WO2010111815A1

WO2010111815A1 - Weak magnetic handling method and device

Info

Publication number: WO2010111815A1
Application number: PCT/CN2009/001224
Authority: WO
Inventors: 窦毓棠; 杨旭; 窦伯英; 窦柏林
Original assignee: 洛阳逖悉开钢丝绳检测技术有限公司
Priority date: 2009-03-31
Filing date: 2009-11-04
Publication date: 2010-10-07
Also published as: CN101593603B; CN101593603A

Abstract

A method for handling a slender ferromagnetic component by weak magnetic field is provided. The method comprises: the step for getting a slender ferromagnetic component going through a magnetic field provided by a weak magnetic handling device to apply the magnetic field to the component along the axis direction of the component, so that every volume element of the component is loaded magnetically; the step for getting the component out of the weak magnetic handling device, so that every volume element of the component is sequentially unloaded magnetically by self-adaption; the step for controlling the magnetic aging of the component to protect the weak magnetic signal of the component from being disturbed, so that a distribution feature of equipotential magnetic energy product is obtained.

Description

Field weakening planning method and device for elongated ferromagnetic members

The invention relates to the field of weak magnetic planning and magnetic non-destructive testing technology for elongated ferromagnetic members, in particular to a weak magnetic planning method and device for elongated ferromagnetic members. Background technique

At present, the traditional magnetization method focuses on the strong magnetic characteristics of the magnetizer. With the magnetic induction intensity as the scale, the field strength value H of the external magnetic field is larger, especially when the ferromagnetic material is in a saturated or near-saturated state, the magnetic induction intensity B is more Close to B _s , the technical features required for subsequent technical measures are more obvious, so the "magnetization" in the usual sense is mainly high-intensity magnetization, or so-called saturation magnetization. Magnetic non-destructive testing, according to the formation of magnetic field signals, is divided into "continuous method" and "remaining magnetic method". The continuous method is to continuously measure the magnetic characteristics of the magnetic saturation state of the tested member while the residual magnetic method is First, the measured member is magnetized to a saturated state as a whole, and then the magnetic characteristics of the remanent state are independently checked. Since the magnetic characteristics (main magnetic flux or defect leakage) of the member to be tested are more obvious, the existing methods are It is necessary to bring the measured member to a saturated or near-saturated magnetic response state, otherwise the magnetic induction device that is originally affected by the lift-off effect is difficult or impossible to extract and recognize an effective magnetic field signal. Therefore, the above methods are also collectively referred to as "strong magnetic detection method".

However, there are two main factors: one is the electromagnetic skin effect of ferromagnetic components, and the other is the inherent limitations of the technical principle, making the detection of surface defects of the components relatively easy, while the deep defects, especially the inside of the components. Defects are still difficult to detect. In the magnetic saturation state, the magnetic permeability of the member becomes lower, which means that the magnetic field change information of the inner layer material of the member is more difficult or even impossible to react outside the member.

In addition, the existing equipment is complicated and cumbersome, the strong magnetic pollution to the tested components, high energy consumption, and the need for demagnetization for repeated detection are all negative effects of magnetic magnetization for magnetic detection. Due to these problems, the strong magnetic detection method is difficult in the general working conditions. It is very convenient to implement. Summary of the invention

SUMMARY OF THE INVENTION It is an object of the present invention to provide a weak magnetic programming method and apparatus for a thin ferromagnetic member which is simple in construction and which minimizes variations and disturbances in the effective magnetic field signal of the magnetic source itself.

In order to achieve the above object, a weak magnetic planning method for an elongated ferromagnetic member according to an embodiment of the present invention is provided, which comprises the steps of:

51. Passing the elongated ferromagnetic member through the magnetic field provided by the field weakening planning device, scanning loading along the axial direction of the elongated ferromagnetic member, so that the volume elements of the elongated ferromagnetic member are sequentially magnetically loaded. the process of;

52, withdrawing the elongated ferromagnetic member from the field weakening planning device, so that each volume element of the elongated ferromagnetic member sequentially completes a process of demagnetization;

a time-dependent control of magnetic aging of the elongated ferromagnetic member that completes the demagnetization, protecting the weak magnetic signal on the elongated ferromagnetic member from disturbance, and causing the elongated ferromagnetic member to be obtained, etc. The distribution characteristics of the weak magnetic energy product.

Preferably, the magnetic field center intensity of the weak magnetic planning device in the step S1 is higher than the corresponding field strength of the maximum magnetic permeability of the elongated ferromagnetic member, and is much lower than the field strength of the saturation magnetization.

Preferably, in step S3, for the magnetic aging period being less than the set value of the magnetic aging fast change period, the control magnetic aging period difference is 0 (ie, the magnetic loading is completely synchronized with the magnetic detection), and the magnetic aging period is faster than the magnetic aging. For the time period setting value, the magnetic aging period is controlled to perform the field weakening detection on the ferromagnetic member before the weak magnetic signal is weakened to 1 Gs, wherein the magnetic aging period is from the loading magnetic field evacuation until the weak magnetic detection sampling. The interval between the magnetic aging periods is the difference between the magnetic aging periods of a certain two volume elements of the elongated ferromagnetic member.

Preferably, for a volume element, the magnetic aging fast varying time period setting is used to control the effect of the initial phase of magnetic aging on the stability of the magnetic energy product.

Preferably, for a plurality of volume elements, the average value of the magnetic aging period is used to control the effect of the magnetic aging period difference on the consistency of the magnetic energy product on different volume elements. Embodiments of the present invention also provide a field weakening planning device for an elongated ferromagnetic member, the weak magnetic planning device being surrounded by a magnetic source to form a finite length hollow core spiral current carrying tube or an equivalent magnetic field space thereof The device is configured to have an opening such that the elongated ferromagnetic member can be inserted radially from the opening or can be axially penetrated from one end of the device to be surrounded by the magnetic field formed by the field weakening planning device In the space.

Preferably, the magnetic source is a direct current coil, a permanent magnet or a combination thereof.

Preferably, the field weakening planning device is one of a DC single coil, a DC coil combination, a permanent magnet sleeve, a permanent magnet magnetic tile combination or a permanent magnet bar combination.

The above technical solution has the following advantages: after the weak magnetic planning is performed on the elongated ferromagnetic member by using the above-mentioned planning device and method, the magnetic state difference between the material and the structural defect having the volume-price swap relationship is established on the member, and the weak magnetic detection is performed. The method provides a prerequisite guarantee. The detection based on this can not only make the detection have excellent detection performance such as high sensitivity, high resolution and high stability, but also minimize the variation and interference of the magnetic source itself to the effective magnetic field signal, so that the sensor Received significant magnetic field signals with significant alienation, no fundamental noise, and high fidelity.

detailed description

The specific embodiments of the present invention are further described in detail below with reference to the drawings and embodiments. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

1 is a flow chart showing a weak magnetic planning method of an elongated ferromagnetic member according to an embodiment of the present invention;

2a-2e are schematic views showing several structures of a field weakening planning device for an elongated ferromagnetic member according to an embodiment of the present invention;

3 is a magnetic loading/discharging B-H action diagram of a weak magnetic planning method for an elongated ferromagnetic member according to an embodiment of the present invention;

4 is a (BH)-t magnetic aging control curve diagram of a weak magnetic planning method of an elongated ferromagnetic member according to an embodiment of the present invention;

5 is a magnetic domain of a weak magnetic planning method of an elongated ferromagnetic member according to an embodiment of the present invention; Schematic;

6 is a schematic view showing a demagnetization curve and a magnetic energy product of a field weakening planning method of an elongated ferromagnetic member according to an embodiment of the present invention;

Fig. 7 is a magnetic hysteresis curve characteristic diagram of a field weakening planning method of an elongated ferromagnetic member according to an embodiment of the present invention.

Embodiments of the present invention provide a field weakening planning method and apparatus for an elongated ferromagnetic member, which may be medium to high carbon content steel, iron, and other iron alloy material members. The weak magnetic programming method is realized by using three technical processes of quantitative magnetic loading, adaptive release, and steady magnetic energy product of the weak magnetic planning device, and the process flow block diagram is shown in FIG. 1 . In Fig. 1, 1 represents a quantitative magnetic loading link, 2 represents an adaptive release carrier link, 3 represents a steady state magnetic energy product link, and 4 represents a weak magnetic detection link (not specifically illustrated by the present invention, indicated by a broken line).

The quantitative magnetic loading, that is, the irreversible magnetic induction control process. Under the control and action of the weak magnetic planning device, each volume element of the elongated ferromagnetic member is sequentially subjected to a magnetic loading process in a pipeline manner. The magnetic loading effect relationship for any one volume element is shown in Figure 3 on the 0→P segment. The magnetic domain contained by the volume element moves the domain wall in a uniform direction due to the action of a given field strength and merges and merges until a "single magnetic domain region" is formed. In operation control, it is required to: pass the elongated ferromagnetic member through the weak magnetic planning device and scan and load along the axial direction of the member; when the elongated ferromagnetic member passes, the magnetic field in the weak magnetic planning device remains constant, the central magnetic field The intensity is (slightly higher than Η _μπι , but significantly lower than the field strength of the saturation magnetization), and the direction is parallel to the axial direction of the elongated ferromagnetic member. Where Η _μιη represents the magnetic field strength corresponding to the maximum magnetic permeability of the ferromagnetic member material of 4 _m . The volume element, that is, a series of volume differentials of the elongated ferromagnetic member in the axial direction.

The adaptive release load is a diamagnetic process after quantitative magnetic loading. In the process of magnetically distributing the elongated ferromagnetic member in a pipeline manner, as the volume element exits from the weak magnetic planning device and gradually moves away, it enters the demagnetization process by itself. The magnetic release effect relationship for any one volume element is shown in Fig. 3 on the P→Q segment. With the field strength from H n reduced to Zero, the corresponding magnetic induction is reduced to ≠ 0 (the demagnetization starting point of a B-H leaflet small return line). In addition, in Fig. 3, 0—→∞ is the basic magnetization curve, O → k is the reversible magnetization stage, k “ is the sharp magnetization stage, m—“ ^ is the near saturation magnetization stage, and j “” is the saturation magnetization stage. A "^ is the limit hysteresis loop, ∞一" ^ is the demagnetization process, r-→c is the demagnetization process. (-Η^, Η^) is the weak magnetic working area, (Hj, H») is the strong magnetic Work area 0 (0,0)

For the adaptive release process, (BH) _t o is the magnetic energy aging starting point magnetic energy product.

The steady state magnetic energy product, that is, the time-dependent control process for magnetic aging. In the operation control requirements: 1 from the completion of the magnetic loading until the end of the weak magnetic detection sampling, must avoid the strong external magnetic field, mechanical stress or high temperature environment on the ferromagnetic components on the weak magnetic signal; 2 magnetic aging period is shorter (Τ < δ ), it is necessary to control the magnetic aging period difference to zero (ΔΤ = 0), that is, the detection and planning are performed at the same speed; 3 The relative aging period of the magnetic aging period is long (such as Τ > δ, and |ΔΤ| < /Κ) The magnetic aging period needs to be controlled to perform the weak magnetic detection on the ferromagnetic member before the weak magnetic signal is weakened to the lGs level.

Wherein, corresponding to a certain volume element, the interval from the start of the loading magnetic field evacuation to the weak magnetic detection sampling is the magnetic aging period (T). According to the object of action (elongated ferromagnetic member), the magnetic aging fast-changing period setting value (δ) is technically used to control the influence of the initial stage of magnetic aging on the stability of the magnetic energy product.

Corresponding to a certain volume element, their difference in the length of the magnetic aging period is the period difference (ΔΤ). According to the object of action (slender ferromagnetic member), the average value of the magnetic aging period is used to control the influence of the magnetic aging difference on the consistency of the magnetic energy product on different volume elements.

For any two volume elements, the relationship between the respective magnetic energy product (ΒΗ) and time t^J is shown in Fig. 4.

As shown in Figures 2a-2e, the field weakening planning device of the present invention is constructed of a DC coil, a permanent magnet, or a combination thereof. Preferably, but not limited to: DC single coil (Fig. 2a), DC coil combination (Fig. 2b), permanent magnet sleeve (Fig. 2c), permanent magnet and magnetic tile combination (Fig. 2d), permanent magnet bar combination (Fig. 2e) and other structural forms. The magnetic field weakening planning device is surrounded by a magnetic source (DC coil or permanent magnet) to form a finite length hollow core spiral current carrying tube or an equivalent form of the magnetic field space; the elongated ferromagnetic member may be The special opening on the device is inserted radially or can be axially penetrated from one end of the device, surrounded by the magnetic field space enclosed by the weak magnetic planning device; the weak magnetic planning device is used for the elongated iron Quantitative magnetic loading of magnetic components (corresponding to "irreversible magnetization") process.

Based on the magnetic domain theory of quantum mechanics, the magnetic induction (induction intensity) of the ferromagnetic material following the external magnetic field (field strength) is briefly explained here. The physical cause, the changing law and related conceptual terms.

1, magnetic domain

The magnetic properties of ferromagnetic materials are mainly derived from the electron spin magnetic moment. According to the theory of quantum mechanics, there is a strong exchange coupling between adjacent electrons in ferromagnetic materials. Below the Curie temperature, their spin magnetic moments can be arranged "spontaneously" in a tiny area. As a result, a small area of spontaneous magnetization, that is, a magnetic domain is formed, as shown in FIG. The magnetic domains have a volume of about 10 - ¹² m ³ to 10 - ⁹ m ³ and contain about 10 ¹⁷ to 10 2 ^Q atoms. In actual magnetic materials, magnetic domain shapes are varied, such as strip domains, labyrinth domains, wedge domains, ring domains, dendritic domains, bubble domains, and the like.

In the unmagnetized ferromagnetic material, the spontaneous magnetization direction of each magnetic domain is disordered, so that magnetic properties are not displayed macroscopically, and the ferromagnetic material is said to be in a magnetic neutral state.

2. Magnetization process of ferromagnetic materials

The process of ferromagnetic material from the magnetic neutral state to the magnetic saturation state under the action of an external magnetic field is called a magnetization process. The process of returning from the magnetic saturation process to the demagnetization state under the action of an external magnetic field is called a demagnetization process. The magnetization process is divided into four stages: reversible, sharp, near saturation and saturation magnetization. As shown in Figure 3.

Reversible magnetization: When an external magnetic field with a small intensity starts to act on the ferromagnetic material, domain wall displacement occurs in each magnetic domain, and those magnetic domains whose magnetic moment direction is close to the direction of the external magnetic field (referred to as "near magnetic domain") External expansion, a magnetic domain that is roughly opposite to the direction of the external magnetic field (referred to as "the opposite direction" The magnetic domain ") shrinks inwardly. However, this process is reversible, that is, when the external magnetic field is removed, the domain wall will still return to the original position, and the material will return to the magnetic neutral state.

Sharp magnetization: Under the action of the external magnetic field that continues to strengthen, the movement of the domain domain wall appears to be a jump, called the Buckyson jump. The change of the magnetic domain structure is characterized by the fact that the near magnetic domain sequentially engulfs those adjacent magnetic domains. When the external magnetic field is increased to Η _μηη , the domain wall movement is completed, and the opposite magnetic domains are all swallowed to the near magnetic domain, becoming a single magnetic domain. Domain regions, at which time the magnetic moment directions of these magnetic domains are still not completely consistent with the direction of the external magnetic field. The process corresponds to the k→m segment of the Β-Η curve shown in Fig. 3. The magnetic induction B increases sharply with the increase of the applied field strength H. This is because the sudden volume of the magnetic domain structure is greatly increased due to the annexation, and macroscopically It is manifested by an accelerated increase in the magnetic permeability of the material. At the end of the sharp magnetization, the magnetic permeability of the material reaches a maximum.

The abrupt magnetization described above is an irreversible magnetization process, that is, the changed domain wall position and magnetic domain structure are not restored as they are due to the evacuation of the external magnetic field, and the material can generate hysteresis.

Magnetic saturation, including near saturation magnetization and saturation magnetization. If the field strength is continuously increased at the end of the abrupt magnetization, the magnetic domain magnetic moment retained after the engulfing will be gradually turned to the direction of the external magnetic field. In general, the rotation of the magnetic domain magnetic moment is both reversible and irreversible, and occurs at this stage. After the ferromagnetic material undergoes near saturation magnetization to reach the magnetic saturation state, the magnetic induction intensity increases little with the increase of the external magnetic field strength, which is caused by the last small amount of reversible rotation of the magnetic domain magnetic moment until the magnetic moment orientation and The direction of the magnetic field is exactly the same. The saturation magnetization value generated at this time is called saturation magnetic induction (B _s ;).

3, hysteresis

Due to the presence of doping and the like in the ferromagnetic material, there is some kind of "friction" between the magnetic domains, which hinders each magnetic domain from returning to the degaussing state of the original chaotic arrangement after removing the external magnetic field. This is the cause of macroscopic remanence and hysteresis. Therefore, even if the external magnetic field acting on the ferromagnetic material is reduced from the saturation corresponding value to zero, the magnetic moment does not return to zero, and the next magnetization effect remains. This residual magnetization value is called residual magnetic induction.

4. Magnetic permeability and material permeability

Magnetic permeability, μ = = μ. μ _Γ also known as the magnetic permeability coefficient, is a representation of matter (magnetic media) The physical quantity of magnetic permeability reflects the ability of the substance itself to help the flux pass. Where: μο = 4πχ 10- ⁷ Η/ιη (Heng per meter) means "vacuum permeability". ^ indicates the relative permeability, which is a variable related to the field strength.

According to the theory of object polarization, the magnetic permeability of an object is not the same concept as the magnetic permeability of the material that constitutes it. _→ The relationship between them can be expressed by the following vector formula:

Β = μ ₀ μ _τ Η where: Α = _{1 + Λ} — represents the "magnetic permeability tensor" of the magnetic induction intensity orientation, Ν represents the "demagnetization coefficient" determined by the shape and size of the object λ, and λ represents the magnetic field of the object The "anisotropic coefficient" of the crystal.

Under the action of pure mechanical load, the magnet usually cannot cause the change of the magnetic permeability of the material, but it will cause significant changes in the magnetic permeability of the object. For example, the magnetization of the permanent magnet is related to the demagnetization coefficient 影响 of the geometric shape at room temperature, and the ferromagnetic member The magnetostrictive effect is related to the magnetocrystalline orientation anisotropy λ affected by processes such as cold rolling and cold drawing.

5, magnetic energy product

The magnetic energy product can also be written as "(ΒΗ)", which is the product of the magnetic induction Β and the external magnetic field strength Η at any point of the demagnetization curve (two quadrants), specifically reflecting the volume of the magnet stored in the external magnetic field it generates. The energy level is also the ability of the magnet to do work externally. Its international unit of measurement is expressed in "J/m ³ " (Joules per cubic meter). '

After the magnet is separated from the external magnetic field, there is a demagnetizing field H _D in the opposite direction to the magnetic induction intensity B. Under the action of H _D , the magnetic induction B is at the B _D position, that is, the working point of the magnet, and B _{D is} called apparent remanence. As shown in Figure 6. The determined relationship between H _D and B _D is only related to the demagnetization coefficient N of the magnet (or to the geometry and size of the object).

Moreover, since the working performance of the magnet reflected by the magnetic energy product depends on the combined action of the demagnetizing magnetic field and the external magnetic field, the magnet is in the performance, except for the degree of magnetization at the starting point on the demagnetization curve.

In addition, it is only related to the geometry of the magnet itself. The weak magnetic detection method just happens to integrate the magnetic energy from each part of the ferromagnetic member, so that various defects including geometric variation inside and outside the member can be found. Weak magnetic planning method: The weak magnetic energy release state of the elongated ferromagnetic member is related to the continuous distribution of the structural properties of the load material, which is measurable and comparable. This distribution characteristic is directly related to the irreversible magnetization effect of the component.

1. Characteristics in the basic physical sense

The "weak magnetic planning" method of the present invention focuses on the pursuit of the maximum "irreversible magnetization" of the magnetic material, and it is necessary to merge the magnetic domains with each other in a specific magnetic moment direction and expand into a single magnetic domain region. In fact, the magnetic induction intensity is not tested, but the extreme value of the magnetic induction strength as a function of the field strength (ie, the magnetic permeability of the material) is tested, and it is not necessary to reach near saturation or saturation.

2. Characteristics on the working magnetic field threshold

The apparent magnetization characteristic (BH curve) of the method corresponds to the reversal magnetization of the ferromagnetic member and the demagnetization process of the weak magnetic region, and the field strength value corresponding to the maximum magnetic permeability of the member is the upper limit at the threshold of the working magnetic field strength. Unlike the limit hysteresis loop characteristics of ferromagnetic components, especially independent of the saturation magnetization of the component

The saturation magnetization means and the "weak magnetic planning" method of the present invention have an obvious separation band at the threshold of the working magnetic field, as shown in FIG. 3, that is, (H^ _m , Hj), the saturation magnetization field strength H needs to be larger than Hj. The usual magnetic induction level is above IT, which belongs to the strong magnetic range, while the field strength H of the weak magnetic working magnetic field is less than Η _μπ1 , and the normal magnetic induction intensity is below _10mT , which is weak according to the academic concept of modern magnetic detection technology. Magnetic range (for details, see Ship Electronic Engineering, 2006, No. 4, "Weak Magnetic Field Testing Methods and Instrument Research", etc.).

3, the characteristics of the use of ^ method

Combined with the weak magnetic detection, the difference between the method and the strong magnetic detection technology of the present invention is basically manifested in three aspects:

In terms of response characteristics, the magnetization means in the strong magnetic detection technology follows the limit hysteresis loop characteristic of the ferromagnetic material, and the weak magnetic planning method conforms to the "leaf" small loop characteristic of the ferromagnetic material, as shown in FIG. In terms of energy conversion, the strong magnetic detection technique or the maximum magnetic energy product (BH) _max that can be achieved by a material, or the external magnetic field intervention, is used to measure its magnetization. The influence of technology on detection, and the present invention measures the influence of magnetic planning on detection by the magnetic state balance of the small magnetic energy product trait finally possessed by the material, and does not use the external strong magnetic field intervention detection method. In terms of information carriers, the strong magnetic detection technology (represented by the main magnetic flux and magnetic flux leakage detection) uses the "magnetic flux given on the ferromagnetic member" as the information carrier to be detected, and the present invention will be "on the ferromagnetic member" The equipotential weak magnetic energy product is the information carrier for detection.

The weak magnetic planning device of the embodiment adopts a N35 grade Nd-Fe-B rod magnet as a magnetic source, and is arranged in a ring shape along the outer diameter (p46 mm plastic skeleton, formed in the skeleton (p40 mm (diameter) x 75 mm (axis) In the magnetic field space of the length), the axial magnetic field strength at the center of the device is 1035 A/m (measured value is 1.3 mT when no magnet is interposed). If it is to conform to other cross-section shapes and materials with a circular cross section or equivalent area of p36 mm or less An elongated ferromagnetic member of medium-high carbon content steel, iron and other iron alloys (larger sections may cause too small a gap between the device and the component, which is not conducive to mutual movement), and are placed radially from the special opening of the device. , closing the opening, a section of the component is enclosed in the magnetic field space.

The elongated test piece for implementing the weak magnetic planning in the example is a set of uniform steel wires. The number of wires in the group is 100, and the diameter of a single wire (pl. 2mm, the material is material supply state 45 steel, the length of the head is > 8111. When passing through the weak magnetic planning device (quantitative magnetic loading and adaptive release process), the running trajectory is consistent with the central axis of the weak magnetic planning device. Under the action of the center position 1035A/m field strength, the local magnetic induction of the test piece The strength reached 0.78T, indicating that the part has completed the quantitative magnetic loading.

Note: The maximum relative magnetic permeability of 45 steel in cold-drawn state is ^=583, 3⁄4 _m =960A/m. For details, please refer to page 25 of the Manual of Non-destructive Testing Technology for Non-destructive Testing of Weapons Industry. Beijing, Mechanical Industry Press, first edition, June 2003.

The test piece was passed through the field weakening planning device for 15 seconds (|ΔΤ| < 15 seconds), and the weak planning device was moved to a distant position after completion to avoid disturbance of the weak magnetic signal on the test piece. Since the quantitative magnetic loading and adaptive magnetic demagnetization of each unit volume element in the middle section of the test piece (the effective section not affected by the end magnetic pole) are exactly the same, their initial remanence state is completely the same, Τ < δ=25 In minutes, the weak magnetic detection can be performed at any time using the synchronous operation mode. Fast after magnetic aging After 25 minutes of variation, T > 5 = 25 min, and Κ | ΔΤ | = 100 | ΔΤ | < Tmin = 25 minutes < f , the (ΒΗ) product in the middle of the test piece was measured to be 7.8 J/m ³ , Positive and negative deviations < 5%. . At this time, both synchronous and asynchronous operation modes can meet the needs of weak magnetic detection.

Note: In the absence of defects, the magnetic state of the test piece is expressed as the equivalent (BH) product of each volume element.

The invention has the beneficial effects that the present invention provides a distribution feature for the elongated ferromagnetic member to have an equipotential weak magnetic energy product in each axial volume element, and the difference information of the magnetic states of each volume element reflects the materials inside and outside the member. And structural trait variation, providing a prerequisite for weak magnetic detection. The magnetic detection of the elongated ferromagnetic member is a non-destructive means of detecting the presence of defects in the member by utilizing the magnetic properties of the member itself. The advantages are high detection efficiency, reliable data science, and relatively low technical cost. Due to the technical solution of the present invention, load materials and structural defects caused by stress, strain, or the like, such as tension, bending, twisting, and pressing, can be continuously and uniformly formed along the central axis direction on the long ferromagnetic member. The difference in the magnetic state of the distributed unit volume element is objectively reflected. The qualitative and quantitative relationship between the magnetic state difference and the defect is not affected by the original structure of the component and the depth of the defect, and the detection of no fundamental noise is achieved, and the signal sensitivity is high and stable. it is good. The completion of the field weakening detection eliminates the need for a conventional magnetizing device. The overall size of the device is small and lightweight, making it easy to carry, install, use and maintain. The above solution effectively avoids the ferromagnetic component under working condition from being strongly magnetically contaminated, thereby having superior applicability, safety and energy saving effects. Magnetic planning is a technical process that quantifies magnetic loading, adaptive release, steady-state magnetic energy product, and finally obtains the distribution characteristics of equipotential weak magnetic energy. Compared with the strong magnetization-detection technique, the weak magnetic programming method does not need to pay more attention to how to obtain a strong magnetic induction signal, because the magnetic loading strength it is to achieve is relatively easy to achieve, and is sufficient for the weak magnetic detection.

The above is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can make several improvements and modifications without departing from the technical principles of the present invention. It should also be considered as the scope of protection of the present invention. Industrial applicability The invention provides a distribution feature for the elongated ferromagnetic member to have an equipotential weak magnetic energy product in each axial volume element, and the difference information of the magnetic states of each volume element reflects the trait variation of the materials and structures inside and outside the member. Provides a prerequisite for weak magnetic detection. The magnetic detection efficiency of the elongated ferromagnetic member is high, the data is scientific and reliable, and the technical cost is relatively low. The technical solution of the present invention enables load materials and structural defects caused by tensile strain, bending, torsion, pressure and the like to be dominant or equivalent, and can be continuously and uniformly distributed in the central axis direction on the elongated ferromagnetic member. The difference in the magnetic state of the element is objectively reflected, and the detection of no fundamental noise can be achieved, and the signal sensitivity is high and the stability is good. The device that completes the weak magnetic detection is small in size, light in weight, and easy to carry, install, use and maintain. The ferromagnetic member under working condition is effectively prevented from being strongly magnetically contaminated, thereby having superior applicability, safety and energy saving effects. Compared with the strong magnetization-detection technology, the weak magnetic programming method does not need to pay more attention to how to obtain a strong magnetic induction signal, because the magnetic loading intensity to be achieved is relatively easy to achieve, and is sufficient for the weak magnetic detection.

Claims

A weak magnetic planning method for an elongated ferromagnetic member, characterized in that the weak magnetic planning method comprises the steps of:

53. Performing time-dependent control of magnetic aging on the elongated ferromagnetic member that completes the remagnetization, protecting the weak magnetic signal on the elongated ferromagnetic member from being disturbed, and obtaining the elongated ferromagnetic member. The distribution characteristics of the weak magnetic energy product.

The method of weak magnetic field planning of an elongated ferromagnetic member according to claim 1 or 2, wherein the magnetic field center strength of the weak magnetic planning device in the step S1 is higher than the elongated ferromagnetic member The corresponding field strength of the maximum magnetic permeability is much lower than the field strength of the saturation magnetization.

The weak magnetic planning method for an elongated ferromagnetic member according to claim 1 or 2, wherein in step S3, the magnetic aging period is controlled by a magnetic aging period that is smaller than a set value of a magnetic aging fast changing period The time difference is 0. For the magnetic aging period greater than the set value of the magnetic aging fast change period, the magnetic aging period is controlled before the weak magnetic signal is weakened to 1 Gs, and the magnetic aging period is performed on the ferromagnetic member. The interval of the magnetic aging period is the difference between the magnetic aging periods of the two volume elements of the elongated ferromagnetic member for the interval from the start of the loading of the magnetic field to the time of the weak magnetic detection.

4. The field weakening planning method for an elongated ferromagnetic member according to claim 3, wherein, for one volume element, a magnetic aging fast-changing period setting value is used to control the stability of the magnetic energy product in the initial stage of magnetic aging. influences.

5. The field weakening planning method for an elongated ferromagnetic member according to claim 3, wherein, for two or more volume elements, a magnetic aging period average value is used to set a magnification ratio of the magnetic aging period difference. Control the influence of the magnetic aging period difference on the consistency of the magnetic energy product on different volume elements.

6. A field weakening planning device for a weak magnetic planning method for an elongated ferromagnetic member, characterized in that the weak magnetic planning device is surrounded by a magnetic source to form a finite length hollow core spiral current carrying tube a magnetic field space, the device being arranged to have an opening such that an elongated ferromagnetic member can be placed radially from the opening or can be axially penetrated from one end of the device, surrounded by the field weakening planning device Formed in the magnetic field space.

7. The field weakening planning apparatus according to claim 6, wherein the magnetic source is a direct current coil, a permanent magnet, or a combination thereof.

The weak magnetic planning device according to claim 6 or 7, wherein the weak magnetic planning device is a DC single coil, a DC coil combination, a permanent magnet sleeve, a permanent magnet magnetic tile combination or a permanent magnet rod. One of the combinations.