JPS59188508A - On-line detector for amount of transformation and flatness of steel material - Google Patents

Abstract

PURPOSE:To detect the amount of transformation and flatness of a steel material by arranging an exciting coil on one side of the steel material to be measured and plural detection coils at different positions, and processing detection signals from the detection coils. CONSTITUTION:When the steel material is in gamma single phase, pieces 141 and 142 of magnetic flux interlinking with the detection coils 151 and 152 through the exciting coil 13 excited by an AC exciting device 12 are generated with intensities corresponding to distances l1 and l2 from the exciting coil 13 and voltages proportional to them are induced. When alpha-phase precipitation by transition from gamma to alpha occurs to the steel material, the steel material 1 varies in magnetic field intensity and the pieces 141 and 142 of magnetic flux vary in initial intensity, and the variations are detected as variations in induced voltages across the detection coils 151 and 152. Further, when lift-off (flatness) variation is caused, the induced voltages across the detection coils 151 and 152 vary. Detection signals 161 and 162 are transmitted to an arithmetic device 17 and processed to calculate the amount of tranformation and flatness in the steel material 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for online detection of the amount of transformation and/or flatness of W4 material.

There are various methods of strengthening steel, such as work hardening, precipitation hardening, solid solution strengthening, grain refinement strengthening, and transformation structure strengthening. With this method, even higher strength can be achieved in the hot rolled state! !
As a means of manufacturing II materials, the use of transformation@weave strengthening technology through controlled cooling after hot rolling is becoming more active than ever.

By the way, when using transformation structure strengthening technology, it goes without saying that accurate knowledge about the transformation behavior of steel is required.

The transformation behavior of steel is generally known to have been investigated experimentally, but the results obtained when manufacturing with actual equipment are often significantly different from the results obtained in the laboratory. Although the actual situation is not fully understood, one of the reasons why the transformation behavior in the actual machine differs from the laboratory results is that the transformation behavior changes in a complicated manner due to the history of thermal strain in the previous or upstream process. It is said that this is because it depends on what you do. Therefore, for example, (a) in order to improve the homogeneity of the material in the longitudinal and width directions, which are major factors that affect the quality of hot-rolled steel products, we are trying to reduce local changes in transformation behavior based on differences in rolling temperature history. As a means of understanding, or also,
(b) As a means of grasping the ratio of the γ phase and α phase at the time of applying reduction in order to manufacture steel materials with high strength and toughness, such as steel plates for high-strength Kalline pipes, it is also possible to , (Hano) We investigated the transformation behavior of yuzu as a means of understanding the ratio of γ phase to α phase at the start of quenching in the production technology of mixed-structure steel to produce thin steel sheets with high strength and excellent workability. If accurate online information on steel can be detected, it will be possible to expect great benefits in the field of manufacturing various steel materials using hot rolling lines and heat treatment lines.

Conventionally, the following methods have been proposed as five methods for online detection of the transformation behavior of steel materials. Part 1
The first method is, for example, as disclosed in Japanese Patent Publication No. 56-24017, in which the temperature rise due to latent heat during phase transformation is detected by a thermometer installed in the production line, and the transformation behavior is attempted to be ascertained. However, this method has the drawbacks that the information obtained is very general, the response is slow, and because a thermometer is used as a sensor, no light is emitted during measurements during water cooling, for example.

Also, y, I Kaisho 49-114518, 51-136
442 and ζh Japanese Patent Publication No. 3-25309, methods have been proposed in which X-rays are directed onto the surface of a steel material and the amount of transformation is measured from the diffraction intensity 3-. However, since this method irradiates intense X-rays, it is necessary to take safety measures against X-ray damage, and therefore the detection device itself becomes a large tree, increasing installation costs and limiting the number of installations. Otherwise, maintenance problems may occur, and in addition, the information obtained may be approximately 50% below the epidermis of the material to be measured.
It is a surface layer within μm, and has the disadvantage that it is difficult to provide macroscopic information.

In contrast, by utilizing the fact that the γ phase → α phase transformation of steel is accompanied by the physical phenomenon of changing from paramagnetism (γ phase) to ferromagnetism (α phase), we can detect the transformation using a magnetic detector. There are methods for detecting behavior, such as Japanese Patent Laid-Open No. 50-104754 or Japanese Patent Laid-Open No. 56-82443. These methods have the problem that the measurable temperature range is limited to the temperature range below the Curie point of the steel being measured.
The Curie point of most commercial steels is as high as approximately 756°C or higher, whereas the transformation range of steel during the cooling process shifts to the lower temperature side in a non-equilibrium manner, so the 4 major transformation points are below the Curie point. The above-mentioned problem does not pose a practical problem except for some steels, since the process proceeds in the temperature range of
And compared to Haku's method which does not use magnetic means mentioned above,
It has the advantage of being simple and responsive, and can be measured even during water cooling, so it can be said to be a practical and effective method.

However, although they have the general advantages as mentioned above, the previously proposed JP-A-50-104754 and JP-A-56-
The magnetic detection device disclosed in No. 82448 has unresolved problems as described below, and it is difficult to say that the magnetic detection device is still suitable for practical use.

First, we will discuss Japanese Patent Application Laid-open No. 104754. The proposal relates to a hot rolling method using a magnetic detection device, and is not a proposal regarding the magnetic detection device itself, and the details regarding the function and structure of the detection device used for implementation are unclear. According to the proposal in Mei II, an excited pickup coil is placed close to the steel to be measured, and the impedance change of the pickup coil itself that occurs as the steel to be measured changes from γ phase to α phase. This method qualitatively detects the presence or absence of metamorphosis. However, in order to apply it to the above-mentioned steel manufacturing field, it is necessary for the magnetic detection device to have a function that can quantitatively detect the progress of transformation. It must be said that a detection device whose function is only to qualitatively detect the presence or absence of a substance has little value in application.

Next, JP-A-56-82443 will be described.

FIG. 1 is a block diagram showing the configuration of the magnetic detection device in the proposal. In this magnetic detection device, an excitation coil 3 wound around a magnetic pole 2 constituted by a U-shaped iron core and a magnetic flux detector 6 are arranged at a constant interval of degrees Celsius, sandwiching a steel material 1 as a material to be measured. Among the magnetic flux 5 generated by exciting the excitation coil 3 by the excitation device 4, the strength of the magnetic flux 5o that penetrates the steel material 1, leaks, and reaches the magnetic flux detector 6 is detected. The amount of transformation is detected because the strength of the magnetic flux 5o changes in accordance with the amount of transformation in 1. In the figure, 7 is a thermometer, 8 is a calculation device,
9 is a condition signal such as material, plate thickness, etc. Although this method has the ability to quantitatively measure the amount of transformation in principle compared to the method of JP-A-50-104754, it has the following problems when applied to an actual production line. There are drawbacks.

That is, in the case of the above configuration, the strength of the magnetic flux 5o (vA flux density) is approximately inversely proportional to the distance between the magnetic pole 2 and the magnetic flux detector 6, so in order to detect the amount of transformation with sufficient accuracy, the distance between this ℃ must be kept at least about 150 mm or less, but when applied to an actual production line, the steel material 1 must be kept in such a narrow gap without coming into contact with the magnetic flux detector 6.
It must be said that it is extremely difficult to move the The reason for this is that the shape of hot-rolled steel sheets produced by hot strip mills and plate mills, for example, is warped or wavy and is not necessarily flat, especially at the tip of the rolled steel material. This is because this tendency is strong near the rear end, and it is difficult to avoid contact with the steel material during transportation. To avoid such accidents, for example, steel + lr
Although it is possible to temporarily widen the above-mentioned gap when passing the tip and rear ends of For example, the value of installing a detection device is halved.Furthermore, the proposed magnetic detection device reduces the gap occupied by the magnetic circuit through which the magnetic flux 5 passes, due to the difference in the plate thickness t of the steel material 1, which is the material to be measured. changes, so the detection output needs to be corrected depending on the plate thickness t, and the measurement accuracy depends on the actual plate thickness t. The plate thickness t of 1 is, for example, 1.
2-30mm, plate mill 5.0-300an
These corrections are complicated, and it is difficult to optimize the detection accuracy according to the actual plate thickness t from the viewpoint of the transportability of the steel material 1 described above.

As mentioned above, it must be said that the magnetic detection device proposed in Japanese Patent Application Laid-Open No. 56-82443 has many problems when applied to an actual manufacturing line.

The present invention was developed to solve the problems of the prior art as described above. Furthermore, it is an object of the present invention to provide a multifunctional magnetic detection device that can accurately detect the flatness of steel materials from time to time.

The present invention is an on-line detection device for the amount of transformation and flatness of the coil (2), which is arranged on either side of the steel material to be measured, and generates an alternating magnetic flux by alternating current excitation (n coil). , arranged on the same side as the excitation coil and at different distances from the excitation coil so that they are mutually induced by the excitation coil. We have achieved the above objective by confirming the amount of transformation and flatness of mU from the difference in the detection signal caused by the difference in Toman, and the calculation to obtain only one of them. be.

The present invention will be explained in detail below based on the illustrated example of an actual egg.

FIG. 2 shows a first embodiment of pulverization i+j]. In the figure, 1
12 is a steel material to be measured, 12 is an AC excitation device, 13 is an excitation coil, and 15+ and 152 are detection coils provided at different distances from the excitation coil 13, such as A+ and β2. 141 is a magnetic flux generated by the excitation coil 13 and interlinks with the detection coil 151 through the steel material 1; similarly, 142 is a magnetic flux that interlinks with the detection coil 152.

Now, since the steel material 1 is in a paramagnetic state when it has not started transformation, that is, when it is in the γ single phase, the detection coils 151 and 152
The magnetic fluxes 14+ and 142 interlinked with each other have a constant strength corresponding to the distances J11 and J12 from the excitation coil 13, and are in a state (hereinafter referred to as initial state) in which induced voltages proportional to these are generated.

When the γ → α transformation occurs in the steel material 1 and a ferromagnetic α phase is precipitated, the α phase is magnetized, causing a fluctuation in the magnetic field strength of the steel material 1.
Since the strength of magnetic flux 141 and 142 deviates from the initial state,
It is detected as a change in the induced voltage of the detection coils 15+ and 152, respectively. Also, when the distance L between the W4 material 1 and the excitation coil 13 (hereinafter referred to as lift-off. Lift-off measurement is synonymous with flatness measurement) changes, the induced voltages of the detection coils 151 and 152 change, respectively. do. Detection signal 16+ in such detection coil 151.152
. Calculate separately.

Next, detection signals 161.16 of detection coils 151 and 152
A method for determining the amount of transformation in the steel material 1 and the lift-off L from the magnitude of 2 will be described.

FIG. 3 shows a distance p1 between the excitation coil 13 and the detection coil 151 in a detection device basically having the configuration shown in FIG.
is 5Qn+m, and the distance to the detection coil 152 is 12
is 100 mm, and shows the relationship between the detection signals (the amount of change in induced voltage from the initial state) of the detection coils 151 and 152 when the lift-off L of the γ→α transformation device of the steel material 1 changes. In Fig. 3, each broken line indicates the case where the amount of transformation is constant and only the lift-off L changes, and -
11- Each solid line shows the relationship when the lift-off L is constant and only the amount of transformation changes. As is clear from FIG. 3, the detection signal 161. between the detection coils 151 and 152.
The relationship between the magnitudes of 162 and 162 becomes a curved relationship, for example, 0→a-+b→0→d→e-+f when the lift-off L changes, but when the amount of transformation changes, for example, O
The relationship is almost linear as →j-+i-+11→0→f. That is, it can be seen that the vector quantities determined by the detection signals 161 and 162 of the two detection coils 151 and 152 have a unique relationship with the transformation quantity and the lift-off L, respectively. Therefore, the relationship shown in FIG. 3 is precisely determined in advance and stored in the arithmetic unit 17 in FIG.
+, 162 are compared with this and calculated, the amount of transformation and lift-off L can be determined at the same time.

In addition, although the above description is based on the case where two detection coils are used, it goes without saying that the same applies even when the number of detection coils is larger than this. Of course, it is possible to perform more precise measurements by measuring originally.

Furthermore, as is clear from the above explanation, the present invention is configured such that information on "transformation amount only", "transformation amount and flatness", and [flatness only J] can be selectively determined as necessary. but,"
When focusing on obtaining information on "flatness only", the material to be measured is not limited to "WA material" as long as it has some effect on the mutual induction between the excitation coil and the detection coil. Therefore, when only flatness information is required, the term "steel material", including in the claims, refers to RM material and other materials that affect the mutual induction effect between the excitation coil and the detection coil. "Plate-shaped material inside"
shall be read as It goes without saying that if only one of the pieces of information is required, it is sufficient to output only that one piece of information.

Next, preferred embodiments at the stage of concretely implementing the present invention will be described.

First, the arrangement of the detection coil and excitation coil will be explained. FIG. 4 shows a second embodiment of the present invention, which has the same basic configuration as the first embodiment shown in FIG. It is something that FIG. 5 shows the detection accuracy of lift-off L when the distance λ2 between the excitation coil 13 and the detection coil 152 is variously changed in the detection device shown in FIG. It can be seen that the detection accuracy of lift-off L tends to deteriorate both when it is less than 20+ nm and when it exceeds 200 mm, and there is an optimum range for ρ2 in order to obtain good detection accuracy. Note that the above tendency also applies to the detection accuracy of the amount of metamorphosis. The reason for this is understood to be as follows. That is, when β2 exceeds 200 mm, the detection signal 162 of the detection coil 152 in FIG. 4 becomes extremely small, so it is not easily affected by noise etc.
The ratio deteriorates. - If β2 is less than 20 mm, the difference between the amount of transformation in the detection coils 151 and 152 in FIG. This makes it difficult to do so, and the detection accuracy deteriorates. According to the present invention, based on the above findings, it is found that it is desirable to arrange the detection coils within a radius of 200 mm from the center of the excitation coil, and to maintain a distance of 20IIl1 or more between the detection coils.

Next, we will discuss the effects of the core. One of the drawbacks of a magnetic detection device is that it has a general characteristic that the magnitude of a detection signal decreases inversely as lift-off increases, so that the range of lift-off that can be detected is limited. Needless to say, each actual f! When applied to an li manufacturing line, it is desirable that the range is as large as possible not only from the viewpoint of detection accuracy but also from the viewpoints of heat resistance of the detection device, transportability of the material to be measured, shape, etc., and the present invention addresses this point. As a result of repeated research, it has been found that the magnitude of the detection signal at the same lift-off can be significantly increased by providing independent dedicated cores for the excitation coil and detection coil as necessary.

15- Figures 6 to 8 show third to fifth embodiments of the present invention in which each coil is provided with a core, and Figure 6 shows the excitation coil 1.
Similarly, FIG. 7 shows a case where rod-shaped cores 1901191 and 192 are provided in the excitation coil 13 and the detection coils 151 and 152, respectively.

Further, FIG. 8 shows a configuration in which the excitation coil 13, the detection coil 151, and the detection coil 152 are connected by an E-shaped core 193. FIG. 9 shows that the γ→α transformation rate of steel material 1 is 100% and the lift-off L is measured using the detection device of the second embodiment shown in FIG.
2 under the same conditions with reference to the magnitude of the detection signal 162 in the detection coil 152 when the diameter is 100 mm,
8 shows a relative comparison of the magnitudes of the detection signals 162 detected by each of the detection devices shown in FIGS. 6 to 8. Note that the results shown in FIG. 9 are all the same under conditions other than those related to the core.

According to FIG. 9, the rod-shaped core 1 is attached to the excitation coil 13 in FIG.
9o (third embodiment) and when rod-shaped cores 19o, 19+, and 192 are provided for the excitation coil 13 and detection coils 151, 16-152 in FIG. 7, respectively (fourth embodiment). It is clear that the magnitude of the detection signal 162 tends to increase compared to the case where no core is provided (second embodiment) as shown in FIG. 4, and by providing the rod-shaped cores 19o to 192, It can be seen that the detection accuracy can be improved. In the case of the fifth embodiment provided with the E-shaped core (193) shown in FIG. 8, the magnitude of the detection signal 162 is larger than that of other embodiments of the present invention in the range where the lift-off L is 50 mm or less. , it has been confirmed that the magnitude of the detection signal 162 in the state where the lift-off L is 100 mm is rather small.As it is clear from FIG. Embodiment 5 is suitable for use in relatively small-scale lines where the steel material 1 to be measured has good flatness.

Next, desirable excitation conditions in the present invention will be described.

As is well known, it is now known that the depth of penetration of magnetic flux into a magnetic material largely depends on the frequency of the magnetic flux. That is, as the excitation frequency of the excitation coil of the detection device increases, the penetration depth into the material to be measured decreases. By the way, it is generally known that steel materials after hot rolling exhibit unique transformation behavior under the skin due to the influence of temperature distribution or rolling processing, etc., and in relation to the material quality of the final product, it is necessary to The detected information becomes less meaningful.

Therefore, when making measurements, it is desirable to optimize the excitation conditions of the detection device. According to the research conducted by the present inventors, the region in which the transformation properties of hot rolled steel exhibit peculiar behavior is approximately 200 μm below the surface skin.
In order to avoid these problems, it is desirable that the penetration depth of the bundle into the shin is 200 μm or more, and from the above point of view, it is desirable that the frequency of the excitation current of the detection device is lower than 10 KHz. On the other hand, as the frequency decreases, the penetration depth of the magnetic flux increases and the detected information on the amount of transformation becomes more macroscopic, but on the other hand, the response speed of the detection device deteriorates and the S of the detection signal... / N
This causes inconveniences such as a decrease in the ratio.

To avoid such problems, the excitation Tlk frequency should be set to 5H2.
It is desirable that it not be less than Note that the most preferable excitation frequency range is 30Hz to 1KH2.

As described above, the invention is to arrange at least two or more detection coils on the same side as the excitation [η coil and at different distances from the excitation coil, and to detect the measurement target 4 by the detection signal.
Since the transformation amount and flatness E lift-off J of the major steel (E) are determined at the same time, (B) mutual induction by HL gas is used for detection, which is accurate and responsive and can be performed online. As a quantitative detection means, one or more of each of the detection devices are used;
It is possible to put it into practical use even on a production line where the flatness of 7t is not very good; (c) Even though the magnetic field is measured by placing an interrogator on one side of the steel material, it is not affected by lift-off fluctuations. The amount of transformation of the steel material can be detected; the flatness of the steel material can be detected by using the online information related to the flatness of the steel material; It can be detected without being affected by the amount of transformation of the steel material; (b) It can be widely used in various environments such as high temperature environments and underwater; Online detection of the amount of transformation of steel materials during hot rolling and heat treatment processes is thermal theory, and online detection of flatness can also be performed. As long as it has some effect on the mutual induction between the excitation coil and the detection coil, it can be used for an extremely wide range of applications, such as being able to detect the flatness of the material to be measured online regardless of the presence or absence of transformation behavior. Is possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram partially including a sectional view showing a conventional example of a magnetic measurement type transformation amount detection device, and FIG. 2 is a block diagram corresponding to FIG. 1 showing a first embodiment of the present invention. 20- Fig. 3 is a diagram showing the correlation between the increase/decrease in lift-off and the amount of transformation and the detection signal in the detection coil for detailed explanation of the present invention; A block diagram corresponding to FIG. 2 showing the second embodiment, FIG. 5 is a diagram showing the relationship between the detection coil spacing and the constant error of the lift-off yaw 11 in the second embodiment, and FIGS. 6 to 8 are FIG. 9 is a block diagram corresponding to FIG. 2 showing the third to fifth embodiments of the present invention, and FIG. FIG. 6 is a diagram showing a comparative relationship with respect to the second example. 12... AC excitation Elj 'iA &, 13... Excitation coil, 141.142... Magnetic flux, 151.152... Detection coil, A1. ft2...Distance between the working coil and the detection coil, L...Distance between the steel material and the excitation coil y lift-off;
161.162...Detection signal, 17...Arithmetic device, 19o-192... Rod-shaped core, 193...E-shaped core. Agent Takaya Theory (1 idiot) 23- Figure 1 Figure 2 Figure 3 Figure 4 Figure 5? ; 0 50 100 150 200
Kabuto 4 times 1-cho δ = rT5BJa Azui Koi and Gekihide Koi
Shino distance method (mml Figure 6 Figure 7 Figure 8 Figure 9

Claims (1)

[Scope of Claims] <1) An excitation coil in which the steel material to be measured is placed on one side and can freely generate alternating magnetic flux by alternating current excitation; Two or more detection coils are arranged at different distances from each other and are mutually induced by the excitation coil, and the difference in detection signal caused by the difference in magnetic flux linkage in each detection coil determines the amount of transformation of the steel material. 1. An online detection device for the amount of transformation and flatness of a steel material, comprising: an arithmetic device that determines flatness or only one of them; (2) The above-mentioned two or more detection coils are arranged within a range of 200 mm from the excitation coil, and at a distance of 20 mm from each other.
An on-line detection device for the amount of transformation and flatness of a steel material according to claim 1, characterized in that the device is arranged as described above. (3) At least one of the excitation coil and the detection coil is provided with a dedicated core that does not span between the coils. Online detection device for the amount of transformation and flatness of W4 material. (4) The transformation of steel material according to any one of claims 1 to 3, wherein the excitation current flowing through the excitation coil has a frequency in the range of 5Hz to 10KH2. Online quantity and flatness detection device.