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JPS5621058

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DESCRIPTION JPS5621058
Specification 10 Title of Invention
Transducers for electromagnetic ultrasonic testing
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transducer for
electromagnetic ultrasonic flaw detection useful for flaw detection of a steel material, particularly
a hot material in a continuous casting process or the like. Conventionally, as a transducer for
electromagnetic ultrasonic flaw detection, the magnetic flux is squeezed using a 1-ring type
electromagnet or permanent magnet, a coil is placed at the tip of the magnet, and an eddy
current is generated on the surface of the object to be inspected. It is known that ultrasonic
energy is introduced into the test material by the Lorentz force due to the interaction of The
basic configuration is as shown in FIG. As shown in the figure, now, when an electric current in a
certain direction is applied to the coil 2, an eddy current generator is generated on the surface of
the test object 1, and this is interacted with the magnet 1 (a magnetic field H Table diIsIn
Lorentzka F of the test material 3 works. Therefore, by passing an alternating current through
the coil 1, in the case of FIG. 111, the ultrasonic wave of the longitudinal wave whose vibration
direction and the propagation direction coincide with each other is injected into the test material
8. The ultrasonic wave input to the material to be inspected 1 is reflected back by the defect
when there is a defect in the material to be inspected EndPage: 1. Therefore, flaw detection is
performed by detecting the returned ultrasonic waves with the detection coil in a conversion
process reverse to that in the case of injection. In this case, the detection coil may use the
excitation coil 2 shown in FIG. 1 as it is or may be prepared separately. In order to increase the
energy input by the transducer for electromagnetic ultrasonic waves, 1 generated magnetic field
It is necessary to make However, for that purpose, in the configuration of FIG. 1, the yoke
becomes extremely large, and from a practical standpoint it can not but be limited to a certain
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size. Therefore, to solve such a problem that the input energy is limited and to obtain high
sensitivity, localizing the magnetic field in the vicinity of the surface of the test material to reduce
the overall magnetostatic energy Recently, a new electromagnetic ultrasonic transducer has been
proposed that generates a large bias magnetic field with a small magnet. The basic configuration
is that a plurality of permanent magnet plates magnetized in the thickness direction are arranged
with the high permeability magnetic material and arranged in the thickness direction so that the
polarity is alternately reversed. And a wave-shaped coil disposed so as to meander along the
arrangement of the permanent magnet plates near the end of the magnetic field generating
mechanism. By the way, in the case of performing the nakedness and the scratching of the hot
material in the continuous casting process and the like with such an electromagnetic ultrasonic
transducer, some consideration is required unlike the case of the cold case.
It is particularly important that the gap distance between the transducer and the material to be
inspected must be sufficiently large, and it should be about 5 tm if @f, the reason is that the
surface roughness is severe in the case of a hot material, As a cooling structure of the transducer,
the cooling medium has to be flowed in the air gap between the end face of the transducer and
the test material, and so on. And while maintaining such a gap distance, 15wx15uNI which
becomes a problem in the hot material by injecting large ultrasonic energy! It is required to
detect defects of II ′ ′ or more with high sensitivity. The present invention has been made in
view of the above-described point, and uses a combination of a magnetic field generating IIIIl and
a wave-shaped coil which can form a uniform and strong magnetic field over a wide area of the
surface of a test material. It is intended to provide a transducer for electromagnetic ultrasonic
waves capable of effectively detecting a defect in an intermediate material. The transducer for
electromagnetic ultrasonic testing according to the present invention is formed by arranging a
plurality of permanent magnet plates magnetized in the thickness direction with the high
permeability magnetic material and alternately arranging them in the thickness direction so as to
be opposite in polarity. A magnetic field generating mechanism is provided, and a wave-shaped
coil meandering along the arrangement of the permanent magnet plates is disposed in the
vicinity of the end of the magnetic field generating mechanism, and the effective area of the
magnetic field generating mechanism is 3.5. It is characterized in that it is set to ˜ 8.5 inches
square. In this case, as described in detail below, by selecting the arrangement relationship
between the wave-shaped coil and the permanent magnet plate, the material to be inspected will
be: longitudinal or transverse ultrasonic waves to be excited or surface waves You can choose to
Two longitudinal and dual surface acoustic wave transfer jitches according to two embodiments
of the present invention will be described with reference to FIGS. As is apparent from these
figures, a plurality of permanent magnet plates JJ (ZJ1. 11,. ) Is arranged in the thickness
direction so that the polarities are alternately reversed by the high magnetic permeability
magnetic material 12 (Jxl, Jj, zJM ...), and a magnetic field generating mechanism is configured. .
In this example, as shown in FIG. 3, the wave-shaped coil 13 for generating the eddy current is
disposed in a serpentine manner so as to cover only immediately below the end face of the
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permanent magnet plate II. 14 is a to-be-tested material. The effective area of the magnetic field
generating mechanism is 2.5 to 8.5 inches square. FIG. 4 is a schematic vertical cross-sectional
view, and to explain how ultrasonic charging energy is injected into the test material 14 using
this, it is now shown in FIG. When a current in a direction is applied, an eddy current I of the
illustrated polarity is generated at each portion below the permanent magnet plate 111U on the
surface of the inspection material 14.
Due to the interaction between the eddy current 1 and the magnetic field H in the horizontal
direction directly below the permanent magnet plate 11, a Lorentz force F of the illustrated
polarity acts on the surface of the test material 14. Therefore, by passing an alternating current
through the corrugated EndPage: 2 coil 13, an ultrasonic wave of a longitudinal wave in which
the pregnancy direction and the propagation direction are both perpendicular directions is
excited in the test material 14. In this case, although the main ultrasonic wave is a longitudinal
wave, one surface wave is also simultaneously excited because there is a slight interaction
between the vertical component of the magnetic field generated on the surface of the inspection
material 14 and the eddy current. . In this way, the ultrasonic wave is excited in the inspection
material 14 and the reflected wave from the defect portion of the ultrasonic wave is detected by,
for example, the wave-shaped coil JJ following the conversion process reverse to the ultrasonic
wave excitation described above. It is a matter of course that flaw detection is performed at the
same time as the corrugated coil 1B, and a detection coil paired with this may be disposed.
According to this embodiment, due to the configuration of the magnetic field generation
mechanism, a uniform and strong magnetic field can be obtained, and interaction with this and
the eddy current induced by the corrugated coil enables uniform and wide flaw detection surface.
You can get it. Further, with the expansion of the effective area of the transducer, it is possible to
detect the defect with high sensitivity by setting the threshold distance between the transducer
and the sound material to be sufficiently large compared to the conventional sheet. According to
the experiment, when the effective area of the transducer is designed to be 1.0 inch square, the
relationship between the air gap distance and the output voltage is as shown in FIG. 5 and
according to the following experiment, the effective area is 1.5 inch. When designed to have a
square to SL5 inch square, it was possible to detect a defect with a size of 158 m × 15 gj with
sufficiently high sensitivity, assuming that the gap distance of dark between the transducer and
the test material is 5-. If the effective area is too large, small defects can not be detected, and if
the effective area is small, the gap distance between the transducer and the inspection material
can not be set large, and the transducer is used as a cooling structure. It is not possible to
effectively detect defects in hot materials. If the above relationship is illustrated, it becomes as
shown in FIG. 6, and it is understood that it is preferable for flaw detection of a hot material to
make the effective area be tS to L5 inch square. 7 to 9 show the configuration of the main part of
still another embodiment of the present invention. In these embodiments, corrugated coils 11.2.
A double-sided transducer is configured by arranging II '. That is, the embodiment of FIG. 7 is a
double-sided transducer whose lower surface is for longitudinal waves and whose upper surface
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is for transverse waves. In the embodiment of FIG. 8, the thickness of the permanent magnet
plate 11 in FIG. 7 is doubled, and it is found from the experiment that the longitudinal wave is
strengthened about twice.
On the other hand, it is known that in FIG. 9 that the thickness of the high permeability magnetic
plate 12 in FIG. As described above with reference to the embodiment, according to the
transducer for electromagnetic ultrasonic flaw detection according to the present invention, the
combination of the magnetic field generating mechanism for giving a uniform and strong
magnetic field to the test material and the corrugated coil By setting the effective area to 2.5 to 8
or 5 inches square, uniform and wide flaw detection surface can be obtained, and the effective
area is enlarged! From the above, it is possible to detect the defect with high sensitivity
sufficiently even for the hot material by setting the distance of the dark to the inspection material
large.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a typical example of a
conventional electromagnetic ultrasonic transducer, and FIG. 2 is a perspective view showing an
electromagnetic ultrasonic transducer according to an embodiment of the present invention, jl! 3
shows the arrangement pattern of the corrugated coil, FIG. 4 is a schematic vertical sectional
view for explaining the operation in the same manner, and FIG. 5 is a diagram showing the
relationship between the air gap distance and the output voltage. FIG. 6 similarly shows the
relationship between the effective area and the detection ability, and the figures from $ 7 to FIG.
9 are the main components of the embodiment of the double-sided transducer. zxczx, 17. , JJ, ...)
... permanent magnet plate, xxc 421, xB, xx 3 ...) ... high permeability magnetic material, JJ, 1 j '...
wave-shaped coil, 14 ... inspection Material Applicants Attorney Attorney Takehiko Suzue
EndPage: 3 years 1 figure 2 figure 3 3 EndPage: 4 o 6 Figure 翁 little boy (inches x 3 n di) off
figure EndPage: 5
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