JPH10282069A - Ultrasonic flaw detector and sensitivity calibration method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To position a probe mechanism quickly and easily with high accuracy without replacing the probe mechanism for different shape of steel member to be inspected by adjusting the azimuth, distance and height of an ultrasonic probe with respect to the steel member to be inspected. SOLUTION: In a flaw detector suspended from an upper frame 15, the angle and the position of a probe holder 1 is adjusted previously depending on the shape or size of a rail R to be inspected and the flaw detector is lowered under that state and set automatically at a specified position. At that position, the rail R abuts against copy rollers 12a, 12b and the probe holder 1 follows up the rail R while keeping a constant distance (water column distance) from a plane to be inspected thus realizing a stabilized flaw detecting operation. The probe holder 1 is elevated/lowered, traversed or turned by operating an elevating/lowering motor 7, a traverse motor 10 or a stepping motor 4 and the water column distance of an ultrasonic medium can be sustained correctly for other type of rail of different size.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic inspection apparatus for inspecting an internal defect by applying ultrasonic waves to a material having a curvature represented by a rail, and a sensitivity calibration method thereof.

[0002]

2. Description of the Related Art Conventionally, an ultrasonic flaw detector for inspecting an internal defect of a material to be inspected having a curvature, such as a rail or a square steel material, is equipped with a probe holding mechanism that matches each shape of the steel to be inspected. As many as the number corresponding to the type of the inspection steel were prepared, and each time the type changed, the holding mechanism was replaced and the probe was replaced. Moreover, the angle of incidence of the ultrasonic wave was physically fixed by matching the probe holding mechanism to the shape of the steel material to be inspected.

[0003] Japanese Patent Application Laid-Open No. 1-65445 discloses that
A probe is disclosed in which an ultrasonic wave propagation direction changing means including a worm gear and a worm wheel is provided in a part of a mechanism, and an incident angle at which a plate wave mode optimal for flaw detection is generated can be specified.

[0004]

However, a flaw detector which replaces the probe holding mechanism corresponding to the shape of the steel to be inspected each time and physically fixes the incident angle of the ultrasonic wave to the steel to be inspected. In the case of, in addition to the disadvantages in equipment and operation,
There is a problem that a fine adjustment operation occurs and an adjustment time is required due to a delicate difference in a mounting method when the probe is incorporated in the holding mechanism.

In the technique described in Japanese Patent Application Laid-Open No. 1-65445, the probe is merely held inside the rotating tire portion via an arc-shaped driving mechanism, and the vertical and horizontal movements are limited. It cannot be said that the structure is not suitable for flaw detection of a material to be inspected having a curvature to be flaw-detected according to the present invention.

The present invention has been made in view of such a point, and simply, quickly and accurately positions a predetermined position in a predetermined position without changing a probe holding mechanism corresponding to a shape of a steel material to be inspected. It is an object of the present invention to provide an apparatus which is capable of performing ultrasonic inspection of a steel material to be inspected having a curvature.

[0007]

According to a first aspect of the present invention, there is provided a flaw detection apparatus according to the present invention, wherein a surface of a steel material to be inspected having a curvature is conveyed while traveling. In an ultrasonic flaw detector for directing an ultrasonic probe fixed to a probe holding mechanism to inspect an internal defect, a vertical rotation mechanism, an elevating mechanism, and a traversing mechanism are added to the probe holding mechanism. In addition, the directivity angle, distance, and height position of the ultrasonic probe with respect to the steel material to be inspected can be adjusted.

[0008] The vertical rotation mechanism attached to the probe holding mechanism includes a probe holding plate for holding a probe holder having a built-in probe, and a surface of a steel material to be inspected provided on the probe holding plate. And a drive unit for providing an arc-shaped trajectory within a certain angle range with the fulcrum as a fulcrum (claim 2). Further, an elevating mechanism and a traversing mechanism attached to the probe holding mechanism hold the holding plate on a slide guide plate, and the slide guide plate is slidably provided in a vertical direction by a driving device. Is provided with another drive device that enables the vehicle to traverse in a substantially horizontal direction (claim 3).

On the other hand, a method according to claim 4 of the present invention is a method for calibrating the sensitivity of an ultrasonic flaw detector using an identically shaped steel material with an artificial defect, which is a preliminary operation for an internal defect inspection of a steel material to be inspected. Using the directional rotation mechanism, each probe holding plate is moved along the arc-shaped locus with the surface of the steel material to be inspected as a fulcrum, and the probe holder is set so that the ultrasonic incidence angle becomes the optimum sensitivity. Is set as the configuration content.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below. Prior to that, points to be considered when performing ultrasonic flaw detection on a steel material to be inspected having a curvature as in the present invention. , And the nature of the ultrasonic wave. Ultrasonic waves have a property of being reflected when hitting not only on the rail but also on the surface or the deformed portion of the steel material to be inspected. When an ultrasonic wave transmitted from an ultrasonic probe reaches a steel to be inspected through a medium such as water or oil for an internal defect inspection of the steel to be inspected, first, a surface reflection echo returns on the surface of the steel to be inspected. . The ultrasonic wave propagates through the steel to be inspected, and if there is a defect inside the steel, a defect echo proportional to the size of the defect is reflected. Furthermore, when the ultrasonic wave propagates through the steel to be inspected and reaches the bottom surface,
The bottom echo is reflected. This is shown in FIG.

When an ultrasonic wave enters a boundary surface obliquely, the reflection and refraction obey Snell's law as in the case of light. When ultrasonic waves are incident on steel from water, which is an ultrasonic medium, C _W / sin i
The relationship of _C = C _L / sin θ _L holds. Where C _W is the velocity of sound in water, C _L is the velocity of longitudinal waves in steel, i _C is the angle of incidence,
θ _L is the refraction angle.

Generally, the underwater sound speed is 1480 m / sec, the longitudinal wave sound speed in steel is 5960 m / sec, and θ _L = arc sin
(5960/1480 × sin i _C ). This indicates that even if it is intended to be vertically incident in the water immersion method, if it is tilted by 1 °, it is tilted by about 4 ° in steel by the above equation.

For example, the above will be described with reference to an example of a rail head provided with a flat bottom artificial defect. One probe was used for convenience. FIG. 6 shows the relationship between the cross-sectional shape of the rail head, the traveling direction of longitudinal ultrasonic waves, and artificial defects. Based on Snell's law, when an ultrasonic wave is incident at an angle of incidence i _C from the normal direction of the head surface such that it hits the artificial defect bottom surface perpendicularly, it is refracted by θ _L and the ultrasonic wave strikes the artificial defect bottom surface perpendicularly. At this time, the reflection flaw signal F becomes maximum (see FIG. 6B).

Next, FIG. 7 shows a state when the incident angle changes by i _C + 1 °. As can be seen from FIG. 7, the refraction angle is θ _L
Since the angle is about + 4 °, the ultrasonic wave does not hit the artificial defect bottom surface vertically. As a result, as shown in FIG. 7B, it is found that the reflection flaw signal F at this time is attenuated as compared with the case of the incident angle i _C.

From the above, when the bottom of the artificial defect and the directing direction of the ultrasonic wave deviate from the normal line due to a delicate difference in how the probe is incorporated into the holder, the reflection flaw signal is attenuated. Therefore, the sensitivity must be increased more than necessary in order to make the magnitude of the specified flaw signal, and it is required to set the incident angle at which the reflection flaw signal is maximized with high accuracy. In particular, regarding ultrasonic flaw detection for a steel material having a curvature such as a rail, strict fine adjustment is required for the direction of ultrasonic waves, and thus fine adjustment for positioning is conventionally repeated.

According to the present invention, means for vertically rotating, raising and lowering, and traversing operations are provided in each holding mechanism of the plurality of probes according to the shape, height, width, and position of the steel material to be inspected. Mounted, the directional angle of the ultrasonic probe with respect to the steel to be inspected,
The distance and the height position can be adjusted appropriately so that the probe can always be quickly and accurately set at the optimum position with respect to the steel material to be inspected. That is, a single device can be used without changing the probe holding mechanism according to the shape or size change of the steel material to be inspected.

In the present invention, the probe holding mechanism includes a probe holder having a built-in ultrasonic probe (probe);
A holding plate for fixedly holding the holder, and a frame for supporting the holding plate. Therefore, if the holding plate itself is rotated in the vertical direction, ascending and descending and traversing, the probe holder is accordingly rotated, ascending and descending and traversing, and the angle of the steel to be inspected with respect to the surface to be inspected, the height position, The distance from the surface to be inspected is kept optimal. Usually, a plurality of sets of the probe and the holding mechanism are arranged. However, at the time of the flaw detection operation, these sets may be interlocked, or may be operated independently.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to the accompanying drawings. The case where a rail to be inspected is used as an example and the inside of the rail is subjected to ultrasonic flaw detection will be described. FIG. 1 shows an apparatus provided with a pair of flaw detection mechanisms having the same structure from both sides of a rail to be inspected R conveyed at a constant speed in a longitudinal direction. Actually, a plurality of sets of flaw detection devices are arranged along the rail transport line, and are arranged so that flaw detection operation can be performed on the entire cross section of the rail.

As shown in FIG. 1, the whole flaw detector is suspended on an upper frame 15 straddling a rail transport line, and can be moved up and down with respect to the rail R by a driving device such as a cylinder. Therefore, before the flaw detection operation starts, the flaw detection device at the upper standby position adjusts the angle and position of the probe (holder) according to the shape and size of the rail to be inspected in advance, and moves down in that state. If it is, it is automatically set at a predetermined position. In this position, the copying rollers 12a, 12b, and 12c (12c are not shown) abut on the rail R, and the copying rollers follow the rail surface during the flaw detection operation. Even if vibration occurs, the probe holder follows the surface to be inspected while maintaining a constant distance (ie, a constant water column distance), so that a stable flaw detection operation can be performed.

In order to set the probe (holder) of the flaw detector to a predetermined position in advance as described above, a vertical rotation mechanism, a lifting mechanism, and a traversing mechanism are incorporated in the probe holding mechanism. Hereinafter, specific examples of each of these mechanisms will be described. FIG. 2 shows an example of a vertical rotation mechanism, which has a probe holder 1 also serving as a water nozzle for flowing water serving as an ultrasonic medium, and an arc-shaped tooth profile for attaching and holding the probe holder 1. Holding plate 2 and steel plate (rail) to be inspected
The basic configuration includes an arc slide guide 3 that enables circular motion in the vertical direction over a certain angle range with the surface of R as a fulcrum, and a stepping motor 4 that serves as a drive source for applying the circular motion to the holding plate 2.

A probe P is fixed inside the probe holder 1, and it is not necessary to remove the probe even if the shape of the steel material to be inspected changes. If this happens, only the probe in the holder needs to be replaced. As shown in FIG. 2B, a hole for supplying water serving as an ultrasonic medium is provided on the rear surface of the probe holder 1, and the inside of the holder is always filled with water. Spouted from the front of the holder, maintaining a water column. The water column hits the surface of the steel to be inspected and forms an ultrasonic medium with the surface of the steel to be inspected.

A probe holder 1 is fixed to one end of the holding plate 2, and a tooth profile is formed in an arc shape at the other end, and the arc tooth profile is engaged with the circular gear 4 a of the stepping motor 4. . The holding plate 2 is supported by the slide guide plate 6 on the other end side, and has a receiving frame 3a for engaging the arc slide guide 3 fixed to the slide guide plate 6. The arcuate slide guide 3 and the receiving frame 3a, the tooth profile of the holding plate 2 and the stepping motor 4
With the circular gear 4a described above, the holding plate itself takes a vertical rotation locus such that the inspection surface of the rail is a fulcrum. In addition,
A groove 2a is formed parallel to the tooth profile of the holding plate 2 and the slide guide 3, and the pin 5 provided on the slide guide plate 6 is inserted into the groove to prevent the holding plate from falling off and rotate. (Angle α).

Further, the slide guide plate 6 is shown in FIG.
As shown in (b) and (c), it has a receiving frame 9a which engages with the vertical slide guide 9 of the side frame 16, and is vertically movable. As the lifting mechanism, a worm gear 8 meshed with a screw 7a rotated by a lifting motor 7 provided on the frame 16 side is provided with a slide guide plate 6.
The worm gear 8 is moved up and down by driving the elevating motor 7 to move up and down.

Further, the holding plate 2 and the slide guide plate 6
Are traversed in a substantially horizontal direction, and the same traversing mechanism as the elevating mechanism is adopted as a traversing mechanism for adjusting the distance between the rail surface and the probe holder 1. That is, FIG.
(A) and (b) show specific examples of the traversing mechanism. The traversing frame 17 to which the upper portion of the holding plate support frame 16 is fixed is connected to an intermediate frame 18 for holding the entire apparatus (see FIG. 1).
The slide guide 19 and the slide guide frames 11a, 1
1b so as to be slidable in a direction intersecting with the rail R via the first frame 1b. It is configured to traverse.

By operating the lifting motor 7, the traversing motor 10 and the stepping motor 4 as described above, the probe holder 1 is raised and lowered, traversed, and rotated. It is possible to appropriately maintain the water column distance (L) of the sonic medium.

In the above-described embodiment, the case where the motor is used as the drive source for performing the ascending, descending, traversing, and circularly rotating operations has been described, but other known driving means such as a cylinder may be used instead. It may be used, and in some cases, it may be all manually.

Next, since a control device is attached to the above-described ultrasonic flaw detector and all operations can be automatically and easily positioned, the present invention is used in the sensitivity calibration work which is a preparatory work for the internal defect inspection of the steel to be inspected. Using the ultrasonic flaw detector, the optimum sensitivity calibration operation can be performed simply, quickly and accurately.

FIG. 4 shows the flow of the pre-sensitivity calibration operation. First, each mechanism of the flaw detector is set to a preset angle (predetermined by a rail shape or the like) with respect to a reference rail having an artificial defect having the same shape as the rail to be inspected. Thereafter, the range of the preset angle ± X ° (for example, 2 °) is set to the scanning pitch Y °.
Angle scanning is performed at (X> Y, for example, 1 °). At this time, the height of the flaw signal from the artificial defect is sequentially stored, and the angle at which the flaw signal is maximized is obtained. Next, based on the obtained angle, the range of ± Z ° (X> Z) is again scanned at a scanning pitch W ° (Y> W, for example, 0.2 °). Flaw signal height is stored in sequence,
The angle at which the flaw signal is maximized is determined. The same scanning is repeated N times, and the angle at which the flaw signal becomes maximum is gradually narrowed, so that the incident angle of the ultrasonic wave can be optimized. Here, X, Y, Z, W and the number of repetitions N may be set in the control device in advance.

[0029]

As described above, according to the ultrasonic flaw detector according to the present invention, it is possible to simply and quickly move the probe to a predetermined position without changing the probe holding mechanism corresponding to the shape of the steel material to be inspected. The probe can be positioned well. Also,
According to the calibration method of the present invention, in the calibration work before the inspection of the internal defect of the steel material to be inspected, the ultrasonic incidence angle can be set to the optimum sensitivity, so that the internal defect inspection of the steel material to be inspected after the sensitivity calibration work is performed. Can be prevented from being over-detected,
Inspection ability is improved.

[Brief description of the drawings]

FIG. 1 is an overall front view showing one embodiment of an ultrasonic flaw detector according to the present invention.

2A and 2B are diagrams illustrating a probe rotating mechanism and a lifting mechanism in the probe holding mechanism shown in FIG. 1, wherein FIG. 2A is a front view of the holding mechanism, and FIG. 2B is a bottom view of FIG. (C) is a side view of (a).

3A and 3B are diagrams showing a specific example of the probe traversing mechanism in FIG. 1, wherein FIG. 3A is a side view thereof, and FIG. 3B is a view taken along the line AA of FIG.

FIG. 4 is a flowchart showing a series of operations up to determination of an optimum angle in the sensitivity calibration method of the present invention.

FIG. 5 is a view for explaining basic properties of ultrasonic flaw detection.

FIG. 6 is a diagram for explaining basic characteristics of refraction and reflected echoes when ultrasonic waves enter a material in ultrasonic flaw detection for a rail to be inspected.

FIG. 7 is a diagram showing a refraction characteristic and a reflected echo when the incident angle is changed in the state of FIG. 5;

[Explanation of symbols]

REFERENCE SIGNS LIST 1 probe holder 2 holding plate with arcuate teeth 3 arcuate slide guide 3 a slide guide receiving frame 4 stepping motor 5 pin 6 slide guide plate 7 elevating motor 8 worm gear 9 slide guide 9 a slide guide receiving frame 10 traverse motor 11 a , 11b Slide guide frame 12a, 12b, 12c Copying roller 15 Holding frame 16 Holding plate support frame 17 Crossing frame 18 Intermediate frame 19 Slide guide 20 Rotation-straight transmission mechanism P Probe R Rail to be inspected

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Osamu Furumi, Inventor, 1-1 1-1 Tobata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka Prefecture Nippon Steel Corporation Yawata Works (72) Inventor: Shin Murata Hibata, Tobata-ku, Kitakyushu-shi, Fukuoka No. 1-1, New Town Nippon Steel Corporation Yawata Works (72) Inventor Toshiharu Tsuboi 1-9-29 Kakuda, Higashiosaka City, Osaka Inside Japan Kraut Kramer Co., Ltd.

Claims (4)

[Claims] 1. An ultrasonic probe fixed to a probe holding mechanism is directed toward a surface of a steel material to be inspected while the steel material to be inspected having a curvature is conveyed while running, and an internal defect is inspected. In the ultrasonic flaw detector, the probe holding mechanism is provided with a vertical rotation mechanism, an elevating mechanism, and a traversing mechanism, so that the directivity angle, distance, and height position of the ultrasonic probe with respect to the steel to be inspected can be adjusted. An ultrasonic flaw detector characterized by the following. 2. A vertical rotation mechanism attached to a probe holding mechanism, comprising: a probe holding plate for holding a probe holder containing a probe; and a steel material to be inspected attached to the probe holding plate. 2. The ultrasonic flaw detector according to claim 1, further comprising: a drive unit for providing an arc-shaped trajectory within a certain angle range with the surface as a fulcrum. 3. A lifting mechanism and a traversing mechanism attached to the probe holding mechanism, wherein the holding plate is held by a slide guide plate,
3. A super-computer according to claim 1, wherein said slide guide plate is slidably provided in a vertical direction by a drive device, and another drive device is provided for enabling said slide guide plate to traverse in a substantially horizontal direction. Sonic flaw detector. 4. A method of calibrating the sensitivity of an ultrasonic flaw detector using an identically shaped steel material with an artificial defect, which is a preparatory operation for an internal defect inspection of a steel material to be inspected, wherein the vertical rotation mechanism according to claim 2 is used. Ultrasound characterized by setting the probe holder so that the probe holding plate is moved along the arc-shaped trajectory with the surface of the steel material to be inspected as a fulcrum, and the angle of incidence of the ultrasonic wave for optimum sensitivity is set. A method for calibrating the sensitivity of a flaw detector.