CN117589862B - A magnetic tomography detection device and method - Google Patents

Abstract

The invention provides a magnetic chromatography detection device and a method, wherein the device comprises a direct current magnetizer, an induction coil probe, a power supply module and a signal conditioning module, wherein the power supply module outputs a step current to change the magnetic field intensity of the direct current magnetizer, so that the step magnetization of a ferromagnetic material to be detected is realized, the induction coil probe is used for detecting the corresponding voltage of magnetic permeability disturbance generated by internal defects on the upper surface of the ferromagnetic material to be detected, the defect position is determined according to the detected peak voltage, and the defect burial depth is determined according to the peak voltage increment. The invention utilizes the characteristic of peak voltage sudden increase when the internal defect of the ferromagnetic material to be detected is magnetized, analyzes the peak voltage increment, characterizes the defect to be magnetized by the inflection point of the peak voltage increment, and determines the defect buried depth by the current value corresponding to the inflection point and a comparison table of preset current and magnetization depth, thereby realizing accurate detection of the internal defect buried depth.

Description

A magnetic tomography detection device and method

Technical Field

The invention relates to the technical field of nondestructive testing of ferromagnetic materials, and in particular to a magnetic tomography testing device and method.

Background technique

Most magnetic flux leakage testing equipment can detect flaws on the outer and inner surfaces of ferromagnetic components. The main methods for inspecting surface defects of ferromagnetic components include magnetic particle testing, eddy current testing, penetration testing and magnetic flux leakage testing. Penetration testing is often used to inspect porous materials. Magnetic particle testing uses the leakage magnetic field generated by the interaction between defects and magnetic fields to inspect defects near the surface or on the surface of structural parts. The above two inspection methods mainly rely on the experience and visual judgment of non-destructive inspection personnel. The automation level is low, and the inspection results are easily affected by the surface attachments of the inspection object. The workload of the inspectors is large. Eddy current testing uses high-frequency current to form an eddy current field on the surface of the inspected object. If there are defects, the eddy current field will change, resulting in changes in the coil impedance, and finally surface defect detection is achieved. The characteristics of eddy current testing are that it is sensitive to crack defects, but the detection effect on pits is not good.

In industry, ferromagnetic components are subject to tensile and compressive stresses of internal fluid loads and physical and chemical effects, and are prone to defects such as corrosion and cracks. The defect scale spans a large range, from tens of microns to tens of millimeters, and is particularly prone to expansion along the depth direction, which is extremely harmful. For example, the main steam pipeline has a large diameter and a thick wall, with a wall thickness of up to 40 mm. The disturbance information obtained by the sensor from deep defects undergoes a greater spatial attenuation than that from surface defects, making detection more difficult. Thick-walled pipelines place higher requirements on nondestructive testing.

However, there is still no good electromagnetic nondestructive testing method to measure the buried depth of macroscopic defects inside ferromagnetic components. Therefore, it is urgent to propose a device that can accurately detect the buried depth of internal defects in ferromagnetic materials.

Summary of the invention

In view of this, it is necessary to provide a magnetic tomography detection device and method to solve the technical problem of being unable to accurately detect the buried depth of internal defects in ferromagnetic materials.

In order to solve the above problems, the present invention provides a magnetic tomography detection device, including a DC magnetizer, an induction coil probe, a power module and a signal conditioning module;

The DC magnetizer and the induction coil probe are both arranged on the upper surface of the ferromagnetic material to be tested, the power supply module is respectively connected to the DC magnetizer, the induction coil probe and the signal conditioning module, and the signal conditioning module is connected to the induction coil probe;

The DC magnetizer is used to perform step magnetization on the ferromagnetic material to be tested based on the step current output by the power module;

The induction coil probe is used to perform defect detection during the step magnetization of the ferromagnetic material to be tested to obtain a magnetic permeability disturbance detection signal corresponding to the step current;

The signal conditioning module is used to process the magnetic permeability disturbance detection signal to obtain the peak voltage and peak voltage increment corresponding to the step current, determine the defect position according to the peak voltage, and determine the defect burial depth according to the current value of the peak voltage increment inflection point and a preset current and magnetization depth comparison table.

Optionally, the induction coil probe includes an excitation coil and a detection coil;

The excitation coil is used to excite a magnetic field on the surface of the ferromagnetic material to be tested;

The detection coil is used to detect the change of the magnetic permeability of the ferromagnetic material to be tested in the magnetization direction and generate a corresponding magnetic permeability disturbance detection signal.

Optionally, the DC magnetizer is a yoke-type magnetizer composed of a U-shaped ferromagnet and a through-type coil.

Optionally, the through-type coil is connected to the power module, and the two magnetic yokes of the U-shaped ferromagnetic body are vertically arranged on the upper surface of the ferromagnetic material to be tested.

Optionally, the DC magnetizer is a through-type DC coil magnetizer.

Furthermore, the present invention also provides a magnetic tomography detection method, which is applied to the above-mentioned magnetic tomography detection device, comprising:

The power module outputs a step current to control the DC magnetizer to perform step magnetization on the ferromagnetic material to be tested;

Using an induction coil probe to perform defect detection during the step magnetization of the ferromagnetic material to be tested to obtain a magnetic permeability disturbance detection signal corresponding to the step current;

The permeability disturbance detection signal is processed based on the signal conditioning module to obtain the peak voltage and peak voltage increment corresponding to the step current, and the defect position is determined according to the peak voltage, and the defect burial depth is determined according to the current value of the peak voltage increment inflection point and the preset current and magnetization depth comparison table.

Optionally, before the power module outputs a step current to control the DC magnetizer to perform step magnetization on the ferromagnetic material to be tested, the method further includes:

The preset current and magnetization depth comparison table is obtained by performing magnetization tests on ferromagnetic materials with different defect burial depths.

Optionally, the step of outputting a step current through a power module to control a DC magnetizer to perform step magnetization on the ferromagnetic material to be tested includes:

Outputting the gradually increasing step current to the DC magnetizer through the power supply module;

The DC magnetizer performs the step magnetization with increasing magnetization intensity on the ferromagnetic material to be tested according to the step current.

Optionally, the method of using an induction coil probe to perform defect detection during the step magnetization of the ferromagnetic material to be tested to obtain a magnetic permeability disturbance detection signal corresponding to the step current includes:

During the process of step magnetization of the ferromagnetic material to be tested, an induction coil probe is used to scan the upper surface of the ferromagnetic material to be tested along the axis direction of the ferromagnetic material to be tested, so as to obtain a plurality of sets of voltage values corresponding to the step currents;

The magnetic permeability disturbance detection signal is generated according to the multiple sets of voltage values.

Optionally, the signal conditioning module is used to process the magnetic permeability disturbance detection signal to obtain a peak voltage and a peak voltage increment corresponding to the step current, and the defect position is determined according to the peak voltage, and the defect burial depth is determined according to the current value of the peak voltage increment inflection point and a preset current and magnetization depth comparison table, including:

Generating a plurality of groups of probe displacement voltage curves corresponding to the step currents one by one according to the magnetic permeability disturbance detection signal;

Determine a plurality of groups of peak voltages according to the plurality of groups of probe displacement voltage curves and determine the defect positions according to the probe positions corresponding to the peak voltages;

Calculating the difference of the peak voltages corresponding to adjacent voltages in the step current to obtain a plurality of groups of peak voltage increments corresponding to the step currents one by one, and generating a peak voltage increment curve;

The defect burial depth is determined according to the current value corresponding to the inflection point in the peak voltage increment curve and the preset current and magnetization depth comparison table.

The beneficial effects of the present invention are as follows: the magnetic tomography detection device provided by the present invention includes a DC magnetizer, an induction coil probe, a power module and a signal conditioning module. The DC magnetizer is controlled by outputting a step current through the power module, and the magnetic field strength of the DC magnetizer is changed by changing the current, thereby realizing the step magnetization of the ferromagnetic material to be tested. The corresponding voltage of the magnetic permeability disturbance caused by the internal defects on the upper surface of the ferromagnetic material to be tested is detected by using the induction coil probe, and the defect position is determined according to the peak voltage obtained by the detection, and the defect burial depth is determined according to the peak voltage increment. The present invention utilizes the characteristic of the sudden increase in peak voltage when the internal defects of the ferromagnetic material to be tested are magnetized, and analyzes the peak voltage increment. The inflection point of the peak voltage increment is used to characterize the magnetization of the defect, and the defect burial depth is determined by the current value corresponding to the inflection point and the preset current and magnetization depth comparison table, thereby realizing the accurate detection of the burial depth of the internal defects of the ferromagnetic material.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

FIG1 is a schematic structural diagram of an embodiment of a magnetic tomography detection device provided by the present invention;

FIG2 is a graph showing relative magnetic permeability and probe displacement when different magnetizing currents are passed through the upper surface of the ferromagnetic material to be tested in an embodiment of the magnetic tomography detection device provided by the present invention;

FIG3 is a graph showing peak voltage and magnetization current values at different defect burial depths in an embodiment of a magnetic tomography detection device provided by the present invention;

FIG4 is a comparison diagram of the magnetizing current of the voltage peak increment and the magnetizing current of the magnetic permeability disturbance of defects at different buried depths in an embodiment of the magnetic tomography detection device provided by the present invention;

FIG. 5 is a schematic flow chart of an embodiment of a magnetic tomography detection method provided by the present invention.

Detailed ways

The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

It should be understood that the schematic drawings are not drawn to scale. The flow chart used in the present invention shows the operations implemented according to some embodiments of the present invention. It should be understood that the operations of the flow chart can be implemented out of order, and the steps without logical context can be reversed in order or implemented simultaneously. In addition, those skilled in the art can add one or more other operations to the flow chart under the guidance of the content of the present invention, and can also remove one or more operations from the flow chart.

Reference to an "embodiment" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

The embodiments of the present invention provide a magnetic tomography detection device and method, which are described below respectively.

FIG1 is a schematic structural diagram of an embodiment of a magnetic tomography detection device provided by the present invention. As shown in FIG1 , it includes a DC magnetizer 10, an induction coil probe 20, a power supply module 30 and a signal conditioning module 40;

The DC magnetizer 10 and the induction coil probe 20 are both arranged on the upper surface of the ferromagnetic material 50 to be tested, the power module 30 is respectively connected to the DC magnetizer 10, the induction coil probe 20 and the signal conditioning module 40, and the signal conditioning module 40 is connected to the induction coil probe 20;

The DC magnetizer 10 is used to perform step magnetization on the ferromagnetic material 50 to be tested based on the step current output by the power module 30;

The induction coil probe 20 is used to perform defect detection in the process of the ferromagnetic material 50 to be tested being step-magnetized to obtain a magnetic permeability disturbance detection signal corresponding to the step current;

The signal conditioning module 40 is used to process the magnetic permeability disturbance detection signal to obtain the peak voltage and peak voltage increment corresponding to the step current, and determine the position of the defect 60 according to the peak voltage, and determine the burial depth of the defect 60 according to the current value of the peak voltage increment inflection point and the preset current and magnetization depth comparison table.

It should be noted that, in the embodiment of the present invention, after the ferromagnetic material 50 to be tested is magnetized, a magnetic field will be formed on the upper surface of the ferromagnetic material 50 to be tested, and the internal defect 60 of the ferromagnetic material 50 to be tested will disturb the magnetic field at the corresponding position of its upper surface. The upper surface of the ferromagnetic material to be tested is scanned by the induction coil probe 20, and the position of the defect 60 relative to the upper surface of the ferromagnetic material 50 to be tested can be determined by the change in the generated detection voltage; due to the different magnetization intensities of the ferromagnetic material 50 to be tested, the degree of magnetization is different, and an unsaturated zone will be formed inside the ferromagnetic material 50 to be tested. If the defect 60 is located in the unsaturated zone, the defect 60 will be The magnetic field disturbance on the upper surface of the material 50 has little effect. If the defect 60 is in the saturation zone, the magnetic field disturbance on the upper surface of the ferromagnetic material 50 to be tested will have a greater impact, which will cause a sudden increase in the voltage of the induction coil probe 20 at the upper surface position corresponding to the internal defect 60. Therefore, the present invention controls the DC magnetizer 10 through the power module 30 to perform step magnetization on the ferromagnetic material 50 to be tested, and continuously deepens the magnetization saturation zone from the upper surface downward. The moment when the internal defect 60 changes from the unsaturated zone to the saturated zone is determined by the peak voltage increment, and the step current corresponding to the moment is determined at the same time. The burial depth of the defect 60 is determined according to the magnetization depth corresponding to the step current (i.e., the preset current and magnetization depth comparison table).

It can be understood that, in the embodiment of the present invention, the peak voltage is the voltage detected at the upper surface corresponding to the internal defect 60. When the current input by the power module 30 is the same, the detection voltage at the upper surface corresponding to the internal defect 60 relative to other positions on the upper surface is the largest, which is the peak voltage. One current value corresponds to one peak voltage. The step current is the current arranged in order from small to large. The peak voltage increment is the increment obtained by subtracting the peak voltage corresponding to the small current from the peak voltage corresponding to the large current in the two adjacent currents. When the internal defect 60 is not magnetized (that is, the internal defect 60 is in the unsaturated zone), each peak The value voltage increment should be roughly the same. When a certain current is input and the difference between the peak voltage corresponding to the current and the peak voltage corresponding to the previous current is significantly greater than other peak voltage increments, it means that the internal defect 60 is magnetized, and the burial depth of the internal defect 60 is the magnetization depth corresponding to the input current; the preset current and magnetization depth comparison table is obtained by testing multiple ferromagnetic materials with different defect 60 burial depths. When the burial depth of the defect 60 is known, the input current corresponding to the inflection point of the peak voltage increment is measured. Through multiple tests, the corresponding relationship table between the input current and the burial depth of the defect 60 can be obtained.

It should be noted that, in the embodiment of the present invention, during detection, the static magnetization field is excited by the DC magnetizer 10, and the current output by the power module 30 is gradually increased to form a step effect. The internal magnetization degree of the ferromagnetic material 50 to be tested is changed by step magnetization, and an unsaturated magnetization region is formed inside the ferromagnetic material 50 to be tested. The unsaturated region generated by the step magnetization is used to layer the ferromagnetic material 50 to be tested in the thickness direction. When there is an internal defect 60 in the ferromagnetic material 50 to be tested, the magnetic lines of force disturb above the defect 60, causing a magnetic field disturbance, so that a larger range of magnetic permeability disturbance is generated in the area above the defect 60, and diffuses to the upper surface of the ferromagnetic material 50 to be tested corresponding to the position of the internal defect 60, presenting a magnetic permeability characteristic different from that of the defect-free area. As the degree of magnetization increases, the defect 60 is partially magnetized, and the defect 60 begins to generate magnetic field distortion, causing fluctuations in the magnetic permeability of the upper surface of the component, and then the magnetic field disturbance caused by the defect 60 is converted into a voltage signal through the induction coil probe 20.

It should also be noted that, in the embodiment of the present invention, the step current output by the power module 30 can be controlled by the current control program of the power module 30 itself, or it can be manually controlled. According to the actual time required for the probe to scan the upper surface of the ferromagnetic material 50 to be tested, the current passed into the DC magnetizer 10 is increased at regular intervals to form a step current, and the value of the current being passed is fed back to the signal conditioning module 40, so that the signal conditioning module 40 can correspond the defect detection result to the step current one by one. The step current can be increased by an equal amount or by an unequal amount. For example, the step current can be divided according to the magnetization depth by stratifying the magnetization depth, and this embodiment does not limit this.

Compared with the prior art, the magnetic tomography detection device provided by the present invention includes a DC magnetizer 10, an induction coil probe 20, a power module 30 and a signal conditioning module 40. The DC magnetizer 10 is controlled by outputting a step current through the power module 30. The magnetic field strength of the DC magnetizer 10 is changed by changing the current, thereby realizing the step magnetization of the ferromagnetic material 50 to be tested. The induction coil probe 20 is used to detect the corresponding voltage of the magnetic permeability disturbance caused by the internal defect 60 on the upper surface of the ferromagnetic material 50 to be tested. The position of the defect 60 is determined according to the peak voltage obtained by the detection, and the burial depth of the defect 60 is determined according to the peak voltage increment. The present invention utilizes the peak voltage sudden increase characteristic when the internal defect 60 of the ferromagnetic material 50 to be tested is magnetized, analyzes the peak voltage increment, and uses the inflection point of the peak voltage increment to characterize the magnetization of the defect 60. The burial depth of the defect 60 is determined by the current value corresponding to the inflection point and the preset current and magnetization depth comparison table, thereby realizing the accurate detection of the burial depth of the internal defect 60 of the ferromagnetic material.

In some embodiments of the present invention, the induction coil probe 20 includes an excitation coil and a detection coil;

The excitation coil is used to excite a magnetic field on the surface of the ferromagnetic material 50 to be tested;

The detection coil is used to detect the change of the magnetic permeability of the ferromagnetic material 50 to be tested in the magnetization direction and generate a corresponding magnetic permeability disturbance detection signal.

It is understandable that, in the embodiment of the present invention, the power module 30 not only outputs step current, but also can output alternating current to the excitation coil, so that the excitation coil excites a magnetic field on the surface of the ferromagnetic material 50 to be tested.

In some embodiments of the present invention, the DC magnetizer 10 is a yoke-type magnetizer composed of a U-shaped ferromagnetic body 12 and a through-type coil 11 .

In some embodiments of the present invention, the through coil 11 is connected to the power module 30 , and the two magnetic yokes of the U-shaped ferromagnetic body 12 are vertically disposed on the upper surface of the ferromagnetic material 50 to be tested.

In some embodiments of the present invention, the DC magnetizer 10 is a through-type DC coil magnetizer.

It can be understood that in the embodiment of the present invention, the corresponding relationship between the relative magnetic permeability and the depth and position of the defect 60 is also tested through simulation experiments. In the simulation, the tested magnetic permeability is distorted because the upper surface of the steel plate is in the connecting part between the air and the inside of the steel. Therefore, a 0.05mm two-dimensional cross-section is set on the upper surface of the steel plate to replace the magnetic permeability disturbance detection signal extracted from the upper surface of the steel plate. When the position of the defect 60 is moved, different magnetizing currents are passed, and the magnetic permeability disturbance detection signals corresponding to each magnetizing current are summarized to form Figure 2. Figure 2 lists the changes in the magnetic permeability disturbance detection signal under different magnetizing currents when the depth s of the defect 60 is 5mm, 10mm, 15mm, and 20mm. The probe displacement is the position of the induction coil probe 20 on the upper surface of the steel plate. For example, when the magnetizing current is 6A, the surface detects that there is a magnetic permeability disturbance. When the magnetizing current reaches 8A, the magnetic permeability disturbance of the defect 60 increases suddenly. , at this time, the defect 60 is magnetized, and the magnetized defect 60 generates a permeability disturbance field and diffuses to the surface to be detected. Finally, the phenomenon of mutation caused by permeability disturbance can verify that when the magnetization current is 8A, the magnetization depth is 10mm; from the above simulation experiment, it can be seen that the internal defect 60 will affect the permeability of the upper surface, and different magnetization currents have different degrees of influence on the permeability. Therefore, the change of permeability can be reflected by voltage, and then the burial depth of the defect 60 can be detected. Figure 3 is a curve diagram of the peak voltage and the magnetization current value (i.e., step current) of different defect burial depths. It can be seen from Figure 3 that when the defect burial depth is 0mm, the step current is 1A, and it has the maximum peak value, which means that 1A corresponds to the burial depth of the defect 60 of 0mm. When the burial depth of the defect 60 is 5mm, the step current corresponding to the maximum peak is 4A, which means that 4A corresponds to the burial depth of the defect 60 of 5mm. By analogy, the burial depth of the defect 60 corresponding to each step current can be obtained.

It can be understood that the present invention compares the magnetizing current of each buried defect voltage peak increment with the magnetizing current of the permeability disturbance. As shown in FIG4 , after inputting the step magnetizing current, the induction coil probe 20 is used to obtain the voltage signal corresponding to each magnetizing current value (i.e., the step current), and the peak value of the voltage signal generated by the adjacent current values is defined as the subtraction: the peak voltage of the large current is subtracted from the peak voltage of the small current to obtain the peak voltage increment of , increase the signal peak value to /> The point where the trend changes is the inflection point, and the magnetizing current value corresponding to the inflection point is recorded as the magnetizing current value/> , the point where each defect causes a sudden change in the permeability disturbance curve is recorded as the magnetizing current of the layer/> , scan the surface with the probe, obtain a set of signals for each buried depth defect under different currents, and extract the signal peak increment/> The magnetizing current value corresponding to the inflection point/> . The magnetizing current value of each buried depth defect voltage peak increment/> Magnetizing current with permeability disturbance/> By comparison, FIG4 is obtained, which shows the inflection point magnetizing current of the peak voltage increment change of the magnetic permeability disturbance detection signal detected by the induction coil probe 20. Magnetizing current at the point of magnetic permeability disturbance/> The changes are basically the same, so it can be concluded that the magnetization current corresponding to each buried depth defect is different. The magnetization current of the defect can be obtained by step magnetization, so as to determine the defect position corresponding to each magnetization current. The last end of the two magnetization current curves tends to be flat because the magnetization is close to saturation. When the magnetization current increases, the corresponding magnetization depth range inside the steel plate becomes larger under the same magnetization current.

FIG5 is a schematic flow chart of an embodiment of a magnetic tomography detection method provided by the present invention. Referring to FIG5 , the present invention further provides a magnetic tomography detection method, which is applied to a magnetic tomography detection device, comprising:

S501, outputting step current through a power module to control a DC magnetizer to perform step magnetization on the ferromagnetic material to be tested;

S502, using an induction coil probe to perform defect detection during the step magnetization process of the ferromagnetic material to be tested to obtain a magnetic permeability disturbance detection signal corresponding to the step current;

S503. Process the permeability disturbance detection signal based on the signal conditioning module to obtain the peak voltage and peak voltage increment corresponding to the step current, determine the defect position according to the peak voltage, and determine the defect burial depth according to the current value of the peak voltage increment inflection point and the preset current and magnetization depth comparison table.

In some embodiments of the present invention, before step S401, the method further includes:

By performing magnetization tests on ferromagnetic materials with different defect burial depths, a comparison table of preset current and magnetization depth is obtained.

In some embodiments of the present invention, step S501 includes:

Outputting a step-by-step increasing current to the DC magnetizer through a power module;

The DC magnetizer performs step magnetization with increasing magnetization intensity on the ferromagnetic material to be tested according to the step current.

In some embodiments of the present invention, step S502 includes:

In the process of step magnetization of the ferromagnetic material to be tested, an induction coil probe is used to scan the upper surface of the ferromagnetic material to be tested along the axial direction of the ferromagnetic material to be tested, so as to obtain a plurality of sets of voltage values corresponding to the step currents;

A magnetic permeability disturbance detection signal is generated according to a plurality of sets of voltage values.

In some embodiments of the present invention, step S503 includes:

Generate multiple sets of probe displacement voltage curves corresponding to the step currents according to the magnetic permeability disturbance detection signal;

Determine multiple sets of peak voltages according to multiple sets of probe displacement voltage curves and determine defect locations according to probe positions corresponding to the peak voltages;

Calculating the difference of the peak voltages corresponding to adjacent voltages in the step current to obtain a plurality of groups of peak voltage increments corresponding to the step currents, and generating a peak voltage increment curve;

The defect burial depth is determined according to the current value corresponding to the inflection point in the peak voltage increment curve and the preset current and magnetization depth comparison table.

It should be understood that other specific embodiments of the magnetic tomography detection method provided by the present invention can refer to the embodiments of the magnetic tomography detection device described above, which will not be described in detail herein.

The above are only preferred specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims (9)

1. A magnetic tomography detection device, characterized in that it includes a DC magnetizer, an induction coil probe, a power module and a signal conditioning module; The DC magnetizer and the induction coil probe are both arranged on the upper surface of the ferromagnetic material to be tested, the power supply module is respectively connected to the DC magnetizer, the induction coil probe and the signal conditioning module, and the signal conditioning module is connected to the induction coil probe; The DC magnetizer is used to perform step magnetization on the ferromagnetic material to be tested based on the step current output by the power module, and continuously deepen the magnetization saturation region from the upper surface of the ferromagnetic material to be tested downward; The induction coil probe is used to perform defect detection during the step magnetization of the ferromagnetic material to be tested to obtain a magnetic permeability disturbance detection signal corresponding to the step current; The signal conditioning module is used to generate multiple groups of probe displacement voltage curves corresponding to the step current one by one according to the magnetic permeability disturbance detection signal, determine multiple groups of peak voltages based on the multiple groups of probe displacement voltage curves, and determine the position of the defect relative to the upper surface of the ferromagnetic material to be tested according to the probe position corresponding to the peak voltage, calculate the difference of the peak voltages corresponding to adjacent currents in the step current, obtain multiple groups of peak voltage increments corresponding to the step current one by one, and generate a peak voltage increment curve, and determine the defect burial depth according to the current value corresponding to the inflection point in the peak voltage increment curve and a preset current magnetization depth comparison table; Among them, the step current output by the power module is a current arranged in sequence from small to large, and each current value corresponds to a peak voltage, the peak voltage increment is the voltage increment obtained by subtracting the peak voltage corresponding to the small current from the peak voltage corresponding to the large current in the two adjacent currents, and the preset current magnetization depth comparison table is a comparison table of the relationship between the current value output by the power module and the magnetization depth. 2. The magnetic tomography detection device according to claim 1, characterized in that the induction coil probe comprises an excitation coil and a detection coil; The excitation coil is used to excite a magnetic field on the surface of the ferromagnetic material to be tested; The detection coil is used to detect the change of the magnetic permeability of the ferromagnetic material to be tested in the magnetization direction and generate a corresponding magnetic permeability disturbance detection signal. 3. The magnetic tomography detection device according to claim 1 is characterized in that the DC magnetizer is a yoke-type magnetizer composed of a U-shaped ferromagnetic body and a through-type coil. 4. The magnetic tomography detection device according to claim 3 is characterized in that the through-type coil is connected to the power module, and the two magnetic yokes of the U-shaped ferromagnetic body are vertically arranged on the upper surface of the ferromagnetic material to be detected. 5. The magnetic tomography detection device according to claim 1, characterized in that the DC magnetizer is a through-type DC coil magnetizer. 6. A magnetic tomography detection method, characterized in that it is applied to the magnetic tomography detection device according to any one of claims 1 to 5, and the magnetic tomography detection method comprises: The power module outputs a step current to control the DC magnetizer to perform step magnetization on the ferromagnetic material to be tested, and the magnetization saturation region is continuously deepened from the upper surface of the ferromagnetic material to be tested downward; Using an induction coil probe to perform defect detection during the step magnetization of the ferromagnetic material to be tested to obtain a magnetic permeability disturbance detection signal corresponding to the step current; Based on the signal conditioning module, a plurality of groups of probe displacement voltage curves corresponding to the step current are generated according to the magnetic permeability disturbance detection signal, and a plurality of groups of peak voltages are determined based on the plurality of groups of probe displacement voltage curves, and the position of the defect relative to the upper surface of the ferromagnetic material to be tested is determined according to the probe position corresponding to the peak voltage, the difference of the peak voltages corresponding to adjacent currents in the step current is calculated to obtain a plurality of groups of peak voltage increments corresponding to the step current, and a peak voltage increment curve is generated, and the defect burial depth is determined according to the current value corresponding to the inflection point in the peak voltage increment curve and a preset current magnetization depth comparison table. 7. The magnetic tomography detection method according to claim 6, characterized in that before the step of outputting step currents through the power module to control the DC magnetizer to perform step magnetization on the ferromagnetic material to be detected, the method further comprises: The preset current magnetization depth comparison table is obtained by performing magnetization tests on ferromagnetic materials with different defect burial depths. 8. The magnetic tomography detection method according to claim 7, characterized in that the step of outputting step current by the power module to control the DC magnetizer to perform step magnetization on the ferromagnetic material to be detected comprises: Outputting the gradually increasing step current to the DC magnetizer through the power supply module; The DC magnetizer performs the step magnetization with increasing magnetization intensity on the ferromagnetic material to be tested according to the step current. 9. The magnetic tomography detection method according to claim 8, characterized in that the defect detection using an induction coil probe during the step magnetization of the ferromagnetic material to be tested to obtain a magnetic permeability disturbance detection signal corresponding to the step current comprises: During the process of step magnetization of the ferromagnetic material to be tested, an induction coil probe is used to scan the upper surface of the ferromagnetic material to be tested along the axis direction of the ferromagnetic material to be tested, so as to obtain a plurality of sets of voltage values corresponding to the step currents; The magnetic permeability disturbance detection signal is generated according to the multiple sets of voltage values.