Large-area steel plate defect flux-leakage detection method

A magnetic flux leakage detection, large-area technology, applied in the direction of material magnetic variables, can solve the problems of low detection efficiency, low detection accuracy, large driving force, etc., to improve the coverage and spatial resolution, ensure detection accuracy, magnetic The effect of road parameter optimization

Inactive Publication Date: 2006-11-22
TSINGHUA UNIV
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Problems solved by technology

[0002] In the prior art, the ultrasonic method is usually used to detect local defects and large-area corrosion thinning on the inner and outer surfaces of steel plates. Although this method has the advantage of high precision, its detection efficiency is low and it is not suitable for large-area detection.
[0003] Chinese patent application (publication number: CN1373852A) discloses a "magnetic flux leakage flaw detection method and a method for manufacturing hot-rolled steel sheets using the magnetic flux leakage flaw detection method". Inspect its internal inclusions, and use this method to produce hot-rolled steel sheets and descaled steel sheets, but this technology does not mention the detection method for internal and external surface defects of steel sheets
However, due to the lack of an effective method for judging the local magnetization saturation state of the tank bottom plate in this patent, the structural parameters of the detector and the magnetic flux leakage sensor cannot be rationally optimized, so the detection accuracy is not high, and the driving force is relatively large in engineering applications

Method used

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Embodiment

[0022] Select the 12mm thick Q235 steel plate as the object to be detected, and select the NdFeB N50 rare earth permanent magnet material with a length of 300mm, a width of 30mm, and a thickness of 25mm to form the excitation device according to the saturation magnetic flux density of the Q235 material and the calculation of formula (1). =5mm magnetization air gap to magnetize the steel plate to make it to local magnetization saturation; according to the attached figure 2 Explain that 36 integrated Hall elements are dislocated and arranged to form a detection probe, and the interval between the magnetically sensitive areas of adjacent elements is 2mm; the probe is used to measure the magnetization direction with a lift-off value of 2.5mm and a sampling interval of 2mm. The magnitude of the magnetic field at different positions on the steel plate surface; firstly, the output signals of every two adjacent magnetic sensitive elements are differentially processed, and then the out...

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Abstract

The disclosed detection method for defect and magnetic leakage of a large-area steel plate comprises: local magnetizing the steel plate, detecting flux density on pole to calculate the inner magnetization saturation state by a formula; then, using multiple magnetic sensitive elements to form a detection probe to detect leakage flux density by equal interval, processing the output signal, comparing the detected value with dynamic-set threshold for decision. This invention improves cover range and space resolution, and ensures detection precision.

Description

technical field [0001] The present invention relates to a method for non-destructive detection of defects on the inner and outer surfaces of steel plates, in particular to a method for locally magnetizing a large-area steel plate through an external magnetic field, and using the leakage magnetic field formed on the surface of the steel plate to quickly detect the defects on the inner and outer surfaces of the steel plate. It belongs to the technical field of nondestructive testing. Background technique [0002] In the prior art, the ultrasonic method is usually used to detect local defects and large-area corrosion thinning on the inner and outer surfaces of steel plates. Although this method has the advantage of high precision, its detection efficiency is low and it is not suitable for large-area detection. [0003] Chinese patent application (publication number: CN1373852A) discloses a "magnetic flux leakage flaw detection method and a method for manufacturing hot-rolled st...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N27/82
Inventor 黄松岭赵伟宋小春
Owner TSINGHUA UNIV
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