JPH03160361A - Transformation quantity measuring apparatus for steel material - Google Patents

Abstract

PURPOSE:To achieve easy and accurate measurement of a transformation value during and after a treatment by arranging any of a magnetic field generator and a magnetic flux detector to contain a coil for detecting excitation or a magnetic flux to arrange such a form of roll as to rotate in contact with a steel material to be measured. CONSTITUTION:A low frequency current is applied to an excitation coil 2b of an exciting roll 2 rotating in contact with an object 1 to be measured from an exciter 6 to generate a magnetic field. A component transmitted through the object 1 to be measured of magnetic fluxes generated from the coil 2b is detected by a detection coil 3b of a detection roll 3 rotating in contact with an opposite surface of the object 1 to be measured. A phase difference and an intensity of a magnetic flux taken into a phase difference detector 4 and a magnetic flux detector 5 are detected. Signals of the detectors 4 and 5 are inputted into a transformation value computing device 7 together with a thermometer 8 to calculate a transformation value. That is, a phase difference is determined primarily based on a frequency of the device 6 and a permeability and an average permeability of a steel material and the average permeability is determined based on a plate thickness and the transformation value, thereby enabling calculation of the transformation value depending on the phase difference, the average permeability, the plate thickness and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an apparatus for accurately measuring the amount of transformation of a running steel material on-line in a hot rolling line for steel materials or the like.

Conventional technology and its issues In recent years, “controlled rolling” has made it possible to produce high-strength steel sheets with excellent low-temperature toughness without the need for post-rolling heat treatment.
The so-called "two-phase region rolling" is known as one form of controlled rolling. This is achieved by rolling in a relatively low-temperature ``[γ+α] two-phase region'' where the transformation of ``austenite (γ) and ferrite (α)'' occurs, and by adjusting the ratio of γ and α at this time. This is a means of manufacturing steel materials that controls the mechanical strength of steel materials.

By the way, in the above-mentioned "two-phase region rolling", T during rolling is
Since the ratio of γ and α has a very significant effect on the mechanical strength of the steel after rolling, in order to obtain the desired strength steel, it is necessary to accurately detect the change from γ to α during rolling in the two-phase region. becomes important.

As a means of detecting the amount of transformation in steel materials, ``the α phase below the magnetic transformation point generally exhibits ferromagnetism, whereas the γ phase is non-magnetic, and the magnetic susceptibility of the steel material is determined according to the change in the ratio of the two. Various methods have been proposed in the past that take advantage of the phenomenon of "changes in the
Device for measuring the amount of transformation of steel sheets online (Unexamined Japanese Patent Publication No. 5
9-174749)''.

As shown in FIG. 3(a), this device holds a conditioning plate 1 immediately before hot rolling in a non-contact state, and a magnetic field generator 1 is placed on one side.
2, and a magnetic flux detector 13 on the other side. The intensity of the leaking magnetic flux is detected by the magnetic flux detector 13, and the amount of transformation of the steel plate 1 is detected based on this value.

However, the above-mentioned proposed transformation amount measuring device had the following problems.

That is, in general, during the rolling process of steel plates, it is unavoidable that the steel plate to be processed is bent, and also due to defects in the conveyance system, etc., the magnetic field. It is difficult to keep the position of the steel plate 1 constant with respect to the generator 12 and the magnetic flux detector 13. Therefore, the position of the steel plate 1 with respect to the magnetic field generator 12 and the magnetic flux detector 13 is not constant, and therefore the mutual positional relationship changes from the state shown in FIG. 3(a) to the state shown in FIG. A situation in which the distance from 12 becomes longer often occurs.However,
When such a relative change in the position of the steel plate occurs, the proportion of magnetic flux generated from the magnetic field generator 12 that passes through the gap between the steel plate 1 and the magnetic field generator 12 increases, and the ratio of the magnetic flux passing through the copper plate 1 increases. The strength of the leakage magnetic flux detected by the magnetic flux detector 13 also changes, and it is difficult to prevent detection errors from occurring even when a steel plate having the same amount of transformation is used as the material to be measured.

Therefore, the applicant focused on the phenomenon that when magnetic flux passes through a steel material, there is a phase delay depending on the amount of ferromagnetic α phase, and in order to accurately measure the amount of transformation of steel material online,
First, the above-mentioned "phase delay (difference between the phase before passing through the tM material and the phase after passing through the steel material)" is detected from the leakage magnetic flux from the steel material to which a magnetic field has been applied, and based on this, the amount of variation B is determined. (Japanese Unexamined Patent Publication No. 61-21094)
No. 2).

FIG. 4 is a schematic diagram of the main parts of the "device for measuring the amount of transformation of steel" proposed by the applicant, in which the magnetic flux detector 15 directly detects the magnetic flux from the magnetic field generator 12 and the magnetic flux that passes through the steel Fi1. A phase difference detector (not shown) detects the phase difference between the output signal and the magnetic flux detector l3 that detects leakage magnetic flux, and a transformation amount calculator (not shown) calculates the amount of transformation of the steel material based on the detected phase difference. It is calculated. It has been confirmed that this transformation amount measuring device can accurately detect the transformation amount without being affected by bending of the sea bream material during the rolling process or defects in the steel material conveyance system.

However, through numerous subsequent practical works, the present inventor came to realize that the ``1000-step method for measuring the amount of steel transformation proposed by the present applicant'' also had the following disadvantages. In other words, with the above means, "the occurrence of bending of the steel plate" and "
In order to prevent the steel plate from coming into contact with the magnetic flux detector and destroying the detector due to warping of the end face of the steel plate, etc., it is necessary to take a sufficient distance X as shown in Figure 4. It was necessary to make the ``magnetic field generated by the magnetic field generator 12'' stronger so that a clear output signal from the magnetic flux detector 13 could be ensured even if the ``magnetic field generated by the magnetic field generator 12'' became large. Moreover, although this is also common to the proposal related to JP-A No. 59-174749, the calculated value of the amount of transformation tends to be influenced by the "magnetic characteristics of the atmosphere" in the magnetic flux measuring section, for example, On the rolling line, the magnetic properties of the atmosphere constantly change due to the scattering of scales and water droplets during rolling, and this causes a detection error in the detected magnetic flux value, causing an inconvenience in the calculation of the amount of transformation. was also recognized. Therefore, it is an object of the present invention to measure the amount of transformation of steel materials running on a processing line (such as steel plates during rolling, just before rolling, or just after rolling) without being affected by the atmosphere, and to The aim was to establish a means of detecting with high precision without requiring measures such as increasing the output.

Means for Solving the Problems> The present invention has been perfected based on the results of numerous experiments and studies conducted from various viewpoints in order to achieve the above objects, and its characteristics include: However, ``For example, the above-mentioned Japanese Patent Application Laid-Open No.
In the "apparatus for measuring the amount of transformation of a steel material based on the leakage magnetic flux from the steel material to which a magnetic field is applied" as proposed in No. 174749 and JP-A No. 61-210942, either a magnetic field generator or a magnetic flux detector is used. The invention also has the feature that it has a built-in excitation coil or detection coil and is in the form of a roll that rotates in contact with the steel material to be measured.

Hereinafter, the present invention will be explained in more detail based on examples.

FIG. 1 is a conceptual diagram showing an example of an apparatus for measuring the amount of transformation of steel according to the present invention. A detection roll 3 detects the magnetic flux (leakage magnetic flux), a phase difference detector 4 detects the phase difference from the output of the detection coil in the detection port 3, and a leakage magnetic flux is detected from the output of the detection coil in the detection port 3. A magnetic flux detector 5 that detects the intensity, an excitation device 6 that excites the excitation coil in the excitation roll 2, a thermometer, a magnetic flux detector, and a variable B amount calculator that calculates the amount of transformation based on the output of the phase difference detector. 7, and a thermometer 8 for detecting the temperature of the object to be measured (steel plate) 1
The main control device was

Here, the excitation roll 2, which is a magnetic field generator, and the detection hole 3, which is a magnetic flux detector, are arranged as shown in FIG.

That is, the symbols 2a and 3a in FIG. 2 are an excitation roll main body and a detection roll main body, respectively, which are made of a material with low magnetic permeability such as stainless steel. An excitation coil 2b is built-in, and the detection roll 3 has a detection coil 3b built-in in close contact with the inner wall of the detection port main body 3a. That is, the excitation coil 2b and the detection coil 3b are not wound around an iron core or the like as in the conventional case, but the outside is wound around the roll body 2a. 3a, and has a structure in which the roll bodies 2a and 3a are axially opposite to each other. For this reason, the magnetic field generator, which is the excitation roll, and the magnetic flux detector, which is the detection port, are connected to the object to be measured (
It is possible to perform contact-type leakage magnetic flux measurement by making contact with the steel plate) 1. In addition, by attaching the coil to the inner wall of the roll with the same axis as the roll, it is possible to construct a transformation rate measuring device, for example, by incorporating it into a rolling work roll, which is useful in rolling processes where there is no installation space. This also makes it extremely easy to measure the metamorphosis rate.

The number of coils built into the roll body may be either single or multiple, but the greater the number of coils, the higher the excitation ability or detection ability, so the coil length L (see Figure 2) should be as short as possible. It is recommended to incorporate a large number of coils to improve detection accuracy.

The reason for using a material with low magnetic permeability as the material of each roll body is to increase the number of lines of magnetic force passing through the object to be measured (steel plate) 1. In other words, if a material with low magnetic permeability is selected for the roll body, more lines of magnetic force will pass through the object to be measured, making it easier to detect "changes in the current flowing through the detection coil 3b" caused by changes in the magnetism of the object to be measured. This is the translation.

The thermometer 8 was installed to eliminate error factors caused by temperature changes in the steel plate, but each roll body and each coil are also equipped with temperature detection elements that detect their respective temperatures. Temperature is captured by a magnetic flux detector.

This is to correct changes in the electrical resistance of the coil and changes in the dielectric constant and magnetic permeability of the roll due to temperature changes.

By the way, the frequency of the current applied to the excitation coil 2b of the excitation roll 2 is preferably as low as possible in order to increase the current flowing to the detection coil 3b side. Therefore, the excitation device 6
Therefore, the excitation coil 2b should be excited at a low frequency.

<Operation> In order to measure the amount of transformation of a steel material using the amount of transformation measuring device shown in FIGS. 6 to generate a magnetic field by applying a low frequency current.

The part of the magnetic flux generated from the excitation coil 2b that passes through the object to be measured 1 is detected by the detection coil 3b of the detection ring 3, which also rotates in contact with the opposite surface of the object to be measured 1, and the phase difference is The signal is taken into the detector 4 and the magnetic flux detector 5, and the phase difference and magnetic flux intensity are detected.

Then, the signals from the phase difference detector 4 and the magnetic flux detector 5 (the signal from the magnetic flux detector 5 also incorporates elements related to the temperature of each roll and each coil as necessary), and furthermore, the signals from the thermometer 8. Based on the signal, the transformation amount calculator 7
Calculate the amount (rate) of metamorphosis with high accuracy.

The reason why the amount of transformation of the steel material can be calculated based on the phase difference is as follows.

That is, the phase difference θ is the frequency f of the alternating current. Electrical conductivity σ of the hollow material
(The electrical conductivity is determined by the chemical composition and surface temperature of the steel material) and the average magnetic permeability of the steel material? It is known that the phase difference θ is uniquely determined based on the following equation +1).

θ=F(f, σ, μ)...(1) Also, the average magnetic permeability is determined based on the steel plate thickness W and the amount of transformation η, and is expressed by the formula μ=G(W, η)... It is expressed as (2).

Therefore, if θl fl σ is known, 1 is calculated,
This means that the amount of transformation η can be calculated based on the seven values and W, etc.

In this case, as mentioned earlier, in order to eliminate error factors caused by temperature changes in the steel material, it is necessary to consider data regarding the temperature of the steel material, as well as changes in the electrical resistance of the coil due to temperature changes and the dielectric strength of the rolls. It goes without saying that data regarding the temperature of each roll and coil should be taken into account in order to correct for changes in magnetic flux and permeability.

On the other hand, the reason why the amount of transformation of the steel material can be calculated based on the leakage magnetic flux intensity is as follows.

In other words, since it is well known that the leakage magnetic flux intensity r changes in accordance with the transformation amount η of the steel material, the leakage magnetic flux varies depending on the chemical composition k, plate shape d, and processing conditions P of the steel material that affect the relationship between the two. By preparing a relationship curve that experimentally determines the relationship between the strength r and the amount of transformation η using the temperature t as a parameter, the corresponding relationship curve can be selected based on the detected leakage magnetic flux strength r, and the amount of transformation η can be determined based on the detected leakage flux strength r. It is possible to calculate Also, the above relationship curve is the chemical composition k of the steel material, the plate shape d. Processing conditions P,
The relational expression between temperature t and leakage magnetic flux strength r is η=f(r, d
, k, t, P) = (31), the amount of transformation η can be calculated from the leakage magnetic flux intensity r based on this relational expression.

Now, as is clear from the above explanation, the present invention
For example, the above-mentioned JP-A-59-174749 and JP-A-61-
No. 210942, the magnetic field generator and magnetic flux detector in the "device for measuring the amount of transformation of a steel material based on the leakage magnetic flux from the steel material to which a magnetic field is applied" are "equipped with an excitation coil or a detection coil. The main point is that the sensor is in the form of a roll that rotates in contact with the object to be measured, but this allows detection of leakage magnetic flux to be carried out with the magnetic field generator and magnetic flux detector in contact with the object to be measured. This makes it possible to solve the problem of ``measured values being affected by the magnetic permeability and conductivity of the atmosphere,'' which had been pointed out in conventional techniques that measure transformation rates without contact, and ``to make the generated magnetic field strong.'' It is possible to eliminate inconveniences such as "unless you do so, stable measurements cannot be made."

<Summary of Effects> As explained above, according to the present invention, the delay caused by the ferromagnetic α phase when magnetic flux passes through the steel material and the detection of the leakage magnetic flux intensity that has passed through the steel material can be detected by It is not affected by bending, warping of the leading and trailing ends, or even changes in the atmosphere, and can be performed easily and accurately under a relatively weak applied magnetic field, making it possible to easily carry out the process with high accuracy during processing on the steel processing line. Also, extremely useful industrial effects are brought about, such as the ability to easily and accurately measure the amount of transformation of steel materials after treatment.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing an embodiment of a steel transformation amount measuring device according to the present invention. FIG. 2 is a schematic explanatory diagram of the excitation roll and detection port in FIG. 1. FIG. 3 is a schematic explanatory diagram of a conventional transformation amount measuring device,
Figure 3(a) shows the situation during proper measurement, and Figure 3(a) shows the situation during proper measurement.
represents the situation at the time of inappropriate measurement. FIG. 4 is a schematic explanatory diagram of another example of the conventional transformation amount measuring device. In the drawings, 1... object to be measured (steel plate), 2a... excitation roll body, 3... detection roll, 3b... detection coil, 5... magnetic flux detector, 7... transformation Quantity calculator, 13. 15... Magnetic flux detector, 2... Excitation roll, 2b... Excitation coil, 3a... Detection roll body, 4... Phase difference detector 6... Excitation device, 12... Magnetic field Generator. 14...Magnetic flux concentrator.

Claims (1)

[Claims] In a device that measures the amount of transformation of a steel material based on leakage magnetic flux from the steel material to which a magnetic field is applied, both the magnetic field generator and the magnetic flux detector have a built-in excitation or magnetic flux detection coil and are in contact with the steel material to be measured. A device for measuring the amount of transformation of steel, characterized in that it is in the form of a rotating roll.