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Magnetic leakage flux flow detection method and mfg. method of hot rolled steel plate using same

A technology of hot-rolled steel plate and flaw detection method, which is applied in the direction of material magnetic variable, electromagnetic measuring device, electric/magnetic roughness/irregularity measurement, etc., and can solve problems such as difficulty in accurately detecting defects, magnetic flux disorder, and leakage

Inactive Publication Date: 2002-10-09
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] When the steel plate 1 is magnetized by the magnetizer 5, if there is a defect 8 inside the steel plate 1, the magnetic flux passing through the inside of the steel plate 1 is disturbed due to the defect 8, and part of it leaks out of the steel plate 1
[0008] But if figure 2 As shown, because the frequency characteristics of the defect signal and the clutter signal overlap, in the case of a small defect or a large clutter, for example, even if a high-pass filter is set, the frequency of the defect signal can be resolved, and the influence of the clutter can be eliminated to accurately detect defects are also difficult

Method used

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  • Magnetic leakage flux flow detection method and mfg. method of hot rolled steel plate using same
  • Magnetic leakage flux flow detection method and mfg. method of hot rolled steel plate using same
  • Magnetic leakage flux flow detection method and mfg. method of hot rolled steel plate using same

Examples

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Effect test

Embodiment 1

[0050] Set on the steel plate inspection line as Figure 5 In the magnetic flaw detection device shown, a steel plate 1 with a thickness of 1 mm is transferred at a speed of 100 m / min, and a saturation magnetic field strength of 2500 AT is applied to the steel plate 1 with a magnetizer 5 a (strong magnetization condition), and a magnetic field of 1000 AT is applied to the steel plate 1 with a magnetizer 5 b. Under saturation magnetization (weak magnetization condition), in the above-mentioned method, the output signal Va of strong magnetization condition is detected by magnetic probe 6a, and the output signal Vb of weak magnetization condition is detected by magnetic probe 6b. The reason for using a magnetic field of 2500AT under strong magnetization conditions and a magnetic field of 1000AT under weak magnetization conditions is that a common clutter signal is detected under the two conditions, and the change of the defect signal level is greater than the change of the clutter...

Embodiment 2

[0054] Figure 8 Another example of a magnetic flaw detection apparatus for carrying out the magnetic flux leakage flaw detection method of the present invention is shown. This device is compatible with figure 1 The magnetic pole center of the magnetizer 5 shown in the current device is different from the magnetic probe 6a in the opposite direction, but another magnetic probe 6b is provided at a position only 4mm apart from the magnetization direction. The distance L between the magnetic probes 6a and 6b was set to 0.7 mm.

[0055] like Figure 8 As shown, a magnetic flaw detection device is installed on the steel plate inspection line, and a steel plate 1 with a thickness of 1 mm is transferred at a speed of 100 m / min. A magnetic field of 3000 AT is applied by a magnetizer 5a to saturate and magnetize the steel plate 1, and a magnetic probe 6a is used to detect the strength of the corresponding example 1 The output signal Va of the magnetization condition is detected by th...

Embodiment 3

[0060] like Figure 10 As shown, using the hot-rolled coil production process with the inclusion inspection process and the process of providing defect information, a low-carbon steel hot-rolled coil with a thickness of 1.8mm and a width of 1m is produced, and the defect inspection is carried out with the oxide scale to obtain the defect position and density information. At this time, in the inclusion inspection process, use a magnetic probe installed at intervals of 5 mm in the width direction of the coil, and Figure 5 The same magnetic flaw detection device was used to detect defects under the same magnetization conditions as in Example 1.

[0061] Figure 11 It shows an example of identifying defect position information in a part of the length direction of the hot-rolled coil within 1000m. In this way, even for hot-rolled coils with scale, the plane position of the defect can be provided by marking. Furthermore, one of information such as the depth, size, and shape of ...

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Abstract

The present invention relates to the invention of the magnetic flux leakage flaw detection method. The strong magnets such as steel plates are magnetized in multiple magnetic fields of different strengths, and the magnetic probes are used to detect the magnetic flux leakage of the magnetized strong magnets, or the strong magnets are magnetized in a certain magnetic field. A plurality of magnetic probes arranged at different positions along the magnetization direction are used to detect the magnetic flux leakage of the magnetized strong magnet, and the output signal of the magnetic probe after the detected magnetic flux leakage is subjected to the calculation of highlighting the signal generated by the internal defect of the strong magnet. In addition, the magnetic flux leakage flaw detection method can be used to detect defects with high precision, so the hot-rolled steel sheet after hot rolling is inspected by this method, and the detected defect is calibrated on the position of the defective steel sheet, so that the correct defect can be grasped in advance. Scaled or descaled hot-rolled steel sheet with location information.

Description

technical field [0001] The present invention relates to a magnetic flux leakage flaw detection method that applies a magnetic field to a strong magnet, detects the magnetic flux leakage from the strong magnet, and checks its internal inclusions, and uses it to produce hot-rolled steel sheets and descaled steel sheets. Background technique [0002] As a method of detecting defects such as inclusions inside a strong magnet such as a steel plate, a magnetic flux leakage flaw detection method is widely used. [0003] As an example, figure 1 Shows the structure of a magnetic flaw detection device using a magnetic probe incorporated in a steel plate inspection line. A magnetic flaw detection device 4 is installed on the product inspection line along the transfer route of the transferred steel plate 1 (strong magnet) using the transfer rollers 2 and 3 at a substantially constant speed V. This magnetic flaw detection device 4 is composed of a magnetizer 5 that magnetizes the steel...

Claims

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Application Information

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IPC IPC(8): G01N27/82G01N27/83
CPCG01N27/82G01N27/83G01B7/34G01N27/87G01N33/20
Inventor 加藤宏晴四辻淳一长栋章生
Owner JFE STEEL CORP
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