JPH02243933A - Method for measuring internal temperature of thin plate - Google Patents

Abstract

PURPOSE:To accurately measure the internal temperature by sending an ultrasonic wave from the transmitting element of an S0-mode electromagnetic ultrasonic wave transmitting and receiving element, receiving it by the receiving element and measuring its propagation time, and correcting the measured time with a measured value of the thickness of the thin plate. CONSTITUTION:Three electromagnetic ultrasonic wave probes 2(2a and 2b) are provided in the width direction of the steel plate 1 to measure temperature at three points in the width direction. Each probe 2 consists of a transmitting element 2a and a receiving element 2b, which are set at a distance of 500mm in the length direction of the steel plate 1. In this constitution, the ultrasonic wave is sent from the transmitting element and received by the receiving element to measure the propagation time, which is corrected with the measured value of the thickness of the thin plate to accurately measure the internal temperature of the thin plate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for measuring the internal temperature of a thin metal sheet such as a steel plate, an AI plate, or a Ti plate during a hot rolling process.

[Conventional technology]

Steel thin plates or non-ferrous metal thin plates such as AI plates and Ti plates are manufactured through only a hot rolling process or a hot rolling process followed by a cold rolling process. In such manufacturing processes, it is known that the crystalline state in which the material is deformed during the hot rolling process has a large effect on the properties of the manufactured thin sheet. is related to the internal temperature of the material during the hot rolling process. Particularly in the case of steel plates, the finish rolling temperature (temperature at the inlet and outlet of the finish rolling mill group) and coiling temperature (temperature at the coiler line) greatly influence the mechanical properties of the manufactured steel plate.

Therefore, detecting the internal temperature of a thin metal sheet such as a steel plate during the hot rolling process and controlling the temperature is extremely important when manufacturing a thin metal sheet.

Conventionally, a large number of radiation thermometers were installed on a hot rolling line to continuously measure the surface temperature of the material, and the internal temperature of the material was detected based on the measured values. However, this method only estimates the internal temperature based on the measured value of the surface temperature and the thickness of the material, so there was a problem that the internal temperature, which determines the crystalline state of the material, could not be accurately measured. .

A measurement method to solve this problem was developed in Japanese Patent Application Laid-Open No. 63-8
It is disclosed in Japanese Patent Application Laid-open No. 3625 and Japanese Patent Application Laid-open No. 83626/1983. These methods involve installing ultrasonic transmitting and receiving elements across the molten metal, determining the sound speed of the ultrasonic wave in the molten metal from the distance between the ultrasonic transmitting and receiving elements and the propagation time of the ultrasound, and calculating the characteristic temperature - sound velocity of the molten metal to be measured. This method attempts to measure the internal temperature of molten metal based on its characteristics, and it is conceivable to measure the internal temperature of the metal thin plate by using a thin metal plate instead of the molten metal in this measurement method. In this case, it is conceivable to use the attenuation of X-rays or γ-rays to measure the thickness of the thin metal plate.

[Problem to be solved by the invention]

However, the attenuation of x'ffA or γ-rays is a function of the density of the thin metal sheet, and the density is also a function of the temperature of the thin metal sheet, so it is impossible to determine the exact speed of sound using the conventional measurement method described above. There is a problem.

Furthermore, the conventional measuring method has the disadvantage that it is necessary to measure the plate thickness with high precision. Figure 6 shows the steel material temperature ('C)
It is a graph showing the relationship between the sound velocity (m/sec) of the ultrasonic wave ('#1 wave) and the sound speed (m/sec). Above the transformation point (approximately 700°C), the sound velocity change is approximately 0.8 m/sec/°C;
In the above, the sound speed is approximately 5000 m/s, so converting this sound speed change into a plate thickness change is 1.6 Xl0-'
(=0.815000). As a result, the plate thickness was reduced to 10
In the case of a crane, in order to measure the internal temperature with a measurement accuracy of l'c, it is necessary to use 1.6 μm (= lOn x 1.6
It is necessary to measure the plate thickness with an accuracy of ').

Even if the accuracy of temperature measurement is set to 10° C., a measurement accuracy of 16 μm is required, and there is a drawback that this accuracy cannot be achieved by plate thickness measurement using attenuation of X-rays or γ-rays.

In addition, when measuring the sound speed in a thin plate under high temperature using longitudinal waves or transverse waves, it is possible to use an electromagnetic ultrasonic probe, but a high frequency is used to resolve and measure multiple echoes. Therefore, it is necessary to suppress the lift-off between the thin plate and the probe to 2 to 3 mm or less, and there is a problem that it is difficult to use it online.

The present invention has been made in view of such circumstances, and is
By adding thickness correction to the mode propagation time,
An object of the present invention is to provide a method for measuring the internal temperature of a thin plate, which can accurately measure the internal temperature of a thin plate without requiring highly accurate thickness measurement, and which can be applied online.

[Means to solve the problem]

The method for measuring the internal temperature of a thin plate according to the first aspect of the present invention includes:
In the method of measuring the internal temperature of the thin plate based on the propagation time of the ultrasonic wave in the thin plate, the transmitting element of the S0 mode electromagnetic ultrasonic transmitting/receiving element provided at a certain distance
Mode ultrasound is transmitted and propagated through the thin plate, the S0 mode ultrasound propagated through the thin plate is received by a receiving element, the propagation time is measured, and this measurement time is calculated in the vicinity of the SO mode electromagnetic ultrasound transmitting/receiving element. The internal temperature of the thin plate is measured by correcting the measured value of the thickness of the thin plate in .

Further, in the method for measuring the internal temperature of a thin plate according to a second invention according to the present invention, in the first invention, the frequency of the S0 mode ultrasonic wave is f (MHz), and the maximum value of the thickness of the thin plate is T (
mm), f-T≦1.3.

Furthermore, the method for measuring the internal temperature of a thin plate according to a third aspect of the present invention is characterized in that, in the first or second aspect, the measurement accuracy of the thickness of the thin plate is 0.1 n or less.

[Effect]

In the method for measuring the internal temperature of a thin plate of the present invention, 80-mode ultrasonic waves are transmitted from the transmitting element of the S0 mode electromagnetic ultrasonic transmitting/receiving element provided at a certain distance on the thin plate, and received by the receiving element, The propagation time of this S0 mode ultrasonic wave is measured. On the other hand, the thickness of the thin plate near the installation position of the S0 mode electromagnetic ultrasonic transceiver element is measured. Then, the measured value of the propagation time is corrected using the measured value of the thickness. Then,
Even if the measurement accuracy of the plate thickness is low, the internal temperature can be measured with high accuracy, and since the low frequency 80 mode is used, the sound speed can be measured almost unaffected by on-line lift-off fluctuations.

〔principle〕

'Hereinafter, the principle of the present invention will be explained using an example in which the internal temperature of a carbon steel plate is measured.

Figure 3 shows the relationship between the steel plate temperature and sound velocity in the S0 mode at frequency 0, based on the longitudinal wave sound velocity and shear wave sound velocity of a carbon steel plate at 800 to 1200°C.Longitudinal wave,
The sound speed in the steel plate in transverse wave and S0 mode is VL and V, respectively.
,,V,. Then, each sound velocity is shown by the following equations (1) to (3), respectively.

λ, μ: lame constant, ρ: density of carbon steel plate Δ: indicates dispersion due to wavelength 8, and when the thickness of the steel plate is T, the above (4) approximated by the following (4) ), if Δ−■ becomes Δ−〇, the above formula (3) becomes the following formula (5).

By the way, when the Lamé constants λ and μ are determined from the above equations (1) and (21), the following equations (6) and (7) are obtained.

λ=l) (Vt "2Vs") ・"(6
)μ=ρ■s! (7) Then, by substituting these equations (6) and (7) into the above equation (5), the following equation (8) is obtained.

Error ΔV of v,o due to constant error. The ratio between V3G and the true value V3G is as shown in equation (9) below.

[(T+0.1) ”-T”) Therefore 8
Speed of sound in 0 mode ■. is a function of longitudinal wave sound speed VL + transverse wave sound speed ■, and these ■.

Since ■ is a function of temperature, the speed of sound in S0 mode is ■.

is a function of temperature, and FIG. 3 is a graph showing the relationship between the two.

S from Figure 3. ■Speed of sound in mode. The change with temperature is 0.65 m/sec/℃, which reduces the sound speed to about 4500 m7
seconds, its rate of change is 1.4 xlO-'/'c (
=0.65÷4500).

On the other hand, assuming Δ-50m and T=1 to 13, Δ(
Calculating the direct angle results in the result shown in Figure 4. Here, the plate thickness T is 0.
If we decide to measure with an accuracy of 1 dragon, this measurement (0, 2
T+0.01) (9) The error rate calculated based on equation (9) is illustrated in FIG. 5.

Find the relationship between the temperature and the 80 mode sound velocity at 8-■ as shown in Figure 3, and set Δ, the correction term based on 8, to 0.
．． If corrected by T measured with an accuracy of 1*n, S
0 mode sound velocity V,. When Δ=50n, if T≦13 fins, it can be determined with an accuracy of 3×10−′ or less, as shown in FIG. 5.

By the way, 80 mode electromagnetic ultrasonic transceiver probe (100k
Hz), if the transmitting and receiving elements are installed at a distance of 10 times the wavelength or more, and if the lift-off of the object to be measured is ±10, then the measurement error of the propagation time of the S0 mode ultrasound is 5X10- 'We know that the following can be achieved. Therefore, if the transmitter/receiver element is installed in such a state, the speed of sound can be measured with an accuracy of 5 xio-' or less. This error accuracy is the same as the sound speed error accuracy (3X
10-').

As described above, the plate thickness T was measured with an accuracy of 0.1 inch,
Moreover, when the plate thickness T is set to 13 mm or less, l×
Since the speed of sound can be sufficiently measured with an accuracy of 101, the measurement accuracy of the temperature measured from this is that the rate of change in the speed of sound is 1.4.
Since Xl0-', 7℃ (= (I Xl0-3
) ÷ (1,4X 10-').

In this way, in the present invention, there is no need to increase the measurement accuracy of plate thickness (accuracy of 0.1 m is sufficient in the present invention),
The internal temperature of the thin plate can be measured accurately (with an error of about 7° C. in the present invention).

〔Example〕

Examples of the present invention will be specifically described below.

FIGS. 1(a) and 1(b) are a plan view and a sectional view showing the implementation state of the measuring method of the present invention, and in the figures, 1 indicates a steel plate to be measured. . In the width direction of the steel plate 1, three sets of electromagnetic ultrasonic probes (EMAT) 2 are provided at appropriate distances apart, and the temperature is measured at three points in the width direction. Each set of electromagnetic ultrasound probes 2 is composed of a transmitting element 2a and a receiving element 2b, and the transmitting element 2a+receiving element 2
b is spaced apart by 500 fins in the longitudinal direction of the steel plate 1.

The transmitting element 2a and the receiving element 2b have substantially the same configuration, and the transmitting element 2a (receiving element 2b) includes two permanent magnets 20a with different polarities, which are provided with a steel plate 1 in between,
21a (20b, 21b), and the surface of the permanent magnet 20a (20b) on the upper surface side of the steel plate 1 has a second
As shown in the figure, a coil 30g (30b) is attached. Note that the permanent magnet used is a laminated layer of samarium cobalt.

The lift-off of the transmitting coil 30a, the receiving coil 30b, and the permanent magnets 21a and 21b on the lower surface side of the steel plate 1 is 20 mm, and the lift-off of the transmitting element 2a and the receiving element 2b is 20 mm, respectively.
Pinch rolls (not shown) are provided at positions spaced apart to suppress vertical movement of the steel plate 1 to less than ±10 degrees.

In such a configuration, the frequency is 80kHz, 5
Each set of electromagnetic ultrasonic probes 2 was excited at a repetition frequency of 64H2 by periodic parsed waves, and the internal temperature of the steel plate 1 during finish rolling was measured based on the above-described principle. Note that the propagation time is measured using the zero-crossing method with an accuracy of IQns.
EC, and the internal temperature was determined using the average value over 128 times (2 seconds).

A steel plate was manufactured by controlling the temperature based on the measurement results obtained in this manner. Therefore, compared to steel sheets manufactured using the conventional method, that is, temperature control based on temperature data obtained by estimating internal temperature using a radiation thermometer, the steel sheets manufactured using the method of the present invention have We were able to halve the variation in mechanical property values.

In this embodiment, a case has been described in which the internal temperature of a steel plate is measured, but it is of course possible to measure the internal temperature of a steel plate in the same manner as well.

〔Effect of the invention〕

As described in detail above, in the measuring method of the present invention, the internal temperature of a thin plate can be accurately measured without measuring the plate thickness with high accuracy. Also, at this time, the frequency f (M
Hz) and the maximum thickness T (in) of the thin plate.
When satisfying T≦1.3 and setting the plate thickness measurement accuracy to 0.1 mm or less, the internal temperature of the thin plate can be measured with an accuracy of about 7°C.

Further, even if a certain degree of lift-off fluctuation occurs in the thin plate, the internal temperature can be accurately measured, so the present invention has excellent effects such as being able to be used online.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the implementation state of the method for measuring the internal temperature of a thin plate according to the present invention, FIG. 2 is a plan view showing a part of the electromagnetic ultrasonic probe used in implementing the present invention, and FIG. is a graph showing the sound speed characteristics of S0 mode, Fig. 4 is a graph showing the velocity dispersion term of S0 mode, Fig. 5 is a graph showing the velocity error rate of S0 mode, and Fig. 6 is a graph showing the sound speed characteristics of longitudinal waves. It is. l... Steel plate 2... Electromagnetic ultrasound probe 2a...
Transmitting element 2b...receiving element 20a, 20b, 21
a, 21b ”・Permanent magnet 30a ... Transmission coil 0b ... Receiving coil patent

Claims (1)

[Scope of Claims] 1. In a method of measuring the internal temperature of a thin plate based on the propagation time of ultrasonic waves in the thin plate, the ultrasonic wave transmitting element of the S_0 mode electromagnetic ultrasonic wave transmitting/receiving element provided at a certain distance from the transmitting element of the S_0 mode electromagnetic ultrasonic wave transmitting/receiving element is transmitting sound waves to propagate through the thin plate;
The S_0 mode ultrasonic wave propagated through the thin plate is received by a receiving element, the propagation time is measured, and this measured time is corrected by the measured value of the thickness of the thin plate in the vicinity of the S_0 mode electromagnetic ultrasonic transmitting/receiving element. A method for measuring an internal temperature of a thin plate, comprising: measuring the internal temperature of the thin plate. 2. The thin plate according to claim 1, where f·T≦1.3, where the frequency of the S_0 mode ultrasonic wave is f (MHz) and the maximum thickness of the thin plate is T (mm). How to measure internal temperature. 3. The method for measuring the internal temperature of a thin plate according to claim 1 or 2, wherein the measurement accuracy of the thickness of the thin plate is 0.1 mm or less.