JPH10170620A - Magnetism inspection method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily inspect a changing degree to a magnetic condition from a nonmagnetic condition by arranging a magnet means at an interval from an inspection object, and detecting a part of a magnetic flux of not passing through the inspection object among a magnetic flux reaching an S pole from an N pole. SOLUTION: When an inspection device 10 is arranged so that a contact surface 32 of a spacer 14 comes into contact with an outside surface of an inspection object 30, in the case where the inspection object 30 is a nonmagnetic material, a magnetic flux of a permanent magnet 20 passes through passages 40 and 42. A part of a magnetic flux 40 reaching an S pole 28 from an N pole 26 to constitute the same magnetic circuit on the inspection object 30 side, passes through a Hall element 34 of a magnetic detector 16. A part of the magnetic flux 40 is detected by the magnetic detector 16, and density of the magnetic flux passing through the Hall element 34 is found on the basis of an output signal of the magnetic detector 16, and is visibly displayed. Since this magnetic flux density changes by depending on a change (a change to a magnetic condition from a nonmagnetic condition) in magnetic permeability of the inspection object 30, magnetic permeability of the inspection object 30 and a changing degree to a magnetic condition from a nonmagnetic condition, can be detected from the obtained magnetic flux density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for inspecting the magnetism of a test object such as a metal material.

[0002]

2. Description of the Related Art Metal materials such as stainless steel having an austenitic structure are so-called non-magnetic and have a very low magnetic permeability, so that they are not attracted to magnets.

[0003] However, the austenite structure has the property of being partially transformed into a martensite structure under the influence of temperature, stress or strain. Since the martensite structure exhibits ferromagnetism, when such a transformation occurs in a metal material, the permeability of the metal material increases, and the metal material becomes attracted to the magnet.

[0004] In addition, alloys containing nickel, chromium, tungsten, or the like as a main component and used for piping of heat treatment equipment and the like are initially non-magnetic, but are also known to become magnetic with deterioration. ing.

As described above, in a material that changes from non-magnetic to magnetic, the change may mean fatigue or deterioration of the material. Therefore, it is important to easily inspect the degree of the change.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to make it possible to easily inspect the degree of change from non-magnetic to magnetic.

[0007]

A magnetic inspection method according to the present invention comprises:
A magnet means having a pole and an S pole is arranged at a distance from the test object, and of the magnetic flux from the N pole to the S pole,
The method includes arranging a magnetic detection element at a position where a part of a magnetic flux that does not pass through the test object passes, and detecting a part of the magnetic flux with the magnetic detection element.

According to the magnetic inspection apparatus of the present invention, there are provided magnet means having an N pole and an S pole, a nonmagnetic spacer for defining a distance between the N pole and the S pole of the magnet means and an object to be inspected, A magnetic detecting element disposed at a position where a part of a magnetic flux that does not pass through the test object among the magnetic fluxes from the N pole to the S pole passes, and processing means for processing an output signal of the magnetic detecting element. Including.

The magnetic flux from the N pole of the magnet means passes from the N pole via the spacer, the inspection object and the magnetic detection element, and further reaches the S pole of the magnet means via the spacer. The higher the magnetic permeability of the device under test, the greater the amount of magnetic flux that obtains such a path, but the smaller the amount of magnetic flux that does not pass through the device under test, and therefore the smaller the amount of magnetic flux that passes through the magnetic sensing element. The amount of magnetic flux passing through the magnetic sensing element changes inversely with the change in the magnetic permeability of the test object such as stainless steel.

The magnetic detecting element detects a part of the magnetic flux that does not pass through the test object as a magnetic flux amount or a magnetic flux density. The amount or density of the detected magnetic flux is proportional to the magnetic flux passing through the magnetic detection element, and decreases as the magnetic permeability of the test object increases. Therefore, the detected magnetic flux amount or magnetic flux density is
The smaller the permeability of the test object and the degree of change from non-magnetic to magnetic, the smaller. Therefore, the magnetic permeability of the test object and the degree of change from non-magnetic to magnetic can be known from the detected magnetic flux amount or magnetic flux density.

According to the present invention, the magnet means is arranged at a distance from the object to be inspected, and a part of the magnetic flux from the N pole to the S pole of the magnet means which does not pass through the object to be inspected is magnetically detected. Since the detection is performed by the element, the output signal of the magnetic detection element changes depending on the change in the magnetic permeability of the test object, and as a result, the degree of magnetism of a material such as stainless steel, which changes from non-magnetic to magnetic. Can be easily inspected based on the output signal of the magnetic detection element.

[0012] The detecting element may be arranged in the spacer. By doing so, the position of the detecting element with respect to the N pole and the S pole of the magnet means becomes constant, and the inspection becomes accurate.

[0013] The spacer may have an abutting surface that abuts on the test object. With this configuration, the intervals between the N and S poles of the magnet unit and the non-inspection body are constant, so that correct inspection can be performed.

In a preferred embodiment, the permanent magnet N
The pole and the south pole are directed toward the test object, and the contact surface of the spacer is shaped to conform to the shape of the outer surface of the test object.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2, an inspection apparatus 10 includes a magnet means 12 having an N pole and an S pole.
And a non-magnetic spacer 14 mounted on the magnet means.
And a magnetic detector 16 for detecting a part of the magnetic flux from the magnet means 12, and a signal processor 18 for processing an output signal of the magnetic detector.

The magnet means 12 assembles a pair of plate-shaped permanent magnets 20 magnetized in the thickness direction on a plate-shaped support member 22 at intervals so that the two permanent magnets 20 form the same magnetic circuit. ing. The two permanent magnets 20 are assembled to the support member 22 with an adhesive or the like in a state where the magnetization directions are opposite and one different magnetic pole surface is in contact with one surface of the support member 22. The other different magnetic pole faces 26 and 28 of the two permanent magnets 20 act as the north and south poles of the magnet means 12, respectively. The support member 22 is made of a non-magnetic material in the illustrated example, but may be made of a magnetic material. Further, the support member 14 may not be provided.

The spacer 14 is made of a non-magnetic material in the shape of a plate. The spacer 14 is formed such that one surface in the thickness direction is in contact with the N-pole 26 and the S-pole 28 of the magnet 12.
Is assembled with an adhesive or the like. The other surface of the spacer 14 is a contact surface 32 that is in contact with the specimen, that is, the test object 30. The thickness dimension of the spacer 14 is determined such that the change in the magnetic flux density detected with respect to the change in the magnetic permeability of the test object 30 is maximized.

In the illustrated example, the contact surface 32 is
Since the abutment portion 0 is flat, the abutment portion is flat, but has a shape corresponding to the shape of the abutment portion of the test object, particularly the outer surface, for example,
A concave or convex surface such as an arc, a Z, a V, or a U may be used. In the example shown in FIG. 3, the contact surface 32 of the spacer 14 is an arc-shaped concave surface having a radius of curvature substantially equal to the radius of curvature of the contact portion of the device under test 30.

In the magnetic detector 16, a Hall element 34 as a magnetic flux density detecting element is disposed at the tip of an elongated inspection head 36. The magnetic detector 16 controls the magnet unit 12 and the spacer 14 so that, of the magnetic fluxes from the north pole 26 to the south pole 28 of the magnet unit 12, the magnetic flux that does not pass through the test object 30 passes through the Hall element 34 at substantially right angles. Attached to.

When the magnetic detector 16 is attached to the magnet means 12 and the spacer 14, the Hall element 3
4 is arranged near the north pole 26 and the south pole 28 of the magnet means 12. In the illustrated example, a hole for inserting the tip of the inspection head 36 into the spacer 14 from above is formed by the magnet unit 1.
2 and the spacer 14. However, the tip of the inspection head 34 may be inserted into the spacer 14 from the side.

The signal processor 18 obtains the density of the magnetic flux passing through the Hall element 34 based on the detection signal of the Hall element 34, and displays the obtained magnetic flux density visually. As such a signal processor 18, a signal processing unit of a magnetic flux density meter using a Hall element can be used.

The inspection device 10 is provided with the contact surface 3 of the spacer 14.
2 is arranged with respect to the inspected body 30 so as to contact the outer surface of the inspected body 30. In this state, if the test object 30 is a non-magnetic material, the magnetic flux from the permanent magnet 20 passes through paths 40 and 42 indicated by solid lines in FIG.

A part of the magnetic flux 40 from the north pole 26 to the south pole 28 constituting the same magnetic circuit on the inspection object 30 side passes through the Hall element 34 of the magnetic detector 16. For this reason, the magnetic detector 16 detects a part of the magnetic flux 40 and outputs the signal to the signal processor 1.
8 is a Hall element 34 based on the output signal of the magnetic detector 16.
The density of the magnetic flux passing through is determined, and the determined magnetic flux density is visually displayed.

In the test object 30 made of a nonmagnetic material such as stainless steel, the magnetic properties gradually change from nonmagnetic to magnetic due to fatigue, deterioration, and the like, and the magnetic permeability gradually increases. When the magnetic permeability of the test object 30 increases, the magnetic flux 40
Of these, the magnetic flux passing through the device under test 30 increases, and the magnetic flux passing through the Hall element 34 decreases accordingly.
Output signal decreases. As a result, the magnetic flux density obtained by the signal processor 18 decreases.

According to the inspection apparatus 10 as described above, the magnetic flux density obtained by the signal processor 18 changes depending on the change in the magnetic permeability of the test object 30 (change from non-magnetic to magnetic). From the magnetic flux density obtained by the signal processor 18, the magnetic permeability of the test object 30 and the degree of change from non-magnetic to magnetic can be known, and as a result, the test object such as stainless steel changes from non-magnetic to magnetic. The degree of fatigue or deterioration of No. 30 can be easily known with a simple device.

The degree of fatigue or deterioration of the test object 30 depends on the fact that the amount of magnetic flux passing through the magnetic detection Hall element 34 changes in reverse to the change in the magnetic permeability of the test object 30. It can be determined that a larger value is smaller. The magnetic flux density obtained by the signal processor 18 may be stored in a storage circuit.

The inspection apparatus 50 shown in FIG. 4 has the same configuration as the inspection apparatus 10 shown in FIG. 1 except that a horseshoe-shaped permanent magnet 54 is used as the magnetic detection means 52. Therefore, similarly to the inspection apparatus 10, the inspection apparatus 50 can also know the degree of change of the inspection object from non-magnetic to magnetic.

The present invention is not limited to the above embodiment. For example, an element for detecting the amount of magnetic flux, such as a coil, may be used as the magnetic detection element instead of the Hall element for detecting the magnetic flux density.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of an inspection apparatus of the present invention.

FIG. 2 is a longitudinal sectional view of the inspection device shown in FIG.

FIG. 3 is a longitudinal sectional view showing a modification of the inspection apparatus shown in FIG.

FIG. 4 is a view showing another embodiment of the inspection apparatus of the present invention.

[Explanation of symbols]

 10, 50 Inspection device 12, 52 Magnet means 14 Spacer 16 Magnetic detector 20, 54 Permanent magnet 26 N pole 28 S pole 30 Inspection object 32 Contact surface 34 Hall element 35 Inspection head

Claims (5)

[Claims] A magnet means having an N pole and an S pole is arranged at a distance from an object to be inspected, and a part of a magnetic flux from the N pole to the S pole that does not pass through the object to be inspected is A magnetic inspection method, comprising: arranging a magnetic detection element at a position passing therethrough, and detecting a part of the magnetic flux with the magnetic detection element. 2. A magnet means having an N pole and an S pole, a non-magnetic spacer for defining a distance between the N pole and the S pole of the magnet means and an object to be inspected, and A magnetic inspection device, comprising: a magnetic detection element disposed at a position where a part of a magnetic flux that does not pass through a device to be inspected among magnetic fluxes reaching a pole passes; and processing means for processing an output signal of the magnetic detection element. 3. The magnetic inspection apparatus according to claim 2, wherein the detection element is disposed in the spacer. 4. The magnetic inspection apparatus according to claim 2, wherein the spacer has an abutting surface that abuts on an object to be inspected. 5. The magnetic inspection apparatus according to claim 2, wherein the north pole and the south pole are directed to an object to be inspected.