JPS59153166A - Flaw detection probe - Google Patents

Abstract

PURPOSE:To enable a wide range of flaw detection on a convex side of long sized work to be inspected by winding an excitation coil around the peripheral rim of a detecting surface. CONSTITUTION:A flaw detection probe 14 has an E-shaped body 16. A U-shaped cut is formed in pole sections at ends thereof and a concave detecting surface 18 arranged inside the cut to face a convex surface 12 to be inspected therealong with a specific clearance therebetween. When an AC exciting current is applied to the excitation coil 20 and a magnetic flux generated reaches a flat steel 10, an eddy current develops near the surface layer of the flat steel 10 pierced by the flux. When a flaw exists on the convex side 12, the flow of the eddy current changes and thus, the presence of the flaw can be detected by checking the level of the change with a detection coil 22. As the excitation coil 20 is wound around the peripheral rim of the detecting surface 18, a high detection sensitivity can be obtained even though the position of the flaw is deviated from the center of the convex side 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flaw detection probe that electromagnetically detects the presence or absence of flaws by applying magnetic flux to the surface to be inspected of a member to be inspected to generate eddy currents and detecting changes in the eddy currents. In particular, the present invention relates to a flaw detection probe that provides high detection sensitivity over the entire convex side surface of a longitudinal member to be inspected that faces the flaw detection surface of the flaw detection probe.

Generally, a flaw detection probe used to detect flaws on the convex side surface of a longitudinal inspected member has a flat flaw detection surface, and when the flaw detection surface is opposed to the convex side surface of the inspected surface, there is a gap. Although the detection sensitivity is high near the center where the flaw detection surface is small, there is a drawback that the gap becomes large near the periphery of the flaw detection surface and sufficient detection sensitivity cannot be obtained. In contrast, flaw detection probes have been considered that include a concave flaw detection surface that runs along the convex side surface of the member to be inspected and faces with a predetermined gap in between.

For example, patent application No. 57-1088 filed earlier by the present applicant.
This is what is described in No. 0.

According to such a flaw detection probe, the flaw detection surface is formed in a concave shape corresponding to the convex curved shape of the surface to be inspected, and the opening width and depth of the flaw detection surface cover a portion existing inside the width of the surface to be inspected. Even if the surface to be inspected is curved in a convex shape, the width that can be detected can be widened, and the detection sensitivity can be increased over the entire width.

However, according to such conventional flaw detection probes, the excitation coil is generally configured by being wound around the outer circumference of the flaw detection probe. In the case of a component, the component to be inspected is a paramagnetic material, so the magnetic flux applied from the testing surface is not actively guided into the component to be inspected, and the magnetic flux is distributed between the bottom of the concave testing surface, which is the shortest distance. The tendency to concentrate was inevitable. For this reason, sufficient detection sensitivity could not always be obtained in the periphery of the convex surface to be inspected.

The present invention has been made against the background of the above circumstances,
The purpose is to obtain sufficient detection sensitivity not only at the center of the convex side surface (surface to be inspected) of the elongated inspected member, but also at the periphery (both sides), and to cover a wide range of flaw detection areas. The purpose of the present invention is to provide a flaw detection probe with the following features.

In order to achieve such an object, the gist of the present invention is to provide a main body provided with an excitation coil, and a magnetic pole formed in the magnetic pole portion of the main body, extending along the convex side surface of the elongated member to be inspected and at a predetermined gap. In the flaw detection probe, the excitation coil is connected to the flaw detection surface, and the flaw detection probe electromagnetically detects flaws existing on the convex side surface by being moved relative to the inspected member. The reason is that it is wound along the outer periphery of the .

In this way, since the excitation coil is wound along the outer periphery of the flaw detection surface, magnetic flux is generated almost uniformly from the entire concave flaw detection surface, and the magnetic flux is high over the entire surface to be inspected facing the flaw detection surface. This provides high detection sensitivity and a wide area that can be detected.

Hereinafter, an embodiment of the present invention will be explained in detail based on the drawings.

In FIG. 1, flat! which is a longitudinal member to be inspected! 111
0 is made to run in the longitudinal direction via hot rolling rollers (not shown). Convex side surface 12 of flat bar 10
is fitted into a U-shaped notch formed in the magnetic pole portion of the flaw detection probe 14, which is provided in a fixed position.

The flaw detection probe 14 includes an E-shaped main body 16 made of a magnetic material. The above-mentioned U-shaped notch is formed in the magnetic pole portion at each end of the main body I6, so that a concave flaw detection surface 18 is provided inside the magnetic pole portion, and the flaw detection surface 18 extends along the convex side face I2 and at a predetermined position. They are facing each other with a gap between them. That is, the width W of the U-shaped notch forming the flaw detection surface 18 is set to a value equal to the plate thickness T of the flat steel 10 plus twice the predetermined gap. The depth D is set to be sufficiently larger than the radius of curvature r of the convex side surface 12, so that when the flaw detection surface 18 faces the convex side surface 12 with a predetermined gap in between, both ends of the flaw detection surface 18 are flat steel. The upper and lower planes of 10 are sufficiently opposed to each other.

Then, the excitation coil 20 and the detection coil 22 are connected to the main body 1.
The magnetic pole portions 6 are similarly wound along the outer periphery of the flaw detection surface 18, respectively. That is, as shown in FIG. 2, the excitation coil 20 has two U-shaped parts 24 and two U-shaped parts on the outside of the U-shaped cutout that forms the flaw detection surface 18 in the magnetic pole part of the main body 16. The connecting part 26 is located on the end face of the main body 16 to connect the ends of the parts 24 and is attached to the main body 16 in an electrically insulated state.

In the flaw detection probe 14 configured as described above, when an alternating current excitation current of several tens of J (Hz to several hundred KHz) is applied to the excitation coil 20, the magnetic flux generated thereby is directed toward the flaw detection surface 18. When such magnetic flux is applied to the flat steel 10, an eddy current is generated near the surface layer of the flat steel 10 through which the magnetic flux penetrates, and the magnetic flux generated by this eddy current is applied to the detection coil 22. This eddy current is generated near the surface of the convex side surface 120, which is the surface to be inspected, and if there is a flaw on the convex side surface 12, this flaw changes the flow of the eddy current. However, the presence of a flaw is detected by detecting the magnitude of this change in eddy current by the detection coil 22.

At this time, the excitation filter 2o is wound along the outer periphery of the flaw detection surface 18, so even if the flaw position deviates from the center of the convex side surface 12, as shown in FIG. You can get it. That is, in FIG. 3, the magnitude of the signal when the flaw position is at the center of the convex side surface 12 is set as 100, and the magnitude of the flaw signal when the flaw position of the same size is moved away from the center. The solid line represents the change in the flaw detection surface 18 shown by the broken line, or when the flaw detection surface 18 shown by the two-dot chain line is concave but the excitation coil is wound around the outer periphery of the main body. It can be seen that higher detection sensitivity can be obtained over a wide range compared to the above, and flaws can be detected on a wide area of the convex side surface 12. This is because the excitation coil 20 is wound along the outer periphery of the flaw detection surface 18, so that magnetic flux is generated almost uniformly from the entire flaw detection surface 18, and the magnetic flux is applied to the convex side surface 12 of the flat bar 10. This is the result, and this can be understood as follows. That is, in a conventional flaw detection probe in which the excitation coil 20 is simply wound around the outer periphery of the main body, especially when the flat bar 10 is a paramagnetic material such as high-temperature steel or aluminum, the flaw detection surface The magnetic flux generated at 18 is the flat steel 1
Since it is extremely rare for the magnetic flux to be guided to 0, the magnetic flux selects the short path with the lowest magnetic resistance and flows, as shown in A in FIG. . However, the flaw detection probe 14 of this embodiment in which the excitation coil 20 is wound along the outer periphery of the flaw detection surface 18
Since the excitation coil 20, which is a magnetic flux generation source, is located along the flaw detection surface 18, magnetic flux is similarly generated from the bottom and both ends of the flaw detection surface 18, as shown in FIG. 5B. Magnetic flux is generated uniformly over substantially the entire flaw detection surface 18.

As a result, high detection sensitivity can be obtained over the entire surface to be inspected that the flaw detection surface 18 faces.

Although the embodiment of the present invention has been described above based on the drawings, the present invention can also be applied to other aspects. still,
In the following description, parts common to those in the above-mentioned embodiments are given the same reference numerals, and the description thereof will be omitted.

For example, the flaw detection probe 14 of this embodiment is particularly effective on paramagnetic materials such as high-temperature steel and aluminum materials, but is also extremely effective even on ferromagnetic materials such as steel at room temperature.

Furthermore, the convex side surface may have a protruding triangular cross section as shown in FIG. In such a case, the flaw detection surface 18 should be adjusted to correspond to such a convex side surface.
is formed in a concave shape, and the excitation coil 20 is located on the flaw detection surface 18.
It suffices if it is wound along the outer periphery of the. Further, as shown in FIG. 7, the member to be inspected may be prismatic, and the convex side surface 12 of the corner may be inspected. Similarly, as shown in FIG.
By preparing a pair of flaw detection probes 14 facing each convex side surface, the entire cylindrical side surface can be inspected for flaws.

Furthermore, the flaw detection probe 14 of the above-described embodiment can be modified in various ways in the shape of its magnetic pole and the shape of the excitation coil 20, as shown in FIGS. 9 and 1O.

In short, if the flaw detection surface 18 is formed so as to face the convex side surface 12 of the inspected member with a predetermined gap therebetween, and the excitation coil 20 is further wound along the outer periphery of the flaw detection surface. It's good.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a state in which a member to be inspected is being inspected using a flaw detection probe according to an embodiment of the present invention. FIG. 2 is an enlarged view of the excitation coil provided in the embodiment of FIG. 1. FIG. 3 is a chart comparing the detection sensitivity of the flaw detection probe shown in FIG. 1 with that of a conventional device. FIG. 4 is a diagram explaining the magnetic flux path of the conventional device, and the fifth
The figure is a diagram illustrating the magnetic flux path in the embodiment of FIG. 1. FIGS. 6 to 8 are diagrams each showing an example of the present invention in which the embodiment is modified according to the cross-sectional shape of the member to be inspected. FIG. 9 and FIG. 1O are diagrams each showing an example of another embodiment of the exciting coil winding shape in the present invention. 10: Flat steel (part to be inspected) 12: Convex side surface 14: Flaw detection probe 16: Main body
18: Flaw detection surface 20: Excitation coil Applicant: Daido Steel Co., Ltd. Figure 1 Figure 3 Figure 8 Figure 9 Figure 10

Claims (1)

[Claims] A main body provided with an excitation coil, and a concave flaw detection surface formed on a magnetic pole part of the main body and facing along a convex side surface of a longitudinal test member with a predetermined gap therebetween, the test member A flaw detection probe that electromagnetically detects flaws existing on the convex side surface by being moved relative to the flaw detection probe, characterized in that the excitation coil is wound along the outer periphery of the flaw detection surface.