JPS6199688A - Method for measuring iron concentration in plated layer of alloyed zinc plated steel sheet and manufacture of said steel sheet - Google Patents

Abstract

PURPOSE:To measure Fe concn. in plated layer of alloyed Zn plated steel sheet nondestructively, continuously and accurately by measuring X-ray diffraction intensity and counted value relating unit area of plated layer of said steel sheet and substituting the measured value into regression formula. CONSTITUTION:Characteristic X-ray is irradiated to alloyed Zn plated steel sheet to measure X-ray diffraction intensity relating to >= one phase among Fe-Zn alloy phase and eta phase. On the other hand, counted value relating to unit area is measured by fluorescent X-ray method, etc. Next, these measured values are substituted into regression formula using said measured values as variable and Fe concn. in plated layer as function, to obtain said Fe concn. In manufacturing said steel sheet by heating after Zn plating it, said Fe concn. is measured continuously by said method, heat treating condition is controlled automatically based on the measured value, to form plated layer of the aimed Fe concn.

Description

[Detailed Description of the Invention] <Field of Application in Industry-E> The present invention provides a method for non-destructively and continuously measuring the Fe concentration in alloyed galvanized plating, and the measured values obtained by this method. The present invention relates to a method for producing an alloyed galvanized steel sheet in which the Fe concentration is controlled within an appropriate range by controlling the alloying heat treatment conditions based on the following.

<Prior art and its problems> In order to improve the quality characteristics of hot-dip galvanized steel sheets and electrogalvanized steel sheets, such as weldability, corrosion resistance after painting, and coating adhesion, these galvanized steel sheets are subjected to heat treatment. , the Fe-Zn alloy phase was made longer in the plating layer,
A so-called alloyed galvanized steel sheet is produced. The Fe concentration in the plating layer is normally 10-13 weight percent (hereinafter abbreviated as %), but the Fe concentration changes if there is excess or deficiency in the heat treatment. Variations in Fe concentration during plating have a significant impact on the quality characteristics of the plating layer.

:JJ1 diagram shows the relationship between the Fe concentration in plating and various quality characteristics of the plating layer based on experiments conducted by the inventors.

For example, the workability of the plating layer deteriorates as the Fe concentration in the plating increases, and the film adhesion, post-painting corrosion resistance, and spot weldability, conversely, improve as the Fe concentration increases. Ru.

Therefore, in order to obtain excellent quality characteristics of the plating layer, it is essential to control the Fe concentration in the plating within an appropriate range.
In order to control the e-concentration, it is important to properly control the heat treatment conditions.

However, although current production lines for alloyed hot-dip galvanized steel sheets are continuous and high-speed in order to prioritize productivity, there is currently no technology to non-destructively and continuously measure the Fe concentration in the coating. is 13M not emitted,
For this reason, on the same production line, a method of estimating the approximate F e of 76 degrees empirically is mainly carried out by visual inspection1, and heating conditions have to be controlled based on this estimation. e A large number of defective products were often produced due to excess or deficiency of 73 degrees.

In view of the actual situation mentioned above, the inventors were acutely aware of the need for a method that could accurately measure the Fe concentration in plating, and conducted various studies.

By the way, according to the research conducted by the inventors, as conceptually shown in Figure 2, the Fe concentration in the plating and the thickness occupied by the Fe-Zn alloy phase and the η phase in the plating layer that constitute the plating layer are There is a close relationship with the ratio, that is, the phase composition of the plating phase, and if the phase composition is known, the Fe concentration of the leopard can be determined.

In addition, Figure 3 shows the plating layer based on the research conducted by the inventors.
X-ray diffraction intensity determined for each phase by A-diffraction and Fe in plating
There is a close relationship between the X-ray diffraction intensity of each phase such as η phase, ζ phase, δ1 phase, and r phase and the Fe concentration in plating, and the X-ray diffraction intensity of each phase is measured. It was found that the Fe concentration in plating can be determined by doing this.

However, the inventors' research revealed that in alloyed galvanized steel sheets with different basis weights, the diffraction intensity of each phase and F
It was found that the IA relationship with e concentration was significantly similar. That is, when the basis weight differs, a measurement error occurs in the Fe concentration.

For this reason, in current production lines that continuously produce alloyed galvanized steel sheets at high speed, the basis weight changes for each coil depending on the order, or the fabric weight changes between two air dies for adjusting the basis weight jA. It is difficult to measure the true Fe concentration during plating because variations in the basis weight often occur due to t6+ warpage in the width direction of the plate or deviation of the plate in one die direction.

<Object of the Invention> The present invention has been made in view of the above-mentioned circumstances, and provides a method for non-destructively and continuously measuring the true Fe concentration in coating, and a method for continuously measuring alloyed galvanized steel sheets based on the measured values. To provide a method for producing an alloyed galvanized steel sheet, which can produce an alloyed galvanized steel sheet with an appropriate Fe concentration in the plating by automatically controlling heat treatment after plating performed during production. The purpose is to

<Structure of the Invention> The present inventors irradiated an alloyed galvanized steel sheet with a characteristic Xi, and determined the Fe-Zn alloy phase and the η phase, that is, the phase with one or more selected from metal zinc during plating. xv
x of one or more phases by measuring the i diffraction intensity and simultaneously measuring the count value related to the basis weight on the other hand, and using these measured values as a function of the pre-obtained Fe concentration in the premixing.
! ! It has been found that the Fe concentration in plating can be accurately measured by substituting the constant value of the diffraction intensity and the measured value of the count value related to the basis weight into a regression equation in which variables are used.

As mentioned above, the first feature of the present invention is that the Fe-Zn alloy phase and the The X-ray diffraction intensity of one or more phases selected from among them is measured, and at the same time, the count value related to the basis weight is also measured by some method, and each measured value is calculated in advance. X-ray diffraction intensity (x, , x2...) of one or more selected from the alloy phase and the η phase
A method of measuring the Fe concentration in the plating of a 1-alloyed galvanized steel sheet by substituting the measured value (Xt) related to the area weight (Xn) and the measured value (Xt) as variables and the Fe concentration in the plating as a function (Y). It is in.

Hereinafter, the first invention will be explained in detail.

As mentioned above, the phase composition of the plating layer of a single-alloyed galvanized steel sheet changes depending on the concentration of Fe in the plating (Fig. 2), and the X-ray diffraction intensity of each phase constituting the plating layer is During plating, Fe changes according to 8 degrees (Fig. 3), therefore,
The Fe concentration in the plating can be measured by measuring the X-ray diffraction intensity of each phase, and the inventors' research has shown that the relationship between the Fe concentration in the plating and the X-ray diffraction intensity of each phase is , it has been found that it can be expressed accurately by the relational expression illustrated below.

Y, = f (Xη) ... Bow, Y2 =
f (Xr) −・−2r.

Y3 = f (Xη, X61) ・”*r
.

Y4 = f (Xy+, XJ, Xr)+++IJ
However, ), in the above relational expression.

Y: Fe concentration in plating, Xη: Diffraction intensity of η phase, Xδ1: Diffraction intensity of δl phase, xr: Diffraction intensity of r phase It is.

However, as shown in FIG. 4, for example, the above-mentioned relationship differs significantly depending on the basis weight. Namely.

It has been found that a significant error occurs in the measured value of FEG degree during plating due to variations in the basis weight.

On the other hand, in the present invention, Y+ ′= f (Xn, It) ・
-1;・'.

Y2' = f (XI: , It)
---Ki)', Y3' = f (xη, xδ,
, r B −=>' , Y4' = f
(X'?, Xδ+, Xr, It)...4
)', i.e., a regression equation using the X-ray diffraction intensity of η phase, δ1 phase, r phase, etc. and the measured value of the basis weight (It) as a function of the Fe concentration in plating as variables. By calculating this in advance and substituting the measured values of the X-ray diffraction intensity of the η phase, δ1 phase, r phase, etc. and some measured value related to the area weight, the F during plating of the alloyed galvanized steel sheet can be calculated.
e concentration is measured.

That is, the inventors calculated the deviation of the Fe concentration for each fabric weight for each equation of ■, force +j), and
) and the Fe concentration deviation, it was found that in each equation, the Fe concentration deviation can be expressed by the relational expression ΔY=f (t) using the basis weight as a variable.

By the way, the basis weight can be determined by the well-known fluorescent X-ray method, X-ray diffraction method, and RI) laser method.
The relationship 1 with measured values such as PS) or radiation part (CPS) is determined by a calibration curve of the relational expression t=f(1) (where L=fabric weight, I-measured value). Therefore, Fe
The density deviation can be expressed as a measured value related to rt, that is, the basis weight.

The second feature of the present invention is that in a continuous galvannealed steel sheet production apparatus that produces galvannealed steel sheets by heat-treating after galvanizing, the force method for measuring Fe concentration in plating of the present invention described in 1. By setting the F e f concentration during plating to i
! I! To manufacture alloyed galvanized steel sheets by systematically measuring and comparing the measured Fe concentration in the plating with a preset standard Fe concentration, and automatically controlling the heat treatment conditions according to the deviation value. A method of manufacturing an alloyed galvanized steel sheet is provided.

Namely, alloyed galvanized steel sheet! ! As described above, the layer properties change depending on the Fe concentration in the plating, so it is necessary to select the Fe concentration in the plating in accordance with the target level of properties.

Now, if the target Fe concentration in plating is Y&, and the measured value of Fe concentration in plating by the measuring method of the present invention is Y,
The deviation value is ΔY-(Ya-Y), (Ya-Y)
> O, the target is met] and the Fe concentration is low, so it is necessary to take measures to increase the Fe concentration during plating.
The Fe concentration in plating can be increased by increasing the cal) or by lengthening the heating time. Conversely, if (Ya-Y)<0, the Fe concentration can be reduced to the target Fe concentration by lowering the heating energy or shortening the heating time.

In other words, if the Fe concentration measurement unit during plating according to the method of the present invention is linked with the process computer and the operations described in 1-1 are performed, instantaneous response is possible and the target Fe concentration during plating can always be set at 5 degrees. is possible.

For example, by the method of the present invention, FI during plating can be applied to an alloyed galvanized steel sheet in the width direction! If the concentration is measured, the Fag degree deviation value ΔY is determined at each part in the width direction of the sheet, and heat treatment is performed in the width direction according to the deviation value, it is possible to manufacture an alloyed galvanized steel sheet with a uniform Fe concentration across the entire width. It is possible.

Example of implementation Hereinafter, the present invention will be specifically explained with reference to examples.

(Example 1) In the continuous hot-dip plating line of Zenzima one-way, the basis weight was 130 g/rn'' (one side), 60 g/rn' (one side),
An alloyed galvanized steel sheet of 90 g/m' (one side) was manufactured by varying the FETK degree during plating from 3 to 15% (concentration analyzed by atomic absorption spectrometry). Regarding these, Fe during plating by the method of the present invention.
The concentration was measured. The basis weight was measured by fluorescent X-ray method, and X-ray diffraction was performed under the following conditions. Measurement results first
Shown in the table.

X-ray diffraction device; Parallel beam optical system X-ray diffraction device characteristics
-α ray diffraction angle (2θ) to +Cr line: η phase 135.5 @ δ electric phase 12B, 8.

rJ 139.0" As can be seen from Table 1 below, the method of the present invention allows accurate measurement of Fe concentration in plating.
Furthermore, it can be seen that the measured value hardly changes depending on the basis weight.

The regression equation is based on the above-mentioned ・4)′, that is, η phase, δ1
A regression equation was used in which the diffraction intensities of the phase and r-phase three layers and the measured value of the grain by fluorescent X-ray were used as variables, and the Fe concentration in the plating was used as a function.

(Example 2) I! In the Li hot-dip plating line, η phase, δ! by X-ray diffraction method using parallel beam optical system similar to Example 1. Measure the diffraction intensity of the phase and the diffraction intensity of α-Fe using the same X-ray diffraction method as a measurement value related to the basis weight,
The Fe7 concentration in plating is continuously measured using the regression equation (see), and the furnace temperature in the heat treatment furnace is continuously adjusted according to the deviation value between the measured value and the target Felfa degree in plating. Alloyed galvanized steel sheets were manufactured continuously using a variable automatic control system.

The results are shown in FIG. 5, and FIG. 6 shows an example of an alloyed galvanized steel sheet produced by the conventional visual inspection method.

From Figures 5 and 6, in the conventional manufacturing method, the Fe concentration in the plating fluctuates by up to 20% with respect to the target.
It can be seen that the variation is within 4% in the production method of the present invention.

From this, it is clear that the manufacturing method of the present invention is significantly effective in controlling the degree of peak during plating.

Note that the diffraction angle (20) of a-Fe was 105.8 degrees.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between Fe concentration in plating and processability. FIG. 2 is a graph showing the relationship between Fe concentration in plating and each alloy phase. FIG. 3 is a graph showing the relationship between the Fe concentration in plating and the X-ray diffraction intensity of each alloy phase. FIG. 4 is a graph showing that the measured Fe6 degree value during plating and the actual Fe concentration during plating vary depending on the basis weight. Figures 5 and 6 show (actual Fe concentration in plating)/(Fe concentration in labeled plating) when alloyed galvanized steel sheets were manufactured by the method of the present invention and the conventional method, respectively.
It is a graph showing the change over time. Yo Ishii, the same professional scientist. FIG, I Fe ulcer ('/,) FIG, 2 Fe concentration ('/,) FIG, 3 Fe concentration ('/,) FIG, 4

Claims (2)

[Claims] (1) X-ray diffraction of one or more phases selected from the Fe-Zn alloy phase and metallic zinc, i.e., the η phase, generated in the galvannealed steel sheet by irradiating the galvannealed steel sheet with characteristic X-rays. For one or more phases selected from the Fe-Zn alloy phase and the η phase, each measured value was determined in advance by measuring the strength and simultaneously measuring the count value related to the basis weight. Plating of an alloyed galvanized steel sheet, characterized in that the Fe concentration in the plating is determined by substituting the X-ray diffraction intensity and the measured value of the count related to the area weight as variables into a regression equation in which the Fe concentration in the plating is a function. How to measure medium iron concentration. (2) When manufacturing a galvannealed steel sheet by heat treatment after galvanizing, the galvannealed steel sheet is irradiated with characteristic X-rays to produce Fe-
The X-ray diffraction intensity of one or more phases selected from the Zn alloy phase and metallic zinc, that is, the η phase, is measured, and at the same time, the count value related to the basis weight is measured, and each measured value is calculated in advance. The X-ray diffraction intensity of one or more phases selected from the determined Fe-Zn alloy phase and η phase and the measured value of the count related to the basis weight are used as variables to
Continuously measure the Fe concentration in the plating by substituting the concentration into a regression equation as a function to determine the Fe concentration in the plating,
Measured Fe concentration in plating and preset target Fe
1. A method for manufacturing an alloyed galvanized steel sheet, characterized in that the alloyed galvanized steel sheet is manufactured by comparing the concentration and automatically controlling heat treatment conditions according to the deviation value.