JPH05281063A - Measuring device for tension of steel material - Google Patents

Abstract

PURPOSE:To provide a steel material tension measuring device which can continuously noncontactedly measure tension acting on bar steel or wire material in a rolling process even under bad environment. CONSTITUTION:A steel material tension measuring device has a detecting section S composed of an exciting coil 5 wound on a concentric shaft, a detecting coil 4 concentrically wound inside the exciting coil 5, and a magnetizing coil 6 to magnetize a material M to be inspected set on the outer periphery of the exciting coil 5, a full wave commutating section 8 to convert a signal issued from the detecting coil 4 into a d.c. current, a computing section 11 to execute fixed compensating computation on the measured value of temperature of the material M to be inspected, and a difference computing section 12 to compute a difference between a d.c. signal issued from a commutating section 8 and a compensating signal issued from the computing section 11. Thus a measuring signal which is not practically influenced by the temperature change of the material M can be accurately obtained even under bad environment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for continuously measuring the tension applied to a steel bar or wire rod during rolling in a non-contact manner by utilizing the electromagnetic characteristics between the material to be tested and the electric coil. ..

[0002]

2. Description of the Related Art Generally, the dimensional accuracy of steel materials in rolling mills is a factor that affects the yield and quality of steel materials.
It was recognized that the best way to determine this is to constantly grasp and constantly control the tension of the material to be tested in addition to the rolling reduction control during hot rolling, and to accurately measure the tension of the steel material during rolling. Development of the detection method is desired.

For example, Japanese Patent Application Laid-Open No. 57-197434 proposes a tension measuring device which has a magnetic circuit composed of a detection coil and a steel material and utilizes the property that the magnetic permeability of the steel material changes due to the tension applied to the steel material. ing. This is to detect the magnetic permeability due to the tension or compression force of the steel material to be measured, that is, the material to be measured, and calculate the tension from the detected magnetic permeability, and how to maintain a constant gap between the magnetic permeability measuring element and the steel material to be measured. A major problem in measurement is that the pressing force sensor detects the interval and maintains the interval constant.

[0004]

However, according to the above-mentioned tension measuring device, the installation accuracy between the magnetic permeability measuring element and the object, that is, the interval setting accuracy is one of the important factors. During continuous measurement, it is difficult to maintain a constant gap and pressing force, and the gap fluctuates, making accurate measurement impossible. Further, since the magnetic permeability is the detection principle, it is impossible to measure non-magnetic metal. Further, the magnetic permeability of the ferromagnetic metal is greatly affected by the temperature change and changes in a complicated manner. Therefore, there is no apparatus for applying the method for compensating for it, and it is difficult to measure with good reliability in practical use.

An object of the present invention is to magnetically saturate the material to be tested with a magnetizing coil so that the relative permeability is substantially one, to correct the variation in the conductivity due to temperature, and to adjust only the change component of the conductivity of the material to be tested due to the tension. It is to provide a tension measuring device that can measure iron or non-metals by extracting.

[0006]

DISCLOSURE OF THE INVENTION A tension measuring device for a steel bar or a wire according to the present invention comprises an exciting coil wound around a concentric shaft.
(5) and the detection coil (4) wound inside the exciting coil (5)
And a detection unit (S) consisting of a magnetizing coil (6) for magnetizing the material to be tested (M) provided on the outer circumference of the exciting coil (5), and a signal from the detecting coil (4) is converted to DC. A full-wave rectification unit (8) to be converted and a calculation unit (11) for performing a correction calculation based on the temperature measurement value of the test material (M), and a difference calculation unit (D) for performing a difference calculation between the DC signal and the correction calculation signal. It is characterized by consisting of 12) and. The symbols in parentheses indicate the corresponding elements in the embodiments shown in the drawings and described later.

[0007]

[Operation] The magnetizing coil (6) magnetically saturates the test material (M) with the test material (M) penetrating the detection part (S) to substantially reduce the relative magnetic permeability of the test material (M). Every second. The exciting coil (5) magnetizes the material under test (M). The detection coil (4) generates a voltage corresponding to this magnetization, and this voltage corresponds to the conductivity of the test material (M), and the conductivity is affected by the tension of the test material (M). receive. That is, the voltage generated by the detection coil (4) depends on the tension of the test material (M). This voltage, that is, the detection signal
(8) converts to DC. From this direct current and the temperature measurement value of the test material (M), the calculation unit (11) performs temperature correction calculation of the conductivity, and the difference calculation unit (12) outputs the temperature correction calculation output signal and the full-wave rectification unit ( Take the difference from the DC output signal in 8) and use that output as the tension signal.

More specifically, the test material (M) is
It penetrates through the central position of the detection unit (S) having a hollow cylindrical structure.
An alternating current is applied to the exciting coil (5) and a direct current is applied to the magnetizing coil (6) to completely magnetically saturate the test material (M). At this time, the magnetic field generated by the excitation coil (5) acts on the material to be tested (M) and an eddy current flows, a secondary magnetic field is generated by it, and the combined magnetic field interlinks with the detection coil (4), An alternating voltage is induced in the detection coil (4). This induced voltage is a voltage signal proportional to the conductivity, magnetic permeability and excitation frequency of the test material (M), and inversely proportional to the square of the filling rate (radius b of the test material M / radius a of the detection coil 4). Is. That is, when the test material (M) is concentrically contained, the resistance component or reactance component changes due to the eddy current loss in the test material (M),
The two independent parameters as the change factor are the normalized frequency F and the filling rate.

Here, the normalized frequency F is F≡ωL ₂ / R ₂ ≡2πfμσa ² (1) where f: excitation frequency [Hz] a: radius of detection coil [m] μ: permeability of conductor [H / m] R ₂ : Conductor resistance component [Ω] σ: Conductor conductivity [Ωm] ωL ₂ : Conductor reactance [Ω] where the conductor (test material M) is previously magnetically saturated The normalized frequency F is determined by the excitation frequency f, the coil radius a, and the electrical conductivity σ of the conductor (material M to be tested). That is, the normalized frequency F can be expressed by the ratio of the inductance component and the resistance component generated in the conductor. Once the conductor shape and coil specifications are determined, they are constant and do not contribute to the detection signal, so they are canceled by the signal processing circuit described later. The induced voltage signal detected as described above is a signal when magnetically saturated at a constant frequency of a constant current, and a change due to the conductivity σ of the conductor can be detected. That is, the metal conductor has a characteristic that the conductivity changes substantially in inverse proportion to the internal stress when external tension is applied. It is also well known that it is inversely proportional to the temperature rise.

Therefore, when tension is applied to the test material M (the conductor), the eddy current of the test material (M) decreases, and the voltage signal induced in the detection coil (4) has a conductivity higher than that in the non-tensioned state. Increase in proportion to the decrease. In addition, since it has the conductivity characteristic according to the temperature peculiar to the test material, this temperature characteristic table is prepared, the increase rate of conductivity corresponding to the temperature of the conductor is obtained, and the increase rate is multiplied by the tension. The product of the detected voltage and the induced voltage signal of the detection coil is used as the correction amount. Then, a highly accurate tension signal is obtained by performing a difference calculation between the induced voltage signal and the above-mentioned correction amount.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an outline of one embodiment of the present invention. In FIG. 1, 1 is an oscillator, 2 is a power amplifier that amplifies the output of the oscillator 1 and has a constant current function, 3 is a DC power supply, and M
Is a material to be inspected, S is a detection unit, and 6 is a magnetizing coil for completely magnetically saturating the material to be inspected M.

FIG. 2 shows a cross section of the detecting portion S. Detector S
Is a through-type coil in which the coils 4 to 6 are wound on a concentric axis, and the test material M passes through the through-hole. Although not shown in FIG. 2, there are rolling mills in front of and behind the detection unit S so that tension is applied to the test material M. In the structure of the detection unit S, the detection coil 4, the excitation coil 5, and the magnetizing coil 6 are wound around the outer circumference from the inner circumference side. The output signal of the detection coil 4 is amplified by the signal amplifier 7 and converted from an AC signal to a DC signal by the double-wave rectifier 8. The DC amplifier 9 amplifies the DC signal of the double-wave rectifier 8 and receives the DC voltage signal from the bias adjuster 10 to perform a difference calculation. That is, when the material M to be inspected is passed through the detecting portion in a tensionless state, a DC signal determined by the filling rate and the conductivity at that time is output from the DC amplifier 9, so that a negative voltage equivalent thereto is set in the bias adjuster 10. Then, this negative voltage is added to the DC signal of the double-wave rectifier 8 to make the output of the DC amplifier 9 at zero tension zero voltage. T is a temperature sensor,
The temperature of the test material M is measured. The temperature information of the temperature sensor T and the signal of the DC amplifier 9 are input to the temperature correction calculator 11, and the temperature correction calculator 11 responds to the temperature change of the conductivity σ of the test material M based on these signals. Correct the amount of change. This correction signal and the signal from the DC amplifier 9 are given to the difference calculator 12. The difference calculator 12 outputs a difference value signal obtained by subtracting the correction signal of the temperature correction calculator 11 from the signal of the DC amplifier 9.

The ratio L / D of the length L of the exciting coil 5 of the detector S and its diameter D is preferably at least 3 or more. That is, if L / D is small, the magnetic flux density distribution generated by the excitation coil 5 becomes non-linear, and the passing position of the material M to be inspected shifts, which changes the detection voltage of the detection coil 4 and causes an error. Although not shown, the detection coil 4 is preferably as short as possible with respect to the length L of the excitation coil 5, and in order to maintain high accuracy, the inventors have found that The ratio L ′ / L of the length L ′ and the length L of the exciting coil 5 is preferably 1/50 or less.

FIG. 6 shows the level shift of the detection signal according to the ratio L / D. This graph shows the relative output of the detection coil 4 when the test material having a diameter of 10 mm is moved left and right from the center point of the cross section of the exciting coil 5 with L / D as a parameter, even if the filling rate (ν) is the same. The larger the displacement from the center point, the lower the output and this becomes an error. In order to reduce the measurement error due to the position variation of the material M to be inspected, L / D needs to be at least 3 or more. By the way, the coil specifications are as follows: Excitation coil 5: inner diameter 50 mm, length 150 m
m, detection coil 4: outer diameter 50 mm, length 3 mm.

When tension is applied to the material M to be tested, the DC amplifier 9
Outputs a voltage signal on which the change in conductivity due to temperature and tension is superimposed, and this voltage Ve is: Ve = K {f (σ ₁ ΔT), f (σ ₁ 'ΔH), f (ν)}・ It becomes (2). Here, k is a constant determined by the excitation coil current and the structure of the detecting portion, σ ₁ ΔT is a change in conductivity due to temperature change, σ ₁ 'ΔH is a change in conductivity due to tension change, and ν is a filling rate. In the above equation (2), the f (ν) component is a DC component that does not depend on tension, and corresponds to the output level of the DC amplifier 9 when the material M to be tested is present and there is no tension. This is canceled by the bias adjuster 10 in the DC amplifier 9 by the difference calculation. Further, the f (σ ₁ ΔT) component is converted from the amount of change in conductivity (σ ₁ ΔT) due to temperature in the correction calculator 11 in the near future, and the converted value and the f (ν) component of the DC amplifier 9 are converted. It is obtained by the product of the canceled output. The difference calculator 12 cancels this product from the output obtained by canceling the f (ν) component of the DC amplifier 9. Thus, the output of the difference amplifier 12 is f
It becomes the (σ ₁ 'ΔH) component, and the desired tension signal is obtained. The conductivity characteristics of steel for obtaining this signal are clarified.

FIG. 4 shows the specific resistance (1
/ Σ). As is apparent from FIG. 4, a change in the specific resistance is observed in proportion to temperature up to about 900 ° K. Therefore, the correction can be realized based on the temperature information. On the other hand, FIG. 5 shows the rate of increase in resistivity due to the workability (tension) of steel materials.

In FIG. 5, the horizontal axis represents the workability, the elastic limit being 100%, and the vertical axis represents the rate of increase in resistivity.
The rate of increase in resistivity is about 20 at the elastic limit of 100%.
However, the processing rate in the tension (stress) range targeted by the inventors is 40% or less, which is almost linear in this range. It is possible to output the output of the difference amplifier 12 as a signal substantially proportional to the tension due to the conductivity characteristic of the workability of the steel material.

FIG. 3 shows the results of tension measurement by the device shown in FIG. The horizontal axis of FIG. 3 represents tension (stress). The vertical axis represents the output levels of the DC amplifier 9 and the difference amplifier 12,
Difference amplifier 12 when the tension (stress) is 5 kgf / mm ²
The relative value with the output level of 1 as a reference (100%) is shown.
A curve a in FIG. 3 is a signal obtained by the DC amplifier 9 before temperature correction, and shows a characteristic in which the amount of change in conductivity due to temperature and tension is superimposed. A curve b in FIG. 3 shows a true tension characteristic after temperature correction. This measurement example has a diameter of 1
It was obtained by applying tension to a 0 mm steel material while raising the temperature to about 500 ° C. As can be seen from the b characteristic after temperature correction, the output characteristic corresponding well to the tension is obtained. However, at a low tension of 0.5 kgf / mm ² , it exhibits non-linear characteristics. This is because the composition variation of the material M to be inspected and the noise of the signal processing circuit system are superimposed and the S / N ratio is lowered. Since the practical area has a tension exceeding this range, this phenomenon has no practical problem.

[0019]

As is apparent from the above description, according to the present invention, the material to be tested is magnetically saturated in a non-contact manner, the influence of the magnetic permeability μ is eliminated, the temperature dependence of the conductivity is corrected, and the external stress is applied. Since only the conductivity change component is separated and extracted, accurate tension measurement is possible, and in particular, it is non-contact and can be continuously measured even in a bad environment, so that it can be easily applied online. Further, in the conventional rolling process, it was difficult to obtain a satisfactory control performance such as responsiveness and accuracy, because the structure of the rolling control model was complicated and the processing time was long because it was difficult to measure the tension online. However, by providing the present invention, it is possible to obtain high effects such as system simplification, stabilization of operation, improvement of dimensional accuracy, and quality improvement, and it is possible to improve productivity. ..

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of an embodiment of the present invention.

2 is a cross-sectional view of a detection unit S shown in FIG.

3 is a graph showing an output a of the DC amplifier 9 and an output b of the difference amplifier 12 shown in FIG.

FIG. 4 is a graph showing changes in resistivity of steel materials due to changes in temperature.

FIG. 5 is a graph showing the rate of increase in resistivity depending on the workability of steel materials.

6 is a graph showing variations in the output voltage of the differential amplifier 12 shown in FIG. 1 due to L / D of the exciting coil 5 shown in FIG. 2 and displacement of the passing position of the steel material.

[Explanation of symbols]

S: Detection unit M: Test material 1: Oscillator 2: Constant current power amplifier 3: DC magnetizing power supply 4: Detection coil 5: Excitation coil 6: Magnetization coil 7: Signal amplifier 8: Double wave rectifier 9: DC amplifier 10: Bias adjuster 11: Temperature correction calculator 12: Difference amplifier

Claims (2)

[Claims] 1. An apparatus for electromagnetically measuring the tension of a steel bar or a wire rod by using an electric coil, wherein an exciting coil wound on a concentric shaft, a detecting coil wound inside the exciting coil, and the exciting coil. A detection unit consisting of a magnetizing coil for magnetizing the test material provided on the outer circumference of the coil, a full-wave rectification unit that converts the signal from the detection coil to DC, and a correction calculation based on the temperature measurement value of the test material A tension measuring device for a steel product, comprising: a calculation unit for performing the above-mentioned calculation; and a difference calculation unit for calculating a difference between the DC signal and the correction calculation signal. 2. The ratio L / D of the diameter D to the length L of the exciting coil of the detecting portion is 3 or more, and the length L'of the detecting coil is
The tension measuring device for steel according to claim 1, wherein the exciting coil length L is 1/50 or less.