JP3614115B2 - Water immersion type ultrasonic inspection method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a water immersion type ultrasonic flaw detection method in which a metal band such as a steel band is conveyed in a water tank and internal defects of the metal band are continuously detected by ultrasonic waves.
[0002]
[Prior art]
An ultrasonic flaw detection method is often used to detect an internal defect of a metal strip, for example, a steel strip (hereinafter, a steel strip will be described as a typical example). Especially for ultrasonic flaw detection with the aim of detecting internal defects such as inclusions in the entire width of the steel strip, a number of ultrasonic probes (detectors) are arranged in the width direction of the steel strip to be detected, and the steel strip is There are a method of inspecting while transporting, a method of arranging a large number of ultrasonic probes in the width direction of the steel strip, and a method of scanning ultrasonic waves substantially perpendicular to the transport direction of the steel strip.
[0003]
When detecting an internal defect of a steel strip by such a flaw detection method using ultrasonic waves, in order to maintain a good acoustic coupling between the ultrasonic probe and the steel strip, that is, to increase detection accuracy, for example, It is advantageous to detect by immersing a steel strip in the water tank.
[0004]
[Problems to be solved by the invention]
However, since many bubbles are mixed in the water in which the steel strip is immersed, there is a problem that these bubbles diffuse the ultrasonic waves between the ultrasonic probe and the steel strip and prevent the steel strip from being flawed. It was.
In other words, industrial water originally contains some air bubbles, but when the steel strip is mainly introduced into the aquarium, air similar to the steel strip is mixed into the water as air bubbles near the water surface. As a result of being carried on the water stream to the place where the ultrasonic probe is installed, the detection is hindered.
[0005]
In addition, when the steel strip is led out from the water tank, there are also bubbles that are generated when the water attached to the steel strip falls into the water tank, and these bubbles are also diffused by the water flow in the water tank, causing the ultrasonic flaw to be hindered. . Regarding this bubble, for example, as disclosed in JP 2000-230975 A, it has been proposed to install a liquid receiver under a steel strip led out of a water tank to avoid water falling into the water tank. .
[0006]
However, it is difficult to completely prevent the generation of bubbles mixed into the water due to various causes such as bubbles generated when the steel strip is introduced into the water tank. It was a big problem in ultrasonic flaw detection.
Therefore, the present invention intends to propose a method for avoiding bubbles in water from obstructing ultrasonic flaw detection on the premise that bubbles are mixed in water.
[0007]
[Means for Solving the Problems]
As a result of earnestly examining the means for eliminating the influence of bubbles in water by limiting the detection location to the ultrasonic flaw detection in mind, it is difficult to completely prevent the bubbles from being mixed into the water. The present invention has been led.
That is, the present invention passes a metal band between an ultrasonic transmitter and an ultrasonic receiver arranged to face each other in a water tank, and transmits an ultrasonic beam between the ultrasonic transmitter and the ultrasonic receiver via the metal band. The water immersion is characterized by sucking the water flow that is the same as the band on the upstream side of the ultrasonic transmitter and the ultrasonic receiver in the water tank when transmitting and receiving and detecting the internal defect of the metal band. Type ultrasonic flaw detection method.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Next, the method of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing an ultrasonic flaw detection facility used in the method of the present invention, and a steel strip 1 is conveyed from the left side (upstream side) to the right side (downstream side). 1 introduces the steel strip 1 into the water tank 4 by the deflector rolls 2 and 3, and then transports the steel strip 1 along the bottom surface of the water tank 4 between the sink rolls 5 and 6, and then the deflector roll 7 And 8, the internal defect of the steel strip 1 is detected by the ultrasonic probe 9 disposed in the water tank 4 in the process of deriving from the water tank 4.
[0009]
That is, the ultrasonic transmitter 9 a and the ultrasonic receiver of the ultrasonic probe 9 facing each other across the conveyance line in a direction orthogonal to the conveyance line of the steel strip 1 set between the sink rolls 5 and 6 in the water tank 4. 9b is disposed, and by transmitting and receiving an ultrasonic beam via the steel strip 1 between the ultrasonic transmitter 9a and the ultrasonic receiver 9b, internal defects of the steel strip 1 passing therethrough are continuously detected. . The ultrasonic probe 9 functions if the ultrasonic transmitter 9a and the ultrasonic receiver 9b are arranged to face each other. Therefore, the arrangement of the ultrasonic transmitter 9a and the ultrasonic receiver 9b shown in FIG. Not limited to this, the positions of the two may be interchanged. In the following description, the ultrasonic transmitter 9a and the ultrasonic receiver 9b are collectively referred to as an ultrasonic probe 9 for convenience.
[0010]
What becomes a problem in the ultrasonic flaw detection described above is air bubbles contained in water in the gaps 10 a and 10 b between the steel strip 1 passing through the ultrasonic probe 9 and the ultrasonic probe 9. That is, if bubbles exist in the gaps 10a and 10b, the transmission beam in the gap 10a and the reception beam in the gap 10b are diffusely reflected by the bubbles, and as a result, accurate ultrasonic flaw detection is hindered.
[0011]
Therefore, in the present invention, as shown in FIG. 2, the water flow 12 a that the steel strip 1 is associated with through the water intake ports 11 a and 11 b provided on the upstream side of the ultrasonic probe 9 in the water tank 4 in the traveling direction of the steel strip. Aspirate 12b. That is, when the steel strip 1 is introduced into the water tank 4, air is generated near the water surface due to air mixed with the steel strip 1 being mixed into the water, and such bubbles are attached to the steel strip 1 to generate ultrasonic waves. In order to reach the probe 9, it is important to suck the accompanying flow mixed with bubbles before reaching the ultrasonic probe 9 on the upstream side of the ultrasonic probe 9. Here, it goes without saying that the water intake ports 11 a and 11 b have openings at least over the entire width of the steel strip 1.
[0012]
In this way, by sucking the water flows 12a and 12b that are the same as the steel strip 1 on the upstream side of the ultrasonic probe 9, it is possible to introduce a water flow with less bubbles into the gaps 10a and 10b. The impact on acoustic flaw detection can be reduced.
Furthermore, as shown in FIG. 1, it is also effective to install a water receiver 16 under the steel strip 1 led out from the water tank 4 to avoid water falling into the water tank 4.
[0013]
【Example】
A hot rolled steel sheet for tin plate having a width of 600 to 1200 mm and a thickness of 1.6 to 2.6 mm is introduced into the water tank 4 of the ultrasonic flaw detection equipment shown in FIG. 1 at a conveying speed of 330 m / min. Internal defects were detected by acoustic flaw detection. At that time, when water was sucked from the water intake ports 11a and 11b under the following conditions, the bubble interference area ratio in the gaps 10a and 10b was 1.5%. Here, the bubble interference area ratio represents the ratio of the “cross-sectional area of the ultrasonic beam subjected to bubble interference” to the “total cross-sectional area of the ultrasonic beam”, and is an appropriate index indicating the influence of the bubble. Become.
Water intake arrangement: 50mm from steel strip
Aspiration amount: 20 m ³ / h
As a comparison, the bubble interference area ratio was 2.5% as a result of measuring the bubble interference area ratio in the case where water was not sucked from the water intake ports 11a and 11b. The effectiveness of the present invention Was confirmed.
[0014]
【The invention's effect】
As described above, according to the present invention, even if bubbles are unavoidable in the water tank, the influence of the bubbles is reduced at least in the ultrasonic flaw detection unit. Accuracy can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an ultrasonic flaw detection equipment used in a method of the present invention.
FIG. 2 is a diagram showing a main part of an ultrasonic flaw detection equipment used in the method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steel strip 2, 3, 7, 8 Deflector roll 4 Water tank 5, 6 Sink roll 9 Ultrasonic probe 9a Ultrasonic transmitter 9b Ultrasonic receiver 10a, 10b Gap 11a, 11b Intake port 12a, 12b Water flow

Claims (1)

A metal band is passed between the ultrasonic transmitter and the ultrasonic receiver arranged opposite to each other in the water tank, and an ultrasonic beam is transmitted and received between the ultrasonic transmitter and the ultrasonic receiver via the metal band. In detecting an internal defect, a water immersion type ultrasonic flaw detection method is characterized in that a water stream with a metal band is sucked upstream of the ultrasonic transmitter and ultrasonic receiver in the water tank.

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