JPH0625894A - Production of fe-zn alloy plated steel sheet - Google Patents

Abstract

PURPOSE:To rapidly measure Fe content in a plating layer by online with high precision by determining the interplanar spacing of the alpha-phase in an Fe-Zn plating layer by measurement by an X-ray diffraction method. CONSTITUTION:At the time of producing an Fe-Zn alloy plated steel sheet by means of a continuous electroplating line, the relation between Fe content and the interplanar spacing of alpha-phase is previously determined in the form of an analytical curve, with respect to an Fe-Zn alloy plating layer whose Fe content is known. From this relation and the measured value of the interplanar spacing of alpha-phase with respect to an Fe-Zn alloy plating layer whose Fe content is unknown, the Fe content in the plating layer is measured. This measurement of the interplanar spacing of alpha-phase is done under the online of plating by an X-ray diffraction method. On the other hand, coating weight is measured. On the basis of the resulting measured values plating conditions are regulated, by which Fe content in the plating layer and coating weight are controlled to the prescribed values, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a Fe-Zn alloy plated steel sheet. More specifically, the steel sheet is plated with Fe-Zn alloy by a continuous electroplating line and the plated steel sheet adheres to the plated steel sheet. Amount of Fe-Zn alloy plating layer
Fe-Zn that controls the Fe content in the plating layer and the Fe content in the plating layer by measuring the Fe content online and non-destructively and adjusting the plating conditions based on these measured values
The present invention relates to a method for manufacturing a base alloy-plated steel sheet.

[0002]

2. Description of the Related Art When manufacturing a Fe-Zn alloy plated steel sheet by a continuous electroplating line, the amount of coating on the plated steel sheet and the Fe content in the Fe-Zn alloy plated layer are measured,
By adjusting the plating conditions based on these measured values, the amount of deposited plating and the Fe content are controlled.

Conventionally, the above-mentioned coating weight and Fe content have been measured off-line using a glow discharge emission spectroscopic analyzer. That is, during the continuous plating, a part of the plated steel sheet is cut out and a glow discharge emission spectroscopic analysis (hereinafter referred to as GDS) is performed outside the line using the above analyzer.
It is carried out by a method of measuring the coating weight and the Fe content. Here, GDS is an analysis in the depth direction of the plating layer by Ar sputtering or the like. For example, the coating adhesion amount is obtained by a method of analyzing the Fe strength distribution in the depth direction of the plating layer and estimating the plating adhesion amount from the distribution.

The above-mentioned coating amount and Fe content are controlled by
Based on the results of the above measurement, the method is performed by adjusting the plating conditions such as the current density, the plating solution concentration, and the plating solution pH so that the plating adhesion amount and the Fe content rate become predetermined values.

[0005]

[Problems to be Solved by the Invention] In the above-mentioned conventional method for producing a Fe-Zn alloy plated steel sheet, the coating amount and Fe
As described above, the content rate is measured by GDS outside the line (offline). Since this GDS analyzes in the depth direction of the plating layer, the analysis time is long and
Since it is an off-line measurement, there is a problem in rapid analysis, and therefore it lacks promptness and delays in adjusting the plating conditions for controlling the plating deposit amount and the Fe content ratio. Control for securing is difficult,
However, there is a problem that it is difficult to obtain stable quality. Further, GDS has a drawback that the analytical value may be varied due to the roughness of the plating surface of the plated steel sheet or the surface of the base steel sheet, and the analysis accuracy may be poor.

The present invention has been made in view of such circumstances, and its purpose is to solve the problems of the above-mentioned conventional ones and to manufacture Fe-Zn alloy plated steel sheet by a continuous electroplating line. In doing so, the amount of coating on the plated steel sheet and the Fe content in the Fe-Zn alloy plating layer can be measured online quickly and accurately, and the quality of the plated steel sheet can be improved. It is intended to provide a method for manufacturing a steel sheet.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the inventors of the present invention have conducted extensive studies, and as a result, Fe-Zn alloy-plated steel sheet was measured by X-ray diffractometry.
There is a good inverse inverse correlation between the interphase spacing of the α-phase of the Fe-Zn alloy plating layer and the Fe content in the Fe-Zn-based alloy plating layer. The inventors have found that there is the best correlation between the phase spacing of the phase (110) plane and the Fe content, and have completed the present invention. The manufacturing method of the Fe—Zn alloy plated steel sheet according to the present invention has the following constitution.

That is, in the method for producing a Fe-Zn alloy plated steel sheet according to the first aspect, the steel sheet is subjected to Fe-Zn alloy plating by a continuous electroplating line, and the coating amount of the plated steel sheet and Fe- The Fe content in the Zn-based alloy plating layer is measured online, and the plating conditions are adjusted based on the measured values to control the coating weight and the Fe content in the plating layer. A manufacturing method,
The Fe content in the Fe-Zn alloy plated layer was measured by
A method for producing a Fe—Zn alloy plated steel sheet, characterized in that the interplanar spacing of the α phase of the —Zn alloy plated layer is measured by an X-ray diffraction method.

In the method for manufacturing the Fe-Zn alloy plated steel sheet according to claim 2, the interphase spacing of the α phase is the interplanar spacing of the α phase (110) plane. It is a method of manufacturing a steel sheet. In the method for producing an Fe-Zn alloy plated steel sheet according to claim 3, the measurement of the coating adhesion amount is performed by measuring the plating thickness by a fluorescent X-ray method. It is a method of manufacturing a steel sheet.

[0010]

[Function] As described above, Fe-Z measured by the X-ray diffraction method
The interplanar spacing of the α phase of the n-based alloy plating layer and the Fe in the plating layer
There is a good inverse correlation with the content, especially α
It was found that there is the best correlation between the interplanar spacing of the (110) phase and the Fe content. Based on this finding, the Fe content in the plating layer can be obtained by measuring the interplanar spacing of the α phase of the Fe—Zn alloy plating layer with an unknown Fe content by the X-ray diffraction method. That is, the relationship between the Fe content and the interplanar spacing of the α phase is obtained in advance for the Fe-Zn alloy plating layer with a known Fe content, and this relationship and the Fe-Zn alloy plating with an unknown Fe content described above. The Fe content of the alloy plated layer can be accurately measured from the measured value of the α phase surface spacing of the layer. Here, the measurement of the α phase surface spacing by the X-ray diffraction method can be performed under online Fe—Zn alloy plating. Therefore, the Fe content in the Fe—Zn alloy plating layer can be measured online quickly and accurately.

Therefore, in the method for manufacturing an Fe-Zn alloy plated steel sheet according to the present invention, as described above, the Fe content in the Fe-Zn alloy plated layer is measured online by Fe-Zn alloy measurement.
The interplanar spacing of the α phase of the Fe-Zn alloy plating layer is measured by the X-ray diffraction method. Therefore, from the above, the Fe content in the Fe-Zn alloy plating layer can be calculated online. The measurement can be performed quickly and accurately.

On the other hand, the plating adhesion amount is also measured online. This measurement can be performed accurately and quickly by measuring the plating thickness by a fluorescent X-ray method as described below.

Then, the plating conditions are adjusted to control the plating adhesion amount and the Fe content ratio in the plating layer based on the measurement values of the Fe content ratio and the plating adhesion amount of the Fe-Zn alloy plating layer. I am trying. Therefore, Fe according to the present invention
According to the method for producing a Zn-based alloy-plated steel sheet, the coating amount and the Fe content in the plating layer can be accurately controlled to predetermined values, and as a result, the quality of the plated steel sheet can be improved.

When measuring the interplanar spacing of the α phase, especially the α phase
It is desirable to measure the plane spacing of the (110) plane. As mentioned above, it is especially the α-phase (110) plane spacing and
There is the best correlation with Fe content, and therefore
This is because the accuracy of the measured Fe content is further improved, and as a result, the Fe content in the plating layer can be controlled more accurately.

In the present invention, the method for measuring the coating amount online is not particularly limited, but the method for measuring the plating thickness by the fluorescent X-ray method is excellent in accuracy and speed. It is desirable to adopt.

[0016]

【Example】

(Example 1) For the Fe-Zn alloy-plated steel sheets of which the Fe content and the coating weight of the plating layer are known and different in advance, the interplanar spacing of the α phase (110) plane was measured by the X-ray diffraction method,
The relationship (calibration curve A) between the Fe content and the interplanar spacing d ₍₁₁₀₎ of the α-phase (110) plane was determined. The calibration curve is shown in FIG. Further, the same steel sheet was irradiated with fluorescent X-rays by the fluorescent X-ray method, the intensity of the fluorescent X-rays from the plated steel sheet was measured, and the Zn adhesion amount (plating adhesion amount x Zn content rate) and fluorescence X The relationship with the intensity of the line (calibration curve B) was determined. The calibration curve is shown in FIG. Thereafter, in a continuous electroplating line, the Fe-Zn alloy plated steel sheet was manufactured while controlling the coating amount and the Fe content in the plating layer as described below. still,
The above-mentioned interplanar spacing d ₍₁₁₀₎ was measured by an X-ray diffraction method (110)
The diffraction angle 2θ ₍₁₁₀₎ of the surface was measured at the highest peak position, and d was calculated from the Bragg equation, that is, the equation of λ (: X-ray wavelength) = 2d sin θ. Surface spacing d ₍₁₁₀₎ described later
Was also measured by the same method.

FIG. 2 shows an outline of the control system according to the first embodiment.
Shown in. In FIG. 2, S is a steel strip, 1 is an introducing roll, and 2 is
Is Fe-Zn alloy plating equipment (plating tank and washing equipment), 3
Is a dryer, 7 is a Fe-Zn alloy plated steel sheet, and 4 is
Fluorescent X-ray Zn adhesion amount meter for measuring the intensity of the fluorescent X-rays from Zn of the Fe-Zn alloy plated steel plate and obtaining the Zn adhesion amount from the measured value and the calibration curve B, 5 is an Fe-Zn alloy plating layer Α phase (11
0) X-ray diffraction Fe content meter for measuring the interplanar spacing by the X-ray diffraction method and obtaining the Fe content from the measured value and the calibration curve A. 6 is a digital signal 9 from these instruments 4 and 5. The process computer which analyzes the sent results, determines the plating conditions so as to obtain a predetermined coating adhesion amount and Fe content, and adjusts and controls them is shown.

In the above control system, the steel strip S is introduced into the plating equipment 2 while running, and the equipment 2 is used to make Fe-Z.
After being plated with n alloy and washed with water, it is sufficiently dried by a drier 3. Next, the Fe-Zn alloy-plated steel sheet 7 is measured for the Zn adhesion amount by the fluorescent X-ray Zn adhesion amount meter 4 and sent to the process computer 6. Further, the Fe content is measured by the X-ray diffraction Fe content meter 5 and sent to the process computer 6 for input.

In the process computer 6, the input
The plating amount is calculated from the Zn deposition amount and the Fe content value by the following formula, and based on this plating deposition amount and the Fe content value, the line speed is adjusted so that the predetermined plating deposition amount and Fe content ratio are achieved. The plating conditions such as the current density of electroplating are determined according to the above, and the adjustment is controlled. That is, when the measured value deviates from the predetermined value, the plating condition is changed so that the predetermined value is obtained instantly, and even when the measured value is likely to deviate from the predetermined value, the plating condition becomes the median of the predetermined value (predetermined range). Fine-tune to. Coating weight = [Zn weight / (1-Fe content)] ----
formula

After the Fe-Zn alloy-plated steel sheet was manufactured by the continuous electroplating line under the control as described above, the obtained Fe-Zn alloy-plated steel sheet was coated by the method such as anodic dissolution method and the amount of the deposited coating and the plating A confirmation analysis of the Fe content in the layer was performed.
The content rates were all within the prescribed values. Therefore, it is possible to measure the Fe content rate and the plating adhesion amount online and quickly and accurately, and it is possible to accurately control the Fe content rate and the plating adhesion amount to a predetermined value, so that the quality of the plated steel sheet can be improved. It was confirmed.

(Second Embodiment) FIG. 4 shows an outline of a control system according to the second embodiment. In this system, an automatic analyzer 8 for Fe—Zn alloy plating solution is added to the system of Example 1,
In addition to the current density and the like, the concentration of the plating solution can be adopted as the plating condition adjusted to control the coating weight and the Fe content. A plasma emission spectrophotometer (: ICP) is used as the plating solution automatic analyzer 8.

The automatic plating solution analyzer 8 analyzes the plating solution supplied from the plating tank of the plating facility 2 and sends the analysis result as a digital signal 10 to the process computer 6 to set a predetermined plating solution concentration range. Control so that. At this time, since the analysis is intermittent and continuous analysis is difficult, when controlling the liquid concentration, either Zn, Fe or pure water is selected based on the information, and a fixed amount is supplied to the plating equipment 2. Until the next analysis result comes out, supply is stopped and it will be in a standby state.

According to the control system of the second embodiment, the concentration of the plating solution can be adjusted in addition to the current density.
There is an advantage that it becomes easier to control the content rate and the coating deposition amount more accurately.

[0024]

EFFECTS OF THE INVENTION According to the method for producing an Fe-Zn alloy plated steel sheet according to the present invention, it becomes possible to measure the Fe content in the plating layer and the coating adhesion amount online and quickly and accurately, Adjust the plating conditions based on those measured values
Fe content rate and plating adhesion amount Since it is possible to control the plating adhesion amount and the Fe content rate in the plating layer,
It is possible to accurately control the Fe content and the coating weight to a predetermined value,
As a result, the quality of the plated steel sheet can be improved.

[Brief description of drawings]

FIG. 1 is a calibration curve for measuring the Fe content in the Fe—Zn alloy plating layer according to Example 1, showing the Fe content and the Fe—Zn alloy α phase.
It is a figure which shows the relationship with the surface spacing d ₍₁₁₀₎ of a (110) surface.

FIG. 2 is a diagram showing an outline of a control system according to the first embodiment.

FIG. 3 is a calibration curve for measuring the Zn adhesion amount of the Fe—Zn alloy plating layer according to Example 1, showing the relationship between the Zn adhesion amount and the strength measured by the fluorescent X-ray method.

FIG. 4 is a diagram showing an outline of a control system according to a second embodiment.

[Explanation of symbols]

1--Introduction roll, 2--Fe-Zn alloy plating equipment, 3--Dryer, 4--Fluorescent X-ray Zn adhesion meter, 5--X-ray diffraction Fe content meter, 6--Process computer, 7--Fe-Zn alloy plated steel sheet, 8--Automatic analyzer of plating solution, 9,10--Digital signal, S--Steel strip.

Claims (3)

[Claims] 1. Fe-Z on steel plate by continuous electroplating line
In addition to performing n-based alloy plating, measure the plating adhesion amount of this plated steel sheet and the Fe content in the Fe-Zn alloy plating layer online, and adjust the plating conditions based on these measured values to determine the plating adhesion amount and A method for producing a Fe-Zn alloy-plated steel sheet for controlling the Fe content in a plating layer, the method comprising:
Fe-Zn alloy, characterized in that the Fe content in the Zn-Zn alloy plated layer is measured by measuring the interplanar spacing of the α phase of the Fe-Zn alloy plated layer by an X-ray diffraction method. Manufacturing method of plated steel sheet. 2. The method for producing a Fe—Zn alloy plated steel sheet according to claim 1, wherein the α-phase interplanar spacing is the α-phase (110) interplanar spacing. 3. The method for producing a Fe—Zn based alloy plated steel sheet according to claim 1, wherein the coating amount is measured by measuring a plating thickness by a fluorescent X-ray method.