Device for determining the uniformity of mechanical properties of articles made of ferromagnetic materials and detecting regions of abnormal hardness therein

Abstract

The invention relates to the field of testing the physical properties of articles and materials and can be used for detecting regions of abnormal hardness and other physical and mechanical surface properties of articles manufactured from ferromagnetic materials, in particular steel sheets, rails, pipes and bars. The technical result of the invention is that of ensuring the necessary measuring accuracy and improving testing efficiency, thereby rendering the claimed device for determining the uniformity of mechanical properties of articles made of ferromagnetic materials suitable for use in testing metal products for the presence of abnormal hardness while on a production line. Proposed is a design for a device for determining the uniformity of mechanical properties of articles made of ferromagnetic materials and detecting regions of abnormal hardness therein. Use of the claimed design makes it possible to prevent the negative effect of regions with residual magnetism in test objects by means of the simultaneous analysis of several frequency components of a signal.

Description

[0001] DEVICE FOR DETERMINING THE HOMOGENEITY OF MECHANICAL PROPERTIES OF PRODUCTS MADE OF FERROMAGNETIC MATERIALS AND DETECTING ZONES WITH ANOMALOUS HARDNESS IN THEM

[0002] Field of technology

[0003] The invention relates to the field of monitoring the physical properties of products and materials, and can be used to detect zones with anomalies in hardness and other physical and mechanical properties of the surface of products made from ferromagnetic materials, in particular steel sheets, rails, pipes, rods.

[0004] Prior art

[0005] It is well known that there is a correlation between the mechanical and magnetic / electromagnetic properties of metals.

[0006] Devices for eddy current determination of the structure and mechanical properties of metal products are widely known. Being universal devices to a certain extent, they, as a rule, do not take into account the specifics of rolling production, which forms anisotropy of the mechanical and electromagnetic properties of metal, uneven scale, local deviations from the nominal shape and surface defects. Therefore, these devices are practically unsuitable for operation as part of multichannel systems for high-performance control of the mechanical properties of metal in industrial production conditions. A device is known for determining the homogeneity of the mechanical properties of metal products and detecting zones with abnormal hardness in them (patent for invention RU2690074C1, published 05 . 04 .2019), which contains a roller table for moving the test object (TO) during the test process, a demagnetizer, a system for compensating for the influence of the working gap, and a set of at least two electromagnetic sensors (ED), each of which contains at least one working coil (WC) and one auxiliary coil, wherein the frequency F of the maximum in the spectrum of the magnetic field generated by both coils is selected from the ratio F < 0.8 x Fc, where Fc is the frequency at which the change in the inductance of the corresponding coil when the ED approaches the TO changes direction from positive (the inductance increases when approaching the TO) to negative (the inductance decreases when approaching the TO).At least two EDs on a common substrate, and therefore operating in approximately the same conditions, allow for comparison and joint analysis of the data obtained from these sensors, thereby significantly increasing the reliability of eddy current testing, especially when detecting compact, relatively small areas with increased hardness. In addition, each ED during scanning allows for recording hardness gradients detected by sharp changes in the measured values ​​when the ED moves relative to the OC.

[0007] The disadvantage of the known device is that when using the above ratio, both coils react equally to the working gap: as it increases, the inductance of the coils decreases. It is in these cases that changes in the electromagnetic properties of the OC can easily be confused with a random change in the gap between the OC and the ED, with the presence of residual magnetization, or with the influence of a thick scale spot on the corresponding section of the OC.

[0008] The closest in technical essence to the claimed design is a device for detecting zones with non-uniform physical properties in rolled metal products (patent for invention RU276793901, published 03.22.2022), selected as a prototype.

[0009] The known device comprises a roller table for moving the test object (TO) during the test process, a system for compensating for the effect of the working gap, a generator control unit and a set of electromagnetic sensors designed to generate measuring electromagnetic pulses in the TO, closing through the TO, and registering electrical signals. In the known device, the generator of measuring electromagnetic pulses performs a periodic inversion of the phase of the measuring pulses, and this device also contains a unit for analyzing and comparing signals obtained when the same section of the TO is exposed to electromagnetic pulses with opposite initial phases. The sensor of this device contains at least one excitation coil connected to a source of direct and inverted current pulses, at least one measuring coil having an electromagnetic (transformer) connection with the excitation coil, and,the functions of the generator and measuring coils can be combined, a U-shaped core on which the excitation and receiving coils are located and which forms a closed magnetic circuit with the OC to the maximum extent, a source of current pulses flowing through the excitation coil, which carries out a periodic inversion of these pulses, leading to a corresponding inversion of the direction of the currents through the excitation coil, wherein the current pulses passing through the excitation coil have a component of magnetization of the OC, as well as a measuring component, the frequency of which can change from pulse to pulse due to a forced change in the parameters of the oscillatory circuit, a measuring unit connected to the measuring coil, which analyzes signals corresponding to at least one direct and at least one inverted current pulse through the excitation coil on each examined section of the product, wherein this analysis is carried out in the time domain.

[0010] The device selected as a prototype has proven itself well in the control of hot-rolled sheet metal, provided that the control is performed outside the production flow. However, a disadvantage of this device is that in some cases it is necessary to use a demagnetizer, since not all steel grades provide complete suppression of interference associated with their residual magnetization. Another disadvantage of the prototype is that the device's performance does not allow for control in the production flow, since to obtain additional data that ensure increased interference protection and accuracy in determining the mechanical properties of the OC, it is necessary to change the parameters of the oscillatory circuit of the sensors, which requires additional cycles to generate signals, leading to an increase in the time for taking measurements.Increasing the frequency of pulse sending, in turn, leads to an increase in the temperature of the sensors and an uncontrolled change in their parameters, which is also a factor limiting the speed (performance) of control. Thus, one of the disadvantages of the device selected as a prototype is that its use does not exclude the negative effect of the magnetic field on the measurement result, as a result of which it is impossible to refuse to use a demagnetizer. Another disadvantage of this technical solution is the need for forced change in the parameters of the oscillatory circuit to change the frequency of the measuring component of the signal, which requires additional time, which leads to a decrease in the performance of control. Another disadvantage of the known device is the uncontrolled change in the parameters of the oscillatory circuit associated with the temperature drift of the sensor parameters, which leads to a decrease in the accuracy of measurements.

[0011] Disclosure of invention

[0012] The technical problem solved by the claimed invention is the need to completely abandon the use of a demagnetizer, as well as to ensure higher control performance compared to the prototype.

[0013] The technical result is to ensure the required measurement accuracy, increase the productivity of control and, as a consequence, the possibility of using the device to determine the homogeneity of the mechanical properties of products made of ferromagnetic materials for monitoring metal products for the presence of hardness anomalies in the production flow.

[0014] The specified technical result is achieved due to the design of a device for determining the homogeneity of the mechanical properties of products made of ferromagnetic materials and detecting zones with anomalous hardness in them, which includes: a sensor containing at least one excitation coil (EC) connected to a source of direct and inverted current pulses, at least one measuring coil (MC) having a strong electromagnetic connection with the EC, as well as a U-, П-, С- or Ш-shaped core on which the EC and MC are located and forming a magnetic circuit with the test object (TO), wherein the functions of the EC and MC can be combined in one coil; a source of current pulses that performs a periodic inversion of the generated pulses, leading to a corresponding inversion of the direction of the currents flowing through the EC, wherein the base B of the current pulses satisfies the condition:

[0015] B = dT x dF >1 (1), where: dT is the effective signal duration; dF is the effective signal spectrum width.

[0016] - a measuring unit connected to the IR, performing an analysis of signals corresponding to at least one direct and at least one inverted current pulse flowing through the VC on each investigated section of the OC, wherein the measuring unit additionally contains a unit for converting received signals from the time domain to the frequency domain, and a spectrum analyzer (SA) connected to it in series, wherein, in the spectrum of each received IR signal, the amplitudes of both its high-frequency and low-frequency components are measured, based on the analysis of which the influence of interfering factors is suppressed and the hardness of the test object is determined.

[0017] In addition, the sensor can be additionally equipped with a cooling system.

[0018] Data analysis can be carried out, for example, in the following way: by selecting from the spectrum of received signals corresponding to both direct and inverted current pulses, pre-selected frequency components fi...f n , measuring their amplitudes Afid . . .Afi n and Afii . . .Af n i, where indices 1...n correspond to the serial number of the frequency component, and indices d and i mean that they belong, respectively, to the direct and inverted current pulses through the VK,

[0019] - subsequent calculation of the parameter R = R (Afid . . . Af nd, Afu . . . Afni ) , which correlates with the hardness of the test object and has a minimal correlation with interfering factors, in particular, with changes in the gap and magnetization of the test object, and the type of formula by which the parameter R is calculated is determined experimentally , using samples of the material subject to testing . The parameter R can be calculated, for example, using the following formula : Where : “maximum amplitude in the spectrum of the direct signal; “ maximum amplitude in the spectrum of the inverted signal;

[0020] - the amplitude of the frequency component fn of the direct signal; amplitude of frequency component fn inverted signal; > . f , - weighting factors selected empirically.

[0021] Next, the hardness value is calculated for the area of ​​the OK being studied, which is usually carried out by multiplying the R value by the corresponding scale factor, which, in turn, depends on the specific properties of each measuring channel and is determined during calibration of the measuring system.

[0022] Unlike the prototype, in which only the high-frequency part of the received signal is used for measurements, in the claimed design the entire signal is analyzed, including its low-frequency part, and the analysis is performed in the frequency domain, not in the time domain. Thus, a distinctive feature of the operation of the device of the claimed design is that the base B of the analyzed signal satisfies the condition B>1, and that several frequency components of the signal are analyzed simultaneously.

[0023] As a result of using the claimed design of the device for determining the homogeneity of the mechanical properties of products made of ferromagnetic materials and detecting zones with anomalous hardness in them, the negative influence of OK sections with residual magnetization is eliminated, thanks to the simultaneous analysis of several frequency components of the signal.

[0024] Different frequency components allow to separately identify the influence on the calculation result of both the OC properties and the influence of interfering factors, and, accordingly, to exclude their influence on the final result. In addition, since the analysis of frequency components is performed simultaneously, there is no need to perform a forced change in the parameters of the oscillatory circuit, which ensures an increase in the frequency of pulse sending, and the additional use of the sensor cooling system allows to stabilize the temperature mode of its operation and further increase the frequency of pulse sending, which, ultimately, allows to significantly increase the productivity of OC control (for example, hot-rolled sheets) in the production flow.

[0025] Brief description of the drawings

[0026] Fig. 1 shows a block diagram of the claimed device for determining the homogeneity of mechanical properties of metal products and detecting zones with abnormal hardness in them.

[0027] Fig. 2 shows a schematic cross-section of the sensor.

[0028] Fig. 3A and Fig. 3B show the types of sensor signals (direct and inverted, respectively).

[0029] Fig. 4 shows an example of a sequence of signals generated by a current pulse source connected to the sensor coil.

[0030] Fig. 5 shows a view of the first sample 16 in its initial state.

[0031] Fig. 6 shows a view of the first sample 16 with “interfering” factors on its surface.

[0032] Fig. 7 shows a section of the first sample 16 with scale removed.

[0033] Fig. 8 and 9 show the results of scanning the first sample 16 in the initial state and with “interfering factors”.

[0034] Fig. 10 shows the second sample of 21 sheet pipe steel.

[0035] Fig. 11 shows the second sample 21 before magnetization.

[0036] Fig. 12 shows the second sample 21 after magnetization. Fig. 13 shows a visualization of the magnetic field on the magnetized second sample 21.

[0037] Embodiments of the invention

[0038] The claimed design is explained by images, which indicate the following positions:

[0039] 1 - a device for determining the homogeneity of mechanical properties of products made of ferromagnetic materials and detecting zones of anomalous hardness in them;

[0040] 2 - sensor;

[0041] 3 - source of current pulses;

[0042] 4 - measuring block;

[0043] 5 - control object (CO);

[0044] 6 - sensor body 2;

[0045] 7 - excitation coil (EC) of sensor 2;

[0046] 8 - measuring coil (IR) of sensor 2,

[0047] 9 - ferromagnetic core of sensor 2;

[0048] 10 - housing cover 6 of sensor 2;

[0049] 11 - substrate of the housing 6 of the sensor 2;

[0050] 12A, 12V - direct and inverted signals;

[0051] 13 - magnetizing component of direct or inverted signal 12A, 12V;

[0052] 14 - measuring component of direct or inverted signal 12A, 12V;

[0053] 15 - sensor 2, installed on the laboratory scanner; 16 - first sample;

[0054] 17 - section of the first sample 16, simulating a gap;

[0055] 18 - section of the first sample 16 with removed scale;

[0056] 19 - the area of ​​location of section 17 of the first sample 16, simulating a gap;

[0057] 20 - area of ​​location of section 18 of the first sample 16 with removed scale;

[0058] 21 - second sample;

[0059] 22 - hard spot;

[0060] 23 - the area where the hard spot 22 is located.

[0061] Fig. 1 shows a block diagram of the claimed device for determining the homogeneity of mechanical properties of metal products and detecting zones with abnormal hardness 1 in them, which includes a sensor 2, a current pulse source 3 and a measuring unit 4.

[0062] Fig. 2 shows a schematic section of sensor 2, which includes housing 6, VK 7 and IR 8. In this case, sensor 2 can be designed with the possibility of its connection directly to OK 5 or it can be placed at a given distance S from the surface of OK 5, wherein said distance S from the surface of OK 5 to sensor 2 must satisfy the condition S ≥ 0 mm, which can be constant or variable.

[0063] The housing 6 of the sensor 2 includes a cover 10 and a substrate 11 connected to the cover 10 of the housing 6.

[0064] The exciting coil 7 and the measuring coil 8 of the sensor 2 are placed on the same substrate 11 and include a common ferromagnetic core 9 , in this example made U-shaped. The core 9 forms with the OK 5 a closed magnetic circuit to the maximum extent. The source of current pulses 3 is connected to the VK 7 of the sensor 2 . The current pulse is fed to the VK 7 of the sensor 2 , in which a wideband signal 12 arises, which includes the first component 13 (the magnetizing component) and the second component 14 (the measuring component) sequential in time. In this case, the source of current pulses 3 is designed with the possibility of generating both a direct and an inverted current pulse . As a result, the signal 12 will be either direct, as it is designated in Fig. 3A by position 12A, or inverted, as it is designated in Fig. 3B by position 12B .

[0065] An important feature of the signals 12 generated by VK 7 is that their base B satisfies the condition: B = dT x dF > 1, where dT is the effective duration of signal 12, and dF is the effective width of the spectrum of signal 12.

[0066] The inversion of the shape of the magnetic field pulses in the magnetic circuit and in the section of the OK 5 connected to it ensures at least partial demagnetization of the surface layer of the OK 5, which ensures partial compensation for the influence of the residual magnetic field.

[0067] The measuring unit 4 is connected to the IR 8 of the sensor 2 and is designed with the possibility of receiving and processing signals arising in the IR 8 of the sensor 2, the appearance of which is caused by the presence of electromagnetic connections between the VK 7 of the sensor 2, the IR 8 of the sensor 2, and the OK 5.

[0068] The measuring unit allows analyzing the signal 12 as a whole, both its magnetizing component 13 and the measuring component 14. In doing so, it includes a Fourier analyzer and converts the received signal 12 from the time domain to the frequency domain. For example, the amplitudes of various frequency components of the signal 12 spectrum, as well as the width and central frequencies of various frequency components, can be used as informative parameters in signal analysis. It is also important that both the direct 12A and the inverted 12B signals obtained on the same section of the OK 5 are analyzed together. Analysis of various frequency components of the signal 12 received by the IR 8 sensor 2 allows determining the current gap between the sensor 2 and the OK 5 and suppressing the influence of other interfering factors, in particular the residual magnetic field, for any steel grade, as well as identifying parameters that characterize the physical properties of the OK 5 material, which allows increasing the accuracy of measurements.

[0069] Based on the experimental data, a direct proportional relationship was established between the frequency of component 14 of signal 12 and the hardness of the OK surface 5, i.e. the higher the frequency of the observed signal, the harder the surface located under sensor 2. This relationship is valid if sensor 2 is located on the same material, different parts of which have different hardness.

[0070] Measuring block 4, based on the data collected during the control process, allows calculating the parameter R using formula (2). Parameter R, in turn, correlates with the value of hardness OK 5, and accordingly, can be converted into hardness units.

[0071] The claimed device operates as follows.

[0072] Sensor 2 is placed at a specified distance from the surface of the OK 5.

[0073] By means of a current pulse source 3 (Fig. 1), connected to the coil 7 of the sensor 2, a sequence of multiple signals 12 is generated: alternating direct signals 12A and inverted signals 12B (an example of a signal sequence is shown in Fig. 4).

[0074] The parameters of the current pulses (duration and amplitude) that cause the appearance of signals 12 are selected experimentally for each OK sample (steel grade) in such a way as to ensure local demagnetization of a thin surface layer of the material in the area where the measurements are performed.

[0075] The parameters of signals 12 during the testing process change depending on the properties of the OK 5 , the size of the gap between the sensor 2 and the OK 5 , and the presence of a residual magnetic field . Signals 12 are received by means of the IR 8 . By means of the measuring unit 4 , the informative parameters of the received signals 12 are analyzed, in particular, their shape, and the obtained parameter values ​​are compared with the parameter values ​​obtained during calibration , and the parameter R is calculated, correlating with the hardness value . The dependence between the parameter R and the hardness value when calculated using the proposed formula ( 2 ) is inversely proportional (the higher R, the lower the hardness ). During the calibration process, the dependence of the measured signal parameters on the gap for a given specific material is established, that is, the values ​​of the weighting coefficients Ki ... K are selected nin formula (2), which allows the device to be calibrated in such a way as to compensate, for example, for random changes in the gap, the influence of residual magnetization, and at the same time to see those areas where the change in signal parameters is associated with a change in hardness.

[0076] The claimed design has passed experimental tests.

[0077] Experiment 1: Investigation of the influence of gap and scale on the testing results.

[0078] The first sample of 16 sheet pipe steel with dimensions of 300x300 mm, having a surface hardness in the range from 170 to 180 Hvl O (the test was performed using a manual dynamic hardness tester) was used to conduct the experiment. A laboratory scanner containing the claimed device was used to conduct the experiment.

[0079] The first sample 16 was examined twice: the first time in its original state (Fig. 5), the second time after adding “interfering” factors to its surface:

[0080] - section 17, simulating a gap, equipped with pieces of paper glued to its surface with tape. The total height of the gap was 0.3 mm, which corresponds to the actual range of gap variation during the inspection of real OK;

[0081] - section 18 with removed (stripped) scale.

[0082] The appearance of the sample with “interfering” factors on its surface is shown in Fig. 6, the area with removed scale is shown in

[0083] Fig. 7. The results of scanning the first sample 16 in the initial state and with "interfering factors" are presented in Fig. 8 and Fig. 9. In the right part of Fig. 8 and Fig. 9 presented above, there is a graph of the change in the parameter R, whereby the position 19 denotes the area of ​​the section simulating the gap of the first sample 16, and the position 20 denotes the area of ​​the location of section 18 of the first sample 16 with removed scale. The change in the gap does not have a noticeable effect on the change in the parameter R, just like section 18 with removed scale.

[0084] Experiment 2: Magnetic field suppression and detection of solid spots.

[0085] The second sample 21 (Fig. 10) of sheet pipe steel with dimensions of 300x300 mm, having a surface hardness in the range from 180 to 190 HvlO (the test was performed using a manual dynamic hardness tester), as well as hard spots 22 formed on its surface using a laser. The hardness of hard spots 22 is about 270 HvlO. For the subsequent magnetization of sample 21, a crane permanent magnet with a lifting capacity of 1000 kg was used.

[0086] Sample 21 was examined twice: the first time in the initial state, before magnetization (see Fig. 11), and the second time after magnetization (see Fig. 12). Fig. 13 shows a visualization of the magnetic field on the magnetized second sample 21. In Fig. 11, Fig. 12, positions 23 indicate the areas of location of hard spots 22. The scanning results demonstrate the ability of the claimed device both to detect hard spots 22 and to effectively suppress the influence of the residual magnetic field.

[0087] Thus, the solution to the technical problem and the achievement of the declared technical result using the claimed technical solution were confirmed experimentally.

Claims

CLAUSE OF INVENTION 1. A device for determining the homogeneity of mechanical properties of products made of ferromagnetic materials and detecting zones with anomalous hardness in them, comprising: a sensor containing at least one excitation coil (EC) connected to a source of direct and inverted current pulses, at least one measuring coil (MC) having a strong electromagnetic connection with the EC, as well as a U-, П-, С- or Ш-shaped core on which the EC and MC are located and forming a magnetic circuit with the test object (TO), wherein the functions of the EC and MC can be combined in one coil; a source of current pulses that performs a periodic inversion of the generated pulses, leading to a corresponding inversion of the direction of the currents flowing through the EC;a measuring unit connected to the IC, which analyzes signals corresponding to at least one direct and at least one inverted current pulse flowing through the VK on each investigated section of the OK, characterized in that the base B of the current pulses through the corresponding excitation coil satisfies the condition:; B = dT x dF >1, where: dT is the effective signal duration; dF is the effective signal spectrum width, and the device additionally contains a unit for converting received signals from the time domain to the frequency domain, and a spectrum analyzer (SA) connected to it in series, wherein, in the spectrum of each received IR signal, the amplitudes of both its high-frequency and low-frequency components are measured, based on the analysis of which the influence of interfering factors is suppressed and the hardness of the test object is determined.

2. The device according to paragraph 1, characterized in that the sensor is additionally equipped with a cooling system.

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