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Sub-saturated time-division and multi-frequency magnetic flux leakage testing method

A magnetic flux leakage detection technology with multiple time divisions, applied in the direction of material magnetic variables, etc., can solve the problems of defect depth information, easy to produce misjudgment, corrosion level assessment, etc., and achieve the effect of broad market prospects, high detection accuracy, and simple probe.

Inactive Publication Date: 2013-06-12
XIAMEN UNIV
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Problems solved by technology

At present, the magnetic flux leakage detection method widely used at home and abroad is difficult to effectively evaluate the corrosion level of defects due to the similarity of the magnetic field leakage of inner and outer wall defects. Scanning cloud images of different detection depths

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  • Sub-saturated time-division and multi-frequency magnetic flux leakage testing method

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Embodiment Construction

[0031] The present invention will be further described below through specific embodiments.

[0032] refer to figure 1 , figure 2 , image 3 and Figure 4 , a half-saturation time-division multi-frequency magnetic flux leakage detection method of the present invention, the magnetizer adopted is composed of a permanent magnet 3 and a U-shaped magnetic core 2 wound with an excitation coil 1, wherein the strength of the permanent magnet 3 is set to measure the steel plate 5 Magnetize to 70-80% of the magnetic saturation state. Therefore, the leakage magnetic field will not be formed on the surface of the steel plate 5 to be tested only by the action of the permanent magnet 3 . Place the magnetizer above the surface of the steel plate 5 to be tested and leave a certain air gap G, the air gap G is 0.5mm-1.5mm, the magnetizer can scan and detect the steel plate 5 to be tested at a certain speed V, and V is 0.2m / s -2m / s. Specific steps are as follows:

[0033] 1) The permanent...

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Abstract

The invention discloses a sub-saturated time-division and multi-frequency magnetic flux leakage testing method. At an early stage, a permanent magnet and direct-current excitation are used for realizing saturated magnetization of a steel plate to be detected; general examination on defects is realized by a magnetic flux leakage signal and positions of the defects are determined; then, a plurality of sine alternative-current excitations with different frequencies are used for replacing the direct-current excitation and carrying out alternating magnetization on the steel plate to be detected; and magnetic flux leakage scanning cloud pictures with different depths are finished by adopting a skin depth difference of the excitations with the different frequencies in an alternating magnetic field. According to the method disclosed by the invention, the disadvantages that the judging effect of the defect depth is not ideal and the accuracy is not high in the existing magnetic flux leakage testing technology are overcome; the method has the advantages of simple probe, convenience in operation and high detection precision on various defects; and the method can be used for detecting steel plates of a pipeline, a storage tank and the like, and has a wide market prospect.

Description

technical field [0001] The invention relates to a non-destructive testing method, in particular to a half-saturated time-division multi-frequency magnetic flux leakage testing method. Background technique [0002] With the wide application of magnetic flux leakage method in pipeline and storage tank steel plate detection, it is more and more important to locate the depth level of defects. On the one hand, it is beneficial to accurately describe the cause of corrosion defects in the flaw detection report, so that different treatment measures can be taken; on the other hand, with the location of the corrosion defect level, the detection signal can be more accurately evaluated and the quantitative accuracy of the detection results can be improved. , to effectively evaluate the actual shape of the defect. At present, the magnetic flux leakage detection method widely used at home and abroad is difficult to effectively evaluate the corrosion level of defects due to the similarity...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N27/83
Inventor 吴德会柳振凉张忠远夏晓昊
Owner XIAMEN UNIV
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