CN100427947C - Large-area steel plate defect flux-leakage detection method - Google Patents
Large-area steel plate defect flux-leakage detection method Download PDFInfo
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- CN100427947C CN100427947C CNB2006100122894A CN200610012289A CN100427947C CN 100427947 C CN100427947 C CN 100427947C CN B2006100122894 A CNB2006100122894 A CN B2006100122894A CN 200610012289 A CN200610012289 A CN 200610012289A CN 100427947 C CN100427947 C CN 100427947C
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 54
- 239000010959 steel Substances 0.000 title claims abstract description 54
- 238000001514 detection method Methods 0.000 title claims abstract description 43
- 230000007547 defect Effects 0.000 title claims abstract description 13
- 230000004907 flux Effects 0.000 claims abstract description 29
- 239000000523 sample Substances 0.000 claims abstract description 19
- 230000005284 excitation Effects 0.000 claims abstract description 7
- 230000002950 deficient Effects 0.000 claims description 8
- 238000000034 method Methods 0.000 claims description 7
- 238000001914 filtration Methods 0.000 claims description 5
- 230000003321 amplification Effects 0.000 claims description 4
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 4
- 206010038743 Restlessness Diseases 0.000 claims description 3
- 238000003491 array Methods 0.000 claims description 2
- 238000007781 pre-processing Methods 0.000 claims description 2
- 230000005415 magnetization Effects 0.000 abstract description 5
- 238000007689 inspection Methods 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 206010040844 Skin exfoliation Diseases 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000035618 desquamation Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000000696 magnetic material Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910001172 neodymium magnet Inorganic materials 0.000 description 1
- 238000009659 non-destructive testing Methods 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
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Abstract
The present invention relates to a large-area steel plate defect flux-leakage detection method which comprises steps that firstly, an excitation device is used for locally magnetizing a large area steel plate, and by measuring a flux density value at the point of a magnetic pole, a magnetizing saturation state in the steel plate is calculated by using a formula; then, a plurality of magnetic sensitive elements are staggered to array to form a detection probe so as to determine a lift-off value and measure the leakage magnetic flux density of different positions on the surface of the steel sheet with equal intervals, and output signals of two adjacent magnetic sensitive elements are pretreated for difference, etc.; finally, a magnetic flux density value which is measured is compared with a detection threshold value which is set dynamically to judge whether defects exist or not. Because the present invention can effectively judge the local magnetization and saturation state of the steel plate, magnetic circuit parameters of a leakage magnetic probe can be optimized. At the same time, the probe which is formed by staggering to array the magnetic sensitive elements is used for measuring a leakage magnetic field, which can prevent missed detection. Thus, measuring coverage areas and space resolution are enhanced, and the detection precision of surface defects of the large area steel plate is guaranteed.
Description
Technical field
The present invention relates to a kind of lossless detection method to steel plate surfaces externally and internally defective, be particularly related to and a kind ofly large-area steel plate carried out local magnetized by externally-applied magnetic field, utilize its stray field that forms at surface of steel plate to the method that steel plate surfaces externally and internally defective detects fast, belong to technical field of nondestructive testing.
Background technology
In the prior art, adopt ultrasonic method to detect the local defect and the large tracts of land corrosion thinning of steel plate surfaces externally and internally usually, have advantage of high precision though this method detects, its detection efficiency is low, is not suitable for large tracts of land and detects.
Chinese patent application (publication number: CN1373852A) disclose a kind of " the hot rolled steel plate manufacture method of leakage magnetic field inspection and use leakage magnetic field inspection ", this patent is added in magnetic field on the kicker magnet, utilize the leakage field that detects kicker magnet to check its endogenous inclusion, and produce hot rolled steel plate and desquamation steel plate with this method, but this technology is not mentioned the detection method to steel plate surfaces externally and internally defective.
China's utility model patent (Granted publication number: CN 2729723Y) disclose a kind of " direct current motor driven storage tank bottom plate Magnetic Flux Leakage Inspecting instrument ", this utility model is made up of notebook, vehicle frame, data acquisition module, accumulator, d.c. motor, speed reduction unit, driving wheel, magnet, wheel, photoimpact scrambler and leakage field sensor, utilize the defect situation of leakage field sensor dynamic acquisition jar floor iron plate, realize the coordinate setting of defective by the photoimpact scrambler.But this patent is owing to the local magnetized state of saturation to storage tank bottom plate lacks effective determination methods, and the structural parameters of detector and leakage field sensor can not get reasonably optimizing, so accuracy of detection is not high, and driving force was bigger when engineering was used.
Summary of the invention
The objective of the invention is to propose a kind of large-area steel plate defect flux-leakage detection method, promptly utilize the local magnetized state of saturation of the flux density value judgement steel plate between magnetic pole and steel plate, and the dislocation array way of passing through sensor makes up the Magnetic Flux Leakage Inspecting probe, in case the leak-stopping inspection improves coverage and the spatial resolution measured.
Technical scheme of the present invention is as follows:
1) adopt excitation unit that large-area steel plate is carried out local magnetized,, utilize the magnetic flux density of regional area in following formula (1) the calculating steel plate again by measuring the magnetic flux density at magnet magnetic pole place, with the magnetic saturation state of judgement steel plate inside,
Wherein, B
MBe the average flux density in magnetic pole and steel plate gap, W
MBe magnet width, L
PBe steel plate thickness, B
PSaturation magnetic flux density for regional area in the steel plate;
2) adopting the detection probe that is made of a plurality of magnet-sensitive elements is the leakage flux density that 2～4mm uniformly-spaced measures this surface of steel plate diverse location with fixing lift-off value;
3) at first, output signal to adjacent two magnet-sensitive elements is carried out difference processing, then the output signal to whole detection probe superpose respectively, amplification and filter preprocessing, filtering or suppress the random noise and the ground unrest of output signal, and the saltus step amplitude of amplifying flaw indication;
4) dynamically setting detection threshold according to detection speed is 2～10 Gausses, by measured flux density value and this detection threshold are compared, judges having or not of defective.
Feature of the present invention also is: the magnet-sensitive element in the detection probe step 2) adopts the dislocation arranged in arrays.
Large-area steel plate defect flux-leakage detection method provided by the invention owing to can effectively judge the local magnetized state of saturation of steel plate, therefore can be optimized the magnetic circuit parameters of leakage field probe; Simultaneously, utilize the probe of forming by magnet-sensitive element dislocation array to measure stray field, can prevent omission, thereby improve coverage and the spatial resolution measured, guaranteed the accuracy of detection of large-area steel plate surface imperfection.
Description of drawings
Fig. 1 is the Magnetic Flux Leakage Inspecting schematic diagram.
Fig. 2 is the structural representation of detection probe, expresses by a plurality of magnet-sensitive element dislocation layouts to form.
Fig. 3 is the structured flowchart of large-area steel plate defect detection system.
Wherein: 1-armature, 2-magnet, 3-pole shoe, 4-large-area steel plate to be measured, 5-magnet-sensitive element, the air gap height between H-magnetic pole and steel plate, the lift-off value of δ-magnet-sensitive element, 6-detection probe.
Embodiment
Below in conjunction with accompanying drawing detection method provided by the invention is described further.
At first according to the standard saturation magnetic flux density value of thickness He this steel plate material therefor of steel plate to be measured, using formula (1) calculates and selects sizeable excitation unit that steel plate is magnetized, and makes it to the local magnetized state of saturation; Excitation unit is by armature 1, magnet 2, and pole shoe 3 is formed.Figure 1 shows that the detection schematic diagram, excitation unit is placed on certain altitude H on the surface of steel plate, large-area steel plate 4 to be measured is carried out saturated magnetization, and utilizing magnet-sensitive element 5 is the leakage flux density that 2～4mm uniformly-spaced measures this surface of steel plate diverse location with fixing lift-off value; According to accompanying drawing 2 explanations, a plurality of magnet-sensitive elements 5 are pushed the wrong the bit array mode arrange, constitute Magnetic Flux Leakage Inspecting probe 6, there is not omission to guarantee scanning zone, improve coverage and the spatial resolution measured.Wherein, the quantity of the magnet-sensitive element of arranging should make its coverage summation greater than tested zone (as shown in Figure 2); Magnetic Flux Leakage Inspecting probe carries out scanning along direction of magnetization to steel plate, and the output signal of adjacent two magnet-sensitive elements is carried out difference processing, superposes, pre-service such as filtering and amplification filtering or suppress the random noise and the ground unrest of output signal again; Be sent to single-chip microcomputer via interface circuit, single-chip microcomputer will detect data by buffer circuit and be sent to computing machine and store.Simultaneously dynamically setting detection threshold according to detection speed is 2～10 Gausses, by measured flux density value and this detection threshold are compared (as shown in Figure 3), if the flux density value of measuring can judge then that greater than detection threshold there is defective in surface of steel plate.
Embodiment:
Select the thick Q235 steel plate of 12mm as detected object, according to the saturation magnetic flux density size of Q235 material and the calculating of formula (1), select the NdFeB N50 rare earth permanent-magnetic material of long 300mm, wide 30mm, thick 25mm to constitute excitation unit, this steel plate is magnetized, make it saturated to local magnetized with H=5mm magnetization air gap; Press accompanying drawing 2 explanation, 36 integrated hall elements are misplaced to arrange constitutes detection probe, and wherein adjacent elements magnetosensitive sensillary area is spaced apart 2mm; Adopting this probe is the sampling interval of the lift-off value of 2.5mm and 2mm is measured the surface of steel plate diverse location respectively along direction of magnetization magnetic field size with δ; Earlier the output signal of adjacent per two magnet-sensitive elements is carried out difference processing, and then to the output signal of whole Magnetic Flux Leakage Inspecting probe superpose respectively, pre-service such as amplification and filtering, obtain comparatively ideal defect detection signal; Dynamically setting detection threshold according to detection speed (0.5m/s) is 4.8 Gausses (Gauss), after measured leakage flux density value and this detection threshold compared, the leakage flux density value of finding to measure can be judged this surface of steel plate and have defective greater than set detection threshold 4.8 Gausses.
Claims (2)
1. large-area steel plate defect flux-leakage detection method is characterized in that this method carries out as follows:
1) adopt excitation unit that large-area steel plate is carried out local magnetized,, calculate the magnetic flux density of regional area in the steel plate to utilize following formula (1), and judge the magnetic saturation state of steel plate inside by measuring the magnetic flux density at magnet magnetic pole place,
Wherein, B
MBe the average flux density in magnetic pole and steel plate gap, W
MBe magnet width, L
PBe steel plate thickness, B
PSaturation magnetic flux density for regional area in the steel plate;
2) adopting the detection probe that is made of a plurality of magnet-sensitive elements is the leakage flux density that 2～4mm uniformly-spaced measures this surface of steel plate diverse location with fixing lift-off value;
3) at first, output signal to adjacent two magnet-sensitive elements is carried out difference processing, then the output signal to whole detection probe superpose respectively, amplification and filter preprocessing, filtering or suppress the random noise and the ground unrest of output signal, the saltus step amplitude of amplifying flaw indication;
4) dynamically setting detection threshold according to detection speed is 2～10 Gausses, by measured flux density value and this detection threshold are compared, to judge having or not of defective.
2. according to the described large-area steel plate defect flux-leakage detection method of claim 1, it is characterized in that: step 2) described in detection probe in magnet-sensitive element adopt the dislocation arranged in arrays.
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| CNB2006100122894A CN100427947C (en) | 2006-06-16 | 2006-06-16 | Large-area steel plate defect flux-leakage detection method |
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| CN100427947C true CN100427947C (en) | 2008-10-22 |
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Cited By (1)
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| CN102435668A (en) * | 2011-08-31 | 2012-05-02 | 重庆大学 | Array ferromagnetic member surface defect detector based on leakage magnetic field double component |
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| CN102435668B (en) * | 2011-08-31 | 2015-05-27 | 重庆大学 | Array ferromagnetic member surface defect detector based on leakage magnetic field double component |
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