JPS637346B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electromagnetic ultrasonic probe, and particularly to an electromagnetic ultrasonic probe that is most suitable for a probe that requires strength.

FIGS. 1 and 2 show an example of the structure of a probe used in electromagnetic ultrasonic flaw detection.

FIG. 1 is a side sectional view of a conventional probe, and FIG. 2 is a bottom view of the probe.

A probe having a structure capable of contacting a material to be inspected (for example, a steel material or a steel pipe) 1 is composed of an excitation coil 2, an iron core 3, a transmitting/receiving coil 4, and a bottom plate 5. The excitation coil 2 is wound around an E-shaped iron core 3, is supplied with DC power from the outside, and constantly generates a DC magnetic field. iron core 3
A transmitting/receiving coil 4 is provided at the tip of the central magnetic pole. In order to protect the excitation coil 2 and the transmitter/receiver coil 4, a bottom plate 5 is provided on the contact surface with the specimen 1.

A pulse current is applied to the transmitting/receiving coil 4 from a pulse generator (not shown), thereby generating a changing magnetic flux and generating an eddy current in the specimen 1. Due to the interaction between this eddy current and the aforementioned DC magnetic field,
A changing strain (Fleming's law) occurs in the test material, and the changing strain propagates through the test material as an ultrasonic wave.
Defects in the material to be inspected and ultrasonic waves reflected from the bottom surface are detected by the transmitter/receiver coil in a process reverse to that described above.

In such a probe, the bottom plate 5 must have the following characteristics in addition to the above-mentioned protective function.

(1) Must have sufficient mechanical strength as a protective plate.

(2) In order to efficiently apply DC magnetic flux and variable magnetic flux to the test material, the lower part of the central leg of the iron core (transmitting/receiving coil attachment part) should be made as thin as possible, especially.

(3) It must be non-magnetic so that the bottom plate 5 and the iron core 3 do not form a magnetic closed circuit in order to apply DC magnetic flux to the material to be tested.

(4) Since changing magnetic flux is applied to the material to be tested, there should be no changing magnetic flux blocking effect (shielding effect), that is, it should be non-conductive.

For example, as satisfying the characteristics (3) and (4),
Reinforced plastic etc. can be considered, but in order to satisfy (1), the thickness will inevitably be thicker (approximately 3 mm).
(2) cannot be satisfied, and in order to satisfy (2), a thickness of 0.5 mm or less is desirable. ) was inevitably inefficient.

In this way, in the past, it has not been possible to create a probe that completely satisfies the conditions required for the bottom of the probe, and it has not been possible to create a probe that completely satisfies the conditions required for the bottom of the probe, and it has been difficult to create a probe that meets the requirements of (1) (mechanical strength) or (2) (efficiency). One or the other had to be sacrificed.

An object of the present invention is to provide an electromagnetic ultrasound probe having sufficient strength and efficiency.

In the present invention, the bottom plate of the probe is divided into two parts: a DC excitation coil holding plate and a transmitting/receiving coil protection plate. ) to ensure strength, and the transmitting/receiving coil protection plate is made of a non-conductive and preferably high magnetic permeability material (for example, a ferrite core), thereby solving the conventional drawbacks.

FIG. 3 is a side sectional view showing an embodiment of the present invention, and FIG. 4 is a bottom view of the embodiment.

The number and names of the members constituting the probe are the same except for the bottom. The bottom plate is as shown in the figure.
It is divided into a protection plate 6 for the transmitting/receiving coil 4 and a holding plate 7 for the DC excitation coil 2. The protective plate 6 is non-conductive, and more preferably is made of a material with high magnetic permeability (eg, ferrite).
As a result, direct current magnetic flux and variable magnetic flux can be efficiently transmitted to the test material 1, and eddy currents are not generated in this material, so the thickness of the protective plate can be increased to protect the transmitter/receiver coil 4. There is no negative effect either.

On the other hand, the holding plate 7 is made of a non-magnetic material (for example, stainless steel). Because the material has sufficient mechanical strength as a protective plate and is non-magnetic,
There is no possibility that a magnetic closed circuit will occur between the central leg and both end legs of the iron core 3, and the strength required to protect the DC excitation coil 2 can be sufficiently ensured by selecting the material.

FIG. 5 is a side sectional view showing another embodiment of the present invention, and FIG. 6 is a bottom view of the embodiment.

The embodiment shown in FIG. 3 uses an E-shaped core, but the embodiment shown in FIG. 5 uses a U-shaped core. In this case, a protective plate 6 is placed on the head of the leg on which the transmitting/receiving coil 4 of the iron core 8 is mounted so as to cover the transmitting/receiving coil 4, and a retaining plate 7 is placed around the outer periphery of the excitation coil 2. Cover. The materials of the protection plate 6 and the retaining plate 7 in this embodiment are selected with the same consideration as in the embodiment shown in FIG.
The effect obtained by this embodiment is the same as that of the embodiment of FIG.

As detailed above, according to the present invention, the mechanical strength is improved by constructing the holding plate 7, which occupies most of the area of the bottom plate 5, from a non-magnetic material having a predetermined mechanical strength. 6 occupies a small area on the bottom plate 5 and is surrounded by a retaining plate 7 having sufficient mechanical strength, so the mechanical strength of the bottom plate 5 is greater than that of the conventional bottom plate 5 shown in FIG. The mechanical strength and efficiency of the probe can be improved.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of a conventional probe, Fig. 2 is a bottom view of the probe, Fig. 3 is a side sectional view of an embodiment of the present invention, and Fig. 4 is a bottom view of the embodiment. , FIG. 5 is a side sectional view of another embodiment of the present invention, and FIG. 6 is a bottom view of the embodiment. 1... Test material, 2... Excitation coil, 3... Iron core, 4...
Transmitting/receiving coil, 6...protective plate, 7...retaining plate.

Claims (1)

[Claims] 1. An excitation coil for generating a DC magnetic field in a legged iron core is wound around an outer iron type or an inner iron type, and a transmitting/receiving coil is installed on the leg head of the iron core for generating an eddy current in the test material. In an electromagnetic ultrasonic probe, a non-magnetic material having a predetermined mechanical strength;
a bottom plate made of a non-conductive magnetic material, the non-conductive magnetic material covers the surface of the transmitting/receiving coil facing the test material, and the presence of the non-magnetic material causes the excitation coil to An electromagnetic ultrasonic probe configured so that the magnetic circuit does not become a closed loop due to the bottom plate.