CN112557133B

CN112557133B - Method for preparing hot-dip coating transmission sample by reduction-oxidation delamination method

Info

Publication number: CN112557133B
Application number: CN202011246262.8A
Authority: CN
Inventors: 杨洪刚; 吕家舜; 徐闻慧; 王永明; 徐承明; 严平原; 李文竹
Original assignee: Angang Steel Co Ltd
Current assignee: Angang Steel Co Ltd
Priority date: 2020-11-10
Filing date: 2020-11-10
Publication date: 2022-05-20
Anticipated expiration: 2040-11-10
Also published as: CN112557133A

Abstract

A method for preparing a hot-dip coating transmission sample by a reduction-oxidation delamination method comprises the steps of taking a steel plate, washing with acid and alkali, and putting the steel plate into a hot-dip galvanizing simulator; in the annealing stage, the steel plate is subjected to reduction treatment, then is subjected to oxidation treatment after reduction, and then is immersed into a hot plating bath, and is discharged out of a hot plating bath pot and then is swept by an air knife to obtain a hot-dip plated steel plate; the coating subjected to hot dipping after oxidation is poorer in combination with the steel plate, the plated steel plate is bent to a certain degree, the coating can be automatically separated from the matrix, and the coating is taken down by using tools such as tweezers; and (4) preparing a transmission sample. Compared with the prior art, the invention has the beneficial effects that: the invention provides a method for preparing a hot-dip coating transmission sample by a reduction-oxidation delamination method, which is simple and convenient in sample preparation method and can obtain the complete information of a coating in a transmission electron microscope. The sample prepared by the method completely reproduces the structure, structure and components of the plating layer after the hot-dip technological process.

Description

Method for preparing hot-dip coating transmission sample by reduction-oxidation delamination method

Technical Field

The invention relates to the field of hot dip coating technology and transmission detection, in particular to a method for preparing a hot dip coating transmission sample by a reduction-oxidation delamination method.

Background

The magnification of the transmission electron microscope can reach more than 5 ten thousand times, the microscopic characteristics and components of a detected sample can be clearly seen, the analysis and the research of the macroscopic performance of the material are very important, but the sample needs to be thin enough so that rays can penetrate through the sample, so that the preparation of the sample by the transmission electron microscope is difficult, particularly, for the observation of a coating sample, taking a hot-dip coating as an example, the thickness of the coating is often several micrometers to dozens of micrometers, and a substrate combined with the coating needs to be removed to the maximum extent.

The currently commonly used means in practical applications is double spraying or ion thinning. The double-spraying effect is generally poor, the principle is that a corrosive agent is mainly adopted to inject and corrode the middle of a sample, but the corrosion resistance of a substrate and a coating is generally different greatly, most prepared samples can only thin one side of the sample, and the coating is often difficult to keep; the ion thinning is relatively good, the principle is mainly mechanical etching of a micro-area, but the problems are that the mechanical properties of a substrate and a coating are greatly different, the thinning amount of the substrate/the coating is greatly different after etching, and ideal results are difficult to obtain under a transmission electron microscope.

At present, a copper ring or copper pipe method is mostly adopted to manufacture a coating section transmission sample. Chakraborty et al adhered two coated surfaces of a coated sample together with a special glue, then cut to a proper size, put the cut sample into a copper tube with a diameter of 3mm, finely cut along the cross section of the copper tube, mechanically grind the cut sheet, when the cut sheet is sufficiently thin, thin-grind the adhered sample by an ion thin-grind device, finally put the sample into a transmission electron microscope for observation, and CN 102519771A, CN 103308362A, CN 103487303 a also adopts a similar means, or uses a copper ring or a copper tube, and uses organic resin to seal the sample to prepare the transmission cross section sample.

However, this method is greatly affected by the properties of the glue and the properties of the sample, especially in the mechanical grinding process, since the final thickness of the grinding is generally 30 to 100 microns, the sample is in a thin film state at this time, the deformation resistance is very poor, and although the bonding glue is cured, the bonding glue has strong brittleness, and is very easy to break especially in the thin film state. In order to prevent the sample from separating from the copper tube, researchers have used resin burying methods, but in the case of extremely thin, the cured resin is also highly brittle and is easily brittle under the action of mechanical force (pressure and friction), so that the sample can separate from the copper ring. In the ion thinning process, the adhesive glue, the resin material and the plating layer material have larger performance difference, the adhesive glue is easy to fall off in pieces, two combined samples are separated, or a thin area is concentrated at the position of the adhesive glue, and the sample to be observed does not have the thin area and cannot be observed under a transmission electron microscope. Therefore, the method has low sample preparation success rate and less sample thin areas.

Patent CN 102323119 a discloses a method for preparing a rust layer sample, which mainly adopts a welding and liquid silver sealing means, the liquid silver has a certain difference in performance from the rust layer, especially when preparing a very thin transmission sample, no matter grinding or ion thinning, the difference in performance causes the silver and the rust layer (i.e. two materials with different properties) to be damaged in different forms, once the main substance to be observed is ground off in advance or the ion thinning disappears, the influence on the test is very large.

In the field of hot dip coating, particularly for steel grades containing strong oxidizing elements such as high Si, high Mn and the like, hot dip coating is often carried out in a pre-oxidation and reduction mode, mainly, silicon oxide and manganese oxide are difficult to completely reduce by a reducing atmosphere in a continuous annealing process, so that oxidized substances are remained on the surface of a steel plate, and when hot dip coating is caused, a zinc liquid cannot be completely combined with a substrate to generate a delamination phenomenon.

Disclosure of Invention

The invention aims to provide a method for preparing a hot dip coating transmission sample by a reduction-oxidation delamination method, which utilizes the principle that a hot dip coating and an oxidized substrate surface are easy to delaminate, adopts a brand-new preparation process to more conveniently prepare the transmission sample of the hot dip coating, and enables the transmission sample to obtain ideal coating information under a transmission electron microscope.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for preparing a hot dip coating transmission sample by a reduction-oxidation delamination method comprises the following steps:

1) removing iron scales from a steel plate by acid washing, then removing oil by alkali washing, and putting the steel plate into a hot galvanizing simulator;

2) reduction treatment: the temperature of the hot dip coating annealing process is set correspondingly according to the requirement, and in the annealing stage, the steel plate is reduced firstly, and the reducing atmosphere is hydrogen: the balance of the nitrogen gas accounts for 5-20 vol%, and the reduction is carried out to increase the surface brightness of the steel plate so as to obtain a better delaminating coating;

3) oxidation treatment: carrying out oxidation treatment on the steel plate after reduction, wherein the temperature of the oxidation atmosphere is controlled by dew point, the temperature is kept at 500-900 ℃ for 1-5 min, the volume content of oxygen in a reduction section is 0.1-5 vol%, the higher the dew point is, the higher the water vapor content is, namely, the higher the oxidation atmosphere is, the surface of the steel plate is oxidized to a certain degree;

4) hot dip coating treatment: cooling the reduced-oxidized steel plate to 450-500 ℃, immersing the steel plate into a hot plating bath, taking the steel plate out of a hot plating bath pot, and blowing by adopting an air knife to obtain a hot-dip plated steel plate;

5) delamination treatment: the coating subjected to hot dipping after oxidation is poorer in combination with a steel plate, the plated steel plate is bent to a certain degree, the coating can be automatically separated from a matrix (as shown in figure 1), and the coating is taken down by using tools such as tweezers;

6) transmission sample preparation: because the removed coating is thin enough, the perforation treatment can be directly carried out by double spraying or ion thinning, and an in-situ transmission sample of the hot dip coating is obtained.

The surface roughness of the steel plate treated in the step 1) is less than 1.5 mu m, so that the removed coating has good flatness and is beneficial to transmission observation.

The annealing temperature in the step 2) is 500-900 ℃, and the reduction time is 1-5 min.

The time of the hot plating bath in the step 4) is 3-10 s.

And 4) blowing by adopting an air knife in the step 4) to ensure that the thickness of the coating on the steel plate is 2-10 mu m.

The transmission coated samples that delaminate from the steel plate still incorporate a very thin matrix material, which facilitates the observation of the information on the elemental interaction at the layer/matrix interface in transmission.

The method is suitable for hot-dip coating such as hot-dip galvanized coating, hot-dip galvanized aluminum-magnesium coating, hot-dip aluminum-zinc coating, and the like. The coating material used in the method for transmission observation and the normal coating material undergo the same heating-cooling treatment process, and the structure, structure and components of the coating after the hot-dip process can be reproduced in situ.

Compared with the prior art, the invention has the beneficial effects that:

the invention provides a method for preparing a hot-dip coating transmission sample by a reduction-oxidation delamination method, which is simple and convenient in sample preparation method and can obtain the complete information of a coating in a transmission electron microscope. The sample prepared by the method completely reproduces the structure, structure and components of the plating layer after the hot-dip technological process.

Drawings

FIG. 1 is a graph showing the bending effect of a plated sample after reduction-oxidation treatment.

In the figure: 1-coating separation base plate after bending, 2-coating, 3-base plate.

Detailed Description

The following examples further illustrate embodiments of the present invention.

Example 1: the method for preparing the hot-dip coating transmission sample by the delamination method is described by taking IF steel as an example of hot-dip galvanizing.

1) Taking an IF steel plate 120mm by 220mm, carrying out acid washing-alkali washing treatment to obtain an IF steel plate with the roughness of 1.1 mu m, wiping the IF steel plate with alcohol, and putting the IF steel plate into a hot galvanizing simulator;

2) reduction treatment: the annealing temperature was set at 850 ℃ and the atmosphere was 10 vol% H₂+90vol％N₂Reducing the surface of the steel plate for 2 min;

3) oxidation treatment: the dew point of the oxidizing atmosphere is set to be 25 ℃, the temperature in the furnace is 850 ℃, the oxidizing time is 3 minutes, and then the temperature is reduced to 480 DEG C

4) Hot dip coating treatment: immersing the steel plate in a hot plating bath for 5s, taking the steel plate out of a hot plating bath pot, and blowing by adopting an air knife to ensure that the thickness of a plating layer on the steel plate is about 6 mu m, thereby obtaining a hot-dip plated steel plate;

5) delamination treatment: bending and deforming the steel plate to separate the oxidized surface of the steel plate from the coating, and taking down the coating by using tweezers.

6) Transmission sample preparation: and carrying out perforation treatment on the taken coating by adopting double spraying or ion thinning to obtain an in-situ transmission sample of the hot dip coating.

Claims

1. A method for preparing a hot dip coating transmission sample by a reduction-oxidation delamination method is characterized by comprising the following steps:

1) putting the treated steel plate into a hot galvanizing simulator;

2) reduction treatment: in the annealing stage, the steel plate is firstly subjected to reduction treatment in the reducing atmosphere of hydrogen: 5-20 vol% and the balance of nitrogen;

3) oxidation treatment: carrying out oxidation treatment on the steel plate after reduction, wherein the oxidation atmosphere adopts dew point control, the temperature is kept at 500-900 ℃ for 1-5 min, and the volume content of oxygen in the reduction section is 0.1-5 vol%;

5) delamination treatment: bending the plated steel plate, automatically separating the plating layer from the matrix, and taking down the plating layer;

6) transmission sample preparation: and carrying out perforation treatment by adopting double spraying or ion thinning to obtain an in-situ transmission sample of the hot dip coating.

2. A method for preparing a hot dip coating transmission sample by reduction-oxidation delamination method as set forth in claim 1, wherein the surface roughness of the steel sheet after the treatment in the above step 1) is less than 1.5 μm.

3. The method for preparing the hot-dip coating transmission sample by the reduction-oxidation delamination method as claimed in claim 1, wherein the annealing temperature in the step 2) is 500-900 ℃ and the reduction time is 1-5 min.

4. The method for preparing the hot dip coating transmission sample by the reduction-oxidation delamination method as claimed in claim 1, wherein the hot dip bath time in the step 4) is 3-10 s.

5. The method for preparing the hot-dip coating transmission sample by the reduction-oxidation delamination method as set forth in claim 1, wherein the thickness of the coating on the steel plate is 2 μm to 10 μm by using the air knife purge in the step 4).

6. The method for preparing the hot dip coating transmission sample by the reduction-oxidation delamination method according to the claim 1, which is suitable for hot dip galvanizing coating, hot dip galvanizing aluminum magnesium coating and hot dip aluminum zinc coating.

7. A method for preparing a hot dip coating transmission sample by reduction-oxidation delamination method as set forth in claim 1, wherein the step 1) of treating the steel sheet comprises: and (3) pickling the steel plate to remove iron scales, and then washing with alkali to remove oil.