JPS6026180B2 - Electromagnetic non-destructive testing method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nondestructive deep scratch device that nondestructively detects scratches in metal materials by applying electromagnetic phenomena.

Generally, a method of applying electromagnetic phenomena to deep scratches that occur in metal materials involves passing a current into the metal material being inspected and detecting the disturbance of the current caused by the presence of scratches as a change in the impedance of the detection coil. eddy current flaw detection, or magnetic flaw detection, which applies a magnetic field to the metal material being inspected (limited to magnetic materials) and detects the flux of magnetic flux from the flaw caused by the presence of flaws; In particular, automatic flaw detection methods include using a magnetically sensitive element to detect wax from the flaw, and directly converting magnetic flux into an electrical signal, each of which is applied depending on the shape of the material being inspected and the manufacturing process. , is widely used.

However, recent demands for improvements in flaw detection ability and deep flaw efficiency (speed) are shifting from the standpoint of precision inspection of 100% to more advanced methods in order to improve quality and reliability in various metal materials.

Furthermore, depending on the type of injury, some injuries may be of little concern, while others may lead to serious accidents. That is, it is important to perform defect detection for each type of flaw. To deal with these problems, individual efforts have been made to improve the flaw detection ability by making the detection end smaller and increasing the speed and stabilization of the flaw detection signal processing circuit, depending on the purpose.

However, the miniaturization of the detection end and flaw detection efficiency are contradictory conditions, and this can be solved by making the detection end follow the inspection target more accurately and at high speed, and by increasing the speed of the deep flaw signal processing circuit. There was no other way but to deal with it.
Furthermore, there is no definitive good method for classifying flaw signals;
It is said that it is most reliable to make deep scratches on the same material to be inspected many times with multiple types of detection ends. In this case, there are disadvantages such as poor efficiency in deep damage and high cost, and there has been a strong desire for an efficient method to meet these objectives. This invention was invented based on the above, and it is a completely new electromagnetic deep flaw method that simultaneously solves the problem of improving flaw detection ability and flaw detection efficiency, and also makes it possible to classify and detect flaw types. The aim is to provide equipment.

In other words, near the detection coil through high-frequency current,
Multiple magnetic cores are arranged at multiple points within the magnetic field created by the coil or on multiple equipotential lines including each of those points, and each magnetic core is fixed or moved on the equipotential lines while being inspected. The impedance of the coil is detected by each magnetic core, and the state of eddy current generated in the material to be inspected directly under each magnetic core and the state of the flux flowing from the flawed part of the material to be inspected are detected by scanning in close proximity to the material. By efficiently converting the impedance as a change in the impedance and detecting the change in the impedance of the detection coil, a deep wound operation can be performed.

Next, the deep wound method and device of the present invention will be explained with reference to embodiments shown in the drawings.

Figure 1 is a plan view of a detection coil in which two magnetic cores are arranged inside a circular detection coil among the detection coils that have multiple magnetic cores, which is the essential part of this invention, and Figure 2 is a similar circular detection coil. An embodiment of a detection coil in which magnetic cores are arranged twice inside and outside the shape coil is shown. In Figures 1 and 2, 1 is a circular detection coil, 2, 2', 2''..., 3, 3'
, 3″...4, 4', 4″..., and 5, 5
', 5''... are equipotential lines C2 on the concentric circle with the detection coil 1
, C3, C4, and C5, and FIGS. 1 and 2 each constitute a detection mechanism having multiple magnetic cores.

To explain the detection coil shown in FIG. 1 in more detail, the magnetic cores arranged on equipotential lines C2 and C3 have different shapes, and are designed to correspond to the types of scratches described later.
(Of course, they may have the same shape.) Figure 2 shows a case where the shape of the magnetic core is the same on the outside and inside of the detection coil 1, that is, on the equipotential lines C4 and C5. As in the figure, there is no problem even if the shape is different. The most characteristic feature of Fig. 2 is that on one equipotential line, for example, C
The magnetic cores 4, 4', 4''... on the magnetic field line C5 are fixed to the detection coil, and the magnetic cores 5, 4', 4'' on the other equipotential line C5 are fixed to the detection coil.
5', 5''... is to rotate on the circular orbit C5. Now, when a high frequency current is passed through the detection coil 1 as described above, C2, C3 are caused by the magnetic field created by the detection coil. , C4 and C5 are strengthened and magnetic cores 2, 2', 2''..., 3, 3', 3''...
..., 4, 4', 4''..., and 5, 5'
, 5" increases in proportion to its magnetic permeability, and the magnetic flux density locally increases just below each magnetic core on the surface of the material to be inspected (not shown) that is close to those cores. becomes high.

The direction of the local magnetic flux on the surface of the material to be inspected has both a component perpendicular to the surface of the material to be inspected (a plane parallel to the drawing) and a horizontal component. This is because none of the magnetic cores 2, 3, 4, and 5 are arranged at the center of the detection coil 1. (
If the magnetic core is placed at the center of the detection coil 1, there will be only a vertical component. ) Among these magnetic fluxes, the perpendicular component of the magnetic flux generates local eddy currents in the part directly below the magnetic core of the material to be inspected, and the arrival of flaws disturbs the distribution of eddy currents. On the other hand, the magnetic flux of the horizontal component results in the generation of magnetic flux due to flaws existing on the surface or under the surface of the material to be inspected. Changes in magnetic flux due to these scratches change the magnetic flux density inside each magnetic core.

Since the detection coil 1 includes all of these magnetic cores within its magnetic field, this appears as a change in the impedance of the detection coil, and by detecting this change in impedance, it is possible to detect flaws. In the flaw detection method according to the present invention, the magnetic cores are arranged on multiple equipotential lines, so the depth flaw sensitivity differs for each equipotential line, but the main purpose of arranging the magnetic cores in multiple places is to The purpose is to simultaneously detect different types of scratches with high sensitivity.

In other words, in the detection coil shown in Figure 1, the small magnetic core placed on C2 detects small point or linear scratches with high sensitivity, while the large magnetic core placed on C3 detects large area scratches, dents, etc. It is advantageous for detecting scratches and is ideal for detecting them simultaneously. In other words, the shape of the tip of the magnetic core,
This is because the size (that is, shape) is comprised of multiple types. The tip shapes of the respective magnetic cores in one equipotential line can also be made different.

In addition, in the detection coil shown in Figure 2, by selecting C4 and C5 as equimagnetic potential lines and fixing the magnetic core on C4 and rotating the magnetic core on C5 around it, the magnetic core on C4 will be the one to be inspected. It is advantageous for detecting horizontal scratches that are perpendicular to the scanning direction of the material, while the rotating magnetic core on C5 is mainly effective for detecting vertical scratches, and in this case, multidirectional scratches can be detected simultaneously. perfect for doing so. When the cores on each equipotential line coexist in a fixed or moving state as in the embodiment shown in FIG. 2, care must be taken to prevent them from interfering with each other. Next, an embodiment of the present invention will be explained with reference to FIG.

FIG. 3 is a block diagram of an apparatus according to an embodiment of the present invention, in which IA and IB are the same two detection coils having multiple magnetic cores according to the deep scratch method, 6 is a planar metal body which is a material to be inspected; 7
Reference numeral 8 indicates an offset detection circuit, 8 an amplifier, and 9 and 9' two signal analyzers capable of performing phase discrimination, frequency discrimination, etc., respectively. The detection coils IA and IB scan and cause deep scratches on the inspected material 6 while emitting deep scratch signals containing various types of scratch signals every moment, as described in detail in the deep scratch method.

These two detection coils IA and IB are set so that the deep flaw output signal thereof becomes zero when there is no flaw in the inspected material 6 by a differential detection circuit 7 such as an AC bridge that differentially detects the flaw. Now, in such a scanning flaw detection state between the inspected material 6 and the detection coils IA and IB, when a flaw arrives directly under the magnetic core of the detection coil, an output is output to the differential detection circuit 7 by the above-mentioned flaw detection mechanism. A scratch signal appears. As mentioned above, this deep damage signal can be detected as a high frequency voltage in response to the high frequency current flowing through the detection coil, and after this deep damage signal is amplified by the amplifier 8, it is possible to perform signal analysis using phase discrimination. Therefore, it is possible to further discriminate the frequency components of the deep flaw signal and perform flaw detection with a good S/N ratio. Reference numerals 9 and 9' denote signal analyzers for performing the above-mentioned signal analysis, and the reason why two series of these are provided is that the detection coil IA or IB has double (multiple) magnetic cores and two types (many types) of them. This is to allow each signal to be analyzed optimally depending on the fact that it includes a flaw signal.

In the above embodiments, the shape of the detection coil is circular, but it is not limited to a circle, and may be freely designed depending on the shape of the material to be inspected and the purpose of deep scratches.

In addition, although the shape of the tip of the magnetic core is circular in all examples, the shape of the flaw can be optimally designed depending on the purpose of flaw detection, such as a horizontally long rectangle in the case of a linear horizontal flaw.

Further, in the detection coil having the magnetic core arrangement shown in FIG. 1, an embodiment may be considered in which the entire magnetic core is rotated at a constant speed on the isomagnetic grain lines C2 and C3 with respect to the detection coil 1.

In this case, the effect of facilitating frequency discrimination of the flaw detection signal is produced without being affected by the relative scanning flaw detection speed between the detection coil and the material to be inspected. As detailed above, this invention has multiple magnetic cores arranged on a plurality of equipotential lines near the detection coil, so it is equipped with two flaw detection methods: eddy current flaw detection and magnetic flaw detection. At the same time, with only one detection coil, the detection sensitivity is not lowered at all compared to the conventional electromagnetic deep wound method of this kind, and deep wounds can be detected over a wide range at the same time. Furthermore, the biggest effect of the multiplexed magnetic core arrangement is that it enables flaw detection and signal analysis for each type of flaw.
Multi-purpose flaw detection can be performed simultaneously, ensuring a revolutionary improvement in flaw detection technology.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of the detection coil which is the main part of this invention, and Fig. 2 is a plan view showing the shape and positional relationship of the circular detection coil and the magnetic cores arranged in multiple layers therein. FIG. 3 is a diagram showing another embodiment of the coil, and is a plan view showing the magnetic cores arranged inside and outside the circular detection coil and their positional relationship, and FIG. 3 is a block diagram of the embodiment device according to the present invention. 1, IA, IB...detection coil, 2, 2', 2'', 3, 3
', 3'', 4, 4', 4'', 5, 5', 5''...
・Magnetic core, 6... material to be inspected, 7... differential detection circuit, 8... amplifier, 9... phase discrimination circuit (frequency discrimination circuit) ). Hair' Shida 2 drawings 3 boxes

Claims (1)

[Claims] 1. In the vicinity of the detection coil installed close to the material to be inspected, any plurality of points other than its geometric center, or on a plurality of equimagnetic potential lines including each of those points. Deploying magnetic cores at multiple points,
The magnetic core, the detection coil, and the material to be inspected are moved and scanned relative to each other, and defects in the material to be inspected are detected by detecting changes in impedance of the detection coil. Electromagnetic non-destructive testing method. 2. A magnetic core on an isomagnetic potential line that includes any number of points in the vicinity of the detection coil and excluding its geometric center is moved so as to be displaced relative to the detection coil, and 2. The electromagnetic non-destructive flaw detection method according to claim 1, wherein the magnetic core on the equimagnetic potential line including each of the other plurality of points is fixed. 3. A plurality of magnetic cores arranged on any one of the plurality of isomagnetic potential lines have multiple types of tip shapes, or magnetic cores with the same type of tip shape are arranged on one equipotential line. The magnetic core is configured with a plurality of types of tip shapes such that other magnetic cores with the same type of tip shape are arranged on other equipotential lines, so that a plurality of types of defects can be detected. An electromagnetic nondestructive flaw detection method according to claim 1 or 2. 4. Arrange magnetic cores at any number of points other than the geometric center of the detection coil installed close to the material to be inspected, or at multiple points on multiple equipotential lines including each of those points. At the same time, the magnetic cores are moved to be displaced relative to the detection coil on their respective equipotential lines, and the change in impedance of the detection coil having the moving magnetic core is detected to detect defects in the material to be inspected. An electromagnetic non-destructive flaw detection method characterized by detecting. 5. Are multiple magnetic cores arranged on any one of multiple equipotential lines composed of multiple types of tip shapes, or are magnetic cores with the same type of tip shapes arranged on one equipotential line? Another magnetic core with the same type of tip shape is arranged on the equimagnetic potential line of the magnetic core, so that the magnetic core is configured with a plurality of types of tip shapes, and a plurality of types of defects can be detected. An electromagnetic nondestructive flaw detection method according to claim 4. 6 A detection coil installed close to the material to be inspected, and any plurality of points in the vicinity of this detection coil other than its geometric center, or multiple points on a plurality of equipotential lines including each of those points. a differential detection circuit that is provided with two detection mechanisms consisting of magnetic cores arranged in multiple directions and differentially detects them;
It is equipped with a plurality of signal analysis circuits that individually analyze the flaw detection signals from the differential detection circuit, so that multiple types of flaws can be individually and simultaneously detected using the flaw detection signals from the detection coil. An electromagnetic non-destructive flaw detection device characterized by: