CN115468831A - Dyeing metallographic corrosive agent, preparation method thereof and application of dyeing metallographic corrosive agent in quantitative detection of high-temperature ferrite in martensitic heat-resistant steel - Google Patents
Dyeing metallographic corrosive agent, preparation method thereof and application of dyeing metallographic corrosive agent in quantitative detection of high-temperature ferrite in martensitic heat-resistant steel Download PDFInfo
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- CN115468831A CN115468831A CN202211057693.9A CN202211057693A CN115468831A CN 115468831 A CN115468831 A CN 115468831A CN 202211057693 A CN202211057693 A CN 202211057693A CN 115468831 A CN115468831 A CN 115468831A
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- G—PHYSICS
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- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/32—Polishing; Etching
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
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Abstract
The invention provides a dyeing metallographic corrosive agent, a preparation method thereof and application thereof in quantitative detection of high-temperature ferrite in martensite heat-resistant steel, wherein the corrosive agent comprises potassium permanganate, chromic anhydride, perchloric acid and water.
Description
Technical Field
The invention belongs to the field of quantitative analysis of metallographic microstructure, and particularly relates to a dyed metallographic corrosive agent, a preparation method thereof and application thereof in quantitative detection of high-temperature ferrite in martensitic heat-resistant steel.
Background
The martensite heat-resistant steel is mainly used in a high-temperature and high-pressure environment for operation of thermal equipment, requires high-temperature endurance strength and toughness and certain corrosion resistance, is widely used in the fields of thermal power and nuclear power, and has a microstructure composed of martensite or martensite and bainite (including a small amount of high-temperature ferrite) and mainly comprises P92, P91, P122 and other marks. Because a small amount of high-temperature ferrite exists in the structure of the molten iron, the high-temperature ferrite is generated by peritectic transformation and precipitation of liquid molten iron at 1538 ℃, and is also called delta-ferrite. In general, high-temperature ferrite is less common in a normal temperature environment, but is often present in partially heat-resistant steel. Since high-temperature ferrite belongs to a brittle phase, reduces toughness of a material, easily causes microcracks during processing, and easily causes pitting corrosion, it is a harmful additive in martensitic heat-resistant steel to control its content.
Two metallographic etching solutions (picric acid hydrochloric acid alcoholic solution, copper sulfate hydrochloric acid aqueous solution) and two electrolytic etching methods (10% aqueous solution of Na (OH), nitric acid and oxalic acid) are recommended in Standard YB/T4402-2014 metallographic determination of ferrite content in martensitic stainless Steel. In the method, the high-temperature ferrite generally presents gray, has little contrast with a matrix, cannot extract colors by utilizing gray value difference, can only carry out morphology observation, and then is roughly quantified by comparing with a standard provided atlas.
In a chinese invention patent "a statistical method of delta ferrite phase area content in martensitic heat-resistant steel" published in 11/27/2013 and having publication number CN 103411972A, there is provided a method for quantifying high-temperature ferrite by using metallographic quantification software, wherein high-temperature ferrite is changed into black and a matrix is white by electrolytic erosion in a water bath environment. The method needs electrolytic etching, needs water bath heating in the electrolytic process, and has complex process and high cost.
The invention patent of Chinese invention with publication number CN103336102A published in 2013, 10, and 2 provides a calculation formula of high-temperature ferrite content in weld metal of martensite heat-resistant steel, namely a determination method of delta-ferrite content in weld of martensite heat-resistant steel with 9-12% Cr, but the contents of 12 elements of carbon, nitrogen, nickel, cobalt and the like in weld metal must be firstly measured, and then the contents of high-temperature ferrite are calculated by regression analysis, and the method has complex process.
Disclosure of Invention
The invention aims to provide a dyeing metallographic corrosive agent and a preparation method thereof, which adopt brand-new raw materials to enable various tissues in martensite heat-resistant steel to present different colors. The color metallographic phase is also called thin film dyeing. The method uses a special corrosive agent to react with each phase on the ground surface to form a film (or reaction precipitate) with uneven thickness, and under the irradiation of white light, each phase presents different color contrast due to the interference of light, thereby improving the identification capability of each phase in metal and alloy.
The invention also aims to provide an application of the dyeing metallographic corrosive agent in quantitative detection of high-temperature ferrite in martensite heat-resistant steel, so that the high-temperature ferrite, martensite and bainite in the martensite heat-resistant steel can present different colors under a microscope ocular, the distribution and the morphology of various tissues can be clearly observed, and further quantitative metallographic phase is adopted for measuring the content of the high-temperature ferrite.
The specific technical scheme of the invention is as follows:
a staining metallographic corrosive agent comprises potassium permanganate, chromic anhydride, perchloric acid and water.
The mass ratio of the potassium permanganate to the chromic anhydride to the water is as follows: 3-6:8-10:100, respectively;
the volume ratio of perchloric acid to water is as follows: 1-3:100.
the water is distilled water.
The pH value of the staining metallographic corrosive agent is 4-5.
The invention provides a preparation method of a dyeing metallographic corrosive agent, which comprises the following steps:
mixing the potassium permanganate, the chromic anhydride, the perchloric acid and the water according to the mass ratio, and standing.
Standing for 55-65min;
the preparation method comprises the following steps: the preparation method is carried out at the temperature of 23-28 ℃, can be carried out at room temperature, does not need to strictly control the temperature, and has low cost.
The invention provides an application of a dyeing metallographic corrosive agent in quantitative detection of high-temperature ferrite in martensite heat-resistant steel, and the specific application method comprises the following steps:
1) Preparing a martensite heat-resistant steel sample;
2) Pre-corroding the sample by using nital, then cleaning by using absolute ethyl alcohol, and drying;
3) Immersing the sample treated in the step 2) into a dyeing metallographic corrosive agent, wherein the detection surface faces upwards;
4) After corrosion, the high-temperature ferrite is white, the martensite is brown and the bainite is dark blue under the observation of a metallographic microscope, and then phase quantitative statistics is carried out.
The step 1) comprises the following steps:
1-1) cutting the martensite heat-resistant steel into blocks;
1-2) carrying out coarse grinding on the detection surface on a metallographic specimen grinding machine, and then carrying out fine grinding by using abrasive paper;
1-3) continuously polishing the ground sample by mechanical polishing.
In the step 1-1), the size of a specific cut sample is suitable for metallographic examination and observation, the metallographic detection surface is not less than 10mm multiplied by 10mm under general conditions, and if the sample is too small, the sample is processed by adopting an embedding method. Microstructural changes due to temperature increases should be avoided during sampling.
The fine grinding in the step 1-2) comprises the following steps: and (3) carrying out fine grinding by adopting 240#, 600# and 1000# sandpaper in sequence, removing grinding marks in the coarse grinding process, and grinding by changing the sandpaper once to be vertical to the grinding marks in the previous process. Namely, when every time one sand paper is replaced, the sample is rotated by 90 degrees, so that the grinding mark of the previous pass is vertical to the grinding mark of the current pass. Each pass of grinding is carried out until the grinding surface is flat, the grinding mark direction is consistent and the grinding mark of the last pass is covered.
In the step 1-3), a metallographic polishing agent is used for rough polishing and fine polishing in the polishing process so as to remove scratches and deformation disturbing layers generated by fine grinding and remove scratches visible to the naked eye, so that the surface of the sample is changed into a smooth and perfect mirror surface. The rough polishing process is to make the detection surface evenly and lightly pressed on the rotating polishing disk and rotate the polishing direction during polishing, and the polishing process should be supplemented with polishing liquid from time to time while maintaining the proper humidity of the polishing surface. And in the fine polishing process, the detection surface is continuously subjected to fine polishing after rough polishing to remove the micro scratches and the deformation layer, and after the fine polishing is finished, the surface of the dyed sample is carefully cleaned to ensure that the surface of the sample is clean and has no oil stain.
In the step 2), the sample treated in the step 1) is firstly pre-corroded for 1-2 seconds by nitric acid alcohol with the volume concentration of 2-4%, then is cleaned by absolute ethyl alcohol and is dried by hot air.
In the step 3), the dried sample is clamped by a wood clamp and immersed in the prepared dyeing metallographic corrosive agent, the detection surface faces upwards, so that the color change of the detection surface can be seen by naked eyes, and the sample is continuously shaken, so that the detection surface is uniformly corroded.
The corrosion time in the step 3) is 40-60s;
in the step 3), according to the effective film interference effect which can be formed on the surface of the detection surface, the corrosion time is determined by observing the macroscopic color change of the detection surface by naked eyes, the color change is yellow-blue-purple-light brown, the corrosion is carried out at room temperature, the corrosion time is between 40s and 60s, when the color is changed into light brown, the sample is taken out, the sample is immediately cleaned by absolute ethyl alcohol and dried by hot air, the detection surface is kept dry and clean, and any dirt and water stains are not allowed to exist.
The dyeing metallographic corrosive provided by the invention can be recycled, and the use frequency is less than or equal to 4 times.
In the step 4), the prepared sample is placed under a metallographic microscope for observation, and the proper aperture and view field diaphragm are adjusted. And adjusting a focusing knob to enable the imaging to be clear, wherein the high-temperature ferrite is white, the martensite is brown and the bainite is dark blue under the ocular lens. And adopting metallographic quantitative statistical software, extracting the tissues to be detected by utilizing the difference of threshold values of different tissues according to the national standard GB/15749-2008, calculating the high-temperature martensite content, and simultaneously calculating the martensite and bainite contents.
The corrosive can clearly distinguish martensite, bainite and high-temperature ferrite, simultaneously can determine the content of the high-temperature ferrite in the martensite heat-resistant steel by utilizing quantitative metallographic phase, can also determine the content of the martensite and the bainite in the steel, has large difference of different tissue colors, is clearly distinguished, and provides technical support for the optimization of the production process of the heat-resistant steel.
Drawings
FIG. 1 is a color metallographic photograph of a P91 steel sample of corrosion-resistant steel according to the present invention 1;
FIG. 2 is a color metallographic photograph of a P91 steel sample 2 of corrosion-resistant steel according to the present invention; the high-temperature ferrite content is 3.2%, the bainite content is 44.7%, and the martensite content is 52.1%;
FIG. 3 is a color metallographic photograph of a sample 3 of a corrosion heat-resistant steel P91 according to the present invention, in which the high temperature ferrite content is 5.8%, the bainite content is 45.4%, and the martensite content is 48.8%.
Detailed Description
The invention is further illustrated by the following examples. The invention will be more clearly understood by reference to the following detailed description of specific steps taken in conjunction with the accompanying drawings.
Example 1
The application of the dyeing metallographic corrosive agent in the quantitative detection of high-temperature ferrite in martensite heat-resistant steel is characterized in that a detection object is martensite heat-resistant steel P91 (sample 1), and the specific application method comprises the following steps:
1) Selecting martensite heat-resistant steel P91 produced in large-scale industrial production as a research object, cutting the heat-resistant steel into blocks, wherein the specific sample size is that a metallographic detection surface is not less than 10mm multiplied by 10mm, and if the sample is too small, processing the sample by adopting an embedding method. Microscopic structure change caused by temperature rise in the sampling process is avoided; and (3) roughly grinding the detected surface on a metallographic specimen grinding machine, then finely grinding by using No. 240 abrasive paper, no. 600 abrasive paper and No. 1000 abrasive paper in sequence, removing grinding marks in the rough grinding process, and grinding by changing one abrasive paper every time to be vertical to the front grinding mark. Namely, when every time one sand paper is replaced, the sample is rotated by 90 degrees, so that the grinding mark of the previous pass is vertical to the grinding mark of the current pass. Grinding each pass until the grinding surface is flat, the grinding trace direction is consistent, and the grinding trace of the last pass is covered; and (5) continuously polishing the ground sample by adopting mechanical polishing. And performing rough polishing and fine polishing by using a metallographic polishing agent to remove scratches and deformation turbulent layers generated by fine grinding and remove macroscopic scratches so that the surface of the sample is changed into a smooth and perfect mirror surface. The rough polishing process is to make the test surface evenly and lightly pressed on the rotating polishing disk and rotate the polishing direction during polishing, and the polishing process should be supplemented with polishing liquid from time to time while maintaining proper humidity of the polishing surface. And in the fine polishing process, the inspection surface is subjected to fine polishing after rough polishing to remove the micro scratches and the deformation layer, and after the fine polishing is finished, the surface of the dyed sample is carefully cleaned to ensure that the surface of the sample is clean and has no oil stain.
2) And pre-corroding the polished sample with 4% nitric acid alcohol for 2 seconds to activate the detection surface, cleaning with absolute ethyl alcohol, and drying with hot air.
3) The sample after will weathering is cliied with the wood clip and is soaked in the dyeing metallography corrosive agent, and the detection surface is up, makes the change that the naked eye can see the detection surface colour to constantly rock the sample, make the observation face evenly receive the corruption. The corrosion time is determined by the color change of the detection surface, the correct color change is yellow-blue-purple-light brown, the corrosion time is 45s, when the color is changed into light brown, the sample is taken out, is immediately cleaned by absolute ethyl alcohol and is dried by hot air, and the detection surface is kept dry and clean without any dirt and water stain.
The preparation method of the dyeing metallographic corrosive agent comprises the following steps: mixing 4g of potassium permanganate, 9g of chromic anhydride, 3ml of perchloric acid and 100ml of distilled water at room temperature; the corrosive agent ensures that the pH =4, and the solution can be used after standing at room temperature for 60 minutes after being prepared. The prepared dyeing metallographic corrosive agent can be recycled, the using frequency is less than or equal to 4 times, and the prepared environment temperature is within the range of 23-28 ℃.
3) And (3) placing the prepared sample under a metallographic microscope for observation, and adjusting a proper aperture and a proper view field diaphragm. The focusing knob is adjusted to enable the imaging to be clear, and the ferrite is white, the martensite is brown and the bainite is dark blue under the ocular lens at high temperature. And (3) adopting metallographic quantitative statistical software, extracting the tissues to be detected by utilizing the difference of threshold values of different tissues according to the national standard GB/15749-2008, and calculating the content of the high-temperature martensite, wherein the content of the P91 high-temperature ferrite is 3.8%, the content of the bainite is 29.3%, and the content of the martensite is 66.9% in the embodiment.
Example 2
An application of a dyeing metallographic corrosive agent in quantitative detection of high-temperature ferrite in martensite heat-resistant steel, wherein a detection object is martensite heat-resistant steel P91, and a preparation method of the used dyeing metallographic corrosive agent comprises the following steps: mixing 3g of potassium permanganate, 9.5g of chromic anhydride, 2.5ml of perchloric acid and 100ml of distilled water at room temperature; the corrosive agent ensures that the pH =4, and the solution can be used after standing at room temperature for 60 minutes after being prepared. The configured ambient temperature is in the range of 23-28 ℃. The detection results of sample 2 were shown in FIG. 2, which is the same as example 1.
Example 3
An application of a dyeing metallographic corrosive agent in quantitative detection of high-temperature ferrite in martensite heat-resistant steel, wherein a detection object is martensite heat-resistant steel P91, and a preparation method of the used dyeing metallographic corrosive agent comprises the following steps: mixing 6g of potassium permanganate, 8.2 g of chromic anhydride, 3ml of perchloric acid and 100ml of distilled water at room temperature; the pH =4 is ensured by the corrosive agent, the prepared solution can be used after standing for 60 minutes at room temperature, and the prepared environment temperature is in the range of 23-28 ℃. Otherwise, sample 3 was tested in the same manner as in example 1, and the test results are shown in FIG. 3.
Comparative example 1
The same martensitic heat-resistant steel P91 was treated with the same method and etchant as in example 1, and etched for 30 seconds, and in the case where the etching time was insufficient, a complete diffraction film could not be formed because the etchant did not sufficiently react with the sample. Under the irradiation of microscope white light, various color artifacts can be formed, and the colors are different in depth and cannot be identified and quantified.
Claims (10)
1. The staining metallographic corrosive agent is characterized by comprising potassium permanganate, chromic anhydride, perchloric acid and water.
2. The dyed metallographic etchant of claim 1, wherein the mass ratio of the potassium permanganate to the chromic anhydride to the water is: 3-6:8-10:100.
3. the corrosive agent for dyeing metallography according to claim 1 or 2, characterized in that the volume ratio of perchloric acid to water is: 1-3:100.
4. the dyed metallographic etchant of claim 1 or 2 having a pH of 4 to 5.
5. The preparation method of the dyeing metallographic corrosive agent disclosed by any one of claims 1 to 4 is characterized by comprising the following steps: mixing the potassium permanganate, the chromic anhydride, the perchloric acid and the water according to the mass ratio, and standing.
6. The method according to claim 5, wherein the standing is carried out for 55 to 65min.
7. The application of the dyeing metallographic corrosive agent in the quantitative detection of high-temperature ferrite in martensite heat-resistant steel is characterized in that the specific application method comprises the following steps:
1) Preparing a martensite heat-resistant steel sample;
2) Pre-corroding the sample by using nital, then cleaning by using absolute ethyl alcohol, and drying;
3) Immersing the sample treated in the step 2) into a dyeing metallographic corrosive agent, wherein the detection surface faces upwards;
4) After corrosion, the high-temperature ferrite is white, the martensite is brown and the bainite is dark blue under the observation of a metallographic microscope, and then phase quantitative statistics is carried out.
8. Use according to claim 7, characterized in that step 1) comprises the following steps:
1-1) cutting the martensite heat-resistant steel into blocks;
1-2) carrying out coarse grinding on the detection surface on a metallographic specimen grinding machine, and then carrying out fine grinding by using abrasive paper;
1-3) continuously polishing the ground sample by mechanical polishing.
9. Use according to claim 7 or 8, wherein the etching time in step 3) is 40-60s.
10. The use of claim 7 or 8, wherein the dyed metallographic etchant is recycled less than or equal to 4 times.
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