阅读说明：本技术 一种用于奥氏体不锈钢冷轧薄板的金相腐蚀液及样品腐蚀方法 (Metallographic etchant for austenitic stainless steel cold-rolled sheet and sample corrosion method ) 是由 陈家荣 黄磊 凌锐 贺超 于 2020-12-10 设计创作，主要内容包括：本发明属于奥氏体不锈钢金相腐蚀领域,特别涉及一种用于奥氏体不锈钢冷轧薄板的金相腐蚀液及样品腐蚀方法。该金相腐蚀液由以下体积份数的组分组成：质量浓度为30.0～38.0％的盐酸45～55份,质量浓度为60.0～68.0％的硝酸45～55份,质量浓度为90.0％以上的醋酸3～8份。采用本发明的金相腐蚀液处理后的奥氏体不锈钢冷轧薄板晶界清晰显示,可进行后续评级分析,并且,本发明中各原料使用分析纯级别的试剂即可,制备腐蚀时流程简单,腐蚀显示效率高,利于工业上大规模的推广使用。本发明的金相腐蚀液尤其适用于不锈钢冷轧薄板,金相组织显示效果优异,并且腐蚀速率适宜,腐蚀成功率高。(The invention belongs to the field of metallographic corrosion of austenitic stainless steel, and particularly relates to a metallographic corrosive liquid for an austenitic stainless steel cold-rolled sheet and a sample corrosion method. The metallographic corrosive liquid consists of the following components in parts by volume: 45-55 parts of hydrochloric acid with the mass concentration of 30.0-38.0%, 45-55 parts of nitric acid with the mass concentration of 60.0-68.0% and 3-8 parts of acetic acid with the mass concentration of more than 90.0%. The austenitic stainless steel cold-rolled sheet processed by the metallographic corrosive liquid of the invention has the advantages of clear grain boundary display, capability of subsequent grading analysis, simple preparation process and high corrosion display efficiency, and is beneficial to large-scale industrial popularization and use, and all raw materials in the invention are only required to be analyzed by using analytical grade reagents. The metallographic corrosive liquid is particularly suitable for stainless steel cold-rolled sheets, and has the advantages of excellent metallographic structure display effect, proper corrosion rate and high corrosion success rate.)

1. A metallographic corrosive liquid for an austenitic stainless steel cold-rolled sheet is characterized by comprising the following components in parts by volume: 45-55 parts of hydrochloric acid with the mass concentration of 30.0-38.0%, 45-55 parts of nitric acid with the mass concentration of 60.0-68.0% and 3-8 parts of acetic acid with the mass concentration of more than 90.0%.

2. The metallographic etchant for austenitic stainless steel cold rolled sheets according to claim 1, comprising the following components in parts by volume: 50 parts of hydrochloric acid with the mass concentration of 30.0-38.0%, 50 parts of nitric acid with the mass concentration of 60.0-68.0% and 5 parts of acetic acid with the mass concentration of more than 90.0%;

preferably, the mass concentration of the hydrochloric acid is 36.0-38.0%;

preferably, the mass concentration of the nitric acid is 65.0-68.0%;

preferably, the mass concentration of the acetic acid is more than 99.5%.

3. The metallographic etchant for austenitic stainless steel cold-rolled sheet according to claim 1, wherein the hydrochloric acid has a mass concentration of 38%;

preferably, the mass concentration of the nitric acid is 68%.

4. The metallographic etchant for an austenitic stainless steel cold-rolled sheet according to any one of claims 1 to 3, wherein the austenitic stainless steel cold-rolled sheet has a thickness of 1mm or less.

5. The metallographic etchant for an austenitic stainless steel cold-rolled sheet according to any one of claims 1 to 3, wherein the austenitic stainless steel cold-rolled sheet has a thickness of 0.3mm or less;

preferably, the austenitic stainless steel cold-rolled sheet is 304.

6. A sample corrosion method for austenitic stainless steel cold rolled sheet metal phase analysis, comprising the steps of:

(1) sample treatment:

polishing the sample to obtain a pretreated sample;

(2) preparing a metallographic corrosive liquid:

taking hydrochloric acid, nitric acid and acetic acid as components in the metallographic etchant for the austenitic stainless steel cold-rolled sheet according to any one of claims 1 to 5, uniformly mixing, and standing;

(3) corrosion shows that:

and immersing the pretreated sample into the metallographic corrosive liquid, etching with the polishing surface facing downwards, and then carrying out post-treatment to obtain the sample to be observed.

7. The sample corrosion method for austenitic stainless steel cold rolled sheet metal phase analysis according to claim 6, wherein, in the step (1), the polishing treatment comprises sanding, polishing by polishing liquid;

preferably, the sandpaper is sanded by: sequentially grinding with 400#, 1000#, 2000# water sand paper;

preferably, the polishing solution is a diamond suspension;

preferably, the diamond has a grain size of 3 μm and 1 μm in this order.

8. The sample corrosion method for austenitic stainless steel cold-rolled sheet metal phase analysis according to claim 6, wherein the standing time in step (2) is 15-30 min.

9. The sample corrosion method for austenitic stainless steel cold-rolled sheet metal phase analysis according to claim 6, wherein in the step (3), etching is performed at normal temperature, and the etching time is 10-20 s;

preferably, the etching time is 10-15 s.

10. The sample corrosion method for austenitic stainless steel cold-rolled sheet metal phase analysis according to claim 6, wherein in step (3), the post-treatment comprises rinsing and drying the etched sample.

Technical Field

The invention belongs to the field of metallographic corrosion of austenitic stainless steel, and particularly relates to a metallographic corrosive liquid for an austenitic stainless steel cold-rolled sheet and a sample corrosion method.

Background

Metallographic analysis is one of the main methods for researching the internal structure and defects of metals and alloys, and plays an important role in the field of metal material research. Metallographic analysis is mainly to utilize a metallographic microscope to carry out amplification observation, discrimination and analysis on the surface of a specially prepared sample, and to study the relationship between the internal structure of the metal and the alloy and the chemical components of the metal and the alloy; determining the microscopic structures of the metal and the alloy after different processing and heat treatment; judging whether the quality of the material is qualified or not, and the like. Metallographic analysis is required to be done, firstly, metallographic corrosion is carried out on a sample, and subsequent observation and analysis can be carried out only if a clear structure is corroded.

General corrosion methods for austenitic stainless steels fall into two categories, electrolytic corrosion and chemical reagent corrosion. The electrolytic corrosion is generally carried out by using a saturated oxalic acid solution, the voltage is 3-6 v, and the time is 10-25 s. The corrosive liquid used by the chemical reagent corrosion is usually aqua regia or ferric chloride hydrochloric acid solution.

With the improvement of the whole industrial level in China, stainless steel products are also developed to the high end, and in recent years, austenitic stainless steel cold-rolled sheet and ultrathin sheet products are more and more. When metallographic analysis is carried out on austenitic stainless steel cold-rolled sheets, particularly ultrathin sheet samples with the thickness of less than 0.3mm, the metallographic structure of the austenitic stainless steel cold-rolled sheets is difficult to show through electrolytic corrosion, and the conventional chemical corrosion reagent has the defects of high corrosion rate, high operation difficulty, easy dirty surface of the corroded samples and low corrosion success rate.

Disclosure of Invention

The invention aims to provide a metallographic corrosive liquid for an austenitic stainless steel cold-rolled sheet and a sample corrosion method, and aims to solve the problems of low corrosion success rate caused by poor metallographic structure display effect, high corrosion rate and the like when the existing metallographic corrosive liquid is used for the austenitic stainless steel cold-rolled sheet.

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

a metallographic corrosive liquid for an austenitic stainless steel cold-rolled sheet comprises the following components in parts by volume: 45-55 parts of hydrochloric acid with the mass concentration of 30.0-38.0%, 45-55 parts of nitric acid with the mass concentration of 60.0-68.0% and 3-8 parts of acetic acid with the mass concentration of more than 90.0%.

Preferably, the metallographic corrosive liquid consists of the following components in parts by volume: 50 parts of hydrochloric acid with the mass concentration of 30.0-38.0%, 50 parts of nitric acid with the mass concentration of 60.0-68.0% and 5 parts of acetic acid with the mass concentration of more than 90.0%.

Preferably, the mass concentration of the hydrochloric acid is 36.0-38.0%.

Preferably, the mass concentration of the nitric acid is 65.0-68.0%.

Preferably, the mass concentration of the acetic acid is more than 99.5%.

Preferably, the mass concentration of the hydrochloric acid is 38%.

Preferably, the mass concentration of the nitric acid is 68%.

Preferably, the austenitic stainless steel cold-rolled sheet has a thickness of 1mm or less.

Further preferably, the austenitic stainless steel cold-rolled sheet has a thickness of 0.3mm or less.

Preferably, the austenitic stainless steel cold-rolled sheet is 304.

A sample corrosion method for austenitic stainless steel cold rolled sheet metal phase analysis, comprising the steps of:

(1) sample treatment:

polishing the sample to obtain a pretreated sample;

(2) preparing a metallographic corrosive liquid:

taking hydrochloric acid, nitric acid and acetic acid according to the components in the metallographic etchant for the austenitic stainless steel cold-rolled sheet, uniformly mixing and standing;

(3) corrosion shows that:

and immersing the pretreated sample into the metallographic corrosive liquid, etching with the polishing surface facing downwards, and then carrying out post-treatment to obtain the sample to be observed.

Preferably, in step (1), the polishing treatment includes sanding and polishing with a polishing solution.

Preferably, the sandpaper is sanded by: and (4) grinding by using 400#, 1000#, and 2000# water sandpaper in sequence.

Preferably, the polishing liquid is a diamond suspension.

Preferably, the diamond has a grain size of 3 μm and 1 μm in this order.

Preferably, in the step (2), the standing time is 15-30 min.

Preferably, in the step (3), etching is carried out at normal temperature, and the etching time is 10-20 s;

further preferably, the etching time is 10-15 s.

Preferably, in the step (3), the post-treatment comprises washing and drying the etched sample.

Compared with the closest prior art, the technical scheme provided by the invention has the following excellent effects:

the austenitic stainless steel cold-rolled sheet processed by the metallographic corrosive liquid of the invention has the advantages of clear grain boundary display, capability of subsequent grading analysis, simple preparation process and high corrosion display efficiency, and is beneficial to large-scale industrial popularization and use, and all raw materials in the invention are only required to be analyzed by using analytical grade reagents.

The metallographic corrosive liquid is particularly suitable for stainless steel cold-rolled sheets, and has the advantages of excellent metallographic structure display effect, proper corrosion rate and high corrosion success rate.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention. Wherein:

FIG. 1 is an austenite microstructure of a cold-rolled 304 steel sheet having a thickness of 0.74mm according to example 1 of the present invention;

FIG. 2 is a graph showing the effects of the austenitic corrosion of a cold-rolled 304 steel sheet having a thickness of 0.74mm according to comparative example 1;

FIG. 3 is a graph showing the effects of the austenitic corrosion of a cold-rolled 304 steel sheet having a thickness of 0.74mm according to comparative example 2 of the present invention;

FIG. 4 is a graph showing the effects of the austenitic corrosion of a cold-rolled 304 steel sheet having a thickness of 0.74mm according to comparative example 3 of the present invention;

FIG. 5 is an austenite microstructure of a cold-rolled 304 steel sheet having a thickness of 0.19mm according to example 2 of the present invention;

FIG. 6 is an austenite microstructure of a cold-rolled 304 steel sheet having a thickness of 0.44mm according to example 3 of the present invention;

FIG. 7 is an austenite microstructure of a cold-rolled 304 steel sheet having a thickness of 1.00mm in example 4 of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention.

The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The invention relates to a metallographic corrosive liquid for an austenitic stainless steel cold-rolled sheet, which consists of the following components in parts by volume: 45 to 55 parts (e.g., 45, 47, 49, 51, 53, 55 parts) of hydrochloric acid having a mass concentration of 30.0 to 38.0% (e.g., 30.0%, 31.0%, 32.0%, 33.0%, 34.0%, 35.0%, 36.0%, 36.5%, 37%, 37.5%, 38.0%), 45 to 55 parts (e.g., 45, 47, 49, 51, 53, 55 parts) of nitric acid having a mass concentration of 60.0 to 68.0% (e.g., 60.0%, 61.0%, 62.0%, 63.0%, 64.0%, 65.0%, 66.0%, 67.0%, 68.0%), 45 to 55 parts (e.g., 45, 47, 49, 51, 53, 55 parts) of acetic acid having a mass concentration of 99.5% or more (e.g., 99.5%, 99.6%, 99.7%, 99.8%), 3 to 8 parts (e.g., 3, 4, 5, 6, 7, 8 parts). As a preferred embodiment, the metallographic corrosive liquid of the invention consists of the following components in parts by volume: 50 parts of hydrochloric acid with the mass concentration of 30.0-38.0%, 50 parts of nitric acid with the mass concentration of 60.0-68.0% and 5 parts of acetic acid with the mass concentration of more than 90.0%. More preferably, the mass concentration of the hydrochloric acid is 36.0-38.0%, the mass concentration of the nitric acid is 65.0-68.0%, and the mass concentration of the acetic acid is 99.5% or more. Still more preferably, the hydrochloric acid has a mass concentration of 38% and 50 parts by volume, and the nitric acid has a mass concentration of 68% and 50 parts by volume and the acetic acid has a volume fraction of 5 parts.

Compared with the existing chemical reagent corrosion, the metallographic corrosive liquid is particularly suitable for austenitic stainless steel cold-rolled sheets with the thickness of less than 1mm, even less than 0.3mm, and can improve the corrosion success rate of the sheets. The material of the austenitic stainless steel cold-rolled sheet in the present invention is 304. The sample corrosion method for austenitic stainless steel cold-rolled sheet metal phase analysis comprises the following steps:

(1) sample treatment:

polishing the sample to obtain a pretreated sample, wherein the polishing comprises grinding with 400#, 1000#, 2000# water sand paper in sequence, and polishing with diamond suspension liquid with grain size of 3 μm and 1 μm as polishing solution;

(2) preparing a metallographic corrosive liquid:

taking hydrochloric acid, nitric acid and acetic acid according to the components in the metallographic etchant for the austenitic stainless steel cold-rolled sheet, uniformly mixing, wherein the solution is light yellow, and standing for 15-30 min (for example, 15min, 18min, 20min, 23min, 27min and 30min) to convert the solution into dark red, so that the metallographic etchant is obtained;

(3) corrosion shows that:

and (2) immersing the pretreated sample into the metallographic corrosive liquid, etching the sample with the polishing surface facing downwards for 10-20 s (for example, 10s, 12s, 15s, 17s and 20s), then washing and drying the etched sample to obtain a sample to be observed, wherein the surface of the sample can be washed by water or ethanol to remove corrosive agents and dirt.

The austenitic stainless steel cold-rolled sheet processed by the metallographic corrosive liquid has clear grain boundary, can be subjected to subsequent rating analysis, and is prepared by only using analytically pure reagents for all raw materials.

Example 1

The metallographic etchant for an austenitic stainless cold-rolled sheet according to the present example was composed of 50mL of hydrochloric acid having a mass concentration of 38.0%, 50mL of nitric acid having a mass concentration of 68.0%, and 5mL of acetic acid having a mass concentration of 99.5%.

The sample corrosion method for austenitic stainless steel cold-rolled sheet metal phase analysis in this embodiment is directed to a 304 cold-rolled sheet with a thickness of 0.74mm, and includes the following specific steps:

(1) sample treatment:

after the sample is inlaid, grinding the sample by using No. 400, No. 1000 and No. 2000 waterproof abrasive paper in sequence, polishing the sample into a scratch-free mirror surface by using diamond suspensions of 3 mu m and 1 mu m in sequence, and then washing and drying the mirror surface by using clear water to obtain a pretreated sample;

(2) preparing a metallographic corrosive liquid:

at normal temperature, 50mL of hydrochloric acid (with the mass concentration of 38.0%) is measured and poured into a beaker, then 50mL of nitric acid (with the mass concentration of 68.0%) and 5mL of acetic acid (with the mass concentration of 99.5%) are measured and poured into the beaker in sequence, after the mixture is stirred evenly by a stirring rod lightly, the mixture is stood for 20min to prepare metallographic corrosive liquid;

(3) corrosion shows that:

and (3) immersing the polished sample into the metallographic corrosive liquid with the polished surface facing downwards, slightly stirring the sample to etch for 12s, putting the sample into tap water to be fully washed after etching is finished, and drying the sample by using dry air to obtain the sample to be observed.

The sample to be observed was observed by a metallographic microscope, and the austenitic microstructure of the 304 cold-rolled sheet having a thickness of 0.74mm in this example is shown in FIG. 1. As can be seen from FIG. 1, the austenite grain boundaries clearly show that subsequent grade analysis can be performed.

Comparative example 1

The sample corrosion method of the comparative example specifically comprises the following steps:

(1) sample treatment:

after the sample is inlaid, grinding the sample by using No. 400, No. 1000 and No. 2000 waterproof abrasive paper in sequence, polishing the sample into a scratch-free mirror surface by using diamond suspensions of 3 mu m and 1 mu m in sequence, and then washing and drying the mirror surface by using clear water to obtain a pretreated sample;

(2) preparing a corrosive liquid:

at normal temperature, measuring 40mL of hydrochloric acid (with the mass concentration of 38.0%) and pouring the hydrochloric acid into a beaker, sequentially measuring 40mL of nitric acid (with the mass concentration of 68.0%) and 20mL of acetic acid (with the mass concentration of 99.5%) and pouring the nitric acid and the acetic acid into the beaker, slightly and uniformly stirring the nitric acid and the acetic acid by using a stirring rod, and standing the mixture for 20min to prepare an etchant;

(3) corrosion shows that:

and (3) immersing the polished sample into the corrosive liquid with the polished surface facing downwards, slightly stirring the sample to etch for 5s, putting the sample into tap water to be fully washed after etching is finished, and drying the sample by using dry air to obtain the sample to be observed.

The austenite corrosion effect of the 304 cold-rolled sheet with the thickness of 0.74mm in the comparative example is shown in FIG. 2 by observing the sample to be observed through a metallographic microscope. As can be seen from FIG. 2, the sample is over-corroded after being etched for 5s, and only part of austenite grain boundaries can be distinguished, which indicates that the corrosive agent is too strong in corrosivity and difficult to operate.

Comparative example 2

The sample corrosion method of the comparative example specifically comprises the following steps:

(1) sample treatment:

after the sample is inlaid, grinding the sample by using No. 400, No. 1000 and No. 2000 waterproof abrasive paper in sequence, polishing the sample into a scratch-free mirror surface by using diamond suspensions of 3 mu m and 1 mu m in sequence, and then washing and drying the mirror surface by using clear water to obtain a pretreated sample;

(2) preparing a corrosive liquid:

at normal temperature, 25mL of distilled water is measured and poured into a beaker, 25mL of hydrochloric acid (with the mass concentration of 38.0%), 25mL of nitric acid (with the mass concentration of 68.0%) and 25mL of acetic acid (with the mass concentration of 99.5%) are measured and poured into the beaker in sequence, after the mixture is stirred evenly by a stirring rod, the mixture is stood for 20min to prepare corrosive liquid;

(3) corrosion shows that:

and (3) immersing the polished sample into the corrosive liquid with the polished surface facing downwards, slightly stirring the sample to etch for 15s, putting the sample into tap water to be fully washed after etching is finished, and drying the sample by using dry air to obtain the sample to be observed.

The austenite corrosion effect of the 304 cold-rolled sheet with the thickness of 0.74mm in the comparative example is shown in FIG. 3 by observing the sample to be observed through a metallographic microscope. As can be seen from FIG. 3, the sample is not corroded uniformly, only part of austenite grain boundaries can be displayed in a fuzzy manner, and the corrosive is not suitable for corroding 304 cold-rolled sheets.

Comparative example 3

The sample corrosion method of the comparative example specifically comprises the following steps:

(1) sample treatment:

after the sample is inlaid, grinding the sample by using No. 400, No. 1000 and No. 2000 waterproof abrasive paper in sequence, polishing the sample into a scratch-free mirror surface by using diamond suspensions of 3 mu m and 1 mu m in sequence, and then washing and drying the mirror surface by using clear water to obtain a pretreated sample;

(2) preparing a corrosive liquid:

at normal temperature, measuring 20mL of distilled water, pouring the distilled water into a beaker, sequentially measuring 30mL of hydrochloric acid (with the mass concentration of 38.0%), 10mL of nitric acid (with the mass concentration of 68.0%), 10mL of acetic acid (with the mass concentration of 99.5%) and 10mL of hydrofluoric acid (with the mass concentration of 40%), pouring the mixture into the beaker, slightly and uniformly stirring the mixture by using a stirring rod, and standing the mixture for 30min to prepare an etching solution;

(3) corrosion shows that:

and (3) immersing the polished sample into the corrosive liquid with the polished surface facing downwards, slightly stirring the sample to etch for 10s, putting the sample into tap water to be fully washed after etching is finished, and drying the sample by using dry air to obtain the sample to be observed.

The austenite corrosion effect of the 304 cold-rolled sheet with the thickness of 0.74mm in the comparative example is shown in FIG. 4 by observing the sample to be observed through a metallographic microscope. As can be seen from FIG. 4, the austenite grain boundary corrosion is extremely shallow and difficult to distinguish, and the sample has more precipitates to form black spots, which indicates that the corrosive is not suitable for corroding 304 cold-rolled sheets.

Example 2

The metallographic etchant for austenitic stainless cold-rolled sheet according to the present example was composed of 50mL of hydrochloric acid having a mass concentration of 36.0%, 50mL of nitric acid having a mass concentration of 68.0%, and 5mL of acetic acid having a mass concentration of 99.5%.

The sample corrosion method for austenitic stainless steel cold-rolled sheet metal phase analysis in this embodiment is directed to a 304 cold-rolled sheet with a thickness of 0.19mm, and specifically includes the following steps:

(1) sample treatment:

after the sample is inlaid, grinding the sample by using No. 400, No. 1000 and No. 2000 waterproof abrasive paper in sequence, polishing the sample into a scratch-free mirror surface by using diamond suspensions of 3 mu m and 1 mu m in sequence, and then washing and drying the mirror surface by using clear water to obtain a pretreated sample;

(2) preparing a metallographic corrosive liquid:

at normal temperature, 50mL of hydrochloric acid (with mass concentration of 36.0%) is measured and poured into a beaker, then 50mL of nitric acid (with mass concentration of 68.0%) and 5mL of acetic acid (with mass concentration of 99.5%) are measured and poured into the beaker in sequence, after the mixture is stirred gently and uniformly by a stirring rod, the mixture is kept stand for 20min and then is prepared into metallographic corrosive liquid;

(3) corrosion shows that:

and (3) immersing the polished sample into the metallographic corrosive liquid with the polished surface facing downwards, slightly stirring the sample to etch for 12s, putting the sample into tap water to be fully washed after etching is finished, and drying the sample by using dry air to obtain the sample to be observed.

The sample to be observed was observed by a metallographic microscope, and the austenitic microstructure of the 304 cold-rolled sheet having a thickness of 0.19mm in this example is shown in FIG. 5. As can be seen from fig. 5, the austenite grain boundaries clearly show that a subsequent grade analysis can be performed.

Example 3

The metallographic etchant for an austenitic stainless cold-rolled sheet according to the present example was composed of 50mL of hydrochloric acid having a mass concentration of 37.0%, 50mL of nitric acid having a mass concentration of 66.0%, and 5mL of acetic acid having a mass concentration of 99.5%.

The sample corrosion method for austenitic stainless steel cold-rolled sheet metal phase analysis in this embodiment is directed to a 304 cold-rolled sheet with a thickness of 0.44mm, and specifically includes the following steps:

(1) sample treatment:

after the sample is inlaid, grinding the sample by using No. 400, No. 1000 and No. 2000 waterproof abrasive paper in sequence, polishing the sample into a scratch-free mirror surface by using diamond suspensions of 3 mu m and 1 mu m in sequence, and then washing and drying the mirror surface by using clear water to obtain a pretreated sample;

(2) preparing a metallographic corrosive liquid:

at normal temperature, 50mL of hydrochloric acid (with mass concentration of 37.0%) is measured and poured into a beaker, then 50mL of nitric acid (with mass concentration of 66.0%) and 5mL of acetic acid (with mass concentration of 99.5%) are measured and poured into the beaker in sequence, after the mixture is stirred evenly by a stirring rod lightly, the mixture is kept stand for 20min and then is prepared into metallographic corrosive liquid;

(3) corrosion shows that:

and (3) immersing the polished sample into the metallographic corrosive liquid with the polished surface facing downwards, slightly stirring the sample to etch for 10s, putting the sample into tap water to be fully washed after etching is finished, and drying the sample by using dry air to obtain the sample to be observed.

The sample to be observed was observed by a metallographic microscope, and the austenite microstructure of the 304 cold-rolled sheet having a thickness of 0.44mm in this example is shown in FIG. 6. As can be seen from fig. 6, the austenite grain boundaries clearly show, and a subsequent grade analysis can be performed.

Example 4

The metallographic etchant for an austenitic stainless cold-rolled sheet according to the present example was composed of 50mL of hydrochloric acid having a mass concentration of 38.0%, 50mL of nitric acid having a mass concentration of 65.0%, and 5mL of acetic acid having a mass concentration of 99.5%.

The sample corrosion method for austenitic stainless steel cold-rolled sheet metal phase analysis in this embodiment is directed to a 304 cold-rolled sheet with a thickness of 1.00mm, and specifically includes the following steps:

(1) sample treatment:

after the sample is inlaid, grinding the sample by using No. 400, No. 1000 and No. 2000 waterproof abrasive paper in sequence, polishing the sample into a scratch-free mirror surface by using diamond suspensions of 3 mu m and 1 mu m in sequence, and then washing and drying the mirror surface by using clear water to obtain a pretreated sample;

(2) preparing a metallographic corrosive liquid:

at normal temperature, 50mL of hydrochloric acid (with the mass concentration of 38.0%) is measured and poured into a beaker, then 50mL of nitric acid (with the mass concentration of 65.0%) and 5mL of acetic acid (with the mass concentration of 99.5%) are measured and poured into the beaker in sequence, after the mixture is stirred evenly by a stirring rod lightly, the mixture is stood for 20min to prepare metallographic corrosive liquid;

(3) corrosion shows that:

and (3) immersing the polished sample into the metallographic corrosive liquid with the polished surface facing downwards, slightly stirring the sample to etch for 15s, putting the sample into tap water to be fully washed after etching is finished, and drying the sample by using dry air to obtain the sample to be observed.

The sample to be observed was observed by a metallographic microscope, and the austenitic microstructure of the 304 cold-rolled sheet having a thickness of 1.00mm in this example is shown in FIG. 7. As can be seen from fig. 7, the austenite grain boundaries clearly show that a subsequent grade analysis can be performed.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.