JP5079714B2 - Surface state measuring apparatus and surface state measuring method - Google Patents

Description

  The present invention relates to a surface state measuring apparatus and a surface state measuring method, and more particularly to a surface state measuring apparatus and a surface state measuring method for measuring a surface state of a measurement object in a non-contact manner using eddy current.

  In the steel industry, it is very important to maintain the quality by controlling the surface condition of the steel material to be manufactured. Moreover, it is very important not only at the time of manufacture but also to measure the surface state of a finished steel material when using the steel material. However, in reality, it is not easy to measure a steel material such as a steel material in a steelmaking process that is moving, at a high temperature, or in which cooling water is scattered.

  A continuous casting process is an example of a process in the steel industry in which it is very important to measure the surface state of a steel material. In this continuous casting process, it is a very important process to make a steel slab directly from molten steel (an example of steel material, also called slab). The molten steel is poured into a mold and the solidified side is drawn from the bottom of the mold. Thus, a slab is formed. At this time, if the outer solidified shell is thin, so-called “bulging deformation” occurs in which the slab between the rolls from which the slab is drawn is expanded due to the static pressure of the molten steel inside. In this case, measuring the presence or absence of bulging deformation, that is, the shape of the surface of the steel material (an example of the surface condition) is very important for maintaining manufacturing stability and maintaining product quality after subsequent processing steps. is important.

  Many measuring devices have been developed that measure the amount of deformation caused by such bulging deformation (hereinafter also referred to as “bulging amount”) as an example of the surface state of a steel material. Such measuring devices are roughly classified into, for example, a contact type, an indirect contact type, and a non-contact type.

  For example, as an example of a contact-type measuring device, there is a measuring device disclosed in Patent Document 1. The measuring apparatus of Patent Document 1 detects the position of a slab by pressing an annular contact having a rounded head at the tip against the slab with a cylinder and detecting the contact position. In addition, this measuring device has heat resistance and durability measures by ejecting cooling water from the tip. However, since it has a movable part and is in contact with the high temperature part, it is difficult to use it stably for a long time.

  Moreover, as an example of an indirect contact type measuring device, there are measuring devices disclosed in Patent Documents 2 and 3. The measuring apparatus of patent document 2 forms a water column with respect to steel materials, and measures a distance with an ultrasonic distance meter by using the water column as a sound wave transmission medium. However, in this measuring apparatus, the working environment is not stable, and it is difficult to form a stable water column in a high-temperature environment in which cooling water or the like to the steel material is scattered. Moreover, the measuring apparatus of patent document 3 measures the roll reaction force of the hot_water | molten_metal surface level inside a casting_mold | template and the representative roll for slab conveyance, and calculates | requires the bulging amount from the measurement result. However, with this measuring device, it is difficult to detect sudden bulging of a very small part. Therefore, even with these indirect contact-type measuring devices, it is difficult to accurately and stably measure the surface state of the steel material.

  As an example of a non-contact type measuring apparatus capable of relatively stable measurement, there is a measuring apparatus disclosed in Patent Document 4. The measuring apparatus of Patent Document 4 scans the eddy current rangefinder with respect to the steel surface, and obtains the bulging amount from the scan result. For example, in a secondary cooling zone in continuous casting, cooling water is sprayed and a high-temperature steel material is cooled. However, the measurement device of Patent Document 4 is capable of relatively stable measurement even under such adverse conditions. It is said.

JP 2006-130549 A JP-A-61-67550 JP-A-9-206906 JP-A-3-268850

  However, when the temperature of the slab changes significantly, for example, just below the mold, other surface conditions such as the permeability and conductivity of the slab also change greatly. For example, when the temperature is around the Curie point, the magnetic permeability of the steel material varies greatly and the electrical conductivity also varies greatly as the temperature varies. Therefore, under the condition that the other surface state of the steel material greatly changes in this way, the measuring device of Patent Document 4 is difficult to measure quickly, such as requiring calibration each time. In many cases, it is difficult to perform stable and accurate measurement.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to quickly and stably provide accuracy of one surface state of a steel material even under conditions where other surface states fluctuate. Measure well.

In order to solve the above problems, according to one aspect of the present invention, there is provided a surface state measuring device for measuring a surface state of a moving steel material,
Three probes including one excitation coil and one or two detection coils, which are arranged side by side on the same axis so that each coil end face is opposed to the steel material surface, and have the same coil characteristics and an air core, A probe set in which the three probes are arranged side by side so that the coil characteristics of the excitation coils are equal, the excitation coils are located on the same axis, and the distances from the steel surface are different;
An excitation unit that sequentially applies an AC voltage to each of the three excitation coils included in the probe set within one measurement time to excite the three excitation coils one by one;
A magnetic flux detection unit that detects a magnetic flux generated by the excitation coil excited by the excitation unit using a detection coil of the probe including the excitation coil and converts the magnetic flux into an electrical signal;
A surface state deriving unit for deriving a surface state of the steel material at a position facing the coil end surface within the one measurement time based on the electrical signal converted by the magnetic flux detection unit for each of the three exciting coils; ,
There is provided a surface state measuring apparatus characterized by comprising:

In addition, the excitation coil included in at least one of the probes is shared as the detection coil with the other probe adjacent to the probe,
The magnetic flux detection unit uses the excitation coil of the at least one probe as the detection coil of the other probe when the excitation coil of the other probe is excited by the excitation unit. You may detect the magnetic flux with respect to the exciting coil of a probe.

In addition, the probe set includes the three exciting coils arranged adjacent to each other on the same axis, and a position closer to the steel material surface than the three exciting coils, and a position farther from the steel material surface. 3 excitation coils and 2 detection coils arranged side by side on the same axis,
When the excitation coil of the other probe is excited by the excitation unit, the magnetic flux detection unit may include the other two excitation coils adjacent to the excitation coil or the other one excitation coil and Two electrical signals, which are detection results of the magnetic flux of the exciting coil, may be acquired from one of the detection coils and converted into an electrical signal of the difference between the two electrical signals.

The excitation unit applies the alternating current of at least two frequencies to the excitation coil within the one measurement time,
The magnetic flux detector detects the magnetic flux for each of the two frequencies and converts it into an electrical signal,
The surface state deriving unit may derive the surface state based on an electric signal for the frequency having the largest absolute value of the electric signal.

  Further, the surface state derived by the surface state deriving portion may be the shape, magnetic permeability, or conductivity of the steel material surface.

  Further, the surface state deriving unit may derive the surface state based on a relationship between the electrical signal measured in advance for each steel material and the surface state together with an electrical signal for each of the three excitation coils. .

Moreover, in order to solve the above problems, according to another aspect of the present invention, there is provided a surface state measuring method for measuring a surface state of a moving steel material,
Three probes including one excitation coil and one or two detection coils, which are arranged side by side on the same axis so that each coil end face is opposed to the steel material surface, and have the same coil characteristics and an air core, In the probe set in which the three probes are arranged side by side so that the coil characteristics of the excitation coils are equal, the excitation coils are located on the same axis, and the distances from the steel material surface are different, An excitation step of sequentially applying AC voltage within one measurement time to excite the three excitation coils included in the probe set one by one;
A magnetic flux detection step in which the magnetic flux detection unit detects the magnetic flux generated by the excitation coil excited in the excitation step by the detection coil of the probe including the excitation coil, and converts the magnetic flux into an electrical signal;
The surface state deriving unit derives the surface state of the steel material at a position facing the coil end surface within the one measurement time based on the electric signal converted in the magnetic flux detection step for each of the three excitation coils. A surface state deriving step to perform,
A method for measuring a surface condition is provided.

  As described above, according to the present invention, the excitation coils of the three probes in the probe set are sequentially excited within one measurement time to detect the respective magnetic fluxes, and based on the electrical signals representing the magnetic fluxes. One surface state of the steel material can be derived. Therefore, one surface state of a steel material can be measured quickly and stably with high accuracy even under conditions where other surface states vary.

It is explanatory drawing for demonstrating the outline | summary of the continuous casting which is an example of the application destination of the surface state measuring apparatus which concerns on each embodiment of this invention. It is explanatory drawing for demonstrating the outline | summary of the continuous casting which is an example of the application destination of the surface state measuring apparatus which concerns on each embodiment of this invention. It is explanatory drawing for demonstrating the relationship between the relationship of the magnetic field and bulging amount which the surface state measuring apparatus which concerns on each embodiment of this invention uses. It is explanatory drawing for demonstrating the relationship between the relationship of the magnetic field and bulging amount which the surface state measuring apparatus which concerns on each embodiment of this invention uses. It is explanatory drawing for demonstrating the structure etc. of the surface state measuring apparatus which concerns on 1st Embodiment of this invention. It is explanatory drawing for demonstrating the dead zone in the relationship between the relationship between the magnetic field which the surface state measuring apparatus which concerns on each embodiment of this invention uses, and the amount of bulging. It is explanatory drawing for demonstrating the 1st example of the probe set which the surface state measuring apparatus which concerns on 1st Embodiment of this invention has. It is explanatory drawing for demonstrating the 2nd example of the probe set which the surface state measuring apparatus which concerns on the same embodiment has. It is explanatory drawing for demonstrating the surface state derivation | leading-out process by the surface state measuring apparatus which concerns on the same embodiment. It is explanatory drawing for demonstrating the operation | movement in the surface state derivation | leading-out process by the surface state measuring apparatus based on the embodiment. It is explanatory drawing for demonstrating the operation | movement in the correlation derivation | leading-out process by the surface state measuring apparatus which concerns on the same embodiment. It is explanatory drawing explaining the example of the derivation | leading-out result of the correlation which the surface state measuring apparatus which concerns on the same embodiment uses.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  In addition, the surface state measuring apparatus which concerns on each embodiment of this invention demonstrated below WHEREIN: As the surface state (characteristic) of steel materials, either the shape of a steel material surface, magnetic permeability, or electrical conductivity is the same or similar structure. It is possible to measure. Therefore, for convenience of explanation, a case where “the shape of the steel material surface” is measured as an example of the surface state will be described as an example. In addition, as an example of the shape of the steel material surface, a case of measuring bulging in continuous casting under bad conditions will be described as an example so that the effect of this surface state measuring device becomes clearer. Note that the bulging is measured, for example, by measuring the distance to the steel surface from a fixed position and measuring the distance along the surface of the steel material (with respect to the moving steel material). As a result, the surface shape of the steel material is measured. This can be done by deriving. Therefore, in other words, the case where the surface state measuring device measures the distance to the surface of the steel material will be described below as an example. And the example of a change in the case of measuring the other surface state of steel materials will be supplementarily demonstrated suitably.

Moreover, the surface state measuring apparatus according to each embodiment of the present invention mainly uses a magnetic field in order to measure bulging without contact. And this surface state measuring apparatus is equipped with various structures in order to enable a stable and accurate measurement rapidly. Therefore, first, the outline of continuous casting in which measurement is performed will be described, and then the outline of the relationship between the magnetic flux and the bulging amount used by the surface state measuring apparatus will be described, and then the configuration and operation of each embodiment of the present invention Etc. will be described. That is, hereinafter, each embodiment of the present invention will be described in the following order.
1. 1. Outline of continuous casting 2. Relationship between magnetic flux and bulging amount First embodiment

<1. Overview of continuous casting>
Drawing 1 is an explanatory view for explaining an outline of continuous casting which is an example of an application destination of a surface state measuring device concerning each embodiment of the present invention.

  As shown in FIG. 1, the molten steel S1 poured into the mold 2 from the immersion nozzle 1 is solidified from the side surface, and a solidified shell S2 is formed on the side surface. The steel material S on which the solidified shell S2 is formed is drawn out from the floor of the mold 2 as a semi-finished product that is shaped to some extent. At this time, the drawn steel material S is conveyed downward (v-axis positive direction) while being sandwiched by the roll 3, and is secondarily cooled by, for example, cooling water and further solidified. In FIG. 1, although the structure etc. which spray cooling water are abbreviate | omitted, a mode that the solidification shell S2 of the steel material S becomes thick gradually as it pulls out below is shown typically. Such a position directly under the mold 2 is very high in temperature, and the environment is very bad for measuring the surface state of the steel material S such as cooling water splashing. However, the surface state measurement apparatus according to each embodiment of the present invention enables surface state measurement under such adverse conditions.

  On the other hand, as shown in FIG. 1, when the solidified shell S2 is not formed with an appropriate thickness, that is, when solidification is not sufficient, the surface of the steel S between the rolls 3 continuous in the conveying direction of the steel S is The solidified shell S2 cannot withstand the static pressure of the internal molten steel S1 and bends so that it swells. In severe cases, the solidified shell S2 may burst and the molten steel S1 may flow out. Such deformation is also referred to as “bulging deformation”. When this bulging deformation occurs, a large tensile force is generated in the solidified shell S2 immediately below the roll 3. On the other hand, in the solidification process, the steel material S may be at a specific temperature at which it becomes brittle (weakly brittle). If an excessive tensile force due to the bulging deformation or the like is generated at this temperature, the steel material S is cracked.

  Therefore, the presence / absence of this bulging deformation, the shape of bulging B, the amount of bulging Δd (the amount of irregularities in the surface shape of the steel material, etc.), etc. are measured, and the casting speed is reduced or the amount of cooling water is determined depending It is necessary to take an appropriate treatment before the cracking occurs, such as suppressing bulging early by increasing the thickness of the solidified shell S2 by increasing the thickness of the solidified shell S2. The presence / absence of bulging deformation, the shape of bulging B, and the bulging amount Δd can be measured by measuring the surface shape of the steel material, that is, the unevenness generated on the surface. In other words, if the surface shape of the steel material is measured, the partial convex portion of the steel material may correspond to the bulging B, and the amount of protrusion from the other surface of the convex portion corresponds to the bulging amount Δd. .

  Therefore, as shown in FIG. 1, the surface state measuring device 10 according to each embodiment of the present invention is disposed so as to face the surface of the steel material S between the rolls 3 and is fixed in position, up to the surface of the steel material S. The distance (gap) d is measured. That is, as shown in FIG. 2, the surface state measuring apparatus 10 measures the surface shape by repeating the measurement of the distance d to the surface of the steel material S while the steel material S is moving, and bulging the surface shape from the surface shape. The occurrence of deformation and the bulging amount Δd are measured. In addition, in FIG. 2, instead of moving the steel material S in the v-axis positive direction (downward), the measurement state is schematically shown by moving the surface state measuring device 10 in the v-axis negative direction (upward). ing. At this time, it is preferable that two or more surface condition measuring apparatuses 10 are disposed with the steel material S interposed therebetween, and the distance d to both surfaces of the steel material S is measured.

  In order to measure the distance d to the moving steel material S and detect the bulging B by this surface condition measuring device 10, in order to measure the surface shape of the steel material S, it is necessary to measure the distance d quickly. It is. When the moving speed of the steel material S, that is, the continuous casting speed is about 2500 mm / min (42 mm / second), for example, in order to measure the surface shape of the steel material S, every time interval of about 0.1 second or less. It is desirable to measure the distance d. Therefore, it does not simply mean that the distance d can be measured, and it is very important that the measurement time required for one measurement is short. On the other hand, the surface state measuring apparatus 10 according to each embodiment of the present invention described below enables sufficiently quick measurement, and the configuration and the like will be described in detail in the embodiment.

<2. Relationship between magnetic flux and bulging amount>
The relationship between the magnetic flux (output voltage V) and the bulging amount (distance d) used by the surface state measuring apparatus according to each embodiment of the present invention will be described with reference to FIGS. 3 and 4 are explanatory diagrams for explaining the relationship between the magnetic field and the bulging amount used by the surface state measuring apparatus according to each embodiment of the present invention. It should be noted that the relationship described here is a matter found as a result of the inventors of the present invention diligently researching the surface state measurement of the steel material S and the like.

  FIG. 3 shows a partial configuration of the probe set 20 included in the surface state measurement apparatus 10 according to each embodiment of the present invention, more specifically, three probes (first probe 21 to third probe included in the probe set 20. The configuration of one of the probes 23) is schematically shown in the figure. Since the probe set 20 can be used to measure the distance d to the steel material S using a magnetic field, it is also referred to herein as a distance meter (displacement meter). However, this probe set 20 can measure not only the distance d (that is, the surface shape of the steel material S) but also the surface state (for example, magnetic permeability and conductivity) of other steel materials.

  One probe included in the probe set 20 shown in FIG. 3 has, for example, three coils. In FIG. 3, as the three coils, one excitation coil 20I and two detection coils 20Ou and 20Od are arranged. Here, when the excitation coil 20I and the detection coils 20Ou and 20Od are not distinguished, they are simply referred to as coils.

  These three coils all have the same coil characteristics: coil cross-sectional area, coil length, and number of turns. That is, these three coils have the same self-inductance value as a single coil except for external factors such as the surrounding magnetic permeability. Such a coil can be formed, for example, by winding the same coil winding of the same material, thickness, etc. with the same pitch interval, coil area, and number of turns. And as shown in FIG. 3, all three coils are formed with an air core.

  All of these three coils are arranged on the same axis. In other words, the coil axes of the three coils ride on the same straight line. And one coil end surface of each of three coils opposes the surface of the steel material S which is a measuring object. That is, the three coils are all arranged concentrically so that the coil end faces face the steel material S. At this time, the excitation coil 20I is preferably disposed between the detection coil 20Ou and the detection coil 20Od, and the interval between the coils is preferably set equal. Here, for convenience, the coil closer to the steel material S is referred to as a detection coil 20Od, and the far coil is referred to as a detection coil 20Ou. Note that, as described above, the three coils are arranged on the same axis, and this axis is preferably orthogonal to the surface of the steel material S, but it only has to intersect the steel material S. As a result, the three coils arranged in this manner have different distances from the surface of the steel material S. That is, the detection coil 20Od is closest to the steel material S, and is next to the steel material S in the order of the excitation coil 20I and the detection coil 20Ou. Here, the coil end surface facing the surface of the steel material S is taken as an example of the reference position of the exciting coil 20I, and the distance d from the reference position to the surface of the steel material S will be described. However, this reference position is a position for convenience and may be any position of the exciting coil 20I.

  Thus, the probe set 20 disposed on the surface of the steel material S at a predetermined distance generates a magnetic flux Φ when the exciting coil 20I is excited by an alternating current. The magnitude of the magnetic flux Φ depends on the surface state of the steel material S (distance d, conductivity σ, permeability μ). Therefore, the surface state measuring apparatus 10 according to each embodiment of the present invention fixes at least one of the surface states (here, conductivity σ, magnetic permeability μ, which need not be known), and detects the detection coil 20Ou. , 20 Od, it is possible to measure another surface state (here, distance d) from the voltage of the measurement result. More specifically, this relationship will be described below using the distance d as an example.

  Here, the relationship between the distance d and the magnetic flux Φ will be described qualitatively, and the actual output voltage V (an example of an electrical signal) will also be described qualitatively. However, the qualitative contents described here are only for facilitating understanding of the effects and the like of the surface state measuring apparatus 10 according to each embodiment of the present invention, and are not included in the qualitative contents. It does not exclude the principle or action.

  As shown in FIG. 3, when an alternating voltage VI is applied to the exciting coil 20I, an alternating current I flows through the coil winding. As a result, the excitation coil 20I generates an alternating magnetic flux Φ, as can be seen from electromagnetics such as Maxwell's equations (in FIG. 3, the magnetic flux Φ in the steel material S direction is excited).

  A part of the magnetic flux Φ generated by the exciting coil 20I intersects the coil end faces of the detection coils 20Ou and 20Od having the same axis and sandwiching the exciting coil 20I. As a result, an induced electromotive force is generated in the detection coils 20Ou and 20Od, and voltages (potential differences) VOu and VOd are generated between the output terminals, respectively. The surface state measuring apparatus 10 according to each embodiment of the present invention has a differential configuration in which an output voltage V is obtained by taking a difference between these voltages VOu and VOd (V = VOd−VOu). As a result, the surface state measuring apparatus 10 enables more accurate surface state measurement. However, it is also possible to obtain an output voltage by arranging only one of the detection coils without using a differential configuration.

  On the other hand, the magnetic flux Φ generated by the exciting coil 20I depends on the inductance of the exciting coil 20I if the voltage VI and its frequency f are constant, and the inductance of the exciting coil 20I is when the steel material S is arranged in the vicinity. , Depending on the surface state such as the shape (distance d) of the surface of the steel material S, the permeability μ of the steel material S, the conductivity σ of the steel material S, and the like. Therefore, the output voltage V output from the detection coils 20Ou and 20Od also depends on the surface conditions such as the distance d to the steel material S, the magnetic permeability μ of the steel material S, and the conductivity σ of the steel material S. Here, with reference to FIG. 4, the relationship between the distance d and the output voltage V will be described by qualitatively considering the influence due to the magnetic permeability μ and the influence due to the conductivity σ. FIG. 4 is a conceptual graph with the output voltage V (= VOd−VOu) according to the above-described differential configuration as the vertical axis and the distance d as the horizontal axis. However, it goes without saying that the influence of the magnetic permeability μ and the conductivity σ cannot be strictly separated as the output voltage V. In FIG. 4, it is assumed that the frequency f of the alternating current I is constant.

4. Effect of permeability μ of steel S When the steel S is a magnetic body, the magnetic flux Φ generated by the exciting coil 20I is affected by the permeability μ of the steel S, as shown in FIG. At the same time, it is biased toward the steel material S (see FIG. 3). Further, the influence of the permeability μ of the steel material S is greater as the distance d to the steel material S is closer.
In FIG. 4, the correlation F1 schematically represents a change in the output voltage V when the distance d is changed with respect to the steel material S having the permeability μ1 and the conductivity σ1. As can be seen from the correlation F1, as the distance d increases (d1 <d2 <d3), the influence of the magnetic permeability μ1 decreases, and the output voltage V attenuates to about 0 (V1>V2> V3). . This is because when the influence of the magnetic permeability μ1 of the steel material S is small, the amount of the magnetic flux Φ becomes equal in the vertical direction in FIG. 3, and as a result of the same amount of magnetic flux interlinking the detection coils 20Ou, 20Od, each voltage VOu, This is because the absolute values of VOd are equal.
On the other hand, in FIG. 4, the correlation F2 schematically represents a change in the output voltage V when the distance d is changed with respect to the steel material S having the magnetic permeability μ2 and the conductivity σ1. At this time, the magnetic permeability μ2 is larger than the magnetic permeability μ1. The correlation F2 also changes in the same manner as the correlation F1, but since the magnetic permeability μ2 is large, the magnetic flux Φ is larger than that of the correlation F1, and the output voltage V is also largely biased toward the steel material S side. It is getting bigger.
That is, in the case of a magnetic material, it can be seen that the output voltage V has a smaller absolute value as the distance d increases, and that the output voltage V increases in the positive direction when the magnetic permeability μ increases.

Influence of conductivity σ of steel material S On the other hand, whether the steel material S is a magnetic material or a non-magnetic material, as shown in FIG. 3, the alternating magnetic flux Φ generated by the exciting coil 20I links the surface thereof. The eddy current Iw flows so as to generate a magnetic flux Φw in a direction that cancels the magnetic flux Φ. As a result, when described with a magnetic material, as shown in FIG. 3, the magnetic flux Φ biased toward the steel material S due to the magnetic permeability μ of the steel material S is reversed in the direction away from the steel material S due to the magnetic flux Φw of the eddy current Iw. Is pushed back. As a result, the difference in magnetic flux that links the detection coils 20Ou and 20Od decreases, and the output voltage V (= VOd−VOu) changes in the negative direction. The influence due to the conductivity σ of the steel material S, that is, the influence due to the eddy current Iw becomes small as the distance d increases, similarly to the influence due to the magnetic permeability μ of the steel material S, regardless of whether the material is magnetic or non-magnetic. . Therefore, the change in the negative direction of the output voltage V due to the influence of the conductivity σ of the steel material S also decreases as the distance d increases. Therefore, when the distance d or the like is constant, the output voltage V to the magnetic material is determined by subtracting the influence of the conductivity σ of the steel material S and the influence of the magnetic permeability μ of the steel material S described above. In the case of a magnetic material, the influence of the electrical conductivity σ of the steel material S is smaller than the influence of the magnetic permeability μ of the steel material S. Therefore, as shown in the correlations F1 and F2 in FIG. 4, the output voltage V (= VOd -VOu) is often positive.
On the other hand, in FIG. 4, the relationship with respect to a nonmagnetic material is shown by correlation F3, F4. In the case of a non-magnetic material, the magnetic permeability μ (μ3, μ4) of the steel material S is smaller than that of the magnetic material, and the influence of the magnetic permeability μ is little or small. Therefore, the influence of the eddy current Iw described here due to the magnetic flux Φw is increased, and the magnetic flux Φ generated by the exciting coil 20I is biased away from the surface of the steel material S. As a result, as shown in FIG. 4, the output voltage V (= VOd−VOu) is often negative. In these correlations F3 and F4, as the distance d increases, the influence of the electrical conductivity σ of the steel material S decreases as described above, so the output voltage V attenuates to about zero. Again, when the influence of the electrical conductivity σ of the steel material S is small, the amount of the magnetic flux Φ is equal to the vertical direction in FIG. 3, and as a result of the same amount of magnetic flux interlinking the detection coils 20Ou, 20Od, each voltage VOu, This is because the absolute values of VOd are equal. Further, in the non-magnetic material, when the conductivity σ increases (σ3> σ4), the influence of the conductivity σ of the steel material S becomes stronger, so the absolute value of the output voltage V also increases. In this case, the output voltage V increases in the negative direction.
In other words, in the case of a non-magnetic material, it can be seen that the absolute value of the output voltage V decreases as the distance d increases, and the output voltage V increases in the negative direction when the conductivity σ increases.

In summary, the following can be said.
In the case of a magnetic material, an eddy current Iw is generated due to the influence of the magnetic flux Φ and the electrical conductivity σ, preventing the change of the magnetic flux Φ in the direction of the steel S, but moreover, due to the effect of the high permeability μ, the magnetic flux Φ Is biased toward the steel material S, and the output voltage V becomes a positive value. Further, the output voltage V increases as the distance d is shorter. As the magnetic permeability μ increases, the output voltage V also increases. However, when the conductivity σ is large, the output voltage V decreases. However, the influence of the conductivity σ is smaller than the influence of the magnetic permeability μ.
In the case of a non-magnetic material, the influence of the magnetic permeability μ is small and negligible, but the eddy current Iw is still generated due to the influence of the magnetic flux Φ and the conductivity σ, pushing the magnetic flux Φ away from the steel material S. Therefore, the output voltage V becomes a negative value. Further, the output voltage V increases in the negative direction as the distance d is shorter.
Here, the case where the output voltage V is a differential signal between two upper and lower coils with a differential configuration has been described. However, it is possible to use either one of the detection coils. In this case, it goes without saying that there is a relationship similar to the relationship described here from the same consideration regarding the output value of the output voltage V, the positive / negative increase / decrease, and the like.

  The relationship between the magnetic flux (output voltage V) and the bulging amount (distance d) has been described above. The inventors of the present invention conducted intensive studies on the surface state measurement and the like of the steel material S. As a result, these relationships were clarified and the embodiments of the present invention were completed. Hereinafter, each embodiment will be described. Note that the items described here are qualitative and do not limit the cause or action, and the value of the output voltage V depends on the device configuration such as the coil characteristics and arrangement position. Dependent. Therefore, the surface state measuring apparatus 10 according to each embodiment of the present invention obtains a correlation F with respect to a desired steel material S from an experiment or the like in advance with a predetermined configuration, and determines the surface state (from the correlation F and the output voltage V). It is possible to measure distance d, conductivity σ or permeability μ). Furthermore, the surface state measuring apparatus 10 has various configurations so that not only this relationship can be simply used but also stable and accurate measurement can be performed quickly. Therefore, it goes without saying that the characteristics of the surface state measuring apparatus 10 according to each embodiment of the present invention are not limited to the matters described here. Hereinafter, the surface state measuring apparatus 10 according to the first embodiment of the present invention will be described in detail.

<3. First Embodiment>
First, the configuration and the like of the surface state measuring apparatus 10 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 5 is an explanatory diagram for describing a configuration and the like of the surface state measurement apparatus 10 according to the first embodiment of the present invention.

(3-1. Configuration of surface condition measuring apparatus)
As shown in FIG. 5, the surface state measuring apparatus 10 roughly includes an exciting unit 11, a probe set 20, a magnetic flux detector 30, and a surface state deriving unit 40.

The outline of each component will be described as follows.
The probe set 20 has three probes including one excitation coil shown in FIG. 3 as described above, and the excitation unit 11 supplies an alternating current to the probe set 20, and the total of the probe set 20 has. 3 excitation coils are sequentially excited. The magnetic flux detection unit 30 detects a voltage representing a change in magnetic flux due to the excitation using a detection coil, and performs signal processing to convert the voltage into a predetermined differential electrical signal. The electric signal is sent to the surface state deriving unit 40, and the surface state deriving unit 40 derives the surface state (here, distance d) of the steel material S based on the electric signal.

  In the above “relationship between magnetic flux and bulging amount”, that is, “relationship between output voltage V and distance d”, from one excitation coil 20I and two detection coils 20Ou and 20Od for one distance d, The case where the differential output voltage V of 1 is measured has been described. In the continuous casting machine which is an application example of the present embodiment, as shown in FIGS. 1 and 2, etc., the distance d to the steel material S is measured. However, the conductivity σ and the magnetic permeability μ of the steel material S are measured. The exact value of the surface state is often unknown at the time of measurement. In particular, when measuring a steel material S in a temperature range around the Curie point (about 770 ° C.), since the nonmagnetic material changes to a magnetic material across the Curie point, the change in permeability μ etc. is very large. It will be a thing. That is, it is often necessary to measure the surface state of the steel material S in which all three surface states (distance d, conductivity σ, magnetic permeability μ) are unknown or at least one of the surface states changes greatly. Therefore, it is difficult to measure the distance d using the magnetic flux Φ as described above.

  On the other hand, the surface state measuring apparatus 10 according to the first embodiment of the present invention measures the output voltage V based on the change of the magnetic flux Φ reflecting the surface state by excitation from three different positions d. This makes it possible to derive the surface state. That is, the surface state measuring apparatus 10 includes three excitation coils, and the excitation coils are arranged side by side so that the distances d from the surface of the steel material S are different from each other, and the output voltage V from each excitation coil is obtained. It is possible to measure the surface condition. For example, for three unknown variables (surface states), it is possible to measure values corresponding to three equations and derive at least one variable from the result. Further, the distance d from each of the three exciting coils to the steel material S is not necessarily different, and the surface state measuring apparatus 10 is different in the distance d on the same axis intersecting the surface of the steel material S. By generating the magnetic flux Φ from three locations, it is possible to perform accurate and rapid measurement. If the exciting coil is not on the same axis, the surface of the steel material S is flat, and if the distance from the reference of the distance d to the surface is constant, the distance d can be measured even if it is not on the same axis. There is also. However, it is very difficult to measure the surface shape (one of the surface states) of the moving steel material S, which is a measurement target in each embodiment of the present invention, when excitation points are not on the same axis. Therefore, the surface state measuring apparatus 10 completed by the present inventors, which has clarified the nature of the moving steel material, has the surface shape of the moving steel material S by, for example, setting the excitation location on the same axis. Measurement is also possible. At first glance, in order to increase the magnetic flux Φ contributing to the measurement, it is considered that the measurement accuracy can be improved by providing a core in the exciting coil. However, the present inventors have also clarified that when the excitation location is on the same axis, if a core is provided, the correlation between the excitation coils becomes too strong and measurement becomes difficult. Therefore, not only on the same axis, the surface state measuring apparatus 10 according to the present embodiment can measure the surface state by using each exciting coil as an air core. On the other hand, as shown in FIG. 4, the absolute value of the output voltage V decreases as the distance d increases. When the exciting coils are arranged on the same axis, the distances (Δd1, Δd2) between the exciting coils are limited values compared to the case where the exciting coils are not arranged on the same axis. Therefore, the surface state measuring apparatus 10 according to the present embodiment described below has a probe set 20 (second example of a probe set) that is further improved in order to reduce the distance between the exciting coils. It is also possible to increase. However, when a desired measurement accuracy can be obtained, the surface state measurement apparatus 10 according to the present embodiment has a probe set 20 (first example of a probe set) in which the distances (Δd1, Δd2) between the excitation coils are limited. Can also be used. Therefore, in the following, each configuration of the surface state measurement apparatus 10 according to the present embodiment will be described. However, in order to facilitate understanding of the effects and the like of the probe set 20, in the description of the probe set 20, After describing the first example, a second example of a further improved probe set will be described.

(Excitation part 11)
The excitation unit 11 applies AC voltage to the three excitation coils of the probe set 20 within one measurement time, and excites all three excitation coils at least once (the AC voltage is applied once or more). Apply). Therefore, it is desirable that the excitation unit 11 has a circuit such as an AC power supply. In addition, since the surface state measuring apparatus 10 according to the present embodiment can reduce the time required for signal processing at the time of deriving the surface state, the one measurement time is made sufficiently shorter than the speed at which the steel material S advances. Is possible. Moreover, the one measurement time said here means the time interval which measures the distance d once. Temporarily, the surface state measuring apparatus 10 according to the present embodiment makes it possible to set the measurement time to about 0.1 second or less when the continuous casting speed is about 42 mm / second. In this case, the resolution in measuring the surface shape of the steel material S is about 4.2 mm, and measurement with very high accuracy is possible.

  As described above, the excitation unit 11 sequentially applies an alternating current to the three excitation coils within one measurement time to excite the three excitation coils one by one. That is, the excitation unit 11 selects, for example, the first excitation coil and excites it within one measurement time, then selects and excites the second excitation coil, and selects the third excitation coil. Excited. Therefore, it is desirable that the excitation unit 11 has an excitation coil selection unit. The order of excitation and the number of excitations within one measurement time are not particularly limited. In the probe set 20 described below, in the case of the second example of the probe set, it is possible to shorten the intervals (Δd1, Δd2) between the excitation coils by exciting one excitation coil as described above. Measurement accuracy can be improved. The configuration for improving the measurement accuracy will be described in detail in the description of the second example of the probe set.

  Further, the excitation unit 11 applies an alternating current having at least two frequencies to each excitation coil within one measurement time. That is, it is desirable that the exciting unit 11 excites each exciting coil at the two frequencies by applying alternating currents having two different frequencies to all the exciting coils. The surface state measurement apparatus 10 according to the present embodiment enables more reliable surface state measurement by using the frequency of 2 as described above. Therefore, it is desirable that the excitation unit 11 has, for example, two types of AC power supplies or a frequency conversion circuit. The use of these two frequencies will be described with reference to FIGS. FIG. 6 is an explanatory diagram for explaining a dead zone in the relationship between the magnetic field used by the surface state measurement apparatus according to each embodiment of the present invention and the relationship between the bulging amounts.

  In FIG. 4, “Relationship between magnetic flux and bulging amount”, that is, “Relationship between output voltage V and distance d” depends on the surface state of steel S (distance d, conductivity σ, permeability μ). Explained. However, the output voltage V may be zero depending on the balance of the distance d, the conductivity σ, the magnetic permeability μ, and the like. Here, such a state is also referred to as a “dead zone”. FIG. 6 shows the correlation FN that has entered the dead zone.

  As shown in FIG. 6, the output voltage V of the correlation FN is 0 regardless of the distance d due to the balance of the conductivity σ, the magnetic permeability μ, and the like. In this case, even if the output voltage V is obtained by the three exciting coils, the output voltage V becomes 0 or an effective output value cannot be obtained, and it becomes difficult to identify the correlation.

  On the other hand, the output voltage V depends on the magnetic flux Φ, and the magnetic flux Φ depends not only on the coil characteristics of the exciting coil but also on the frequency f of the exciting current. The inventors of the present invention have found that this can be used to prevent the dead zone, and have also found that the output voltage V increases in the negative direction as the frequency increases. Therefore, the surface state measuring apparatus 10 according to the present embodiment succeeds in excluding the case where the measurement becomes impossible due to the dead band by performing the measurement at the two frequencies f1 and f2 using this relationship. .

This will be described more specifically.
Here, for the steel material S, which is a magnetic body having the conductivity σ1 and the permeability μ1, for example, the correlation when the AC voltage of the frequency f1 is used is the correlation F5, and the correlation is when the frequency f2 is used. Assume F6 and the frequency f1 is greater than the frequency f2. Then, as shown in FIG. 6, it can be seen that the correlation F6 can obtain a higher output voltage V than the correlation F5 if the distance d is the same.
On the other hand, for the steel material S which is a non-magnetic material having conductivity σ3 and permeability μ3, for example, the correlation when using an alternating voltage of frequency f1 is set as correlation F7, and the correlation when using frequency f2 is used. Assume F8, and the frequency f1 is greater than the frequency f2. Then, as shown in FIG. 6, it can be seen that the correlation F7 can obtain an output voltage V higher than the correlation F8 if the distance d is the same.
Therefore, the surface state measuring apparatus 10 according to the present embodiment performs measurement by applying a two-frequency AC voltage from the excitation unit 11, and uses the frequency having the larger absolute value of the output voltage V to determine the surface state. By deriving, it is possible to avoid the dead zone.

  However, when the dead zone can be avoided, it is needless to say that measurement can be performed using only one frequency. In addition, when the excitation unit 11 applies an alternating voltage of two frequencies f1 and f2 to each excitation coil, the two frequencies f1 and f2 can be applied at different times. The surface state measuring apparatus 10 superimposes these two frequencies f1 and f2, and obtains an output voltage V for both frequencies f1 and f2 within one application time. Therefore, the surface state measuring apparatus 10 can shorten one measurement time, and can perform very quick measurement as described above. Although the case where the two frequencies f1 and f2 are superposed has been described here, the number of frequencies to be superposed is not limited to two, and may be three or more. When three or more frequencies are superimposed and applied to each excitation coil, it is possible to obtain a plurality of sets of output voltages V that avoid the dead zone. Therefore, in this case, by using a set having a large absolute value of the output voltage V, it is possible to measure the surface state with less errors. Furthermore, in this case, the surface state can be measured with less error by deriving the surface state for each of a plurality of sets of output voltages V that avoids the dead zone and taking the average value of the surface state.

(Probe set 20)
As for the probe set 20, the conceptual configuration for one probe is shown in FIG. 3, but as described above, the surface state measuring apparatus 10 according to the present embodiment has three probes as illustrated in FIG. As a result, a total of three exciting coils are provided. Therefore, conceptually, three exciting coils 20I shown in FIG. 3 are provided. On the other hand, two detection coils 20Ou and 20Od are provided for each excitation coil. As an example, a first example of the probe set 20 shown in FIG. Here, a set of one excitation coil and a detection coil that detects the magnetic flux Φ of the excitation coil is called a probe, and for convenience, the first probe 21, the second probe 22, and the third probe are sequentially arranged from the side closer to the steel material S. It will be called a probe 23. That is, when showing each probe, it says the 1st-3rd probe 21-23, and when showing the whole 1st-3rd probe 21-23, it says the probe set 20.

  In the following, a first example (FIG. 7) of a probe set that is easy to understand from FIG. 3 will be described first, and then a second example of a further improved probe set that can improve measurement accuracy and the like. (FIG. 8) will be described. In this case, in the second example of the probe set, the same configuration as that of the first example of the probe set is omitted, and description will be made mainly on points different from the first example of the probe set.

(First example of probe set 20)
The probe set 20 according to the first example will be described with reference to FIG. FIG. 7 is an explanatory diagram for describing a first example of a probe set included in the surface state measurement apparatus according to the first embodiment of the present invention.

  As shown in FIG. 7, the probe set 20 includes three first to third probes 21 to 23 each having one exciting coil. First, each of the exciting coils 21I to 23I will be described.

  As shown in FIG. 7, the three exciting coils 21I to 23I have different distances d from the surface of the steel material S (distances d1, d2, and d3). That is, for example, when the position of the coil end surface facing the surface of the steel material S is used as a reference, the distance d from each reference is the distance d1 in the exciting coil 21I, the distance d2 in the exciting coil 22I, and the distance in the exciting coil 23I. Each exciting coil 21I-23I is arrange | positioned so that it may become d3. However, the reference of the distance d is not limited to the position of one coil end face, and can be set by changing as appropriate.

  In addition, all of the three exciting coils 21I to 23I are arranged on the same axis AX. In other words, the coil axes of the three exciting coils are on the same straight line. And one coil end surface of each of three exciting coils opposes the surface of the steel material S which is a measuring object. That is, the three exciting coils are all arranged side by side concentrically so that the coil end faces face the steel material S. At this time, it is desirable that the intervals between the exciting coils (Δd1 = d2−d1, Δd2 = d3−d2) are set to be equal. As described above, the three exciting coils are arranged on the same axis AX, and this axis AX is preferably orthogonal to the surface of the steel material S, but it only has to intersect the steel material S. As described above, by arranging all the exciting coils on the same axis AX, it is possible to measure the same portion of the steel material S to be moved within one measurement time, and to shorten the measurement time.

  The three exciting coils 21I to 23I all have the same coil characteristics. That is, the three exciting coils have the same self-inductance value as a single coil except for external factors such as the surrounding magnetic permeability. Such an exciting coil can be formed, for example, by winding the same coil winding of the same material, thickness, etc. with the same pitch interval, coil area, and number of turns. The three exciting coils 21I to 23I are all formed of an air core as shown in FIG. By constructing the exciting coil arranged on the same axis with an air core, the interaction between the exciting coils is reduced, thereby enabling more accurate measurement.

  The probe set 20 according to the first example has two detection coils corresponding to the respective excitation coils 21I to 23I in each of the first to third probes 21 to 23. That is, the first probe 21 is provided with detection coils 21Od and 21Ou above and below the excitation coil 21I (on the side closer to and far from the steel S on the axis AX), and the second probe 22 is detected above and below the excitation coil 22I. The coils 22Od and 22Ou are arranged, and the third probe 23 is arranged with detection coils 23Od and 23Ou above and below the exciting coil 23I.

  The detection coils 21Od to 23Ou correspond to the detection coils 20Ou and 20Od for the excitation coil 20I shown in FIG. 3 with respect to the excitation coils 21I to 23I in the first to third probes 21, 22, and 23, respectively. . That is, taking the first probe 21 as an example, the excitation coil 21I corresponds to the excitation coil 20I, the detection coil 21Ou corresponds to the detection coil 20Ou, and the detection coil 21Od corresponds to the detection coil 20Od.

  The detection coils 21Od to 23Ou are formed in the same manner as the detection coils 20Ou and 20Od in FIG. In other words, taking the first probe 21 as an example, the detection coils 21Ou and 21Od have the same coil characteristics as the excitation coil 21I and are formed of an air core, and the excitation coil 21I and the coil axis coincide with each other. The coil end faces are arranged side by side above and below the exciting coil 21I so as to face the steel material S.

  As a result, the probe set 20 as a whole has a total of nine coils, each coil has the same coil characteristics and is formed of an air core, and all the coil axes are aligned on the same straight line. One coil end face of the steel plate faces the surface of the steel material S.

  In the probe set 20 thus formed, the first to third probes 21 to 23 are sequentially excited by the excitation unit 11 with an alternating voltage VI on which two frequencies f1 and f2 are superimposed one by one. An output voltage is output from the detection coil. The selection of which excitation coil 21I to 23I of the first to third probes 21 to 23 is applied with the AC voltage VI is performed by the excitation unit 11 as described above, while which of the detection coils 21Od to 23Ou is selected. The selection of whether or not to obtain the output is selected by the magnetic flux detection unit 30 described below in synchronization with the excitation of the excitation unit 11. The probe set 20 may have a differential configuration so that the differential outputs (output voltages V1 to V3) are output from the first to third probes 21 to 23, respectively. In the surface state measurement apparatus 10 according to the embodiment, the magnetic flux detection unit 30 has such a differential configuration.

The first example of the probe set 20 has been described above.
As shown in FIG. 7, the probe set 20 according to the first example has nine combined coils, and the coils are arranged on the same straight line. Therefore, two detection coils are arranged between the excitation coils. On the other hand, as shown in FIG. 6, the absolute value of the output voltage V attenuates as the distance d increases. Therefore, in order to keep the absolute value of the output voltage V large and improve the measurement accuracy, it is desirable to reduce the distances Δd1 and Δd2 between the exciting coils. Therefore, in the probe set 20 according to the first example, for example, two detection coils adjacent to each other (the detection coil 21Ou and the detection coil 22Od, and the detection coil 22Ou and the detection coil 23Od) are used as one common detection coil. It is also possible. On the other hand, in the probe set 20 of the second example described below, the distances Δd1 and Δd2 between the exciting coils can be further reduced to improve the measurement accuracy. The probe set 20 of the second example will be described with reference to FIG.

(Second example of probe set 20)
FIG. 8 is an explanatory diagram for describing a second example of the probe set included in the surface state measurement apparatus according to the second embodiment of the present invention.

  As shown in FIG. 8, the probe set 20 according to the second example also includes three first to third probes 21 to 23 each having one exciting coil. Each of the exciting coils 21I to 23I is configured in the same manner as the probe according to the first example (FIG. 7). However, in the probe set 20 of the second example, the detection coils 21Ou, 22Od, 22Ou, and 23Od arranged between the respective excitation coils 21I to 23I are omitted, and the detection coil 21Od and the detection coil 23Ou are used as detection-dedicated coils. Have only. And exciting coil 21I-23I is utilized as a coil for detecting a differential signal. In other words, the excitation coils 21I to 23I are used as detection coils while other adjacent excitation coils are excited. That is, as shown in Table 1 below, the surface state measurement apparatus 10 according to the present embodiment has a magnetic flux Φ in the excitation coil 22I instead of the detection coil 21Ou of the first probe 21 when the excitation coil 21I is excited. When the excitation coil 22I is excited, instead of the detection coils 22Od and 22Ou of the second probe 22, the excitation coils 21I and 23I detect the magnetic flux Φ, and the excitation coil 23I is excited. In this case, instead of the detection coil 23Od of the third probe 23, the excitation coil 22I detects the magnetic flux Φ.

  In other words, in the probe set 20 according to the second example, the three exciting coils 21I to 23I are arranged adjacent to each other on the coaxial AX as shown in FIG. Detection coils 21Od and 23Ou are arranged one by one at positions closer to and farther from the surface of the steel material S than the three excitation coils 21I to 23I. On the other hand, as described above, from which detection coil the output voltage V is obtained is selected by the magnetic flux detection unit 30 described below. In this case, the magnetic flux detection unit 30 is excited by one excitation coil. 2, two other exciting coils or one other exciting coil and one detecting coil arranged adjacent to the one exciting coil are selected, and the output voltage V is acquired from the selected coil. .

  The configuration of the probe set 20 according to the second example shown in FIG. 8 has been described for the case where all the excitation coils 21I to 23I are used not only for excitation but also for detecting the magnetic flux Φ. The excitation coil may be used as a detection coil for detecting magnetic flux with respect to the excitation coil being excited. For example, in the configuration of the probe set 20 according to the first example shown in FIG. 7, only the detection coil between the excitation coil 21I and the excitation coil 22I is omitted, or between the excitation coil 22I and the excitation coil 23I. It is also possible to omit only the detection coil. In this case, the upper and lower excitation coils (excitation coil 21I and excitation coil 22I or excitation coil 22I and excitation coil 23I) of the omitted detection coil are used not only for excitation but also for detecting magnetic flux Φ. The excitation coil in which the detection coil is arranged is used only for excitation. Further, in the case where the differential configuration is not used when detecting the magnetic flux Φ, that is, when the magnetic flux Φ on one side of one exciting coil is detected, the configuration of the probe set 20 according to the second example shown in FIG. Further, the detection coil 21Od or the detection coil 23Ou can be omitted.

  In the case of having the probe set 20 of the second example, the surface state measuring apparatus 10 does not need to insert a detection coil between the respective excitation coils. Therefore, the distance Δd1 (= d2-d1) between the respective excitation coils 21I to 23I. , Δd2 (= d3−d2) can be reduced. As a result, the surface state measuring apparatus 10 can increase the absolute value of the output voltage V, which is a detection signal, and can improve the measurement accuracy. In the following, the case where the probe set 20 according to the second example shown in FIG. 8 is used will be described.

(Magnetic flux detector 30)
The magnetic flux detection unit 30 detects the magnetic flux Φ generated by each of the exciting coils 21I to 23I and converts it into an electrical signal (here, output voltage V) used for derivation of the surface state. As described above, the magnetic flux detection unit 30 selects two coils adjacent to the excited excitation coil as the detection coil used for detecting the magnetic flux Φ, and outputs two voltages from each of the coils. VOu and VOd are acquired, and an output voltage V that is a differential signal is output based on the voltages VOu and Vod. At this time, when the probe set 20 according to the second example shown in FIG. 8 is used, the detection coil is selected from the excitation coil that is not excited and the two detection coils 21Od and 23Ou. Further, as described above, since the excitation unit 11 applies an alternating current on which the two frequencies f1 and f2 are superimposed to the excitation coil, the two voltages VOu and VOd include two frequency components. Therefore, the magnetic flux detection unit 30 separates the two frequency components and outputs an output voltage V that is an electric signal for each of the frequencies f1 and f2. Here, the output voltage is the output voltage VA for the frequency f1, and the output voltage VB for the frequency f2.

  As shown in FIG. 5, the magnetic flux detection unit 30 has a specific configuration for performing the above processing. As illustrated in FIG. 5, the voltage acquisition unit 31, the differential amplification unit 32, the frequency separation unit 33, and the electric signal output units 341 and 342. With.

  In synchronism with the excitation unit 11, the voltage acquisition unit 31 uses two excitation coils from the excitation coils 21I to 23I and the detection coils 21Od and 23Ou with respect to the one excitation coil 21I to 23I excited by the excitation unit 11. select. And the voltage acquisition part 31 acquires voltage VOu and VOd showing magnetic flux (PHI) which the exciting coil generate | occur | produced from each of the selected detection coil.

  The differential amplifier 32 takes the difference between the voltages VOu and VOd acquired by the voltage acquisition unit 31 (V = VOd−VOu) and amplifies the difference signal.

  The frequency separation unit 33 separates the electric signal obtained by the differential amplification unit 32 by taking the difference, and separates the electric signal into signals of the two frequencies f1 and f2, and outputs them to the electric signal output units 341 and 342, respectively. For this purpose, the frequency separation unit 33 may include, for example, two bandpass filters that extract the electrical signals of the frequencies f1 and f2.

  The electric signal output units 341 and 342 have a maximum value detection circuit and a phase detection circuit for the excitation signal (AC voltage by the excitation unit 11), respectively, and positive or negative for each frequency f1 and f2 from the input electric signal. Output voltages VA and VB (an example of electrical signals) are generated and output. More specifically, the electrical signal output unit 341 that has acquired the electrical signal having the frequency f1 separated by the frequency separation unit 33 detects the maximum value of the electrical signal by the maximum value detection circuit and is further excited by the phase detection circuit. The phase of the electrical signal with respect to the signal is detected. The electrical signal output unit 341 determines that the sign is positive and the value is the above value if the phase of the electrical signal is advanced by 90 ° with respect to the excitation signal (the phase difference may be 0 ° or more and less than 180 °). An output voltage VA that is the detected maximum value is output. On the other hand, if the phase of the electrical signal is delayed by 90 ° with respect to the excitation signal (the phase difference may be −180 ° or more and less than 0 °), the electrical signal output unit 341 sets the sign to a negative value. The output voltage VA having the detected maximum value is output. On the other hand, the electrical signal output unit 342 generates the output voltage VB by performing the same processing on the electrical signal having the frequency f2 separated by the frequency separation unit 33.

(Surface state deriving unit 40)
The surface state deriving unit 40 is based on the electrical signal converted by the magnetic flux detecting unit 30 and the surface state of the steel material S at the position where the probe surface of the probe set 20 is opposed within one measurement time (here, the distance d, that is, the surface). Shape). At this time, the magnetic flux detection unit 30 outputs the output voltages VA and VB of the two frequencies, but the surface state deriving unit 40 compares the output voltages VA and VB and outputs the output voltage for the frequency having the larger absolute value. The larger one is selected when both output voltages are positive, and the smaller one is used when negative. As described with reference to FIG. 6, the surface state measuring apparatus 10 can eliminate the dead zone and can reliably measure the surface state. Further, the surface state deriving unit 40 outputs the output voltage V and the distance d measured in advance for each steel material S under a plurality of conditions in which the permeability μ and the conductivity σ are changed by changing the temperature at the time of measurement. 3 (an example of the relationship between the electrical signal and the surface state, corresponding to the above correlation) is recorded, and three probes (first to third probes 21 to 23) measured within one measurement time are recorded. Based on the output voltages V1 to V3 for each, the correlation of the steel material S to be measured is determined, and at least one or more output voltages V1 to V3 are applied to the correlation to derive the distance d.

  Therefore, the surface state deriving unit 40 includes a surface state deriving unit 40, a frequency selecting unit 41, a correlation determining unit 42, a correlation storing unit 43, a surface state specifying unit 44, and a surface state storing unit 45. A surface state change output unit 46, a surface state acquisition unit 47, and a correlation derivation unit 48. Each configuration will be described below. First, it is assumed that the correlation is recorded in advance, and then, the surface state acquisition unit 47 and the correlation derivation unit 48 that are configurations for recording the correlation will be described. .

  Note that examples of the correlation between the output voltage V and the distance d include the correlations F1 to F8 as shown in FIGS. 4 and 6, but here, the correlation F9 as shown in FIG. , F10 will be described as an example. Further, the correlation measured in advance may be expressed as a function in which the output voltage V is substituted and the distance d is output. However, in order to shorten one measurement time, it is desirable to use a lookup table in which the distance d is specified by the three output voltages V1 to V3 as the correlation. However, in the following description, in order to facilitate understanding of the process of deriving the distance d, first, a case where the correlation is a function will be described, and then a case where a lookup table is used will be described.

(Configuration to derive the surface state)
The frequency selection unit 41 compares the output voltages VA and VB of the two frequencies f1 and f2 acquired from the magnetic flux detection unit 30, and determines which frequency f1 and f2 is used for surface state derivation. At this time, the frequency selection unit 41 may compare any of the output voltages V1 to V3 of the first to third probes 21 to 23, but the output voltage V1 of the first probe 21 closest to the steel material S is the highest. Since it becomes a large signal, it is desirable to compare the output voltages V1 and select a frequency having a larger absolute value (a larger value if V1 is positive and a smaller value if negative). The output voltages V1 to V3 corresponding to the selected frequency are output to the correlation determining unit 42 and the correlation deriving unit 48. At this time, it is desirable that information indicating which frequency is used is also output to the correlation determining unit 42 and the correlation deriving unit 48.

  The correlation determining unit 42 is a correlation used for deriving the surface state from the correlation recorded in advance in the correlation storage unit 43 based on the output voltages V1 to V3 corresponding to the frequency selected by the frequency selecting unit 41. To decide. The distance d at which each of the three output voltages V1 to V3 is measured is unknown, but the distances Δd1 and Δd2 between them are known, so that the correlation determining unit 42 determines the one from the output voltages V1 to V3. Correlation can be determined. For example, as shown in FIG. 9, a plurality of correlations F9 and F10 are recorded in the correlation storage unit 43 in advance. Therefore, the correlation determining unit 42 selects a correlation on which the three output voltages V1 to V3 are multiplied from the plurality of correlations F9 and F10. In FIG. 9, the horizontal axis is the output voltage V, the vertical axis is the distance d, the three output voltages V1 to V3 are # 1 to # 3, respectively, and the output voltages V1 to V3 for each measurement are indicated by ●, ▲, and □. expressed. For example, assume that output voltages V1 to V3 of ● (black circles) are obtained within one measurement time. Then, in this case, the correlation determining unit 42 determines the correlation function F9 on which ● # 1 to # 3 are multiplied. Further, for example, assume that output voltages V1 to V3 of ▲ (black triangle) are obtained within one measurement time. Then, in this case, the correlation determination unit 42 determines the correlation function F9 on which ▲ # 1 to # 3 ride. On the other hand, for example, assume that □ (white square) output voltages V1 to V3 are obtained within one measurement time. Then, in this case, the correlation determining unit 42 determines the correlation function F10 on which □ # 1 to # 3 are multiplied. Since ● and ▲ are on the same correlation F9, it means that these measurements were performed when the distance d was different for the steel material S having the same surface state.

  The surface state specifying unit 44 specifies the distance d, which is an example of the surface state to be measured, by applying at least one output voltage V1 to V3 to the correlation determined by the correlation determining unit 42. That is, when the correlation is a function for deriving the distance d when the output voltage V is input, the surface state specifying unit 44 substitutes, for example, the output voltage V1 for the correlation determined by the correlation determining unit 42. To derive the distance d. The reason why the output voltage V1 is used here is that the output voltage V1 can take a larger absolute value than the other output voltages V2 and V3, so that the measurement accuracy can be improved. However, it is of course possible to use other output voltages V2, V3. Furthermore, an example is given and demonstrated concretely. The same correlation F9 is selected when the output voltages V1 to V3 are ● and ▲. However, when the output voltage V1 (● # 1, ▲ # 1) is assigned to the correlation F9, the derived distance d is different, and it is derived that both are the same steel material S but the distance d is different. The On the other hand, although the values of the output voltage V1 (● # 1, □ # 1) are substantially equal, the correlations F9 and F10 are different, so both are the measurement results for different steel materials S and the derived distance d is also different. I understand that. The distance d derived in this way is recorded in the surface state storage unit 45 as a temporal change (history) of the surface state (distance d).

  Here, the case where the correlation is a function having the output voltage V as an input and the distance d as an output has been described. However, when other surface states (conductivity σ, magnetic permeability μ) are derived instead of the distance d, the surface state deriving unit 40 receives the output voltage V as a correlation and outputs the surface state as an output. It is possible to use functions. Further, as described above, the correlation may be a lookup table that specifies the distance d (and / or other surface state) with the three output voltages V1 to V3. In this case, the output voltages V1 to V3 of 3 and the distance d (and / or other surface state) associated therewith are recorded in the correlation storage unit 43 as a lookup table. Then, the correlation determining unit 42 determines data (another example of the correlation) in which the measured three output voltages V1 to V3 are recorded from the lookup table, and the surface state specifying unit 44 The distance d (and / or other surface conditions) associated with the determined data may be specified.

  The surface state change output unit 46 outputs the time change of the surface state recorded in the surface state storage unit 45 to a display device such as a monitor for display. In this case, the output change in the surface state represents a change in the distance d from the surface state measuring device 10 as shown in FIGS. 1 and 2 to the surface of the moving steel S, and the magnitude of this change is This corresponds to the bulging amount Δd. Accordingly, the surface state change output unit 46 may calculate the bulging amount Δd, determine whether or not the value exceeds a threshold value, and output a determination result of whether or not bulging B has occurred.

(Configuration to derive correlation)
Here, a configuration for deriving the correlation will be described. As described above, the correlation not only depends on the surface state (distance d, conductivity σ, permeability μ) of the steel material S, but also the frequency f, the configuration of the probe set 20 and the magnetic detection unit 30, and the like. Also depends on. Therefore, by measuring the steel material S whose surface state is known by the probe set 20 and the magnetic detection unit 30 used for actual measurement, between the output voltage V and the surface state (for example, distance d) of the steel material. The correlation is derived.

  The surface state acquisition unit 47 acquires the surface state (distance d, conductivity σ, permeability μ) of the steel material S that is being measured to derive the correlation. The surface state acquisition unit 47 acquires the surface state from input data from a host controller or operator that controls the surface state measuring apparatus 10. In addition, when acquiring a surface state from the input data by an operator, the operator can use a contact type conductivity meter for the conductivity σ, and a contact type permeability meter for the permeability μ, for example. Can be used. And an operator inputs the measurement result by these measuring instruments into surface state deriving part 40 via an input device (not shown), and surface state acquisition part 47 will acquire this input data.

  The correlation deriving unit 48 detects the correlation based on the output voltages V1 to V3 detected by the probe set 20 and the magnetic flux detecting unit 30 and selected by the frequency selecting unit 41 and the surface state acquired by the surface state acquiring unit 47. The relationship is derived and recorded in the correlation storage unit 43.

  At this time, the correlation deriving unit 48 acquires, for example, a plurality of data points by sequentially changing the distances d1 to d3 for the steel material S having the same conductivity σ and permeability μ, and approximates from the data points. A correlation (function) may be derived by obtaining a curve. When the lookup table is used as described above, the correlation deriving unit 48 measures the output voltages V1 to V3 obtained by substituting the distances d1 to d3 into the derived correlation (function). The process of associating the distance d1 (the distances d1 to d3 and other surface states in some cases) that is the state may be performed by changing the distances d1 to d3 and the like, thereby creating the lookup table.

(3-2. Operation of surface state measuring device)
The configuration and the like of the surface state measurement apparatus 10 according to the first embodiment of the present invention have been described above.
Next, the operation and the like of the surface state measuring apparatus 10 according to the present embodiment will be described with reference to FIGS. In the following, the operation in the surface state derivation process will be described first with reference to FIG. 10, and then the operation in the correlation derivation process will be described with reference to FIG.

(Surface state derivation process)
FIG. 10 is an explanatory diagram for explaining the operation in the surface state deriving process by the surface state measuring apparatus according to the present embodiment.

  In the surface state derivation process, step S101 is first processed as shown in FIG. 10, and in this step S101 (an example of an excitation step), one excitation coil 21I, 22I, 23I of the probe set 20 is performed by the excitation unit 11. Is selected and excited. Then, the process proceeds to step S103.

  In step S103 (an example of a magnetic flux detection step), the magnetic flux detection unit 30 detects the magnetic flux Φ generated by the excited excitation coil in synchronization with the excitation unit 11, and in the subsequent step S105, the magnetic flux detection unit 30 Then, electric signals (output voltages VA and VB) for each frequency are derived. That is, the voltage acquisition unit 31 selects a detection coil for the excited excitation coil, and acquires the voltages VOu and VOd from the selected detection coil. The differential amplifying unit 32 generates an output voltage V that is a difference signal between the voltages VOu and VOd, and the frequency separating unit 33 frequency-separates the output voltage V. Furthermore, if the electric signal output units 341 and 342 detect the maximum value for the frequency-separated output voltage V, and the phase of the output voltage V is advanced by 90 ° with respect to the excitation signal, the maximum value is detected. (It may be a case where the phase difference is 0 ° or more and less than 180 °.) If it is a positive value and is delayed by 90 ° with respect to the excitation signal (may be a case where the phase difference is -180 ° or more and less than 0 °). Are output as output voltages VA and VB (an example of an electric signal) for the respective frequencies f1 and f2. After the process of step S105, the process proceeds to step S107.

  In step S107, the surface state measuring apparatus 10 confirms whether or not the three excitation coils 21I to 23I are all excited and the detection signals V1 to V3 for the respective excitation coils 21I to 23I are acquired. If there is an excitation coil that is not excited, the processes in steps S101 to S105 are repeated. If all the excitation coils are excited, the process proceeds to step S109.

  In step S109, the frequency selection unit 41 of the surface state deriving unit 40 compares the output voltages VA and VB (for example, the output voltages VA and VB with respect to the output voltage V1), and selects the frequency f used for the surface state deriving. Then, the output voltages V1 to V3 corresponding to the selected frequency f are output to the correlation determining unit 42. Then, the process proceeds to step S111.

  In step S <b> 111, the correlation determination unit 42 determines one correlation used for surface state derivation based on the output voltages V <b> 1 to V <b> 3 and the correlation recorded in the correlation storage unit 43. Then, the process proceeds to step S113.

  In step S113 (an example of the surface state deriving step), the surface state specifying unit 44 determines the surface state (for example, distance d) based on the correlation determined in step S111 and at least one output voltage V1 to V3. Identify. In subsequent step S115, the surface state specifying unit 44 causes the surface state storage unit 45 to record the specified surface state. Then, the process proceeds to step S117.

  In step S117, the surface condition measuring apparatus 10 confirms whether or not the measurement is completed. If the measurement is not completed, the surface condition (for example, distance d) is determined by repeating the processes in and after step S101. The time change is recorded in the surface state storage unit 45. On the other hand, when the measurement is finished, the surface state measuring device 10 finishes the operation.

  Note that the change in the surface state recorded in the surface state storage unit 45 in steps S101 to S117 may be output to the display device, for example, by the surface state change output unit 46.

(Correlation derivation process)
FIG. 11 is an explanatory diagram for explaining the operation in the correlation derivation process by the surface state measuring apparatus according to the present embodiment.

  In the correlation derivation process, as shown in FIG. 11, first, step S201 is processed, and in this step S201, a steel material S whose surface state is known is prepared and arranged. And it progresses to step S203 and in step S203, the distance d with respect to the probe set 20 of the steel material S is set, and the surface state acquisition part 47 acquires the distance d with respect to each measurement. Then, the process proceeds to step S205.

  In step S205, measurement of an electrical signal (output voltages V1 to V3) by the excitation unit 11, the probe set 20, the magnetic flux detection unit 30, and the frequency selection unit 41 is performed. Specifically, in step S205, steps S101 to S109 of FIG. 10 are processed, and output voltages V1 to V3 for the selected frequency f are obtained. Then, the process proceeds to step S207.

  In step S207, the correlation deriving unit 48 checks whether or not the necessary number of data points has been detected. When the necessary data score is not obtained, the processing after step S203 is repeated, different distances d are set in step S203, and further data scores for the same steel material S are obtained. On the other hand, if the necessary number of data points has been obtained, the process proceeds to step S209. Here, the necessary number of data points means the number of data points that can be used to derive an approximate curve having the output voltage V as input and the surface state (for example, distance d) as output.

  In step S209, the surface state acquisition part 47 acquires the other surface state with respect to the steel material S by which the measurement was performed. In step S203, the surface state acquisition unit 47 acquires a distance d that is one of the surface states. Therefore, when it is desired to measure another surface state (conductivity σ, magnetic permeability μ), the surface state is acquired by the surface state acquisition unit 47 in step S209. After step S209, the process proceeds to step S211.

  In step S211, the correlation deriving unit 48 calculates an approximate function having the output signals V1 to V3 as inputs and the distance d as outputs based on a plurality of sets of the distance d and the output signals V1 to V3 at the distance d. To do. As this approximate function, for example, a function such as a quadratic, cubic, quartic function, exponential function, etc. can be used, but it is not limited to this example. After the process of step S211, the process proceeds to step S213.

  In step S213, the correlation deriving unit 48 creates a lookup table based on the approximate function calculated in step S211. That is, the correlation deriving unit 48 changes the distances d1 to d3 within a predetermined range (at least including a range that can be obtained by actual measurement), and substitutes each of the distances d1 to d3 for the approximate function. By doing so, a set of output voltages V1 to V3 and a corresponding distance d (for example, distance d1, which may include other surface states) are created to create a lookup table. In step S 215, the correlation deriving unit 48 records this lookup table in the correlation storage unit 43. When the approximate function is used directly without using the lookup table, this step S213 is omitted, and the approximate function is recorded in the correlation storage unit 43 as a correlation in step S215. However, by using the look-up table in this way, the measurement time can be shortened and quick measurement can be performed. After step S215, the process proceeds to step S217.

  In step S217, the surface state measuring apparatus 10 confirms whether all necessary correlations of the steel material S have been derived. If all necessary correlations have not been derived, the processes in and after step S201 are repeated. In this case, in step S201, it is desirable that steel materials S having different electrical conductivity σ, magnetic permeability μ, temperature, and the like are arranged and the correlation is measured for all the steel materials S. On the other hand, when all the correlations are derived, the correlation deriving operation ends, and the correlation derived here is used to process the surface state deriving process as shown in FIG. Become. In addition, when it is not possible to derive all the correlations, the derived correlations can be complemented. That is, it is difficult to derive the correlation for all the steel materials S having different electrical conductivity σ, magnetic permeability μ, temperature, and the like in step S217 and step S201. Therefore, a correlation is derived for each of the plurality of steel materials S having discretely different values such as conductivity σ, permeability μ, temperature, and the like, and from the correlation, conductivity σ, permeability μ that is not actually measured. It is also possible to interpolate the correlation with respect to the steel material S such as temperature.

(3-2. Examples of correlation)
Here, an example of a correlation derivation result derived in the correlation derivation process shown in FIG. 11 and used in the surface state derivation process shown in FIG. 10 will be described with reference to FIG. FIG. 12 is an explanatory diagram for explaining an example of a correlation derivation result used by the surface state measurement apparatus according to the present embodiment.

  As the probe set 20, a second example of the probe set shown in FIG. 8 is used. As the excitation coils 21I to 23I and the detection coils 21Od and 21Ou, an enameled copper wire with a material of copper and a diameter of 0.5 mm is used. The coil which wound 20 turns with the direct system 30mm of the coil end surface was used. In this case, the height of each coil was 10 mm, and the distances Δd1 and Δd2 between the probes 21 to 23 were about 10 mm. And as excitation frequency f1, f2, 10 kHz and 1 kHz were used. Further, a flat magnetic body (SS400) and a non-magnetic body (SUS304) are used as measurement objects, and the distance from the lower surface of each probe to the steel material S (d-10 mm) is changed from 10 mm to 60 mm, and the output voltage V Was measured by the surface condition measuring apparatus 10 described above. The measurement results are shown in FIG.

  As shown in FIG. 12, it can be seen that the correlation F11 is obtained at 1 kHz and the correlation F12 is obtained at 10 kHz for the steel (SS400) that is a magnetic material. On the other hand, it can be seen that the correlation F13 is obtained at 1 kHz and the correlation F14 is obtained at 10 kHz for the non-magnetic steel material (SUS304). The correlations F11 to F13 (approximate curve) obtained in this way or a look-up table obtained from the approximate curve is recorded in the correlation storage unit 43 and can be used in the surface state derivation process.

(3-3. Examples of effects according to this embodiment)
The surface state measuring apparatus 10 according to the first embodiment of the present invention has been described above.
According to this surface condition measuring apparatus 10, by using three air-core exciting coils 21I to 23I arranged on a straight line, the surface condition (for example, distance d, conductivity σ, magnetic permeability) of the moving steel material S is used. μ) can be measured over time. At this time, since the correlation with the surface state to be measured can be determined by the three output voltages V1 to V3 from the three exciting coils 21I to 23I, it is used even under conditions where other surface states vary. Is possible. Furthermore, this measurement is performed in a non-contact manner, has high measurement accuracy, and requires only a very short measurement time, so it is stable even under adverse conditions such as high temperatures and cooling water splashes. Thus, the surface condition can be measured accurately and quickly. Therefore, it can also be applied to continuous casting, and in this case, bulging can be measured directly under the mold 2. Therefore, it is possible to detect blistering (an example of a surface state) due to an abnormality of the solidified shell S2, and it is possible to realize a stable operation such as prevention of breakout of the steel material S (slab).

  In the sense of rapid measurement, in the example shown in FIG. 12, the time required for 1 measurement is about 0.03 seconds for each of the first probes 21 to 23, and the correlation is determined thereafter. Processing such as processing and surface state identification processing can be performed in about 0.01 seconds. Therefore, one measurement time is about 0.1 second or less, and the steel material S that moves in the positive direction of the v-axis at about 42 mm / second can achieve a resolution of about 4.2 mm. In the above-described embodiment, it is possible to quickly determine the correlation by performing measurement with the three exciting coils 21I to 23I. On the other hand, in the sense that the unknown variable is 3 and the measured value of 3 is used, for example, the inductance value is obtained by simply changing the frequency of 3 or more, and the surface state is obtained by regression analysis therefrom. However, in this case, since it is necessary to use a total of three or more frequencies, the configuration of the apparatus (configuration of the excitation unit 11) becomes large and the manufacturing cost increases, and it is necessary to perform regression analysis. , One measurement time is as long as several tens of seconds, and quick measurement is difficult. From this, it can be understood how quickly the surface state measuring apparatus 10 according to the present embodiment enables measurement.

  Moreover, this surface state measuring apparatus 10 arrange | positions the three exciting coils 21I-23I of air core on the same axis | shaft, and thereby the local surface state (distance d, electrical conductivity (sigma), magnetic permeability) of the steel material S to move. μ) can be measured. In addition, when the three exciting coils 21I-23I are not arrange | positioned coaxially, it is very difficult to measure the local surface state of such steel materials S, and also from this, it concerns on the said this embodiment. It can be understood how the surface condition measuring apparatus 10 can accurately measure the surface condition.

  At this time, the surface state measuring apparatus 10 succeeds in shortening the distances Δd1 and Δd2 between the excitation coils 21I to 23I by using a special probe set 20 as shown in FIG. As a result, measurement time can be shortened while improving measurement accuracy. Furthermore, in the sense of shortening the measurement time, the surface state measurement apparatus 10 according to the present embodiment can further shorten one measurement time by recording the correlation as a lookup table. Whether the lookup table is used or the function of the approximate curve is used, the specific values (distance d) are specified using the output voltages V1, V2, and V3 as input values. Can be obtained. Therefore, for example, the surface condition measuring apparatus 10 can accurately measure the steel material S whose physical property value greatly changes over the Curie point (about 770 ° C.).

  As mentioned above, although preferred embodiment of this invention was described in detail, referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this example. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

  For example, in the above embodiment, the case where the distance d (that is, the surface state) is measured as the surface state of the steel material S has been described. However, as described above, the surface state of the steel material S to be measured may be electrical conductivity σ, magnetic permeability μ, etc. in addition to the distance d, and these can be measured simultaneously. As described in the above embodiment, when the lookup table for specifying the surface state is generated from the approximate function calculated by experimental measurement, the lookup table is shown in FIG. 9 or FIG. It is derived from the correlations F9 to F14 that are such approximate curves. However, these correlations F9 to F14 are uniquely determined if the conductivity σ, permeability μ, etc. of the steel material S are determined. Therefore, as a look-up table, not only the distance d but also the conductivity σ, permeability μ, etc. of the steel S from which the output voltages V1 to V3 are obtained for each set of output voltages V1 to V3. By preparing an associated lookup table, it is possible to simultaneously measure a plurality of surface states of the steel material S. Note that, in the case of using an approximate curve as well as the case of the lookup table, similarly, by creating an approximate curve from which other surface states (conductivity σ, magnetic permeability μ, etc.) are derived, the material S Can be measured simultaneously.

  In this specification, the steps described in the flowcharts are executed in parallel or individually even if they are not necessarily processed in time series, as well as processes performed in time series in the described order. Including processing to be performed. Further, it goes without saying that the order can be appropriately changed even in the steps processed in time series.

DESCRIPTION OF SYMBOLS 1 Immersion nozzle 2 Mold 3 Roll 10 Surface state measuring device 11 Excitation part 20 Probe set 21 1st probe 22 2nd probe 23 3rd probe 20I, 21I, 22I, 23I Excitation coil 20Ou, 21Ou, 22Ou, 23Ou Detection coil 20Od, 21Od, 22Od, 23Od Detection coil 31 Voltage acquisition unit 32 Differential amplification unit 33 Frequency separation unit 341, 342 Electric signal output unit 40 Surface state derivation unit 41 Frequency selection unit 42 Correlation determination unit 43 Correlation storage unit 44 Surface state specification Part 45 Surface state storage part 46 Surface state change output part 47 Surface state acquisition part 48 Correlation derivation part S Steel material S1 Molten steel S2 Solidified shell d, d1, d2, d3 Distance Δd Bulging amount Δd1, Δd2 Distance F, F1, F2, F3, F4, F5, F6, F7, F8 F9, F10, F11, F12, F13, F14, FN Correlation f, f1, f2 Frequency μ, μ1, μ2, μ3, μ4 Permeability σ, σ1, σ2, σ3, σ4 Conductivity V, VA, VB , V1, V2, V3 output voltage

Claims (7)

A surface condition measuring device for measuring the surface condition of a moving steel material,
Three probes including one excitation coil and one or two detection coils, which are arranged on the same axis so that each coil end face faces the steel material surface and have the same coil characteristics and an air core, A probe set in which the three coil probes are arranged side by side so that the coil characteristics of the excitation coils are equal, the excitation coils are positioned on the same axis and the distances from the steel surface are different;
An excitation unit that sequentially applies an AC voltage to each of the three excitation coils included in the probe set within one measurement time to excite the three excitation coils one by one;
A magnetic flux detection unit that detects a magnetic flux generated by the excitation coil excited by the excitation unit by a detection coil of the probe including the excitation coil and converts the magnetic flux into an electrical signal;
A surface state deriving unit for deriving a surface state of the steel material at a position facing the coil end surface within the one measurement time based on the electrical signal converted by the magnetic flux detection unit for each of the three exciting coils; ,
A surface state measuring apparatus comprising: An excitation coil included in at least one of the probes is shared as the detection coil with another probe adjacent to the probe,
The magnetic flux detection unit uses the excitation coil of the at least one probe as a detection coil of the other probe when the excitation coil of the other probe is excited by the excitation unit. The surface state measuring apparatus according to claim 1, wherein a magnetic flux with respect to an excitation coil of the probe is detected. The probe set includes the three excitation coils arranged adjacent to each other on the same axis, and the three probe coils at positions closer to the steel material surface than the three excitation coils and at positions farther from the steel material surface. Two exciting coils and two said detecting coils arranged coaxially,
When the excitation coil of the other probe is excited by the excitation unit, the magnetic flux detection unit is adjacent to the other excitation coil, the other two excitation coils, or the other one excitation coil and The electric signal of 2 which is a detection result of the magnetic flux of the exciting coil is acquired from the detection coil of 1, and is converted into an electric signal of a difference between the electric signals of the two. Surface condition measuring device. The excitation unit applies the alternating current of at least two frequencies to the excitation coil within the one measurement time,
The magnetic flux detector detects the magnetic flux for each of the two frequencies and converts it into an electrical signal,
The surface state according to any one of claims 1 to 3, wherein the surface state deriving unit derives the surface state based on an electric signal for the frequency having the largest absolute value of the electric signal. measuring device.   The surface state measuring apparatus according to any one of claims 1 to 4, wherein the surface state derived by the surface state deriving unit is a shape, magnetic permeability, or conductivity of the surface of the steel material.   The surface state deriving unit derives the surface state based on the relationship between the electrical signal measured in advance for each steel material and the surface state together with the electrical signal for each of the three excitation coils. The surface state measuring apparatus according to any one of claims 1 to 5. A surface condition measuring method for measuring the surface condition of a moving steel material,
Three probes including one excitation coil and one or two detection coils, which are arranged on the same axis so that each coil end face faces the steel material surface and have the same coil characteristics and an air core, In the probe set in which the three probes are arranged side by side so that the coil characteristics of the excitation coils are equal, the excitation coils are positioned on the same axis and the distance from the steel surface is different, An excitation step of sequentially applying an alternating voltage within one measurement time to excite the three excitation coils included in the probe set one by one;
A magnetic flux detection step in which the magnetic flux detection unit detects the magnetic flux generated by the excitation coil excited in the excitation step by the detection coil of the probe including the excitation coil, and converts it into an electrical signal;
The surface state deriving unit derives the surface state of the steel material at a position facing the coil end face within the one measurement time based on the electrical signal converted in the magnetic flux detection step for each of the three excitation coils. A surface state deriving step to perform,
A surface state measuring method characterized by comprising:

Images