JP7281979B2 - Electrodes for magnetic particle flaw detectors - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrode for a magnetic particle flaw detector, and more particularly to an electrode for magnetic particle flaw detection, in which an object to be inspected is energized or a magnetic field is applied to perform flaw detection using magnetic particles.

The magnetic particle testing is applied to the surface testing of objects to be inspected, such as steel materials such as billets and automobile parts, and is standardized in JIS-Z-2320. In the magnetic particle flaw detection test, a magnetic particle dispersion containing magnetic particles, that is, a magnetic particle liquid, is applied to the surface of the object to be inspected, and a magnetic field is applied to the object to be inspected, or an electric current is applied to the object to be inspected to magnetize the object to be inspected. If there is a flaw such as a crack on the surface of the magnetized object to be inspected, magnetic flux leaks from the flaw, and a magnetic particle indication pattern is formed by this leaked magnetic flux. Defects are inspected by observing the magnetic particle indication pattern. As a magnetic particle test, a fluorescent magnetic particle test using fluorescent magnetic particles containing a phosphor is also known in order to improve the detection accuracy of flaws.

In the axial energization method of magnetic particle inspection, a current is passed through an object to be inspected to generate a magnetic field perpendicular to the current direction, thereby magnetizing the object to be inspected. This inspection method can detect flaws in the direction perpendicular to the magnetic field, and is sensitive to flaws in the axial direction.

Composite magnetization by alternating current or half-wave rectification of the coil method and the axial current method detects flaws in all directions by applying a magnetic field in the axial direction from the outside at the same time that the current is applied to the object to be inspected. can do things

In Patent Document 1, when inspecting a long square pole-shaped steel material by the axial current method, a notch is provided so as to avoid the label on the steel piece with a label for product management attached to the end face in the longitudinal direction. An electrode is disclosed. Also, the electrodes are made of copper, which is a good conductor.

JP-A-2006-322748

Patent Literature 1 discloses an electrode that is inclined with respect to the end surface of an object to be inspected in order to improve electrical contact in the axial current application method. However, here, the object to be inspected is in the shape of a quadrangular prism, and no consideration is given to a cylindrical object to be inspected. Moreover, the magnetization method is only the axial current method, and composite magnetization by the coil method or the like is not taken into consideration.

The end face of an object to be inspected, which is an industrial product, may not be perfectly smooth due to the finishing accuracy of the surface, engraving, or the like. In some cases, the object to be inspected is conveyed obliquely with respect to the electrodes by automatic conveyance or the like. In that case, when magnetized by the axial current method, the object to be inspected and the electrode come into contact with each other at one point or a small area, and when the object is energized, a spark may occur. Furthermore, a difference in current density occurs near the end face of the object to be inspected, causing unevenness in the detection force in the circumferential direction.
In addition, when a copper contact portion is magnetized in a composite magnetic field of the coil method and the axial current method, magnetic poles are generated near the end face of the object under the influence of the coil magnetization. As a result, there is a problem that a pseudo pattern is generated near the end surface of the object to be inspected, and the detecting power in the circumferential direction is lowered.

Therefore, the object of the present invention is to prevent sparks generated on the electrode contact surface and reduce damage to the test object and electrodes when magnetic particle inspection is performed by the axial current method, and to combine the coil method and the axial current method. An object of the present invention is to eliminate unevenness generated near the end face of an object to be inspected during magnetization and to improve detection sensitivity.

In order to solve the above problems, the present invention provides a magnetic particle flaw detection apparatus that magnetizes an object to be inspected with composite magnetization by alternating current or half-wave rectification by a coil method and an axial current method,
The contact portion with the object to be inspected is made of iron and has a tapered recess at a predetermined angle.

Further, the tapered recess is characterized by being mortar-shaped.

Further, the object to be inspected has a prism shape, the tapered recess has an inverted quadrangular pyramid shape, and the contact between the object to be inspected and the contact portion is linear .

Further, the predetermined angle is 25 degrees or more and 45 degrees or less.

According to the present invention, in a magnetic particle flaw detection apparatus that magnetizes an object to be inspected with composite magnetization by alternating current or half-wave rectification by a coil method and an axial current method,
The part that comes into contact with the object to be inspected is made of iron and has a shape with a tapered dent at a predetermined angle, so that the object to be inspected and the contact part are in good contact, suppressing the generation of sparks, and furthermore, It is possible to uniformly magnetize the object to be inspected without concentrating the magnetic field on the contacting end of the object.

Furthermore, according to the present invention, since the tapered recesses are mortar-shaped, the contact portions are in good contact with the cylindrical test object, suppressing the generation of sparks and uniformly inspecting the test object. It can magnetize things.

Furthermore, according to the present invention, the object to be inspected is prismatic, the tapered recesses are in the shape of an inverted square pyramid, and the contact between the object to be inspected and the contact portion is linear . The contact portion is in good contact with the object to be inspected, the generation of sparks is suppressed, and the object to be inspected can be uniformly magnetized.

Furthermore, according to the present invention, since the predetermined angle is 25 degrees or more and 45 degrees or less, the object to be inspected and the contact portion are in good contact, the generation of sparks is suppressed, and the object to be inspected is uniformly magnetized. becomes possible.

They are the contact portion and the object to be inspected of the magnetic particle flaw detector according to the present embodiment. It is a perspective view of the contact portion of the magnetic particle flaw detector according to the present embodiment. (A) A contact portion of a conventional magnetic particle flaw detector and an object to be inspected with an oblique end face. (B) A contact portion of the magnetic particle flaw detector according to the present embodiment and an object to be inspected with an oblique end face. (A) A contact portion of a conventional magnetic particle flaw detector and an inclined object to be inspected. (B) A contact portion of the magnetic particle flaw detector according to the present embodiment and an inclined object to be inspected. It is a perspective view of a contact portion of a magnetic particle flaw detector according to another embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an iron contact portion 1 and an inspection object 2 of a ferromagnetic material such as iron for a magnetic particle flaw detector according to this embodiment. The contact portion 1 is formed in a tapered shape and contacts the object 2 to be inspected at two or more contact points. A perspective view is shown in FIG. The contact portion 1 has a mortar-like concave shape. By using the contact portion 1 having such a shape in a magnetic particle flaw detector, it is possible to stably hold the object 2 to be inspected and to stably pass an electric current since the object to be inspected 2 is in contact with two or more points. Therefore, magnetic poles are not formed at both ends of the object 2 to be inspected, and a magnetic field can be stably applied.

The contact portions 1 are paired and fix the object 2 to be inspected so as to sandwich the object 2 to be inspected from the left and right sides. The contact portion 1 is larger than the object 2 to be inspected. With such a configuration, the contact portion 1 can securely fix the object 2 to be inspected, allow a stable current to flow, and can stably apply a magnetic field, resulting in high accuracy. Magnetic particle inspection can be performed.

When an electric current is passed through the object 2 to be inspected by the axial energization method, the contact portion 1 becomes an electrode. Further, when applying a magnetic field to the object 2 to be inspected by the coil method, the contact portion 1 becomes a magnetic pole. Furthermore, there is also a method in which the axial energization method and the coil method are performed simultaneously, an alternating current is applied, and composite magnetization is used.
The invention of this patent is a contact part used in these methods, and the name is generically called "electrode for magnetic particle flaw detector".

In the axial energization method, an electric current is passed through the object 2 to be inspected, a magnetic field is generated in the circumferential direction, and the object 2 to be inspected is magnetized. A current of 50 to 5000 A is applied to the object 2 to be inspected, which is a large current. The voltage is 5-20V and this current is passed for 3-10 seconds. Therefore, if the electrical contact between the contact portion 1 and the test object 2 is poor, or if there is a point contact, sparking will occur and an accurate magnetic particle pointing pattern cannot be obtained.
In the coil method, an externally generated magnetic field is applied to the object 2 to be inspected in the axial direction. The magnetic field generated by the external coil is 0.5-2 Tesla. In this coil method, it is desirable that the contact portion 1 and the object 2 are in good contact with each other and that the contact portion 1 is made of iron. In the case of copper, the electrical conductivity is good, but since it is not a ferromagnetic material, the ends of the object to be inspected 2 become magnetic poles, and an accurate magnetic powder indication pattern cannot be obtained near the ends. Since the contact portion 1 is made of iron, a good magnetic circuit is formed between the contact portion 1 and the external coil, and the detection accuracy near the edge portion of the object to be inspected 2 is improved.

When the test object 2 has a columnar shape, it is preferable that the contact portion 1 has a mortar shape as shown in FIG. The angle of the depression of the contact portion 1 is represented by θ in FIG. 1, and is preferably 5 degrees or more and 60 degrees or less, more preferably 25 degrees or more and 45 degrees or less.

If the angle of the depression of the contact portion 1 is less than 25 degrees, the object 2 to be inspected does not slip within the electrode when the crimping pressure is weak, and the object 2 to be inspected does not move to the position where multiple points are contacted. Furthermore, if this angle exceeds 45 degrees, the contact portion 1 becomes longer than necessary, resulting in poor usability.

A conventional contact portion has a flat plate shape as shown in FIG. 3(A). The end surface of the test object 12 shown in FIG. 3A is not parallel to the contact portion 11 . Therefore, the contact becomes a point contact, and a gap 13 is formed between the object 12 to be inspected and the contact portion 11 . When a current is passed through this, a spark is generated, which may damage the object to be inspected 12 and the contact portion 11 . Also, an accurate magnetic powder indication pattern cannot be obtained.
On the other hand, as shown in FIG. 3B, the contact portion 1 of the present invention is recessed in the shape of a mortar. It is possible to make good contact with The contact between the contact portion 1 and the test object 2 is line contact or contact at two or more points.

Furthermore, FIG. 4 shows a case where the object to be inspected is oblique. FIG. 4A shows a conventional example, in which a gap 13 is formed between the object 12 to be inspected and the contact portion 11, and the contact becomes a point contact.
On the other hand, as shown in FIG. 4B, the contact portion 1 of the present invention is recessed in the shape of a mortar. becomes possible to come into contact with

The shape of the object to be inspected may be prismatic. In this case, the shape of the recess may be an inverted quadrangular pyramid, as shown in FIG. By using the contact part of this shape, the contact between the object to be inspected and the contact part becomes linear, suppressing the generation of sparks in the axial current method, and furthermore, in the composite magnetization by the coil method and the axial current method, Magnetic particle flaw detection can be performed satisfactorily.

As a method for magnetizing an object to be inspected, there is composite magnetization by alternating current between a coil method and an axial current method. Magnetic particle inspection can detect flaws oriented perpendicular to the direction of the applied magnetic field. The coil method is a method of generating a magnetic field in the axial direction of the object to be inspected, and the axial current method is a method of generating a magnetic field in a direction perpendicular to this. Furthermore, in the composite magnetization by alternating current, by synthesizing the magnetic field by the two methods, it is possible to generate a magnetic field whose directionality rotates, and it becomes possible to detect flaws in all directions by the rotating magnetic field.

Magnetic particle testing is a non-destructive testing method for detecting flaws and cracks on the surface of ferromagnetic materials such as steel. When a magnetic field is applied to a ferromagnetic material to be inspected, if there is a defect that blocks the magnetic flux on the surface or inside of the inspected material, magnetic poles appear at both ends of the defect, and the magnetic flux leaks to the surface of the material. When a magnetic powder liquid consisting of fluorescent magnetic particles to which a fluorescent substance is adhered is applied here, the magnetic particles are attracted to the leakage magnetic field corresponding to the scratched portion. Here, when ultraviolet rays are irradiated, the fluorescent substance of the magnetic particles adsorbed to the scratched portion emits light to form a fluorescent magnetic particle indicating pattern, and the scratched portion can be detected.

In the magnetic particle inspection method, first, the surface of a ferromagnetic material such as steel is cleaned with a solvent or the like, and then dried. Next, the ferromagnetic material is magnetized by an electromagnet or the like. There is a continuous method in which magnetic particles are applied while magnetized, and a residual method in which detection is performed after the magnetic field is removed. There are two types of magnetic powder: a dry method, in which magnetic powder is dispersed in the air, and a wet method, in which water or an organic solvent is used. Sprinkle magnetic powder to which a fluorescent substance is attached. If there is a scratch where the magnetic powder is sprinkled and there is a leakage magnetic field, the magnetic powder will stay there. When irradiated with ultraviolet light, the fluorescent substance attached to the magnetic powder emits light, and a pattern indicating the scratch is obtained. Determination of the damaged part is based on visual observation. Alternatively, it is imaged by an imaging device and automatically determined by a computer. A mark may be applied to the location where the wound is detected. In the case of automatic judgment by computer, the wound can be confirmed efficiently by marking automatically.

After the fluorescent magnetic particle inspection has been completed, the inspected object undergoes post-treatment such as degaussing, cleaning, and rust prevention.

The electrode for a magnetic particle flaw detector of the present invention is a magnetic particle flaw detector that magnetizes an object to be inspected using an axial energization method. An electrode for a magnetic particle flaw detector characterized in that it has a curved shape. Furthermore, in the magnetic particle testing equipment that is magnetized by the composite magnetization by the alternating current of the coil method and the shaft energization method, the contact part (contact part that is both a magnetic pole and an electrode) with the object to be inspected is made of iron and is tapered at a predetermined angle. An electrode for a magnetic particle flaw detector characterized by having a concave shape. Further, in the electrode for a magnetic particle flaw detector, the tapered recess has a mortar shape or an inverted quadrangular pyramid shape.

EXAMPLES Next, the present invention will be specifically described with reference to examples, but these examples are not intended to limit the present invention in any way.

(Example 1)
As Example 1 of the embodiment of the present invention, the contact portion 1, which is an electrode for a magnetic particle flaw detector made of iron and shown in FIG. 1, was produced. It had a diameter of 4 cm and a height of 1.5 cm with a taper angle of θ=30 degrees. The dent is mortar-shaped.
The test object 2 is a cylindrical iron rod with a diameter of 3 cm and a length of 35 cm. An artificial flaw having a width of 50 μm, a length of 5 mm, and a depth of 0.3 mm was formed on the inspection object 2 by a laser processing method. Scratches were made in the axial and circumferential directions, respectively.

When the object 2 to be inspected was sandwiched between the two contact portions 1, they were contacted linearly (circularly) in the circumferential direction. First, a magnetization test was performed by the axial current method. An alternating current of 500 A was passed for 5 seconds. At this time, no spark occurred. Next, a magnetization test was performed by the coil method. An external coil applied a magnetic field of 1 Tesla in the axial direction of the test object.

A fluorescent magnetic powder solution was applied to the object to be inspected. When irradiated with an ultraviolet black light, it was confirmed that fluorescent magnetic particles accumulated in the axial and circumferential scratches.

(Comparative example 1)
As Comparative Example 1, an iron contact portion 11 shown in FIG. 3A was produced. It is cylindrical and flat with a diameter of 4 cm and a height of 1 cm.
As the object 12 to be inspected, a cylindrical iron rod similar to that used in Example 1 was used.

It was found that the gap 13 shown in FIG. Sparks occurred when current was applied by the shaft current method, and a pseudo pattern was generated. When a magnetic field was applied in the axial direction by the coil method, no magnetic pole was generated at the end of the object 12 to be inspected because the contact portion 11 was made of iron, but a pseudo pattern was formed due to the presence of a gap.

(Comparative example 2)
As Comparative Example 2, a plate-like contact portion 11 having the same shape as in Comparative Example 1 was made of copper. The inspected object 12 is the same as that of the first embodiment and the first comparative example.

When the object 12 to be inspected was sandwiched between the two contact portions 11, a gap 13 was formed as in the first comparative example. Sparks occurred when current was applied by the shaft current method, and a pseudo pattern was generated. Further, when a magnetic field was applied in the axial direction by the coil method, since the contact portion 11 was made of copper, magnetic poles were generated at the ends of the object 12 to be inspected, forming a pseudo pattern.

(Results and Summary)
As Example 1, a mortar-shaped iron contact portion 1 was prepared as an electrode for a magnetic particle flaw detector. Further, as Comparative Example 1, a flat plate-shaped contact portion 11 made of iron was produced, and as Comparative Example 2, a flat plate-shaped contact portion 11 made of copper was produced. Using these electrodes, magnetic particle inspection was performed by the axial current method and the coil method. On the other hand, in Comparative Example 1, sparks were generated by the axial current method, and pseudo patterns were generated at the ends. Furthermore, in the coil method, since the contact portion 11 is made of iron, the end portion of the object to be inspected 12 does not become a magnetic pole. There has occurred. In Comparative Example 2, sparks were generated by the axial current method, and pseudo patterns were generated at the ends. In the coil method, since the contact portion 11 is made of copper, the end of the object to be inspected 12 becomes a magnetic pole, and a pseudo-pattern occurs at the end.

The electrode for a magnetic particle flaw detector according to the present disclosure can be used for magnetic particle flaw detection by the axial current method, the coil method, and composite magnetization by both of them. Since the electrodes are made of iron and are recessed in the shape of a mortar, they are suitable especially when the object to be inspected is cylindrical. In addition, for a prismatic object to be inspected, it is possible to prepare an iron electrode recessed in the shape of an inverted quadrangular pyramid.

REFERENCE SIGNS LIST 1 mortar-shaped contact portion 11 flat plate-shaped contact portion 2, 12 cylindrical test object 3 inverted quadrangular pyramid-shaped contact portion 13 gap θ taper angle

Claims (4)

In a magnetic particle flaw detection device that magnetizes an object to be inspected with composite magnetization by alternating current or half-wave rectification of the coil method and the axial current method,
An electrode for a magnetic particle flaw detector, wherein the contact portion with the object to be inspected is made of iron and has a tapered recess at a predetermined angle. The tapered recess is mortar-shaped,
The electrode for a magnetic particle flaw detector according to claim 1 . The object to be inspected has a prismatic shape,
The tapered recess has an inverted quadrangular pyramid shape,
The contact between the object to be inspected and the contact portion is linear ,
The electrode for a magnetic particle flaw detector according to claim 1 . The predetermined angle is 25 degrees or more and 45 degrees or less,
The electrode for a magnetic particle flaw detector according to any one of claims 1 to 3 .

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