JPS6396545A - Method and device for on-line measuring metallic surface film in atmospheric air - Google Patents

Abstract

PURPOSE:To suppress a variation of the photo-electron detection efficiency by keeping constant a distance between a measurement tip part consisting of an ultraviolet ray leading-in system, and a detector for measuring the intensity of a photo-electron, and the surface of a sample. CONSTITUTION:An ultraviolet ray leading-in system 2 using an optical fiber is provided in order to project a light beam from an ultraviolet ray light source 3, to a metallic sheet sample 9, and fixed to a measuring chamber 7 and a detector 1. The detector 1 is also fixed to the measuring chamber 7. The measuring chamber 7 in which the part opposed to the sample 9 is brought into contact with the surface of the metallic sample 9 through a roller, 4, in its opening, part, and can move in accordance with the up-and-down variation of the sample 9 by suspending it from a rack base 10 by a spring 8. A holding roller 6 suppresses the up-down variation of the sample 9, and supports a load of the measuring chamber.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method and apparatus for measuring in the atmosphere the thickness or coverage of a film on the surface of a metal sheet that is continuously passing through a process.

(Conventional technology) Fluorescence X-ray analysis (XRF
) has already been put into practical use.

However, this method is only used for relatively thick layers with a film thickness of about several μm. The thickness of the oxide film on the metal surface depends on the oxidation conditions, but it is generally on the order of tens to hundreds of years. When analyzing films with this thickness, Auger electron spectroscopy (AES), photoelectron spectroscopy is used. Law (ESC
A), surface analysis instruments such as glow discharge emission spectroscopy (GDS) are often used. However, since all of these methods use a vacuum device, it is necessary to cut out a small sample piece and insert it into the device for analysis.

In the metal manufacturing industry, non-destructive continuous analysis (without cutting out test pieces from thin metal sheets or other products during the manufacturing process) is used to provide quick feedback for the purpose of quality control, yield improvement, etc. online analysis) is desirable. In this respect, the aforementioned AES, ESCA, G
DS has difficulties in applying to online analysis.

On the other hand, methods that can be used to measure the thickness of the surface film of metal materials in the atmosphere include ultraviolet excitation and a slow electron atmospheric counting device (Japanese Patent Publication No. 59-9874).
A method that combines the following is known (RIKEN KEIKI ■Surface analyzer model AC-1 catalog (see attached reference material)). This method uses a gas discharge tube as a light source to monochromate ultraviolet rays using a spectrometer, and then irradiates the surface of the sample with the monochromatic ultraviolet rays through an ultraviolet introducing system consisting of an optical fiber and its coating. By emitting photoelectrons from the base and measuring their intensity, the emission blocking ability of the film on the outermost surface, that is, the thickness or coverage of the film, can be determined. More specifically, the thickness of the coating is measured as follows.

FIG. 7 is a diagram showing information obtained by the surface analyzer AC-1. The incident ultraviolet light is made monochromatic by a spectrometer and its energy is scanned. The horizontal axis in Figure 7 represents the energy A/-1f'- of this incident ultraviolet rays, but if the sample is irradiated with long wavelength, that is, low energy ultraviolet rays, a certain energy threshold will be reached as shown in the figure. Photoelectron emission begins when . This threshold value is called the work function, and the square root of the amount of photoelectrons emitted after the work function has a nearly linear relationship with the energy value of the incident ultraviolet rays, and the slope of that straight line represents the emission blocking ability of the coating. The thicker the coating or the greater the coverage of the coating, the smaller the slope. This measurement method determines the surface coating thickness or coverage rate from the slope of this straight line.

However, there are the following problems when applying this device to online measurements.

That is, in this known device that combines ultraviolet excitation and a slow electron atmospheric counting device, the counting rate fluctuates depending on the vertical positional fluctuation of the sample relative to the combination of the ultraviolet introduction system and the detector. There are three possible reasons for this:

(,) As shown in Fig. 5, this device irradiates the sample 25 with monochromatic ultraviolet rays 24 from an oblique direction, so if the sample moves up and down, the center of the ultraviolet irradiation position and the measurement position will change. It shifts.

(b) The longer the distance from the sample to the detector, the more difficult it becomes for emitted photoelectrons to enter the detector.

(e) The longer the distance from the tip of the ultraviolet introduction system to the sample, the more attenuation of ultraviolet light occurs.

Therefore, even if this method is applied to a sample passing through the production process, it is difficult to measure with high accuracy.

Further, the measurement principle of this detector is based on the gas discharge phenomenon, and the response speed is slow depending on the discharge extinction time, so a measurement time of about several seconds is required. Therefore, when the moving speed of the process is fast, the spatial resolution in the moving direction becomes insufficient.

(Problems to be Solved by the Invention) In view of the above-mentioned circumstances, the present invention aims to effectively use an ultraviolet-excited slow photoelectron atmospheric counting device to apply it to online measurement of a metal sample surface film.

(Means and effects for solving the problems) The present invention has the following features:
A surface analysis method that measures the film thickness or coverage rate on the sample surface by irradiating ultraviolet rays onto a metal thin plate sample that is passing through the production process and measuring the intensity of photoelectrons excited and emitted from the sample. An online measurement method for metal surface coatings in the atmosphere, characterized by suppressing fluctuations in photoelectron detection efficiency by keeping the distance between the measurement tip consisting of a system and a detector for measuring photoelectron intensity and the sample surface constant. , and a measurement tip consisting of an ultraviolet light source, an ultraviolet introduction system that guides the ultraviolet light from the light source into the measurement chamber and irradiates the thin metal sample, and a detector that measures the intensity of photoelectrons excited and emitted from the sample by the ultraviolet irradiation. and a measurement chamber that houses the measurement tip and is open at the part facing the sample and has a structure in which the inside can be replaced with atmospheric gas, and a measurement chamber that maintains a constant distance between the measurement tip and the surface of the thin metal sample. This is an on-line measuring device for metal surface coatings in the atmosphere, characterized by comprising a ninth holding mechanism for holding the metal surface film in the atmosphere.

The structure of the present invention will now be described by explaining the means taken to solve the above problems along with their effects.

Known devices were originally designed on the premise of measuring a stationary sample. Therefore, when applying this to a sample that is moving through the production process, it is important to minimize the relative fluctuation in the vertical direction. in this case,
It is not necessary to absolutely fix the vertical position of the sample, and it is sufficient that the distance between the entrance of the detector and the sample and the distance between the ultraviolet introduction system and the sample are kept constant.

In the present invention, the detector and the ultraviolet introduction system are fixed to the same holder, and this holder is held at a constant distance from the sample surface. By keeping the distance to the sample constant, fluctuations in detection efficiency can be suppressed.

A gas discharge tube or laser is used as the ultraviolet light source.
This is to irradiate the surface of a thin metal sample to be measured with ultraviolet light to excite and emit photoelectrons. The ultraviolet introduction system is made of an optical fiber or vacuum waveguide, and its tip is fixed to a holder together with the detector through the measurement chamber, so that the ultraviolet irradiation position is always kept constant relative to the sample and detector. be able to. (9) When multiple detectors are used, the ultraviolet light from one light source is distributed to each detector.

The measurement chamber, which houses the measurement tip and is open at the part facing the sample, serves as a medium to connect the measurement tip and the holder, and at the same time, the space between the measurement tip and the sample is used for measurement. It is provided for replacing with atmospheric gas.

Here, the measurement atmosphere gas needs to contain oxygen, which serves as a carrier for photoelectrons emitted from the sample surface, and high-purity dry air or a mixed gas of oxygen and nitrogen is used.

The inside of the detector is also replaced with the same gas as the inside of the measurement chamber, but in the measurement chamber, the gas is replaced by flowing the measurement gas over the sample surface in advance, and the condition of the sample surface is kept constant, and the humidity and humidity at the production site are replaced. This is essential for obtaining stable measurement values that are unaffected by the environment such as dust.

Next, the content of the present invention will be explained in detail based on the drawings.

(Example) An example of an apparatus for carrying out the present invention is shown in FIG. The ultraviolet introduction system 2 using an optical fiber irradiates the metal thin plate sample 9 with light from the ultraviolet light source 3.
and fixed to the detector 1. The detector 1 is also fixed in the measurement chamber 7, and as a result, the positions of the detector 1, the ultraviolet ray introduction system 2, and the king of the measurement chamber 7 are relatively fixed.

In this example, the light source is a 150W water-cooled deuterium rung, the spectrometer is a diffraction grating spectrometer using a single spectroscopic crystal, and the ultraviolet introduction system is a 4flφ optical fiber made of quartz glass with a core diameter of 200 μm. The detector used was one for Riken Keiki's AC-1 type, and the measurement atmosphere gas used was high-purity dry air. However, a vacuum waveguide may be used instead of the optical 7-eyeper, and a xenon lamp, an Equinox laser, or an argon laser may be used instead of the heavy water lamp. Regarding the spectroscope, it can be replaced with a spectral filter or can be omitted.

The reason is as follows.

By monochromating the light from an ultraviolet light source using a spectrometer, scanning the wavelength of the incident ultraviolet light from long wavelength to short wavelength, and irradiating the sample with light in order of low energy, information as shown in Figure 7 can be obtained. I have already mentioned this. In order to analyze unknown samples whose composition and structure are completely unknown and which are dangerous, it is important to scan the energy of the incident ultraviolet rays and find the work function in this way.

On the other hand, when regularly measuring the film thickness or coverage of a sample flowing through a process, it is not necessarily necessary to scan the energy of the incident light. For example, if the diffraction grating of a spectroscope is fixed and only ultraviolet rays of a certain energy are irradiated, or if monochromatic laser light is used as a light source, the desired information can be obtained in a shorter time. Alternatively, a filter may be used instead of a spectrometer. Furthermore, it is necessary to fully understand in advance what kind of sample the sample is, what kind of abnormalities are likely to occur in what places, and also ensure that the behavior of photoelectron emission from normal parts does not change drastically depending on the location. , the light from the light source may be directly irradiated onto the sample without being monochromatic. In this case, since light with energy greater than the work function simultaneously excites and releases photoelectrons, the signal detected here represents the integral value of the straight line rising after the work function in FIG. Therefore, the signal intensity increases compared to when the incident light is made monochromatic, and the measurement time can be further shortened. Furthermore, since the intensity of the incident light increases, there is also the advantage that a plurality of detectors can be installed for one ultraviolet introduction system.

The measurement chamber 7, which has an open portion facing the sample, is in contact with the surface of a thin metal plate sample 9 via a roller 4 that rotates with the movement of the sample at the open portion, and is suspended from a mount 10 by a spring 8. This allows it to move in response to vertical fluctuations of the metal thin plate sample 9. The holding ring 6 is used to suppress vertical movement of the sample and support the load of the measurement chamber. In the present invention, these mechanisms allow the distance between the detector and the sample surface and the distance between the tip of the ultraviolet introduction system and the sample surface to be kept within ±1tj1. The basis for setting this distance within ±lzx is as follows.

The above three points were considered to be the reason why the counting rate changes due to the relative vertical fluctuation of the sample.

Of these, (a) and (b) are considered to have a large contribution, but these are ultimately reduced to the contribution of changes in the detected solid angle.

Therefore, Fig. 6 shows how the detected solid angle changes with respect to the displacement Δ2 of the tip and sample in Fig. 5. Δ
It can be seen that 2 needs to be within ±1 positive. Also,
As can be seen from this figure, even if the incident angle θ of the ultraviolet rays is changed within the range of about 30'' to 90° when Δ2 is within the range of ±1, the change in the detected solid angle with respect to Δ2 will vary depending on θ. is almost independent.

Therefore, by using the holding mechanism according to the present invention to suppress the vertical movement of the sample within ±1 blade snow removal, stable measurement results can be obtained even if the incident angle of the ultraviolet rays is selected with some degree of freedom.

In the manufacturing process of the galvanized steel sheet shown in FIG. 2, after passing through the pickling tank 11 and immediately before being immersed in the plating tank 13 in the measurement chamber 12, abnormal areas due to oil stains and scale left behind on the surface of the steel sheet. We conducted measurements to detect the

The analyzer based on the present invention is installed as shown in Figure 3 (al t (b)), and the film on the surface of the steel plate is measured while the plate is being passed. Figure 3(b) is a cross-sectional view seen from the parallel plane, and Figure 3(b) is a cross-sectional view seen from the normal force plane. By summing the signals from the instruments, we succeeded in increasing the counting rate per unit time and shortening the measurement time.

The ultraviolet introduction system 16 consists of an optical fiber and its coating,
The light from the ultraviolet light source 17 is branched to each detector, thereby making it possible to downsize the entire measurement chamber.

Pulley 19 and pulley holder 20 installed at the lower end of the detector
This is to keep the error in the distance between the steel plate 22 and the entrance of the detector 15 within ±1. The entire measurement chamber is fixed to a pedestal 21, and vertical vibrations of the steel plate can be suppressed by this holding mechanism and a holding roll 23 that supports the steel plate.

As for the spectroscope, it was not used in this example for the reasons already mentioned, and the light from the ultraviolet light source 17 was directly incident on the steel plate 22 through the ultraviolet introduction system 16.

Abnormal areas on the surface of the steel plate were detected under the above conditions.

The results are shown in Figure 4 (,). The vertical axis represents the counting rate that is the sum of the signals of 100 detectors, and a portion with a low counting rate indicates an abnormal portion of the steel plate. The horizontal axis represents the distance from the top of the coil calculated from the line speed.

From this result, it can be determined where in the coil the defective part is located.

The resolution in the horizontal axis direction depends on the measurement time per measurement point, the line speed, and the size of the detector. In the case of this example, the measurement time was 0.1 seconds, and the line speed was approximately 2 seconds.
m/sec, and the detector has a width of about 25cIIL, so in the end, the resolution depends on the width of the detector, which is about 25cIIL.
This means 1rL. Normally, the size of the defective part is about 3m in the direction of line movement, so
It can be said that the spatial resolution of this measurement is sufficient.

Next, FIG. 4(b) shows the results of measuring the thickness of carden stains on a steel plate using the same configuration as in FIG. 3.

In this example, the detectors arranged vertically and horizontally are divided into 20 rows of 5 detectors parallel to the direction of movement of the steel plate, the signal strength in each set is summed, and the signals from each set are detected independently. ing. This means that multi-channel measurement of 20 channels is being carried out. In FIG. 4(b), the horizontal axis indicates the width direction of the steel plate, the left vertical axis indicates the measured value of the number of photoelectrons, and the right vertical axis indicates the thickness of carden stain. From this result, car? It can be seen that the dirt is thicker at the nip than near the center in the width direction.

However, the thickness of the stain that can be measured is about 500X or less.

(Effects of the invention) By applying the method of the present invention to processing lines such as plating, process control of film thickness and dirt during processing can be greatly improved, resulting in a high level of stable product quality and improved product yield. can be achieved.

[Brief explanation of the drawing]

Figure 1 (a), (b) and Figure 3 (a), (
b) are all drawings showing the configuration of an apparatus according to an embodiment of the present invention, FIG. 2 is a drawing showing an example of the manufacturing process of an embodiment of the present invention, and FIG.
Figures (a) and (b) are diagrams showing the results of the examples, Figure 5 is a diagram showing an outline of a well-known device that combines ultraviolet excitation and a slow electron atmospheric counting device, and Figure 6 is a diagram showing the results of a sample. FIG. 7 is a diagram showing the relationship between the positional displacement (Δ2) and the detected solid angle, and is an explanatory diagram of the measurement principle. 1...Detector 2...Ultraviolet introduction system 3...
・Ultraviolet light source 4...Roller 5...Measurement gas inlet 6...Holding roll 7...Measurement chamber
8... Spring 9... Metal thin plate sample 10... Frame 1
1... Pickling tank 12... Measurement chamber 13... Plating tank 14... Winder 15... Detector
16... Ultraviolet introduction system 17... Ultraviolet light source 1
8...Measuring gas introduction Loe9...Pulley 20
... Pulley holder 21 ... Frame 22 ...
Steel plate 23... Holding roll 24... Ultraviolet rays 25.
・・Sample ``''-) Agent Teruo Taniyama -'' ′--] ・ , --J Figure 1 12: Jllll regular room (b) Figure 5 Figure 7 Human body [Kohei Ruki-(eV)

Claims (1)

[Claims] 1. A surface for measuring the film thickness or coverage on the sample surface by irradiating ultraviolet rays onto a metal thin plate sample passing through the production process and measuring the intensity of photoelectrons excited and emitted from the sample. An atmospheric analysis method characterized by suppressing fluctuations in photoelectron detection efficiency by maintaining a constant distance between the measurement tip, which consists of an ultraviolet introduction system and a detector that measures photoelectron intensity, and the sample surface. Online measurement method for metal surface coatings. 2. A measurement tip consisting of an ultraviolet light source, an ultraviolet introduction system that guides the ultraviolet light from the light source into the measurement chamber and irradiates the thin metal sample, and a detector that measures the intensity of photoelectrons excited and emitted from the sample by the ultraviolet irradiation; , a measurement chamber that houses the measurement tip, has an open portion facing the sample, and has a structure in which the inside can be replaced with atmospheric gas, and maintains a constant distance between the measurement tip and the surface of the thin metal sample. 1. An online measurement device for a metal surface film in the atmosphere, comprising a holding mechanism for