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DESCRIPTION JPS63255657

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DESCRIPTION JPS63255657
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
method of manufacturing a damper material for a probe of an ultrasonic flaw detector, and more
particularly, to a method of manufacturing a damper material used for a probe having high
resolution. 2. Description of the Related Art A damper is used to obtain a high resolution probe.
FIGS. 4A and 4 are explanatory views of a probe when a damper is used, and the probe is
composed of a transducer a1 electrode b1 damper C. A damper C is provided on the back surface
of the vibrator a, and by the action of the damper C, a pulse waveform d with a small frequency
as shown in FIG. When the damper is not used, as shown in FIGS. 3 (A) and 3 (B), the vibration
wave from the probe becomes a free vibration waveform e with many wave numbers, and high
resolution can not be obtained. In order to obtain a probe having such high resolution, it is
essential to use the damper 0 in the probe. And, as a property of the damper material itself used
for the damper, a material having a high value of acoustic impedance (the product of density and
sound velocity) and as close as possible to the value of acoustic impedance of the vibrator and
having a large sound attenuation Is preferred. From the above background, in order to obtain a
probe with higher resolution, a conventional damper material is manufactured by mixing
tungsten powder having a high acoustic impedance value into epoxy resin and pressing it with a
press etc. There is [Problems to be Solved by the Invention] However, since the damper material
manufactured by the above method J: is made by adhering and bonding between particles of
tungsten powder with an epoxy resin, it has a high density. It was difficult to obtain, and the
acoustic impedance of the damper material could not be increased. By the way, at the time of
pressing, a large friction occurs between tungsten powder, resulting in the infiltration of many
resins inside, and the density of the resin is as low as 1.2 × 10 3 kg / m 3 and the specific
gravity of the damper material is also about 8 at the limit The acoustic impedance was also able
to be produced only as low as about 15 × 10 6 kg / ll 12 S. From the above, it was not possible
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to obtain a probe with higher resolution, and it was not possible to respond to the measurement
of thin film, etc. for which high accuracy is required. Also, the vibrator to be applied is
inconvenient such as being limited to lead niobate (acoustic impedance: 16 × 10 6 kp / m 2 S)
or the like having a relatively small acoustic impedance. SUMMARY OF THE INVENTION The
present invention has been made in view of the above problems, and its object is to provide a
high-resolution probe having a high acoustic impedance and a large sound attenuation. It is in
providing the manufacturing method of materials.
[Means for Solving the Problems] In the method of the present invention, a high melting point
metal powder mainly composed of tungsten or uranium and a low melting point metal powder
mainly composed of a metal having a melting point of 1000 ° C. or less are mixed. The gist of
the present invention is to have a mixing step, a heating step of heating to a temperature at
which only the low melting point metal powder is melted, and a consolidation step. [Operation]
Figs. 2 (A) to 2 (C) are schematic diagrams showing the process of consolidation and
solidification of the mixed powder of the present invention, using powders of tungsten (high
melting point metal) and lead (low melting point metal). That's the case. The operation will not be
described based on the following figures. The mixed powder 3 in which the high melting point
metal powder 1 and the low melting point metal powder 2 are mixed is in a state in which a
cavity is considerably left as shown in FIG. 2 (A). Next, by heating the mixed powder 3 to the
melting point of the powder 2, only the powder 2 is melted as shown in FIG. 2 (B), and the place
occupied by the powder 2 by the discharged powder 2 is hollowed, The melted powder 2 results
in flowing into the narrow space between the powders 1 by capillary action. The powder 2 which
has flowed between the powder 1 acts as if it is a lubricating oil when compressed as shown by
the arrows by an external force from a press etc., and the powder 1 and the other cause slip
easily. As shown in Fig. (C), it is consolidated at a high density, and the air-cooled I is cooled and
solidified by water cooling or the like to obtain a material, that is, a damper material. In
particular, since the damper material manufactured by mixing tungsten and lead powder is a
mixture of metals whose acoustic impedances are largely different from each other, sound
attenuation is also large and an excellent damper material can be obtained. Incidentally, the
acoustic impedance is 10 4 × 10 6 kg / Tl 12 s for tungsten and 25 x 10 6 kq / + n 2 s for lead.
[Embodiment] A preferred embodiment of the present invention will be described based on the
drawings. FIG. 1 is a flow chart of one embodiment showing the method of the present invention.
In FIG. 1, the case where tungsten powder is used as the high melting point metal powder and
lead powder is used as the low melting point metal powder will be described as an example. 10
to 40% of lead powder is mixed with tungsten powder in volume ratio, and mixed so as to be
uniformly distributed to make a mixed powder. For consolidation, the mixed powder is loaded at
a load of 5,000 using a consolidation device consisting of a die and a punch! It was compacted at
If / cm2. Next, the mixed powder was filled in a die and the load was released, and the mixed
powder was placed in a heating furnace under an argon atmosphere, and heated for about 30
minutes at a humidity of 600 ° C. in the furnace to melt only the lead in the powder.
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6 First, take the die out of the furnace and insert the punch into the die again while cooling
naturally and press solidify it with a load of 15,000 kgr / cm2, cool it to room temperature,
solidify it and make the damper material of tungsten and lead powder Manufactured. When the
property of this damper material was measured, it was the density −-12 × 103 k (] / TI3 and
the sound velocity υ-2100 m / s. Therefore, the acoustic impedance I is:--× x)) = 12 x 103 x
2100 = 25.2 x 106 kg / rr? The value of s,-) and acoustic impedance was 25.2 x 10 6 kg / Tl 12
S, and it was confirmed that the value of acoustic impedance was very high compared to the
conventional one. When this damper material is combined with a vibrator, it can be used, for
example, as a lead zirconate-based vibrator (acoustic impedance 28 × 106 kQ / vS ′), and a
high resolution probe can be obtained. In the above embodiment, although the case where
tungsten powder is used as the high melting point metal powder has been described, the present
invention is not limited to this, and high specific gravity and high melting point uranium similar
to tungsten may be used. It may be a metal powder consisting mainly of tungsten or uranium or
a metal alloy thereof. The low melting point metal powder is not limited to lead, and may be
aluminum, as long as it is a metal having a melting point lower than that of tungsten or uranium
and practically having a melting point of 1 ooo ° C. or less. . However, in consideration of sound
attenuation, preferably, a metal having an acoustic impedance largely different from that of the
refractory metal is preferable. Although the case where the mixed powder is compacted and then
heated is described, the compacting step may be omitted and the mixed powder may be heated
immediately. Although the mixed powder was heated to a temperature at which the low melting
point metal powder melts, and then the mixed powder was compacted while being naturally
cooled, the mixed powder was compacted in the heated or cooled state. May be The cooling may
be forced cooling by water cooling or the like instead of natural cooling. It goes without saying
that other modifications can be made without departing from the scope of the present invention.
As described above, according to the method of the present invention, the following excellent
effects can be obtained. (1) Since the mixed powder of high melting point and low melting point
metal powder is heated to a temperature for melting only the low melting point metal, the
density of the powder can be further increased. (2) Since the low melting point metal of the
mixed powder is melted and then consolidated, the density of the powder can be further
increased.
(3) From the above items (1) and (2), a damper material having a high acoustic impedance value
as compared to the prior art can be obtained, and a high resolution probe can be obtained.
[0002]
Brief description of the drawings
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[0003]
FIG. 1 is a flow chart of one embodiment showing the method of the present invention, FIG. 2
(A>, (B), (C) is a schematic view showing the consolidation and solidification process of the mixed
powder of the present invention, FIG. 4 and FIG. 4 are explanatory views of a conventional probe.
In the figure, 1 indicates a high melting point metal powder, 2 indicates a low melting point
metal powder, and 3 indicates a mixed powder. Patent Assignee Ishikawajima Harima Heavy
Industries Ltd. 1N Open HG 3-255G ', +7 (4) (A) (A) (B) (C) Figure 2 Figure 4
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