RU2767939C1 - Device for detecting zones with inhomogeneous physical properties in rolled metal products - Google Patents

Abstract

FIELD: rolling.

SUBSTANCE: invention relates to the field of control of the physical properties of products and materials and can be used to detect areas with surface hardness anomalies of rolled steel products. A device for detecting zones with inhomogeneous physical properties in rolled metal products contains a roller table for moving the control object during the control 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 control object, closing through the control object, registering electrical signals, a generator of measuring electromagnetic pulses performs periodic phase inversion of measuring pulses, moreover, the device also contains a block for analyzing and comparing signals received when exposed to the same section of the object of control by electromagnetic pulses with opposite initial phases.

EFFECT: increase in the accuracy of determining the uniformity of the mechanical properties of products.

4 cl, 1 dwg

Description

The invention relates to the field of monitoring the physical properties of products and materials, and can be used to detect areas with anomalies in hardness and other physical properties of the surface of rolled steel products, such as sheets, rails, pipes and bars.

Known devices that implement a method for monitoring the uniformity of the mechanical properties of sheet, long products and pipes according to the RF patent for the invention No. 2258217, publ. 08/10/2005, IPC G01N29/04, including the use of blocks of electromagnetic-acoustic transducers placed on the surface of the controlled product, excitation in the product and reception of elastic vibrations, reception and measurement of the travel time of ultrasonic pulses polarized along and across the rolling direction. Moreover, at each section of the rolled unit, impulses of transverse waves are simultaneously excited and received, which are mainly polarized along and across the direction of rolling, the time of arrival of bottom pulses reflected from the opposite wall of the rolled unit is measured, for each section of the rolled unit, at least one of the informative values is calculated relationships that carry information about the homogeneity of mechanical properties.

Also known is a device for ultrasonic testing of the strength characteristics of materials in dynamic mode according to the RF patent for the invention No. 2231055, publ. 06/20/2004, IPC G01N29 / 00, containing a generator of high-frequency electrical oscillations, two electromagnetic-acoustic transducers, each of which consists of a flat inductor located parallel to the surface of the product, and a magnetic system connected in series: a high-frequency amplifier, a detector, a video amplifier, an indicator and a sweep generator, and the second input of the indicator is connected to a sweep generator connected to a generator of high-frequency electrical oscillations, characterized in that the electromagnetic-acoustic transducer is installed on one side of the controlled product, and the polarization direction of one electromagnetic-acoustic transducer coincides with the rolling direction, and the second - perpendicular to it, and in addition to the output of the video amplifier, a serial circuit is connected from a time interval meter, a divider of the indicated time intervals and a recorder.

Known devices allow continuous automatic high-performance control of the mechanical properties of materials and products using several lines of electromagnetic-acoustic transducers, allowing each unit to control a fairly wide area of the object of control (OK).

The disadvantages of the known devices include their high sensitivity to deviations in temperature and geometric dimensions of the OK, as well as to the scale layer on its surface, which leads to a significant decrease in the reliability of measurements.

The attenuation of elastic waves, which, theoretically, also carries information about the physical properties of the OC, is measured, as a rule, also with large and unavoidable errors, due mainly to the same reasons. In addition, the use of bulk (longitudinal and transverse) elastic waves makes it possible to obtain only integral, averaged over the path of ultrasonic pulses, information about the physical properties of the OC.

Anomalies in the hardness of the surface layers of the metal are detected very unreliably. Devices for eddy current control of the structure and mechanical properties of metal products are widely known. It is also known that there is a correlation between the mechanical and magnetic/electromagnetic properties of metals. Being, to a certain extent, universal devices, they, as a rule, do not take into account the specifics of rolling production, which forms a pronounced anisotropy of the mechanical properties of the metal. In addition, these devices are practically unsuitable for operation as part of multichannel high-performance control systems in industrial production.

First, with a large number of sensors (several hundred of them may be required at the same time), a serious problem may be their low operational stability associated with abrasion and high temperature of the test object.

Also, dirt, debris, flaking scale, often found on the surface of the rolled products, will inevitably and uncontrollably change the gap between the sensors and OK. This is a very undesirable phenomenon, since any system for compensating for the effect of changing the gap has an error that can significantly reduce the reliability of the control.

Another disadvantage of eddy current testing systems is their mutual influence. A very dense arrangement of the working coils is required for continuous testing of sheet metal. Independent registration of changes in the amplitude and/or phase of a relatively low-frequency harmonic or quasi-harmonic signal in different coils takes time, and the exclusion or, at least, a significant reduction in their mutual electromagnetic influence in some cases can be a serious problem.

A significant disadvantage of these devices is also their low noise immunity, associated with the inevitable in the conditions of industrial production interfering factors, in particular, with the negative influence of the almost inevitable fluctuations of the residual magnetic fields on the surface of the OC.

A device is known for determining the uniformity of the mechanical properties of metal products and detecting zones with abnormal hardness in them according to the RF patent for the invention No. 2690074, publ. 04/05/2019, IPC G01N27 / 82, selected as a prototype, containing a roller table for moving the test object (OC) in the control process, a demagnetizer, a working gap effect compensation system, and a set of at least two electromagnetic sensors (ED), each of which contains at least one working coil, a housing, characterized in that each EM is an assembly of at least two working coils (RC) wound on U-shaped cores, and the lines connecting the poles of each core are oriented parallel to each other in such a way that that the alternating magnetic field generated by the coils closes through the OK, either along or across the rolling direction, and the frequency F of the maximum in the spectrum of the magnetic field generated by the ED is selected from the relation: F ≤ 0.8 × Fc, where Fc is the frequency at which the change in the inductance of the RC when the ED approaches the OK, it changes direction from positive (inductance increases as it approaches) to negative (inductance as drops when approaching), and the gap compensation system additionally contains a system for supplying compressed air to the EM, and each EM additionally contains at least one hole made in the sole of the EM (from the side of the test object), and which serves to release air from the sole of the EM and create an air cushion in the space between OK and ED, and the area S of the sole of the ED satisfies the condition: S ≥ 5000/P, where S is the area of the sole of the ED in mm ² ; P is the air pressure at the EM inlet, in bars, the shape of the sole corresponds to the shape of the OC, and each EM additionally contains a device for pressing it against the control object with a given force, which ensures the stabilization of the gap between the OC and the EM at a given value.

This well-known device has proven itself well in the production of hot-rolled sheet metal: the ED groups and the RC lines located in them are protected both from mutual influence and from the aggressive effects of OK.

The main disadvantage of the known device, as well as all similar devices, is the mandatory presence of a low-frequency demagnetizer in its composition. This bulky and very expensive unit significantly reduces the productivity of the station for electromagnetic control of the mechanical properties of the metal. This is due to the fact that steel sheets are transported during their production, as a rule, by magnetic cranes. The residual magnetization caused by them significantly reduces the reliability of the results of electromagnetic testing of sheets, since the reaction of the measuring system to the magnetized area often turns out to be completely similar to the reaction to the area with anomalous hardness.

In order to qualitatively demagnetize the sheet to its entire depth, the use of very low frequencies of the operating current of the demagnetizer is required - up to 0.5 Hz. For reliable demagnetization, each section of the sheet must be exposed to a slowly changing electromagnetic field over several periods of the operating frequency of the demagnetizer. This causes significant time losses in the production of sheets for special purposes. But even in a well-demagnetized sheet, areas with non-zero residual magnetization may appear, due to various factors inherent in real metallurgical production. As the experience of operating the installation of electromagnetic testing of rolled products has shown, areas with spontaneous magnetization are a serious hindrance in the conduct of electromagnetic testing, and often lead to re-rejection.

The technical problem solved with the help of the claimed invention is the lack of reliability and accuracy in determining the uniformity of the mechanical properties of metal products obtained by rolling using known devices.

The technical result of the present invention is to increase the reliability, productivity and accuracy of determining the uniformity of the mechanical properties of products obtained by rolling.

The specified technical result is achieved by the fact that the device for detecting zones with inhomogeneous physical properties in rolled metal products contains a roller table for moving the test object in the control process, a system for compensating the influence of the working gap, a generator control unit, and a set of at least two electromagnetic sensors, each of which is an assembly of at least two working coils wound on U-shaped cores, designed to generate measuring electromagnetic pulses in the control object, closing through the control object, either along or across the rolling direction, and recording electrical signals due to the influence of the control object , taken from the same working coils, or from separate measuring coils wound on the same U-shaped cores, with capacitors connected in parallel to the working and / or measuring coils, the capacitance of which determines the operating frequency of the damped oscillations, while m generator of measuring electromagnetic pulses performs periodic inversion of the phase of the measuring pulses, and the device also contains a unit for analyzing and comparing the signals obtained when the same area of the control object is exposed to electromagnetic pulses with opposite initial phases.

In addition, the specified device may additionally contain at least one magnetizing current pulse generator connected to the working coils, and ensuring the passage through them of bias current pulses of a given amplitude and duration, and of alternating polarity, which, as a rule, precede the measuring pulses.

In addition, the functions of the generator of measuring pulses and the generator of bias current pulses can be performed by the same generator, moreover, its operating modes at one time or another are determined by the algorithm implemented in the generator control unit.

In addition, each working or measuring coil may contain at least one additional capacitor, and at least one electronic switch connected to both the working or measuring coil and the additional capacitor, and providing a periodic change in the resonant frequency of the working circuit and its transition from one frequency to another.

As a result of using the proposed design of the device for detecting zones with inhomogeneous physical properties, the frequency spectrum of informative signals is expanded, which makes it possible to obtain additional information about the state of the OK, and the noise immunity during monitoring is also increased. In addition, the claimed device makes it possible to eliminate or at least significantly reduce the negative impact of OC sections with residual magnetization. This leads to the possibility of either abandoning the use of a demagnetizer or significantly reducing its size and cost.

Thus, due to the proposed design of the device for detecting zones with inhomogeneous physical properties, the reliability, productivity and accuracy of determining the uniformity of the mechanical properties of rolled metal products are increased.

As an example, in FIG. 1 shows a functional diagram of the measuring part of the proposed device, which indicates:

K1 - K4 - current control keys;

L - measuring coil;

C1 and C2 - loop capacitors;

K5 - key for connecting capacitor C2;

D1, D2 - protective diodes;

S1 - S5 - control signals.

The measuring coil L, wound, for example, on a U-shaped core, is placed in an inductive sensor located near OK, and having with it. The core can also have a different shape, which also provides electromagnetic coupling of the coil with OK.

The scheme works in several possible ways. The following are examples of the three main options for how the circuit works.

Option 1

The magnetizing pulse is combined with the pulse that starts oscillations in the circuit.

With the simultaneous short-term closure of keys K1 and K3, carried out using control signals S1 and S3, voltage from the voltage source U will be applied to the L-C1 circuit. a damped oscillatory process with an initial phase Ф1 will begin in the circuit, the parameters of which, among other things, are determined by the physical properties of the OK. The first, triggering, most intense "portion" of current through the coil L, as the initial component of the oscillatory process, is, in fact, a magnetization pulse. As a reaction to this current pulse, at its sufficient intensity, there will be a partial rearrangement of the magnetic domains on the OC surface, and, as a result, some change in the electromagnetic properties of the OC surface layer, in particular, its magnetic permeability.

After completion (attenuation) of the oscillatory process described above, with the help of control signals S2 and S4, a short-term closure of the second pair of keys - K2 and K4 is carried out. The voltage from the voltage source U will be again applied to the circuit L-C1, but in the opposite direction compared to the previous case. If the time of the closed state of the switches K1 and K3 is significantly less than the period of natural oscillations of the circuit L-C1, then the damped oscillatory process will again begin in the circuit, but this time with the initial phase F2, opposite to the phase F1.

The pair of damped pulses described above, after its sequential digitization, is fed to the device for analyzing and comparing the signals obtained when currents flow through the same section of the OK with two opposite initial phases. If the OK is not magnetized, then these signals will have almost identical measured characteristics: period, amplitudes, damping decrement, etc. The magnetized section of the OK will cause asymmetry of the received signals, the degree of which depends on the magnitude and direction of the residual magnetic field vector. Note that the residual field vector, as a rule, is parallel to the “easy” magnetization direction (most often, this is the rolling direction), and, taking into account the orientation of the U-shaped coil core L, which also coincides with the rolling direction, will either add up with the initial field of the coil, or subtracted from it.

The greater the difference in the ratio of the numerical values of the parameters of the same name obtained by their measurements in different phases of the initial current from unity, the greater the residual magnetization. These relationships are the basis for developing corrective actions on the measured parameters.

For example, the ratio of the numerical values of the periods T1 and T2 of damped processes measured in phases F1 and F2 should, as a rule, be equal to one - regardless of the gap between the sensor and the OC, its temperature, roughness, electrical conductivity, and other physical characteristics.

The only exception is the residual magnetization of the OC section, which immediately leads to a deviation of this ratio from unity. Instead of the period, or in addition to it, you can use other quantities that characterize the oscillatory process, for example, the damping or amplitude decrement.

This measurement process is repeated in a cycle:

- Magnetization in phase F1 and, at the same time, starting the oscillatory process in the initial phase F1;

- Magnetization in the phase F2 and, at the same time, the launch of the oscillatory process in the initial phase F1.

Option 2

To enhance the effect of pre-magnetization of the OK surface, it is possible, using the same keys K1-K4, to pass high-intensity current pulses through the coil L. To do this, the duration of opening the keys must be sufficiently large.

The control cycle in this case will look like this:

- Magnetization in phase F1;

- Measuring pulse in phase Ф1;

- Magnetization in phase F2;

- Measuring pulse in phase F2.

As a response to intense magnetizing pulses of different polarity, a more intense (partial) reorientation of domains on the OC surface will occur, the degree of which will depend on the phase of the magnetization pulse. Thus, the contrast when measuring the parameters of the oscillatory process in one and the other direction will be expressed to an even greater extent than in option 1.

Option 3

Periodic change in the spectrum of the measuring signal. It is carried out by periodically connecting the capacitor C2 to the oscillatory circuit. At the same time, the observation of two oscillatory processes occurring at different frequencies makes it possible to significantly expand the set of informative parameters, and to an even greater extent increase the reliability and noise immunity of the electromagnetic control process.

A lower natural frequency F2 of the oscillatory circuit is provided by connecting a capacitor C2 to it, which is carried out by electronic switching of the key K5 (using the signal S5).

In this case, the measurement cycle may look like this:

- Magnetization in phase F1 (key K5 is open);

- Initiation of the measuring pulse in phase F1 at frequency F1 (key K5 is open);

- Initiation of the measuring pulse in phase F1 at frequency F2 (key K5 is closed);

- Magnetization in phase F2 (key K5 is open);

- Initiation of the measuring pulse in phase F2 at frequency F1 (key K5 is open);

- Initiation of the measuring pulse in phase F1 at frequency F2 (key K5 is closed);

There are also other options for using the above measuring circuit.

Claims (4)

1. A device for detecting zones with inhomogeneous physical properties in rolled metal products, containing a roller table for moving the test object in the test process, a system for compensating for the effect of a working gap, a generator control unit and a set of at least two electromagnetic sensors, each of which is an assembly of at least two working coils wound on U-shaped cores, designed to generate measurement electromagnetic pulses in the test object, closing through the test object, either along or across the rolling direction, and recording electrical signals due to the influence of the test object, taken from the same working coils, or from separate measuring coils wound on the same U-shaped cores, with capacitors connected in parallel to the working and / or measuring coils, the capacitance of which determines the operating frequency of the damped oscillations, characterized in that the generator of the measuring electrome magnetic pulses performs a periodic inversion of the phase of the measuring pulses, and the device also contains a block for analyzing and comparing the signals obtained when the same area of the test object is exposed to electromagnetic pulses with opposite initial phases. 2. The device according to claim 1, characterized in that it contains at least one magnetizing current pulse generator connected to the working coils, and ensuring the passage through them of bias current pulses of a given amplitude and duration, and alternating polarity, which, as a rule, precede measuring impulses. 3. The device according to paragraphs. 1, 2, characterized in that the functions of the measuring pulse generator and the magnetizing current pulse generator are performed by the same generator, moreover, its operating modes at one time or another are determined by the algorithm implemented in the generator control unit. 4. The device according to paragraphs. 1 - 3, characterized in that each working or measuring coil contains at least one additional capacitor and at least one electronic switch connected both to the working or measuring coil and to the additional capacitor, and providing a periodic change in the resonant frequency of the working circuit and the transition it from one frequency to another.

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