JPH0712761A - Determination method for upper layer plating of steel plate having multilayer of alloyed and fused galvanization - Google Patents

Abstract

PURPOSE:To precisely measure the deposited amount of an upper galvanized layer and an iron content via a nondestructive process, regarding a steel plate having a multilayer of allayed and fused galvanization. CONSTITUTION:A monochromatic characteristic X-ray is made incident on the surface of a steel plate having a multilayer of alloyed and fused galvanization at an incident angle equal to or above six times but equal to or less than 12 times Ra of the steel plate. The diffraction peak intensity and background intensity of the X-ray are measured to find an intensity difference. Then, the deposited amount of upper layer plating is calculated on the basis of the difference. Furthermore, the X-ray diffraction peak angle of the upper layer plating is measured, and an angular difference from the X-ray diffraction peak angle of pure iron is obtained, thereby calculating the iron content of the upper layer plating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention, in order to improve corrosion resistance, slidability, chemical conversion treatment property, and electrical property, applies galvannealing to the surface of a steel sheet, and Fe-Zn based plating to the upper layer. The present invention relates to a method for measuring the coating weight of the surface layer and the Fe content in the so-called multilayer galvannealed steel sheet.

[0002]

2. Description of the Related Art Generally, galvannealed steel sheets are widely used as steel sheets having excellent corrosion resistance, but the reason is that the manufacturing cost is lower and the weight per unit area can be higher than that of galvannealed steel sheets. Due to this, alloyed hot-dip galvanized steel sheets are widely used.

Further, in recent years, for the purpose of improving slidability, chemical conversion treatment property, or electrodeposition property, a multi-layer alloy hot-dip galvanized steel sheet having an Fe system as the uppermost layer of the hot-dip galvanized steel sheet is used. Has been done.

By the way, the basis weight of the upper layer Fe-based plating or the upper layer Fe in this multi-layer galvannealed steel sheet
Since the content greatly affects slidability, chemical conversion treatment, and electrodeposition, it is necessary to strictly control the basis weight of the upper layer plating or its Fe content.

Conventionally, the plating composition of the multi-layer galvanized steel sheet including the above-mentioned multi-layer galvannealed steel sheet has been measured as follows. That is, the upper and lower layer separation points were calculated by GDS, and the upper layer plating composition was quantified from the integrated strength, or the plating film was dissolved at a constant current, and the plating composition was quantified from the dissolution time and the like.

However, the conventional measuring method as described above is
Since it is a destructive test method, it is strongly affected by lower layer plating.

Therefore, this fracture test method is effective only when the composition is constant in the plating depth direction, such as an alloyed electroplated steel sheet, and particularly when the plating composition of the lower layer is constant in the depth direction. is there.

However, in the galvannealed steel sheet, after hot dip galvanizing the steel sheet base material, it is heated in an alloying treatment furnace at, for example, about 600 ° C. And a Fe-Zn alloy layer is formed.

For this reason, the Fe concentration of the surface portion of the plating film is low, and the Fe concentration increases as it goes to the inner portion. Therefore, even if the Fe content (alloying degree) of the entire plating film is the same, the Fe content of the outermost layer is significantly different.

As a result, according to the conventional destructive test method affected by the plating composition of the lower layer, when the upper layer plating composition of the multi-layer galvannealed steel sheet is quantified, the measurement variation becomes large and the quantification accuracy is low. turn into.

Further, in the destructive testing method, since a stable standard sample is required, there is a problem that it is difficult to maintain and manage the analysis accuracy for each measurement opportunity.

Therefore, in order to measure multi-layer plating nondestructively, the following methods using fluorescent X-rays have been disclosed. JP-A-59-195146: A method for measuring upper and lower layer plating compositions by injecting fluorescent X-rays at a high angle and a low angle for the purpose of comparing lower layer and upper layer plating and measuring fluorescent X-rays. Japanese Patent Laid-Open No. 61-132847; A method of utilizing the fluorescent X-ray intensity of L series, which has a shallow depth of penetration information into the plating film, for measuring the upper layer plating composition. Japanese Patent Application Laid-Open No. 2-302654; When X-rays are incident at a low angle and a high angle, the best matching X is obtained from the measurement intensities of known standard samples.
A method of calculating the composition ratio of the upper and lower layers by calculating the line intensity ratio.

[0013]

In each of the methods disclosed in the above publications, the composition of the lower alloy plating layer is not constant in the depth direction, and in particular, the Fe content on the lower surface is not constant. In a hot-dip galvanized steel sheet, the amount of information from the lower layer causes variations in the measured fluorescent X-ray intensity, resulting in poor measurement accuracy and poor reliability.

Therefore, a main object of the present invention is to accurately quantify the coating weight and the Fe content of the upper plating layer in a multi-layer galvannealed steel sheet without being affected by the composition of the lower plating. is there.

[0015]

The first invention, which has solved the above-mentioned problems, is a multilayer alloy of a double-layer plated steel sheet having an alloyed hot-dip galvanized layer on a steel sheet, and further having an Fe-based plated layer on the upper layer. A method for measuring a basis weight of an upper Fe-based plating layer in a chemical-dip galvanized steel sheet, comprising:
The characteristic X-rays that are monochromatic are made incident on the surface of the multi-layer alloy hot-dip galvanized steel sheet at an incident angle β of 6 times or more and 12 times or less of the center line average roughness Ra of the surface of the system-plated layer, and the upper layer plating The X-ray diffraction peak intensity I _Fe and the background intensity I _FK are measured, the intensity difference I _UP between them is determined, and the correlation is checked in advance with the correlation between the intensity difference and the basis weight of the upper Fe-based plating layer, A coating weight measuring method for the upper layer plating of a multi-layer galvannealed steel sheet, which is characterized in that the coating weight of the upper Fe-based plating is calculated from the measured strength difference I _UP .

The second invention is an upper layer Fe-based plating in a multi-layer alloyed hot-dip galvanized steel sheet of a double-layer plated steel sheet having an alloyed hot-dip galvanized layer on the steel sheet and further having an Fe-based plated layer on the upper layer. A method for measuring the basis weight of a layer, wherein the characteristic X-ray monochromatized at the incident angle β of 6 times or more and 12 times or less of the centerline average roughness Ra of the surface of the upper Fe-based plating layer is used for the multilayer alloy. X-ray diffraction peak angle 2 of the upper layer plating by making it incident on the surface of the galvanized steel sheet
The angle difference Δ2θ between the X-ray diffraction peak angle 2θ _Fe peculiar to the upper Fe-based plating and the X-ray diffraction peak angle 2θ _{Fe0 of} pure Fe, which was previously determined by measuring θ _Fem , the upper-layer Fe-based plating basis weight, and the upper layer Correlation with the Fe content, the angle difference Δ2θ _m based on the measured X-ray diffraction peak angle 2θ _Fem , and the upper layer Fe content is obtained, and the upper layer plating of the multi-layer alloy hot-dip galvanized steel sheet is characterized. This is an Fe content measuring method.

[0017]

As described above, in the case of the multi-layer alloy hot-dip galvanized steel sheet, the measuring method based on the fluorescent X-ray intensity has a large variation, and therefore another measuring method was considered. As a result, they have found that an X-ray diffraction method that can utilize the difference in the alloy phase structure between the upper layer and the lower layer is effective.

The present invention will be described below together with its elements. (1) X-ray incidence angle The upper alloy phase in the multi-layer galvannealed steel sheet is F
Since it is an e-based plating, it is not preferable to receive information on the underlying Fe that is the plating base material, and it is desirable to make X-rays incident at a low angle that does not pick up the underlying Fe information.

However, since the alloy phase structure of the lower alloyed hot-dip galvanized coating and the alloy phase structure of the upper Fe-based plating are completely different, the incident light is necessarily incident at an extremely low angle for picking up only the upper layer plating composition information. There is no need. The point is that the incident angle should be set so that the information of Fe of the base material is not picked up.

In the galvannealed steel sheet, in addition to the irregularities of the steel sheet itself, irregularities of the plating itself due to the local difference in the alloying growth rate are added.

Therefore, when Fe-based plating is performed on the Fe-Zn alloy plated layer, irregularities naturally occur.

Therefore, in order to know the incident angle of the base steel sheet which is not affected by Fe, the appropriate range of the X-ray diffraction incident angle was measured for each of the multi-layer alloy hot-dip galvanized steel sheets having different irregularities. As a result, the base F
It was found that the X-ray diffraction incident angle β that does not pick up the information of e largely depends on the surface roughness of the upper Fe-based plating, particularly Ra (center line average roughness) thereof.

By the way, what is actually required as the galvannealed steel sheet is in the range of 30 to 70 g / m ² as the coating weight of the galvannealed layer and 7 to 14% as the degree of alloying. It is a thing.

Therefore, the surface roughness of the multi-layer alloy hot-dip galvanized steel sheet within this range was measured, and the X-ray incident diffraction angle β which did not pick up the influence of Fe as the base was measured. as a result,
It has been found that if the range of β is Ra × 6 ≦ β ≦ Ra × 12, it is possible to quantify with high accuracy and high reliability.

If β is less than Ra × 6, the X-ray incident diffraction angle is too small to provide information on the underlying Fe, but the information on the upper Fe-based plating cannot be sufficiently picked up. The measurement accuracy is not stable because the diffraction intensity is not sufficient.

On the other hand, when β is larger than Ra × 12, although the information of the upper Fe-based plating is sufficiently collected, the effect of Fe of the underlayer comes out strongly, and the peak strength peculiar to the upper-layer plating,
The diffraction angle is affected by the underlying Fe, resulting in a shift. Therefore, the range of β was limited as described above. A more preferable range of β is Ra × 8 ≦ β ≦ Ra × 10.

When X-rays are incident at a low angle,
It is preferable to use slits for incident X-rays and diffracted X-rays and use parallel X-rays. Further, although it is a mode that is difficult to apply online, in the measurement of offline, while eliminating the influence of the preferential orientation of the surface, the sample surface is averaged, the analysis accuracy is improved,
It is preferable to rotate the sample in-plane.

Since the incidence with the low incidence angle β is sufficiently possible if the pass line of the strip is sufficiently stabilized, it can be applied for online measurement.

On the other hand, in the present invention, the basis weight of the upper Fe-based plating layer is quantified based on the surface roughness of the upper Fe-based plating layer. Since it is difficult to perform this analysis of the surface roughness online, usually, the surface roughness of the base metal that can be measured in advance, the alloying degree of the galvannealed steel sheet,
It is also possible to make predictions based on the skin pass condition and the like, and even with this predicted value, it is possible to obtain sufficiently valid accuracy. Therefore, based on this predicted surface roughness, X It is quite possible to set the incident angle of the line.

(2) Measurement of coating weight of upper layer Since the intensity of Fe-based plating diffraction peculiar to the upper coating has a correlation with the coating weight of the upper layer, Ra × 6 ≦ β ≦ Ra × 12
By measuring the diffraction intensity of the upper layer plating by making the X-ray incident within the range, it is possible to measure the adhesion amount of the upper layer plating having a different Fe content in a fairly wide range.

The coating amount of the upper layer, which is required from the performance of the product formed on the multi-layer galvannealed steel sheet, is
It is about 2.5 to 5.0 g / m ² . The reason for this is as described below. When the coating weight of the upper layer is less than 2.5 g / m ² , the effect of improving the slidability, chemical conversion treatment property, and electrodeposition property by applying the upper layer plating becomes insufficient. On the other hand, when the coating weight of the upper layer exceeds 5.0 g / m ² , workability deterioration due to poor powdering or electrodeposition failure due to poor workability occurs due to peeling of the upper layer plating during processing by applying the upper layer plating. Because of that it becomes a cause. Further, since a micro battery is formed from the potential difference between the upper layer and the lower layer, and corrosion is likely to proceed, it depends on the corrosion resistance, especially the upper Fe-based plating thickness, red rust is likely to occur, and external rust resistance is also a problem. Furthermore, when the upper Fe-based plating thickness is large, there is a cost problem and it is not preferable from the economical viewpoint.

Therefore, as the upper layer plating basis weight measuring range in the present invention, as shown in FIG. 3 which will be described later, which covers the practical basis weight range, it is 1.5 to 7.0 g / m 2.
^A reasonableness in ² is considered sufficient. Therefore, as a result of the measurement experiment, the X-ray diffraction peak intensity I _Fe peculiar to the upper layer plating is within the above-mentioned weight measurement range.
And the background intensity I _BK , the diffraction peak intensity I _UP (= I _Fe −I _BK ) of the upper Fe-based plating substance is
It was found that there was a very good linear relationship within the range of Ra × 6 ≦ β ≦ Ra × 12.

Therefore, the relationship between the substantial diffraction peak intensity I _UP of the upper Fe-based plating of the standard sample and the basis weight is obtained in advance to form a calibration curve, and the diffraction peak intensity of the upper Fe-based plating is measured and collated with this calibration curve. Then, the coating weight of the upper layer of the multilayer galvannealed steel sheet can be calculated.

The coating weight of the upper layer is 1.5 g / m ²
If it is less than the above, the diffraction peak peculiar to the upper Fe-based plating is unclear, and the strength measurement becomes difficult. On the other hand, when the amount of the deposited upper layer plating is larger than 7.0 g / m ² , the diffraction peak intensity tends to be saturated. As a result, when the coating weight of the upper layer is too thick, it is necessary to increase the set value of the X-ray incident angle, and it is necessary to greatly change the diffraction angle beyond the set angle range according to the present invention. Therefore, it becomes difficult to measure with high accuracy.

(3) Measurement of Fe content in upper Fe-based plating In the case of Fe-rich upper Fe-based plating, the diffraction peak angle and the diffraction peak angle of pure Fe are almost the same.
A slight deviation occurs in the diffraction peak angle between the e-based alloy plating and pure Fe. Further, as a result of the measurement experiment, it was found that there is a correlation between the deviation of the diffraction peak angle, the Fe coating amount of the upper Fe-based coating, and the Fe content of the upper Fe plating.

On the other hand, the Fe content (Fe%) required for the upper Fe-based plating formed on the multi-layer alloy hot-dip galvanized steel sheet is about 75- though it depends on the product performance.
It is about 85%. The reasons are as follows. That is, if the upper layer Fe% is too low, the effect of improving the slidability, chemical conversion treatment property, and electrodeposition property by applying the upper layer plating is insufficient, which is not preferable. On the other hand, the upper layer F
If e% is too high, unevenness of the upper layer plating is likely to occur. Alternatively, there is also a problem of plating operability that the current efficiency during electrodeposition is lowered, which is not preferable. Therefore, in the present invention, the target Fe content range showing high measurement accuracy is as follows.
It is considered that 70 to 95% is sufficient.

When the upper layer Fe% is less than 70%, the diffraction peak peculiar to the upper layer Fe-based plating becomes broad (blunt), and the diffraction peak becomes unclear, which is not preferable. Further, when such Fe% upper layer plating is applied, the amount of the upper layer basis weight obtained by obtaining the diffraction peak intensity is substantially reduced,
This lowers the measurement accuracy of the upper layer areal weight. On the other hand, upper layer Fe%
Can be measured even at 100%. In any case, it is possible to measure with high accuracy within the range of the upper layer plating Fe% required for product performance.

In any case, the X-ray diffraction peak angle 2θ _Fe peculiar to the upper Fe-based plating, the deviation Δ2θ (= 2θ _Fe -2θ _FeO ) of the X-ray diffraction peak angle 2θ _FeO of pure Fe and the upper-layer basis weight are There is a correlation between the relationship and the upper layer Fe%.

Therefore, in the known sample, the upper layer F
The diffraction peak angle is obtained by scanning the X-ray detection angle in the extremely short range of e-based plating and at the same time obtaining the peak intensity and diffraction angle, and the correlation between the upper-layer basis weight and the deviation of the diffraction peak angle and the upper-layer Fe% is calculated. The upper layer Fe% can be determined by measuring the diffraction peak intensity and the diffraction peak angle of the upper layer Fe-based plating, which have been obtained in advance by the multiple regression equation, and by collating with this multiple equation. In addition,
The reason why the diffraction peak angle shifts depending on the Fe% of the sample is not clear, but it is considered that the crystal lattice strain in the plating increases and changes depending on the Fe% of the upper layer and the attached amount.

It is needless to say that the method of the present invention can be applied even to a multi-layer alloy electrogalvanized steel sheet having a uniform lower layer plating composition. Further, the upper layer plating in the present invention includes Fe-Zn type, Fe-P type, Fe-B type and the like.

[0041]

EXAMPLES The effects of the present invention will be specifically described below with reference to examples. In order to clarify the effect of the present invention, after degreasing various alloyed hot-dip galvanized steel sheets produced on an actual plating line, upper layer plating is performed with the plating solution composition shown in Table 1 and each basis weight shown in Table 2 , A multi-layer alloy hot-dip galvanized steel sheet having a degree of alloying and Ra was prepared.

[0042]

[Table 1]

[0043]

[Table 2]

With respect to each of the above upper layer plating compositions, the upper layer areal weight is determined by changing the energization time.
The e% was adjusted by changing the ZnSO ₄ .7H ₂ O concentration.

In order to quantify the plating composition of the upper layer,
In a multi-layer alloy hot-dip galvanized steel sheet, it is difficult to quantify only the upper layer plating composition.
With respect to the one subjected to the system plating, the one in which the plating film was dissolved was chemically analyzed to obtain the upper layer plating composition.

The coating weight of the upper layer and the Fe content were measured. The measurement conditions are shown below. X-ray tube; Co-Kα (wavelength d = 1.78892
Å) Tube voltage; 30 kV tube current; 200 mA monochromator; used for monochromation Diversity Slit; 0.50 mm Scattering Slit; 3.00 mm Receiving Slit; 3.00 mm Sample rotation speed; 180000 deg / min scintillation detector upper; Plating measurement lattice plane spacing; d = 2.0611 to 2.0
268Å (2θ _UP = 51.4 to 52.4 °) Pure Fe (110) lattice spacing = 2.02680Å (2θ
_FeO = 52.38 °) The measurement results are shown below. <Result 1> In FIG. 1, the upper layer plating (area weight = 2.5 g / m
² , Fe% = 70%), the relationship between the X-ray incident angle, the upper layer plating strength, and the Fe strength of the base is shown. From this figure, even if the incident X-ray angle β changes, the upper layer plating strength difference I _UP
Is stable, and β suitable for measurement that picks up information only on the upper layer plating
It turns out that the range of exists.

<Result 2> The following alloyed hot-dip galvanized steel sheet was subjected to upper layer plating (area weight = 3.0 g / m ² , F
The relationship between the surface roughness of the sample and the measurable X-ray incident angle is shown in FIG. From FIG. 2, when the basis weight is large, the measurable X-ray incident angle tends to be slightly widened, but the β range that can be measured can be arranged by the center line roughness Ra when the entire manufacturing range is taken into consideration. It can be seen that the lower limit value of β is Ra × 6, and the upper limit value is Ra × 12.

<Result 3> Next, the basis weight of the upper layer and the strength difference I _UP
The relationship is shown in FIG. Ra of the lower layer galvannealed steel sheet was 1.2 μm, and the X-ray incident angle β was fixed at 10 °. In that case, the coating weight of the upper layer is 0.5 g / m ² to 1
Up to 0.0 g / m ² , the upper layer Fe% is 60, 7
It was changed to 0, 80, 90 and 100%. From FIG. 3, when the upper layer Fe% is 70% or more, the upper layer areal weight is 1.5 to 7.0.
It can be seen that a good correlation is recognized in the range of g / m ² .

<Result 4> FIG. 4 shows the relationship between the upper layer plating diffraction peak angle and the pure Fe diffraction peak angle deviation Δ2θ from the same sample. If the basis weight is constant, Δ
It can be seen that there is a good correlation between 2θ and Fe% in the upper layer. Therefore, the upper layer Fe% can be obtained from Δ2θ by obtaining the upper layer areal weight from the intensity difference I _UP .

From the above results, by preparing a calibration curve of a standard sample, the X-ray incident angle is set within the range of Ra × 6 ≦ β ≦ Ra × 12, and the strength of the upper layer plating is set at this X-ray incident angle. By obtaining the difference I _UP and Δ2θ, the upper layer F
It is understood that it is possible to determine the amount of Fe-based plating deposited and the Fe%.

[0051]

As is apparent from the above description, according to the present invention, by using the X-ray diffraction method, the upper layer plating in the multi-layer alloy hot-dip galvanized steel sheet is not affected by the composition of the lower layer plating. Area coating weight and Fe
It is possible to measure the content rate accurately by non-destructive.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between upper layer plating peak intensities when an X-ray incident angle is changed.

FIG. 2 is a diagram showing a relationship between an optimum X-ray incident angle range and surface roughness.

FIG. 3 is a diagram showing a relationship between an upper layer plating basis weight and an upper layer plating diffraction peak intensity difference.

FIG. 4 is a diagram showing a relationship between a deviation between an upper layer plating diffraction peak angle and a pure Fe diffraction peak angle and an upper layer Fe%.

Claims (2)

[Claims] 1. A galvanized galvanized layer on a steel sheet,
A method for measuring a basis weight of an upper Fe-based plating layer in a multi-layer alloy hot-dip galvanized steel sheet of a double-layer plated steel sheet having an Fe-based plating layer as an upper layer thereof, wherein the center line average of the surface of the upper Fe-based plating layer is measured. Roughness Ra 6
Characteristic X that is monochromatic at an incident angle β of not less than 2 times and not more than 12 times
A line was made incident on the surface of the multilayer galvannealed steel sheet, the X-ray diffraction peak intensity I _Fe and the background intensity I _FK of the upper layer plating were measured, and the intensity difference I _UP between them was determined, An upper layer of a multi-layer alloy hot-dip galvanized steel sheet, characterized in that the basis weight of the upper Fe-based plating is calculated from the measured strength difference I _UP by checking the correlation between the strength difference and the basis weight of the upper Fe-based plating layer. Method for measuring coating weight of plating. 2. A galvannealed layer on a steel sheet,
A method for measuring a basis weight of an upper Fe-based plating layer in a multi-layer alloy hot-dip galvanized steel sheet of a double-layer plated steel sheet having an Fe-based plating layer as an upper layer thereof, wherein the center line average of the surface of the upper Fe-based plating layer is measured. Roughness Ra 6
Characteristic X that is monochromatic at an incident angle β of not less than 2 times and not more than 12 times
The X-ray diffraction peak angle 2θ _Fe specific to the upper Fe-based plating and the pure X-ray diffraction peak angle 2θ _Fe obtained by measuring the X-ray diffraction peak angle 2θ _Fem of the upper layer plating by irradiating the surface of the multilayer alloyed hot-dip galvanized steel sheet surface The angle difference Δ2θ from the X-ray diffraction peak angle 2θ _{Fe0 of} Fe, the upper-layer Fe-based plating basis weight, and the correlation of the upper-layer Fe content with the measured X-ray diffraction peak angle 2θ _Fem
A method for measuring the Fe content in the upper layer plating of a multi-layer galvannealed steel sheet, wherein the upper layer Fe content is determined by matching the angle difference Δ2θ _m based on the above.