JPH0875707A - Ultrasonic wave surface flaw detection device and method thereof - Google Patents

Abstract

PURPOSE: To discriminate between a flaw and a foreign matter, and to detect a depth of the flaw by a method wherein a surface wave is transmitted to a work from a transmitting/ receiving flaw detection probe, the reflection wave is received by the transmitting/receiving flaw detection probe and the straight wave is received by a receiving-only probe and received levels of both of the probes are compared with each other. CONSTITUTION: A surface wave goes from a transmitting/receiving flaw detection probe 2 to a receiving-only probe 3. When there is a flaw on the way, the wave is reflected to be returned to the probe 2. When the work W does not have a flaw and a foreign matter stuck on the surface, a receiving level of the probe 3 becomes markedly high and the receiving level of the probe 2 becomes zero. When the work has a flaw but does not have a foreign matter, a component that the reflection wave is subtracted from the surface wave reaches the probe 3, then the receiving level becomes roughly the middle thereof. If there is no flaw on the work W but there is a foreign matter on it, the surface wave attenuates and the receiving level of the probe 3 becomes roughly medium. The combinations of the levels of the probes 2, 3 are operated by an operator 5 so that the flaw and foreign matter are discriminarted from each other. It is possible to estimate the depth of the flaw from reference data, a real pulse penetration coefficient and real accumulated penetration intensity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder (eg roll).
TECHNICAL FIELD The present invention relates to an ultrasonic surface flaw detection method and apparatus for detecting defects such as flaws generated on the surface of a flat plate.

[0002]

2. Description of the Related Art Eddy current flaw detection, penetration flaw detection, ultrasonic surface wave flaw detection and the like are known as methods for detecting surface flaws in metal materials. The eddy current flaw detection method is to detect eddy currents on the surface of the target material and detect changes in the resistance value to detect flaws, but it is also reliable because it detects tissue changes and magnetic changes other than flaws. It is said that the sex is poor. The penetrant flaw detection method is a method called color check, and is a method in which a penetrant liquid is applied to the surface of a target material, the surface is then washed with a cleaning liquid, and then a developer is applied. If there is a crack on the surface, the penetrant will permeate into this crack and color will be developed by the developer, which makes it easier to find flaws. However, the workability is not good because it is basically a manual work by a worker. Further, since it is a visual judgment, a minute flaw may be overlooked.

Therefore, an ultrasonic surface flaw detection method, which has a high detection accuracy and a high working efficiency, has attracted attention. A method in which this flaw detection method is applied to a roll is disclosed in Japanese Patent Laid-Open No. 52-92779, "Roll flaw detection method" or It is proposed as Japanese Patent Publication No. 5-65027, "Roll ultrasonic flaw detection method".

The above is characterized in that the local water immersion method surface wave ultrasonic probe is ultrasonically coupled to the rotating roll at a constant value of the roll speed or less. According to FIG. After the surface water is purged by the air nozzle 32 disposed on the side, ultrasonic flaw detection is performed. The above is characterized in that it is provided with a tire type surface wave probe and a wiper for removing contaminants in the grinding fluid.

[0005]

As is well known, since the ultrasonic flaw detection method has very high sensitivity, even if a small foreign matter is attached to the surface, it can be detected as a flaw, and it is necessary to wipe the surface cleanly. Therefore, the above treatment is performed by air purging, and the above treatment is performed by a wiper.

However, it has not been confirmed whether the air purge and the wiper function effectively. That is,
If the air purging or wiper cleaning function is weak, an incorrect decision will be made. Therefore, the functions of the air purge and the wiper are strengthened more than necessary, for example, the amount of air is doubled to increase the equipment cost and operating cost, or the wiper is strongly pressed against the roll surface, resulting in a flaw on the roll surface. There is also the problem of turning on. Therefore, it is necessary to have a technique for determining whether or not there is a deposit such as a water drop on the roll surface.

Further, when a flaw is found in the above, the roll is re-polished, but in the above, the depth of the flaw cannot be detected even if the presence of the flaw is detected, so the polishing amount becomes uncertain. However, if the polishing amount is insufficient, it is necessary to grind many times, so in reality, a large amount of grinding will be performed. If so, the life of the roll is shortened. Therefore, there is a demand for a technique capable of detecting not only the defect but also the depth of the defect.
Therefore, it is an object of the present invention to provide an ultrasonic surface flaw detector and a method thereof, which are provided with a technique for effectively detecting foreign matter adhering to the surface of a work and a technique for detecting the depth of a flaw.

[0008]

In order to achieve the above object, the present invention provides a transmitting / receiving probe that sends a surface wave to a work and receives a reflected wave due to the flaw if there is a flaw. , A reception-only probe that is arranged on a workpiece at a position away from the transmission / reception probe and receives a rectilinear wave where the reflected wave is removed from the surface wave, and these transmission / reception probe and reception-only probe An ultrasonic surface flaw detector is composed of an operator which receives a received signal of a child and discriminates the presence or absence of a flaw and the presence or absence of a foreign matter based on the presence or absence of a reflected wave and the strength of a straight wave.

As a concrete method, a transmitting / receiving probe is made to face a work such as a cylindrical object or a flat plate, and this probe is moved in a direction perpendicular to a surface wave traveling direction while the ultrasonic wave surface is moved from the probe. When a wave is transmitted and a reflected wave is received, the reflected wave is received, and the actual number of pulse reflections and the cumulative reflection intensity are obtained from the received contents.On the other hand, the depth of the defect from the known flaw, the number of pulse reflections and the cumulative reflection intensity are calculated. And the reference data is created in advance, and the depth of the flaw is estimated from the reference data and the actual number of times of pulse reflection and the cumulative reflection intensity.

Alternatively, a probe having at least a transmitting function and a probe having at least a receiving function are made to face a workpiece such as a cylindrical object or a flat plate, and these probes are moved in a direction perpendicular to the surface wave traveling direction. While transmitting ultrasonic surface waves from one probe, if there is a flaw, the rectilinear wave attenuated to some extent is received by the other probe and the actual number of pulse transmissions and cumulative transmission Obtain the intensity, on the other hand, to create a reference data by examining the relationship between the depth of the flaw from a known flaw and the number of pulse transmissions and the cumulative transmission intensity, and this reference data and the actual number of pulse transmissions and the cumulative transmission intensity and Estimate the depth of the flaw from.

[0011]

The surface wave is launched from the transmitting / receiving probe, and the rectilinear wave component of this surface wave is received by the receiving-only probe. On the way
If there is a flaw, part of the surface wave becomes a reflected wave and is received by the transmitter / receiver probe, or if there is a foreign substance such as scale on the work surface, the rectilinear wave is weakened and then received by the receive-only probe. . Therefore, by checking the reception levels of both probes, the presence / absence of a flaw, the presence / absence of a foreign matter, and the identification of a flaw and a foreign matter can be determined.

The depth of the flaw is estimated from the reference data, the actual number of pulse reflections and the cumulative reflection intensity.

Alternatively, the depth of the flaw is estimated from the reference data, the actual number of times of pulse transmission, and the cumulative transmission intensity.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a principle diagram of an ultrasonic surface flaw detector according to the present invention. The ultrasonic surface flaw detector 1 has a surface wave transmitting / receiving probe 2 facing one side of a work W (roll in the embodiment).
(Hereinafter abbreviated as “transmission / reception probe 2”) and a probe 3 dedicated to surface wave reception used in pair with the transmission / reception probe 2.
(Hereinafter abbreviated as "reception-only probe 3"), and flaw detector 4
And an arithmetic unit 5. These actions will be described later.

The transmitting / receiving probe 2 includes a flexible roller 11 ...
(... indicates a plurality, the same applies hereinafter) 12
And the holding material 12 is held by the arm 13,
The arm 13 is a slider 14 that slides in the front and back direction of the drawing.
Held in. The slider 14 is, for example, a motor 15,
It is driven by the pinion 16 and the rack 17 for accurate positioning. The probe 2 can be brought into and out of contact with the work W at any time by operating the cylinder 18. Also, 2
Reference numeral 1 denotes a medium supply pipe, which supplies the medium supplied from the contact medium supply box 22 on the slider 14 via the flexible hose 23 to the contact surface of the probe 2. Reference numeral 24 is a wiper, which is a foreign matter (scale, dust,
Water droplets).

The reception-only probe 3 is also a flexible roller 11
... is held by the slider 14 via the holding material 12, the cylinder 18, and the arm 13. The configuration is the transmitting and receiving probe 2
The description is omitted because it is the same as that of No.

FIG. 2 is a principle view of the probe according to the present invention. The transmitting / receiving probe 2 has a resin wedge 2a having a modified quadrangular cross section in which a rectangle is added to an equilateral triangle, and a cut crystal 2b is attached to the slope of the resin wedge 2a. Then, an ultrasonic wave is made incident at an angle i with respect to the perpendicular to generate a directional surface wave as indicated by an arrow on the surface of the work W. The transmitting / receiving probe 2 can also receive a surface wave in the direction opposite to the arrow. The reception-only probe 3 receives only surface waves on the same principle.

The operation of the ultrasonic surface flaw detector described above will be described below. In FIG. 1, when a surface wave is emitted from the transmission / reception probe 2, the surface wave goes toward the reception-only probe 3 as indicated by an arrow. If there is a flaw in the meantime, the surface wave is reflected by the flaw and returns to the transmitting / receiving probe 2.

3 (a) to 3 (d) are explanatory views of the operation according to the present invention. (A) is a case where the work W has no flaws and no foreign matter adheres to the surface, and the surface wave is the reception-only probe 3
And the reception level is extremely high. The reflected wave is 0 (zero). Therefore, the reception levels are shown as "high" and "0" in the lower part of the schematic diagram. (B) is a case where the work W has a flaw and no foreign matter adheres to the surface thereof, a part of the surface wave is reflected by the flaw, and the reflected wave returns to the transmitting / receiving probe 2. The component obtained by removing the reflected wave from the surface wave becomes a rectilinear wave and reaches the reception-only probe 3. Its reception level is medium.

(C) is a case where the work W has no flaws and foreign matter adheres to the surface thereof, and the surface wave is the transmitting / receiving probe 2
However, since it is attenuated by the foreign matter, the reception level of the rectilinear wave in the reception-only probe 3 becomes substantially medium. (D) is a case where the work W has a flaw and a foreign substance adheres to the surface, and a part of the surface wave is reflected by the flaw and returns to the transmitting / receiving probe 2. On the other hand, since the rectilinear wave component of the surface wave is weakened by the foreign matter, the reception level of the reception-only probe 3 becomes low.

Therefore, by combining the transmission / reception probe 2 and the reception-only probe 3, it is possible to detect a flaw as well as to identify a flaw and a foreign substance. 1)).

Based on the above flaw detection principle, the workpiece W shown in FIG. 1 is rotated counterclockwise at a constant speed to detect a flaw on the surface of the workpiece W. When the workpiece W makes one revolution, the slider 14 is rotated.
Is moved by one pitch (effective flaw detection width; for example, 5 mm), and flaw detection is performed again. At this time, the position (angle) of the flaw found by the calculator 5 is stored, and it is determined whether or not the flaw found during the previous rotation and the flaw found in the next time are the same flaw. .

Further, since the spherical roller of the free roller 11 rotates freely in all directions and can roll in the rotational direction of the work W and the axial direction of the work W, the movement of the slider 14 is not hindered. Further, the medium poured from the medium supply pipe 21 toward the probes 2 and 3 falls from the top to the bottom of FIG. The reception-only probe 3 is θ with respect to the transmission / reception probe 2.
= 135 °, the medium associated with it falls to the lower left of the figure, while the medium associated with the transmitting / receiving probe 2 falls to the lower right of the figure, and as a result, the medium does not reach in the vicinity of the arrow. Further, although it is possible to distinguish between a flaw and a foreign substance in the manner described with reference to FIG. 3, flaw detection is not intended to detect the foreign substance, and therefore the work W is in principle not to have the foreign substance on the surface. Therefore, the wiper 24 of FIG. 1 is used to forcibly remove the foreign matter.

Next, a method for checking the depth of a flaw with the device of the present invention will be described. FIGS. 4A and 4B are schematic diagrams of flaws, and in the case of a relatively small flaw as shown in FIG. 4A, the probes 2 and 3 are moved at the pitch P in the arrow direction (roll axis direction). Then, the surface wave collides with the flaw at the points P1 and P2, a part of the surface wave returns as a reflected wave, and the rest becomes an attenuated rectilinear wave and reaches the dedicated reception probe 3. That is, in (a), the reflected wave is measured twice. (B) is the case of a large flaw, and the reflection is P
It is measured 6 times from 1 to P6.

FIG. 5 is a graph showing the relationship between the reflection intensity and the flaw depth. The horizontal axis is the cumulative intensity of the reflected waves measured by the transmitting / receiving probe, and the vertical axis is the flaw depth. The flaw is deep. ● indicates the number of pulse reflections 1 to 3 times, ○ indicates 4 to 6 times,
△ indicates 7 times or more. Specifically, the existing work W is scratched and the intensity of the reflected wave is measured by the probe 2. The tendency is identified by ●, ○ and △, so that each is summarized by a straight line. . A part of the surface wave is reflected by the flaw and the rest becomes an attenuation wave and goes straight. Therefore, the deeper the flaw, the stronger the reflection intensity. Therefore, draw the upper right curve.

When the number of pulses is small, the cumulative intensity of the reflected wave becomes small. Therefore, the depth of the flaw must be sufficiently deep to generate the reflected wave as shown in the graph. On the contrary, when the number of pulses is large, the cumulative intensity of the reflected wave becomes large. The accumulated intensity of reflected waves increases even if the depth of the flaw is shallow. Thus, the depth of the flaw can be estimated by knowing the number of pulses and the reflection intensity.

FIG. 6 is a graph showing the relationship between transmission intensity and flaw depth. The horizontal axis represents the cumulative intensity of surface waves measured by the reception-only probe, and the vertical axis represents the flaw depth. The flaw is deep. ● indicates the number of pulse transmissions 1 to 3 times, ○ indicates the same 4 to 6 times,
△ indicates 7 times or more. Specifically, the existing work W is scratched and the intensity of the surface wave is measured by the probe 3, and the trends are indicated by ●, ○, and △, so that each is summarized by a straight line. . A part of the surface wave is reflected by the flaw, and the rest of the surface wave becomes an attenuation wave and travels straight. Therefore, the shallower the flaw, the higher the transmitted intensity. Therefore, draw a downward-sloping curve.

Since the reflection intensity and the transmission intensity have an inverse relationship to each other, FIG. 6 has a tendency opposite to that of FIG. 5, and the depth of the flaw can be estimated by knowing the pulse transmission frequency and the transmission intensity. You can Note that FIG. 5 is a reference graph created by actually measuring flaws of known depth and width with the well-tuned transmitting and receiving probe 2, and FIG. 6 similarly shows flaws of known depth and width. It is a reference graph created by actually measuring the transmission-only probe 2 and the reception-only probe 3 which are well adjusted, and is characterized in that the depth of a flaw is estimated from these reference graphs and actual measurement values. There is.

The depth of the flaw can be individually calculated from the reflected wave and the straight wave, but when the depth of the flaw thus found is D1 and D2, the flaw removal grinding amount of the larger one of D1 and D2 is obtained. It is arbitrary to adopt a numerical value or an average value of D1 and D2. Furthermore, when the difference between D1 and D2 is great, a measurement error may occur. This processing may be performed freely by the arithmetic unit 5 of FIG.

Next, an actual measurement example of the present invention will be described. The actual measurement conditions are as follows. Work Roll Roll 800 mm Roll width 1840 mm Roll surface flaw 0.25 mm Depth and 0.3 mm depth 1 flaw each Roll material Nickel chrome steel Roll rotation 20 rpm Testing frequency 5 MHz Testing sensitivity Depth 0.2 mm, Length 1 0.0 mm, width 10
The sensitivity when the artificial flaw of mm was measured at the position 50 mm away was set to 50%, and the sensitivity was further +6 dB. Roll axial pitch 5 mm

As a result of actual measurement under the above conditions, the inspection time is 20 minutes, the detection flaw is two, the detection depth is 0.21 mm on the one hand, and 0.34 mm on the other hand. , ± 0.
It was confirmed that it can be estimated with an accuracy of about 05 mm.

According to the present invention, not only the presence or absence of a flaw but also the depth of the flaw can be estimated. Therefore, it is not necessary to excessively perform roll grinding as in the conventional case, and the grinding amount can be kept within an appropriate range. The processing time can be shortened and the life of the rolling roll can be extended.

In this embodiment, the transmitting / receiving probe 2 and the receiving probe 3 are arranged in a pair, but the present invention is not limited to this. For example, although the transmitting / receiving probe 2 is preferably integrated, it is composed of a transmitting-only probe and a receiving-only probe,
These may be arranged close to each other. In addition, the reception-only probe 3 is changed to a transmission / reception probe, and normally only the reception function is used, and when the transmission function of the other transmission / reception probe 2 fails, the transmission function is utilized. You may Furthermore, in order to detect a flaw with a straight wave according to FIG.
The transmitting / receiving probe is not always necessary, and it is sufficient to have “a probe having at least a transmitting function” and “a probe having at least a receiving function”.

Although the slider 14 is moved one pitch after the work W is rotated once in the embodiment, the invention is not limited to this, and the rotation of the work W and the slider 14 are not limited thereto.
May be simultaneously performed. The loci of the probes 2 and 3 are spiral, but the flaw detection time is short.

[0035]

The present invention has the following effects due to the above configuration. The ultrasonic surface flaw detector according to claim 1 comprises a transmission / reception probe and a reception-only probe, and by checking the reception levels of both probes, presence / absence of flaws, presence / absence of foreign matter, and flaw / foreign matter Since the identification can be performed, the flaw detection accuracy is increased, which is preferable.

According to the ultrasonic surface flaw detection method of claim 2,
Since the depth of the flaw can be estimated from the reference data, the actual number of pulse reflections, and the cumulative reflection intensity, it is possible to prevent the work from being over-cut and prolong the life of the work.

According to the ultrasonic surface flaw detection method of claim 3,
Since the depth of the flaw can be estimated from the reference data, the actual number of times of pulse transmission, and the cumulative transmission intensity, it is possible to prevent the work from being over-cut and prolong the life of the work.

[Brief description of drawings]

FIG. 1 is a principle diagram of an ultrasonic surface flaw detector according to the present invention.

FIG. 2 is a principle diagram of a probe according to the present invention.

FIG. 3 is an explanatory view of the operation according to the present invention.

FIG. 4 is a schematic diagram of a flaw according to the present invention.

FIG. 5 is a graph showing the relationship between reflection intensity and flaw depth according to the present invention.

FIG. 6 is a graph showing the relationship between transmission intensity and flaw depth according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ultrasonic surface flaw detector, 2 ... Transmitting / receiving probe, 3 ... Receiving probe, 5 ... Arithmetic unit, 11 ... Free roller, 12 ...
Holding material, 13 ... Arm, 14 ... Slider, 15 ... Motor, 18 ... Cylinder, 21 ... Medium supply pipe, 24 ... Wiper, W ... Work.

Claims (3)

[Claims] 1. An ultrasonic surface flaw detector for detecting flaws on the surface of a workpiece such as a cylindrical object or a flat plate with an ultrasonic surface wave. The ultrasonic surface flaw detector sends a surface wave to the workpiece.
When there is a flaw, the probe for transmission and reception where the reflected wave due to this flaw is received, and the work is placed at a position apart from the probe for transmission and reception, and the reflected wave is removed from the surface wave. However, the reception-only probe that receives the rectilinear wave, and the reception signals of these transmission / reception probe and reception-only probe are input, and the presence / absence of flaws and foreign matter due to the presence or absence of the reflected wave and the strength of the rectilinear wave. An ultrasonic surface flaw detector, comprising an arithmetic unit for identifying the presence / absence. 2. An ultrasonic surface wave is emitted from the probe while a transmitting and receiving probe is exposed to a work such as a cylindrical object or a flat plate, and the probe is moved in a direction perpendicular to the surface wave traveling direction. If there is a flaw, the reflected wave is received, and the actual number of pulse reflections and the cumulative reflection intensity are obtained from this received content.On the other hand, the relationship between the depth of the flaw from the known flaw, the number of pulse reflections, and the cumulative reflection intensity is calculated. An ultrasonic surface flaw detection method characterized in that the depth of a flaw is estimated from the reference data and the reference data and the actual number of times of pulse reflection and the cumulative reflection intensity. 3. A work such as a cylindrical object or a flat plate is made to face a probe having at least a transmitting function and a probe having at least a receiving function, and these probes are moved in a direction perpendicular to a surface wave traveling direction. While transmitting ultrasonic surface waves from one probe, if there is a flaw, the rectilinear wave attenuated to some extent is received by the other probe and the actual number of pulse transmissions and cumulative transmission Obtain the intensity, on the other hand, to create a reference data by examining the relationship between the depth of the flaw from a known flaw and the number of pulse transmissions and the cumulative transmission intensity, and this reference data and the actual number of pulse transmissions and the cumulative transmission intensity and An ultrasonic surface flaw detection method characterized by estimating the depth of a flaw from the surface.