JPH0720593Y2 - Steel tube end magnetizing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a steel pipe end magnetizing device used for magnetic particle flaw detection in all directions of the inner and outer surfaces of a steel pipe end portion.

[Prior Art] Usually, a pipe end portion of a steel pipe is a portion that serves as a joint, and is subjected to secondary processing such as screwing and welding to be used for various purposes. For this reason, if there is a defect on the outer surface or the inner surface of the pipe end, damage may occur due to secondary processing, which may lead to a serious accident. Therefore, it is necessary to detect defects on the inner surface and the outer surface of the pipe end portion of this type steel pipe, and conventionally, a magnetic particle flaw detection method for flaw detection by uniformly applying magnetic particles to a magnetized flaw-detecting material has been proposed. Was commonly used.

By the way, when the magnetic particle flaw detection method is used, it is necessary to magnetize the flaw-detecting material, that is, the end portion of the steel pipe. As such a steel pipe end magnetizing device, a device for magnetizing the outer surface and the inner surface of the pipe end by separate magnetizing machines is known, as described in JP-A-59-225348. Has been.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional publication, since the range magnetizable by the magnetizing machine is limited to only below the magnetizing yoke, the steel tube or the steel tube is rotated relatively. It is necessary to magnetize the outer surface and the inner surface over the entire circumference, which causes a problem that the device is large and expensive. If the inner diameter of the steel pipe end is small (φ10
(0 mm or less), a magnetizer could not be inserted into the tube and the inner surface could not be magnetized, so flaw detection could not be performed. Furthermore, there are many pipe ends that have large bends, such as the shape called the upset end.Therefore, when rotating the magnetizer or steel pipe relatively, the magnetizer and pipe end Could come into contact with and damage the tube end or damage the magnetizer.

Therefore, the present invention has a simple and inexpensive structure without restrictions on the inner diameter and bending of the pipe end, and without the need to rotate the magnetizer or the steel pipe. An object of the present invention is to provide a magnetizing device for magnetizing a steel pipe end.

[Means for Solving the Problems] The present invention relates to a cylindrical coil wound spirally along the tube axis of a steel pipe, a DC power supply for DC magnetizing the cylindrical coil to generate a DC magnetic field, and the steel pipe. The # type twin coil, which is formed by arranging four ro-type coils wound in parallel with the surface of the pipe in a # type surrounding the steel pipe, and two sets of the ro-type coils facing each other of the # type twin coil. Three-phase AC (2/3)
It is a steel pipe end magnetizing device composed of a three-phase alternating current power source that magnetizes each by a current having a π phase shift to generate a rotating magnetic field.

[Operation] By taking such means, the permeability of the tube end portion of the steel tube inserted in the cylindrical coil is lowered by the DC magnetic field generated by the cylindrical coil, and the tube end is rotated by the rotating magnetic field generated by the # -type twin coil. A longitudinal magnetic field and a transverse magnetic field are generated on the outer surface and the inner surface of the portion, and are magnetized in all directions of the outer surface and the inner surface.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of the apparatus of the present embodiment.
Is a pipe end of a steel pipe as a material to be detected. The apparatus of this embodiment has a cylindrical coil 2 in which the steel pipe 1 is spirally wound along the axial direction of the steel pipe 1 and the steel pipe 1 can be inserted into and removed from the tubular portion of the steel pipe 1.
And a # -type twin coil 7 in which four B-shaped coils 3, 4, 5 and 6 wound in parallel with the surface of the steel pipe 1 are arranged in a # -shape surrounding the steel pipe 1. Has been done.

Then, as shown in FIG. 2, a DC power source 8 for DC-magnetizing the coil 2 is connected to the cylindrical coil 2. In the # -type twin coil 7, a pair of opposing ro-type coils 3 and 5 are magnetized with a u-phase current of a three-phase alternating current, and are arranged 90 degrees apart from the ro-type coils 3 and 5. The other pair of B type coils 4 and 6 facing each other is (2
/ 3) A three-phase AC power supply 9 that is magnetized with a v-phase current deviated by π is connected.

In the apparatus of this embodiment having such a configuration, a direct current flows from the direct current power source 8 to the cylindrical coil 2 in a state where the pipe end of the steel pipe 1 as the flaw detection material is inserted in the cylindrical portion of the cylindrical coil 2. Then, the cylindrical coil 2 is DC magnetized to generate a DC magnetic field, which lowers the magnetic permeability of the tube end.
At this time, the u-phase current and the v-phase current of the (2/3) π-phase of the three-phase AC are shifted to the third pair of the B-type coils 3 and 5, 4 and 6 which are opposed to each other in the # -type twin coil 7. Flowing at the timing shown in the figure, the # type twin coil 7 is rotationally magnetized and
A rotating magnetic field that changes from moment to moment is generated in the direction shown in the figure. As a result, a longitudinal magnetic field and a transverse magnetic field are generated on the outer surface and the inner surface of the tube end, and the tube end is stably magnetized in all directions of the outer surface and the inner surface.

Here, the cylindrical coil 2 is formed with a size of φ180 × 5T,
# Each twin coil 3,4,5,6 that composes the twin coil 7 is 3
Form with T size. Then, insert the steel pipe 1 into which the test piece of A1-15 / 60μ (circular shape) specified in JIS-A0565 is attached to the cylindrical coil 2 on the inner and outer surfaces of the end of the upset end type steel pipe of outer diameter φ75, inner diameter φ43, A direct current of 600 A (ampere) was passed through the cylindrical coil, and a three-phase alternating current (u-phase current and v-phase current) of 800 A was passed through the # -type twin coil 7 for 5 seconds. Then, as a result of examining the magnetizing directions of the inner and outer surfaces of the tube end and the detection force of the test piece by the continuous method, it was found that the inner and outer surfaces of the tube end were magnetized in all directions.

As described above, according to the apparatus of the present embodiment, magnetizing can be performed in all directions of the inner and outer surfaces of the pipe end by simply inserting the pipe end of the steel pipe 1 as the flaw detection material into the cylindrical portion of the cylindrical coil 2. Therefore, it is not necessary to relatively rotate the steel pipe or the magnetizer, and a device therefor is not required. Therefore, the structure is simpler than the conventional one and the cost can be realized.

Further, since the inner and outer surfaces of the pipe end can be magnetized from the outer surface side of the steel pipe, it is not necessary to insert a magnetizing machine into the pipe, and there is no limitation on the inner diameter of the steel pipe as the material to be inspected. Moreover, since it is not necessary to rotate the steel pipe or the magnetizer as described above, even if the pipe end is bent, there is no risk of scratching the steel pipe or damage to the magnetizer, and stable magnetization is possible.

The number of turns and the shape of each of the b-shaped coils 3 to 6 forming the cylindrical coil 2 and the # -type twin coil 7 are not limited to those in this embodiment, and can be changed according to design conditions. Further, although the center of the cylindrical portion of the cylindrical coil 2 and the pipe axis of the steel pipe 1 as the material to be inspected coincide with each other in the above-mentioned embodiment, there may be some eccentricity due to the magnetic force. other than this,
Needless to say, various modifications can be made without departing from the scope of the present invention.

[Effects of the Invention] As described in detail above, according to the present invention, there is no restriction on the inner diameter and bending of the pipe end, and there is no need to rotate the magnetizer or the steel pipe, and the pipe end has a simple and inexpensive structure. It is possible to provide a steel pipe end magnetizing device capable of easily magnetizing the outer surface and the inner surface of the portion in all directions.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 1 is a configuration diagram showing a layout relation of coils, FIG. 2 is a configuration diagram showing a relation of power supplies connected to the coils, and FIG. FIG. 4 is a diagram showing an example of a three-phase alternating current passed through a type twin coil, and FIG. 4 is a diagram showing a magnetic field direction of a rotating magnetic field generated by the # type twin coil when the three-phase alternating current shown in FIG. 3 is passed. 1 ... Steel tube, 2 ... Cylindrical coil, 3-6 ... B type coil, 7 ... # type coil, 8 ... DC power supply, 9 ... Three-phase AC power supply.

Front page continued (72) Ikuo Yamada Ikuo Yamada 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd. (72) Mitsuo Numakuchi 1-2-13 Higashishimbashi, Minato-ku, Tokyo Sakae Evolutionary Science Co., Ltd. (56) Reference JP-A-59-114456 (JP, A)

Claims (1)

[Scope of utility model registration request] 1. A cylindrical coil wound in a spiral shape along a pipe axis of a steel pipe, a DC power source for DC-magnetizing the cylindrical coil to generate a DC magnetic field, and a coil wound parallel to the pipe surface of the steel pipe. Enclose the steel pipe with the four B-shaped coils
The # -type twin coil arranged in the mold and the two pairs of B-type coils facing each other of the # -type twin coil are connected to each other by a three-phase alternating current (2 /
3) A steel tube end magnetizing device comprising a three-phase AC power source that magnetizes with a current having a π-phase shift to generate a rotating magnetic field.