KR100345738B1 - An apparatus for measuring thickness of scale on the surface of a plate - Google Patents

Abstract

PURPOSE: A measuring apparatus of the thickness of a scale is provided to exactly and simply measure the thickness of the scale on the surface of a thick plate by using the difference of mutual magnetic properties between the thick plate and the scale layer. CONSTITUTION: A thick plate(1) has a scale(3). A housing(10) contains a magnetic core(9) therein. A magnetic induction coil(5) generates magnetic flux by wiring in the housing and feeding voltage. A sensor(15) contains a first detecting coil and a second detecting coil(7) to feed and output induction voltage by the magnetic flux of the magnetic induction coil and the thick plate. The first and the second detecting coils are formed in the upper part and the lower part of the magnetic induction coil. The sensor outputs the induction voltage to be changed according to the thickness of the scale layer by contacting to the thick plate. Thereby, the accuracy of the measurement is improved by the simple method.

Description

An apparatus for measuring thickness of scale on the surface of a plate}

The present invention relates to a scale thickness measuring apparatus, and more particularly, to a scale thickness measuring apparatus of a thick plate surface capable of measuring the thickness of a scale by a non-destructive method by detecting an induced voltage that varies depending on the thickness of the scale.

In general, a thick oxide layer is generated on the surface of the thick plate produced during the rolling process during the heating and rolling process. This is called a scale, and the thickness of the scale depends on the manufacturing process, which is an important factor in degrading the quality of the final product. Therefore, removing the scale is a very important problem for improving the quality of the product. In general, the scale is removed by a scale break consisting of a vertical roll and a high pressure water jet. The thick plates from the heating or rolling process are rolled at a slight rolling rate in a vertical roll, the scale is crushed and then removed by high pressure water.

As described above, since the thick plate is pushed down by the vertical roll when the scale is removed, the scale is not completely removed when the thickness of the scale is not accurately measured, and the thick plate is affected by the rolling of excessive reduction ratio. There was a case. Therefore, accurate measurement of scale thickness plays a very important role in product improvement.

At present, a method of measuring the thickness of a scale is mainly a method of cutting a thick plate vertically and polishing and measuring a cross section by an optical microscope or an electron microscope. However, this method not only has to cut the thick plate for sample preparation, but also takes a long time for the measurement. In addition, there was a problem that the thickness variation was large depending on the measurement position of the scale.

In order to solve the above problem, the scale thickness of the surface of the thick plate to measure the thickness of the scale by the change of the magnetic field strength induced with respect to the magnetic field applied from the outside using the difference of the magnetic properties between the thick plate and the scale layer It is an object to provide a measuring device.

In order to achieve the above object, the scale thickness measuring apparatus of the thick plate surface according to the present invention is composed of a scale plate is formed and a sensor that is in contact with the thick plate and outputs an induced voltage that changes depending on the thickness of the scale layer.

The sensor includes a housing having a magnetic core inserted therein, a magnetic induction coil wound around the housing and applied with a voltage to generate magnetic flux, and a magnetic flux of the magnetic induction coil formed above and below the magnetic induction coil. And a first detection coil and a second detection coil to which an induced voltage by the thick plate is applied and output, so that the output voltages of the first detection coil and the second detection coil are differentially amplified in the differential amplifier.

The calibration curve, which is a criterion for determining the scale thickness of the actual thick plate, can be constructed by measuring the relationship between the scale thickness and the output voltage by measuring a plurality of samples in which scales having different thicknesses are formed.

1 is a view showing a line of magnetic force in accordance with the present invention.

Figure 2 shows a scale thickness measurement sensor according to the present invention.

3 is a view showing a scale thickness measuring apparatus according to the present invention.

4 is a graph showing a measurement result of scale thickness according to the present invention.

Explanation of symbols on the main parts of the drawings

1: thick plate 3: scale

5: magnetic induction coil 6,7: detection coil

9: core 10: housing

12: differential amplifier 15: sensor

The present invention utilizes Faraday's law and Ampere's law, which are basic physical laws. To measure the thickness.

Electromotive force induced in the induction coil 5 having an arbitrary number of turns as shown in FIG. 1 (a) is proportional to the rate of change of the flux. If this is expressed as an equation, it is expressed as Equation 1.

Where E represents the electric field, l represents the integration path, and Φ represents the magnetic flux.

At this time, the magnetic flux passing through the first detection coil 6 is the value obtained by dividing the magnetic field B passing through the area A, as shown in Equation (2).

As shown in FIG. 1A, when the first detection coil 6 and the second detection coil are disposed above and below the magnetic induction coil 5, the magnetic flux Φ ₁ and the second passing through the first detection coil 6 are formed. The value of the magnetic flux Φ ₂ passing through the two detection coils 7 is the same. This means that when the voltage of the induction coil 5 is applied, the electromotive force induced in the first detection coil 6 and the second detection coil 7 is the same.

As shown in FIG. 1 (b), when the thick plate 1 is disposed under the second detection coil 7, the magnetic field guided to the first detection coil 6 and the second detection coil 7 is provided. Is different by 4πM due to the magnetization (M) of the thick plate (1). That is, a difference in induced electromotive force between the first detection coil 6 and the second detection coil 7 is generated by a value corresponding to the above value.

The present invention uses the above-described concept, and forms a basic form of a sensor for measuring the thickness of a scale by using a magnetic induction coil and two detection coils, thereby detecting the difference in electromotive force due to the thickness of the scale and measuring the thickness. 2 is a view showing a measuring sensor applied to the present invention. As shown in the figure, the magnetic induction coil 5, the first detection coil 6 and the second detection coil 7 are wound in a groove (not shown) of the housing 10. The housing 10 is made of an insulating material, in the center of which a core 9 made of a soft magnetic material having a length of about 10 mm and a diameter of about 1 to 2 mm is inserted. The core 9 is for increasing the magnetic induction signal, and the lower part of the sensor is in contact with the scale layer 3 perpendicularly. At this time, it is preferable to increase the number of turns of the detection coils 6 and 7 as much as possible to increase the signal.

Hereinafter, a method for measuring scale thickness of a thick plate surface according to an embodiment of the present invention will be described in detail with reference to FIGS. 3 and 4.

3 is a view showing a scale thickness measuring apparatus according to the present invention. As shown in the drawing, the thick plate 1 on which the scale layer 3 is formed is provided with a magnetic induction coil 5 and a sensor 15 wound with first and second detection coils 6 and 7. Induction coil 5 is applied with an alternating voltage of frequency 100 Hz and voltage 15 V in an oscillator circuit not shown. A resistor R1 of 1 KΩ is inserted at the input side of the magnetic induction coil 5 to increase the output impedance of the input oscillation circuit, thereby enabling stable oscillation of voltage and frequency.

The first detection coil 6 and the second detection coil 7 have the same number of turns, and the output thereof is connected to the differential amplifier 12. In addition, 10KΩ resistors R ₂ and R ₃ and 6.8 nF capacitors C ₁ and C ₂ are inserted into the output sides of the first and second detection coils 6 and 7, respectively. (7) filter the signal output from the;

In the absence of the thick plate 1, since the magnetic fluxes Φ ₁ and Φ _{2 of} the first detection coil 6 and the second detection coil 7 are the same, the output value of the differential amplifier 12 becomes zero, but the thick plate ( When 1) is present, the magnetic flux (M) of the thick plate 1 causes a difference in magnetic flux, and the output value of the differential amplifier 12 does not become zero. As the scale layer 3 (actually the scaling layer is slightly magnetic) is formed in the thick plate 1, the difference in the magnetic flux between the first detection coil 6 and the second detection coil 7 decreases. As a result, the output value of the differential amplifier 12, that is, the output voltage also decreases.

Since the output voltage of the differential amplifier 12 depends on the thickness of the scale layer 3 as described above, in order to know the thickness of the scale layer 3 from the output voltage, the difference between the output voltage and the thickness of the scale layer 3 is determined. A reference calibration curve representing the relationship is needed. For this purpose, it is necessary to measure the output value of the standard sample which knows the thickness of the scale layer 3 in advance.

The scale layer thickness of the standard sample is measured by thoroughly cleaning the surface in a mixed atmosphere of oxygen and nitrogen in a 1: 1 atmosphere and then heating the thick plate to form a scale layer and observing with an electron microscope. A plurality of samples on which scale layers 3 of different thicknesses are formed are measured by measuring sensor 12, and output voltages corresponding to the respective thicknesses are obtained to construct a calibration curve as shown in FIG. In the drawing, when the thick plate 1 without the scale layer 3 is measured, the output voltage is about 5V, and as the thickness of the scale layer 3 becomes thick, the output voltage gradually decreases, and the thickness is about 100 μm. You can see that it outputs a voltage of 2.5V.

The thickness of the scale layer 3 of the actual thick plate 1 can be obtained by comparing the output voltage obtained by the above-described measuring apparatus with the calibration curve of FIG. 4.

As described above, the present invention not only simplifies the method but also improves the accuracy of the measurement because the thickness of the scale layer is measured by measuring the induction magnetic generated in the coil. In addition, the present invention is a non-destructive measuring method in which no thick plate needs to be cut to measure the thickness of the scale.

Claims (1)

A scaled plate; And Housing with magnetic core inserted inside, A magnetic induction coil wound around the housing and generating a magnetic flux by applying a voltage, A first detection coil and a second detection coil which are formed above and below the magnetic induction coil and are subjected to the magnetic flux of the magnetic induction coil and the induced voltage by the rear plate, and are in contact with the thick plate according to the thickness of the scale layer. Scale thickness measurement device on the surface of a thick plate consisting of a sensor that outputs a variable induced voltage.

Images