JP3039308B2 - Refractory thickness measurement method using elastic waves - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thickness measuring method for measuring the thickness of a refractory brick or the like lined inside a steel furnace of an industrial furnace, particularly a steelmaking blast furnace, from the surface of the steel shell using an elastic wave with high accuracy. About.

[0002]

2. Description of the Related Art For example, a blast furnace for steelmaking has an outer shell made of a steel shell and a refractory brick lining inside. Since the refractory brick at the bottom of the blast furnace is constantly exposed to hot metal, it gradually wears out with the operation of the blast furnace. May be decreasing. It is necessary to accurately measure the change in the remaining thickness of refractory during blast furnace operation and accurately estimate the life expectancy of the blast furnace.
This is very important for preventing serious accidents such as erosion of iron shell or outflow of hot metal by hot metal and effective utilization of blast furnace assets.

Hitherto, many methods have been proposed for measuring the remaining thickness of refractory bricks in blast furnaces. The main methods are exemplified below.

(1) The simplest method is to strike the surface of the steel shell of the blast furnace with a hammer or the like, and the elastic waves generated by the strike propagate through the refractory, reflect on the surface of the core side, and again. Measure the round trip time to return to the steel surface,
There is a method of measuring the thickness of the refractory brick from the propagation speed of the elastic wave in the refractory and the reciprocation time obtained in advance.

(2) Japanese Patent Application Laid-Open No. 49-50961 discloses that a sine wave exciting force of an audio frequency is applied to a brick to be measured by changing the frequency, the mechanical impedance is measured, and the peak value of the mechanical impedance is measured. A method for non-destructively measuring the thickness of a brick for an industrial furnace from outside the furnace has been proposed.

(3) Japanese Patent Application Laid-Open No. 58-27002 discloses that an opening is formed in a part of a steel shell, a metal rod is directly connected to a refractory, and one end of the metal rod is hit efficiently to refractory fire. A method has been proposed in which an elastic wave is generated in an object, the time required for the elastic wave to reciprocate in the refractory is measured, and the thickness of the refractory is measured from the round-trip time and the propagation speed of the elastic wave in the refractory. .

(4) A potential pulse is applied to mutually insulated metal coaxial wires or parallel metal wires embedded in the thickness direction of the furnace wall, and the reflection time of the potential pulse from the tip of the metal conductor is measured. TD for metal wire length and furnace wall thickness
A method called an R (Time Domain Response) method has also been proposed.

[0008]

The method (1) using a reflected wave has the advantage that the processing contents for calculating the thickness of the refractory brick from the apparatus configuration and the measurement data are extremely simple, and the measurement can be performed at an arbitrary place. However, it has not been put into practical use at present because of the following problems.

Most of the vibration energy due to the impact is consumed as the vibration energy of the iron shell itself, and the efficiency of conversion into elastic waves propagating through the refractory brick is extremely low. For this reason, the vibration of the iron shell itself is larger than the vibration of the elastic wave propagating in the refractory brick and reflected. Therefore, it is very difficult to detect a weak elastic wave that propagates through the refractory brick mixed with the above and returns by detecting it on the surface of the steel skin and identify it as a reflected wave.

[0010] The measurement accuracy in the method for measuring the round-trip time of propagation in bricks is about one-fourth of the wavelength. The wavelength of the elastic wave propagating in the refractory is considerably long, and the accuracy of measuring the thickness of the refractory by this method is considerably deteriorated (frequency 10).
About 600mm at 00Hz). Along with this,
The ability to detect cracks in refractory bricks is also very low.

In the measuring method described in Japanese Patent Application Laid-Open No. 49-50961 (2), in order to apply a sine wave exciting force of an audio frequency to a brick to be measured and obtain a peak value of a mechanical impedance of the brick. In addition, it is necessary to apply a sufficiently large sine wave exciting force, and it is necessary to sweep the frequency of the exciting force within a predetermined range. Therefore, the apparatus for performing this method is extremely complicated and large.

The method for measuring the thickness of a refractory described in JP-A-58-27002 described in (3) above requires that a steel shell at the measurement point be opened and the refractory and a metal rod be directly connected. In addition, the measurement operation is extremely complicated, and the time and cost required for the measurement are enormous. In addition, it is difficult to always keep the state of connection between the refractory and the metal rod and the state of hitting of the metal rod by the hammer (strength, hitting position, etc.) constant,
Poor reproducibility of measurement results.

Further, in the TDR method of the above (4),
In order to measure the thickness of the furnace wall, it is necessary to embed a metal wire in a measurement place in advance, so that the measurement place is limited to a place where the metal wire is buried before burning in the blast furnace. In addition, for example, if the metal wire breaks and insulation failure occurs during the operation of the blast furnace for, for example, over 10 years, there is a disadvantage that the measurement at that location becomes impossible thereafter.

The present invention has been made in view of the above-mentioned problems of the prior art, and has a thickness for accurately measuring the thickness of a refractory brick or the like lining the inside of a steel shell from the surface of the steel shell using an elastic wave. It is intended to provide a measuring method.

[0015]

The present invention relates to a method for measuring the thickness of a refractory stretched on the inner surface of a steel shell from a resonance frequency component obtained when an elastic wave is propagated. The methods from (3) to (3) are summarized.

(1) First method A method for measuring the thickness of a refractory, which is performed according to the following procedures.

Vibration is applied to the skin.

[0018] The iron skin from the vibration response to the vibration of the
Alternatively, the vibration response frequency spectrum from which the vibration response signals of the iron shell and the stamp material are removed is measured.

The thickness of the refractory is calculated from the peak frequency of the vibration response frequency spectrum.

(2) Second method A method for measuring the thickness of a refractory, which is performed according to the following procedures.

A plurality of vibrations having different excitation strengths are applied to the steel.

A vibration response frequency spectrum corresponding to the plurality of excitation intensities is measured.

The difference processing is performed on the value of the vibration response frequency spectrum for each excitation intensity.

The thickness of the refractory is calculated from the peak frequency of the vibration response frequency spectrum subjected to the difference processing.

(3) Third Method A method for measuring the thickness of a refractory, which is performed according to the following procedures.

Vibration is applied to the skin.

A vibration frequency spectrum and a vibration response frequency spectrum obtained by removing a predetermined frequency from each of the vibration applied to the above-mentioned steel and the vibration response thereto are measured.

The vibration response frequency spectrum is normalized by taking the ratio between the vibration response frequency spectrum and the excitation frequency spectrum.

The thickness of the refractory is calculated from the peak frequency of the normalized vibration response frequency spectrum.

As the normalized vibration response frequency spectrum used in the above, it is desirable to use the one that has been subjected to the difference processing by a plurality of excitation vibrations performed by the second method.

[0031]

FIG. 1 is a diagram schematically showing the configuration of an apparatus for carrying out the method of the present invention (first to third methods). Note that a portion surrounded by a broken line in the figure is used when implementing the third method.

Reference numeral 1 denotes an iron shell of a furnace (for example, a blast furnace), reference numeral 3 denotes a refractory brick, and reference numeral 2 denotes a stamp material in the middle. In the method of the present invention, the thickness of the refractory brick 3 is measured.

First, a procedure and a device configuration common to the implementation of the first to third methods of the present invention will be described with reference to FIG.

A vibration is applied to the surface of the steel shell 1 on the refractory brick 3 whose thickness is to be measured. In order to propagate the elastic wave into the refractory brick with good reproducibility, the vibration is applied by hitting with a hammer 4 composed of an air hammer or an electric hammer. A hitting tip 5 made of a suitable hard plastic is attached to the tip of the hammer 4 in order to generate an elastic wave in a frequency band required for measurement (for example, 500 to 3000 Hz).

A striking strength meter 6 is attached to the rear of the striking tip 5 to monitor the striking strength of the hammer 4 against the steel bar. The vibration response of the steel 1, the stamp material 2 and the refractory brick 3 at the time of hammering is sampled by a vibration sensor 7 attached to the surface of the steel. Although an accelerometer is used as the vibration sensor 7,
In addition, a sensor for measuring vibration such as a displacement meter can be used. The vibration response signal collected by the vibration sensor 7 is amplified at a predetermined magnification by the amplifier 8a, and then input to the frequency analysis device 10 via the filter 9a to calculate the vibration response frequency spectrum y (f).

After the calculated vibration response frequency spectrum is stored at a predetermined position in the memory 12, the signal processor 1
At 1, it is provided to the arithmetic processing described later.

In the embodiment shown in FIG. 1, the frequency analysis device 10 includes an A / D converter and a Fourier transform unit for Fourier transforming the A / D converted vibration response signal to calculate a frequency spectrum. Was used. In addition, a commercially available FFT analyzer (which can change the frequency band to be analyzed by changing a built-in program) can be used as the frequency analysis device 10. Further, an A / D converter and a device which takes in the A / D converted signal into a computer and calculates a frequency spectrum by software may be used. Further, an analog frequency analysis device that analyzes the frequency of the band-limited vibration signal as an analog signal using a heterodyne detector or the like may be used.

Hereinafter, the principles and specific embodiments of the first to third methods of the present invention will be described with reference to FIG.

[First Method] The vibration response signal of the iron shell or the iron shell and the stamp material (hereinafter referred to as the skin material) is 500
Appears remarkably in a frequency band of about 700 Hz. In this method, a vibration response signal in the frequency band is investigated in advance, and a band-pass filter is used as the above-described filter 9a, thereby removing the signal in this frequency band and transmitting a vibration response signal of only the refractory brick. It is an embodiment. This method is effective when the resonance peak of the vibration response frequency spectrum of the refractory brick is clear and appears at a position sufficiently separated from the resonance peak of the vibration response frequency spectrum of the skin material.

First, an exciting force having a strength and a frequency band necessary for measuring the thickness of the refractory brick is applied to the surface of the steel shell 1 by hitting the hammer 4. The vibration response at the time of the impact is sampled by the vibration sensor 7 and amplified by the amplifier 8a. Then, the above-mentioned vibration response signal of the steel material and the mechanical noise and the noise generated during the operation of the blast furnace are obtained from the vibration response signal in the band-pass filter 9a. Eliminate electrical noise. The vibration response signal subjected to the band limitation is input to the frequency analysis device 10, and the vibration response frequency spectrum y (f) is calculated.

Next, the signal processor 11 sets the frequency fp at which the peak of the vibration response frequency spectrum y (f) is given.
Is used to calculate the brick thickness d according to the following equation (1).

D = (n · v) / (2 · fp) −dm−ds (1) where, dm: steel shell thickness, ds: stamp material thickness,
n: integer, v: elastic wave propagation velocity function in steel, stamp material and brick As described above, the first method has the following effects.

(1) By striking the surface of the steel skin with an air hammer or the like, elastic waves having a required intensity and a frequency range (for example, 500 to 3000 Hz) can be propagated within the refractory brick with good reproducibility.

(2) When the thickness of the brick is measured using the frequency that gives the peak of the vibration signal on the frequency axis, when a low-frequency elastic wave (frequency: 500 to 3000 Hz) is propagated into the refractory brick Of measurement accuracy is suppressed.

(3) Since the vibration response signal of the iron shell material and the mechanical noise and the electric noise generated during the operation of the blast furnace which are obstructive to the measurement are removed from the vibration response signal, the vibration response signal of only the refractory brick is detected. Measurement accuracy is improved.

[Second Method] In this method, when extracting the vibration response of only the refractory bricks in the first method, a plurality of vibrations and the difference between the respective vibration response frequency spectra obtained therefrom are extracted. This is performed in processing. In the vibration response frequency spectrum, the resonance peak of the skin material and the refractory brick appear at a relatively close position, the measurement area of the refractory brick is relatively wide, and the resonance peak of the skin material changes depending on the measurement position. It is effective in the case.

Hereinafter, similarly to the first method, a description will be given based on an example in which the steel surface is hit with two types of strong and weak intensities as a plurality of strengths using the apparatus configuration of FIG. The impact strength / strength means strength enough to vibrate the refractory brick through the skin material (for example, about 2000 Kgf), and hitting strength / weak strength means strength enough to vibrate only the skin material ( (About 200 kgf).

As the filter 9a, a filter (for example, a low-pass filter) for roughly limiting the frequency band for removing mechanical noise and electric noise generated during the operation of the blast furnace is used. With this band limitation,
There are advantages that the calculation time for calculating the frequency spectrum by the frequency analyzer 10 can be reduced, and that alias noise during A / D conversion can be suppressed.

First, similarly to the first method, strong / weak 2
Vibration response frequency spectra ys (f), yw obtained when the steel surface is hit with different types of impact strength
(F) is calculated and stored in the memory 12. Next, in the signal processor 11, the difference processing is performed by the following equation (2), and the difference vibration response frequency spectrum y2 (f) y2 (f) = ys (f) -c.yw (f) (2) Here, c: constant The difference vibration response frequency spectrum y2 of the difference processing result
Using the frequency fp giving the peak of (f), the brick thickness d is calculated by the above equation (1). As described above, when this method is applied, the following effect is added to the first method.

Of the vibration responses obtained by the two types of impact strength, ys (f) includes the vibration response of the skin material and the refractory brick, while yw (f) includes the skin response. The vibration response of the material alone is included. Therefore, by performing the difference processing between ys (f) and yw (f), the vibration response of the skin material can be removed, and the vibration response of the refractory brick can be detected with high accuracy, and the measurement accuracy is improved. .

[Third Method] In this method, the first method and the second method described above are used in order to suppress the influence of variations in the reproducibility of the vibration state (strike strength, frequency distribution of elastic waves generated at the time of strike, etc.). The ratio of the vibration response frequency spectrum obtained by the vibration sensor attached to the surface of the iron skin in the method 2 to the frequency spectrum of the excitation signal obtained by the impact strength meter attached to the hammer is determined. It is normalized by

First, the vibration response frequency spectrum y (f)
Is calculated in the same manner as in the first method and the second method. At the same time, similarly to the vibration response signal collected by the vibration sensor 7, the vibration signal collected by the striking strength meter 6 attached to the hammer 4 is transmitted to the amplifier 8b and the filter 9b (FIG. 1).
(Enclosed by a broken line) is input to the frequency analysis apparatus 10. Here, a band-pass filter having the same frequency band as the band-pass filter 9a used in the first method and the second method is used as the filter 9b. An excitation frequency spectrum x (f) is calculated in the frequency analyzer 10 from the excitation signal whose band is limited. The vibration response frequency spectrum y (f) and the excitation frequency spectrum x (f) are stored in a predetermined memory 12, respectively.
By calculating the ratio by the signal processor 11, the vibration response frequency spectrum is normalized. As a method of calculating the normalized vibration response frequency spectrum h (f), the following equations (3) and (4) can be mentioned, but it is desirable to use the equation (4).

H (f) = y (f) / x (f) (3) h (f) = {x (f) ′ · y (f)} / ｛| x (f) | ² + 1 / c｝ · (4) where f: frequency (KHz) x (f): excitation frequency spectrum, y (f): vibration response frequency spectrum, c: constant, x (f) ′: x ( f) Conjugate complex number When this method is applied to the second method, the second
In the same manner as in the above method, normalized vibration response frequency spectra hs (f) and hw (f) corresponding to the above-mentioned plurality of excitations are calculated, and h2 (f) is calculated by the following equation (5).

H 2 (f) = h s (f) −c · h w (f) (5) where c is a constant. Next, signal processing is performed in the same manner as in the first method and the second method. The normalized vibration response spectrum h
The brick thickness d is calculated by the above equation (1) using the frequency fp giving the peak of (f) or h2 (f).

As described above, when this method is applied, the following effects are added to the first method and the second method.

By normalizing the vibration response frequency spectrum with the vibration signal frequency spectrum, the vibration state (strike strength,
Variations in measurement due to fluctuations in the frequency distribution of elastic waves generated at the time of impact are suppressed, and measurement reproducibility is improved.

In any of the first to third methods described above, if the stamp material has peeled off or slipped off from the steel or refractory brick in the vicinity of the measurement place, the steel and the fireproof Since a gap is formed between the brick and the brick, it is extremely difficult to transmit an elastic wave into the refractory brick even when the steel surface is hit. In this case, it becomes impossible to specify the resonance peak frequency fp of the refractory brick on the vibration response frequency spectrum y (f) or h (f). At this time, the mortar material is press-fitted in the vicinity of the measurement place, and a pretreatment for eliminating the gap between the steel shell and the refractory brick is performed, so that the brick thickness can be measured by the above method.

Further, when it is possible to directly apply an exciting force to the refractory due to the opening of the steel shell or the like, the vibration of the refractory obtained when the surface of the refractory is struck with a hammer is used. Measure using a vibration sensor attached to the object surface,
It goes without saying that the thickness of the refractory can be measured by the method of the present invention.

[0059]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows a measurement procedure of an embodiment in which the second and third methods of the present invention are implemented by the apparatus configuration shown in FIG. FIG. 2 shows a normalized vibration response frequency spectrum hs (f) obtained when the steel surface is struck with a striking strength / strong (about 2000 Kgf) and a striking strength / weak (about 200 Kgf) [FIG.
(A)], hw (f) [FIG. 2 (b)] and the difference processing result h2 (f) [FIG. 2 (c)]. 2A and 2B, the resonance peak of the surface material is dominant in FIG. 2A and FIG. 2B, but in FIG. 2C obtained by performing the difference processing, the resonance peak is removed. The process by which the resonance peak of the refractory brick becomes apparent becomes apparent.
The frequency f of the resonance peak of the difference processing result h2 (f)
The brick thickness obtained by using equation (1) from p is about 65
It was 0 mm.

On the other hand, FIG. 4 schematically shows a result of measurement using the core sample at the measurement location. In FIG. 4, the solidified material is a portion where the waste of the refractory brick and the contents of the furnace are mixed and hardened, and the embrittlement portion is a portion where the refractory brick is deteriorated by thermal stress or the like (about 130 m).
m), the sound part indicates the part of the refractory brick still having the refractory function to be measured. In FIG. 4, the brick thickness of the healthy part at the measurement location was about 630 mm, and it was confirmed that the thickness of the refractory brick could be measured accurately by the method of the present invention.

FIG. 3 shows a measurement process of another embodiment similarly performed by the first and third methods.

FIG. 3 shows the impact strength and strength (about 2000 kgf).
And the vibration response frequency spectrum ys obtained when the steel surface was hit with a low impact strength (about 200 kgf)
(F) [FIG. 3 (a)], yw (f) [FIG. 3 (b)] and an example of the difference processing result y2 (f) [FIG. 3 (c)] are shown. From FIG. 3, in FIGS. 3A and 3B,
Although the resonance peak of the surface material or the like is dominant, FIG. 3 (c) as a result of performing the difference processing clearly shows a process in which the resonance peak is removed and the resonance peak of the refractory brick becomes apparent. The brick thickness obtained by using the equation (1) from the frequency fp of the resonance peak of the difference processing result y2 (f) was about 880 mm. On the other hand, the measurement result of the thickness of the refractory brick by the core sample at this measurement place was about 90%.
0 mm, and both agree well.

[0063]

As described above, according to the method of the present invention, the following effects are exhibited in the thickness measurement using an elastic wave, and it is possible to realize excellent thickness measurement accuracy of a refractory.

(1) By measuring the thickness of the brick using the resonance frequency, a low-frequency elastic wave (frequency band: 50
(0-3000 Hz) is suppressed from lowering the measurement accuracy that occurs when propagating into the refractory brick.

(2) The measurement accuracy is improved by removing the vibration response that hinders the measurement of the skin material and detecting the vibration response of only the refractory brick.

(3) By normalizing the vibration response frequency spectrum with the excitation frequency spectrum, the influence of the excitation state is suppressed, and the reproducibility and accuracy of the measured values are improved.

[Brief description of the drawings]

FIG. 1 is an apparatus configuration diagram of an example in which a method of the present invention is implemented.

FIG. 2 is a normalized vibration response frequency spectrum hs obtained when the steel surface is hit with two types of strong and weak hitting strengths.
(F), hw (f) and the difference processing result h2 (f)
FIG. 4 is a spectrum distribution diagram showing an example of the above.

FIG. 3 shows an example of vibration response frequency spectra ys (f) and yw (f) obtained when the steel surface is hit with two types of high and low hitting strengths, and a difference processing result h2 (f). It is a spectrum distribution diagram shown.

FIG. 4 is a schematic diagram of a measurement result by a core sample.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Iron skin 2 Stamp material 3 Brick 4 Hammer 5 Impact tip 6 Impact strength meter 7 Vibration sensor 9 Filter (band-pass filter or low-pass filter) 10 Frequency analyzer 11 Signal processor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01B 17/00-17/04 G01N 29/00-29/28

Claims (3)

(57) [Claims] 1. A method for measuring the thickness of a refractory stretched over an inner surface of a steel shell from a resonance frequency component obtained when an elastic wave is propagated, wherein the vibration is applied to the steel shell, and then the vibration is applied to the steel shell. Response from vibration to steel or steel and stamp
A method for measuring the thickness of a refractory using elastic waves, comprising: measuring a vibration response frequency spectrum from which a vibration response signal of a material is removed, and calculating a thickness of the refractory from a peak frequency of the vibration response frequency spectrum. 2. A method according to claim 1, wherein a plurality of vibrations having different excitation intensities are applied to the steel, and a vibration response frequency spectrum corresponding to the plurality of excitation intensities is measured. The method for measuring the thickness of a refractory using elastic waves according to claim 1, wherein a difference process is performed on the refractory, and a thickness of the refractory is calculated from a peak frequency of a difference frequency spectrum obtained by the difference process. 3. The method according to claim 1, wherein the vibration response frequency spectrum is normalized by an excitation frequency spectrum applied to the steel.