JP3283415B2 - Defect determination method for brazed part - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining a defect in a brazing portion at a boundary between a pair of members having a constant thickness, and more particularly, to a method of fitting an annular body to a cast iron pipe by fitting an annular body to the boundary. The present invention relates to a method for judging a defect in a brazed portion when brazing is performed by the method described above.

[0002]

2. Description of the Related Art When a projection is formed on the outer periphery of an insertion port of a cast iron pipe, an annular body is press-fitted into the outer circumference of the insertion port, and then heated and brazed to form an opening of the pipe. And an annular body are integrated. In this case, after brazing, it is preferable to inspect the entire periphery of the brazed portion to determine a defect.

[0003] Generally, in order to determine the defect of the brazing portion between the opening and the annular body, an ultrasonic wave is emitted from the surface of the annular body toward the brazing section, and then the reflected echo is reflected. Is larger than a certain value, it is determined that the defect exists. As the constant value, a half value of the surface echo, a half value of the bottom surface echo, or the like is adopted.

[0004]

However, there is a problem in that it is difficult to satisfactorily determine a defect simply by comparing the reflected echo with a half value of the surface echo. This is because the angle of incidence of ultrasonic waves is not stable because the cast iron tube has a bend, the inner surface of the cast iron tube is a rough surface with irregularities, and the outer surface of the annular body is a shot blasted rough surface. This is because ultrasonic waves are scattered and it is difficult to uniformly enter the inside of the member.

SUMMARY OF THE INVENTION It is an object of the present invention to solve such a problem and to make it possible to reliably determine the defect even when an annular body is brazed to the outer periphery of a cast iron pipe.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for determining the presence or absence of a defect in a brazing portion at a boundary between a pair of members having a certain thickness. After emitting ultrasonic waves from the surface toward the brazing portion and detecting the reflected echo, the first gate is opened for a first predetermined time after a certain time has elapsed from the generation of the surface echo, and thereafter, The second gate is opened for a second predetermined time, and the peak value of the reflected echo when the first gate is open is larger than the peak value of the reflected echo when the second gate is open; And the first
When the peak value of the reflected echo when the gate is open is larger than a certain threshold value, it is determined that a defect exists.

In this way, it is possible to reliably pick up the echo from the defective portion as compared with the case where the magnitude of the reflected echo is simply compared with a certain fixed value, and the defect with higher accuracy can be obtained. Discrimination becomes possible.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 2, a metal ring 3 having a predetermined thickness and a rectangular cross section is provided on the outer periphery of an insertion opening 2 at one end of a cast iron pipe 1 having a certain thickness. Are inserted, and the insertion opening 2 and the annular body 3 are brazed to each other at a portion of a boundary surface thereof. 4 is the brazing part. However,
In FIG. 2, the brazing condition is poor, and defects such as gaps have occurred. Therefore, when the ultrasonic wave 5 is incident from the surface of the annular body 3 using the ultrasonic probe, the ultrasonic wave 5 is reflected by the brazing portion 4 and a defect echo 6 is generated.

FIG. 1 illustrates a reflected echo from the portion shown in FIG. The horizontal axis indicates the received voltage of the probe, that is, the magnitude of the reflected echo, and the vertical axis indicates the propagation time of the ultrasonic wave. This propagation time also means the propagation distance. Reference numeral 11 denotes a surface echo, which corresponds to a reflected wave from the surface of the annular body 3, and does not include information on the presence or absence of a defect in the brazing portion 4. Reference numeral 12 denotes a primary wave of the defect echo 6, which is received by the probe after the incident ultrasonic wave 5 is reflected by the brazing portion 4. Numeral 13 is a secondary wave of the defect echo 6, and the ultrasonic wave reflected by the brazing portion 4 is reflected again by the surface of the annular body 3 and again reflected by the brazing portion 4 and received by the probe. It is a thing. Similarly,
Reference numeral 14 denotes the third wave of the defect echo 6.

In measuring these echoes, the first gate is opened for a first predetermined time t1 after a lapse of a predetermined time after the generation of the surface echo 11, as shown in FIG. The peak value P1 is obtained. After the first predetermined time t1 has elapsed, the second gate is opened for the second predetermined time t2, and the peak value P2 of the reflected echo at that time is obtained. The peak value P1 when the first gate is open is the peak value P2 when the second gate is open.
If the peak value P1 is larger than the threshold value S1 and the peak value P1 when the first gate is open is larger than a certain threshold value S, it is determined that the brazing portion 4 has a defect. That is, P
When 1> P2 and P1> S, it is determined that a defect exists.

The first gate is opened at a time when the secondary wave 13 is expected to return to the probe, based on the thickness of the annular body 3 and the speed of sound inside the annular body 3. The second gate is also opened at a time when the tertiary wave 14 is expected to return to the probe. Here, the gate is not opened at the time corresponding to the primary wave 12, but this is because the time width of the surface echo 11 is actually wide, so that the primary wave 12 may be adversely affected by the surface echo 11. Because it is expensive. The threshold value S is set based on experience.

By adjusting the time at which the second gate is opened, it is possible to confirm that the brazing portion 4 is sound. That is, FIG. 4 shows a case where the brazing portion 4 is sound. In this case, the ultrasonic wave 5 incident from the ultrasonic probe is not substantially reflected by the brazing portion 4 and the 1
Is mainly reflected by the inner surface 7 of the lens. 8 is the bottom echo.

In this case, as shown in FIG. 3, the bottom echo 8 which is generated at a time after the generation of the surface echo 11 is generated.
Is received by the probe. When the bottom echo 8 is observed when the second gate is open for a predetermined time t2, and when substantially no reflected echo is observed when the first gate is open for a predetermined time t1, Can confirm that the brazing part 4 is sound.

[0014]

As described above, according to the present invention, the first gate is opened for a first predetermined time after a predetermined time has elapsed from the generation of the surface echo, and thereafter, the second gate is opened for a second predetermined time. When the gate is opened, the peak value of the reflected echo when the first gate is open is larger than the peak value of the reflected echo when the second gate is open, and the first gate is open When the peak value of the reflected echo is larger than a certain threshold value, it is determined that a defect exists, so the echo from the defective part is compared with a case where the magnitude of the reflected echo is simply compared with a certain value. Can be reliably picked up, and more accurate defect determination can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a method of determining a defect in a portion where an annular body is brazed to the outer periphery of an insertion opening of a pipe according to the present invention.

FIG. 2 is a diagram showing a state of propagation of ultrasonic waves when a portion where an annular body is brazed to the outer periphery of a tube opening has a defect.

FIG. 3 is a diagram illustrating an example of an observation result of a reflection echo when a portion where an annular body is brazed to the outer periphery of an insertion opening of a pipe is sound according to the present invention.

FIG. 4 is a view showing a state of propagation of ultrasonic waves when a portion where an annular body is brazed to the outer periphery of a tube opening is sound.

[Explanation of symbols]

 11 Surface echo 13 Secondary wave 14 Tertiary wave P1 Peak value P2 Peak value S Threshold

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Seiji Fujiwara 2-26 Ohama-cho, Amagasaki City, Hyogo Prefecture Inside Kubota Mukogawa Works, Ltd. (56) References JP-A-58-68664 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) G01N 29/00-29/28

Claims (1)

(57) [Claims] 1. A method for judging the presence or absence of a defect in a brazing portion at a boundary between a pair of members having a certain thickness, wherein ultrasonic waves are directed from the surface of one member toward the brazing portion. After launching, you can detect the reflected echo,
After a predetermined time has elapsed from the occurrence of the surface echo, the first gate is opened for a first predetermined time, and then the second gate is opened.
The second gate is opened for a predetermined time, and the peak value of the reflected echo when the first gate is open is larger than the peak value of the reflected echo when the second gate is open, and the first gate is opened. A method for determining the presence of a defect when the peak value of the reflected echo when the gate is open is greater than a certain threshold value.