JPH0340338B2 - - Google Patents

Description

Claim 1: A step of magnetizing a part of a sample by a pulsed magnetic field so as to form a spot of a residual induction region magnetized to a saturation point in opposite directions, used for determining mechanical properties of the sample. A method for magnetically measuring the mechanical properties of a moving elongated ferromagnetic sample, comprising the step of determining the magnitude of the residual induction, converting the gradient of the residual induction into an electrical signal along the magnetized portion. and the magnitude of the residual induction is determined by selecting a pulse of one polarity indicating a change in residual induction between the regions from this signal and integrating the selected pulse. A method for magnetically measuring the mechanical properties of a moving elongated ferromagnetic sample.

2. A magnetizing pulse generator, a magnetizing coil surrounding the sample and arranged along the sample and connected in an antiparallel relationship to the output of the magnetizing pulse generator, and a residual induction coil surrounding the sample. In an apparatus for magnetically testing a moving elongated ferromagnetic sample, comprising a transducer connected to a measuring circuit connected to an indicator suitable for converting the slope of the ferromagnetic sample into an electrical signal, The measuring circuit comprises a key 5, an integrator 6 connected in series with the key and a comparator circuit 7 suitable for selecting the instant at which the output signal of the transducer 4 is taken to be zero; A moving elongated ferromagnetic sample, characterized in that a comparator circuit 7 has an input connected to said transducer 4 and its output is electrically connected to the control input of said key 5 A device for magnetically testing.

3 the electrical connection of the comparator circuit 7 with the control input of the key 5 is made through a control unit 8;
The output of the integrator 6 is connected to the other input of the control unit through a further comparator circuit 9 suitable for selecting the instant at which the output signal of the integrator 6 is zero. characterized in that it is connected to the other input of the integrating circuit 6 through a current generator 10 whose output is controlled;
Apparatus according to claim 2.

TECHNICAL FIELD The present invention relates to a method for non-destructive testing of materials and articles, and more particularly to magnetic testing for determining the mechanical properties of moving elongated ferromagnetic materials and apparatus for carrying out the same. Regarding.

BACKGROUND OF THE INVENTION The magnetic and mechanical properties of ferromagnetic materials are known, for example on the basis of the chemical composition and structure obtained during manufacture. The formation of the desired mechanical properties of the steel, such as hardness, ultimate strength, yield strength and malleability, can therefore be ensured by maintaining the stability of the chemical composition constants and the manufacturing process. Certain (within tolerance) changes in the chemical composition and the manufacturing process used alter the mechanical and magnetic properties, so that measurements of the magnetic properties allow for the determination of mechanical properties. A dependent correlation exists between these mechanical and magnetic properties. The best magnetic properties for the above purpose are coercive force and remanent induction (magnetism).

In the conventional method named ``Method of measuring residual magnetism'' (see Patent Specification No. 53-29109 accepted in Japan, International Classification G01N27/
68), the sample piece (plate) passes between two electromagnets, which are arranged in opposing relation on both sides of the sample plate, one at the top and the other at the bottom. . The electromagnets cause a magnetic trail to form within the test material, which magnetic trail extends in the direction of movement of the test material. A transducer mounted for movement along a path across the magnetic footprint is located at the same distance from the electromagnet. The signal from the transducer is used to determine the amount of residual magnetism in the sample plate. The test results obtained with this method are affected by the displacement of the test material due to vibrations, which affects the measurement accuracy.

Furthermore, the presence of moving parts makes this method even more difficult to perform and reduces its reliability.

In another previously known method entitled ``Method and apparatus for detecting the presence of magnetic anomalies in ferromagnetic and non-ferromagnetic materials'' (see British patent no.
No. 1498218, International Classification G01N27/86), the test material passes through an annular magnet, and the test material is magnetized by the magnetic field of the annular magnet. The parameters of the test material are determined by the magnitude of the signal formed in the detection coil under the action of a magnetic dipole placed in the test material. The amplitude that produces a signal representative of the test material is therefore proportional to the magnitude of the test material's magnetic dipole and velocity.

The dependence of the output signal on the speed of the test material mentioned above affects the accuracy of the method.

Furthermore, a method is known for magnetically inspecting a circular section of a moving ferromagnetic object, comprising a pulse generator suitable for generating magnetizing pulses with repeating pulses of variable frequency (see, Soviet invention Certificate No. 696369, May 11, 1979). The magnetic means are formed in the form of a solenoid arranged in anti-parallel relationship with the circuit of the pulse generator. A readout device is mounted inside one of the solenoids symmetrically about the axis of the solenoid. The readout device used is a conventional ferroprobe inclinometer placed in the circuit.
gradiometer), the sum of their output signals is taken. The field coil of the ferroprobe is connected to the excitation circuit through a power amplifier, and the measurement coil is connected to the input of a selective amplifier tuned to the second harmonic.

The mechanical properties of the materials are magnetically tested using the method described above as follows.

A sample piece passes inside a magnetizing solenoid and between a plurality of ferroprobe inclinometers. A pulsed current is passed through the coil of the magnetizing solenoid to form a magnetic symbol. The parameters of the pulses are selected to produce a maximum slope for the remanence region. The repetition frequency of the magnetizing pulses is selected depending on the speed of the moving specimen, so that there is no residual magnetic field in the second solenoid during the passage of the magnetic symbol.
The Ferroprobe inclinometer responds to a tilt, which is normal to the direction in which the residual magnetic field component is moving, and is representative of the mechanical properties of the specimen. If the sample pieces moving between the ferroprobes are evenly spaced from them, their signals are equal and the combined signal is equal to the sum of all signals. If the sample piece deviates from the centerline of its path of motion, the strength of the signal from the Ferroprobe placed on one side increases, while the strength of the signal from the Ferroprobe placed on the other side increases. decreases, but the sum of these signals can remain constant (at low vibration amplitudes) if there is no change in the mechanical properties of the specimen.

The method and apparatus described above do not eliminate the influence of vibrations on the accuracy of the test results over a sufficiently wide range and for the desired accuracy, since the dependence of the gradient of the remanence on the distance to the surface of the sample is non-linear. be.

On the other hand, the applicability of the method and device described above is limited to samples having a circular cross section.

DISCLOSURE OF THE INVENTION The present invention eliminates the effects of sample displacements caused by vibrations and sample velocity changes that affect test results, and ensures the determination of mechanical properties of samples of arbitrary cross-section with high accuracy. An object of the present invention is to provide a method and an apparatus for magnetically testing a moving elongated ferromagnetic material.

The object of the present invention is to magnetize a part of a sample by means of a pulsed magnetic field in opposite directions so as to form a spot of a residual induction region magnetized to a saturation point, in order to determine the mechanical properties of the sample. In accordance with the present invention, in a method for magnetically measuring mechanical properties of a moving elongated ferromagnetic sample comprising the step of determining the magnitude of residual induction to be used, The magnitude of the residual induction is determined by converting the slope of the induction into an electrical signal, selecting a pulse of one polarity from this signal that indicates a change in the residual induction between the regions, and integrating the selected pulse. is achieved by a method of magnetically measuring the mechanical properties of a moving elongated ferromagnetic sample in which the ferromagnetic sample is determined.

The present invention also provides a magnetizing pulse generator, a magnetizing coil that surrounds a sample, is arranged along the sample, and is connected in an antiparallel relationship to the output of the magnetizing pulse generator, and Magnetically testing a moving elongated ferromagnetic sample with a transducer connected to a measurement circuit surrounding the sample and connected to a suitable indicator for converting the gradient of residual induction into an electrical signal In accordance with the invention, the measuring circuit comprises a key, an integrator connected in series with the key, and a device suitable for selecting the point in time at which the output signal of the transducer is taken to be zero. a moving elongated ferromagnetic sample, comprising a comparator circuit, the comparator circuit having an input connected to the transducer, and an output thereof electrically connected to a control input of the key. This is accomplished by means of a device for magnetically testing.

The electrical connection of the comparator circuit with the control input of the key is preferably made through a control unit, and the output of the integrator is connected to another comparator suitable for selecting the point in time at which the output signal of the integrator is zero. connected through a circuit to the other input of said control unit;
Preferably, the other output of the control unit is connected to the other input of the integrating circuit through a controlled current generator. Such a variant of the proposed device is able to improve the reproducibility of test results in large ambient temperature differences and provides good noise immunity of the device.

The proposed method and device eliminate the effects of sample velocity and sample displacement due to vibrations on the accuracy of the test results, making it possible to expand the product range of magnetic testing. The test results obtained with the invention and the device are determined solely by the parameters of the residual induction spot and can therefore represent the mechanical properties of the sample with high precision.

[Brief explanation of drawings]

The invention will be explained in more detail below in connection with the embodiments shown in the accompanying drawings, in which FIG. Figure 1b illustrates the distribution of the residual induction gradient in the magnetic domain according to the invention, Figure 2 is the block diagram of the proposed device, and Figure 3 shows the transformer at different speeds of the sample according to the invention. 4 is a time chart illustrating the operation of the device shown in FIG. 2; FIG. 5 shows another variant of the proposed device; FIG. 6 is a time chart explaining the operation of the apparatus shown in FIG.

BEST MODE FOR CARRYING OUT THE INVENTION The essence of the invention will be made clear from the following description.
The sample is magnetized by a pulsed magnetic field to generate spots of residual induction. FIG. 1a illustrates the structure of this spot with regions magnetized to saturation in opposite directions and located close to each other along the sample. The function B=B(x) representing the structure of this guiding spot will be used later for the purpose of fully understanding the essence of the invention. If the sample is moving, the slope of the residual induction, expressed as the function F(x) = dB(x)/dx (Fig. 1b), is converted into an electrical signal ε = ε(t), where ε (t) is the induced electromotive force of the transducer for converting the above-mentioned slope into an electric signal. Such a transducer may be, for example, a measuring induction coil integrated in the proposed device described below.

Based on Faraday's law of induction, the induced electromotive force ε(t) in an induction coil is expressed as a time change in the amount of magnetic flux coupled to the coil, which is a given function φ.
(t).

ε(t)=−dφ(t)/dt Therefore, the integral of the function ε(t) in a given time interval (T ₁ , T ₂ ) is simply given by the function φ(t) at the instantaneous times T ₁ and T ₂ It is determined. From the Newton-Leibniz equation, it is as follows.

U=∫ ^T2 _T1 ε(t) dt=−∫ ^T2 _T1 dφ(t)/dtdt = φ(T ₁ )−φ(T ₂ ) According to the proposed method, the instantaneous time T ₁ corresponds to the passage of a portion of _the sample magnetized in _{one direction} (segment corresponds to the passage of the magnetized sample part through the transducer until (inverted). Therefore 1
Once a two-pole pulse is selected from the transducer signal, it is integrated to yield U=K[φ(T ₁ )−φ(T ₂ )] =K[φ(X ₂ )− φ(X ₁ )] =2K・φ=2K[∫ _s Brds] Here, φ(X ₂ )=φ(T ₁ )=φ is the instantaneous time T ₁ (when the integration starts), that is, the residual magnetic flux is is the _magnetic flux passing through the transducer in the time that crosses _{the division}
The instantaneous time T ₂ , i.e. the residual magnetic flux is divided into the sample section X ₁
is the magnetic flux passing through the transducer in time across , Br is the distribution function of the residual induction for the section, and K is a constant coefficient determined by the transducer parameters and the integrator.

The obtained relationship therefore does not include the axial displacement of the sample caused by vibrations over the entire area of the transducer, since the instantaneous time
This is because at T ₁ and T ₂ (as segments X ₂ and X ₁ ) the entire magnetic flux that is coupled to the coil is actually concentrated inside the specimen. The above relationship is independent of the speed of the sample moving through the transducer. The output signal is the amount of residual induction in the specimen and the shape of its division (in other words, the amount of residual magnetic flux in the specimen)
Determined only by.

The proposed method can be implemented by the apparatus illustrated in FIG. The device comprises a magnetizing pulse generator 1, the output of which is connected in parallel to a magnetizing coil 2. The coil 2 is arranged along the sample 3 and surrounds the sample. The distance between the magnetic coils is selected depending on the actual situation in which the proposed method is implemented. The device further includes a transducer that converts the residual induced gradient into an electrical signal. This transducer is preferably designed in the form of a measuring coil 4 . This coil surrounds the sample 3 and is connected to a measurement circuit comprising a key 5, an integrator 6 and a comparator circuit 7. key 5
and an integrator 6 are connected in series to the coil 4. The comparator circuit 7 is suitable for selecting the instantaneous time when the signal from the coil 4 passes through the zero level and has an input connected to the coil 4 . The output of the comparison circuit 7 is electrically connected to the control electrode of the key 5. The measurement circuit can be connected to any suitable recording device connected to the output of the integrator.

The device operates as follows. The magnetizing pulse generator 1 generates pulses that are applied to the magnetizing coil 2, which in response to the pulses form a residual induction spot on the sample (FIG. 1a). It is self-evident that such spots can be formed either regularly or occasionally with a predetermined period.

The measuring coil is actuated in such a way that when the sample 3 passes through the measuring coil 4, the residual induction spot generates a signal ε(t). At the moment T ₁ the part magnetized to saturation in a certain direction passes through the measuring coil 4 and the comparator circuit 7 is actuated to open the key 5. The integrator 6 starts integrating the signal applied from the measuring coil 4. moment
At T ₂ the comparator circuit 7 again operates to close the key 5. As a result, the output voltage of the integrator 6 may be proportional to the integral value of the signal from the measuring coil 4 within the time interval (T ₁ , T ₂ ). This voltage is recorded and then indexed by any suitable device (not shown), after which the integrator is cleared and the measuring circuit is ready to begin processing the next pulse. A time chart of the voltage at the output of the integrator 6 is illustrated in FIG. The magnitude of the signal thus recorded is used to determine the mechanical properties of the sample.

The reproducibility of test results in situations where large atmospheric temperature differences and where the device is subjected to high noise is preferably ensured by using the proposed device in the variant disclosed below.

Referring to FIG. 5, apart from the device shown in FIG. It is connected to the. The output of the integrator 6 is connected through another comparator circuit 9 to the other input of the control unit 8;
The other comparator circuit 9 is adapted to select the instantaneous time at which the output signal of the comparator circuit 6 is zero. The other output of the control unit 8 is connected to the integrator through a controlled current generator 10, and the output of the control unit can be connected to any suitable device for recording during a time interval, during which the control The controlled current generator 10 is energized by the control unit 8.

T ₁ and T ₂ are the instantaneous times (FIG. 3) at which the residual induction spot region in the test material, maximally magnetized in opposite directions, passes through the measuring coil 4.

The device of the above variant operates as follows. The moving test material is magnetized by the coil 2. The shape of the residual induction spot is illustrated in FIG. 1a. When the non-magnetized portion of the test material 3 passes through the measuring coil 4, the output signal of the coil is zero. Key 5 is closed. Controlled current generator 10 is turned off. The output signal of integrator 6 is zero. The residual induction spot when passing through the measurement coil 4 generates the above-mentioned induced electromotive force in the coil (third
figure). Comparator circuit 7 (FIG. 5) is activated at instant _T1 . The control unit 8 opens the key 5 and the signal from the measuring coil 4 is applied to the integrator 6.
The output voltage of the integrator increases in proportion to ∫ ^t _T1 ε(t)dt. As a result, the comparator circuit 9 operates above a threshold which determines the noise immunity of the device.
At the moment T ₂ (FIG. 3), the comparator circuit 7 is activated again in response to the control unit 8 closing the key 5 and turning off the controlled current generator 10, which causes the capacitor of the integrator 6 to switch off. (not shown) is discharged by the current of the controlled current generator 10. When the output voltage of integrator 6 is zero,
The comparator 9 operates and the control unit 8 switches on the controlled current generator 10. The device is now ready for the next pulse process.

The mechanical properties of the test material are determined in this case by the operating time of the controlled current generator 10. This time can be converted to a digital signal and applied to an indicator. If the controlled current generator 10 is a controlled direct current generator, its operating time is equal to the output voltage of the integrator 6 at the instantaneous time T ₂ (FIG. 6), i.e. ∫ ^T2 _T1 ε(t)dt. (a time chart of the output voltage of the integrator 6 is illustrated in FIG. 6). As is clear from the above description, this integral value does not depend not only on the velocity of the test material, but also on the displacement of the test material over the entire area of the measuring coil 4, but is determined only by the parameters of the residual induction spot. be done.

The method and apparatus described above reduce errors occurring in the readout of data representing the dimensions of residual induction spots and caused by axial displacements of the test material and the nonlinear dependence of the transducer signal on these displacements. enable.

Furthermore, the proposed method and apparatus eliminates dependence of the signal for reading the velocity of the test material and errors associated with twisting.

Industrial applicability The measurement accuracy obtained by using the method and device proposed by the invention makes it possible, for example, to test rolled products of arbitrary cross-section, since the test material This is because it does not require a symmetrical cross section. Therefore, the present invention can be suitably used for testing the mechanical properties of rolled steel products and pipes during their manufacturing process.