JP4193181B2 - Magnetizer for magnetic testing of steel pipes - Google Patents

Description

  The present invention relates to a magnetizing device for magnetic flaw detection (magnetic particle flaw detection, etc.) of a steel pipe, and in particular, it is possible to magnetize so that any defect extending in each direction such as the axial direction or the circumferential direction of a steel pipe can be detected with high accuracy. The present invention relates to a magnetizing apparatus.

  2. Description of the Related Art Conventionally, there is known a magnetic particle flaw detection method for detecting defects generated on the inner and outer surfaces of a steel pipe by magnetizing a steel pipe (particularly, a pipe end) that is a magnetic body. More specifically, in the magnetic particle flaw detection method, if the magnetic powder liquid is sprayed on the magnetized steel pipe, the magnetic powder is magnetized and agglomerated and adsorbed by the leakage magnetic flux generated at the defect occurrence site. This is a flaw detection method for detecting defects by visual observation.

  Here, the leakage magnetic flux is remarkably generated when the defect extends in a direction perpendicular to the direction of the magnetic flux generated by the magnetization of the steel pipe. On the other hand, as defects generated on the inner and outer surfaces of the steel pipe, there are various defects extending in each direction such as an axial direction and a circumferential direction of the steel pipe depending on the generation factor. Therefore, in order to accurately detect any defect in various directions that can occur in the steel pipe, a magnetization method (magnetization apparatus) is adopted in which the magnetic flux is generated substantially uniformly in all directions along the inner and outer surfaces of the steel pipe. Ideally.

  Therefore, for the purpose of generating magnetic flux substantially uniformly in all directions, conventionally, the first coil wound in a spiral shape along the axial direction of the steel pipe, and extending along the axial direction of the steel pipe, and A pair of second coils disposed opposite to each other across the steel pipe along a horizontal axis direction perpendicular to the axial direction of the steel pipe, and electrically connected to each other; and extending along the axial direction of the steel pipe; and A pair of third coils arranged opposite to each other across the steel pipe along the axial direction perpendicular to the axial direction of the steel pipe and the horizontal axis direction, and electrically connected to each other, the first coil, and the second coil And a magnetizing device provided with a three-phase alternating current power supply for supplying alternating current whose phase difference is mutually 120 degrees to each of the 3rd coil is proposed (for example, refer to patent documents 1).

However, when the inventors of the present invention actually tested a steel pipe with artificial defects in various parts and directions using the magnetizing apparatus described in Patent Document 1, a defect extending in a predetermined direction of a predetermined part of the steel pipe. It was found difficult to detect.
Japanese Patent Laid-Open No. 7-103942

  The present invention has been made to solve such problems of the prior art, and can be magnetized so that any defect extending in each direction such as the axial direction or circumferential direction of a steel pipe can be detected with high accuracy. An object of the present invention is to provide a magnetizing device for magnetic flaw detection of a simple steel pipe.

  In order to solve the above-mentioned problems, the inventors of the present invention have made extensive studies and as a result, it is supplied to the first coil, the second coil, and the third coil that a defect extending in a predetermined direction of a predetermined portion of the steel pipe cannot be detected. This is because the magnetic flux due to magnetization does not occur in all directions along the inner and outer surfaces of the steel pipe due to the phase difference between the alternating currents being 120 degrees (for example, paragraph 4 of page 4 of Patent Document 1). I found out.

  More specifically, as shown in FIG. 6, the first coil 11 wound in a spiral shape along the axial direction of the steel pipe P (the depth direction in FIG. 6), and the axial direction of the steel pipe P A pair of second coils 12a and 12b arranged opposite to each other across the steel pipe P along a horizontal axis direction orthogonal to each other, and the steel pipe P along a vertical axis direction orthogonal to the axial direction of the steel pipe P. A phase difference of 120 degrees between the pair of third coils 13a and 13b that are arranged opposite to each other and electrically connected to each other (the phase difference between the first coil 11 and the second coils 12a and 12b is 120 degrees). When an alternating current (amplitude and frequency are the same) having a phase difference of 240 degrees between the first coil 11 and the third coils 13a and 13b is supplied, the magnetic field distribution (the locus of the magnetic field vector) as shown in FIG. Was found to form. Here, FIG. 7 is a view showing a magnetic field (magnetic permeability of the steel pipe P is not considered) distribution formed by the coil arrangement shown in FIG. 6, and (a) shows the second coil 12a and the third coil 13a. A magnetic field distribution formed in a region between the second coil 12b and the third coil 13b (hereinafter referred to as A region as appropriate), (b) is between the second coil 12b and the third coil 13a. The results of calculating the magnetic field distribution formed in the region (hereinafter referred to as B region as appropriate) between the second coil 12a and the third coil 13b (hereinafter referred to as B region as appropriate) are shown. In FIG. 7, the horizontal axis indicates the magnetic field strength along the axial direction (L direction) of the steel pipe P, and the vertical axis indicates the magnetic field strength along the circumferential direction (T direction) of the steel pipe P. Moreover, the point (●) in the graph shown in FIG. 7 indicates the magnetic field strength plotted every time the phase of the alternating current supplied to each coil advances by 20 degrees.

  As shown in FIG. 7, when an alternating current having a phase difference of 120 degrees is supplied to the first coil 11, the second coils 12a and 12b, and the third coils 13a and 13b, the region B is increased as the phase of the alternating current advances. In FIG. 7, an elliptical magnetic field distribution is formed (FIG. 7B), but in the area A, a linear magnetic field distribution is obtained (FIG. 7A). In other words, as the phase of the supplied alternating current advances, the magnetic field vector in the B region follows all directions along the inner and outer surfaces of the steel pipe P, whereas the magnetic field vector in the A region only changes in magnitude. Therefore, it follows only one predetermined direction along the inner and outer surfaces of the steel pipe P. Therefore, in the area A, it is possible to detect a defect extending in a direction perpendicular to the one direction, but the detection ability of the defect extending in the other direction is lowered, and in particular, a defect extending in parallel to the one direction. Will be very difficult to detect. As described above, the result of this numerical calculation substantially coincided with the result of actually testing a steel pipe with an artificial defect, thereby confirming the validity of the analysis by this numerical calculation.

The present invention has been completed based on the knowledge found by the inventors of the present invention described above. That is, the present invention includes a first coil wound in a spiral shape along the axial direction of the steel pipe, and a first direction extending along the axial direction of the steel pipe and orthogonal to the axial direction of the steel pipe. A pair of second coils that are arranged opposite to each other with the steel pipe interposed therebetween and are electrically connected to each other, and extend along the axial direction of the steel pipe, and are further orthogonal to the axial direction of the steel pipe and the first direction. To supply an alternating current to each of the pair of third coils that are disposed opposite to each other across the steel pipe along two directions and are electrically connected to each other, and the first coil, the second coil, and the third coil. A three-phase AC power source, and during the energization time from the three-phase AC power source, rotating the steel pipe at least 90 degrees in the circumferential direction, all the parts of the steel pipe, Magnetic field formed by a magnetizing device Vector in which to provide a magnetic flaw detection magnetizer of the steel pipe, characterized in that it comprises a rotation mechanism for transitioning to the area to follow all along the inner and outer surfaces of the steel pipe.

According to such an invention, since the rotation mechanism for rotating the steel pipe at least 90 ° or more in the circumferential direction is provided during the energization time from the three-phase AC power source, that is, during the magnetization of the steel pipe, the steel pipe is rotated by the rotation mechanism. By doing so, it is possible to make sure that all the portions of the steel pipe make a transition to the aforementioned B region (see FIG. 6) until the magnetization is completed. As described above, in the region B, the magnetic field vector follows all directions along the inner and outer surfaces of the steel pipe (FIG. 7B), so that defects in a direction that cannot be detected in the region A can be detected. As described above, according to the magnetizing apparatus of the present invention, it is possible to magnetize so that any defect extending in each direction such as the axial direction or the circumferential direction of the steel pipe can be detected with high accuracy.

  The second coil according to the present invention is configured by arranging a plurality of metal elongated members extending along the axial direction of the steel pipe in a direction perpendicular to the axial direction, as described in Patent Document 1. It is possible. More specifically, the second coils having the above-described configuration are arranged opposite to each other with the steel pipe interposed therebetween, and the start end portion of the elongated member constituting one second coil and the elongated member constituting the other second coil are arranged. It is possible to employ a configuration in which the terminal portions are sequentially electrically connected. Also, as the second coil, a so-called yoke coil is formed by winding a winding around a yoke extending in the axial direction of the steel pipe, and the windings of the yoke coils arranged opposite to each other with the steel pipe interposed therebetween are electrically connected. A configuration for connection may be employed. Similarly, for the third coil according to the present invention, the configuration described in Patent Document 1 and the configuration using a yoke coil can be employed. Further, as the rotating mechanism according to the present invention, for example, a pair of rotating rollers separated by a distance smaller than the outer diameter of the steel pipe is used, and the rotational force of the rotating roller is transmitted to the steel pipe placed between the rotating rollers. Therefore, it is possible to employ a configuration in which the steel pipe is rotated in the circumferential direction.

  As described above, according to the magnetizing apparatus for magnetic testing according to the present invention, the magnetic field vector generated by the magnetization follows all directions along the inner and outer surfaces of the steel pipe. It is possible to magnetize so that any extending defect can be detected with high accuracy.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a perspective view schematically showing a configuration of a magnetic testing magnetizing apparatus according to an embodiment of the present invention. As shown in FIG. 1, a magnetizing device for magnetic flaw detection (hereinafter, appropriately referred to as a magnetizing device) 1 includes a first coil 11 wound in a spiral shape along the axial direction of a steel pipe P, and an axial direction of the steel pipe P. A pair of second coils 12 a that extend along the first direction (horizontal direction in the present embodiment) perpendicular to the axial direction of the steel pipe P and are opposed to each other with the steel pipe P interposed therebetween and are electrically connected to each other. 12b and extending along the axial direction of the steel pipe P, and opposed to each other across the steel pipe P along the axial direction of the steel pipe P and a second direction (vertical direction in the present embodiment) orthogonal to the first direction. And a pair of third coils 13 electrically connected to each other, and three for supplying alternating currents having a phase difference of 120 degrees to the first coil 11, the second coils 12a and 12b, and the third coils 13a and 13b, respectively. And a phase AC power source 14. Furthermore, the magnetizing apparatus 1 according to the present embodiment adjusts the alternating current output from the three-phase alternating current power supply 14, and supplies the adjusted alternating current to the second coils 12a and 12b and the third coils 13a and 13b. Current adjustment circuit 15 is provided.

  The second coils 12a and 12b according to the present embodiment are configured by arranging a plurality of metal elongated members extending along the axial direction of the steel pipe P in the vertical direction, and each of the elongated coils constituting the second coil 12a. The terminal end portion (end portion on the downstream side in the energization direction) of the member and the start end portion (end portion on the upstream side in the energization direction) of each elongated member constituting the second coil 12b are sequentially electrically connected (connection lines are not shown) ), An elongate member positioned at the end of the second coil 12a (the elongate member positioned lowest in FIG. 1) and an elongate member positioned at the end of the second coil 12b (elongated member positioned uppermost in FIG. 1) ) Is electrically connected to the current adjusting circuit 15 and thus to the three-phase AC power source 14. In the above configuration, when AC power is supplied from the three-phase AC power supply 14, currents in opposite directions are supplied to the second coils 12a and 12b along the axial direction of the steel pipe P. A magnetic field along the direction will be formed.

  The third coils 13a and 13b according to the present embodiment are configured by arranging a plurality of metal elongated members extending along the axial direction of the steel pipe P in the horizontal direction, and each of the elongated coils constituting the third coil 13a. The terminal end portion (end portion on the downstream side in the energization direction) of the member and the start end portion (end portion on the upstream side in the energization direction) of each elongated member constituting the third coil 13b are sequentially electrically connected (connection lines are not shown) ), An elongated member positioned at the end of the third coil 13a (the elongated member positioned closest to the front in FIG. 1), and an elongated member positioned at the end of the third coil 13b (the elongated member positioned deepest in FIG. 1) ) Is electrically connected to the current adjusting circuit 15 and thus to the three-phase AC power source 14. In the above configuration, when AC power is supplied from the three-phase AC power supply 14, currents that are opposite to each other in the axial direction of the steel pipe P are supplied to the third coils 13a and 13b. A magnetic field along the direction will be formed.

  The current adjustment circuit 15 is configured such that the amplitude of the alternating current supplied to one of the second coils 12a and 12b and the third coils 13a and 13b is 0 to 0.4 times the amplitude of the alternating current supplied to the other coil. The AC current output from the three-phase AC power source 14 is adjusted so that the adjusted AC current is supplied to the second coils 12a and 12b and the third coils 13a and 13b. As the current adjustment circuit 15, various known current adjustment circuits can be used.

  FIG. 2 is a diagram showing an example of a magnetic field (the magnetic permeability of the steel pipe P is not considered) distribution (trajectory of the magnetic field vector) formed by the magnetizing apparatus 1 described above, and (a) shows the second coil 12a and The magnetic field distribution formed in the region between the third coil 13a (or between the second coil 12b and the third coil 13b) (hereinafter referred to as A region as appropriate), (b) shows the second coil 12b and the second coil 12b. The results of calculating the magnetic field distribution formed in the region between the three coils 13a (or between the second coil 12a and the third coil 13b) (hereinafter referred to as B region as appropriate) by numerical calculation are shown. Here, the horizontal axis in FIG. 2 indicates the magnetic field strength along the axial direction (L direction) of the steel pipe P, and the vertical axis indicates the magnetic field strength along the circumferential direction (T direction) of the steel pipe P. Further, a point (●) in the graph shown in FIG. 2 indicates the magnetic field strength plotted every time the phase of the supplied alternating current advances by 20 degrees.

  In addition, as a numerical calculation method for obtaining the result shown in FIG. 2, each coil 11, 12 a (12 b) and 13 a (13 b) is formed by each coil alone in consideration of the amplitude and phase of the alternating current flowing through each coil The magnetic field strength at a predetermined location (for example, in the case of the A region, the intermediate point between the second coil 12a and the third coil 13a) is calculated using Bio-Savart's law, and each calculated magnetic field is calculated. A simple method of obtaining the magnetic field intensity at the predetermined location by superimposing the intensity was used.

  The results shown in FIG. 2 are obtained when the current Ix applied to the second coils 12a and 12b is set to 0, and the current Iz supplied to the first coil 11 and the current Iy supplied to the third coils 13a and 12b are the same. The obtained results show that the magnetic field vector follows all directions along the inner and outer surfaces of the steel pipe P in both the A region and the B region. Similarly, the amplitude of the alternating current supplied to one of the second coils 12a, 12b and the third coils 13a, 13b should be 0 to 0.25 times the amplitude of the alternating current supplied to the other coil. For example, the magnetic field vector follows all directions along the inner and outer surfaces of the steel pipe P in both the A region and the B region, and thereby any defects extending in each direction such as the axial direction and the circumferential direction of the steel pipe P are accurate. Magnetization is possible so that it can be detected well.

  In addition, although this embodiment demonstrated the structure which supplies the alternating current after adjustment to each coil 11, 12a (12b) and 13a (13b) via the current adjustment circuit 15 from the three-phase alternating current power supply 14, this book The invention is not limited to this, and a configuration using a phase shifter instead of the current adjustment circuit 15 may be employed.

  More specifically, the three-phase AC power supply 14 is set so that the phase differences of the AC currents supplied to the first coil 11, the second coils 12a and 12b, and the third coils 13a and 13b are not 120 degrees from each other. A configuration comprising a phase shifter for shifting the phase of the alternating current output from, and supplying the alternating current after the phase shift to the first coil 11, the second coils 12a and 12b, and the third coils 13a and 13b. It may be adopted. As such a phase shifter, various known phase shifters can be used.

  FIG. 3 is a diagram showing an example of a magnetic field (the magnetic permeability of the steel pipe P is not considered) distribution (trajectory of the magnetic field vector) formed by the magnetizing device having such a configuration, and (a) is similar to FIG. The magnetic field distribution formed in the A region and (b) show the results of calculating the magnetic field distribution formed in the B region by numerical calculation. The meanings of the horizontal axis, the vertical axis, the point (●), and the numerical calculation method in FIG. 3 are the same as those in FIG.

  The result shown in FIG. 3 is that the phase difference between the current Ix flowing through the second coils 12a and 12b and the current Iy flowing through the third coils 13a and 13b is 90 degrees, and the current Ix flowing through the second coils 12a and 12b. And the phase difference between the current Iz applied to the first coil 11 and the current Iz are 90 degrees, and the magnetic field vector is in all directions along the inner and outer surfaces of the steel pipe P in both the A region and the B region. I found it to follow. Similarly, if the phase shift is performed by the phase shifter so that the phase differences of the alternating currents supplied to the first coil 11, the second coils 12a and 12b, and the third coils 13a and 13b are not 120 degrees, the A region In both the B and B regions, the magnetic field vector follows all directions along the inner and outer surfaces of the steel pipe P, whereby any defect extending in each direction such as the axial direction or the circumferential direction of the steel pipe P can be detected with high accuracy. Can be magnetized.

  It is also possible to adopt a configuration using a frequency conversion circuit instead of the current adjustment circuit 15. More specifically, at least one of the alternating currents supplied to the first coil 11, the second coils 12a and 12b, and the third coils 13a and 13b has a frequency of the remaining alternating current. The frequency of the alternating current output from the three-phase alternating current power supply 14 is converted, and the alternating current after the frequency conversion is supplied to the first coil 11, the second coils 12a and 12b, and the third coils 13a and 13b. A configuration including a frequency conversion circuit for the purpose may be employed. As such a frequency conversion circuit, various known frequency conversion circuits can be used.

  FIG. 4 is a diagram showing an example of a magnetic field (the magnetic permeability of the steel pipe P is not considered) distribution (trajectory of the magnetic field vector) formed by the magnetizing device having such a configuration, and (a) is similar to FIG. The magnetic field distribution formed in the A region and (b) show the results of calculating the magnetic field distribution formed in the B region by numerical calculation. The meanings of the horizontal axis, the vertical axis, the point (●), and the numerical calculation method in FIG. 4 are the same as those in FIG.

  The result shown in FIG. 4 is that the frequency of the alternating current supplied to the first coil 11 is 0.95 times the frequency of the alternating current supplied to the second coils 12a and 12b and the third coils 13a and 13b, respectively. It was found that the magnetic field vector followed all directions along the inner and outer surfaces of the steel pipe P in both the A region and the B region. Similarly, the frequency of at least one alternating current out of the alternating currents supplied to the first coil 11, the second coils 12a and 12b, and the third coils 13a and 13b is different from the frequency of the remaining alternating current. If the frequency conversion is performed by the frequency conversion circuit, the magnetic field vector follows all directions along the inner and outer surfaces of the steel pipe P in both the A region and the B region, and thereby, in each direction such as the axial direction and the circumferential direction of the steel pipe P. It is possible to magnetize so that any extending defect can be detected with high accuracy.

  Further, the current adjusting circuit 15 is not provided, and the AC current output from the three-phase AC power supply 14 is directly supplied to the coils 11, 12a, 12b, 13a, and 13b, and the rotation for rotating the steel pipe P in the circumferential direction. It is also possible to employ a configuration including a mechanism. If it demonstrates more concretely, you may employ | adopt the structure provided with the rotation mechanism for rotating the steel pipe P at least 90 degrees or more to the circumferential direction during the electricity supply time from the three-phase alternating current power supply 14. FIG. As the rotating mechanism, for example, a pair of rotating rollers separated by a distance smaller than the outer diameter of the steel pipe P is used, and the rotating force of the rotating roller is transmitted by placing the steel pipe P between the rotating rollers. A configuration in which the steel pipe P is rotated in the circumferential direction may be employed.

  According to the magnetizing device having such a configuration, during the energization time from the three-phase AC power supply 14 (that is, during the magnetization of the steel pipe P), the steel pipe P is rotated at least 90 ° or more in the circumferential direction by the rotation mechanism, so In the meantime, all the parts of the steel pipe P will surely transition to the B region (see FIGS. 6 and 7B) in which the magnetic field vector follows all directions along the inner and outer surfaces of the steel pipe P. Magnetization is possible so that any defect extending in each direction such as the axial direction or circumferential direction of the steel pipe P can be detected with high accuracy.

  Further, the second coils 12a and 12b and the third coils 13a and 13b according to the present embodiment are provided by arranging a plurality of metal elongated members extending along the axial direction of the steel pipe P in a direction perpendicular to the axial direction. However, the present invention is not limited to this. As shown in FIG. 5, the second coil 12a, 12b and the third coil 13a, 13b are used as the axial direction of the steel pipe P (perpendicular to the plane of FIG. 5). A so-called yoke coil is formed by winding a winding C around a yoke Y extending along a certain direction), and the windings of the yoke coils arranged opposite to each other with the steel pipe P interposed therebetween are electrically connected (yoke coil). It is also possible to adopt a configuration in which 12a and 12b are connected and yoke coils 13a and 13b are connected.

FIG. 1 is a perspective view schematically showing a configuration of a magnetic testing magnetizing apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of a magnetic field distribution formed by the magnetic flaw detector for magnetic testing according to one embodiment of the present invention. FIG. 3 is a diagram showing an example of a magnetic field distribution formed by a magnetic flaw detection magnetizing apparatus according to another embodiment of the present invention. FIG. 4 is a diagram showing an example of a magnetic field distribution formed by a magnetic flaw detection magnetizing apparatus according to another embodiment of the present invention. FIG. 5 is a longitudinal sectional view schematically showing the configuration of a coil used in a magnetic flaw detection magnetizing apparatus according to another embodiment of the present invention. FIG. 6 is a longitudinal sectional view schematically showing an arrangement configuration of coils used in a conventional magnetic flaw detector. FIG. 7 is a diagram showing a magnetic field distribution formed by a conventional magnetizing device for magnetic flaw detection.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Magnetizing apparatus for magnetic flaw detection 11 ... 1st coil 12a, 12b ... 2nd coil 13a, 13b ... 3rd coil 14 ... Three-phase alternating current power supply 15 ... Current adjustment circuit P ... Steel pipes

Claims (1)

A first coil wound spirally along the axial direction of the steel pipe;
A pair of second coils that extend along the axial direction of the steel pipe and are opposed to each other across the steel pipe along a first direction orthogonal to the axial direction of the steel pipe, and are electrically connected to each other;
A pair of first electrodes that extend along the axial direction of the steel pipe and that are opposed to each other across the steel pipe along a second direction orthogonal to the axial direction of the steel pipe and the first direction, and are electrically connected to each other. 3 coils,
A magnetizing device comprising a three-phase AC power source for supplying an AC current to each of the first coil, the second coil, and the third coil;
During the energization time from the three-phase AC power source, the steel pipe is rotated at least 90 ° in the circumferential direction, and a magnetic field vector formed by the magnetizing device is applied to all the parts of the steel pipe on the inner and outer surfaces of the steel pipe. A magnetizing device for magnetic flaw detection of a steel pipe, comprising a rotation mechanism for making a transition to a region that follows all directions along .

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