A focusing semicircular probe for eddy current defect detection of metal components and its use method

Abstract

The present invention provides a focused semicircular probe for eddy current defect detection of metal components. The focused semicircular probe for eddy current defect detection of metal components is composed of a semicircular magnetic core, an excitation coil and two receiving coils. The two magnetic legs of the semicircular magnetic core are downward, the excitation coil is evenly wound around the outside of the semicircular magnetic core, and the two receiving coils are placed directly below the center line connecting the two magnetic legs of the semicircular magnetic core. The upper surface of the receiving coil is in close contact with the lower surface of the two magnetic legs of the semicircular magnetic core, and the distance between the receiving coils can be adjusted. The focused semicircular probe for eddy current defect detection of metal components provided by the present invention can effectively detect local defects and thickness of the test piece under inspection at a large lifting height. It has higher detection sensitivity than traditional eddy current detection probes and has great application value in local corrosion and wall thickness detection of metal components of pipes with coatings.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic nondestructive testing, and in particular to a focusing semicircular probe for eddy current defect detection of metal components for ferromagnetic pipes with a coating layer, and a method for using the probe. Background Art

[0002] Coated pipes are commonly used in the oil, natural gas, and chemical industries to transport high-temperature, high-pressure, or corrosive gas and liquid media. They are prone to corrosion defects, which are mainly localized. Detecting corrosion defects on the inner and outer walls of coated pipes is a major challenge. Pulsed Eddy Current Testing (PECT) is a non-contact detection method. Compared with traditional eddy current testing, PECT uses square wave excitation, which has the characteristics of a large penetration depth of the incident electromagnetic field, strong defect depth detection capability, and rich detection information. Therefore, PECT has received widespread attention in the application field of corrosion defect detection in coated pipes.

[0003] Pulsed eddy current probes generally consist of an excitation coil and a receiving unit. The conventional excitation coil structure is cylindrical, and the receiving unit is generally composed of a coil or a magnetic sensor. Traditional excitation coils are cylindrical and are widely used for wall thinning and defect detection of metal components. However, cylindrical probes have eddy current diffusion, which is not conducive to eddy current aggregation. U-shaped excitation coils have better focusing characteristics than cylindrical probes in terms of spatial magnetic field distribution and eddy current distribution of the specimen, and are more advantageous for detecting localized corrosion defects under lift-off. However, the two right-angled sides of the U-shaped excitation coil have relatively serious magnetic field leakage, which is not conducive to eddy current aggregation.

[0004] For detecting local defects or thickness changes in ferromagnetic pipes, the above-mentioned probe design and research have achieved good detection results when detecting defects or thickness changes in the test piece at a certain lift, but the focusing performance of the probe is not excellent, and its detection effect and detection capability need to be further improved. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to propose a focused semicircular probe for eddy current defect detection of metal components and its use method, to solve the problem of effectively detecting local corrosion defects and thickness of ferromagnetic pipes under large lift-off, and to solve the problem of pulsed eddy current detection of local defects of metal components under coating conditions and accurate positioning of defects.

[0006] In the first aspect, the present invention provides a focused semicircular probe for eddy current defect detection of metal components, wherein the semicircular probe is composed of a semicircular magnetic core, an excitation coil and two receiving coils, the two magnetic legs of the semicircular magnetic core are downward, the excitation coil is evenly wound around the outside of the semicircular magnetic core, and the two receiving coils are placed directly below the line connecting the centers of the two magnetic legs of the semicircular magnetic core. The upper surface of the receiving coil is in close contact with the lower surfaces of the two magnetic legs of the semicircular magnetic core, and the distance between the receiving coils can be adjusted.

[0007] Furthermore, the wire diameter of the excitation coil of the semicircular probe is 0.1 to 2 mm, and the number of turns is 50 to 2000 turns.

[0008] Furthermore, the wire diameters of the two receiving coils of the semicircular probe are both 0.01 to 1 mm, and the number of turns is 200 to 10,000 turns.

[0009] Furthermore, the distance between the two receiving coils of the semicircular probe is 0 to 100 mm;

[0010] In a second aspect, the present invention further provides a method for using a focused semicircular probe for eddy current defect detection of metal components, the operating steps of which are as follows:

[0011] 1) A pulse signal transmitter, a signal receiver and a computer are provided in the pulse eddy current detector. The excitation coil is connected to the pulse signal transmitter; the receiving coil is connected to the signal receiver;

[0012] 2) Using a semicircular probe to move parallel to the test piece, the semicircular probe moves horizontally along the line connecting the center lines of its receiving coils; the excitation coils on the semicircular probe are excited with a bipolar square wave of equal width, and the semicircular probe is lifted from a height of 10 to 110 mm to start testing from one end of the ferromagnetic pipe to be tested. A test point is selected every 0.1 to 1000 mm. The signal receiver receives the induced voltage signal on the receiving coil and collects voltage data, which is then sent to a computer for processing;

[0013] 3) Using the decay voltage data received by the computer, plot voltage decay curves for different time windows with time as the horizontal axis and normalized induced voltage as the vertical axis;

[0014] 4) The above voltage attenuation curve reflects the defect information of the ferromagnetic pipe near the receiving coil, thereby judging the local corrosion and wall thickness of the specimen.

[0015] The present invention's focusing semicircular probe for eddy current defect detection in metal components and its method of use enable effective detection of local defects and thickness in test pieces even at relatively high liftoff heights. Compared to conventional eddy current detection probes, it boasts higher detection sensitivity and is particularly valuable for detecting localized corrosion and wall thickness in metal components with cladding pipes. The semicircular probe's effect on eddy current focusing can be adjusted by adjusting the size, dimensions, winding wire diameter, number of turns, and distance between the two receiving coils, resulting in varying detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a front view of the semicircular probe in the present invention;

[0017] Figure 2 It is a left side view of the semicircular probe in the present invention;

[0018] Figure 3 A top view of the semicircular probe of the present invention;

[0019] Figure 4 Schematic diagram of the detection system of the present invention;

[0020] Figure 5 It is a front view schematic diagram of a pipeline with defects according to the present invention;

[0021] Figure 6 A side view of a defective pipeline according to the present invention;

[0022] Figure 7 A time diagram of the excitation current and the acquisition voltage of the detection system of the present invention;

[0023] Figure 8 The results of the normalized voltage value for detecting defects and the sensitivity calculation method of the present invention are shown;

[0024] Figure 9 The result of the semicircular probe of the present invention detecting the tested piece;

[0025] In the figure: semicircular probe 01, semicircular magnetic core 11, excitation coil 12, receiving coil 13, pulsed eddy current detector 02, pulse signal transmitter 21, signal receiver 22, probe 23, coating 24, computer 25, test piece 26, embodiment specimen 03, connection time 41, disconnection time 42, connection action 43, disconnection action 44, collected signal 45. DETAILED DESCRIPTION

[0026] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the accompanying drawings. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present disclosure.

[0027] See also Figures 1-9 The present invention provides a focused semicircular probe 01 for eddy current defect detection of metal components. The semicircular probe is composed of a semicircular magnetic core 11, an excitation coil 12 and two receiving coils 13. The two magnetic feet of the semicircular magnetic core are downward, and the excitation coil is evenly wound around the outside of the semicircular magnetic core. The two receiving coils are placed directly below the center line connecting the two magnetic feet of the semicircular magnetic core. The upper surface of the receiving coil is in close contact with the lower surface of the two magnetic feet of the semicircular magnetic core, and the distance between the receiving coils can be adjusted.

[0028] Furthermore, the wire diameter of the excitation coil of the semicircular probe is 0.1 to 2 mm, and the number of turns is 50 to 2000 turns.

[0029] Furthermore, the wire diameters of the two receiving coils of the semicircular probe are both 0.01 to 1 mm, and the number of turns is 200 to 10,000 turns.

[0030] Furthermore, the distance between the two receiving coils of the semicircular probe is 0 to 100 mm;

[0031] In a second aspect, the present invention further provides a method for using a focused semicircular probe for eddy current defect detection of metal components, the operating steps of which are as follows:

[0032] 1) A pulse signal transmitter 21, a signal receiver and a computer are provided in the pulse eddy current detector 02. The excitation coil is connected to the pulse signal transmitter; the receiving coil is connected to the signal receiver;

[0033] 2) Using a semicircular probe to move parallel to the test piece, the semicircular probe moves horizontally along the line connecting the center lines of its receiving coils; the excitation coils on the semicircular probe are excited with a bipolar square wave of equal width, and the semicircular probe is lifted from a height of 10 to 110 mm to start testing from one end of the ferromagnetic pipe to be tested. A test point is selected every 0.1 to 1000 mm. The signal receiver receives the induced voltage signal on the receiving coil and collects voltage data, which is then sent to a computer for processing;

[0034] 3) Using the decay voltage data received by the computer, plot voltage decay curves for different time windows with time as the horizontal axis and normalized induced voltage as the vertical axis;

[0035] 4) The above voltage attenuation curve reflects the defect information of the ferromagnetic pipe near the receiving coil, thereby judging the local corrosion and wall thickness of the specimen.

[0036] The present invention's focusing semicircular probe for eddy current defect detection in metal components and its method of use enable effective detection of local defects and thickness in test pieces even at relatively high liftoff heights. Compared to conventional eddy current detection probes, it boasts higher detection sensitivity and is particularly valuable for detecting localized corrosion and wall thickness in metal components with cladding pipes. The semicircular probe's effect on eddy current focusing can be adjusted by adjusting the size, dimensions, winding wire diameter, number of turns, and distance between the two receiving coils, resulting in varying detection results.

[0037] Specifically, Figures 1 to 3 This is a semicircular probe of the present invention, consisting of a semicircular magnetic core 11, an excitation coil 12, and a receiving coil 13. The shape, size, and magnetic permeability of the semicircular core can be adjusted by selecting different materials. The excitation coil is evenly wound around the semicircular core, and its number of turns and wire diameter are adjustable. The two receiving coils are hollow cylindrical coils, connected in a differential manner, and placed below the magnetic legs of the semicircular core. Their size, wire diameter, and number of turns can be adjusted, and the distance between the two coils can also be adjusted. During probe testing, the two semicircular magnetic legs are oriented toward the test piece, that is, the two receiving coils are placed closer to the test piece and the excitation coil is placed farther from the test piece.

[0038] The schematic diagram of the detection system of the present invention is as follows Figure 4 As shown in FIG, the pulsed eddy current detector 02 includes a pulse signal transmitter 21, a signal receiver 22 and a computer 25. The pulse signal transmitter 21 transmits a pulse signal to the excitation coil of the probe 23 and transmits a synchronization signal to the signal receiver 22. The probe moves on the surface of the coating 24 on the test piece. The signal excitation and reception time are shown in FIG. Figure 7 As shown, each time the signal receiver generates an excitation current to the excitation coil of the probe, when the excitation current is disconnected, the signal receiver will collect the voltage value of the receiving coil and then transmit the data to the computer 25 for processing, storage and display.

[0039] The pulse detector used in the present invention includes a pulse signal transmitter 21 and a signal receiver 22. The computer 25 used is a Windows handheld computer. The pulse eddy current detector 02 is connected to the semicircular probe 01. The pulse signal transmitter 21 provides a stable pulse signal to the probe. The probe is placed on the test piece 26 through the coating 24 to start testing. Figure 7As shown in the figure, the acquisition process is a continuous process. At each moment, the voltage value of the receiving coil changes. The voltage value of the receiving coil is sampled according to a certain rule. In order to process the detection signal in segments, the detection signal of each detection point is divided into several segments (each segment is called a time window), as shown below. The voltage vector obtained at the i-th measurement point is:

[0040] V i =[v i1 v i2 …v i(N-1) v iN ]

[0041] Where N is the off time of each Figure 7 The total number of time windows within the off time in .

[0042] Assuming there are M measuring points, the voltage vectors of the M measuring points can be synthesized into a matrix W:

[0043]

[0044] The jth column in the matrix W represents the jth time window, and the profile vector S j :

[0045] S j =[v 1j v 2j …v (M-1)j v Mj ]

[0046] Among them, the matrix S j The voltage vectors at different measurement points at a given moment in the voltage decay curve are used to determine the presence of defects by observing the voltage information at these points within the same time window. If a defect is present, the voltage at the defective point will be lower than that at the non-defective point within the same time window. The sampling time is divided into 28 time windows (N = 28), and the time window lengths increase logarithmically to better preserve the information in the detection signal.

[0047] In order to quantitatively describe the probe's ability to detect defects, in the test, the probe selects defective and non-defective locations for detection (M=2). After the voltage decay curves at the two locations of the specimen are sectioned, the voltage change amplitudes in the same time window are compared, as shown in the following example: Figure 8 As shown, the detection sensitivity S is calculated e . V f is the voltage vector at the non-defective part, V d is the voltage vector at the defect, V fj With V dj They are the voltage values of the defect-free area and the defect area in the jth time window, and the sensitivity S of the probe in the jth time window ej The calculation method is:

[0048]

[0049] In order to better reflect the detection capability of the probe, the voltage values under multiple time windows are calculated and averaged as the detection sensitivity of the probe. Select the jth time window with better display effect and all the voltage values in the next n time windows, and the sensitivity S e The calculation formula is:

[0050]

[0051] The present invention is described in detail below with reference to examples, but the circular probe and pulsed eddy current detection method of the present invention are not limited to the examples. The test piece used in the test is made of 20# steel pipe with the following dimensions: Figure 5 and Figure 6 As shown: The outer diameter of the pipe is 108mm, the thickness is 8mm, the total length is 1200mm, and a size of 30×30×2.4mm is engraved in the center of the pipe. 3 A groove of (length × width × depth) is used to simulate localized corrosion defects.

[0052] The parameters of the semicircular probe are shown in the following table:

[0053]

[0054] (1) The material used is 20# steel pipe, the size is as follows Figure 5 and Figure 6 As shown, the outer diameter of the pipe is 108mm, the thickness is 8mm, the total length is 1200mm, and a size of 30×30×2.4mm is engraved in the center of the pipe. 3 A groove of (length × width × depth) is used to simulate localized corrosion defects.

[0055] (2) Wrap the steel pipe with a 40mm thick coating and mark the area directly above the defect on the coating surface. Place the center point of the semicircular probe at this location and apply an excitation voltage of 5V. Sample the voltage within the off time and average the five voltage values. Record the value of the receiving coil at each moment. This data is recorded and saved as the data of the defect point.

[0056] (3) Using the above-marked measuring point as a reference, move 200 mm to the right along the pipeline axis. Repeat the above steps. The data here is recorded and saved as the data of the defect-free point.

[0057] (4) Plot the above two sets of data on the same graph, such as Figure 9 As shown, it can be clearly seen that the attenuation curve with defects is below the attenuation curve without defects.

[0058] (5) According to Figure 8The sensitivity is calculated using the method and formula shown.

[0059] The above embodiments merely illustrate the implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, and these modifications and improvements fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A focusing semicircular probe for eddy current defect detection of metal components, characterized in that: The semicircular probe is composed of a semicircular magnetic core, an excitation coil and two receiving coils. The two magnetic legs of the semicircular magnetic core are downward, and the excitation coil is evenly wound around the outside of the semicircular magnetic core. The two receiving coils are placed directly below the line connecting the centers of the two magnetic legs of the semicircular magnetic core. The two receiving coils are hollow cylindrical coils and are connected in a differential manner. The upper surfaces of the receiving coils are in close contact with the lower surfaces of the two magnetic legs of the semicircular magnetic core, and the distance between the receiving coils is adjustable. The wire diameter of the excitation coil of the semicircular probe is 0.1-2 mm, and the number of turns is 50-2000 turns; the wire diameters of the two receiving coils of the semicircular probe are both 0.01-1 mm, and the number of turns is 200-10000 turns; the distance between the two receiving coils of the semicircular probe is 0-100 mm.

2. A method for using the focused semicircular probe for eddy current defect detection of metal components according to claim 1, characterized in that: The following steps are involved: 1) A pulse signal transmitter, a signal receiver and a computer are provided in the pulse eddy current detector, the excitation coil is connected to the pulse signal transmitter, and the receiving coil is connected to the signal receiver; 2) Using a semicircular probe to move parallel to the test piece, the semicircular probe moves horizontally along the line connecting the center lines of its receiving coils. The excitation coils on the semicircular probe are excited by a bipolar square wave of equal width. The semicircular probe is lifted from a height of 10 to 110 mm and tested from one end of the ferromagnetic pipe to be tested. A test point is selected every 0.1 to 1000 mm. The signal receiver receives the induced voltage signal on the receiving coil and collects the voltage data, which is then sent to a computer for processing. 3) Using the decay voltage data received by the computer, plot voltage decay curves for different time windows with time as the horizontal axis and the normalized induced voltage as the vertical axis. The sampling time is divided into several time windows, and the length of the time windows increases logarithmically. 4) The above voltage attenuation curve reflects the defect information of the ferromagnetic pipe near the receiving coil, thereby judging the local corrosion and wall thickness of the specimen.

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