JPS6370161A - Immersion type ultrasonic flaw detection - Google Patents

Abstract

PURPOSE:To secure a relation S/N>=4 in an immersion type ultrasonic flaw detection, by using an ultrasonic wave with the frequency of 2-2.25MHz. CONSTITUTION:An ultrasonic wave with the frequency of 2-2.25MHz is transmitted at about 48 deg. of the flaw detection angle of refraction to the surface of an object 3 to be inspected which is conveyed while being immersed from a reciprocating probe 2. Then, reflected waves from a defect inside the object 3 being inspected are received with the probe 2 to detect the position of the defect. The ultrasonic wave with the frequency of 2-2.25MHz enables the securing of a relation S/N>=4 because the attenuation thereof underwater is very limited. This enables the detection of the position of any small defect below 2mm in the size.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Field of Industrial Application This invention relates to an immersion-type ultrasonic flaw detection method for continuously and automatically detecting flaws in plate-shaped materials to be inspected, such as steel strips.

(2) Conventional immersion-type ultrasonic flaw detection methods include the oblique angle method, plate wave method, double transmission method, and vertical method, but the dead zone in the thickness direction of the material to be inspected can be set to O. For these reasons, the oblique angle method is widely adopted. In this bevel method, generally 5-
Using ultrasonic waves with a frequency of 112 or more, the ultrasonic waves are emitted from a probe toward the surface of a material to be inspected that is being transported under water at a flaw detection refraction angle of about 48 degrees.

Then, this emitted wave propagates inside the material to be inspected, and if there is a defect (flaw) on the way, it collides with it and generates a reflected wave, so this reflected wave is received by the transmitting side. As a result, the position of the defect is detected.Also, along with this detection, the position of the defect is marked by an automatic marker device.

(3) Problems to be solved by the invention By the way, the ultrasonic waves used in the conventional flaw detection method have a frequency of 5 M)Iz or higher, so when they enter water, they are attenuated greatly, causing a reaction. The ratio S/N between the wave resistance S and the noise N of the entire device is 4 (
dB 12) or less, and although it may be fine for defects of 2 mm or more, there was a pressure point where it was difficult to detect the position of defects smaller than this.

Therefore, the technical object of the present invention is to ensure an SZN ratio of S/N≧4 so that the position of even a small defect as described above can be detected.

(4) Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a means for solving the above-mentioned problems. An ultrasonic wave is emitted from a probe installed so that it can be reciprocated in the direction of the inspection. If a defect exists inside the material to be inspected, the emitted wave collides with the defect and is reflected, and this reflected wave is used as the probe for the detection. By receiving with a touch,
In the immersion ultrasonic flaw detection method for detecting the location of defects,
The frequency of the ultrasound is 2~2.25M)! This method is characterized by using ultrasonic waves of z.

(5) Example In Fig. 1, 1 is a flaw detection water tank in which a probe 2 is installed;
Passage holes 4 for the test material 3 are bored in the front and rear walls of the flaw detection water tank 1 in the direction of transport of the test material 3 (indicated by arrow A in the figure). Auxiliary water tanks 5 and 6 are installed adjacent to the front and rear walls of the flaw detection water tank 1, and one side wall of the auxiliary water tanks 5 and 6 is connected to the flaw detection water tank 1.
It is common to the front and rear walls of , and communicates with the flaw detection water tank 1 via the passage hole 4 .

The passage hole 4 is provided with a seal gasket (not shown) that seals between the passage hole 4 and the inspected material 3 conveyed therethrough.

The auxiliary water tanks 5 and 6 are connected to a water storage tank 7 installed below them via pipes 8 and 9.

10 is a drain pipe. On the other hand, the water tank 7 is connected to a water tank 12 installed above the flaw detection water tank 1 via a pipe 14 equipped with a pump 13.
It is connected to the flaw detection water tank 1 via 6. , 18 are jet tubes that flow water from the water supply tank 12 toward the probe 2 in the flaw detection water tank 1 to prevent air bubbles from entering the probe 2 during flaw detection.

Due to the piping structure as described above, the water in the flaw detection tank 1 flows out from the passage hole 4 into the auxiliary water tanks 5 and 6, and from the auxiliary water tanks 5 and 6 flows down to the water storage tank 7 via the pipes 8 and 9, where it is once suspended. reactor. after that.

The water is sent from the water tank 7 to the water tank 12 via the pipe 14 by the operation of the pump 13, and from the water tank 12 to the flaw detection water tank 1 via the pipe 16 (18). Such circulating supply is performed by controlling the operation of the pump 13, whereby the water in the flaw detection water tank 1 is always maintained at a predetermined water level.

As shown in FIG. 2, a plurality of probes 2 are arranged in series along the conveyance direction of the material 3 to be inspected.

It is composed of one probe block.

The cable 22 of each probe 2 is connected to the flaw detector 24 via a relay box (not shown). Furthermore, it is connected to a recorder 25 from here. Then, as described above, the probe 2 is moved as a single block body by the scan mechanism section 26 in a direction (indicated by arrow B) that intersects the conveyance direction of the inspected material 3, as shown in FIG. The inspection material 3 is reciprocated while being reversed at the edge portion. In FIG. 2, arrow C indicates the direction of ultrasonic wave transmission. The probe 2 emits ultrasonic waves with a frequency of 2 to 2.25 MIIz.

In addition, in Fig. 1, 27 and 28 are the feed rolls for the material to be inspected 3,
It has a function of suppressing vertical movement of the inspected material 3 being conveyed in water in the flaw detection water tank 1.

Among these, the upper roll is fixed, and the lower roll can be moved upwardly and downwardly toward and away from the upper roll. Reference numeral 29 denotes a photosensor installed outside the probe tank 1, and is designed to eliminate reflected waves entering from the edges of the material 3 to be inspected.

In the above-mentioned apparatus, an ultrasonic wave having a frequency of 2 to 2.25 MHz is emitted from the reciprocating probe 2 toward the surface of the inspected material 3 that is being conveyed under water at a flaw detection refraction angle of about 48 degrees.

If a defect exists inside the inspected material 3, a reflected wave is generated from this defect, and by receiving this reflected wave with the probe 2, the position of the defect is detected.6 Figure 4.5 shows Two large and small defects A and B (A:
1 am in the defect, B: defect width 2 mm) is 2-25 M with different frequencies from probe 2 under the following conditions.
! This is experimental data showing whether detection is possible by transmitting three ultrasonic waves of Iz t 5 M) lz tlo MHz.

Note: Material to be inspected: Thickness: 1.8 to 5. Omm width:
200~400w0 Conveying speed of inspected material...4~6
Distance between m/winQ probe and inspected material...30 degrees
Probe right movement beam width...3+++m○ Probe back and forth! FII (scan) width: 600 mm 0 Probe reciprocating speed: 945 mm/see As can be seen from the experimental data in Figures 4 and 5, A and B at 2.25 MHz
Both can be detected. On the other hand, at 5 MHz, the larger one B can be detected, but the smaller one A is difficult to detect, and at 10 MHz both A and B are difficult to detect. Although not listed here as experimental data,
Detection results similar to those obtained at 2.25 Ml1z were obtained at 2 MHz.

In addition, in the case of 2.25MHz (same as 2Mllz), A.

It can be seen that in both methods B, S/N≧4 is ensured, and the attenuation through water is extremely small.

(6) Effects of the invention As described above, this invention uses ultrasonic waves with a frequency of 2 to 2.25 MIIz as ultrasonic waves used for flaw detection.
It is now possible to ensure a S/N≧4 /N ratio, and therefore even small defects of 2m+n or less, which were detected on the inner wall in the case of the conventional 5Ml (z or less) frequency, can be detected at that location. It has excellent effects such as enabling detection.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an immersion type ultrasonic flaw detection device showing an embodiment of the present invention, FIGS. The figure is a graph showing experimental data regarding defects in the same inspected material as above.

Claims (1)

[Claims] 1. Send ultrasonic waves to the surface of the material to be inspected that is being transported by a transport member in the flaw detection water tank from a probe that is installed above the surface so that it can reciprocate in a direction that intersects the direction of transport of the material to be tested;
When a defect exists inside the material to be inspected, the transmitted wave collides with the defect and is reflected, and the reflected wave is received by the probe to detect the position of the defect.Immersion type ultrasonic flaw detection In the method, the ultrasonic wave has a frequency of 2 to 2
．． An immersion type ultrasonic flaw detection method characterized by using 25 MHz ultrasonic waves.