JP5263178B2 - Nondestructive inspection method for steel rails for tracks - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of automatically and precisely determining a material defect section without any visual verification even if the material defect section occurs on the surface of a steel rail for a track. <P>SOLUTION: In the method of nondestructively inspecting the steel rail for the track for detecting the material defect section occurring on the surface of a plurality of steel rails for the track joined by flash-butt welding, based on a signal outputted from a vortex flow flaw inspection probe 11a, a linear vortex flow flaw inspection is performed by performing scanning of the vortex flow flaw detection probe 11a along a longitudinal direction of a rail on a rail surface 1a, the vortex flow flaw inspection probe 11a is moved in a direction A orthogonal to the longitudinal direction of a rail on the rail surface 1a, and adjustment of a zero point in a level of a signal outputted from the vortex flow flaw inspection probe 11a is performed repeatedly within a prescribed range on the rail surface, thus performing a vortex flow flaw inspection of the prescribed range. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  TECHNICAL FIELD The present invention relates to a nondestructive inspection method for rails for rails for detecting material abnormalities occurring on the surface of rails for rails (hereinafter also simply referred to as “rails”). The present invention relates to a nondestructive inspection method for rails for rails suitable for detecting an abnormal material portion occurring on a contact surface between an electrode and a rail and the vicinity thereof when joining a plurality of rails in series by flash butt welding.

  The rail steel rail is for supporting the load of the railway vehicle, and a large repetitive load is applied each time the vehicle passes. For this reason, if defects such as defects generated inside or on the surface of the rails during manufacturing or welding, or defects generated or grown due to repeated loads acting during use as a railway track, are overlooked Destruction can lead to serious accidents.

  In addition, when manufacturing and laying steel rails for tracks, factory welding and on-site welding are performed to manufacture long rails. When welding these steel rails, the purpose is to shorten the welding time and reduce thermal effects. Flash butt welding is often used. In this flash butt welding, the longitudinal ends of the rails are welded to each other by passing a large current from the electrodes pressed against the two rails that are in contact with each other in the longitudinal direction of the rails. Is. There are two methods for pressing this electrode against the rail: a method in which the electrode is pressed against the surface of the rail column from the horizontal direction, and a method in which the electrode is pressed against the surface of the rail head and legs from the vertical direction. Is adopted.

  In flash butt welding in the rail welding factory or at the rail laying site, the contact resistance between the electrode and the rail is non-uniform, resulting in partial current concentration or partial discharge between the electrode and the rail surface. As a result, a part of the rail surface may be greatly heated locally. In this case, due to the rapid cooling after the heating, a martensite structure is generated in a locally heated region, and a material abnormal portion having a hardness extremely higher than that of the peripheral portion is locally generated.

  In particular, rail steel rails are often made of pearlite steel containing 0.7% by mass or more of carbon, and are inherently highly hardenable. It has become.

  When such a material abnormal part occurs on the rail surface, as with the above-mentioned flaw defect, when a repeated load is applied to the material abnormal part, it is seriously caused by the failure starting from the material abnormal part. May lead to serious accidents.

  Such a rail surface abnormal material part is accompanied by discoloration of the rail surface and can be visually confirmed by the welding operator. However, if the material abnormal part is very small, or a material abnormal part has occurred especially on the back of the rail. If you think you might miss this. Further, although it is possible to reduce the occurrence frequency of the material abnormal portion by the maintenance of the electrode surface, the pressing method of the electrode to the rail, the control method of the welding current, etc., it is difficult to eliminate it at all. For these reasons and from the viewpoint of reducing the load on the welding operator, it has been desired to establish a method for automatically detecting an abnormal material portion on the surface of a rail steel rail without visual confirmation.

  Here, conventionally, after flash butt welding of rails for rails, non-destructive inspection has been performed, the purpose of which is to investigate the presence or absence of defects on the surface or inside of the rail. Yes. Non-destructive inspection methods for such rails include radiation transmission testing, magnetic particle testing, ultrasonic testing, penetration testing, eddy current testing, etc., depending on the rail shape, material, testing environment, etc. Various test methods are used properly. Among these nondestructive inspection methods, the magnetic particle testing method, the penetrant testing method and the eddy current testing method are mainly suitable methods for inspecting surface defects. On the other hand, the radiation transmission test method and the ultrasonic flaw detection method are mainly suitable for detection of internal flaw defects.

  In particular, the ultrasonic flaw detection method can detect internal defects safely and easily compared to the radiation transmission test method, so it is formed inside the rail in the rail welding factory and on the site after the rail is laid. It is frequently used to detect cracks, blow holes, cast holes, and the like. For example, Patent Document 1 discloses a rail flaw detection aid used when applying an ultrasonic flaw detection method to a rail. This is applicable not only to pre-shipment inspections in rail welding plants, but also to rails after they have been laid on site, and has a simple structure and excellent inspection accuracy, position accuracy, and work efficiency. ing. This rail flaw detection aid includes a probe holding portion for holding a probe for detecting defects inside the rail by ultrasonic flaw detection, a slide portion for moving the probe holding portion along the longitudinal direction of the rail, and the slide portion as a rail. And a fixing portion for fixing to. Further, a measure for measuring the amount of movement of the probe is provided on the slide portion. Further, the probe holding portion is provided with an elastic member that urges the holding plate holding the probe upward.

  As for the eddy current flaw detection method, Patent Document 2 discloses an eddy current flaw detection probe, a eddy current flaw detection apparatus, and a eddy current flaw detection method that can easily inspect a portion overlapping with another member such as a joint of a steel rail for a track. Has been. The eddy current flaw detection probe disclosed in Patent Document 2 includes a flaw detection part that is inserted into a gap with a rail joint plate and flaws detected, and a lead part that is inserted into the gap to scan the flaw detection part. However, it has a flaw detection coil made of a printed coil, and the flaw detection portion of the eddy current flaw detection probe is inserted into a gap between the rail joint plate and the flaw detection is performed while scanning in a predetermined direction.

JP 2005-188930 A JP 2005-221273 A

  However, the ultrasonic flaw detection method and rail flaw detection auxiliary tool disclosed in Patent Document 1 above, and the eddy current flaw detection probe, eddy current flaw detection device, and eddy current flaw detection method disclosed in Patent Document 2 are not limited to rail surface defects. In addition, there is a problem that it is intended for internal flaw defects and is not suitable for detection of an abnormal material portion such as a hardened structure formed only on the surface layer without flaw defects such as notches.

  Therefore, the present invention has been devised in view of the above-described problems, and its object is to provide a martensitic structure on the surfaces of a plurality of rail steel rails joined in series by flash butt welding. It is an object of the present invention to provide a non-destructive inspection method for rails for rails that can automatically and highly accurately detect an abnormal material portion such as a material without visual confirmation.

  The present invention has the following features in order to solve the above-described problems.

  A nondestructive inspection method for rail steel rails according to a first aspect of the present invention is a signal output from an eddy current flaw detection probe for material abnormalities occurring on the surfaces of a plurality of rail steel rails joined in series by flash butt welding. In the non-destructive inspection method of the steel rail for tracks to be detected based on the rail surface, the rail surface is subjected to a linear eddy current inspection by scanning the eddy current inspection probe along the rail longitudinal direction of the rail surface. Until the zero level adjustment of the signal level output from the eddy current flaw detection probe is performed in a predetermined range on the rail surface. The eddy current flaw inspection for the predetermined range is performed.

  The nondestructive inspection method for rail steel rails according to the second invention is the method according to the first invention, wherein the material abnormal portion is determined as a rail steel rail joined by flash butt welding, and the eddy current flaw detection is performed. The predetermined range to be inspected is the range in which the electrode and the rail are in contact with each other at the time of flash butt welding in the longitudinal direction of the rail, and the range from this to the part spaced by 10 mm or more and 30 mm or less toward the welded portion. The direction perpendicular to the rail longitudinal direction on the surface of the rail is a range in which the electrode and the rail come into contact during flash butt welding.

  A nondestructive inspection method for a rail steel rail table according to a third aspect of the invention is the first or second aspect of the invention, wherein the moving speed of the eddy current flaw detection probe at the time of scanning along the rail longitudinal direction is constant. It is characterized by that.

  According to the first to third inventions, the range to be inspected at the time of the eddy current flaw inspection is set to a two-dimensional range on the rail surface, and the material abnormal part generated in this range is accompanied by visual confirmation. It is possible to detect automatically and with high accuracy. This makes it easy to control the quality of track steel rails, and can prevent the occurrence of serious accidents due to failure starting from abnormal material parts that are a concern when repeated loads are applied during use. It becomes. In addition, it is possible to grasp the two-dimensional distribution information indicating the occurrence range and size of material abnormalities that have occurred on the rail surface, and it is also possible to easily collect, store, and accumulate information related to these material abnormalities. As a result, it can exert a great effect on the industry.

  According to the second invention, it is possible to reliably detect most of the material abnormal portions that may occur when the rail is flash-butt welded. In addition, the range to be inspected can be prevented from becoming excessively wide, and the inspection time can be shortened.

  According to the third invention, at the time of eddy current flaw inspection, it is possible to obtain stable detection ability and improve detection accuracy.

It is a block diagram which shows an example of the nondestructive inspection system for implementing this invention. It is a typical top view of a flaw detection inspection auxiliary tool for explaining operation of a flaw detection inspection auxiliary tool. (A) is a perspective view which shows the state at the time of carrying out flash butt welding of the rail longitudinal direction edge parts of two rails, (b) is the front sectional drawing. It is a perspective view which shows the state of the rail after flash butt welding is completed. It is a top view which shows typically the scanning procedure at the time of scanning an eddy current flaw detection probe by making a test | inspection direction into a rail longitudinal direction. It is a top view which shows typically the scanning procedure at the time of scanning an eddy current flaw detection probe by making an inspection direction into a rail width direction. (A) is a schematic diagram showing a signal detected when an eddy current flaw inspection is performed along a rail width direction of a rail steel rail, and (b) is detected when an eddy current flaw inspection is performed along a rail longitudinal direction. It is a schematic diagram which shows the signal to be performed. (A) is a schematic diagram which shows the signal detected when the eddy current flaw inspection is carried out along the rail longitudinal direction of the rail width direction end of the steel rail for the track, and (b) is a rail at the rail width direction center. It is a schematic diagram which shows the signal detected when an eddy current flaw inspection is carried out along a longitudinal direction. It is a top view which shows typically the other scanning procedure at the time of scanning an eddy current test probe. It is a schematic diagram which shows the signal detected when it determines with there being a material abnormality part. It is an image figure which shows an example of the information output and displayed after an eddy current test.

  Hereinafter, an example of an embodiment of a nondestructive inspection method for steel rails for tracks according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing an example of a nondestructive inspection system 10 for carrying out the present invention.

  The nondestructive inspection system 10 includes an eddy current flaw detection probe 11a, an eddy current flaw detection apparatus 11 for performing an eddy current flaw inspection on the rail surface 1a, and a flaw detection inspection auxiliary tool 20 for assisting the eddy current flaw inspection by the eddy current flaw detection apparatus 11. And an external control device 13 for controlling the operation of the flaw detection inspection aid 20, a data recorder 15 connected to the eddy current flaw detection device 11, and a material abnormal portion determination device 17 connected to the data recorder 15. Yes.

  The eddy current flaw detection apparatus 11 is an apparatus that performs eddy current flaw inspection on the rail surface 1a using the eddy current flaw detection probe 11a based on the eddy current flaw detection method. Specifically, the eddy current flaw detection probe 11a includes an excitation coil that generates an eddy current by applying an alternating magnetic field to the rail surface 1a, and a detection coil that detects a magnetic field due to the eddy current generated on the rail surface 1a by the excitation coil. It has. The magnitude of the eddy current generated on the rail surface 1a by the exciting coil changes depending on the presence / absence, distribution, etc. of the material abnormal portion of the rail surface 1a, so that the change in the magnitude of the eddy current is detected as the impedance change of the detection coil. By doing so, the material abnormality part of the rail surface 1a can be determined. The signal detected by the eddy current flaw detection probe 11 a is converted into digital data by the eddy current flaw detection device 11 and then transmitted to the data recorder 15. As long as the eddy current flaw detection probe 11a and the eddy current flaw detection apparatus 11 can exhibit such a function, their specific configurations are not particularly limited, and commercially available materials suitable for material determination may be used. .

  FIG. 2 is a schematic plan view of the flaw detection inspection auxiliary tool 20 for explaining the operation of the flaw detection inspection auxiliary tool 20. In the present embodiment, the flaw detection inspection auxiliary tool 20 includes an outer guide frame 21, an inner guide bar 23, and a probe holding device 25.

  The outer guide frame 21 is configured by assembling a plurality of frame members 21a into a rectangular shape. The outer guide frame 21 is arranged so that the inspection target area of the rail surface 1a during the eddy current inspection is surrounded by the outer guide frame 21, and is fixed to the rail 1 or another member (not shown). .

  Two inner guide bars 23 are provided in the outer guide frame 21 so as to form a cross shape, and are slidably supported by the frame member 21a of the outer guide frame 21 via the slide portions 23a on both sides thereof. . A motor is built in the slide portion 23a on one end side of each inner guide bar 23, and the inner guide bar 23 is guided to the outer guide frame 21 through the slide portion 23a by driving of the motor, and the rail longitudinal direction. In addition, the rail surface 1a to be inspected is slidable in a direction A perpendicular to the rail longitudinal direction.

  The probe holding device 25 is provided in the vicinity of the intersection portion 23b of the two inner guide bars 23 having a cross shape, and is slidably supported by the inner guide bars 23 via the slide portions 23a. . When the inner guide bar 23 is guided to the outer guide frame 21 by driving the motor and slides in the directions P1 and P2 shown in FIG. 2A, for example, the probe holding device 25 is as shown in FIG. In addition, the guide is guided to the inner guide bar 23 via the slide portion 25a, and slides in a direction corresponding to the slide of each inner slide bar 23.

  The probe holding device 25 can hold the eddy current flaw detection probe 11a while being pressed against the rail surface 1a. The probe holding device 25 is preferably configured to be able to press the eddy current flaw detection probe 11a via air pressure or spring pressure so that the probe can be stably pressed against the rail surface 1a. The probe holding device 25 preferably has a position adjusting function capable of pressing the eddy current flaw detection probe 11a perpendicularly to the rail surface 1a. In addition, the probe holding device 25 preferably has a probe height adjustment mechanism that can drive the eddy current flaw detection probe 11a on both sides in the normal direction with respect to the rail surface 1a by incorporating an air cylinder or the like, for example.

  With this configuration, the flaw detection inspection auxiliary tool 20 can freely move the eddy current flaw detection probe 11a in the rail longitudinal direction and the direction A within the range to be inspected on the rail surface 1a while holding the eddy current flaw detection probe 11a. It is possible to move to. As long as such a function can be exhibited, the flaw detection inspection aid 20 is not particularly limited to the above-described configuration.

  The external control device 13 sets the moving speed and moving range of the inner guide bar 23 in the rail longitudinal direction by the motor, and further sets the moving pitch amount and moving range of the inner guide bar 23 in the rail width direction by the motor. The moving condition of the flaw detection probe 11a can be controlled. The external control device 13 may be operable based on control by the material abnormality portion determination device 17.

  The data recorder 15 records the signal data output from the eddy current flaw detection device 11 by the eddy current flaw inspection, and the recorded signal data is transmitted to the material abnormality portion determination device 17. A commercially available data recorder 15 may be used, and the specific configuration is not particularly limited.

  The material abnormality portion determination device 17 determines the material abnormality portion with respect to the inspection target range of the rail surface 1a by analyzing the signal data as digital data transmitted from the data recorder 15 based on an analysis method described later. Is. The material abnormality portion determination device 17 is, for example, a personal computer (PC) having hardware such as a RAM (Random Access Memory) and a display in addition to a CPU (Central Processing Unit) that executes a program for performing an analysis method described later. ) And the like.

  Next, the detail of the nondestructive inspection method of the steel rail for tracks to which this invention is applied is demonstrated.

  The present invention is applied to detect an abnormal material portion occurring on the rail surface 1a of the rail steel rail 1 as shown in FIGS. 3 (a), 3 (b), and 4. FIG. In the following, the range to be inspected of the rail surface 1a is as shown in FIG. 4 in the rail surface 1a of the rail head portion 1c and the rail leg portion 1e that are in contact with the electrode 33 used during flash butt welding as shown in FIG. It is assumed that the range is S0 as shown in FIG.

  In the present invention, the material abnormal portion to be determined is a hardness that is partly due to local heating and rapid cooling of the rail 1 when the rail 1 is flash-butt welded, as compared with the peripheral portion. A locally extremely high part.

  The size of the material abnormal portion is about several millimeters when it is small. Further, since the commercially available eddy current flaw detection probe 11a used for the eddy current flaw inspection has a probe diameter of about several millimeters, the eddy current flaw detection probe 11a is generated within a range to be inspected only by scanning in one direction. It is impossible to detect an abnormal material portion without omission. Therefore, in the present invention, at the time of eddy current flaw inspection, the eddy current flaw detection probe 11a is moved a plurality of times in both directions of the rail longitudinal direction and the direction A perpendicular to the rail longitudinal direction on the rail surface 1a to be inspected. Thus, the eddy current flaw inspection is performed over almost the entire range to be inspected of the rail surface 1a. In order to realize this, the present invention uses the above-described flaw detection inspection auxiliary tool 20 so as to be freely movable in both the longitudinal direction of the rail and the direction A.

  Here, as a scanning procedure of the eddy current flaw detection probe 11a capable of efficiently executing the eddy current flaw inspection performed over almost the entire range to be inspected of the rail surface 1a, for example, the following two kinds of procedures can be considered. .

  As shown in FIG. 5, in the first scanning procedure, a linear eddy current flaw detection inspection is performed by scanning the eddy current flaw detection probe 11a with the inspection direction as the rail longitudinal direction, and then the rail surface 1a is orthogonal to the rail longitudinal direction. The operation of moving a predetermined pitch in the rail width direction, which is the direction in which it is performed, is repeated. In the second scanning procedure, as shown in FIG. 6, the eddy current flaw detection probe 11a is scanned with the inspection direction as the rail width direction to perform a straight eddy current flaw inspection, and then moved by a predetermined pitch in the rail longitudinal direction. Is repeated.

  Here, as shown in FIG. 6, when a linear eddy current flaw inspection was performed with the inspection direction as the rail width direction, a signal as shown in FIG. 7A was detected. Further, as shown in FIG. 5, when a linear eddy current flaw inspection was performed with the inspection direction as the rail longitudinal direction, a signal as shown in FIG. 7B was detected. In any case, the range to be inspected of the rail surface 1a is the one having no material abnormality portion, surface, or flaw defect on the inner surface.

  When a linear eddy current flaw inspection is performed along the rail width direction, as shown in FIG. 7 (a), the signal level at the center portion in the rail width direction is present even though there is no material abnormal portion on the rail surface 1a. As a result, the signal level increased toward the end in the rail width direction. In this way, when the signal level is greatly disturbed depending on the inspection position, it becomes difficult to determine the material abnormality portion by an analysis method as described later, and it can be said that the second scanning procedure described above is not preferable. .

  On the other hand, when a linear eddy current flaw inspection is performed along the rail longitudinal direction, as shown in FIG. 7B, in any part of the rail surface 1a where there is no material abnormal portion or the like, in any part of the rail longitudinal direction. Even a stable signal level could be obtained.

  It is considered that this difference is greatly influenced by the cross-sectional shape orthogonal to the rail longitudinal direction of the rail 1 as shown in FIG. That is, as shown in FIG. 3B, the rail 1 is formed such that the end portion in the rail width direction is thin and the thickness in the center portion in the rail width direction is extremely thick. When the linear eddy current flaw inspection along the rail width direction as shown in FIG. 4 is performed, the thickness of the rail 1 in the normal direction with respect to the inspection surface varies depending on the inspection position. On the other hand, as shown in FIG. 3A, the rail 1 is formed with a constant thickness over a long range in the rail longitudinal direction. When a straight eddy current flaw inspection is performed, the thickness of the rail 1 in the normal direction relative to the inspection surface is constant regardless of the inspection position.

  In general, in the eddy current flaw detection method, it is known that the test frequency passed through the exciting coil of the eddy current flaw detection probe 11a is changed according to the position in the depth direction where the inspection object is estimated to exist. For example, when it is desired to inspect the rail surface 1a, the test frequency is relatively high. Conversely, when it is desired to inspect a position away from the rail surface 1a in the depth direction, the test frequency is relatively low.

  However, it is known about the signal level disturbance caused by the inspection position as shown in FIG. 7 (a) and the countermeasures to be taken when the eddy current flaw detection inspection is performed linearly in the direction in which the thickness changes for the specimens having different thicknesses. It is not done. Therefore, in order to solve the problem caused by the disturbance of the signal level due to such an inspection position, in the present invention, when performing a linear eddy current flaw inspection by the eddy current flaw detection probe 11a, as shown in FIG. Thus, the eddy current flaw detection probe 11a is scanned along the rail longitudinal direction.

  Further, in the present invention, in order to realize the eddy current flaw detection inspection performed over almost the entire range to be inspected of the rail surface 1a, the processing method of the signal output from the eddy current flaw detection probe 11a is also characterized. ing.

  FIG. 8A is a schematic diagram showing a signal detected when the eddy current flaw inspection is performed linearly in the rail longitudinal direction along the direction R1 in FIG. 5, and FIG. It is a schematic diagram which shows the signal detected when the linear eddy current flaw detection test | inspection is performed in the rail longitudinal direction along direction R2. In any of the inspections, the range to be inspected on the rail surface 1a is an object that does not have a defect in the material, the surface, or the inner surface.

  As described above, when the eddy current flaw detection probe 11a is scanned in the longitudinal direction of the rail and the linear eddy current flaw inspection is performed, the position to be scanned in the longitudinal direction of the rail is the central portion in the rail width direction and the end portion in the rail width direction. In both cases, the detected signal level was a stable value. However, the absolute value of the detected signal level is greatly different depending on the position to be scanned in the rail longitudinal direction even when there is no material abnormal part or the like.

  The reason why the absolute value of the detected signal level differs depending on the inspection position is the same as described above, and the thickness of the rail 1 in the normal direction relative to the inspection surface varies greatly depending on the inspection position. Seems to have influenced. When the signal level is disturbed depending on the inspection position as described above, it is difficult to determine a material abnormality portion or the like as described above.

  Therefore, in the present invention, the eddy current flaw detection probe 11a is moved along the rail longitudinal direction after the eddy current flaw detection probe 11a is moved in the rail width direction which is a direction orthogonal to the rail longitudinal direction on the rail surface 1a to be inspected. Before the scanning, the zero point of the signal level output from the eddy current flaw detection probe 11a is adjusted. As a result, a substantially constant signal level can be obtained regardless of the position in the rail width direction where the linear eddy current flaw detection is performed, thereby using the first scanning procedure as described above. Even in such a case, it is possible to easily determine the material abnormality portion by an analysis method described later.

  In the above description, the case where the range to be inspected is the rail head surface 1a of the rail head portion 1c and the rail leg portion 1e has been described, but during flash butt welding, as indicated by a two-dot chain line in FIG. The electrode 33 may be brought into contact with the rail surfaces 1a on both sides of the rail body 1d, and the rail surfaces 1a on both sides of the rail body 1d may be in a range to be inspected. Even in this case, the thickness of the rail 1 in the normal direction with respect to the inspection surface is slightly different between the center in the height direction of the rail body 1d and the portion near the rail head 1c and the rail leg 1e of the rail body 1d. ing. For this reason, a stable signal level cannot be obtained when a linear eddy current flaw inspection is performed in the rail height direction, or the absolute value of the signal level detected during the linear eddy current flaw inspection performed in the rail longitudinal direction is the rail height. Different problems occur depending on the position in the vertical direction, and as described above, it is difficult to determine the material abnormality portion.

  For this reason, in the present invention, when the rail surfaces 1a on both sides of the rail body 1d are to be inspected, a linear eddy current flaw inspection is first performed along the rail longitudinal direction, and then the inspection target is performed. The eddy current flaw detection probe 11a is moved in the rail height direction which is a direction orthogonal to the rail longitudinal direction on the rail surface 1a, and then the zero point adjustment of the signal level output from the eddy current flaw detection probe 11a is performed. Thus, the above-mentioned problems are solved.

  The present invention has been devised based on the above concept, and the procedure will be further described below.

  First, as shown in FIG. 5, the corner portion 1f on one end side of the rail longitudinal direction within the range to be inspected of the rail surface 1a and the direction A perpendicular to the rail longitudinal direction on the rail surface 1a to be inspected. Above, the eddy current flaw detection probe 11a is arranged using the flaw detection inspection auxiliary tool 20. Subsequently, a longitudinal flaw detection inspection step is performed in which the eddy current flaw detection probe 11a is scanned along the longitudinal direction of the rail surface 1a to perform a linear eddy current flaw inspection. Subsequently, a probe moving step for moving the eddy current flaw detection probe 11a in the direction A is executed. Subsequently, a zero point adjustment step for adjusting the zero point of the signal level output from the eddy current flaw detection probe 11a is executed.

  A series of steps from the longitudinal direction flaw detection step to the zero point adjustment step is performed so that almost the entire range to be inspected on the rail surface 1a is inspected almost entirely in the eddy current flaw inspection. Iterate over the range. The longitudinal flaw detection step here is performed along the solid line arrow in FIG. 5, the probe moving step is performed along the dotted line arrow in FIG. 5, and the zero point adjustment step is in FIG. This is performed at the position indicated by the circle.

  The repetition of a series of steps from the longitudinal direction flaw detection step to the zero point adjustment step executed here is performed, for example, as shown in FIG. 5, every time a series of steps are performed, the eddy current flaw detection probe in the longitudinal direction flaw detection step. There is a procedure in which the scanning direction of 11a is repeated while being reversed. In addition to this, as shown in FIG. 9A, the probe moving step is performed so that the scanning start position of the longitudinal flaw detection step is aligned on the substantially same straight line in the direction A every time a series of steps are performed. You may make it adjust the moving direction of. In addition to this, the movement amount of the eddy current flaw detection probe 11a in the probe moving step every time a series of steps is performed is not set to a predetermined pitch as shown in FIG. 5, but a series of steps as shown in FIG. 9B. You may make it change whenever it performs. Incidentally, in the scanning procedure shown in FIG. 9B, the moving trajectory by the eddy current flaw detection probe 11a is repeated from the longitudinal direction flaw detection step to the zero point adjustment step so as to draw a spiral shape. As described above, the scanning procedure of the eddy current flaw detection probe 11a in the present invention is not particularly limited as long as almost the entire range to be inspected can be eddy current flaw inspection.

  When the above-described series of steps are repeated, the rail surface 1a has a curvature depending on the inspection position. Therefore, there is a case where the eddy current flaw detection probe 11a is separated from the rail surface 1a every time the probe moving step is executed. . For this reason, it is preferable to drive the eddy current flaw detection probe 11a to be pressed against the rail surface 1a with a constant pressure by the probe height adjusting mechanism every time the longitudinal flaw detection inspection step is started. Even if there is a curvature, the inspection can be executed stably.

  The zero point adjustment step performed here may be performed by the external control device 13 after the external control device 13 is connected to the eddy current flaw detection device 11 or the external control device 13 executes the zero point adjustment step. If it is difficult to do so, the material abnormality portion determination device 17 may perform the determination. When performing the zero point adjustment step, for example, the signal level at the start of the longitudinal flaw detection inspection step is corrected to zero, and all signal levels detected until the next width direction movement step is performed with the correction amount. What is necessary is just to perform the process to correct. In addition, the impedance of the variable resistor in the bridge circuit generally used in the eddy current flaw detection method may be changed every time the zero point adjustment step is performed, so that the bridge circuit is in an equilibrium state. Any zero point adjusting means may be applied.

  A signal detected from the eddy current flaw detection probe 11 a to the eddy current flaw detection device 11 is converted into digital data, and then recorded in the data recorder 15. After that, the digital data is transmitted to the material abnormality portion determination device 17 via the data recorder 15. To be recorded.

  The following analysis process is performed on the signal data recorded by the material abnormality portion determination device 17. First, as shown in FIG. 10, a threshold value V1 for discriminating a material abnormality portion is set in advance for the detected signal level. Then, the signal level detected by the eddy current flaw detection probe 11a is compared with the threshold value V1, and it is determined that there is a material abnormality portion at a part where the signal level exceeding the threshold value V1 is detected. In the example illustrated in FIG. 10, it is determined that there is a material abnormality portion in a portion where the signal level of the range Ra is detected.

  The information on the presence / absence of the material abnormal portion determined based on the signal level is associated with the position information of the eddy current flaw detection probe 11a within the range to be inspected, and thereby, the material abnormal portion within the range to be inspected. Two-dimensional distribution information indicating the generation range and size can be obtained.

  The threshold value V1 set here is obtained based on the signal level actually detected at the time of the eddy current flaw inspection of the abnormal material portion by performing eddy current flaw inspection using a plurality of samples having the material abnormal portion in advance. do it. Here, the threshold value V1 obtained from the sample may be stored in advance as a table value in the material abnormality portion determination device 17.

  After the inspection within the range to be inspected of the rail surface 1a, the inspection result includes the presence / absence of an abnormal material portion, if there is, two-dimensional distribution information indicating the generation range and size, and the number, etc. As shown in FIG. 11, the screen may be output to the display 17 a or the like of the material abnormality portion determination device 17 or may be stored in the material abnormality portion determination device 17 or the like. At this time, the inspection date and time, the inspection object identification number, and the like may be output to the screen and stored. 11, the electrode 33 is in contact with the rail 1 in FIG. 3A, and the rail head 1 c and the rail leg 1 e of the left rail 1 </ b> A and the right rail 1 </ b> B in the figure. The inspection results after inspecting a total of four places on the surface 1a are shown.

  In addition, from the viewpoint of alerting the inspector and enhancing safety, the material abnormality portion determination device 17 or other device has a function of simultaneously outputting an alarm display and an alarm sound when it is determined that there is a material abnormality portion. Preferably. In addition, in order to accumulate and search information about the inspection results of these material abnormal portions, it is preferable that the material abnormal portion determination device 17 and other devices have these functions.

  According to such a method for determining a material abnormality portion of the rail surface 1a according to the present invention, the range to be inspected at the time of the eddy current flaw inspection is set as a two-dimensional range of the rail surface 1a and is generated within this range. It is possible to automatically and accurately determine the material abnormality portion to be performed without visual confirmation. For this reason, the quality control of the steel rail 1 for track becomes easy, and it is possible to prevent the occurrence of a serious accident due to the breakage starting from the material abnormal part which is a concern when a repeated load is applied during its use. It becomes possible. In addition, it is possible to grasp the two-dimensional distribution information indicating the occurrence range and size of the material abnormality portion that has occurred on the rail surface 1a, and furthermore, it is possible to easily collect, store, and accumulate information regarding these material abnormality portions. It becomes.

  Next, in order to describe the preferable range of the range to be inspected when the material abnormal portion determination method according to the present invention is applied, first, how flash butt welding is performed will be described.

  FIG. 3A is a perspective view showing a state when the rail longitudinal ends of the two rails 1 are flash-butt welded, and FIG. 3B is a front sectional view thereof. FIG. 4 is a perspective view showing a state of the rail 1 after the flash butt welding is completed.

  When flash butt welding the two rails 1, first, as shown in FIG. 3A, the rails 1 are arranged so that the end portions in the longitudinal direction of the rails abut each other, and then the rails 1 are sandwiched. The two electrodes 33 are pressed from opposite directions.

  Subsequently, under the control of the power supply device 31 connected to each electrode 33, the rail longitudinal ends of the two rails 33 are brought into close contact with each other and lightly brought into contact with each other, and a large current is passed between the rails 1. A flash is generated between the directional ends to heat the rail longitudinal ends. After the rail longitudinal ends are contacted and heated to some extent to sufficiently melt the rail longitudinal ends, the other rail 1 is pressed against one rail 1 to complete flash butt welding. The welded portion 3 is formed between the end portions in the rail longitudinal direction.

  Here, when the rail 1 is flash-butt welded as in this embodiment, as described above, an abnormal material portion is generated due to partial current concentration or discharge between the electrode 33 and the rail 1. there's a possibility that. For this reason, the range to be inspected may be a range including at least a range S0 where the electrode 33 and the rail 1 are in contact with each other.

  Here, as shown in FIG. 4, the range to be inspected is a range Sa1 in which the electrode 33 and the rail 1 are in contact with each other in the rail longitudinal direction Sa, and further 10 mm to 30 mm further toward the welded portion 3 side. It is preferable to combine the following range Sa2 up to the site with a space. The reason why the range Sa2 is set to 10 mm or more from the range Sa1 to the welded portion 3 side is that discharge may occur between the welded portion side end surface 33a of the electrode 33 and the rail surface 1a, and the range to be inspected is the rail longitudinal direction. This is because the material abnormal part generated by such a discharge may be overlooked if it is only in the range Sa1. The range Sa2 is set to 30 mm or less from the range Sa1 to the welded part 3 side. Generally, the distance from the electrode 33 to the welded part 3 is about 50 mm to 100 mm, but from the range Sa1 to the welded part 3 side is 30 mm. This is because it is difficult to distinguish between a region where the material inevitably changes due to the thermal effect of the welded portion 3 and a material abnormal portion due to discharge and current concentration if the temperature is too close to the welded portion 3. In addition, the range Sb in the direction A in the range to be inspected in this case may be a range in which the electrode 33 and the rail 1 are in contact with each other.

  By adjusting the range to be inspected in this way, it is possible to reliably detect most of the material abnormal portions that may occur when the rail 1 is flash-butt welded. Further, by adjusting the range to be inspected in this way, the range to be inspected can be prevented from becoming excessively wide, and the inspection time can be shortened.

  Further, at the time of flash butt welding, the electrode 33 is pressed against each of the rails 1 against the rail surface 1a of the rail head portion 1c and the rail leg portion 1e or the rail surface 1a on both sides of the rail body portion 1d. It will be. For this reason, it is preferable to make all the places which pressed these electrodes 33 into the range of a test object.

  Further, when scanning the eddy current flaw detection probe 11a along the rail longitudinal direction of the rail surface 1a, it is preferable to scan at a constant speed in order to obtain stable detection capability and improve detection accuracy.

  The moving speed of the eddy current flaw detection probe 11a is preferably about 10 to 200 mm / sec, although it depends on the detection ability of the eddy current flaw detection device 11 and the eddy current flaw detection probe 11a and the roughness of the rail surface 1a. Further, when the eddy current flaw detection probe 11a is scanned by the scanning procedure as shown in FIG. 5, the movement pitch in the direction A of the eddy current flaw detection probe 11a at each probe movement step is preferably about 3 to 20 mm.

  Next, the effect of this invention is demonstrated with the Examples 1-3. In addition, the conditions used in Examples 1 to 3 described below are examples, and the present invention is not limited to these conditions.

  In Example 1, a nondestructive inspection was performed on the rail surface 1a under the conditions described below. As the inspection object by the nondestructive inspection, a rail that can be confirmed by visual confirmation that there is a material abnormality portion at least in the electrode contact range after flash butt welding is used. In Example 1, the inspection was performed under other conditions shown in Table 1 below. The test results are evaluated based on whether or not all the abnormal material portions within the electrode contact range can be detected, and overdetection that detects other than the abnormal material portions confirmed by visual confirmation does not occur. did.

  In Table 1, when the “inspection direction” is “rail longitudinal direction”, the eddy current flaw detection probe 11a is scanned by the scanning procedure as shown in FIG. The eddy current flaw detection probe 11a is scanned by a scanning procedure as shown in FIG. The range to be inspected at the time of the eddy current flaw inspection is set to a range in which a range Sa2 of 0 to 100 mm is combined with the electrode contact range of the range S0 as shown in FIG. Further, the material abnormal portion is determined by executing the above-described analysis processing on the signal data detected from the eddy current flaw detection probe 11a.

  The test results of Example 1 will be described. Test No. In A-2, since the eddy current flaw detection inspection is performed with the inspection direction as the rail width direction, the signal level fluctuates greatly regardless of the presence or absence of the material abnormal portion, and the material abnormal portion cannot be detected. there were. Test No. In A-3, since the zero point adjustment step was not performed between the end of the probe moving step and before the start of the longitudinal flaw detection inspection step, the signal level is large depending on the inspection position where the linear eddy current flaw inspection is performed in the rail longitudinal direction. As a result, it was impossible to detect an abnormal material portion.

  In contrast, test no. Since A-1 satisfies the above-described conditions for the present invention, it was possible to detect all of the material abnormal portions within the electrode contact range.

  Next, Example 2 will be described. In the second embodiment, unlike the conditions in the first embodiment, as an inspection object by the nondestructive inspection, there may be a material abnormal portion on the weld side from the electrode contact range in addition to the electrode contact range after flash butt welding. A rail that can be confirmed by visual confirmation was used. In Example 2, the inspection was performed under other conditions shown in Table 2 below. The test result can detect all of the electrode contact area and the material abnormal part on the weld side from this, and whether or not there is an overdetection that detects other than the material abnormal part confirmed by visual confirmation. It was decided to evaluate by.

  The test results of Example 2 will be described. Test No. In B-2, since the range to be inspected was only the range S0 as shown in FIG. 4, it was impossible to detect the material abnormal portion on the welded portion side from the electrode contact range. Test No. In B-3, because the range to be inspected is the electrode contact range of the range S0 as shown in FIG. In addition to the material abnormal portion that has occurred, over-detection has occurred in which a portion where the material inevitably changes due to the heat effect of the welded portion 3 is also detected.

  In contrast, test no. Since B-1 satisfies the above-described conditions for the present invention, it is possible to detect all of the electrode contact range and the material abnormal portion on the welded portion side without overdetection. there were.

  Next, Example 3 will be described. In Example 3, the nondestructive inspection was performed under the same conditions as in Example 1 except for the conditions shown in Table 3 below. The test results were evaluated under the same conditions as in Example 1.

  The test results of Example 3 will be described. Test No. In C-2, since the moving speed of the eddy current flaw detection probe at the time of performing the linear eddy current flaw inspection is not uniform, the signal level becomes unstable, and a part of the abnormal material portion is detected. Over-detection is detected even if there is a material abnormality portion even in a region where there is no material abnormality portion.

  In contrast, test no. Since C-1 satisfies the above-described conditions for the present invention, it was possible to detect all of the abnormal material portions in the electrode contact range without overdetection.

  The nondestructive inspection method for rail steel rails according to the present invention can be used, for example, at the time of inspection of material abnormalities occurring on the rail surface in a welding factory or field welding site where flash butt welding of rail steel rails is performed. it can.

1: Rail steel rail 3: Welded part 10: Nondestructive inspection system 11: Eddy current flaw detector 11a: Eddy current flaw probe 13: External control device 15: Data recorder 17: Material abnormal part judgment device 20: Flaw detection inspection tool 21 : Outer guide frame 23: Inner guide bar 23a: Slide part 25: Probe holding device 25a: Slide part 33: Electrode

Claims (3)

In a nondestructive inspection method for rails for rails for detecting abnormalities on the surface of a plurality of rails for rails connected in series by flash butt welding based on a signal output from an eddy current flaw detection probe,
A linear eddy current flaw inspection is performed by scanning the eddy current flaw detection probe along the rail longitudinal direction of the rail surface, and then the eddy current flaw detection probe is moved in a direction perpendicular to the rail longitudinal direction on the rail surface. Thereafter, until the zero level adjustment of the signal level output from the eddy current flaw detection probe is performed repeatedly in a predetermined range on the rail surface, the eddy current flaw inspection is performed for the predetermined range. Non-destructive inspection method for steel rails for tracks. The predetermined range to be subjected to the eddy current flaw inspection, the range in which the electrode and the rail are in contact with each other in the flash butt welding in the longitudinal direction of the rail, and the range from this to the part further spaced by 10 mm or more and 30 mm or less toward the welded portion The steel rail for a track according to claim 1, wherein a direction perpendicular to the longitudinal direction of the rail on the surface of the rail is a range in which the electrode and the rail are in contact with each other at the time of flash butt welding. Non-destructive inspection method. The method for nondestructive inspection of a steel rail for a track according to claim 1 or 2, wherein the moving speed of the eddy current flaw detection probe during scanning along the rail longitudinal direction is made equal.

Images