KR20060063430A - An on-line determination device of transformation ratio of steel plate using ac magnetic field - Google Patents

Abstract

The present invention relates to an apparatus for measuring the transformation amount of steel passing through the accelerated cooling stand online in the accelerated cooling stand after rolling.

The present invention provides a device for measuring the transformation amount of the steel online while cooling the high temperature steel during transport, the yoke member provided at both ends spaced apart from the steel while facing the steel; An excitation coil wound at one or both ends of the yoke member to induce an alternating magnetic field in the yoke member according to the application of an AC power source; First and second metal members each forming a magnetic circuit between both ends of the yoke member and the steel; A magnetic flux detecting coil detecting an intensity of magnetic flux on a magnetic circuit formed of the yoke member, the first metal member, the steel and the second metal member by the alternating magnetic field induced by the excitation coil; And an analysis unit configured to measure a transformation amount of the steel according to the magnetic flux intensity detected by the magnetic flux detection coil by using a correlation between a preset magnetic flux intensity and a transformation amount of the steel.

According to the present invention, when measuring the amount of transformation of the steel in progress in the steel acceleration cooling stand, it is possible to secure a sufficient lift-off, online measurement is possible, and is not significantly affected by the harsh environment of high temperature, high humidity inside the acceleration cooling stand. There is no advantage.

Rolling, accelerated cooling stand, steel, transformation, magnetic material, magnetic flux, yoke

Description

Steel on-line measuring device using alternating magnetic field {AN ON-LINE DETERMINATION DEVICE OF TRANSFORMATION RATIO OF STEEL PLATE USING AC MAGNETIC FIELD}

1 is a schematic structural diagram of an interior of an accelerated cooling stand to which the present invention is applied.

2 is a magnetic characteristic change according to the phase transformation of the steel in the cooling process of the accelerated cooling stand according to the present invention.

3 is a schematic configuration diagram of a steel deformation amount online measuring device using an alternating magnetic field according to an embodiment of the present invention.

 Explanation of symbols on the main parts of the drawings

10: accelerated cooling stand 20: steel

111 housing 112 yoke member

113: magnetic flux detection coil 114: female coil

115,116: first and second metal member 117: power supply device

118: flux 119: analysis unit

211: inlet pipe 212: discharge pipe

213: cooling material

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for on-line measurement of transformation amount of steel, and more particularly, to an apparatus for on-line measurement of transformation amount of steel passing inside a high temperature accelerated cooling stand.

In the steelmaking process, in order to produce high strength steel, the steel is passed through the accelerated cooling zone after hot rolling to strengthen the transformation structure. In the case of accelerated cooling of such steels, grain refinement of the tissue occurs, thereby improving tensile strength, increasing toughness, and enabling high input heat welding, thereby significantly reducing welding work. In the case of the transformation structure transformation technology, an apparatus for measuring the transformation behavior of the steel in the acceleration cooling zone in real time is essential.

In general, the high-temperature steel that enters the entrance of the accelerated cooling stand after rolling is cooled while being transferred through the inside of the accelerated cooling stand at a constant speed, and discharged into the low-temperature steel at the exit side of the accelerated cooling stand. Such steels are transformed from paramagnetic austenite to ferromagnetic ferrite by the cooling process in the accelerated cooling zone.

In order to achieve the desired ferromagnetic ferrite state at the side of the accelerated cooling stand, it is important to control the cooling process, especially the amount of cooling water. This is because over-transformation occurs when the amount of cooling water in the accelerated cooling stage is large, and untransformation occurs when the amount of cooling water is small. Therefore, the on-line measurement of the steel sheet during accelerated cooling after rolling is to control the amount of cooling water according to the amount of transformation of the steel, which is important for securing the steel in a desired state at the exit of the accelerated cooling stand. In order to prevent plate deformation, it is essential to perform cooling control by measuring actual transformation rate in the accelerated cooling stand.

However, the acceleration cooling stand is a kind of black box, and it is difficult to easily measure the transformation rate of the steel therein. In fact, it is very difficult to measure the temperature and the transformation due to the extreme environment in the current acceleration cooling stand.

Conventional transformation measurement techniques include a temperature measurement method for measuring a temperature rise due to latent heat during phase transformation with a precision thermometer, a method using X-ray diffraction, a method using eddy current, and the like.

The temperature measurement method has a drawback that the information that can be obtained as an indirect method, rather than directly detecting phase transformation, is rough. In addition, there is a disadvantage in that responsiveness is difficult to secure precision and measurement using a radiation thermometer in a water-cooled environment is difficult.

The X-ray diffraction method can confirm only transformation information within 50 µm from the surface layer portion of the steel sheet. Therefore, the transformation properties of steel materials are inadequate in view of the fact that information needs to be taken out at a depth of 200 µm or more. In addition, in consideration of the poor cooling atmosphere of the mixed water and air in the accelerated cooling, it is fundamentally impossible to use, and there is a disadvantage that the apparatus used is an expensive large apparatus and difficult to maintain and repair. In addition, since strong X-rays are irradiated, a radiation protection and shielding device is necessary.

Eddy current measurement is precise in the laboratory environment, but is very sensitive to the lift-off, the distance between the steel under test and the eddy current sensor, so there is a limit to obtaining a reliable signal in the field environment where various vibrations exist. have.

In addition, Republic of Korea Utility Model Application No. 1995-346, which is excited by different frequency bands and detects the magnetic flux shaped to output the organic electromotive force signal, by analyzing the signal filtered the organic electromotive force signal with a different frequency band filter Disclosed is a technique for measuring the amount of transformation, Korean Patent Application No. 1996-41353 discloses a technique for determining the fraction of each phase by using the x-ray paradigm analysis method, which is a method of analyzing the crystal structure, to obtain the rate of transformation, Korean patent Application No. 1996-51639 discloses a technique for obtaining permeability using a lift-off distance value and calculating the amount of transformation by the permeability. Korean Patent Application No. 1996-67984 discloses a maximum value of a measured voltage signal such as a unit time. The technique of measuring the metamorphosis rate by finding the bay is disclosed. In addition, Japanese Patent Laid-Open No. 5-126798 discloses an apparatus for forcibly magnetizing a steel plate and measuring the amount of transformation by measuring the magnetic change of the magnetized steel sheet. However, these techniques differ from the present invention in the principles, concepts and arrangements for measuring metamorphism.

Therefore, in the technical field, the necessity of a device for accurately measuring the amount of transformation of the steel passing through the interior of the accelerated cooling stand in order to accurately control the amount of cooling water in the accelerated cooling stand as a part for improving the quality of the steel. to be.

The present invention has been proposed to solve the above problems, the steel transformation can be measured online by analyzing the magnetic flux change according to the transformation amount of the steel passing through the accelerated cooling zone after rolling online steel transformation The purpose is to provide an on-line measuring device.

In addition, another object of the present invention is to provide an apparatus for measuring the amount of transformation online of a steel having excellent applicability and simple structure to an environment of high temperature and poor accelerated cooling stage.

The present invention for achieving the above object, in the apparatus for measuring the transformation amount of the steel online while cooling the high temperature steel during transport,

A yoke member having both ends spaced apart from the steel while facing the steel; An excitation coil wound at one or both ends of the yoke member to induce an alternating magnetic field in the yoke member according to the application of an AC power source; First and second metal members each forming a magnetic circuit between both ends of the yoke member and the steel; A magnetic flux detecting coil detecting an intensity of magnetic flux on a magnetic circuit formed of the yoke member, the first metal member, the steel and the second metal member by the alternating magnetic field induced by the excitation coil; And an analysis unit configured to measure a transformation amount of the steel according to the magnetic flux intensity detected by the magnetic flux detection coil by using a correlation between a preset magnetic flux intensity and a transformation amount of the steel.

In one embodiment of the present invention, the measuring device according to the present invention may further include a housing of a nonmagnetic material having an internal space filled with a cooling material, wherein the yoke member, The first and second magnetic bodies and the magnetic flux detection sensor are installed, and the cooling material is one material selected from cooling oil, cooling water or cooling gas.

In addition, in one embodiment of the present invention, the yoke member includes a substantially U-shaped ferrite, and the first and second metal members are preferably ferromagnetic wire brushes or circular rollers. Do.

Further, in one embodiment of the present invention, the first and second metal members are attached to the outside of the housing corresponding to both ends of the yoke member, respectively, between both ends of the yoke member and the first and second metal members. It may further comprise a ferromagnetic member each bonded to the housing for forming a magnetic circuit.

Furthermore, in one embodiment of the present invention, while the steel is transferred at a constant speed, it is preferable to cool to a temperature of 500 ℃ to 600 ℃ at a temperature of 750 ℃ to 850 ℃, wherein the steel is 0.5 ~ 2.0 m It is preferable to feed at a speed of / s.

The present invention provides an apparatus for measuring on-line the amount of transformation of the steel passing through the acceleration cooling stand. The steel that passes through the accelerated cooling zone in the high temperature state is transformed from the paramagnetic austenite state to the ferromagnetic ferrite state through the cooling process. As such, the magnetic change of the steel is generated through the acceleration cooling zone, and the intensity of the magnetic flux applied to the steel also changes according to the magnetic change of the steel. The present invention provides an apparatus for measuring the magnetic transformation amount of steel passing through the accelerated cooling zone online by detecting and analyzing the change of magnetic flux intensity of the steel through the magnetic flux detection coil.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 is a schematic structural diagram of an interior of an accelerated cooling stand to which the steel deformation amount online measuring apparatus of the present invention is applied. Referring to FIG. 1, first, the rolled steel 20 is introduced into the acceleration cooling stand 10 by the driving of the roller 11. As such, when the steel 20 is introduced into the acceleration cooling stand 10, the amount of the coolant 14 set by the cooling water nozzles 12 installed in the upper and lower parts of the acceleration cooling stand 10 is detected. Sprayed on the upper and lower surfaces of the steel 20 to cool the steel (20). In order to obtain a preferred transformation state of the steel according to the present invention, the temperature of the steel entering the accelerated cooling zone after rolling is preferably 750 ℃ to 850 ℃, the temperature of the steel discharged from the accelerated cooling zone is preferably 500 ℃. To 600 ° C., and the moving speed of the steel passing through the accelerated cooling zone is preferably 0.5 to 2.0 m / s.

Although not shown in the drawing, in the cooling device of the accelerated cooling table 10, high pressure compressed air is supplied through the air compressor and water is simultaneously supplied. The supplied compressed air and water meet each other at one point of the cooling water nozzle 12, and water is sprayed according to the outflow speed of the high pressure, thereby generating mists in which fine water particles are scattered by the high pressure compressed air. The mist generated as described above is sprayed at high speed on the surface of the steel 20 due to its ejection speed, thereby cooling the heat-treated steel 20 at high speed.

Through such a cooling process, since sufficient cooling is achieved in a short time, the structure of the heat-treated steel 20 is refined, and thus the tensile strength is sharply improved.

2 is a magnetic characteristic change according to the phase transformation of the steel in the cooling process of the accelerated cooling stand according to the present invention. As described above, the steel 20 is rolled in the austenite state and then transferred to the accelerated cooling stand 10, cooled while passing through the accelerated cooling stand 10, and discharged in a ferrite state. Referring to FIG. 2, immediately after hot rolling, the temperature of the steel 20 is about 750 to 800 ° C. ((a) position), in this case, the austenite state (γ phase) of the face-centered cube and the magnetic permeability μ is 1. When the steel 20 enters the accelerated cooling zone 10 and starts quenching, when the temperature of the steel 20 gradually decreases and falls below the temperature of the A3 transformation line, the γ phase in the austenite state decreases gradually and the α phase in the ferrite state decreases. It will increase gradually. In this case, the ferrite phase is paramagnetic (α phase) since the Curie temperature is higher than or equal to 1. That is, when the temperature is below the A3 transformation line, it gradually changes from the austenite state to the ferrite state. When the temperature is above the Curie temperature, all phases are paramagnetic, but when the temperature is below the Curie temperature, the ferrite phase becomes ferromagnetic. As the quenching of the steel 20 proceeds, if the temperature of the steel 20 drops below the curie, the ferrite phase transformed from the austenite state into the ferrite state has ferromagnetic properties and the magnetic permeability μ is greater than 1. It becomes around 70. The present invention intends to measure the amount of transformation of the steel using the principle that the magnetic property of the steel greatly changes (ie, the magnetic permeability μ ranges from 1 to 70) during the transformation process.

As the cooling process proceeds, the amount of transformation increases, which is a change from paramagnetic austenite to ferromagnetic ferrite. In addition, the lattice structure is changed from a face-centered cube to a body-centered cubic structure, whereby a change in metal phase occurs. Here, the transformation amount may be calculated using Equation 1 below.

[Equation 1]

Transformation rate (%) = {(α phase volume) / (total volume of metal)} × 100

3 is an overall schematic configuration diagram of a steel deformation amount online measuring device using an alternating magnetic field according to an embodiment of the present invention. Referring to FIG. 3, the steel deformation amount online measuring apparatus 100 using the alternating magnetic field according to an exemplary embodiment of the present invention includes a housing 111 of a nonmagnetic material having an internal space including a cooling material 112. It is provided in the inner space of the housing 111 of the non-magnetic material, the both ends facing the steel 20, the alternating current by the yoke member 112, the power supply device 117 installed to be spaced apart from the steel 20 Excitation coil 114 wound on one or both ends of the yoke member 112 and both ends of the yoke member 112 and the steel material 20 in order to induce an alternating magnetic field to the yoke member 112 according to the application of power. ), The yoke member 112, the first metal member 115, and the steel material by the first and second metal members 115 and 116 to form a magnetic circuit therebetween, and the alternating magnetic field induced by the excitation coil 114. 20) and a magnetic flux detector for detecting a change in flux 118 on the magnetic circuit formed of the second metal member 116. The 113 and the analysis unit 119 for analyzing the change in the flux (118) detected by the magnetic flux detection coil 113 to measure the transformation amount of the steel 20 is configured to include.

In one embodiment of the present invention, the steel deformation amount measuring apparatus 100 of the present invention preferably measures the transformation amount of the steel 20 in close proximity to the high temperature steel 20 after hot rolling. A device for cooling of 100 may be needed. To this end, as shown in FIG. 3, in one embodiment of the present invention, an inlet pipe 211 and an inlet tube 211 for introducing the cooling material 213 from the outside are externally provided on one surface of the housing 111. It may include a discharge pipe 212 for discharging to. Therefore, the cooling material 213 introduced from the outside through the inlet pipe 211 cools the yoke member 112, the magnetic flux detection coil 113, and the excitation coil 114, and then through the discharge pipe 212. It is discharged to the outside. Here, the cooling material 213 may be cooling water, cooling gas or cooling oil.

In addition, although not shown in the drawing, in another embodiment of the present invention, a non-magnetic housing 111 containing the cooling material 213 is sealed, and a tube having a predetermined diameter inside the housing 111 (not shown). Inserts and cools the cooling material 213 inside the housing 111 by flowing a specific cooling medium (cooling water, cooling oil, etc.) into the tube, and as a result, the cooled cooling material 213. It is also possible to cool the measuring device 100 of the present invention. In this case, the cooling tube (not shown) may have any form or location at any position as long as it can cool the cooling material 213. However, the tube (not shown) is preferably located around the yoke member 112 in which the temperature-sensitive magnetic flux detecting coil 113 is located. As such, when the on-line measuring apparatus 100 of the steel according to the present invention operates in a high temperature environment, the cooling apparatus according to the above embodiments may be provided.

Meanwhile, as shown in FIG. 3, first and second metal members 115 and 116 are provided at both ends of the yoke member 112, respectively. Accordingly, the first and second metal members 115 and 116 are installed between both ends of the yoke member 112 and the steel 20 so that magnetic flux is formed between both ends of the yoke member 112 and the steel 20. Make the path effective. In this case, the first and the second metal members 115 and 116 may include a cooling material 213 injected for effective cooling of the yoke member 112, the magnetic flux detecting coil 113, and the excitation coil 114. It is installed in an effective way to prevent the leakage to the outside and maintain the flux path. To this end, in another embodiment of the present invention, the first and second metal members 115 and 116 may be detachably attached to the outside of the housing 111, and the first and second metal members 115 and 116 and the yoke member 112 may be detached. A ferromagnetic iron plate (not shown) may be welded and inserted into the housing 111 between the nth to allow the cooling material 213 to be effectively circulated without loss of magnetic flux. As a result, a magnetic close circuit is effectively formed through the steel 20, the first metal member 115, the yoke member 112, and the second metal member 116, and a magnetic flux 118 is generated on the magnetic closed circuit. Here, the first and second metal members 115 and 116 may be a means capable of effectively forming a magnetic flux path between both ends of the yoke member 112 and the steel 20, but in one preferred embodiment of the present invention, It is preferred that a brush or roller (not shown) having a circular cross section is assembled with a plurality of wires. The first or second wire brush or the first and second rollers may use a ferromagnetic-based steel wire and have rigidity and elasticity that can support the load of the yoke member 112. . In addition, the first and second wire brushes or rollers are respectively attached to the outside of the housing 111 corresponding to both ends or the both ends of the yoke member 112, and are in contact with the steel 20, and are moved It is preferable that the steel 20 be manufactured so as to absorb the bent portion due to the deformation of the plate.

In addition, the excitation coil 114 is wound on one end or both ends of the yoke member 112. AC power is applied to the excitation coil 114 by an external power supply 117. When the AC power is applied to the excitation coil 114 as described above, a magnetic field is formed in the coil according to Fleming's right hand law. The magnetic field is formed through the yoke member 112 on which the excitation coil 114 is wound. The direction of the magnetic flux 118 is determined according to the winding direction of the excitation coil 114. At this time, since the power applied to the excitation coil 114 is an AC power source, the magnetic field induced by the yoke member 112 becomes an AC magnetic field. As such, the intensity of the magnetic flux 118 formed by the alternating magnetic field induced by the excitation coil 114 is changed over time. The intensity of the magnetic flux is detected by the magnetic flux detecting coil 113. That is, a voltage is induced in the magnetic flux detecting coil 113 according to a change in magnetic flux intensity on the magnetic circuit formed through the yoke member 112, and the induced voltage is input to the analyzing unit 119. The induced voltage is determined by the following equation.

[Equation 2]

V =-dφ / dt                     

Where V is the voltage induced in the magnetic flux detecting coil,? Is the magnetic flux intensity, and t is the time.

As such, when the magnetic flux 118 due to the alternating magnetic field formed through the yoke member 112 changes, a constant voltage is induced in the magnetic flux detecting coil 113. Instead of measuring voltage, you can use a flux meter, such as a flux meter, as needed. The magnetic flux value of the induced voltage or flux meter increases as the intensity of the magnetic flux increases.

Furthermore, as shown in FIG. 3, the yoke member 112 is preferably a ferrite having a substantially U shape in order to form a magnetic flux path well. However, although the yoke member 112 of the U shape is shown in FIG. 3 as a preferable embodiment, it is sufficient if it is a structure and a state in which a magnetic flux path is formed.

Hereinafter, with reference to Figure 3, it will be described in more detail the steel deformation amount online measuring device using the alternating magnetic field according to the present invention. As described above, the high temperature steel 20 entered into the accelerated cooling zone 10 after rolling is changed from paramagnetic austenite state (γ phase) to ferromagnetic ferrite state (α phase) as quenching proceeds. At this time, in a preferred embodiment of the present invention, in order to cool the high temperature steel during transportation and measure the amount of transformation of the steel, the temperature of the steel entering the accelerated cooling zone 10 is 750 ° C to 850 ° C, The temperature of the steel discharged from the accelerated cooling stand 10 is preferably to be 500 ℃ to 600 ℃, for this purpose, the moving speed of the steel passing through the acceleration cooling stand is to be 0.5 ~ 2.0 m / s. desirable.                     

On the other hand, when the AC power is applied to the excitation coil 114 wound on the yoke member 112 in the power supply device 117, the AC magnetic field is induced through the yoke member 112. At this time, as the steel 20 gradually changes from paramagnetic to ferromagnetic, the steel 20, the first metal member 115, and the yoke member 112 are caused by an alternating magnetic field induced by the excitation coil 114. And a magnetic circuit is formed through the second metal member 116 and the magnetic flux 118 is generated on the magnetic circuit. The magnetic flux 118 is gradually increased in strength as the steel 20 is transformed from a paramagnetic austenite state to a ferromagnetic ferrite state. At this time, the magnetic flux detection coil 113 detects the strength of the magnetic flux 118 on the magnetic circuit. That is, when the magnetic flux changes with time, a constant voltage is induced in the magnetic flux detecting coil 113, and the voltage induced in the magnetic flux detecting coil 113 also varies according to the strength of the magnetic flux. Therefore, the strength of the magnetic flux may be determined as the magnitude of the voltage induced by the magnetic flux detecting coil 113. Subsequently, the induced voltage is transmitted to the analyzer 119. The analysis unit 119 calculates the transformation amount of the steel 20 using the correlation between the intensity of the magnetic flux and the transformation amount.

As a result, as the transformation of the steel 20 proceeds, the strength of the magnetic flux 118 formed through the first metal member 115, the steel 112, the second metal member 116, and the yoke member 112. Is increased, and as the intensity of the magnetic flux 118 increases, the intensity of the voltage induced by the magnetic flux detecting coil 118 also increases. The analysis unit 119 detects the transformation amount of the steel 20 by analyzing a correlation between the voltage signal and the transformation amount according to the detected magnetic flux magnitude. Here, the analysis unit 119 may be implemented as a microprocessor or software, and those skilled in the art may implement the program by using a predetermined program. In addition, the analyzer 119 may be capable of receiving the voltage signal from the flux detecting coil 113 wirelessly as well as through a wire. In addition, it is possible to directly use the change value of the magnetic flux by configuring a flux integration circuit such as a flux meter as well as the voltage. The apparatus for measuring the amount of transformation of steel online according to the present invention may be installed in a plurality of places in the accelerated cooling stand 10 to measure the amount of transformation of steel online at each position.

As described above, in the steel transformation amount measuring apparatus using the alternating magnetic field according to the present invention, the transformation amount of the steel 20 can be measured by detecting and analyzing the magnetic flux according to the transformation amount of the steel 20.

The description and the contents of the drawings described above describe the technical idea of the on-line deformation measuring apparatus for steel according to the present invention, which is illustrative of the best embodiments of the present invention and is not intended to limit the present invention. In addition, it is obvious that any person having ordinary skill in the art may make various modifications and imitations without departing from the scope of the technical idea of the present invention.

Therefore, the scope of the present invention should be determined by the appended claims rather than by the foregoing description or drawings.

According to the present invention, when measuring the amount of transformation of the steel in progress in the steel accelerated cooling stand, it is possible to secure a sufficient lift-off can be measured online.

In addition, there is an advantage that can accurately measure the amount of transformation without being significantly affected by the harsh environment of high temperature, high humidity inside the acceleration cooling stand.

Claims (12)

In the device for measuring the transformation amount of the steel online while cooling the high temperature steel during transport, A yoke member having both ends spaced apart from the steel while facing the steel; An excitation coil wound at one or both ends of the yoke member to induce an alternating magnetic field in the yoke member according to the application of an AC power source; First and second metal members each forming a magnetic circuit between both ends of the yoke member and the steel; A magnetic flux detecting coil detecting an intensity of magnetic flux on a magnetic circuit formed of the yoke member, the first metal member, the steel and the second metal member by the alternating magnetic field induced by the excitation coil; And An analysis unit measuring a transformation amount of the steel according to the magnetic flux intensity detected by the magnetic flux detection coil by using a correlation between a preset magnetic flux intensity and a transformation amount of steel; Online transformation device for measuring the amount of steel comprising a. The method of claim 1, Further comprising a housing having an interior space filled with a cooling material, Steel deformation amount online measuring device, characterized in that the yoke member, the first and second magnetic bodies and the magnetic flux detection sensor is installed in the inner space of the housing. The method of claim 2, wherein the cooling material, An on-line measuring device for transformation amounts of steel, characterized in that the material is one selected from cooling oil, cooling water or cooling gas. The method of claim 2, wherein the housing, Steel transformation amount on-line measuring device, characterized in that it comprises an inlet pipe and the discharge pipe discharged from the outside of the cooling material. The method of claim 1, wherein the yoke member, Steel transformation amount online measuring device comprising a substantially U-shaped ferrite. The method of claim 1, wherein the first and second metal members, An apparatus for measuring the amount of transformation of steel, characterized in that attached to the outside of the housing corresponding to both ends of the yoke member, respectively. The method of claim 6, And an additional ferromagnetic member joined to the housing to form a magnetic circuit between both ends of the yoke member and the first and second metal members, respectively. The apparatus of claim 1, wherein the housing is made of a nonmagnetic material. The method of claim 1, wherein the first and second metal members, A device for measuring the amount of transformation of steel, characterized in that it is a ferromagnetic wire brush. The method of claim 1, wherein the first and second metal members, An on-line measuring device for the amount of transformation of steel, characterized by being a ferromagnetic circular roller. The method of claim 1, wherein the steel material, Steel transformation amount online measuring device, characterized in that cooled to a temperature of 500 ℃ to 600 ℃ at a temperature of 750 ℃ to 850 ℃ while being transferred at a constant speed. The method of claim 11, The steel sheet is online deformation measuring device characterized in that the conveyed at a speed of 0.5 ~ 2.0 m / s.

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