CN113215572B - Corrosive agent and corrosion method for precipitated phase of duplex stainless steel - Google Patents
Corrosive agent and corrosion method for precipitated phase of duplex stainless steel Download PDFInfo
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- CN113215572B CN113215572B CN202110496478.8A CN202110496478A CN113215572B CN 113215572 B CN113215572 B CN 113215572B CN 202110496478 A CN202110496478 A CN 202110496478A CN 113215572 B CN113215572 B CN 113215572B
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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
- C23F1/00—Etching metallic material by chemical means
- C23F1/10—Etching compositions
- C23F1/14—Aqueous compositions
- C23F1/16—Acidic compositions
- C23F1/28—Acidic compositions for etching iron group metals
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Abstract
The invention belongs to the technical field of metallographic corrosion, and particularly relates to a corrosive agent and a corrosion method for a precipitated phase of duplex stainless steel. The raw materials of the corrosive agent comprise potassium permanganate, nitric acid and water, the corrosion agent can slowly corrode the duplex stainless steel, the corrosion process is easy to control, the over-corrosion phenomenon can be avoided, the precipitated phase in the obtained metallographic structure is clear, and the observation is facilitated. The corrosion method is simple, a precipitated phase with clear microstructure can be obtained at room temperature, and the operation is easy.
Description
Technical Field
The invention belongs to the technical field of metallographic corrosion, and particularly relates to a corrosive agent and a corrosion method for a precipitated phase of duplex stainless steel.
Background
The dual phase steel is a steel composed of ferrite and austenite phases, and generally, the content of a minor phase is required to be 30%. The duplex stainless steel has the advantages of both ferritic stainless steel and austenitic stainless steel, and is mainly applied to the industrial fields of petrochemical equipment, seawater and wastewater treatment equipment, oil and gas pipelines, papermaking machinery and the like and the field of bridge bearing structures.
Certain precipitated phases often exist in the ferrite austenite phase interface of the steel type, and more traditional precipitated phase corrosion methods such as aqua regia, copper sulfate brine solution and 10% oxalic acid electrolysis are not well controlled in the corrosion process, so that the excessive corrosion phenomenon of the precipitated phases of the phase interface after corrosion often occurs, a rough and black curve is presented, and even a groove appears in the phase interface, which is not beneficial to observation and analysis and influences the analysis quality.
Disclosure of Invention
Aiming at the technical problems, the invention provides a corrosive agent and a corrosion method for a precipitated phase of duplex stainless steel. The corrosive agent slowly corrodes the duplex stainless steel, the corrosion process is easy to control, the over-corrosion phenomenon can be avoided, and the obtained metallographic structure has clear precipitated phases and is beneficial to observation. The etching method using the corrosive agent has mild conditions and is easy to operate.
In order to achieve the purpose of the invention, the embodiment of the invention adopts the following technical scheme:
in a first aspect, an embodiment of the present invention provides a corrosive agent for a precipitated phase of duplex stainless steel, where the corrosive agent includes the following raw materials in parts by weight: 1.8 to 2.2 parts of potassium permanganate, 20 to 22 parts of nitric acid and 90 to 110 parts of water.
In the corrosive provided by the invention, potassium permanganate is a strong oxidant and has an oxidation erosion effect on metal; nitric acid is a strong acid and can undergo an acidic attack reaction with stainless steel. According to the invention, potassium permanganate, nitric acid and water in a specific ratio are adopted, so that the corrosive can slowly corrode the duplex stainless steel, the corrosion process is easy to control, the over-corrosion phenomenon can be avoided, and the obtained metallographic structure has clear precipitated phases and is beneficial to observation. Compared with other common acid reagents such as sulfuric acid and the like, the nitric acid adopted by the invention can be used for corroding the duplex stainless steel at room temperature after being matched with potassium permanganate, the time required for corroding until the precipitated phase is clearly displayed is shorter, the precipitated phase with clear microstructure can be obtained in 3-5 minutes, the real-time monitoring and checking are not needed, and the operation is easy.
The corrosive agent has no requirements on the components of the duplex stainless steel, the ferrite-austenite phase ratio and the like, and can obtain a precipitated phase with clear microstructure at normal temperature for the duplex stainless steel with any ferrite-austenite phase ratio.
Preferably, the corrosive agent comprises the following raw materials in parts by weight: 2 parts of potassium permanganate, 21.3 parts of nitric acid and 100 parts of water.
Preferably, the purity of the potassium permanganate is more than or equal to 99 percent.
Preferably, the purity of the nitric acid is more than or equal to 99.5 percent.
High purity potassium permanganate and nitric acid can reduce the impact of impurities on the corrosion process. In practical application, the potassium permanganate and the nitric acid can meet the requirements by adopting analytical purification.
Preferably, the water is deionized water.
In a second aspect, an embodiment of the present invention provides a method for corroding a precipitated phase of duplex stainless steel, which specifically includes the following steps:
the duplex stainless steel is immersed in the corrosive agent at the temperature of 20-30 ℃, taken out after 3-5 minutes, cleaned on the surface by oxalic acid aqueous solution with the volume concentration of 8-12 percent, and then cleaned by water.
The corrosion method utilizes the corrosive to corrode the duplex stainless steel, has mild conditions and simple operation, can completely display the appearance of a precipitated phase on the surface of the duplex stainless steel within 3-5 minutes, and does not have the phenomenon of over corrosion. After being cleaned by oxalic acid with specific concentration, the appearance of a precipitated phase is clearer.
Preferably, the etching method further comprises rinsing with absolute ethanol after the rinsing with water.
Drawings
FIG. 1 is a photograph of the microstructure of a sample obtained after the treatment of example 4;
FIG. 2 is a photograph of the microstructure of the test specimen obtained in comparative example 1.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In the following examples, potassium permanganate and nitric acid were both analytically pure, and water was distilled water.
Example 1
The embodiment provides a corrosive agent for a precipitated phase of duplex stainless steel, which comprises the following raw materials in parts by weight: 2 parts of potassium permanganate, 21.3 parts of nitric acid and 100 parts of water.
The preparation method of the corrosive comprises the following steps: mixing nitric acid and water, and dissolving with potassium permanganate.
Example 2
The embodiment provides a corrosive agent for a precipitated phase of duplex stainless steel, which comprises the following raw materials in parts by weight: 1.8 parts of potassium permanganate, 20 parts of nitric acid and 90 parts of water.
The preparation method of the corrosive comprises the following steps: mixing nitric acid and water, and dissolving with potassium permanganate.
Example 3
The embodiment provides a corrosive agent for a precipitated phase of duplex stainless steel, which comprises the following raw materials in parts by weight: 2.2 parts of potassium permanganate, 22 parts of nitric acid and 110 parts of water.
The preparation method of the corrosive comprises the following steps: mixing nitric acid and water, and dissolving with potassium permanganate.
Example 4
The embodiment provides a corrosion method of a precipitated phase of duplex stainless steel, which is specifically operated as follows:
the corrosive agent obtained in the example 1 is put into a water bath kettle at 23-27 ℃ to keep constant temperature, a duplex stainless steel sample (10 multiplied by 20 mm) to be treated is directly put into the corrosive liquid for 4 minutes, then the corroded sample is taken out, absorbent cotton is dipped in 10% (v/v) oxalic acid aqueous solution for wiping, and finally, water and absolute ethyl alcohol are sequentially used for washing and drying. The microstructure picture of the sample obtained after the treatment is shown in fig. 1.
Example 5
The embodiment provides a corrosion method of a precipitated phase of duplex stainless steel, which is specifically operated as follows:
the corrosive agent obtained in the example 1 is put into a water bath kettle at the temperature of 25-30 ℃ to keep constant temperature, a duplex stainless steel sample (10 multiplied by 20 mm) to be treated is directly put into the corrosive liquid for 3 minutes, then the corroded sample is taken out, absorbent cotton is dipped into 8% (v/v) oxalic acid aqueous solution for wiping, and finally water and absolute ethyl alcohol are sequentially used for washing and drying.
Example 6
The embodiment provides a corrosion method of a precipitated phase of duplex stainless steel, which is specifically operated as follows:
the corrosive agent obtained in the example 1 is put into a water bath kettle at the temperature of 20-25 ℃ to keep constant temperature, a duplex stainless steel sample (10 multiplied by 20 mm) to be treated is directly put into the corrosive liquid for 5 minutes, then the corroded sample is taken out, absorbent cotton is dipped in 12% (v/v) oxalic acid aqueous solution for wiping, and finally water and absolute ethyl alcohol are sequentially used for washing and drying.
Example 7
The embodiment provides a corrosion method of a precipitated phase of duplex stainless steel, which is specifically operated as follows:
the corrosive agent obtained in the example 2 is put into a water bath kettle at 23-27 ℃ to keep constant temperature, a duplex stainless steel sample (10 multiplied by 20 mm) to be treated is directly put into the corrosive liquid for 4 minutes, then the corroded sample is taken out, absorbent cotton is dipped in 10% (v/v) oxalic acid aqueous solution for wiping, and finally water and absolute ethyl alcohol are sequentially used for washing and drying.
Example 8
The embodiment provides a corrosion method of a precipitated phase of duplex stainless steel, which is specifically operated as follows:
the corrosive agent obtained in the example 3 is put into a water bath kettle at 23-27 ℃ to keep constant temperature, a duplex stainless steel sample (10 multiplied by 20 mm) to be treated is directly put into the corrosive solution for 4 minutes, then the corroded sample is taken out, absorbent cotton is dipped in 10% (v/v) oxalic acid aqueous solution for wiping, and finally water and absolute ethyl alcohol are sequentially used for washing and drying.
Comparative example 1
This example provides a method for corroding precipitated phases of duplex stainless steel, wherein the duplex stainless steel to be treated is made of the same material as in example 4. The specific operation is as follows:
putting a corrosive prepared from 2 parts of potassium permanganate, 21.3 parts of sulfuric acid and 100 parts of water into a water bath kettle at 68-72 ℃ to keep constant temperature, directly putting a duplex stainless steel sample (10 multiplied by 20 mm) to be treated into the corrosive liquid, corroding for 4 minutes, taking out the corroded sample, dipping 10% (v/v) oxalic acid aqueous solution into absorbent cotton, wiping the corroded sample, sequentially washing the sample with water and absolute ethyl alcohol, and drying the sample by blowing. The microstructure picture of the sample obtained after the treatment is shown in figure 2, and black precipitated phases can be seen on the surface of the duplex stainless steel, which indicates that the corrosion can be over-corroded under the corrosion condition.
Putting a corrosive agent prepared from 2 parts of potassium permanganate, 21.3 parts of sulfuric acid and 100 parts of water into a water bath kettle at the temperature of 25-30 ℃ to keep constant temperature, directly putting a duplex stainless steel sample (10 multiplied by 20 mm) to be treated into the corrosive solution, corroding for 4 minutes, taking out the sample, dipping 10% (v/v) oxalic acid aqueous solution into absorbent cotton to wipe the sample, finally washing the sample with water and absolute ethyl alcohol in sequence, and drying the sample by blowing. The microstructure of the treated sample was observed, and no precipitated phase was observed.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents or improvements made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (6)
1. A corrosion method of a precipitated phase of duplex stainless steel is characterized in that the duplex stainless steel is immersed in a corrosive agent at the temperature of 20-30 ℃, is taken out after 3~5 minutes, is cleaned on the surface by oxalic acid aqueous solution with the volume concentration of 8-12%, and is then cleaned by water; the corrosive comprises the following raw materials in parts by weight: 1.8 to 2.2 parts of potassium permanganate, 20 to 22 parts of nitric acid and 90 to 110 parts of water.
2. The method for corroding precipitated phases of duplex stainless steel according to claim 1, wherein the corrosive agent comprises the following raw materials in parts by weight: 2 parts of potassium permanganate, 21.3 parts of nitric acid and 100 parts of water.
3. The method for corroding precipitated phases of duplex stainless steel according to claim 1 or 2, wherein the purity of the potassium permanganate is not less than 99%.
4. The method of corroding precipitated phases of duplex stainless steel according to claim 1 or 2, wherein the purity of said nitric acid is not less than 99.5%.
5. A method of corrosion of precipitated phases of duplex stainless steel according to claim 1 or 2, characterized in that said water is deionized water.
6. The method of corroding precipitated phases of duplex stainless steel according to claim 1 further comprising rinsing with absolute ethanol after rinsing with water.
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| CN108051441A (en) * | 2017-11-29 | 2018-05-18 | 西部金属材料股份有限公司 | A kind of observation procedure of Fe-Ni-Cr alloy microstructure |
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| CA1214667A (en) * | 1983-01-05 | 1986-12-02 | Terry A. Debold | Duplex alloy |
| CN103743615A (en) * | 2014-01-23 | 2014-04-23 | 国家电网公司 | Medium/low-alloy heat-resistant steel metallographic phase polishing etching reagent and treatment method thereof |
| CN107761100A (en) * | 2016-08-18 | 2018-03-06 | 宝山钢铁股份有限公司 | Medium high carbon high-strength steel prior austenite grain size visualizingre agent and its application method |
| CN106757031B (en) * | 2016-11-30 | 2019-03-12 | 振石集团东方特钢有限公司 | A kind of high alloyed austenitic body microscopic structure of stainless steel and σ interphase colour corrosive agent and caustic solution |
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| CN108051441A (en) * | 2017-11-29 | 2018-05-18 | 西部金属材料股份有限公司 | A kind of observation procedure of Fe-Ni-Cr alloy microstructure |
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