the alternating current is flowed to the coils 4, 4' to supply alternating magnetic flux to the iron core 3, and the material 1 to be insepcted is magnetized with an induced current to detect a circumferential defect. Further, the electrode plates 5, 5' are brought into press contact with both end parts of the copper pipe 2 and a single-phase half-wave rectified current is fed from the same three-phase AC power source with the coils to detect an axial defect of the material 1 to be inspected. Consequently, defects in the inside of the material 1 to be inspected in all directions are detected at the same time speedily and accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic particle flaw detection method suitable for simultaneously detecting defects existing in a steel pipe, particularly defects existing in all directions on the inner surface.

The magnetic particle flaw detection method is a non-destructive inspection method in which the material to be inspected is magnetized and a magnetic particle liquid is sprayed.The magnetic particles are attracted to the leakage magnetic flux that magnetizes the defective part, and defects are detected from the magnetic particle pattern formed there. , the only defects that can be detected by this method are those in the direction perpendicular to the magnetic flux direction.

Therefore, in order to simultaneously detect defects in all directions in a steel pipe, it is necessary to magnetize the steel pipe so that magnetic flux flows in both the axial and circumferential directions at the same time.
The current penetration method (axial defect detection) involves penetrating a conductor into a steel pipe and magnetizing it, and the coil method (which magnetizes the steel pipe by placing it inside a coil).
Detection of defects in the circumferential direction) is performed at the same time.

However, when using the above-mentioned current penetration method and coil method simultaneously to detect defects in steel pipes, the current penetration method magnetizes the steel pipe from the inside, so it is difficult to accurately detect axial defects on the inner surface of the steel pipe. However, when magnetizing from the outside of the steel pipe as in the coil method, as the thickness of the steel pipe increases, sufficient magnetization does not reach the inner surface, which significantly reduces the accuracy of detecting defects in the circumferential direction on the inner surface of the steel pipe. There are drawbacks.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic particle flaw detection method that eliminates the above-mentioned drawbacks and can quickly and accurately detect defects in all directions on the inner surface of a thick tube.

For this purpose, the flaw detection method according to the present invention involves interposing a steel pipe, which is the material to be tested, between two coils connected in series and in the same direction, and having a part of Surin l in the axial direction, After a copper pipe with a built-in iron core is inserted, electrode plates are crimped to both ends of the copper pipe, and alternating current is applied to the coil and rectified wave current is applied to the electrode plate at the same time. .

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be explained by way of examples with reference to figures and planes. FIG. 1 is an explanatory diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is an enlarged sectional view taken along line AA' in FIG.

Two coils 4, 4' connected in series and in the same direction are attached near both ends of the steel pipe 1, which is the material to be tested, and the steel pipe 2 is inserted therethrough. This copper vibe 2 has a slit 2a formed in the axial direction, and contains therein an iron core 3 made of laminated silicon steel plates having a length slightly shorter than that of the copper pipe.

When an alternating current is applied to the coils 4.4' under such a configuration, an alternating magnetic flux flows through the two coils 4.4' and the iron core 3 through which the specimen 1 interposed between them is inserted, and this alternating magnetic flux As a result, an induced current is generated in the specimen 1 due to electromagnetic induction, and the specimen 1 is magnetized by the magnetic field caused by this current. In this case, the alternating magnetic flux of the iron core 3 first causes an induced current in the copper pipe 2 containing the iron core 5, which significantly reduces the electromagnetic induction effect on the specimen 1, causing magnetization of the specimen 1. becomes difficult. Therefore, in order to enhance the electromagnetic induction effect on the specimen 1, it is necessary to provide a slit portion C in the axial direction of the copper pipe 2 to interrupt the induced current flowing in the circumferential direction of the copper pipe 2. Moreover, this slit portion 2a also has the effect of preventing a rise in temperature of the copper pipe due to Joule heat caused by magnetization due to induced current.

Defects that can be detected by magnetization caused by this induced current are defects in the circumferential direction of the test material 1.

Next, electrode plates 5.5' are crimped to both ends of the copper vibrator 2,
If a rectified wave current is passed, this is the same as the normal current passing method, and defects in the axial direction of the test material 1 can be detected. For the rectified wave current in this case, it is effective and practical to use single-phase half-wave rectification, which is rectified from the same three-phase AC power source as the AC power supply to the coil.

Therefore, if a magnetic particle flaw detection test is performed under such a configuration, the material to be tested 1 will be magnetized in such a way that the magnetic flux directions are perpendicular to each other on the inside, so defects in all directions existing on the inner surface of the material to be tested 1 will be detected. can be detected simultaneously.

In this way, the present invention interposes the material to be inspected between two coils, inserts a single penetrating rod having a slit in the axial direction and a built-in iron core therein, and then An extremely simple method of crimping electrode plates to both ends of the rod and simultaneously applying single-phase AC to the coil and single-phase half-wave rectification to the electrode plate from the same commercial three-phase AC was used to conduct the test. The feature is that defects in all directions on the inner surface of materials can be detected quickly and accurately.

When conducting an actual magnetic particle flaw detection test, it is necessary to apply magnetic particle liquid at the same time as magnetization, and in this case, it is convenient to use a steel pipe in combination as a magnetic particle liquid dispersion tube for the inner surface of the test material. When using the copper pipe 2 as a magnetic powder liquid dispersion pipe,
A magnetic powder liquid introduction valve 6 is provided near the end of the copper vibrator 2, and a plurality of magnetic powder liquid dispersion holes 2b are bored along the axial direction, and a slit portion 2a is provided in order to prevent leakage of the magnetic particle liquid. It is necessary to embed insulating resin.

In this way, if the present invention is carried out with the copper pipe used as the magnetic powder liquid dispersion pipe on the inner surface and the magnetic powder liquid dispersion pipe 7 piped on the upper part of the outside of the material to be inspected, the electromagnetic conduction according to the present invention can be achieved. By simultaneously spraying magnetic powder liquid on the inner and outer surfaces of the material to be inspected, it is also possible to simultaneously detect defects in all directions on the inner and outer surfaces of the material to be inspected.

INDUSTRIAL APPLICATION This invention is extremely effective when carrying out the magnetic particle flaw detection test of the steel pipe in which the pipe end part is thickened, such as an upset steel pipe, or a thick-walled rectangular pipe.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the configuration of an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view taken along line A-A' in FIG. 1. Test material 02.
・Copper pipe 2a...Slit part 3...Iron core 4.
4'...Coil 5...Electrode plate patent applicant Rei/)YJ

Claims (1)

[Claims] A steel pipe, which is the material to be tested, is interposed between two coils connected in series and in the same direction, and a copper pipe with a slit in the axial direction and a built-in iron core is inserted into the pipe. A magnetic particle flaw detection method for copper tubes, which is characterized by crimping electrode plates on both ends of the tube, and simultaneously applying alternating current to the coil and rectified wave current to the electrode plates.