JPH02257045A - Method and device for measuring plated deposit of plated steel sheet and composition of plated film - Google Patents

Abstract

PURPOSE:To enhance measurement precision of both the plated deposit and composition of a plated film by making monochromatic X-rays incident on a standard sample and a material to be measured at the same angle of two kinds, calculating the intensity of fluorescent X-rays, utilizing a previously obtained theoretical expression in the same conditions and calculating the intensity of the theoretical X-rays. CONSTITUTION:When monochromatic X-rays of wavelengths lambda1, lambda2 are made incident into a plated steel sheet at the incident angles phi1, phi2, a theoretical calculation expression of the intensity of fluorescent X-rays in K-sequence of the aimed element for analysis in the measuring angles psi1, psi2 is obtained. Then a standard sample is utilized wherein both the plated deposit and the composition of a plated film are already known. The intensity of fluorescent X-rays is measured in the same conditions as the above-mentioned method. A conversion factor is obtained by which the measured value is converted into the theoretically calculated value on the basis of the theoretical expression. Then the intensity of fluorescent X-rays is measured in the same conditions for the plated steel plate to be measured. This measured intensity is converted into the theoretical intensity by utilizing the conversion factor. The theoretical intensity obtained by the theoretical calculation expression is most closely approached the converted theoretical intensity. The parameter in the theoretical calculation expression is made the plated deposit and the composition of the plated film of the material to be measured.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to the plating of a plated steel sheet (=1 coating amount and coating film composition are measured online).
-1 Method and apparatus for measuring coating weight and plating film composition, particularly effective for analysis when the plating film contains the same components as the underlying metal; Regarding the measuring device.

[Conventional technology]

Fluorescent X-ray analysis is used to measure the amount of plating deposited and the composition of the plating film on this type of plated steel sheet. This X-ray fluorescence analysis method can measure the amount of plating 471 and the composition of the plating film on-line for materials such as Zn-plated steel sheets and Zn-Ni-plated steel sheets where the plating film does not contain a base metal.

However, in recent years, ZN-RE alloy plated steel sheets have attracted attention for their excellent properties such as corrosion resistance and workability. Difficult to distinguish from fluorescent X-rays caused by Fe,
Furthermore, it is difficult to correlate the relationship between the fluorescent X-ray intensity, the amount of plating deposited, and the composition of the plating film, and it is difficult to analyze it online.

Therefore, the following two analysis methods have been proposed as methods for solving the above problems.

One of them is a Zn-Fe alloy plated steel plate, which has a large number of wavelengths. After irradiating so-called white X-rays, the first /l1ll constant angle at which fluorescent X-rays from the underlying metal of the plated steel plate are not substantially detected from the point of the X-ray penetration depth, and the fluorescent X-rays from the underlying metal. This is an on-line analysis method in which the intensity of fluorescent X-rays of the series I is measured at a second measurement angle that can detect the angle of 223
Publication No. 047).

The other method is to use absorption by the film to determine the coating amount from the diffraction
This is a method for determining the plating film composition from the diffraction X-ray intensity of one or two phases selected from alloy J, IJ and η phases.
(Japanese Patent Application Laid-open No. Sho GO-169553).

[Problem to be solved by the invention]

However, since the fluorescence X-ray analysis method using two #IIJ constant angles uses white X-rays as incident X-rays as described above, the following problems have been pointed out.

First, in the former fluorescent X-ray analysis method, ■-1 The high-energy X-rays in the white X-rays have a property of having a large penetration depth because their attenuation in the plating film is small. The first measurement angle at which fluorescent X-rays from the metal are not detected needs to be very small, within 5 degrees, so the influence of fluctuations in the measurement distance and measurement angle due to downward movement, or flapping, of the steel plate surface. There are some issues that are easy to deal with.

■-2 Also, plating (=1 coat amount and plating film composition is
It is conceivable to calculate the actual 411 strength obtained by actually injecting X-rays into the plated steel plate and the theoretical strength obtained by applying it to a well-known theoretical strength calculation formula in advance, but when calculating the theoretical strength, However, there is a problem in that the measurement accuracy decreases because it is affected by spectral fluctuations of incident X-rays due to changes in the X-ray tube over time.

■-3 In addition, the actual 71 that was measured when obtaining the analysis value
11 When calculating the analytical value by comparing the fluorescent X-ray intensity with the theoretical fluorescent X-ray intensity calculated from a well-known theoretical intensity calculation formula, the calculation time becomes long because wavelength integration is required in calculating the theoretical intensity. Therefore, the increase in /l111 constant time cannot be denied.

■-4 Furthermore, in order to avoid the problem pointed out in ■-2 above, there is a method that uses a calibration curve, but this method requires 20 to 30 types of standard samples to create a model that takes into account matrix effects. However, this is a very complicated analysis method.

On the other hand, in the latter analysis method using diffraction X-rays, the diffraction X-ray intensity of α-Fe on the ■-1 base is determined not only by the amount of plating deposited, but also by
There is a problem in measurement accuracy because it depends on the texture and plating coating composition, which vary depending on the steel type and thickness of the steel plate, the manufacturing conditions of the plated steel plate, etc.

(2) On the other hand, the diffraction X-ray intensity of the alloy phase varies depending on the plating conditions, and the structure and composition of the alloy differ between hot-dip plated materials and electroplated materials, and in this case as well, sufficient measurement accuracy cannot be obtained.

The present invention was made to solve the above-mentioned problems, and it is possible to reduce the influence of fluctuations on the surface of a plated steel plate, improve analysis accuracy, shorten analysis time, and use a small number of standard samples. It is an object of the present invention to provide a method for measuring the amount of plating and the composition of the plating film on a plated steel sheet, by which the amount of plating and the composition of the plating film can be reliably obtained.

In addition, the purpose of another invention, a device for determining the amount of plating and the composition of the plating film on a plated steel sheet, is to accurately measure the amount of plating and the composition of the plating film online using a simple configuration. It is in.

[Means and effects for solving the problems] In order to solve the second problem, the method of the present invention is obtained when monochromatic X-rays are incident on a plated steel plate at a predetermined angle of incidence. In addition to the theoretical calculation formula for the fluorescent X-ray intensity or intensity ratio of the two series of analytical elements at two predetermined measurement angles, the above theory can be calculated using a standard sample for which the amount of deposited plating and the composition of the plating film are known. The fluorescent X-ray intensity or intensity ratio is actually measured under the same conditions as those used to determine the calculation formula, and a conversion coefficient for converting the actual measurement value into the theoretical calculation value is determined in advance based on the actual measurement value and the theoretical calculation formula.

After determining the theoretical calculation formula and conversion coefficient as described above, use the same measurement conditions as those used to determine the theoretical calculation formula for a plated steel sheet to be measured whose coating weight and coating film composition are unknown. The fluorescent X-ray intensity or intensity ratio obtained from the plated steel plate to be measured is measured, and then the fluorescent
Convert the linear intensity or intensity ratio to a theoretical intensity or intensity ratio using a conversion coefficient. Then, the theoretical strength or strength ratio obtained from the theoretical calculation formula is made closest to the converted theoretical strength or strength ratio by using the plating adhesion distance and plated H#1 composition, which are the parameters in the theoretical calculation formula. The amount of plating deposited on the plated steel sheet and the composition of the plating film are measured.

In addition, in another method of the invention, two types of analysis at predetermined measurement angles are obtained when monochromatic X-rays are incident on a plated steel plate at a predetermined angle of incidence.
A calibration curve of line strength or intensity ratio is determined using the plating amount and plating film composition as parameters, and then, plating (= 1 plating amount and plating film composition are unknown).
The fluorescent X-ray intensity or intensity ratio obtained from the plated steel plate to be measured is measured under the same measurement conditions as those used to obtain the calibration curve. Further, the measurement target is determined using the plating adhesion m and the plating film composition, which are the parameters ~ in the calibration curve that bring the fluorescent X-ray intensity or intensity ratio obtained from the calibration curve closest to the measured fluorescent X-ray intensity or intensity ratio. The amount of plating deposited on the steel plate and the composition of the plating film.

In the device of the present invention, an X-ray generating section that generates X-rays;
A monochromator that monochromates the X-rays generated from this X-ray generator, a slit system that determines the path line of the X-rays, projects them onto the plated steel plate at a predetermined incident angle, and receives the X-rays at a predetermined receiving angle.
Analysis generated from plated steel sheets [Series fluorescence X of one element]
Two detectors that measure line intensities at different angles, means for storing theoretical calculation formulas for the theoretical intensities or intensity ratios that should be obtained with these measurement systems, and actually measured fluorescent X-ray intensities or intensity ratios. means for converting into theoretical strength or strength ratio, and means for determining the plating coating amount and plating film composition that minimize the difference between the converted theoretical strength or strength ratio and the theoretical strength or strength ratio obtained from the theoretical calculation formula. It is equipped with the following.

Therefore, by taking such measures, the X-rays generated from the X-ray generating section pass through the slit, are made monochromatic by a monochromator, and are incident on the plated steel plate to be measured at a predetermined incident angle, thereby allowing the Analysis i that occurs
The series fluorescent X-ray intensity of heavy elements is detected using two detectors at different predetermined acceptance angles.

Then, the fluorescent X-ray intensity or intensity ratio measured by these two detectors is converted into the theoretical intensity or intensity ratio, and the theoretical intensity or intensity ratio is calculated using a theoretical calculation formula using the plating amount and the plating film composition as variable parameters. The plating adhesion m and the plating film composition of the plated steel sheet to be measured are obtained from the parameters whose calculated values are closest to the converted values.

In addition, in other apparatuses of the present invention, in addition to a measurement system consisting of an X-ray generator, a monochromator, a slit system, two detectors, etc., a calibration curve of the theoretical intensity or intensity ratio that should be obtained with these measurement systems is provided. and a means for determining the plating coating amount and plating film composition that minimize the difference between the actually measured fluorescent X-ray intensity or intensity ratio and the fluorescent X-ray intensity or intensity ratio obtained from the calibration curve. It is prepared.

In this apparatus, the amount of coating and the composition of the plating film of the steel plate to be plated with Al11 are determined by using a calibration curve in place of the theoretical calculation formula and using a signal processing means substantially the same as that described above.

〔Example〕

Hereinafter, before a detailed explanation of the present invention is given, it is assumed that the present invention is constructed with a measurement system that satisfies the following conditions in order to be suitable for online measurement.

(a) Incident X! ! il must be able to obtain sufficient fluorescence X-ray intensity using a commercially available X-ray tube.

(b) Measurement angles such as the X-ray incident angle and fluorescent X-ray extraction angle must be achievable online, that is, 5 degrees or more.

Further, the intensity of fluorescent X-rays generated from the plated steel plate is measured with a radiation detector, and preferably, Δ11 is determined using a bull conductor detector.

Hereinafter, an example of a method for measuring the coating amount and coating film composition (Fe%) of a Zn-Fe alloy plated steel sheet will be described.

That is, in this measurement method, as shown in FIG. 1 and FIG.
1. The X-ray of λ2 is incident at an angle of incidence φ1. φ2, and the intensity of the Feka line and the Znka line generated from the plated steel plate 11 to be measured at this time are determined at the receiving angle ψ1. Measure at ψ2.

Therefore, the Feka line intensity and Zn1ca line intensity measured under the conditions of this measurement angle (φ1.ψ1) are I and I, respectively.
and Pe Zn, and the Fcka line intensities and Znka line intensities determined by Δ1 under the conditions of the measurement angle (φ2.ψ2) are I2. I2Pc
Let Zn be X]=I/I, Xl-Ii,. /In. The operation F
e Zn is performed (step S1.). Furthermore, using this XlX2, the theoretical value Y1. Convert to Y2. Here, Xl, Xl
is the theoretical value Y1. When converting to Y2, the theoretical value is the fluorescent X-ray intensity obtained when measured under the same X-ray wavelength, X-ray intensity, and geometric conditions as the Hori constant conditions, and the amount of plating on the plated steel sheet and the plating film composition. is calculated by a theoretical calculation formula using as a parameter, and based on this value, the above-mentioned
This is obtained as a value corresponding to X2. Actual measured values differ from these theoretical intensities due to the sensitivity characteristics of the detector, the influence of the slit system, etc.

Therefore, in the method of the present invention, the actual measured value X1. Convert Xl to theoretical value Y,, Y2 (step S
2).

Yl-a1X1+b1 Y2- a 2
2 is a conversion coefficient, which is the amount of plating deposited and
5 Using a standard sample whose coating film composition is known in advance, measure the fluorescent X-ray intensity or intensity ratio under the same conditions as the one used to obtain the theoretical calculation formula, and use the theoretical calculation formula to convert the actual value into the theoretical intensity or intensity ratio. It is determined by converting it into an intensity ratio. In other words, the values calculated using the theoretical calculation formula using the plating deposition amount and plating film composition of the standard sample are Y, Y2, and the above formula is established between Xl and Xl calculated from the actually measured fluorescent X-ray intensity. The conversion coefficient air82 is calculated by 2 regression analysis etc.
bl and b2 are determined in advance.

In this way, we used a theoretical calculation formula and adopted a method of configuring the differences with the actual measurement system using standard samples, so we could calculate the amount of plating, the composition of the plating film, and the fluorescence X-rays using a small number of standard samples. A relational expression of intensity or intensity ratio can be obtained.

Next, after calculating the theoretical values Y,, y2 in step S2, the plated 'fJ ffi and Fe
The above Y1. Y1' and Y2 corresponding to Y2 are determined (steps S3 and S4). After that, the process moves to step S5, where the following calculation is performed, and similar calculations are performed by changing the parameter Pk (steps S6, S4, and S5), and when the calculated value is the smallest among these calculated values, Determine the value of the parameter (Step S7), and use this determined parameter value to determine plating (=j between front coat and Fe%,
This is to obtain the coating amount and coating composition of the plated steel plate 11 to be measured.

Next, analysis results obtained using the above measurement method will be specifically explained. Now, the measurement conditions for Xl are, for example, the wavelength of incident X-ray λ1 = 1.26 people, 4111 constant angle (
φ1. ψ, ) = (15° 45°), and the measurement conditions for Xl are, for example, the wavelength λ2 of the incident X-ray = 0.71 persons, and the measurement angle (φ2° ψ2) = (75°, 60°). In addition, X
For l, an X-ray tube with a tungsten target,
For Xl, if an X-ray tube with a molybdenum target is used, the wavelength λ1. λ2 is the WLβ line, M, )l, respectively
The wavelength is near the cα line, and the above-mentioned condition (a) can be satisfied.

On the other hand, of the two measurement angles, the lower measurement angle (φ1.ψ
1) is because the wavelength λ] = 1.26 is used, which has a large attenuation to the plating film and a small penetration depth.
45°), which can be a measurement angle that fully satisfies the above-mentioned condition (b), and as a result, the plated steel plate 11
The influence of measurement distance fluctuations and mll constant angle fluctuations due to surface flapping can be reduced.

Note that the accuracy improves as there is a difference between Xl and Xl in the characteristics with respect to the amount of plating and Fa%, so λ2 is equal to λ1.
The wavelength was set to have a smaller attenuation to the plating film compared to , the measurement angle (φ2.ψ2) was also set to a larger angle compared to (φ1.ψ1), and the maximum depth at which fluorescent X-rays could be detected, that is, the analysis depth was increased. Furthermore, in order to reduce measurement distance fluctuations, the beam diameter of the incident It is desirable to detect fluorescent X-rays. Therefore, this can be realized by using a pinhole collimator of φ2 and Om+n on the incident side and opening the window of the detector on the light receiving side.

Furthermore, as another method of the present invention, when it is possible to use a large number of standard samples, instead of using the above-mentioned theoretical calculation formula, the standard sample is used to determine the amount of plating, the composition of the plating film, and the fluorescent X-ray intensity. Alternatively, the amount of plating and the composition of the plating film on the plated steel sheet 11 to be measured may be estimated using a relational expression of the intensity ratio, that is, a calibration curve.

Next, an embodiment of the device of the present invention will be described with reference to FIG. In the figure, reference numeral 11 denotes a plated steel plate to be measured, and a measurement system 12 is installed in the second part of the plated steel plate 11. This measurement system 12 includes two X-ray tubes 2131 that generate X-rays in a predetermined direction, and a pinhole collimator 22.3 that functions as a slit from the X-ray tubes 21.31.
A monochromator 23゜33 that monochromates the white X-rays incident through 2 and makes the monochromated X-rays incident on the measuring object at a desired angle of incidence.
[Measurement target plated steel plate] 1. The detector 25.35 measures the fluorescent X-ray intensity obtained from the plated steel plate 1 through a flat plate slit 24.34 whose width is variable. 26.36 is a pinhole collimator. In addition, these X-ray tubes 21
, 31. Monochromator 23.33, slit 22,2
4, 32° 34, detectors 25, 35, etc. are the drive control unit 13
The position can be adjusted using drive control signals from.

] 4 is a signal processing means, which consists of two detectors 25
．． Theoretical value conversion means 1 for converting the fluorescent X-ray intensity or intensity ratio measured in 35 into a theoretical intensity or intensity ratio, that is, a theoretical value.
5. A theoretical value calculation means 16 that calculates a theoretical value using an existing fluorescent X-ray intensity calculation formula using the plating adhesion amount and Fe% as variable parameters, and a theoretical value calculation means 16 that uses the theoretical value obtained by the theoretical value conversion means 15 and the theoretical value calculation means 16. Determining parameter value determining means 1 for determining a parameter that is equal to the obtained theoretical value
7, etc., and by using these parameter values as the amount of plating and the composition of the plating film, the plating of the plated steel sheet to be measured (1 stone needle and the composition of the plating film) can be obtained.

Next, the operation of the apparatus configured as described above will be explained.

When white X-rays are generated from the two X-ray tubes 2], 31,
This white X-ray passes through the pinhole collimator 22.32,
After being monochromated by the monochromator 23, 33, the plated steel plate 11 to be measured is subjected to an incident angle φ1=10 to 30°, φ
2 = irradiated at an angle of 45 to 90 degrees. Note that a tungsten target is used as the X-ray tube 2], and X-rays with a wavelength near the WL β ray, which is highly attenuated with respect to the plating film, are extracted from the monochromator 23 and used as incident X-rays on the plated steel plate 11 to be measured. On the other hand, a molybdenum target is used on the X-ray tube 31 side, which allows the monochromator 3
3, an X-ray having a wavelength near the Mokα ray, which is much less attenuated by the plating film than the WLβ ray, is extracted and used as the incident X-ray on the plated steel plate 11 to be measured.

After irradiating the monochromated X-rays as described below, Zn is generated from the plated steel sheet 1 to be measured.

2] α-ray intensity for Fe and acceptance angle ψ1 = 30 to 60°, respectively.
, detector 25.35 with an angle of ψ2-45~90°
Detect with. After that, the theoretical value converting means 15 is used to obtain the Xl + X 2 based on the fluorescent X-ray intensity etc. obtained by the rain detector 25.35, and this is converted to a theoretical value, and the parameter value determining means Send on 17th. On the other hand, the theoretical value calculation means]6 sends the theoretical value to the parameter value determination means 17 while determining the theoretical value using the existing fluorescent X-ray intensity calculation formula, using the plating quantity and Fe% as variable parameters in sequence. Therefore, in this parameter value determining means 17,
A predetermined calculation is performed using the theoretical value sent from the theoretical value converting means 15 and the theoretical value obtained by sequentially changing the parameters in the theoretical value calculating means 16, and the parameter value when both theoretical values become equal is calculated. The amount of plating deposited and the plating film composition of the plated steel sheet 11 to be measured are obtained from this parameter value.

Incidentally, FIGS. 4 and 5 are diagrams showing analysis results obtained using the apparatus shown in FIG. 3. This figure 4 and 5
The figure shows the wavelength λ with a monochromator of 23.33 using the above device.
] = ],, 26 people, λ2 - 0.71 people, and each measurement angle is (φ1.ψ1) = (15°, 45°)
, (φ2゜ψ2) = (75°, 60°), of which Figure 4 shows the plating (= 1 stone amount, and Figure 5 shows the plating film composition. Therefore, it is clear from these figures. As shown above, even though the actual line is subject to measurement distance fluctuations, measurement angle fluctuations, temperature and humidity fluctuations, etc., high viscosity can be measured in a short measurement time of 10 seconds.In addition, this analysis value is F (3 Alternatively, it was determined not from the fluorescent X-ray intensity of Zn but from the intensity ratio of the fluorescent X-rays of Fe and Zn, but by taking this intensity ratio, it is possible to reduce the influence of temperature/humidity fluctuations and changes over time.

It should be noted that the apparatus of the present invention was performed using a theoretical old curve equation, or may be performed using a calibration curve instead of this theoretical calculation equation.

In addition, the present invention can be implemented with various modifications without departing from the gist thereof.

〔Effect of the invention〕

As described above, the present invention provides the following various effects.

First, in claims 1 and 2, X-rays with wavelengths that are largely absorbed by the plating film are extracted through monochromatic treatment and irradiated onto the plated steel plate to be measured, so the fluorescent X-ray intensity is measured at a larger measurement angle than in the past. It is possible to reduce the influence of measurement distance fluctuations and measurement angle fluctuations due to fluttering of the plated steel plate to be measured, and it is less affected by spectrum fluctuations of incident X-rays, and does not require wavelength integration, which improves measurement accuracy.
Second, the measurement time can be shortened. Also,
Several types of standard samples are required for measurement in order to obtain conversion parameters from actual measured values to theoretical values, and these are suitable for online measurement.

Next, in claims 3 and 4, with a very simple configuration,
And online measurement of the plated steel plate to be measured 4'j
The ML and plating film composition can be measured with high precision, making a significant contribution to improving the quality of plated products.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the relationship between X-rays and a fixed plated steel plate using the method of the present invention, Fig. 2 is a diagram illustrating the analysis operation by the method of the present invention, and Fig. 3 is a diagram showing the apparatus of the present invention. FIG. 4 and FIG. 5 are diagrams showing the results of analysis obtained using the apparatus of the present invention.] 1... Plated steel plate to be measured, 12... Measurement system, 213
1...X-ray tube, 2'3.33...monochromator, 2
5.35...Detector, 13...Drive control section, 14.
...Signal processing means, 15...Theoretical value conversion means, 16...
- Theoretical value calculation means, 17...Parameter value determination means. Applicant's agent Patent attorney SuzurL Takehiko Yukishu Tsukuda 7OIIC jar and daikoma

Claims (5)

[Claims] (1) A method for measuring the coating amount and coating composition of a plated steel sheet, which comprises the following steps (a), (b), (c), and (d). (a) Theoretical calculation of the fluorescent X-ray intensity or intensity ratio of the series of analysis target elements at two types of predetermined measurement angles obtained when monochromatic X-rays are incident on a plated steel plate at a predetermined incident angle. (b) actually measuring the fluorescent X-ray intensity or intensity ratio under the same conditions as those used to obtain the theoretical calculation formula using a standard sample with a known plating coating amount and plating film composition; A step of calculating in advance a conversion coefficient for converting the measured value into a theoretical calculation value from the actual measurement value and the theoretical calculation formula; a step of measuring the fluorescent X-ray intensity or intensity ratio obtained from a plated steel plate to be measured whose coating composition is unknown, and converting it to a theoretical intensity or intensity ratio using the conversion coefficient; (d) obtained from a theoretical calculation formula; The theoretical strength or strength ratio,
A step of setting the coating amount and coating composition, which are parameters in the theoretical calculation formula, that are closest to the converted theoretical strength or strength ratio, as the coating coating amount and coating coating composition of the steel sheet to be measured. (2) A method for measuring the coating amount and coating composition of a plated steel sheet, which comprises the following steps (a), (b), and (c). (a) Calibration curve of k-series fluorescent X-ray intensity or intensity ratio of the target element for analysis at two types of predetermined measurement angles obtained when monochromatic X-rays are incident on a plated steel plate at a predetermined incident angle. (b) A process in which the amount of plating and the composition of the plating film are obtained from a plated steel sheet to be measured whose plating amount and composition of the plating film are unknown under the same conditions as those used to obtain the calibration curve. (c) measuring the fluorescent X-ray intensity or intensity ratio obtained from the calibration curve;
A step of determining the coating amount and coating composition of the plated steel sheet to be the parameters in the calibration curve that are closest to the measured fluorescent X-ray intensity or intensity ratio. (3) An X-ray generation section that generates X-rays, a monochromator that monochromates the X-rays generated from this X-ray generation section, and a pass line for the X-rays that is determined and projected onto the plated steel plate at a predetermined angle of incidence. A slit system that receives light at an acceptance angle of A means for storing a theoretical calculation formula for the ratio, a means for converting an actually measured fluorescent X-ray intensity or intensity ratio into a theoretical intensity or intensity ratio, and a means for storing a theoretical calculation formula for the ratio. 1. An apparatus for measuring the coating amount and coating composition of a plated steel sheet, comprising means for determining the coating coating amount and coating coating composition that minimize the difference in theoretical strength or strength ratio. (4) An X-ray generation section that generates X-rays, a monochromator that monochromates the X-rays generated from this X-ray generation section, and a pass line for the X-rays that is determined and projected onto the plated steel plate at a predetermined angle of incidence. A slit system that receives light at an acceptance angle of Find a means for storing the calibration curve of the ratio, and the plating coating amount and plating film composition that minimize the difference between the fluorescent X-ray intensity or intensity ratio actually measured and the fluorescent X-ray intensity or intensity ratio obtained from the calibration curve. An apparatus for measuring the amount of plating deposited on a plated steel sheet and the composition of the plating film, comprising means. (5) The slit system has a pinhole collimator on the input side,
5. The apparatus for measuring the coating amount and coating composition of a plated steel sheet according to claim 3 or 4, comprising a flat plate slit with a variable width on the light receiving side.