JPH05312723A - Measuring method for alloying rate in continuous plating and alloying line for steel plate - Google Patents

Abstract

PURPOSE:To measure the alloying rate of the surface layer of a steel plate with a high accuracy and stably. CONSTITUTION:A far-infrared radiation is employed as alight applied for the measurement of the alloying rate of a steel plate. In a steel plate continuous plating and alloying line in which the steel plate is continuously plated and then subjected to an alloying treatment, a light from a visible light source 4 is diffused by a diffusion plate such as a frosted glass plate 8 and the diffused light 9 is applied to the steel plate 1 after the alloying treatment. Reflected light 10 and 11 from the steel plate 1 are detected by at least two light intensity detectors 5A and 5B at positions having different reflective angles to obtain respective reflected light intensities L1 and L2. The alloying rate is measured from the intensity ratio lambda=L2/L1. With this constitution, the reflected light intensity ratio lambda which is a univalent function of the iron concentration (alloying rate) of the steel plate surface and has the proportional relation with it can be obtained in a short time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the degree of alloying in a steel sheet continuous plating alloying line, and in particular, after continuously plating a steel sheet with zinc plating or Al plating, Continuous plating of steel sheet that is subjected to an alloying treatment by heating in an alloying furnace to cause the alloying of the plating components and the iron content in the steel sheet In the alloying line, the degree of alloying of the steel sheet immediately after the alloying treatment, that is, plating The present invention relates to an alloying degree measuring method for continuously measuring the amount of iron [Fe (%)] in a layer and its distribution (hereinafter referred to as alloying degree) online.

[0002]

2. Description of the Related Art Galvanized steel sheets, such as galvanized steel sheets, are products having improved weather resistance against rust and have been used in many applications including those for automobiles in recent years. However, when this type of plated steel sheet is subjected to bending and deep drawing in press working or the like, peeling easily occurs between the steel sheet as a base material and the plating layer, and the workability is poor. This is because the steel plate and the plating layer are divided into two layers in a step shape when the steel plate is viewed in the cross-sectional direction. Therefore, as a means of improving the workability,
It is said that it is desirable to form an alloy layer in which a clear boundary does not exist by gradually decreasing the iron component from the base metal toward the plating surface layer and gradually increasing the plating component.
For that purpose, it is good to diffuse a large amount of iron components to the plating surface.

However, when the degree of diffusion of the iron component is too high,
Since there is a problem that workability and surface quality are deteriorated, the iron concentration naturally has a limit. According to the iron concentration distribution curve in the plating layer shown in FIG. 6, the curve shows poor weldability and the curve shows poor weldability. Both weldability and workability are good, and the curve shows poor workability. From the above, it is considered appropriate that the iron concentration in the plating surface layer is 9 to 11%.

By the way, when measuring the iron concentration in the alloy layer, it is desirable to continuously perform it online. The alloying furnace part of the continuous plating line is schematically shown in FIG. 3. As a method of measuring the alloying degree online so far, an X-ray diffraction method is used immediately after the alloying furnace 2 at a position P indicated by a triangle. Alternatively, it is generally performed by a laser light scattering method. The former is to estimate the alloying degree from the intensity of several diffracted X-rays specified from the crystal structure of the alloy formed in the plating surface layer, and the latter is to streak laser light as shown in FIG. The detection principle is that the surface of the plated steel plate 1 is irradiated with 12 and the scattered light received by the camera 13 changes depending on the iron concentration.

[0005]

However, in the measurement by the conventional laser light scattering method, the relationship between the alloying degree represented by the iron concentration and the scattered light is a divalent function as shown in FIG. The alloying degree cannot be uniquely determined from the scattered light intensity. This is reported by many literatures, and the cause is explained as follows. That is, when the iron concentration in the surface layer portion is low, most of the laser light is reflected in the specular reflection direction because the surface is, for example, zinc and does not scatter much to the detector side, but the iron concentration (%) is as shown in FIG.
At point A, the Fe particles start to float on the surface layer and the surface becomes rough, and the scattered light intensity increases, and
It becomes the maximum at the point. Further, when the iron concentration (%) is increased, the surface layer portion is filled with Fe particles, the surface roughness is smoothed to some extent, and the scattered light intensity is reduced to point C.

FIG. 9 shows distribution characteristics of scattered light generated when the steel sheet is irradiated with beam-like light. According to FIG. 9, a direction symmetrical to the incident light with respect to the normal line from the surface of the plated steel sheet. Shows a reflection intensity of a size, while a direction of which the angle is deviated by θ shows a reflection intensity of b size. Such characteristics depend on the surface roughness of the plated steel sheet. When the laser light having a strong directivity is used as the irradiation light, the distribution characteristic of the diffused light changes extremely every moment due to the roughness change of a very small part of the surface of the plated steel sheet. Figure 10 shows (1)-
It is shown that it changes with (3). When laser light is used in such a state, the changing states of (1) to (3) appear alternately and the output is not stable.

As described above, in the conventional measuring method by the laser light scattering method, the alloying degree [Fe (%)] cannot be determined only from the scattered light intensity when the beam-like light is irradiated. In addition, there is a drawback that the measured values vary considerably even if the smoothing process is performed due to being greatly influenced by the minute unevenness of the steel sheet by using the laser beam having a high degree of focusing.

On the other hand, the conventional measuring method by the X-ray diffraction method has the same problems as those by the laser light scattering method.

The present invention has been made in order to solve such problems, and an object of the present invention is to easily obtain a scattered light intensity proportional to the iron concentration on the surface of a steel sheet. By providing the detected value as a monovalent function with respect to the alloying degree, it is an object of the present invention to provide a novel method for measuring the alloying degree of a steel sheet that can easily realize highly accurate measurement.

[0010]

The present invention has the following constitution in order to achieve the above object. That is, the invention according to claim 1 (hereinafter referred to as the first invention), after continuously plating the steel sheet, in the continuous plating alloying line of the steel sheet to be alloyed, to the steel sheet immediately after the alloying treatment,
Irradiating diffused light obtained by diffusing light from a visible light source with a diffusion plate, receiving reflected light from a steel plate at positions with different reflection angles by at least two light intensity detectors, and obtaining reflected light intensities, It is a method for measuring the degree of alloying in a continuous plating alloying line for steel plates, which is characterized by measuring the degree of alloying from the strength ratios thereof.

The invention according to claim 2 (hereinafter referred to as the second invention) has a wavelength of 5 μm or more for the steel sheet after the alloying treatment in the continuous plating alloying line of the steel sheet to be alloyed after the steel sheet is continuously plated. Long wavelength infrared and wavelength 0.5 ~
Irradiation with 1 μm visible light or near-infrared rays, the intensity of scattered light reflected from the steel sheet is measured, and the relational expression between the scattered light intensity and the previously determined scattered light intensity and alloying degree. And a degree of alloying of the steel sheet after the alloying treatment is obtained from the above.

The invention according to claim 3 (hereinafter referred to as the third invention) has a wavelength of 7 μm or more on the steel sheet after the alloying treatment in the continuous plating alloying line of the steel sheet which is continuously plated and then alloyed. Is irradiated with two types of long-wavelength infrared rays with different wavelengths, the intensity of the scattered light reflected from the steel sheet is measured, and the intensity of the scattered light and the intensity of the scattered light and the alloying degree that have been obtained in advance are measured. Is used to determine the degree of alloying of the steel sheet after the alloying treatment, and a method for measuring the degree of alloying in a continuous plating alloying line for a steel sheet.

[0013]

According to the first aspect of the invention, the steel sheet immediately after the alloying treatment is
The diffused light obtained by diffusing the light from the visible light source by the diffuser plate is irradiated, the reflected light from the steel plate is received by at least two light intensity detectors, and the reflected light intensities are obtained respectively. , Scattered light intensity), it is possible to obtain a measured value of a monovalent function that is approximately proportional to the iron concentration on the steel sheet surface. This is
This is apparent from the following description.

That is, as shown in the principle diagram of FIG. 2, when light from a light source is applied to a plated steel sheet as diffused light by a diffuser plate made of frosted glass or the like, the scattered light distribution generated by the reflection is microscopically on the surface of the steel sheet. A stable and stable product can be obtained without being affected by the changing unevenness. Next, when the materials with different alloying degrees [Fe (%)] under such stable conditions are scattered and reflected, and their diffusion distribution characteristics are examined, the results shown in Fig. 4 are obtained. Be done. In FIG. 4, the alloying degree progresses from (1) to (3). here,
(A) shows the incident light, and (b) shows the direction of the reflected light corresponding to the law of reflection with respect to the normal. (F) is the direction for observing scattered light, and the usual (B) direction is too strong, so select the (F) direction that is weak light.

However, at the conventional observation position only from one direction, the intensity of scattered light is increased as the alloying progresses.
After increasing from (c) to (d), it will return to (e) this time. FIG. 8 shows this phenomenon in another form, where the horizontal axis represents the iron concentration [Fe (%)] and the vertical axis represents the scattered light intensity. In other words, the alloying degree is proportional to the scattered light intensity up to a certain range, but the scattered light intensity decreases when the alloying degree is more than that. This means that it is not proportional to the scattered light intensity.

By the way, in FIG. 4, the direction (b) is slightly deviated from this direction even if it is not suitable as the observation position because the scattered light intensity is too strong and its fluctuation is large.
It is relatively stable in the direction of (g). Therefore, when the ratio (λ) of the scattered light intensity L _{2 in} the (f) direction to the scattered light intensity L _{1 in} the (g) direction is taken, the value for Fe (%) is as shown in FIG. become. As you can see from this figure, Fe
In the region where (%) is high, it becomes a little saturated, but λ is Fe
Since it is a monovalent function for (%), Fe (%) can be uniquely estimated from λ. Also, the fluctuation is much smaller than that measured only in the (f) direction.
Further, by observing the width direction of the plate in this manner, it is possible to observe the entire width and the unevenness. Furthermore,
In the measurement by the conventional laser light scattering method, the measurement accuracy is significantly reduced due to the vibration of the steel sheet, but the first invention also has an advantage that the influence of the vibration of the steel sheet is reduced because the diffused light is used.

Next, the operation of the second invention will be described. In the first invention, at least two light intensity detectors need to be spatially accurately arranged, the device is complicated, and since the light is in the visible light region, the light from the surroundings (stray light) However, in the second invention, these problems can be alleviated. That is, since long-wavelength infrared rays and near-infrared rays (or visible rays) are used as the irradiation light on the steel sheet immediately after the alloying treatment, it is less likely to be affected by stray light due to surrounding illumination. Further, since the intensity of the scattered light from the steel plate is measured, it is not necessary to strictly arrange the measuring device, and the device can be simple.

Further, in the second aspect of the invention, the use of the infrared rays in the long wavelength range makes it less likely to be affected by the surface roughness of the steel sheet, thus improving the accuracy. That is, according to Beckman's theory of scattering, if there is a certain relation between the typical dimension h of the rough surface and λ, the interference in the rough surface increases and the scattering becomes resonantly large. It is known. The actual surface of the steel sheet does not have a regular array of protrusions but has a random roughness, so the scattering changes continuously with respect to the wavelength. Therefore, the reaction to the degree of alloying can be made clearer by using long-wavelength infrared light having a longer wavelength than visible light used in the first invention. Fig. 11 shows the result of experimentally proving this by Fourier spectroscopy. In the visible light region, the scattered light intensity ratio (ratio of scattered light intensity when the irradiation light is 100) is low,
The difference due to the degree of alloying is small, but the wavenumber is 1000 cm ^-1 (: wavelength 10 μ
At around m), the scattered light intensity ratio increases rapidly.

It is apparent from the following explanation that the alloying degree can be obtained by the method of the second invention. That is, FIG. 12 is a graph obtained by superposing FIG. 11 and FIG. 8 on a graph, and as can be seen from this figure, the alloying degree can be easily obtained from the scattered light intensity. Specifically, the scattered light intensity at the wavelength λ ₁ in the visible light region is
I _1, I ₂ a scattered light intensity at a wavelength lambda ₂ in the long wavelength region infrared region, when the alloying degree to _{Fe%, I 1 = f 1} (Fe%), I 2 =
It becomes f ₂ (Fe%). Where f ₁ and f ₂ are Fe% and I ₁ ,
It means a function that shows the relationship with I ₂ . Fe% can be obtained by solving these simultaneous equations. That is, the degree of alloying can be obtained by irradiating long-wavelength infrared and visible light or near infrared, measuring the intensity of scattered light from the steel sheet, substituting the measured values, and solving the simultaneous equations. However, when long-wavelength infrared rays are used as the irradiation light, the functions f ₁ and f ₂ have similar shapes, and thus it is difficult to obtain Fe% by such a method.

In the second invention, the wavelength of the infrared rays in the long wavelength range to be irradiated is set to 5 μm or more because if it is less than 5 μm, the scattering intensity from the steel sheet surface is weak and the correspondence with the surface iron concentration is poor. On the other hand, the wavelength of visible light or near-infrared rays to be irradiated is 0.5 to 1 μm, which is 0.5 μm.
This is because if it is less than m 2, the scattered light distribution becomes too narrow, and the absorption in the optical path becomes large, and if it exceeds 1 μm, the scattered light intensity falls again.

Next, the operation of the third invention will be described. Since long-wavelength infrared rays are used as irradiation light, it is not easily affected by stray light.Because the intensity of scattered light from the steel plate is measured, it is not necessary to strictly arrange the measuring instrument and the device is also Easy and good. In addition, due to the use of the long-wavelength infrared ray, for the same reason as in the case of the second invention,
It is less affected by the surface roughness of the steel plate, resulting in higher accuracy.

It will be apparent from the following explanation that the alloying degree can be obtained by the method of the third invention. That is, as can be seen from FIG. 12, although the function form is different from the visible light region, the alloying degree cannot be uniquely obtained from the scattered light intensity, but for example, the change ΔI in the scattered light intensity at wavelengths 10 and 12 μm is Along the ordinate, the result as shown in FIG. 13 is obtained. Since this is a monovalent function that uniformly increases with respect to Fe%, Fe% can be uniquely determined from ΔI. Therefore, when two types of long-wavelength infrared rays having different wavelengths are irradiated and the intensity of scattered light from the steel sheet is measured, the measured values and the relational expression between the scattered light intensity and the degree of alloying obtained in advance are used. The degree of alloying can be determined.

In the third invention, the wavelengths of the two kinds of long-wavelength infrared rays having different wavelengths to be irradiated are set to 7 μm or more. When the length is less than 7 μm, the scattering due to the surface roughness is large and the increase rate of scattered light with respect to the wavelength is large. Because it will be.

[0024]

Embodiments will be described below with reference to the drawings. (Embodiment 1) Embodiment 1 is an embodiment of the first invention. The measuring device according to the embodiment is installed at a position as illustrated in FIG. 3, that is, just above the alloying furnace 2 as in the conventional case, but may be installed at a slightly rear position. FIG. 1 shows the first embodiment.
FIG. 3 is a schematic structural diagram of the device according to FIG. 1, showing the measurement system and the signal system for the one side on the right side, but the same is true for the one side on the left side. As the light source 4, two reflector-type incandescent light bulbs 60W are attached in the plate width direction, and a frosted glass 8 is arranged on the front surface as a diffusion plate for diffusing light, whereby a light source with a diffusion plate is formed. The light source with the diffusion plate has an angle with respect to the plated steel plate 1, that is, the angle of the irradiation optical axis is 60 °.
It is provided at a position of 700 to 900 mm from the plated steel plate 1 at ~ 70 °. A constant voltage is supplied to the incandescent bulb. Two light intensity detectors 5A and 5B in combination with this light source with diffuser
Are placed.

One light intensity detector 5A is provided at a position of 0 ° to 5 ° with respect to the normal line of the plated steel sheet 1, and the other light intensity detector 5B is similarly provided at a position of 20 ° to 25 °. .. It is desirable that the angle between these two light intensity detectors 5A and 5B be open around 20 °. The outputs L ₁ , L ₂ from both detectors 5A, 5B are applied to a converter 6 in which a λ = L ₂ / L ₁ is calculated through a preamplifier.

When measuring one point in the width direction of the plated steel plate 1, a detector such as a photodiode or a Si cell may be used, but when measuring the distribution in the width direction, a solid-state image sensor or A one-dimensionally observable one such as a photodiode array is used. In the case of a solid-state image sensor, such as a CCD element, in order to have sensitivity in the visible range,
It is necessary to install an infrared cut filter. Whether it is a single point or multi-point measurement in the width direction, it is better to attach a lens to the front surface of the detector in order to narrow the field of view to some extent.

In this way, the signal obtained by the calculation is output as a control signal to the external display 7 or programmable controller. The display device 7 of the embodiment uses a bar graph display device and can display information in the width direction.

In the embodiment of FIG. 1, stray light from the surroundings is expected to affect the measurement. Therefore, it is necessary to sufficiently remove stray light by a cover or the like to reduce noise. If this shield cannot be obtained sufficiently, it is desirable to attach an optical chopper to the front surface of the light source and the diffusing surface to irradiate light intermittently and perform DC detection on the detector side.

(Embodiment 2) Embodiment 2 is an embodiment of the third invention. As the infrared rays to be radiated, the output of a spectroscope may be used or a filter may be used. However, since the amount of light is generally insufficient, an incandescent light bulb is lit at a low voltage by a stabilized power source as shown in FIG. This light has a wide wavelength range, and is expanded so that it spreads in the width direction of the steel plate by an unequal magnification lens or cylindrical lens immediately after the lamp, passes through the diffuser plate, and further passes through a rotary chopper to the steel plate. Is irradiated. This chopper is interlocked with the detector 14 and is synchronously detected. The situation is shown in FIG. The steel sheet has a far infrared ray because it has a temperature of several hundred degrees Celsius even after it leaves the alloying furnace and the jet cooler. When the chopper is open, the detector detects the sum of the scattered light from the irradiation light and the infrared rays emitted from the steel sheet, and when the chopper is closed, only the infrared light emitted from the steel sheet is detected. For example, only the scattered light component can be detected. still,
The diffusion plate may not be used.

The irradiated light is scattered on the surface of the steel plate and reaches the filter 16 by the collimator 15. The filter is for transmitting wavelengths λ ₁ and λ ₂ , and an interference filter is suitable. After that, it is detected by an infrared detector. This detector uses a thermopile or a compound semiconductor such as HgCdTe, but these detectors are not one-dimensional or two-dimensional array sensors, so a mechanism that mechanically scans in the width direction is used to detect the plate width direction. Is required. Alternatively,
The degree of alloying in the width direction may be measured using an infrared intensifier (a part that receives infrared rays emits visible light and detects infrared rays). These devices can be installed at the positions shown in FIG.

Although the detection of scattered light has been described above, similar results can be obtained by using reflected light. However, in a method in which the detector and the light source are opposed to the steel plate at an angle (for example, the method shown in FIG. 17), since the influence of the vibration of the plate is applied, the detector is opposed to the steel plate at a right angle. A method of irradiating light from behind (for example, the method shown in FIG. 18) may be used.

[0032]

As described above, according to the first aspect of the present invention, the steel plate immediately after the alloying treatment in the continuous plating alloying line for the steel plate is irradiated with the diffused light in which the light from the visible light source is diffused by the diffuser plate. Since this is a method of measuring the scattered reflected light, the influence of the surface roughness of the steel sheet is extremely small, and stable scattered reflected light intensity can be obtained. Furthermore, by a method in which the reflected light from the steel plate is received by at least two light intensity detectors at positions with different reflection angles, the reflected light intensities are obtained, and the alloying degree is measured from the intensity ratio of the scattered reflected light. Therefore, the iron concentration on the steel plate surface (that is,
The intensity ratio of scattered reflected light having a monovalent function with respect to the alloying degree) can be obtained in a short time. Therefore, it becomes possible to continuously and accurately measure the alloying degree of the steel sheet surface layer online. Further, in the measurement by the conventional laser light scattering method, the measurement accuracy is remarkably lowered due to the vibration of the steel sheet, but in the first invention, there is an advantage that the influence of the vibration of the steel sheet is reduced because the diffused light is used.

Further, according to the second invention or the third invention, it is more difficult to be affected by the light (stray light) from the surroundings than in the case of the first invention, so that the accuracy is high and the space of the measuring instrument is high. There is an advantage that the strictness of the physical arrangement becomes gentle and the device becomes simple and easy.

[Brief description of drawings]

FIG. 1 is a schematic structural diagram of an apparatus according to a first embodiment.

FIG. 2 is a principle diagram illustrating a method according to the first invention.

FIG. 3 is a schematic structural diagram of a continuous plating alloying line.

FIG. 4 is a diagram showing a reflected light diffusion distribution when a steel sheet is irradiated with diffused light.

FIG. 5 is a diagram showing the relationship between the iron concentration and the scattered light intensity ratio λ for explaining the method according to the first invention.

FIG. 6 is an iron concentration distribution diagram in a plated layer of a plated steel sheet.

FIG. 7 is a principle diagram of iron concentration measurement in a conventional alloy layer.

FIG. 8 is a diagram showing the relationship between iron concentration and scattered light intensity in conventional iron concentration measurement.

FIG. 9 is a distribution characteristic diagram of scattered light generated when a steel sheet is irradiated with beam-shaped light.

FIG. 10 is a distribution characteristic diagram of diffused light generated when a steel sheet is irradiated with beam-shaped light.

FIG. 11 is a diagram showing the relationship between the wave number of irradiation light and the scattered light intensity ratio obtained by experiments.

FIG. 12 is a diagram showing the relationship between the degree of alloying and the scattered light intensity obtained from FIGS. 8 and 11.

FIG. 13 is a diagram showing the relationship between the degree of alloying and the change ΔI in scattered light intensity at wavelengths of 10 and 12 μm.

FIG. 14 is a schematic structural diagram of an apparatus according to a second embodiment.

FIG. 15 is a diagram showing a change over time of a detection signal when a chopper is used.

FIG. 16 is a diagram illustrating an example of an installation position of the device according to the second embodiment.

FIG. 17 is a diagram for explaining an arrangement relationship between a reflected light detector and a light source.

FIG. 18 is a diagram for explaining an arrangement relationship between a reflected light detector and a light source.

[Explanation of symbols]

1--plated steel plate, 2--alloying furnace, 3--plating pot, 4
--Light source, 5A--Light intensity detector, 5B--Light intensity detector, 6--Converter, 7--Display, 8--Frosted glass, 12--Laser light, 13
--Camera, 14--Detector, 15--Collimator, 16--Filter, 17--Stabilized power supply, 18--Lamp, 19--Lens, 20--Diffuser, 21--Chopper, 22- -Illuminated light, 23--scattered light, 24-- calculator.

Claims (3)

[Claims] 1. Continuous plating of a steel sheet, and then continuous plating of the steel sheet to be alloyed A diffused light obtained by diffusing light from a visible light source by a diffusion plate is applied to the steel sheet immediately after the alloying treatment in an alloying line. Irradiation, reflected light from the steel plate is received by at least two light intensity detectors at positions with different reflection angles, the reflected light intensities are respectively obtained, and the alloying degree is measured from the intensity ratio thereof. A method for measuring the degree of alloying on a continuous plating alloying line for steel sheets. 2. A continuous plating of a steel sheet, which is continuously plated, and a continuous plating of a steel sheet to be alloyed.
The intensity of scattered light reflected from the steel sheet is measured by irradiating with 0.5 to 1 μm of visible light or near-infrared light, and the intensity of the scattered light and the intensity of scattered light and the degree of alloying obtained in advance are measured. A method for measuring the degree of alloying in a continuous plating alloying line of a steel sheet, characterized in that the degree of alloying of the steel sheet after the alloying treatment is obtained from a relational expression. 3. Continuous plating of a steel sheet, followed by continuous plating of the steel sheet to be alloyed. The alloyed steel sheet is irradiated with two types of long-wavelength infrared rays having a wavelength of 7 μm or more and different wavelengths. Then, the intensity of the scattered light reflected from the steel sheet is measured, and the intensity of the scattered light, and the relational expression between the scattered light intensity and the degree of alloying obtained in advance of the steel sheet after the alloying treatment. A method for measuring the degree of alloying in a continuous plating alloying line for steel plates, which comprises determining the degree of alloying.