JP2001041910A - METHOD FOR MEASURING QUANTITY OF Cr IN CHROMATE COAT OF Cr-CONTAINING STEEL PLTE - Google Patents

Abstract

PROBLEM TO BE SOLVED: To nondestructively, quantitatively and speedily measure the quantity of Cr in a chromate coat, formed on a Cr-containing steel plate by estimating the size of the component ratio change of a processing solution, using a response signal intensity in the coat as a measurement index, and correcting the component ratio change. SOLUTION: A theoretical O quantity in each coat is calculated from a known component ratio of each processing solution, and is multiplied by an O response signal sensitivity coefficient, whereby a calculated value of an O response signal intensity is obtained. The ratio of the calculated value of the O response signal intensity in the coat and the measured value of the O response signal intensity of a standard coat by the X-ray fluorescence analysis is obtained, which is made as index value of the size of change of the O quantity in the coat. The index value of the size of the change of the O quantity is strongly correlated with the change in the size of the quantity ratio of Cr and Si in the coat. A calibration curve for obtaining the charge in the size in the quantity ratio of Cr and Si in the processing solutions is formed from the index value of the change in the size of the O quantity with the use of the relationship, and a component ratio change in the processing solution is corrected. A true quantity of Cr in the coat can be detected in this manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for analyzing a chromate film formed on a Cr-containing steel sheet. More specifically, the amount of Cr in the chromate film is quantitatively and quickly determined without destruction of the film by a fluorescent X-ray analysis method or the like, thereby improving the accuracy and efficiency of quality control of the film.

[0002]

2. Description of the Related Art Chromate treatment is a surface treatment method capable of imparting corrosion resistance, fingerprint resistance, beautiful appearance and the like to a steel sheet. Chromate-coated galvanized steel sheets, chromate-coated stainless steel sheets, and the like have been developed using this processing method, and are frequently used in the fields of building materials, home appliances, automobiles, and electric machines. Chromate treatment methods are roughly classified into three types: reaction type, electrolytic type and coating type. Among these, in recent years, a coating type chromate treatment method has been mainly used in view of corrosion resistance and lubricity of a chromate treatment film.

[0003] Until now, various investigations of the properties of chromate films have been conducted from a practical point of view. The difference in the amount of Cr in the films, the difference in the chemical properties of the films, and the chemical components coexisting in the films are considered as the quality of the films. It has been clarified that the influence of the amount of Cr has a large effect on the properties of the steel. In other words, if the amount of Cr in the chromate film is less than the predetermined amount, the workability after immersion in boiling water after painting is poor, or the film is used in a severe corrosive environment such as a coast or factory area. There is a problem that blisters are easily generated.

[0004] Therefore, in quality control of a chromate film production line, it is particularly necessary to inspect the amount of Cr by quantitative analysis of the amount of Cr with high precision. At present, analysis methods for measuring elements in a chromate film formed on a steel sheet are roughly classified into inductively-coupled high-frequency plasma emission spectrometry (ICP emission spectrometry) and atomic absorption spectrometry for measuring a solution in which the above-mentioned film is dissolved. There are a chemical component analysis method such as an analysis method, and a chemical state analysis method such as an X-ray photoelectron spectroscopy method and a fluorescent X-ray analysis method in which the film is measured as it is. Of the latter, the latter irradiates the film with an electromagnetic wave and detects the response signal radiated from the element on the surface layer of the electromagnetic wave irradiating part to determine the amount of the element in the film and the chemical state of the element in the film. This is an analytical method that has the advantage of being measurable by destruction. In addition, for the appearance quality of the film, which cannot be confirmed by the above analysis method, a method of measuring the color tone of the film by visual observation and comparing the color tone with a standard sample is used. Among the above analysis methods, the fluorescent X-ray analysis method has the advantage that the stoichiometry of the elements in the film can be measured nondestructively, quantitatively and quickly, and a large amount of measurement samples can be analyzed at once. Therefore, at present, it is frequently used as a method for measuring the amount of Cr in a chromate film formed on a galvanized steel sheet.

On the other hand, when performing X-ray fluorescence analysis of a chromate film formed on a Cr-containing steel sheet, it is difficult to measure the amount of Cr in the film from the Cr response signal alone for the following reasons. Has become. That is, the film thickness of the film is usually about 0.01 to 0.3 μm, and at such a film thickness, the response signal of Cr of the underlying Cr-containing steel sheet overlaps with the response signal of Cr in the film. This is because it is extremely difficult to quantitatively separate the response signal of Cr from the above, and thus it is difficult to accurately measure the amount of Cr in the film. Therefore, in order to apply the fluorescent X-ray analysis method to the measurement of the Cr content in the coating formed on the Cr-containing steel sheet, the Cr content is measured using the response signal of an element other than Cr in the coating as an index. Is required.

[0006] Hereinafter, C in a chromate film formed on a Cr-containing steel sheet by a conventional fluorescent X-ray analysis method will be described.
A method for measuring the amount of r will be described. As a condition for selecting an element other than Cr used as an index for quantitative measurement of the amount of Cr in the coating, the response signal intensity of an element other than Cr in the coating can ignore the influence of the response signal intensity of the element from the base. To be sufficiently large and have a correlation with the Cr content in the film. C with such conditions
By using the response signal intensity of elements other than r as a measurement index, it becomes possible to measure the amount of Cr in the film.
For example, a main component is a Cr oxide, and a Si oxide and a P
In a coating-type chromate treatment in which a compound and an organic substance such as a resin are blended, the Cr amount can be approximately measured by the following procedure. First, a chromate film whose Cr and Si contents are known and whose content ratios are different from each other is formed on a substrate at an appropriate level, and the response signal intensity of Si by X-ray fluorescence analysis of the film and the film are measured. The correlation with the amount of Cr in the medium is examined, and a calibration curve for obtaining the amount of Cr from the response signal intensity of Si is created. By substituting the response signal intensity of Si by X-ray fluorescence analysis into the equation of this calibration curve, the amount of Cr in the above-mentioned film when the component ratio of the used chromate treatment solution is known and the component ratio is constant is estimated. You can ask.

However, the method for measuring the amount of Cr obtained in this manner requires that the component ratio in the used chromate processing solution be constant, and if the component ratio in the processing solution fluctuates for some reason. In this case, the Cr amount thus obtained deviates from the true value.
In the measurement of the amount of Cr in the film, a quantitative inspection of the film by a chemical component analysis method for measuring a solution in which the film is dissolved as described above for each lot of a product in order to prevent deviation from a true amount of Cr. However, it is not practically preferable from the viewpoint of load on a manufacturing site and inspection efficiency. Against the background of the above problems, it has been desired to establish a method for quantitatively and quickly measuring the amount of Cr in a chromate film formed on a Cr-containing steel sheet in a chromate treatment product production line.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for forming a C film in a chromate film formed on a Cr-containing steel sheet.
An object of the present invention is to provide a method for non-destructively, quantitatively and rapidly measuring the amount of r.

[0009]

In view of the above, the present inventors have conducted intensive studies, and as a result, have found that, in a fluorescent X-ray analysis of a chromate film formed on a Cr-containing steel sheet, the Cr content in the film is reduced. By measuring the response signal intensity of the oxide constituent elements other than O and O, and using the equation derived from the correlation between the response signal intensity and the Cr amount, to correct the effect of the variation in the component ratio of the processing solution, The present inventors have found that the above object can be achieved by calculating the true amount of Cr in the film, and have led to the creation of the present invention. The present inventors first investigated the effect of component fluctuation of the chromate treatment solution on the response signal intensity of each element contained in the chromate film by X-ray fluorescence analysis. As a result, it was found that when the component ratio of the chromate treatment liquid varied, the response signal intensity of O in the film showed a strong correlation with the magnitude of the variation of the component ratio. The reason for this is that macroscopically, most of the components contained in the chromate treatment solution and the chromate film are oxides, and when the component ratio in the film fluctuates, the film is formed according to the difference in the atomic weight ratio of O in each of these oxides. It is conceivable that the amount of O inside changes.

Therefore, the present inventors focused on the above results,
By using the response signal intensity of O in the film as a measurement index to estimate the magnitude of the change in the component ratio of the processing solution, a coefficient for correcting the change in the component ratio is obtained. A method for measuring the true Cr content in the coating by multiplying the response signal sensitivity coefficients of the other elements and the Cr content obtained from the calibration curve of the Cr content by the above correction coefficient was examined. As chromate treatment liquid, Cr oxide and Si oxide
And a treating agent containing as a main component. First, the amount of Cr and Si
A standard chromate film whose ratio to the amount was known, and a chromate film whose ratio between the Cr amount and the Si amount was appropriately changed from the standard film were formed on the Cr-containing steel sheet. Next, the stoichiometry of the elements contained in each of these films was measured by X-ray fluorescence analysis, and the response signal intensities of O and Si and Cr were measured.
The quantitative relationship between the ratio of the amount of Si and the amount of Si was investigated. As a result, it was found that the O response signal intensity showed a linear relationship with the ratio between the Cr amount and the Si amount. The theoretical value of O in each of the films was calculated from the known component ratio of each processing solution, and the calculated value of O response signal intensity was calculated by multiplying this by the O response signal sensitivity coefficient. The ratio between the calculated value of the O response signal intensity in the film and the measured value of the O response signal intensity of the standard film by X-ray fluorescence analysis is determined, and this ratio is determined by the magnitude of the variation in the amount of O in the film. Index value. Further, the relationship between the index value of the magnitude of the variation of the O content and the magnitude of the variation of the ratio between the Cr content and the Si content in the film was examined. As a result, a strong correlation was found between the two, and using this relationship, the magnitude of the variation in the ratio between the Cr content and the Si content in the treatment liquid was determined from the index value of the variation in the O content. By correcting the variation of the component ratio in the processing solution by creating a calibration curve for
The amount can be calculated.

To date, there has been no report investigating the quantitative relationship between the variation of the component ratio in the chromate treatment solution and the amount of O in the chromate film by X-ray fluorescence analysis. There was no example in which the true Cr amount was calculated by correcting the variation in the component ratio of the processing solution. As a reason,
Since the O atom has a relatively small mass number and the intensity of fluorescent X-rays emitted by X-ray irradiation is weak based on quantum mechanical theory, the measurement of O was not suitable for X-ray fluorescence analysis. No. In response to this problem, recently, the spectral crystal of the fluorescent X-ray apparatus has been improved, and it has become possible to detect even weak fluorescent X-rays. At present, the detection sensitivity to the fluorescent X-ray intensity emitted from O is sufficient. Level. Another reason is that most of the chromate film is composed of oxides, and the total amount of O in the film measured by X-ray fluorescence analysis.
It is difficult to decompose the response signal intensity into the O response signal intensity of each oxide. Further, when the oxide constituent element is a transition metal element such as Cr, the oxide constituent element has various valences. Oxides having different numbers of O atoms bonded to one element are present in order to obtain them. Therefore, using the stoichiometry of O for quantitative analysis of the film involves complicated analytical calculations. Therefore, in general, the stoichiometry of O is not used for the quantitative analysis of Cr in the film. However, in the present invention, by utilizing the strong correlation existing between the response signal intensity of O by X-ray fluorescence analysis of the film and the magnitude of the fluctuation of the component ratio in the film, the above-described O For the first time, it has become possible to measure the true Cr content in the coating film in which the variation in the component ratio in the processing solution is corrected without dealing with complicated factors accompanying the above.

That is, the first aspect of the present invention relates to a method for forming O and Cr in a chromate film formed on a Cr-containing steel sheet.
The present invention relates to a method of measuring the stoichiometry of oxide constituent elements other than the above and, if necessary, organic constituent elements, and measuring the amount of Cr in the chromate film using the stoichiometric amounts. The stoichiometry of the present invention means a measured value of an element obtained by analyzing the above-mentioned film. That is, the stoichiometry of an element when the film is analyzed by X-ray fluorescence analysis means that the X-ray is irradiated on the film and the fluorescent X-ray emitted from the X-ray irradiating part is detected. It is the response signal intensity obtained for each element obtained, and the amount of Cr is calculated by using the response signal intensity of each element measured in this way as a stoichiometric amount and using the following formulas 1 to 8.

[0013]

(Equation 1)

In the above formula, Cr _C represents _C in the chromate film.
r, M _jI is the response signal intensity of the oxide constituent element M _j other than Cr in the film, and α and K ₁ are constants.

[0015]

(Equation 2)

In the above formula, [O / Cr] _T is a theoretical ratio between the Cr content and the O content in the film, A and B ₁ -B _i are constants, and x ₁ -x _i are the Cr content. And the amount of oxide constituent elements (M _{1 to} M _i ) other than Cr, and B _{1 to} B _i , x
_{1 to} x _i correspond to the elements M _{1 to} M _i , respectively.

[0017]

(Equation 3)

In the above formula, O _I represents the response signal intensity of O of the film, and β and K ₂ are constants.

[0019]

(Equation 4)

In the above formula, [O / Cr] _T0 is the amount of Cr and M _j
The theoretical ratio between the Cr amount and the O amount in the above-mentioned film, in which the ratio between the amounts was varied, is shown.

[0021]

(Equation 5)

In the above equation, a is a coefficient of a relational expression between the component fluctuation of the film and the rate of change of the response signal intensity of O, and x _j is a ratio of the amount of Cr to the amount of M _j in the film. x _j0 is Cr
It represents the ratio between the amount and the Cr amount of the coating in which was varied the ratio of M _j amount and M _j amount.

[0023]

(Equation 6)

In the above formula, O _I is a measured value of the response signal intensity of O of the chromate film whose chemical composition is unknown, and O _EI is obtained by substituting the response signal intensity of M _{j in} the above film into Expression 1. The calculated value of O response signal intensity obtained by substituting the obtained Cr amount (Cr _EC ) into Equation 3 is shown.

[0025]

(Equation 7)

In the above equation, y is the true Cr value from the calculated Cr amount.
Represents a correction coefficient for calculating the amount.

[0027]

(Equation 8)

In the above formula, Cr_RIs the true Cr in the above film
Quantity, Cr_ECIs M in the above film _jResponse signal strength
It represents the calculated value of the amount of Cr obtained by substituting into Equation 1.

The number 1 is the response of the oxide component element M _j other than Cr in the standard coating when using derived using standard chromate film are known chemical composition of the object element, the same chromate treating solution This is a calibration curve for calculating the amount of Cr from the signal intensity, Equation 2 is an equation for calculating the theoretical ratio between the amount of Cr and the amount of O in the standard film, and Equation 3 is the standard film obtained from Equation 1. Equation 4 is a formula for calculating the response signal intensity of O from the amount of Cr in the medium. Equation 4 shows the theoretical ratio between the amount of Cr and the amount of O in the standard film obtained from Equation 2 and the amount of C in the standard film.
r amount and Cr amount of the film in which was varied the ratio of M _j amount and O
This is an equation for calculating the magnitude of the variation of the O content from the theoretical ratio to the quantity, and Equation 5 finds the coefficient of the equation indicating the relationship between the component variation of the standard film and the rate of change of the O response signal intensity. Equation (6) indicates that O in a chromate film whose chemical composition is unknown
Response signal strength measurements and O that the chemical composition was determined by substituting the Cr amount obtained by substituting the number 1 response signal strength of M _j in an unknown film to the number 3 of the response signal strength Equation 7 is used to calculate the true amount of Cr in the film whose chemical composition is unknown by correcting the variation of the component ratio in the processing solution from the amount of Cr obtained from Equation 1 Equation 8 represents an equation for calculating the true amount of Cr in the coating whose chemical composition is unknown, in which the variation in the component ratio in the processing liquid is corrected.

Further, the second aspect of the present invention is the above Cr
And C in the chromate film formed on the steel sheet containing carbon
The present invention relates to a method for measuring the stoichiometry of oxide constituent elements other than r by X-ray fluorescence analysis.

[0031]

Embodiments of the present invention will be described below.

[Cr-containing steel sheet] The Cr-containing steel sheet used in the method for measuring the amount of Cr in the chromate film according to the present invention is as follows.
It is a substrate for forming a chromate film, and is not particularly limited as long as it can form the film and contains Cr. For example, SU is a chromate-coated stainless steel substrate material for decorative building materials.
A stainless steel plate such as S304 or SUS430 may be used.

[Chromate film] The chromate film of the present invention is not particularly limited as long as it is a film mainly composed of Cr oxide. The method for forming the same is not particularly limited, and any of a reactive type, an electrolytic type, and a coating type may be used. As the treatment material used for the formation of the chromate film, those having conventionally known various compositions are used according to the use and required characteristics of the product. When a chromate film is formed by a coating type chromate treatment, the composition of the treatment solution used is a chromic acid-phosphoric acid system (CrP ₂ O _4.
H ₂ O) as a main component, and the total amount of Cr: 5 to 100 (g)
/ l), Cr ³⁺ : 2 to 70 (g / l), Cr ⁶⁺ : ^{3 to} 70 (g / l)
l), colloidal silica (SiO ₂ ): 0 to 100 (g / l)
And the like, an acrylic resin, a urethane-based resin, a vinyl alcohol-based resin, or the like may be added as necessary.Examples of additives include titanium oxide and aluminum oxide, and the like. There is no particular limitation as long as it is other than an additive that inhibits quality characteristics such as stability and adhesion.

[Method for Measuring the Stoichiometry of Elements in Chromate Film] By irradiating the surface of an object with an electromagnetic wave, detecting a response signal of the electromagnetic wave radiated from the electromagnetic wave irradiation part, and further dispersing the response signal. The analysis method is not particularly limited as long as the analysis method can quantify the stoichiometry of the element from the response signal intensity and measure it nondestructively. X-ray fluorescence analysis is suitable for quality control of a production line in terms of quickness of measurement and mass processing. Other than the fluorescent X-ray analysis method, for example, a spectroscopic analysis method such as an X-ray photoelectron spectroscopy method or an Auger electron spectroscopy method may be used.

The chromate film prepared from a chromate treatment solution having a known chemical composition containing Si and a resin will be specifically described below. Each chromate film was formed on a Cr-containing steel sheet by using a treatment solution in which the concentrations of Si, Cr, and acrylic / styrene resin among the components contained in the chromate treatment solution were increased by about 10% from the standard treatment solution. Formed. Table 1 shows the details of the processing solutions used.

[0036]

[Table 1]

Next, the stoichiometry of each element was measured by fluorescent X-ray analysis of the coating. Table 2 shows the measurement conditions of the fluorescent X-ray analysis.

[0038]

[Table 2]

FIG. 1 is a graph showing the relationship between the Cr content (mg / m ² ) and the response signal intensity (cps) of Si with respect to the results of the fluorescent X-ray analysis of each of the samples thus measured. Shown in Also, regarding the results of the fluorescent X-ray analysis of each of the above samples,
FIG. 2 is a graph showing the relationship between the amount of Cr (mg / m ² ) and the response signal intensity of O (cps).

[0040]

FIG.

FIG. 1 shows that there is a linear relationship between the amount of Cr (mg / m ² ) and the response signal intensity (cps) of Si by X-ray fluorescence analysis in each sample. When the standard composition sample (sample 1) and each of the samples (samples 2 to 4) in which the component ratio in the processing solution was changed at the same Cr amount, the Si amount was 1
The response signal intensity of Si is higher in the sample (Sample 3) in which the amount of Cr is increased by 0%, but the sample (Sample 4) in which the amount of Cr is increased by 10% is higher than that in the standard composition (Sample 1). )
, The response signal intensity of Si is lower. This Si
The increase or decrease of the response signal strength of
It directly reflects the degree of increase or decrease in concentration. By using such a correlation between the amount of Cr and the amount of Si, the amount of Cr in the film can be calculated. On the other hand, in the sample in which the resin amount was increased (sample 2), the response signal intensity of Si was not changed and was almost the same as the standard sample (sample 1). Has no correlation. From this, it is understood that the influence of the variation of the C amount on the response signal intensity of Si can be ignored.

[0042]

FIG. 2

FIG. 2 shows that each of the above films had a Cr content (mg / mg).
m^Two) And O response signal strength (cps) are almost linear.
Relationship is seen. At the same Cr content, the above standard composition
Prepared by changing the component ratio between the coating (sample 1) and the processing solution
In comparison with the samples (samples 2 to 4), the amount of Si was increased by 10%.
The added sample (Sample 3) is compared to the standard composition sample (Sample 1).
Although the response signal intensity of all O is high, the amount of Cr is 10
% (Sample 4) is a standard composition sample (sample 1)
The response signal strength of O is lower than that of. The reason for this
It is considered as follows. The silicon oxide in the above film is converted to Si
O_TwoAnd the Cr oxide is CrO_Three(6 values)
You. SiO_TwoThen, the stoichiometric composition ratio of Si and O is Si
O is 2 atoms per atom, and Si (atomic weight: 28)
The atomic weight ratio of O (atomic weight: 16) is (16 * 2) /28=1.14
3 is greater than 1. On the other hand, CrO_ThreeThen Cr1 field
O is bonded to the atom at a ratio of 3 atoms, and Cr (atomic
Amount: 52) and the atomic weight ratio of O (atomic weight: 16) is (16 * 3
 ) /52=0.923, which is smaller than 1. Obedience
Therefore, when the ratio of the Cr oxide increases, the O in the film increases.
The amount is reduced, and thus the O response signal strength is also reduced. What
In addition, Cr has three valences and six valences,
Each chemical formula is Cr_TwoO_Three(Trivalent) and CrO_Three(6
And the stoichiometric ratio of Cr and O atoms is different
However, the present inventors conducted X-ray photoelectron spectroscopy analysis of the above film.
Investigation of the chemical state of the film
r_TwoO_Three(Trivalent) is a trihydrate state, that is, Cr_TwoO
_Three(Trivalent) 3 H _TwoO present in the film in the chemical state of O
Turned out to be. The ratio of O bonded to Cr is Cr
Is 2 atoms and O is 6 atoms and CrO_ThreeSame as (6)
The same. Therefore, when measuring the amount of Cr in the chromate film,
The effect of different valences of Cr on the analysis of O in Cr oxide
It is understood that there is no need to consider From the above, the skin
There is a phase difference between the Cr content and the O content and between the O content and the Si content in the film.
And the amount of Cr and S
It is possible to estimate the magnitude of the change in the ratio with the i amount.
You. In addition, the response of O of the sample (sample 2) in which the amount of resin was increased was increased.
The response signal intensity is almost the same as the standard composition sample (sample 1).
Therefore, the amount of C does not contribute to the O response signal strength. Yo
Therefore, there is no effect of the change in the amount of C on the response signal strength of O.
You can see it.

Cr, Si, O, C, and chromium in the chromate treatment solution used for preparing each sample shown in FIGS.
Each content of H was determined by ICP analysis. As described above, the O content was determined as being unaffected by the existence ratio of trivalent Cr and hexavalent Cr. Table 3 shows the results. In addition, in Table 3, each increase rate of resin, Si, and Cr was about 10% with respect to the standard composition.

[0045]

[Table 3]

The component ratio of each processing solution shown in Table 3, O /
Table 4 shows the calculation results of Cr, O / Si, Si / Cr, and C / Cr.

[0047]

[Table 4]

Table 4 shows the component ratio of each processing solution shown in Table 3 and the component ratio of each processing solution obtained by assuming that each component ratio of the processing solution used for the standard composition film (sample 1) is 1. . Thus, the composition ratio of the processing solution whose chemical composition is known,
The ratio of the O response signal intensity measured by X-ray fluorescence analysis of the chromate film formed using the treatment solution was compared. In Table 4, the ratio of the O / Cr ratio of the Si-increased film (Sample 3) to the standard composition film (Sample 1) is 1.034. The amount of change in the O / Cr ratio indicates the amount of change in the amount of O from the standard composition film. The ratio of the response signal intensity of O in the Si-increased film to the response signal intensity of O in the standard composition film shown in Table 4 by fluorescence X-ray analysis, that is, R in Formula 6, was 1.033. In other words, the results of the fluorescent X-ray analysis and the results of the calculations in Table 4 almost coincided with respect to the change in the amount of O. Similarly, by fluorescent X-ray analysis, the ratio between the O response signal intensity of the standard composition film and the O response signal intensity of the Cr content increasing film in Table 4 was compared with the O / Cr ratio in Table 4. ,
While the calculated value shown in Table 4 was 0.960, the ratio of the measured values was 0.956, and both values were almost the same. From the above, it can be seen that the magnitude of the change in the ratio of the amounts of O and Cr in the chromate film by theoretical calculation and the magnitude of the change in the response signal intensity of O by X-ray fluorescence analysis of the film are substantially the same. .

As described above, the O response signal intensity of each of the above films has a strong correlation with the magnitude of the increase or decrease of the O amount due to the change in the ratio of the amount of Cr to the amount of Si in each of the above films. In the actual line, when the element ratio of the treatment liquid fluctuates at the level of ± 0.03 to 0.04, the magnitude of the deviation of the Cr amount in the chromate film from the target value is ± several mg / m ^2. It has been found to reach the size,
This is a problem in product quality control. The high-sensitivity quantification method for estimating the magnitude of the element ratio fluctuation according to the present invention meets such a demand for higher precision of quality control.

The procedure for measuring the amount of Cr in the film will be described below using the above formulas (1) to (8) as an example, taking measurement of the amount of Cr in the film prepared from the above-mentioned processing solution.
(A) First, a calibration curve representing the relationship between the response signal intensity of Si (Si _I ) and the amount of Cr (Cr _C ) was prepared by fluorescent X-ray analysis of a standard chromate film having a known chemical composition. I got the formula. Cr _C = α * Si _I + K ₁ = (4.9E-3) * Si _I− 24.01 (mg / m ² ) (1)

(B) The theoretical ratio ([O / Cr] _T ) between the Cr content and the O content in the coating was determined as follows.
The known composition of the above film is Si: 23 (g / l), C:
Since r: 43 (g / l), x = 23/43.
M * n, which is the ratio of the O content in the organic substance to the Cr content in the film, is such that the organic substance is an acrylic-styrene copolymer, C: 65 (g / l), and the atomic weight of C and O The ratio is 0.
It was calculated using the value of 138 (actual value). [O / Cr] _T = 0.923 + 1.143 * x + m * n (2) = 0.923 + 1.143 * (23/43) + (65/43) * 0.138 = 1.744

(C) Further, the following equation was obtained as a relational expression between the response signal intensity (O _I ) of O in the above-mentioned fluorescent X-ray analysis and the amount of Cr (Cr _C ). O _I = β * Cr _C + K ₂ = 36.188 * Cr _C +308.2 (mg / m ² ) (3)

(D) Sample 1 and 10
The magnitude _RT of the change in the theoretical ratio between the Cr amount and the O amount of the sample 3 which was increased by% was determined as follows. In addition,
[O / Cr] _T is the theoretical ratio between the Cr content and the O content of Sample 1, and is determined to be 1.744 from the above equation (2). [O /
Cr] _T0 is a theoretical ratio between the Cr amount and the O amount of the sample 3, and is 1.804 when the Si amount is increased by 10% with x in the above equation (2). Therefore, _RT is as follows. R _T = [O / Cr] _T0 / [O / Cr] _T = 1.804 / 1.744 = 1.034 (4)

(E) Next, the change in the composition of the chromate film and the O
A relational expression with the response signal intensity change rate is obtained. As described above, when the coefficient of the relational expression is a based on the fact that the Cr amount and the O intensity have a linear relationship, a is represented by the following expression. _{x j / x j0 = a *} ((x j / x j0)) * R T) + b in the above formula, b is a constant, x _j is in the standard film M _j / C
The r ratio, x _j0, is the M _j / Cr ratio in the coating obtained by changing the composition ratio of the standard coating. Where M _j is C in the film
represents an oxide constituent element other than r. In the above equation, when the composition of the standard film does not change, x _j / x _j0 = 1 and R _T =
Since it becomes 1, there is a relation of 1 = a + b, that is, b = 1−a. When this is substituted into the above equation and solved for a, the following equation is obtained. a = ((x _j / x _j0 ) -1) / ((x _j / x _j0 ) * _RT- 1) (5) In the above formula, the Si / Cr ratio is 10% from the standard composition ratio of Si.
When a is obtained in the case where the number increases, the following equation is obtained. a = ((1 / 1.1) -1) / ((1 / 1.1) * 1.034-1) = 1.515 Note that 1.034 in the above equation was obtained by the above equation (4). R
_T.

(F) The response signal intensity of O of the chromate film whose chemical composition is unknown and the response signal intensity of Si are determined by the above (1).
The Cr content obtained by substituting into the equation (provisional value obtained assuming that there is no change in the component ratio in the above-mentioned film) into the above-mentioned equation (3) is obtained by substituting into the above-mentioned equation (3) The ratio of the response signal intensity of O to the calculated value was determined as follows. S
The response signal strength (Si _I ) of i: 16000 (cps) is substituted into the above equation (1), and Cr _c = (4.9E-3) * 16000-24.01 = 54.4 (mg / m)
² ) is obtained, and the Cr content is substituted into the above equation (3) to calculate the response signal intensity of O of the film whose chemical composition is unknown: O _EI
= 2277 (cps). At this time, the measured value was 2155 (cps). Therefore, R is as follows. R = (O _I -K ₂ ) / (O _EI -K ₂ ) = (2155-308.2) / (2277-308.2) = 0.938 (6)

(G) Here, y which is an index value of the change in the component ratio between Si and Cr is obtained. This y can be expressed as y = x ₁ / x _S where Si / Cr in the standard film is x _S and Si / Cr in the film whose chemical composition is unknown is x ₁ . At this time, R obtained by the above equation (6) is (O _I -K ₂ ) / R in the film whose chemical composition is unknown.
Assuming that (O _EI -K ₂ ) is R _S , it is represented by R = (x ₁ / x _S ) * R _S. Accordingly, a = a calculated from the above equation (5)
1.515, y is obtained using R = 0.938 obtained from the above equation (6), and the result is as follows. y = x ₁ / x _S = a * R−a + 1 = 1.515 * 0.938−1.515 + 1 = 1.906 (7)

(H) The response signal strength of the Si and the amount of Cr
Amount of Cr (Cr _EC)
Multiply by the number (y) to find the true Cr amount as follows
Was. Cr_R= Cr_EC* Y = 0.906 * 54.4 = 49.3 (mg / m^Two)  (8) From the calibration curve of the response signal intensity of Cr and the amount of Cr by the conventional method
The calculated amount of Cr is approximately
10% more. Also, it is determined separately by ICP analysis.
The amount of Cr in the above film determined from the amount analysis was 48.8 (mg / m
^Two), And almost coincides with the true Cr amount by the above correction.
Turned out to be.

The method of calculating the theoretical ratio between the Cr content and the O content when the film contains a resin will be specifically described below. Si in the above film
The ratio of the amount of Cr / the amount of Cr is x, and the theoretical ratio ([O / Cr] _T ) between the amount of Cr and the amount of O in the film is calculated by the following equation (21). [O / Cr] _T = 0.923 + 1.143 * x ₁ + m * n (21) In the above formula, 0.923 represents Cr in the Cr oxide in the film.
And 1.143 is the atomic ratio of O to Si in the silicon oxide in the film,
m * n represents the atomic weight ratio of O in the organic substance to Cr in the film. m is the ratio of the amount of organic matter to the amount of Cr in the film, and n is the ratio of the amount of O in the organic matter. When the resin contains a styrene-acryl copolymer (Chemical Formula 1) and is blended with a resin so that the ratio of the amount of the organic substance to the amount of Cr is 65/43, the O amount in the organic substance is actually measured. M = 65/43, n = 0.
138, m * n = 0.209.

[0059]

Embedded image

According to the present invention, Si oxide and P
When a compound is contained, the response signal intensity of P is also measured at the time of X-ray fluorescence analysis, and the term (1.032 * x ₂ ) for calculating the amount of O in the P compound is included in the above formula (2). calculate. That is, it is represented by the following equation. [O / Cr] _T = 0.923 + 1.143 * x ₁ + 1.032 * x ₂ (23) In the above formula, x ₁ and x ₂ are the respective ratios of the Cr amount and the Si amount (Si amount / Cr amount). , The ratio of the Cr amount to the P amount (P amount /
Cr amount). In the above formula, 1.032 represents the atomic weight ratio between P and O when phosphoric acid (H ₃ PO ₄ ) is added to the chromate treatment liquid. In this case, since chromium phosphate hydrate (CrPO ₄ .H ₂ O) is generated in the chromate treatment liquid, the atomic weight of Cr: 52, the atomic weight of P: 31, and the atomic weight of O: 16 are used. 5) / 31- (52 * 0.923) / 31 =
1.032. Note that the second term of the above formula is the above (2)
Since the total amount of Cr is already included in the first term of the expression (3), the amount corresponding to Cr in the chromium phosphate is subtracted.

The method for determining the magnitude of the variation in the component ratio blended in the chromate treatment solution when the film contains Si oxide and P compounds is described above. This corresponds to the case where the constituent element is Si alone.

Further, the present invention can be applied to oxides other than Cr oxide, Si oxide, resin, and P compound as the components of the chromate treatment liquid in accordance with the above-described procedure.

[0063]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples. (I) Cr-containing steel sheet to be treated SUS304, SUS430 (II) Chromate treatment (i) Composition of treatment liquid (A) Total Cr amount: 40 (g / l) Si amount: 40 (g / l) (ii) Treatment liquid Composition of (B) Total Cr amount: 40 (g / l) Si amount: 40 (g / l) P amount: 12 (g / l) Resin amount: 15 (g / l) (iii) Coating amount (Cr conversion) (Value): 20 to 100 (mg / m ² ) (III) X-ray fluorescence analysis conditions Table 5 shows the measurement conditions for X-ray fluorescence analysis of this example.

[0064]

[Table 5]

Example 1 A processing solution in which a chromate film was formed on the SUS304 steel plate using the processing solution (A), and the ratio of the amount of Cr to the amount of Si was appropriately changed from the processing solution (A) Was used to form a chromate film. X-ray fluorescence analysis of each film was performed, and the response signal intensities of O and Si were obtained. Table 6 shows the results of the fluorescent X-ray analysis with and without the correction of the Cr content in comparison with the results of the chemical component analysis by ICP analysis.

[0066]

[Table 6]

From Table 6, the results with the correction of the Cr content using the fluorescent X-ray analysis method according to the present invention are almost consistent with the results of the chemical component analysis by ICP analysis within 5%.
It turns out that it is the same level as the high-precision quantitative analysis method of the conventional method. On the other hand, in the result without correction, the difference from the result of the ICP analysis is as large as about 10% at the maximum, and there is a practical problem because the accuracy is low. The treatment liquid (A) is dried and solidified,
When the powder was made into a powder and the O content was measured by oxygen analysis, it was confirmed that the O content was 41 parts by weight. Conventional fluorescent X
The line analysis method has been unsuitable for the measurement of such a film with a large amount of O as described above. However, with the recent improvement of the above analysis method, it is possible to detect the response signal from O in the chromate film. Further, by applying the present invention to the measurement of the amount of Cr in a chromate film formed on a Cr-containing steel sheet, which had a problem with the conventional method, the true Cr in the film can be quickly obtained.
For the first time it was possible to get the quantity.

[Example 2] A chromate film was formed on the SUS430 using the treatment liquid (B), and the ratio of the amount of Cr to the amount of Si and the ratio of the amount of Cr to the amount of P were determined from the treatment liquid (B). A chromate film was formed using an appropriately changed treatment liquid. Table 7 shows the specifications of the samples. X-ray fluorescence analysis of each film was performed, and the response signal intensities of O and Si were obtained. Fluorescent X
Table 8 compares the results of the line analysis with and without the correction of the Cr content and the results of the chemical component analysis by ICP analysis.
Shown in Also, the relationship between the Cr content of the samples having different P / Cr and P / Si ratios and the O response signal intensity (samples S3-P2, P1-S2-
C3, S1-C2, S1-S2-S3) is shown in FIG.
FIG. 4 shows the relationship between the ratio of the P content and the Cr content (P / Cr ratio) of the samples having different / Cr and P / Si ratios and the calculated value of the O content in the film.

[0069]

[Table 7]

[0070]

[Table 8]

According to Table 8, the result without the correction of the Cr amount is IC
The difference from the result of the P analysis is as large as about 13% at the maximum and the accuracy is low, so that there is a practical problem. On the other hand, C
The result with the correction of the amount of r almost coincides with the result of the chemical component analysis by ICP analysis within 5%, which indicates that the result is at the same level as the conventional high-precision quantitative analysis method. From the above results, it can be seen that the Cr content corrected according to the present invention in the X-ray fluorescence analysis can measure the true Cr content in the coating more accurately than without correction.

[0072]

FIG. 3

[0073]

FIG. 4

FIG. 3 shows a linear relationship between the amount of Cr and the O response signal intensity, and this relationship shows a powerful basis for deriving the true amount of Cr from the O response signal intensity. FIG. 4 shows a linear relationship between the ratio of the amount of Cr and the amount of P and the amount of O in the chromate film. This relationship is a powerful one that can derive the true amount of Cr and the amount of P from the O response signal intensity. It shows the basis. Although not shown here, the amount of Cr and S
Similar results were obtained for the relationship between the ratio to the i amount and the response signal intensity of O in the film.

[0075]

As described above, according to the present invention, the amount of Cr in the above-mentioned film can be calculated with high accuracy and speed without destroying the chromate film, and it can be used for automobiles, home appliances, building materials, etc. The quality control technology of the chromate-treated Cr-containing steel sheet to be provided in the above is improved, and it is possible to meet recent strict requirements for surface quality.

The control of the amount of Cr in the chromate film formed on the Cr-containing steel sheet can be performed without impairing the productivity.
It can be performed at any time without any load on the site,
It can contribute to the improvement of the operation stability technology of the actual line.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazumi Matsubara 1-7-1, Takatani-Shimmachi, Ichikawa-shi, Chiba F-term in the Technical Research Laboratory of Nisshin Steel Corporation (Reference) 2G001 AA01 AA03 AA10 BA04 BA08 BA09 CA01 CA03 CA10 FA01 FA08 GA01 KA01 LA02 MA05 NA03 NA07 NA10 NA17 NA19 NA20 4K026 AA02 AA04 AA22 BA06 CA20 CA23 CA39 CA41 DA16

Claims (5)

[Claims] 1. A chromate formed on a Cr-containing steel sheet.
A method for measuring the amount of Cr in a coating, comprising:
Less than O in the oxide film and Cr in the chromate film
Outer oxide constituent element M₁, M_Two, ..., M_iStoichiometry
And the O and M thus determined₁, M
_Two, ..., M_iFrom the following (1), using the stoichiometry of
The amount of Cr in the chromate film is calculated based on the calculation formula (8).
Method for measuring Cr content in chromate film
Law. (1) Measure standard chromate film with known chemical composition
From the stoichiometry of oxide constituent elements other than Cr obtained by
Cr content in the above standard coating: Cr_C= Α * M_jI+ K₁ (2) Theoretical ratio between the Cr content and the O content in the standard coating: [O / Cr]_T= A + B₁* X₁+ B_Two * X_Two＋ ・ ・ ・
+ B_i* X_i(I = 1, 2,...) (3) Relationship between O stoichiometry and Cr content in the above measurement
Formula: O_I= Β * Cr_C+ K_Two (4) The ratio of the components contained in the standard film is varied.
Of the change in the theoretical ratio between the amount of Cr and the amount of O when immersed: R_T= [O / Cr]_T0/ [O / Cr]_T (5) The difference between the component fluctuation of the standard coating and the stoichiometric change rate of O
Coefficient a of relational expression: a = ((x_j/ X_j0) -1) / ((x_j/ X_j0) * R_T
-1) (6) By measuring a chromate film whose chemical composition is unknown
The obtained stoichiometry of O (O_I) To K in the above equation (3)_TwoTo
Subtract the subtracted value and the Cr amount obtained from the above equation (1)
The calculated stoichiometric value of O obtained by substituting into equation (3) (O_EI)
From above K_TwoR = (O_I-K_Two) / (O_EI-K_Two(7) Calculate the true amount of Cr in the film whose chemical composition is unknown
Correction coefficient: y = a * R-a + 1 (8) True amount of Cr in the film whose chemical composition is unknown: Cr_R= Cr_EC* Y (in the above formula, Cr_CIs the above standard film or the above chemical composition
Is the amount of Cr in the unknown coating,_I, O_EIAre each
The measured value of the stoichiometry of O in the film and the calculated value of the stoichiometry of O
M_jIOxide constituent element M other than Cr in the above coating_jof
Stoichiometric, [O / Cr]_TIs the amount of Cr in the above film
It is a theoretical ratio with the amount of O, [O / Cr]_T0Is the above standard
Cr amount when the ratio of the components contained in the coating is changed
And the theoretical ratio of O amount, α, β, K₁, K_Two, A,
B₁~ B_iIs a constant and x₁~ X_iIs Cr content and Cr
Oxide constituent elements (M₁~ M_i) The ratio to the quantity,
x _j, X_j0Is the amount of Cr in the above coating and M_jWith quantity
Ratio, Cr content and M_jIn the above film, the ratio of
Cr content and M_jIs the ratio to the amount_ECIs the above (1)
Represents the calculated value of Cr obtained from the equation,₁~ B_i, X₁~
x_iIs the above element M₁~ M_iCorresponding to ) 2. An organic substance is contained in a chromate film.
If there is, replace the above equation (2) with the following equation (21)
A method for determining the amount of Cr in a chromate film.
3. The method for measuring the amount of Cr in a chromate film according to claim 1.
(21) O atoms in organic matter with respect to Cr in the coating
The ratio of the amount of Cr and the amount of organic matter in the film
m and the ratio of the amount of O in the organic matter to n, this m
From the product of n and n, and the term of the product of m and n is given by the above equation (2).
To be calculated. That is, the amount of Cr in the coating and the amount of O
Theoretical ratio to the amount: [O / Cr]_T= A + B₁* X₁+ B_Two * X_Two＋ ・ ・ ・
+ B_i* X_i+ M * n (i = 1, 2,...) (Where A, B₁~ B_iIs a constant, and x is
Cr content in the sub-coat and oxide constituent elements other than Cr (M₁~
M_i) Represents the ratio to the amount, where m and n are the amounts of Cr in the above film
To Cr_C, Organic matter amount C_C, The amount of O in organic matter_CToss
Then m = C respectively_C/ Cr_C, N = O_C/ C_CRepresented by
And B₁~ B_i, X₁~ X _iIs on each
Element M₁~ M_iCorresponding to ) 3. When the oxide constituent element other than Cr contained in the chromate film is Si alone, the above (1):
Equations (2) and (5) are replaced by the following equations (12), (22) and (52)
2. The method for measuring the amount of Cr in a chromate film according to claim 1, wherein the amount of Cr in the chromate film is calculated instead of the equation. (12) Cr content in the standard chromate film having a known chemical composition: Cr _C = γ * Si _I + K ₃ (22) Theoretical ratio between the Cr content and the O content in the standard film: [O / Cr] _T = 0.923 + 1.143 * x (52) Coefficient a of the relational expression between the component fluctuation of the standard film and the stoichiometric change rate of O: a = ((x / x ₀ ) -1) / ((x / x ₀₎ * R _T -
1) (where γ and K ₃ are constants, Cr _C is the amount of Cr in the standard film, O _I and O _EI are the stoichiometric values of O in the standard film, and Calculated stoichiometry,
Si _I is the stoichiometric amount of Si in the standard coating, [O /
Cr] _T is the theoretical ratio between the Cr content and the O content in the standard coating, and x and x ₀ are the C ratios in the standard coating, respectively.
The ratio of the amount of Cr to the amount of Si and the ratio of the amount of Cr to the amount of Si were varied from the above standard film, and the amounts of Cr and S in the chromate film were changed.
Indicates the ratio with the i amount. ) 4. When the oxide constituent elements other than Cr contained in the chromate film are Si and P, the above formulas (1), (2) and (5) are replaced by the following formulas (13), (23),
The method for measuring the amount of Cr in a chromate film according to claim 1, wherein the amount of Cr in the chromate film is calculated in place of the equation (53). (13) Cr content in the standard chromate film whose chemical composition is known: Cr _C = δ * Si _I + K ₄ (23) Theoretical ratio between the Cr content and the O content in the standard film: [O / Cr] _{T = 0.923 + 1.143 * x 1} +1.
032 * x ₂ (53) Coefficient a of the relational expression between the component fluctuation of the standard film and the stoichiometric change rate of O: a = ((x ₁ / x ₁₀ ) -1) / ((x ₁ / x ₁₀ ) * _RT
-1) (where δ and K ₄ are constants, Cr _C is the amount of Cr in the standard coating, O _I and O _EI are the stoichiometric values of O in the standard coating, Is the calculated stoichiometric value of
Si _I is the stoichiometric amount of Si in the standard coating, [O /
Cr] _T is the theoretical ratio between the Cr content and the O content in the standard coating, and x ₁ , x ₂ , and x ₁₀ are the ratio between the Cr content and the Si content in the coating, the Cr content and the P content, respectively. Ratio with quantity,
The ratio between the amount of Cr and the amount of Si in the chromate film is shown by varying the ratio of the amount of Cr to the amount of Si from the standard film. ) 5. The Cr content in the chromate film according to claim 1, wherein the stoichiometry of the elements in the chromate film is measured by X-ray fluorescence analysis. Quantity measurement method.