JPH01301155A - Method of measuring degree of alloying of alloyed and galvanized steel sheet by x-ray diffraction method and method of controlling degree of alloying in production line for alloyed and galvanized steel sheet - Google Patents

Abstract

PURPOSE:To non-destructively, continuously and exactly measure the degree of alloying of an alloyed and galvanized steel sheet by corresponding the ratio obtd. by measurement of the X-ray diffraction intensity of only the GAMMA phase of Fe-Zn intermetallic compd. phases to the degree of alloying. CONSTITUTION:The background intensity IBGAMMA at the time of measuring the X-ray diffraction intensity Igamma of the GAMMA phase of the alloy phases is linearly proportional to the plating deposition. The ratio (Igamma-IBGAMMA)Igamma at which the X-ray diffraction intensity (Igamma-IBGAMMA) of the true GAMMA phase occupies in the total X-ray diffraction intensity Igamma is the same regardless of the various values of the plating deposition if the degrees of alloying are the same. The X-ray diffraction intensity IGAMMA of the GAMMA phase and background intensity of the alloyed and galvanized steel sheet are measured and (Igamma-IBGAMMA)/IGAMMA is calculated. The degree of alloying is exactly measured from the same and the previously determined linear recurrence equation of (Igamma-IBGAMMA)/Igamma with respect to the average concn. of Fe in the plating layer.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention uses X-ray diffraction to determine the degree of alloying of an alloyed galvanized steel sheet that is produced by heat treatment after galvanizing to influence the plating thickness. The present invention relates to a method of non-destructively and continuously measuring the degree of alloying without being affected by the process, and a method of controlling the degree of alloying in an alloyed galvanized steel sheet manufacturing line using the method.

[Conventional technology]

BACKGROUND OF THE INVENTION In addition to the corrosion resistance of galvanized steel sheets, alloyed galvanized steel sheets have been produced that have paintability, paint film adhesion, and weldability, and are used in various fields. This alloyed galvanized steel sheet is produced by hot-dip galvanizing, electrolytic galvanizing, or vacuum evaporation galvanizing a steel plate, followed by heat treatment.
Manufactured by alloying a galvanized layer with a steel base.

In this way, when a steel sheet is galvanized and then heat treated, as alloying progresses, Fe and Zn mutually diffuse into ζ phase (FeZr+13) * δ1 phase (FeZ
r+v).

The r-phase (Fe5Zn, □) is sequentially generated and grows in the plating layer toward the surface. Previous research has shown that quality characteristics such as paintability are best when the ζ or δ phase grows to the surface of the plating layer, that is, when the average Fe concentration in the plating layer is 9 to 11 wt%. It is said. The reason for this is that when the average Fs concentration in the plating layer is less than 9%, metallic Zn remains on the surface of the plating layer, resulting in poor paintability, film adhesion, and weldability, and when it exceeds 11wt%, it becomes hard and brittle. This is because the r-phase grows thickly and causes a so-called powdering phenomenon in which the plating layer peels off into powder during processing such as press molding. If this powdering phenomenon is significant,
This not only reduces the corrosion resistance of the plating layer, but also adversely affects processing operations such as press molding. Therefore, it is necessary to control the alloying treatment conditions to obtain an appropriate degree of alloying, that is, an appropriate degree of alloying.

Conventionally, various methods for measuring the degree of alloying have been known as described below.

The simplest method is to visually determine the color tone of the surface of the plated layer immediately after alloying or with a photometer, or to visually determine the amount of the plated layer that has peeled off during a bending/unbending test of a sample sample (so-called powdering test). However, both are inaccurate.

On the other hand, the chemical analysis method that measures the average Fe1 degree in the plated layer of the sample is a preferred method that can accurately measure the average Fe1 degree itself, which represents the degree of alloying.
Since it takes a long time from sampling to completion of measurement,
This has the disadvantage that feedback to the alloying processing equipment is delayed.

As a method for non-destructively and continuously measuring the degree of alloying within a production line, various methods have been proposed in which X-ray diffraction characteristics are used as an index of the degree of alloying of an alloyed galvanized steel sheet. Regarding this X-ray diffraction characteristic, for example, the X-ray diffraction intensity, the measured value varies depending on whether the alloy layer is thick (large amount of plating deposited) or thin, even if the degree of alloying is the same. By the way, in the case of alloyed hot-dip galvanized steel sheets, the amount of plating deposited is controlled by a gas wiping method during the manufacturing process, so the amount of plating deposited may vary in both the sheet width direction and the line direction due to flapping or warping of the steel sheet immediately after hot-dip coating. It fluctuates with.

Therefore, it is desirable that the index of alloying degree using X-ray diffraction characteristics be unaffected by the amount of plating deposited, and various conventional proposals have been based on this idea. many.

For example, in Japanese Patent Publication No. 58-47659, ζ phase, δ, phase, r
One or more of the X-ray diffraction characteristic values, that is, the degree of spread and peak angle of the diffraction intensity 7 diffraction lines for two of the phases, are determined for the two phases, and the ratio is calculated, and this ratio determined in advance. A method is disclosed for determining the level of workability (alloying degree) from the relationship between and workability (alloying degree). In addition, the above-mentioned Special Publication No. 58-47
No. 659 discloses a method for producing an alloyed galvanized iron plate by comparing the ratio of diffraction intensities obtained in the same manner as with a standard set value and automatically controlling the alloying treatment conditions according to the deviation value. Furthermore, in JP-A-61-148355, the lattice spacing is approximately 1.
The diffraction intensity and lattice spacing of 22 r-phase X-rays is approximately 1.4.
The X-ray diffraction intensity of the α-Fe phase of four people was measured, and the average in the plating layer was calculated using the previously determined X-ray diffraction intensity of the r-phase and the X-ray diffraction intensity of the α-Fe phase as variables. A method is shown in which the average Fefi degree in the plating layer is measured by substituting the above two measured values into the Fea degree functional formula. However, since each of the above methods using X-ray diffraction characteristics measures the X-ray diffraction characteristics of two phases, the error in the ratio of the measured values further increases due to the error in each measurement value. In addition, since the method of JP-A-61-148355 measures the α-Fe phase whose crystal plane orientation varies depending on the manufacturing history of the plated steel sheet, alloying There was a problem that the degree could not be measured accurately.

[Problem to be solved by the invention]

The present invention solves the above-mentioned problems of the conventional technology, and measures the degree of alloying of an alloyed galvanized steel sheet non-destructively and continuously within a production line, without being influenced by the amount of coating applied. It is an object of the present invention to propose a method and a method using the method to control the degree of alloying in an alloyed galvanized steel sheet production line.

[Means to solve the problem]

When a galvanized steel sheet is alloyed, the average F in the plating layer
When the a concentration reaches approximately 9 wt%, the r phase begins to form,
As the r-phase grows, the average Fe concentration in the plating layer increases. Further, the Xa diffraction intensity of the r phase increases monotonically with an increase in the average Fe'a degree in the plating layer. The present inventors arrived at these phenomena [1] and, as a result of various studies, found that the background intensity Hp when measuring the X-ray diffraction intensity in the alloy phase is linearly proportional to the coating weight. and the true X-ray diffraction intensity of the phase (Ir-If')
is the proportion of the total X-ray diffraction intensity ■1 (IrIP)/Ir
The above problem was solved by finding out that if the degree of alloying is the same, it is the same regardless of the amount of plating deposited, and by correlating the above ratio obtained by measuring the X-ray diffraction intensity of only the r phase with the degree of alloying. The present invention was completed by discovering that the problem can be solved.

The method of the present invention will be explained in detail below with reference to the drawings.

Figure 1 shows the relationship between the average Fe13 degree and (Iy-Ii')/Ir in the plating layer of an alloyed hot-dip galvanized steel sheet, and Figure 2 shows the relationship between the amount of plating and the background strength BP. Figure 3 is a diagram showing the relationship between the measured value of the average Fa concentration in the blocked layer measured by ICP emission spectrometry and the measured value of the average Fed degree in the blocked layer measured by the method of the present invention. , FIG. 4 is a general illustration of the X-ray diffraction curve of the phase.

First, the principle of measuring (average Fe concentration) in an alloyed galvanized layer according to the present invention will be explained.

X-ray diffraction intensity of F phase ■1 and background intensity 1i
If I is shown together with the peak angle 2θ, the result will be as shown in FIG.

In addition, alloyed melts kA and il! were prepared by alloying hot-dip galvanized steel sheets on a laboratory scale. The X-ray diffraction intensity ■ of the r-phase of the lead-plated steel plate with a lattice spacing of approximately 1.22 mm and the background intensity Hp were measured, and then determined (IrI
FIG. 1 shows the relationship between P)/Ir and the average Fei degree in the plating layer. The average F in the solid line in the fitted layer in Figure 1
e) It is a regression line of (IrJP)/Ir for 4 degrees. Note that a test piece with a diameter of 45 m was used to measure the mechanical strength and HP. In addition, the average Fea degree in the plating layer can be determined by measuring the X-ray diffraction intensity (■) and the background intensity (b) of the F phase as described above, and then immersing the test piece in a 25% concentration HCII aqueous solution. The dissolved solution was analyzed by ICP emission spectroscopy to determine Kl'l. At that time, the plating adhesion amount (therefore, the plating adhesion amount is the total amount of not only Zn but also Fe and AQ and SL in the hot-dip galvanized metal) was measured from the difference in the weight of the test piece before and after dissolving the metal layer. The samples were divided into three groups according to the amount of plating deposited, and the plots in FIG. As shown in Figure 1, the average Fe7 in (Ir IP)/Ir plating layer
A 1 degree relationship is expressed by a single regression line regardless of the amount of plating deposited. Average Fe'a in plating layer
The correlation coefficient of (Ip-Ti')/Ir with respect to degree is 0.98, and (Ir-IBr)/with respect to regression line is 0.98.
The standard deviation value of Ir is 0.02, and the average FO in the plating layer
There is a strong positive correlation between the concentration and (Er-law)/Ir, and the variation range is very narrow. Therefore, by measuring the X-ray diffraction intensity (1) and the background intensity (2) of the r-phase of the alloyed hot-dip galvanized steel sheet,
Calculate rr.

The degree of alloying (average Fe in the plating layer is 71 degrees) can be accurately measured from this and the previously determined linear regression equation of (Tr Ip)/ir for the average Fe concentration in the plating layer.

The following example explains how accurately measurements can be made.

FIG. 3 shows the average F e 'a degree in the test layer determined from (IrrP)/Ir obtained by measuring (IrrP)/Ir and the regression line of FIG. The constant value of K11l (hereinafter referred to as M Fe) and the stent layer determined by immersing and dissolving the test piece in a 25% concentration HCil aqueous solution and analyzing the solution by ICP emission spectrometry after the above measurement. Measured value of average Fe'I3 degree (hereinafter referred to as CFn
), and the straight line is a regression line of MFo against CFe. MF for CFe.

The correlation coefficient is 0.981, and the standard deviation value of M Fe with respect to the regression line is 0.4, and the measured value of the average Fe41 degree in the plating layer by the measurement method according to the present invention is the measured value by ICP emission spectrometry. It is in good agreement with

where r −IF) / average F in the Ir and mating layer
The reason why the relationship with e concentration is expressed by one regression line regardless of the amount of plating deposited is as follows.

The above plating deposition amount (g/m) and background intensity I? It can be seen from FIG. 2, which plots . The reason why there is a linear relationship between the amount of plating and the background intensity IP is presumed as follows. The background intensity ■p is caused by the fact that scattered X-rays from the sample and fluorescent X-rays from the sample are taken into the detector. Of these, scattered
In the line, the scattering stamps of Fe and Zn are almost equal, and when the average Fe concentration in the plating layer is in the range of about 8 to 20%, it does not contribute much to the increase in the background strength tsubo with respect to the increase in the amount of plating deposited. Fe and Zn in the fluorescent X-ray plating layer and F in the steel base
Since the fluorescent X-ray intensity of Fe from the steel substrate is absorbed by the plating layer when passing through the plating layer, it decreases as the amount of plating increases; The intensity of fluorescent X-rays from the layer is less influenced by absorption by the plated layer, and increases as the amount of plating increases. And even more.

The excitation efficiency of fluorescent X-rays is higher for Zn than for Fe;
The mass absorption coefficient when the fluorescent X-rays of Zn are absorbed by Zn is smaller than the mass absorption coefficient when the fluorescent X-rays of Fe are absorbed by Zn, and the main component of the plating layer is Zn. The fluorescent X-ray intensity of Zn in the plating layer is extremely large compared to the fluorescent X-ray intensity of Fe, and these facts combine to increase the amount of plating and increase the background intensity Ijl mainly due to the contribution of Zn fluorescent X-rays. increases linearly.

Furthermore, when the average Fe concentration in the plating layer is the same, the greater the amount of plating deposited, the greater the absolute amount of the r-phase, and the greater the X8 diffraction intensity of the r-phase. However, as the amount of plating increases, the background intensity Hp also increases in a linearly proportional relationship as explained in Figure 2, so the true X-ray diffraction intensity of the phase (Ir tP) including the background intensity tsubo The ratio (Ir II')/Ir of the X-ray diffraction intensity (■) does not change even if the amount of plating is changed.Therefore, the average Fe in the plating layer is
Once the relationship between 'a degree and (Ir - IBr)/Ir is obtained, the coating weight can be determined by measuring the X-ray diffraction intensity Ir and background intensity for only the r phase and calculating the above ratio. Alloying degree can be easily obtained regardless of size.

It is easy to perform such measurement operations non-destructively and continuously at appropriate locations on the front and back of the steel plate in the steel plate running area after alloying treatment in the production line, and it is possible to adjust the conditions for uniformity of the degree of alloying. The operation, that is, the temperature adjustment of the heating furnace for alloying and/or the change of the steel plate threading speed can be carried out immediately.

In addition, when measuring the X-ray diffraction intensity (1) of the r-phase, it was confirmed that similar results could be obtained even if crystal lattice planes of a phase with a lattice spacing other than about 1.22 were used.

In addition, similar results were obtained for the measurement of the average Fe concentration in the alloying degree plating layer of alloyed electrogalvanized steel sheet 1 alloyed vapor deposited galvanized steel sheet produced by heat treatment after plating. The measurement method can be applied to all galvannealed steel sheets manufactured by heat treatment after plating.

〔Example〕

The average Fa concentration in the plating layer was measured using the measuring method according to the present invention in a production line for alloyed hot-dip galvanized steel sheets.6 The measurements of 1 and Ill were carried out under the conditions shown below.

X-ray tube: Cr(Cr-K a , wavelength d = 2
．． 28962 people) Tube voltage: 40KV Tube current: 70mA Divergence slit: 4゜Receiving slit: 4'' Solar slit: 4'' Filter: V Detector: Scintillation counter Grid spacing: Approx. 1.22 people■1 and IP measurements were made at 10 locations and 2 locations on the front and back sides of the alloyed hot-dip galvanized steel sheet in the width direction and line direction, respectively.
0000 locations and obtained (Ir IP) / Tr
The average Fc1 degree at each location in the intertwined layer was determined using a regression line similar to that shown in FIG.

By feeding back the average Fe'a degree in the plating layer determined in this way to the alloying treatment conditions and adjusting the atmospheric temperature of the heating furnace for alloying, the average Fe'a degree in the plating layer can be adjusted.
6. The alloying treatment conditions were controlled so that the concentration was in the range of 9 to 11 wt%. Collect test pieces from both the front and back sides of the
The average Fe concentration in the plating layer was measured by the above-mentioned ICP emission spectrometry.

As a result, 90% of all test pieces were within the range of 9 to 11 wt%. Those outside the range of 9~11νt% are also 8~
It was within the range of 12 wt%. All sampled test pieces were bent and unbended by 180° with a bending radius three times the board thickness, and cellophane tape was pasted on the inwardly bent part and a peel test was performed, then the surface of the plating layer and The cross section was examined using a scanning electron microscope at a magnification of 1000 times [9] to evaluate the powdering resistance of the plating layer. The evaluation criteria are shown below.

1: No change in the plating layer 2: Very slight peeling locally 3: Large rack and local peeling 4: The entire surface of the plating layer peels Evaluation criteria 1 and 2 indicate good powdering resistance, 3 and 4 are determined to be defective products due to poor powdering resistance. Of all the sampled test pieces, 95% of the test pieces met evaluation standards 1 and 2. Paintability.

As a result of investigating coating film adhesion and weldability, only 0.1% of all test pieces were determined to be defective.

〔Effect of the invention〕

As detailed above, according to the measuring method according to the present invention, the plating, which has been conventionally used as an indicator of the degree of alloying, is used in the production line of alloyed galvanized steel sheets that are manufactured by heat treatment immediately after plating. Not only can the average Fe concentration in the layer be measured non-destructively and continuously, but the measurement is also unaffected by changes in the amount of plating deposited due to changes in plating conditions, and only the r-phase is measured. Therefore, it can be measured very accurately.

From the measured value of the average Fe concentration in the plating layer using the measurement method according to the present invention, it was found that by promptly controlling the alloying treatment conditions within an appropriate range, both the front and back sides had excellent quality characteristics such as powdering resistance. Alloyed galvanized steel sheets can be produced.

As a result, conventionally, as a shipping test, test pieces sampled from each coil were chemically analyzed, and the average Fe in the plating layer was
However, by controlling the degree of alloying using the measurement method according to the present invention, sufficient quality control can be performed, and shipping tests can be omitted, which shortens the manufacturing process and saves labor. 1. The measurement according to the present invention not only reduces the manufacturing cost, but also eliminates the need for correction based on the amount of plating and only uses a simple linear function equation in calculating the average Fe concentration in the plating layer. Even when automating the method for controlling the degree of alloying using the method, a small-capacity computing device is required, and the cost required for manufacturing the device is low.

[Brief explanation of the drawing]

Fig. 1 shows the relationship between the average Fe'ffJ degree and (Ir I!')/Ir in the plating layer of an alloyed hot-dip galvanized steel sheet, and Fig. 2 shows the relationship between the plating amount and the background strength T? Figure 3 is a diagram showing the relationship between the measured values of the average Fe concentration in the blocking layer measured by ICI' emission spectrometry and the measurement of the average Fe'a concentration in the blocking layer measured by the method of the present invention. FIG. 4, a diagram showing the relationship between values, is a general explanatory diagram of the X-ray diffraction curve of the r phase. Patent applicant Nisshin Steel Co., Ltd. - 'l''・-,・' (Ir-Ir)/l "Background 5 button boat C (X100 c, p, s,)
Figure 3 Base (ICP photoreception analysis method 4° diagram, I 2θ (cliff)

Claims (1)

[Claims] 1 From the X-ray diffraction intensity (I_r) of the Γ phase of the Fe-Zn intermetallic compound phase of the alloyed galvanized steel sheet and the background intensity (I^B_r), (I_r-I^ B_r)
A method for measuring the degree of alloying of an alloyed galvanized steel sheet using an X-ray diffraction method, characterized in that the degree of alloying is measured by calculating /I_r. 2 Fe-Zn in alloyed galvanized steel sheets that have been alloyed and run on the alloyed galvanized steel sheet production line
X-ray diffraction intensity (I_r) of Γ phase among intermetallic compound phases
and the background intensity (I^B_r) are measured non-destructively and continuously, and from the measured values (I_r - I^B_r)
1. A method for controlling the degree of alloying in an alloyed galvanized steel sheet manufacturing line, the method comprising: calculating /I_r, and adjusting alloying treatment conditions so that the calculated value falls within a predetermined value range.