JPH0868779A - Eddy current flaw detection device for steel strip material - Google Patents

Abstract

PURPOSE: To provide a eddy current flaw detection device which enables flaw detection by discirminating a welding part and material changing part from flaws. CONSTITUTION: At the same positions, in longitudinal direction, of a steel strip material 12 which moves continuously, probe sequences 11a and 11b are so assigned that they face each other with the front and rear sides of the steel strip material 12 in between. Integrated circuits 13a and 13b wherein, for each probe sequence 11a and 11b, based on the signal from probes A1-A4.B1-B4 constituting probe sequences 11a and 11b, AND process or OR process is performed, are provided. A decision circuit 14 which, based on the signal from these integrated circuits 13a and 13b, judges whether it is a flaw or not is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eddy current flaw detector for flaw detection and detection of surface flaws in a material to be inspected which continuously moves in a manufacturing process such as a strip steel material.

[0002]

2. Description of the Related Art Various defects are present on the surface of a continuously moving strip steel material. For example, when rolling is performed with foreign matter attached to the rolling roll, the foreign matter is transferred to the steel sheet and a push-in defect occurs. In addition, there are also material defects and the like that occur due to the rolling of foreign substances existing inside the steel sheet.

When a visual inspector overlooks a steel sheet having such defects and ships it as a product, it becomes a user complaint. Therefore, there is a method called eddy current flaw detection as a method for flaw detection described above, and a method as shown in FIG. 4 is a method for detecting defects by eddy current flaw detection.

FIG. 4 (a) is an explanatory view of an eddy current flaw detection method of a through-coil type, in which a coil 2 penetrating a steel plate 1 as a material to be inspected is installed, and a current is passed through the coil 2 to cause a vortex on the steel plate 1. This is a method in which a current is generated and a defect is detected by the disturbance of this eddy current.

FIG. 4 (b) is an explanatory view of a rotary disk type eddy current flaw detection method. Two probes 4 are installed on the same diameter of the rotary disk 3, and each probe is rotated while the rotary disk 3 is rotated. 4 is a method of generating an eddy current in the steel plate 1 and detecting a defect by the disturbance of the eddy current.

FIG. 4C is an explanatory view of a probe type eddy current flaw detection method disclosed in Japanese Patent Laid-Open No. 3-188373.
This is a method in which eddy currents are generated in the steel plate 1 from the probes 4 arranged in a staggered pattern and defects are detected by the difference in eddy currents between the adjacent probes 4.

[0007]

By the way, in carrying out eddy current flaw detection, there are problems such as lift-off fluctuations, material end portions, and material abnormalities. In order to solve these problems, for example, lift-off fluctuations are dealt with by using a phase discrimination method, but this method cannot deal with very large lift-off fluctuations. In addition, the influence of the material edge can be dealt with by detecting the edge with another sensor and not performing flaw detection only on the edge detected using a timer, but this method results in a very long flaw detection length. .

Further, in a steel material 5 such as a strip-shaped steel material in which the manufacturing process is continuous, there is a welded portion 5a as shown in FIG. 5 (a), but the welded portion 5a causes a very large lift-off of 1 to 3 mm. Fluctuation occurs and is detected as an abnormal portion orthogonal to the transport direction. Similarly, as shown in FIG. 5B, the material abrupt change portion 5b that occurs along with the winding of the strip-shaped steel material 5 is also detected as an abnormal portion orthogonal to the transport direction of the strip-shaped steel material 5.

These welds and sudden changes in material are present at the same position on the front and back surfaces of the steel material, and are detected by the eddy current sensors arranged on the front and back surfaces respectively. Therefore, in conventional eddy current flaw detection, these signals should be removed. Was not possible, which was a cause of over-detection.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide an eddy current flaw detection apparatus capable of performing flaw detection by discriminating a welded portion or a material sudden change portion from a defect.

[0011]

In order to achieve the above-mentioned object, an eddy current flaw detector for a strip-shaped steel product according to the present invention is provided at the same position in the longitudinal direction of a continuously moving strip-shaped steel product, at the front and back surfaces of the strip-shaped steel product, or Further, the probe rows arranged so as to face each other across the both sides, and AND processing or OR processing based on the signals from the respective probes that are provided for each of these probe rows and that constitute each probe row The integrated circuit for performing the above and a determination circuit for determining whether or not there is a defect based on signals from each of these integrated circuits are provided, and the determination circuit is arranged at a position facing each other with the strip-shaped steel material sandwiched therebetween. The signals from the integrated circuits based on the signals from the respective probes thus produced have a function of removing the signals detected at the same time.

[0012]

According to the eddy current flaw detection apparatus for a strip-shaped steel material of the present invention, the probe rows are arranged at the same position in the longitudinal direction of the strip-shaped steel material that is continuously moving so as to face each other with the front and back surfaces of the strip-shaped steel material or both sides sandwiched therebetween. And an integrated circuit that is provided for each of the probe rows and that performs AND processing or OR processing based on the signals from the respective probes that form each probe row, and based on the signals from these integrated circuits Since a determination circuit for determining whether or not there is a defect is provided, each integrated circuit performs an AND process or an OR based on the defect signal for each probe forming each probe row.
Processing is performed, and the determination circuit determines from the result as follows.

First, when a plurality of probes forming the probe array detect a defect signal, the integrated circuit determines that the corresponding probe array is defective. When it is judged that the tentacle row is defective at the same time, the method according to claim 1
In the case of, the judgment circuit judges that this signal is a material sudden change portion, a welding point, or lift-off, and does not judge that it is a defect. Further, in the case of claim 2, such a signal is removed by the determination circuit. If it is not determined that either of the facing probe rows is defective, this signal is determined to be a defect. Finally, when all the probes forming the opposing probe row do not detect a defect signal, it is determined that there is no flaw and that the probe is sound.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An eddy current flaw detector for strip steel according to the present invention will be described below with reference to an embodiment shown in FIGS. FIG. 1 is a schematic explanatory view of an eddy current flaw detector for strip steel according to the present invention, and FIG. 2 shows signals of respective probe rows when defects are detected using the eddy current flaw detector for strip steel according to the present invention. FIG. 3 is a diagram showing the determination result, and FIG. 3 is a schematic diagram of another embodiment of the present invention.

In FIG. 1, reference numerals 11a and 11b denote probe rows arranged at the same position in the longitudinal direction of the continuously moving strip-shaped steel material 12 so as to face each other with the front and back surfaces of the strip-shaped steel material 12 interposed therebetween. For example, four probes A1 to A4 and B1 to B4 are provided so that the entire width of the steel material 12 can be detected.
Are arranged in a staggered pattern.

Reference numerals 13a and 13b denote the probe rows 11 described above.
It is an integrated circuit provided for each a.11b, and each probe A1 to A4.B1 of each probe row 11a.11b.
~ AND processing or OR processing is performed based on the signal from B4.

Reference numeral 14 is each of the above-mentioned integrated circuits 13a and 13b.
Is a judgment circuit for judging whether or not there is a defect based on the signal from the, and judges as follows based on the signal from each of the integrated circuits 13a and 13b to discriminate between the defect and the welded part, The result is output to the monitor 15, for example.

First, the integrated circuits 13a and 13b perform AND processing or OR processing to oppose to each other the probe array 11a.
When a plurality of the probes A1 to A4 and B1 to B4 forming 11b detect a defect signal, the fact is output to the determination circuit 14, and the determination circuit 14 outputs the material sudden change portion, the top mark, When it is determined that the welding point or lift-off is detected, the fact is output to the monitor 15, and it is not determined that it is a defect (FIGS. 2C and 2D). This is because they are simultaneously present on the front and back surfaces of the strip-shaped steel material 12 in the entire width direction orthogonal to the transport direction. Further, since such a material sudden change portion and a welding point are removed in a later process, the above-mentioned signal may be removed by the determination circuit 14 when it is not necessary to detect.

Further, as a result of performing the AND processing or the OR processing in the integrated circuits 13a and 13b, either one of the probe arrays 11a and 11b has detected a defect signal, or is facing each other. When a defect signal is detected in only one of the probe rows 11a and 11b,
The fact is output to the judgment circuit 14, and the judgment circuit 14 judges that the side that has detected the defect signal has a flaw [FIG. 2 (a)].
(B)], and output to the monitor 15. This is because most of the defects occur on one of the front and back surfaces, and even if they occur on both the front and back surfaces, most of them do not occur in the entire width direction.

Further, as a result of performing the AND processing or the OR processing in the integrated circuits 13a and 13b, the opposing probe row 11a is formed.
When all of the probes A1 to A4 and B1 to B4 forming 11b have not detected a defect signal, the fact is output to the judgment circuit 14, and the judgment circuit 14 has no defect on both front and back surfaces and is sound. Then, the monitor 15 outputs it.

FIG. 3 is a schematic view of another embodiment of the present invention, in which a probe array is arranged on a pedestal 16 through which the strip-shaped steel material 12 penetrates so that the strip-shaped steel material 12 faces the front and back surfaces and both sides thereof. 11a, 11b, and 11c are arranged, so that the probe rows 11a, 11b, and 11c can detect flaws on the entire width direction and both side surfaces of the strip-shaped steel material 12, for example, four probes each on the front and back sides. A1 to A4 and B1 to B4 are arranged in series, and one probe C1 and C2 are arranged on both side surfaces. Note that the processing after signal detection in this case is also
This is similar to the case of the embodiment shown in FIG.

Further, the AND processing and the OR processing can be appropriately selected depending on the defect signal level, the probe size and the like. Further, in FIG. 1 and FIG.
Although only the series is used, it is also possible to divide into multiple blocks on each material side.

[0023]

As described above, according to the eddy current flaw detector for a strip-shaped steel product of the present invention, the strip-shaped steel product is opposed to the continuously moving strip-shaped steel product at the same position in the longitudinal direction by sandwiching the front and back surfaces of the strip-shaped steel product or both sides. A probe array arranged in an appropriate manner, and an integrated circuit provided for each probe array and performing AND processing or OR processing on the basis of signals from the respective probes forming the probe array,
Since the determination circuit for determining whether or not there is a defect based on the signals from these integrated circuits is provided, it is possible to significantly reduce over-detection associated with a welded portion, a material sudden change portion, or the like.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of an eddy current flaw detector for strip steel according to the present invention.

FIG. 2 is a diagram showing signals and determination results of each probe row when a defect is detected by using the eddy current flaw detector for strip steel according to the present invention shown in FIG.

FIG. 3 is a schematic view of another embodiment of the present invention.

FIG. 4 is a diagram showing an example of an eddy current flaw detection method, in which (a) shows a through coil method, (b) shows a rotating disk method, and (c) shows a probe method.

FIG. 5 is an explanatory diagram of a cause of over-detection, where (a) is a welded portion,
(B) shows a material sudden change part.

[Explanation of symbols]

 11a probe row 11b probe row 11c probe row 12 strip steel 13a integrated circuit 13b integrated circuit 13c integrated circuit 14 determination circuit

Claims (2)

[Claims] 1. A probe row arranged to face each other on both sides of the strip-shaped steel material, or front and back surfaces of the strip-shaped steel material, at the same position in the longitudinal direction of the continuously moving strip-shaped steel material, and for each of these probe rows. An integrated circuit which is provided and performs AND processing or OR processing based on signals from the respective probes forming the respective probe rows, and whether or not there is a defect is determined based on the signals from the respective integrated circuits. An eddy current flaw detector for strip steel, which is equipped with a determination circuit. 2. The determination circuit has a function of removing the signals detected simultaneously by the signals from the integrated circuits based on the signals from the probes arranged at opposite positions with the strip-shaped steel material sandwiched therebetween. The eddy current flaw detection apparatus for strip steel according to claim 1, which is characterized in that.