JPS6259844A - Method for measuring degree of alloying of alloyed and hot dip zinc coated steel sheet - Google Patents

Abstract

PURPOSE:To measure the degree of alloying with high accuracy over a wide range by measuring the peak intensity or diffraction intensity of the diffraction rays with the two different index plane at a delta1-FeZn7 phase and determining the degree of alloying in accordance with the measured value thereof. CONSTITUTION:X-rays are projected on an alloyed and hot dip zinc coated steel sheet and the peak intensities of the diffraction rays at d=2.419Angstrom and d=2.398Angstrom of the detected diffraction rays are measured. The ratio between both measured values is determined. The diagram indicating the relation among the content of Fe in the plating layer, an alloying treatment temp. and the peak intensity of the diffraction ray is preliminarily formed. The content of Fe in the plating layer is calculated in accordance with the value of the ratio between both measured values and the formed diagram. The degree of alloying is thus measured with the high accuracy regardless of the degree of alloying.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for measuring the degree of alloying of an alloyed hot-dip galvanized steel sheet with high accuracy regardless of the degree of alloying.

[Prior art]

In the continuous hot-dip galvanizing process, a heating furnace is installed at the top of the plating tank to change the structure of the plating layer on the steel plate into Fe-Z
The so-called alloying process, which involves diffusion transformation to form a total compound of n, is widely used, and alloyed hot-dip galvanized steel sheets are produced by this process.

Such alloyed hot-dip galvanized steel sheets are weldable.

Although it has excellent properties in terms of compatibility with the coating film, the alloyed plating layer is an intermetallic compound with low ductility, so when drawing or compressive deformation is applied, the plating layer becomes powdered. It has the disadvantage of being prone to intralayer peeling and destruction.

The occurrence rate t of the powdering described above mainly depends on the degree of alloying of the plating layer, that is, the average Fe content in the plating layer, and the AI in the plating layer! quantity, plating layer thickness.

It has been known that this depends on secondary factors such as the alloying temperature.

In order to prevent powdering, it is better to have a lower degree of alloying as long as the alloying temperature is constant, so it is necessary in the process to suppress and manage the degree of alloying to the required level. . For this reason, a method has been proposed that uses X-ray diffraction to measure the intensity of diffraction lines in intermetallic compounds or appropriate strengthening as a means of measuring the degree of alloying (Japanese Patent Publication No. 56-33464, Japanese Unexamined Patent Publication No. 59/1989). -46543)
.

[Problem that the invention seeks to solve]

By the way, according to the results of investigation by the present inventors, the plating layer of the alloyed hot-dip galvanized steel sheet manufactured by the above process has a δ1 phase when the average Fe content in the plating layer is 10 to 14%. It has been found that if the alloying treatment is insufficient, the δ1 phase + i phase (Zn phase) is formed, and if the alloying treatment is excessive, the δ1 phase + r phase (or cubic compound) is formed. Judging from the phase diagram of the Fe-Zn system, the ζ phase should be formed during the alloying process, but in reality, the ζ
Phases are rarely detected. This is because the upper limit temperature at which the ζ phase exists is around 480°C, and the ζ phase is generated.
The alloying treatment conditions are temperature: 480°C, 9 hours: 30~
This is because it requires about 60 seconds, and such conditions cannot be realized on a general manufacturing line that emphasizes productivity.

The measurement method of the above-mentioned Japanese Patent Publication No. 56-33464 is based on the diffraction intensity of the ζ phase of the crystal lattice spacing d=1.26 and the
This is a method to measure the degree of alloying in alloyed galvanized steel sheets that are alloyed at temperatures below 480°C, where the ζ phase appears. Although it seems to be effective for measurement, the S/N of the diffraction line of the ζ phase of d=1.26 is small for those subjected to practical alloying treatment at 480° C. or higher, which poses a problem in terms of measurement accuracy.

Moreover, the measurement method of JP-A No. 59-46543 is d=2
．． Diffraction intensity r of 61 phases for 14 people (d=2.14 people)
and the diffraction intensity r of the η phase of d=2.09 people (d=2.0
9 people) ratio 1 (d=2.14 people) / I (d
= 2.09 people), and it is possible to measure unalloyed materials where the η phase remains, but it is difficult to measure when the Fe content in the plating layer is 10% or more. In this case, as shown in FIG. 5, the above ratio becomes a substantially constant value and becomes impossible to measure. There is also a problem with the interpretation of the diffraction line of a person with d=2.09.

That is, in this method, "C interprets the diffraction line of d = 2.09 person as that at η (101), and I (d
= 2.14 people) / I (d = 2.09 people) shows a nearly constant value when the Pe content is between 10 and 17%, and is about 4
Therefore, in this case, the η phase will exist up to a considerably excessive alloying state. However, according to the knowledge of the present inventors, δ1 (24・1) and η (10−1
) diffraction lines overlap °ζ, d=2.09
The human diffraction line is η (10・1) for materials with low alloying degree.
However, when the Fe content in the plating layer was 10
% or more of the material exhibits a diffraction line of δI (24-1), and therefore this method lacks consistency in theoretical points.

As described above, since the conventional method uses the diffraction intensity ratio of two types of phases, its applicable range is narrow or the measurement accuracy is low, and even offline measurement is impractical.

[Means for solving problems]

The present invention has been made in view of the above circumstances, and uses the diffraction intensity ratio of two different index planes of the δ1 phase, which is the main phase of the plating layer of a practical product, to vary the degree of alloying over a wide range. The purpose of this invention is to provide a method for measuring the degree of alloying of an alloyed galvanized steel sheet that can be measured with high accuracy.

The method for measuring the degree of alloying of an alloyed hot-dip galvanized steel sheet according to the present invention is to measure the degree of alloying of an alloyed hot-dip galvanized steel sheet, which is obtained by subjecting a hot-dip galvanized steel sheet to alloying treatment and alloying the plating layer, using an X-ray diffraction method. In the method of measuring δ, -FeZ
It is characterized by measuring the peak intensity and/or diffraction intensity of diffraction lines on two different index planes in the n7 phase, and determining the degree of alloying based on the measured values.

〔Example〕

The present invention will be specifically explained below. When an alloyed hot-dip galvanized steel sheet is irradiated with X-rays (in this case, CO), multiple diffraction lines as shown in Figure 1 are detected, among which d = 2.
．． δ of 419 people, peak intensity of diffraction line at (14・0) 1 (d・2.419 people) and δ of d-2,398 people
, (14・3), the peak intensity of the diffraction line l(d・2
．． 398 people), and the ratio of remeasured values I (d=2
．． 419 people) / I (d=2.398 people). In FIG. 1, the horizontal axis shows 2θ (degrees) and d (person), and the vertical axis shows the intensity of the diffraction line.

By the way, δH-FeZn7, which is generally formed in the coating layer of alloyed hot-dip galvanized steel sheets, does not have a specific preferred orientation, that is, it shows a profile close to the diffraction of powder crystals. A slight change in orientation has occurred.

Therefore, the ratio I (d=2.419 people)/I
(d-2,398 people), the Fe content in the plating layer, and the powdering amount have the relationships shown in FIGS. 2 and 3, respectively.

In Figure 2, the horizontal axis is I (d・2.419 people) / I (d
= 2.398 people), and the vertical axis is the Fe content (wt%) in the plating layer, and the graph shows the relationship between the two according to the alloying treatment temperature. show the measurement results when the alloying treatment temperatures were 600°C, 550°C, and 500°C, respectively. Note that the alloyed hot-dip galvanized steel sheet is obtained by plating a steel sheet with a thickness of 0.4 fin with 42 g/la2 of Zn per side, and then subjecting it to alloying treatment. The conditions for X-ray diffraction are: target: Co, filter: Fe.

X-ray tube voltage: 30, X-ray tube current: 100
mA.

The rotation speed of the goliometer was 2 dag/min, and the Fe content in the plating layer was determined using the results of melting the plating layer with hydrochloric acid containing an inhibitor and then analyzing it by atomic absorption spectrometry.

As can be understood from this figure, the larger the value of the ratio I (d=2.419 people)/I (d=2.398 people), the more
The degree of alloying increases at a similar rate. In other words, the value of this ratio indicates a change in the line shape according to a change in the Fe content in the plating layer.

In Figure 3, the horizontal axis shows I (d=2.419 people) / I (
d = 2.398 people), and the powdering amount (l
This is a graph showing the relationship between the two by changing the alloying temperature, and the *, O, and ○ marks are measurements taken at alloying temperatures of 600°C, 550°C, and 500°C, respectively. Show the results. The amount of powdering was measured by punching out a 601 mφ circular test piece from an alloyed hot-dip galvanized steel plate and drawing it into a cylinder until the flat bottom diameter was 26 mm and the flange width was approximately 0. This is done by peeling off the plating layer on the side of the molded product using adhesive tape and changing the weight of the molded product.

As can be understood from this figure, when alloying is performed at high temperatures, that is, when diffusion occurs at high speed, F in the same plating layer
Even at the e content, the powdering resistance is lower than when alloying is performed at a low temperature.

Therefore, if the alloying temperature and the relationship shown in FIG. 2 are known, in the case of the present invention I (d-2,419
By determining the Fe content in the plating layer, that is, the degree of alloying, regardless of the degree of alloying, it is possible to measure the Fe content in the plating layer with high accuracy, regardless of the degree of alloying. If the relationship shown is known, the powdering characteristics can be determined.

In addition, in the above example, d = 2.419 people δ1 (14
Although the two diffraction intensities are measured at 0) and δ1 (14.3) of d = 2.398 people, the present invention is not limited to this, as the orientation changes as described above. Changes are relatively noticeable d = 2.554 Å ~ 2.31
It goes without saying that this can also be carried out by measuring the diffraction intensity on two planes having a spacing of 8 people. For example d=2.4
δl (14・0) of 19 people and δ of d = 2.347 people
1 (↓4・6) and a method of measuring the peak intensities of the diffraction lines and calculating the ratio of the remeasured values may be used.

FIG. 4 is a graph showing the relationship between the ratio determined by the above method and the Fe content in the plating layer, where the marks ・, ▪, and Q indicate the base metal forming treatment temperature of 600°C, respectively. , 550
The measurement results at 500°C and 500°C are shown. As can be understood from this figure, the value of the ratio increases with the increase in the degree of alloying of the plated layer, and this ratio is affected by the alloying temperature as before, so when using this method, The degree of alloying and powdering properties can also be measured in the same way as before.

In the above explanation, the degree of alloying, etc. is detected by measuring the ratio of peak intensities of diffraction lines, but the present invention is not limited to this, and it goes without saying that the present invention can also be carried out by measuring the ratio of integrated intensities of diffraction lines. It is.

Furthermore, the present invention is not limited to δ and (hki) as explained above, but can be similarly implemented by measuring the peak intensity or integrated intensity of the diffraction line at other surface indices. For example d = 2
．． The area index corresponding to 542 people is (23・O), (2
3.l), (23.2), (04.9), etc., and the plane index in the above explanation is a relatively low-order plane index among the plurality of plane indexes.

As it is known that δ and the crystal plane spacing d of the phase vary slightly depending on the heat treatment conditions 1 and the degree of alloying, the d values shown in this specification are ±0.005 to ±0. 01
It is accompanied by fluctuations in people.

〔effect〕

As detailed above, in the case of the present invention, δ1-FeZ, which is the constituent phase of the plating layer of the alloyed hot-dip galvanized steel sheet,
The ratio of the peak intensity or integrated intensity of the diffraction lines on different planes in the n7 phase is determined, and the degree of alloying is measured based on the determined value and the relationship between the ratio determined in advance and the degree of alloying. Regardless of the degree of alloying, it is possible to measure the degree of alloying over a wide range and with high precision, and it can also be determined in advance.
The present invention has excellent effects such as being able to determine powdering characteristics based on the relationship between the recording ratio and the amount of powdering.

[Brief explanation of drawings]

Figure 1 is a diffraction line detection chart, Figures 2, 3, and 4.
The figure is a detailed explanatory diagram of the present invention, and FIG. 5 is an explanatory diagram of problems in the prior art.

Claims (1)

[Claims] 1. The alloying degree of an alloyed hot-dip galvanized steel sheet obtained by subjecting a hot-dip galvanized steel sheet to alloying treatment to alloy the plating layer is X.
In the method of measuring by line diffraction method, δ_1-FeZn
Measuring the degree of alloying of an alloyed hot-dip galvanized steel sheet, which is characterized by measuring the peak intensity and/or diffraction intensity of diffraction lines on two different index planes in the _7 phase, and determining the degree of alloying based on the measured values. Method. 2. The diffraction lines each have a crystal lattice spacing of 2.554 Å ~
The method for measuring the degree of alloying of an alloyed hot-dip galvanized steel sheet according to claim 1, which is 2.318 Å in two different index planes of the δ_1-FeZn_7 phase. 3. One of the diffraction lines has a crystal lattice spacing of 2.419
Å and the index plane is (14·0), and the other is a patent claim in which the crystal lattice spacing is 2.398 Å and the index plane is (14·3). A method for measuring the degree of alloying of an alloyed hot-dip galvanized steel sheet according to item 1. 4. One of the diffraction lines has a crystal lattice spacing of 2.419
Å and the index plane is (14·0), and the other is a patent claim in which the crystal lattice spacing is 2.347 Å and the index plane is (14·6). A method for measuring the degree of alloying of an alloyed hot-dip galvanized steel sheet according to item 1.