JPS6352345B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for simultaneously and continuously measuring magnetic properties of steel materials, specifically coercive force, residual magnetization, saturation magnetization, magnetic permeability, hysteresis loss, etc., without contact. be.

It is known that there is an extremely strong correlation between the magnetic properties and mechanical properties of steel materials, and this correlation can be used to perform non-destructive measurements of hardness, quench depth, strength, grain size, etc. It is being done. Furthermore, for magnetic materials such as silicon steel sheets used as transformer cores, hysteresis loss is the most important quality factor, and therefore strict measurement and quality control are performed.

However, in the laboratory, measurement of such magnetic property values requires processing the material to be measured into a solenoid shape, winding a magnetizing coil and a detection coil, and using a conventional magnetic property measuring device. It is done by doing. Although this method is the most accurate measurement method, it
It requires complicated procedures such as processing and coil winding. Another slightly more on-site method is the Epstein test, which is performed by stacking strip-shaped samples to form a rectangular magnetic path, but this is also an off-line test that requires sample collection.

On the other hand, methods that can be used online include a method that saturates a moving steel plate with an electromagnet and then detects the residual magnetization of the steel material downstream, and a method that detects the residual magnetization of the steel material downstream, and a method that generates a magnetic field due to eddy currents generated when a high-frequency magnetic field is applied to the steel plate. There are examples of continuous hardness meters that detect eddy currents and utilize the relationship between eddy current and initial magnetic permeability, and the correlation between initial magnetic permeability and hardness. Not too much. In addition, a method of transmitting a magnetic force through a steel strip and measuring the hardness of a steel plate from the amount of transmitted magnetism is known from Japanese Patent Publication No. 50-21869, and Japanese Patent Application Laid-Open No. 56-82443 describes a method of measuring the hardness of a steel plate by a similar method. An apparatus for measuring the amount of transformation is shown. However, in all of these methods, a constant DC magnetic field is applied to the steel material to be measured, the amount of permeation magnetism is measured, and the amount of permeation is directly correlated with the hardness or the amount of transformation. only one of the magnetic properties is required.

The present invention has been made in view of these circumstances, and aims to provide a method for simultaneously measuring various magnetic property values of steel materials in a non-contact, online manner. That is, in the present invention, an electromagnet excited by an AC excitation source is provided on one side of the steel material to be measured, and a magnetic detector for detecting the transmitted magnetic flux passing through the steel material to be measured is provided on the other side. The purpose is to determine the characteristics of changes in the amount of transmitted magnetic flux with respect to changes in the excitation current of the electromagnet, and to measure various magnetic characteristic values of the steel material to be measured as described above from this characteristic curve. The details of the present invention will be explained below with reference to the drawings. Figure 1 shows the magnetization curve of steel. As is well known, Hc is called the coercive force, Im is the saturation magnetization, and Ir is the remanent magnetization. ) is the initial magnetization curve, 0 of that curve
The slope of the rise from the initial permeability μ ₀ and the curve (2
→3→4→5→2) is the hysteresis loss
Called Wl.

FIG. 2 is a layout diagram of an apparatus for carrying out the present invention, in which 1 is a steel material to be measured, such as a cold-rolled steel plate, 2 is the magnetic core of an excitation electromagnet provided on the surface side of the steel material 1 to be measured, and 3 is a An excitation coil 4 wound around the magnetic core 2 is a power source for supplying an excitation current to the excitation coil, and has a voltage output E ₁ proportional to the magnitude of the current. 5 is a magnetic flux generated from the magnetic core 2, which is composed of a magnetic flux 5 ₁ passing through the steel material 1 to be measured and a magnetic flux 5 ₂ penetrating through the material 1 to be measured and transmitted to the back side.
Reference numeral 6 denotes a magnetic detector that detects the transmitted magnetic flux 5 ₂ , and 7 receives the current proportional output E ₁ of the excitation power source 4 and the output E ₂ of the magnetic detector 6, and determines the steel material 1 to be measured from a characteristic curve representing the relationship between both outputs. This is a device that calculates the magnetic properties of. Note that L is the distance between the tip of the magnetic core 2 and the magnetic detector, _l1 is the distance between the tip of the magnetic core and the surface of the steel material to be measured 1, and _l2 is the distance between the back surface of the steel material to be measured and the magnetic detector 6. , and t represents the plate thickness of the steel material to be measured.

Figure 3 is an example of a characteristic curve between the excitation current proportional output E ₁ measured by the apparatus shown in Figure 2 and the output E ₂ of the magnetic detector. It is obtained by changing from 0 in the positive direction, from a certain value in the negative direction, and from a certain negative value in the positive direction, and the change in the curve at that time is in the direction of the arrow in the figure 0' → 1' → The order is 2′→3′→4′→5′→2′.
In Fig. 2, the transmitted magnetic flux 5 ₂ decreases as the magnetic flux 5 ₁ passing through the steel material 1 to be measured increases, and conversely, the magnetic flux 5 ₁
If the value decreases, the transmitted magnetic flux 5 ₂ increases. Since the magnetic flux 5 ₁ in the steel to be measured is proportional to the magnetic susceptibility of the steel to be measured, the curve (E ₁ -E ₂ ) in Fig. 3 is the magnetization characteristic of the steel to be measured (I-H curve in Fig. 1). , depends on the dimensions of the steel material to be measured (plate thickness, plate width, length), the distances l ₁ and l ₂ and the magnetization characteristics of the magnetic core 2. Here, under the condition that the plate width and length of the steel material 1 to be measured are sufficiently larger than the size of the magnetic core 2, the influence of the plate width and length can be ignored. A magnetic material with high magnetic susceptibility and low hysteresis, such as permalloy or silicon steel plate, is used as the magnetic core 2, so that magnetic saturation does not occur in the magnetic core 2 even under excitation conditions where the magnetization characteristics of the steel material 1 to be measured are saturated. If the cross-sectional dimension of the magnetic core 2 is made large,
The magnetization characteristics of the magnetic core 2 are approximately linear with respect to the excitation current, and the influence of the magnetization characteristics of the magnetic core 2 can be removed. As a result, the characteristic curve (E ₁ − _{E 2} ) of the excitation current proportional output E ₁ and the output E ₂ of the magnetic detector is expressed by the following functional form, (E ₁ − E ₂ )=f[l ₁ , l ₂ , t(I-H)] (1) If we solve equation (1) analytically, we get from the curve (E ₁ −E ₂ ),
The magnetization curve (I-H) of the steel material to be measured is determined, and arbitrary magnetic property values can be measured. However, as is well known, magnetic circuits are nonlinear and individual variables are interrelated, so it is difficult to solve equation (1) analytically. Therefore, for each magnetic property value such as coercive force Hc and residual magnetization Ir, points corresponding to the magnetization curve in Figure 1 are found on the curve in Figure 3, and the relationship between the two is determined by the plate thickness t and measurement distances l ₁ , l ₂ It is more practical to perform the correction.

Next, specific means thereof will be explained for each magnetic characteristic value with reference to FIG. Figure 4 shows curve A, which is an enlarged hysteresis part of the curve in Figure 3, and the exciting current proportional output E ₁ when the steel material 1 to be measured in Figure 2 is removed under the same measurement conditions as curve A. and the characteristic curve B of the magnetic detector output E ₂ are shown superimposed on each other.

First, it will be shown that the holding force Hc is determined from the excitation current proportional output E _1c at the intersection C of curves A and B in FIG. This is because the definition of coercive force is the magnitude Hc of the magnetic field when the magnetization I of the steel material becomes 0 on the magnetization curve in Figure 1, and the fact that the magnetization of the steel material itself is 0 is the same as the absence of steel material. Therefore, from the excitation current proportional output E _1c , which is the intersection of curves A and B when the steel material is removed, in other words, the output E ₁ is an output proportional to the excitation current of the electromagnet, so the distance l ₁ is constant. If there is, it is proportional to the magnitude of the magnetic field applied to the steel material 1 to be measured, and if l ₁ changes, the coercive force Hc can be determined from E _1c by correcting it. In addition, the coercive force Hc changes even if the thickness of the steel material to be measured changes.
It does not depend on the plate thickness as long as a magnetic field sufficient for saturation is applied.

Next, the saturation magnetization Im is determined from the difference ΔE ₂ m between the magnetic detector output E ₂ at point m of curve A in FIG. 4 and curve B. Here, m is the point where the slopes of curves A and B become equal. In other words, when the magnetization of the steel material to be measured is saturated, its permeability dI/dH is approximately equal to the magnetic susceptibility of air, and when a magnetic field greater than the magnetic saturation is applied to the steel material to be measured, it is the same as there being no steel material to be measured. , and the slopes of curve A and curve B are equal. The difference in the output of the magnetic detector ΔE _2n is proportional to the magnetic flux 5 ₁ passing through the steel material to be measured, so if the plate thickness is constant, the output difference ΔE _2n is proportional to the saturation magnetization I _{n of} the steel material to be measured. . In the general case where the plate thickness changes, it is necessary to correct the plate thickness, but the plate thickness correction curve is stored in the arithmetic unit 7 shown in Fig. 2, and it is corrected using the signal from a separately provided plate thickness meter. Is possible. Further, the distance l ₁ may be corrected in the same manner as in the case of measuring the holding force Hc.

Furthermore, the residual magnetization Ir has an excitation current of 0, that is, E ₁ =
It can be found from the magnetic detector output E _2r at 0. In other words,
The magnitude of the magnetic flux measured by the magnetic detector 3 when the magnetic field applied to the steel material 1 to be measured is 0 is caused by the residual magnetization I _r of the steel material 1 to be measured. Further, the hysteresis loss W _l is determined from the area enclosed by the curve A in FIG. 4, and the initial magnetic permeability μ ₀ is determined from the slope of the rise of the curve A. Correction of plate thickness and distance is based on the holding force mentioned above.
This can be done in the same manner as in the case of Hc and saturation magnetization Im.

FIG. 6 is a device layout diagram showing another embodiment of the present invention as set forth in claim 2, with symbols 1 to 7 in the figure.
represents the same part as in FIG. A magnetic detector 8 is placed opposite the magnetic detector 6 across the steel material 1 to be measured, and detects the magnetic flux passing through the front side of the steel material 1 among the magnetic flux generated by the electromagnet.
Instead of the excitation current proportional output E ₁ in FIG. 2, the characteristic curve between the output E ₁ ' of the magnetic detector 8 and the output E ₂ of the magnetic detector 6 is also the same as the curve in FIG.
The magnetic properties of the steel material 1 to be measured can be measured by the same means as described above. By the way, when the present invention is applied online, the excitation frequency can be increased in proportion to the traveling speed of the steel material to be measured. At high frequencies, eddy currents occur in the magnetic core 2 and the steel material 1 to be measured, which creates a phase difference between the exciting current and the magnetic flux produced by the _{electromagnet} . Correction is required because the shape of the curve changes, but the method shown in Fig. 6 has the advantage that the above correction is not necessary because the magnetic flux produced by the electromagnet is directly measured by the magnetic detector 8. .

As explained in detail above, according to the present invention, various magnetic property values can be measured simultaneously without contact, and by utilizing the correlation between these magnetic property values and mechanical properties, it is possible to measure, for example, the hardness of a cold-rolled steel sheet. It also has great effects, such as making it possible to continuously manage the hysteresis loss of electrical steel sheets online. The shape of the magnetic core is not limited to a horseshoe shape as shown in FIG. 2, but a rod shape as shown in FIG. 7 may be used to detect the transmitted magnetic flux 5 ₂ in the direction perpendicular to the plate surface of the material to be measured.

Next, an example will be shown in which the magnetic properties of a steel plate according to the present invention were measured. In the arrangement shown in Fig. 2, the steel material to be measured 1
is a cold-rolled steel plate with a thickness of 0.2 to 1.6 mm, and the magnetic core 2 and magnetic detector 6 were arranged so that l ₁ and l ₂ were each 20 mm apart from the threading level of the cold-rolled steel plate. The material of the magnetic core 2 is a laminated silicon steel plate, the cross-sectional area is 40 x 40 mm, and the length of ^{the two} magnetic paths is 240 mm. Magnetic detector 3 has a diameter of 1.2
mm coated copper wire, the number of turns was 250, the maximum excitation current was ±10A, the frequency was 100Hz, and a Hall element was used as the magnetic detector. Arithmetic device 7
A microcomputer is used for this, and the straight line corresponding to Fig. 4B, which was measured without a cold-rolled steel sheet, is stored in the device 7 in advance.
Excitation current e.g. proportional output E ₁ and magnetic detector output
Obtain the curve corresponding to Fig. 4 A from E ₂ , for example,
The coercive force Hc was measured from the excitation current proportional output _E1c when the curves B intersect.

Figure 5 shows an example of the measurement results, where the vertical axis is the excitation current proportional output E _1c obtained by the method of the present invention, and the horizontal axis is the result obtained by processing a cold-rolled steel plate into a solenoid shape and measuring it using a conventional method for measuring magnetic properties. A very good correspondence was obtained in terms of values.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the magnetization curve of steel material, Fig. 2 is an explanatory diagram showing an example of a device implementing the present invention, and Fig. 3 is an excitation current proportional output E measured by the device shown in Fig. 2. ₁ and the output E ₂ of the magnetic detector, FIG. 4 is an enlarged view of the hysteresis part of FIG. 3, FIG. 5 is a graph showing an example of measurement results according to the present invention, and FIGS. FIG. 7 is an explanatory diagram showing an example of a device different from that shown in FIG. 2. 1: Steel material to be measured, 2: Magnetic core of excitation electromagnet,
3: Excitation coil, 4: Excitation power supply, 5, 5 ₁ , 5 ₂ :
Magnetic flux, 6: Magnetic detector, 7: Arithmetic device, 8: Magnetic detector.

Claims (1)

[Scope of Claims] 1. An electromagnet excited by an AC excitation source is provided on one side of the steel material 1 to be measured, and a magnetic detector 6 that detects the transmitted magnetic flux 5 ₂ that has penetrated the steel material 1 to be measured is provided on the other side. is provided, and when the excitation current of the electromagnet is changed, a characteristic curve of the change in the voltage output E ₁ proportional to the magnitude of the excitation current of the electromagnet and the voltage output E ₂ of the magnetic detector is determined, and this characteristic curve is and the voltage output E ₁ which is proportional to the magnitude of the excitation current of the electromagnet when there is no steel material to be measured, which has been separately determined in advance.
1. A method for measuring magnetic properties of a steel material, characterized in that the magnetic properties of the steel material to be measured are measured by comparing the characteristic curve with respect to changes in the voltage output _E2 of the magnetic detector. 2 An electromagnet excited by an AC excitation source and a magnetic detector 8 that detects the magnetic flux passing through the front side of the steel material to be measured, which is generated by the electromagnet, are placed on one side with the steel material 1 to be measured sandwiched therebetween. In addition to providing
A magnetic detector 6 is provided on the other side to detect the transmitted magnetic flux 5 ₂ that penetrates the steel material to be measured, and the voltage output of the magnetic detector 8 when the excitation current of the electromagnet 2 is changed is
A characteristic curve of changes in E ₁ ′ and the voltage output E ₂ of the magnetic detector 6 is determined, and this characteristic curve and the voltage output E ₁ of the magnetic detector 8 in the absence of the previously determined steel material to be measured are calculated. ' and the voltage output of the detector 6
1. A method for measuring magnetic properties of steel, characterized in that the magnetic properties of the steel to be measured are measured by comparing the characteristic curve of change in _E2 .