CN112763296B - A three-dimensional etching method for chromium-manganese stainless steel inclusions - Google Patents

Abstract

The invention discloses a three-dimensional current corrosion etching method for inclusions in chromium-manganese stainless steel, which belongs to the field of metal material detection. The present invention provides a new type of three-dimensional etching solution, and carries out current directional etching in the new type of etching solution configured by a neutral solvent, a complexing agent and a conductive agent according to a given method and etching parameters, so that the steel substrate Partially dissolves, and the inclusions do not dissolve, thereby exposing the spatial morphology of the inclusions and retaining the spatial position information of the inclusions, so that the morphology and distribution of the inclusions in stainless steel can be observed in situ without extraction. The sample required by this method is small, usually a few grams; the etching time is short and the efficiency is high, and the etching can usually be completed in ten to tens of minutes; the device is simple and the operation is flexible, and after the etching is completed, it can be used with scanning electron microscope equipment Observation, photography and statistics of inclusions to obtain the three-dimensional shape of inclusions and in-situ distribution information in steel are of great help to accurately grasp the spatial distribution and morphological characteristics of inclusions in steel and obtain the in-situ distribution characteristics of inclusions.

Description

A three-dimensional etching method for chromium-manganese stainless steel inclusions

technical field

The invention relates to the field of metal material detection, in particular to a method for in-situ electrolytic corrosion of non-metallic inclusions in Mn stainless steel.

Background technique

According to the national standard GB/T 13304-1991 "Steel Classification" and the international general classification method, according to the metallographic structure of steel, stainless steel is divided into austenite type, ferrite type, martensite type, austenite-iron There are 5 types of element body duplex and precipitation hardening type.

According to its chemical composition, austenitic stainless steel is divided into two series of chromium-nickel series (300 series in the United States) austenitic stainless steel and chromium-manganese series (200 series in the United States) austenitic stainless steel. Chromium-manganese (200 series) austenitic stainless steel is developed on the basis of chromium-nickel austenitic stainless steel, adding manganese and (or) nitrogen to steel instead of precious metal nickel. Its austenitic elements, In addition to manganese, there is nitrogen, and generally there is an appropriate amount of nickel (4% to 6%). Manganese in steel plays a role in stabilizing austenite. Since nitrogen strongly forms and stabilizes austenite and plays a good role in solid solution strengthening, which improves the strength of austenitic stainless steel, this series of stainless steel is suitable for heavy loads and low corrosion resistance requirements. used on equipment and components.

With the improvement of customers' requirements on the quality and performance of steel materials, the removal and control of inclusions in steel are more and more valued by metallurgists. How to effectively remove inclusions and control the shape of inclusions, first of all, it is necessary to control the inclusions Have a clear understanding of the real size and shape characteristics. The non-metallic inclusions that exist discontinuously in stainless steel are the main factors that endanger the corrosion resistance and other structural properties of stainless steel. The size, shape, distribution and other parameters of non-metallic inclusions in steel have an important impact on the uniformity of steel structure. . Usually, metallographic microscopes or scanning electron microscopes are used to observe parameters such as size, shape, and distribution of non-metallic inclusions. However, after the sample is ground and polished, only a certain section of the non-metallic inclusions can be seen under the electron microscope, and the real three-dimensional shape of the non-metallic inclusions in the steel cannot be observed. Therefore, the three-dimensional characterization of non-metallic inclusions in chromium-manganese stainless steel is an important means to accurately grasp the spatial distribution, shape and size of inclusions, and it is of great significance to improve the quality of steel.

At present, the reported methods for extracting non-metallic inclusions generally include acid dissolution and electrolysis. The acid dissolution method has been developed very early and widely used. It uses various concentrations of HNO ₃ , H ₂ SO ₄ , HCl and aqueous solutions to dissolve the metal matrix, and some stable inclusions that are not dissolved by acid can be retained. For the acid-dissolution method, see the literature "Study on the Three-dimensional Morphology of Ultrafine Oxide Inclusions in Steel by Acid-dissolution Method" (Journal of Iron and Steel Research, 2007, 4). Electrolytic etching technology is a three-dimensional characterization method of sulfide that is different from electrolytic extraction technology. Electrolytic extraction usually adopts two methods of aqueous solution large-sample electrolysis and non-aqueous solution small-sample electrolysis. After the steel matrix is completely dissolved, the characterization method of inclusions is obtained by extraction. The electrolysis time is long, and the sulfide filtration is complicated and difficult to operate. The main process is: sample electrolysis → anode cleaning → elutriation → magnetic separation → reduction → washing → drying → weighing → sulfide composition or performance testing. Compared with electrolytic extraction, the electrolytic three-dimensional etching technology is characterized in that only part of the matrix is electrolyzed, and the three-dimensional morphology of the inclusions in the matrix is exposed in situ.

The electrolyte usually used in the aqueous solution electrolysis method is an acidic aqueous solution, which is similar to the acid solution method. Many inclusions in the steel will be destroyed in the acidic aqueous solution, and this electrolysis method can only completely retain the inclusions larger than The smaller inclusions cannot be accurately evaluated, so this method needs to be improved. In the book "Non-metallic Inclusions in Steel", there are 7 kinds of non-aqueous electrolytes mentioned, but the steel types that these electrolytes can extract There is a big limitation with the inclusion type, or for a steel grade, or for a type of inclusion. In addition, there is no description of the value of the electrolyte. Without a value, it is difficult to explain the damage of the electrolyte to the inclusions. More importantly, the filtration method is used when extracting the inclusions. This method is very useful for extracting nanoscale inclusions. Difficult to achieve because ultrafine inclusions are difficult to separate from the filter paper. In addition, it takes a long time to filter and separate by filter paper, and the separation efficiency is low. Therefore, these methods also need to be improved.

Chinese patent CN101736392A discloses an electrolyte and a method for electrolytically extracting non-metallic inclusions in steel. The proportion of the electrolyte is 1% to 1.5% of tetramethylammonium chloride and 6% to triethanolammonium by weight percentage. 10%, glycerin 6% ~ 10%, diphenylguanidine 0.6% ~ 1%, the balance is anhydrous methanol, adjust the current density to 40-100mA/cm2 during electrolysis; control the temperature of the electrolyte to -5 ~ 5 °C, during the electrolysis, argon gas is continuously fed into the electrolytic cell with a flow rate of 0.1-0.3 liters/min, and then the electrolytic solution is centrifugally separated by a centrifuge. The present invention is different from the above-mentioned inventions in that: (1) the above-mentioned invention adopts the method of electrolysis-centrifugation-magnetic attraction-separation, and the operation process is relatively complicated, while the present invention adopts the method of in-situ electrolysis, which abandons the complexity of centrifugal-magnetic attraction-separation method, not only makes the operation easier, but also captures the distribution differences of non-metallic inclusions in steel in different regions of the sample surface, avoiding errors when observing the second phase particles; (2) the present invention proposes a new three-dimensional corrosion etching Liquid, non-toxic and less time-consuming, can achieve the purpose of rapid electrolysis.

Chinese patent CN106596669A discloses a non-destructive detection device and method for sulfide-based inclusions in steel. A non-destructive detection device and method for sulfide-based inclusions in steel. Potentiometer, hydrogen bottle, flow meter, computer and several cellulose acetate plastic bags Detection method Sample preparation and electrolyte preparation The electrolyte is composed of anhydrous chloride file, γ-butyrolactone, glycerin and absolute ethanol, mixed uniformly, Electrolyte was obtained; the pH of the electrolyte was controlled by citric acid solution to be 7-9 at the beginning of electrolysis, and the total electrolysis was 12-36h. After the electrolysis was over, the steel sample and the cellulose acetate plastic bag were cleaned respectively with absolute ethanol, and then weighed Steel samples, magnetic separation and cleaning liquid are classified and filtered under vacuum to separate the sulfide-based inclusions. The device and method of the present invention are different from the above-mentioned inventions in that: the above-mentioned invention adopts the method of magnetic separation and classified filtration, and the present invention The advantage of the in-situ electrolysis method is that the operation process is relatively simple, and the direct appearance and distribution of non-metallic inclusions in chromium-manganese stainless steel can be directly observed, which can effectively avoid the occurrence of non-metallic inclusions in steel. Error analysis, and less time spent, can achieve the purpose of fast electrolysis.

Chinese patent CN110161066A discloses a method for extracting inclusions in steel by non-aqueous solution. Under certain electrolysis parameters, the inclusions and steel matrix are electrolyzed into the non-aqueous solution, and then the inclusions are extracted and separated by centrifugation. The composition (mass percentage) of the non-aqueous electrolyte is 10% acetylacetone, 0.7% tetramethylammonium chloride, 1-5% ammonium thiocyanate, and the rest is anhydrous methanol. The parameters of electrolysis are: the voltage is 2-5V, and the current is 0.04-0.05A/cm ² . The present invention is different from the above-mentioned inventions in that: (1) the above-mentioned invention adopts a centrifugal method, and the operation is relatively complicated, and the present invention does not need to be separated; (2) the electrolytic solution of the above-mentioned invention contains acetylacetone, which is harmful to the human body. The new electrolyte formula does not use acetylacetone, which is harmless to the human body; (3) the present invention adopts the method of in-situ electrolysis, which does not require the extraction process, and can be in-situ electrolyzed on the metal substrate, in-situ analyzed, and can directly observe the inclusions in the steel The original three-dimensional shape of the object and its distribution in the steel greatly improve the efficiency of the experiment.

Chinese patent CN102818723A discloses a method for electrolyzing and extracting fine inclusions in steel. Afterwards, the electrolyte is separated and the inclusions are collected. The collected inclusions are placed in a volatile solvent for ultrasonic dispersion with an ultrasonic cleaner, and then the ultrasonically dispersed solution is dropped on the carrier drop by drop with a micropipette until the solvent volatilizes. Finally, the carrier scattered with inclusions was placed into a scanning electron microscope for analysis. The present invention is different from the above-mentioned invention in that: the above-mentioned invention uses magnetic separation and centrifugation to collect inclusions, and then uses ultrasonic dispersion. The method of magnetic separation and centrifugation to collect inclusions makes the operation process relatively simple. At the same time, the direct morphology and distribution of non-metallic inclusions in chromium and manganese stainless steels can be directly observed in situ.

Chinese patent CN111596094A discloses a three-dimensional etching device and etching method for non-metallic inclusions in steel (9 kinds of electrolytic formulas are provided), through a given etching device, the etching operation is performed according to a given method and etching parameters , in the etching solution prepared by neutral solvent, complexing agent and conductive agent, the current directional etching is carried out, so that the steel matrix is partially dissolved, and the inclusions are not dissolved, thereby exposing the spatial morphology of the inclusions and retaining the space of the inclusions For location information, the electrolysis temperature is -15°C to 45°C, and the current density is 20 to 300mA/cm ² . The present invention is different from the above-mentioned inventions in that: the present invention adopts a completely different etching solution formula for chromium-manganese stainless steel, and the formula is 0.8-2.2% EDTA, 1.1-2.4% aminotriacetic acid (NTA ), 0.9-2.2% quinoline-2-carboxylic acid (QCA), 1.2-2.6% sodium citrate, 5-6% lithium chloride and the balance absolute ethanol. The advantage is that it is non-toxic, and has a better electrolytic effect for chromium-manganese stainless steel, and can directly observe the direct morphology and distribution of non-metallic inclusions in chromium-manganese stainless steel in situ.

Contents of the invention

In order to achieve rapid electrolytic corrosion of non-metallic inclusions in austenitic stainless steel, 200 series stainless steel with different contents was electrolyzed with a specific electrolytic solution.

The invention relates to an electrolytic solution comprising a neutral solvent, an electrolytic reaction conductive agent and a matrix element complexing agent. According to the content of different steel components, the three-dimensional shape information of different inclusions in steel is analyzed. In order to achieve the above observation effect, the present invention provides a three-dimensional electrolytic etching method and device for non-metallic inclusions in 200 series stainless steel, which is suitable for the chemical composition of stainless steel: C: ≤0.3%, Mn: 4-16% , P: ≤0.06%, Si: ≤0.8%, S: ≤0.5%, Cr: 12-18%, N: ≤0.25%.

A three-dimensional etching method for chromium-manganese stainless steel inclusions, specifically:

a. The method is aimed at chromium-manganese stainless steel, and the mass percentage of the chemical composition of the material satisfies: the chemical composition is: C: ≤0.3%, Mn: 4-16%, P: ≤0.06%, Si: ≤0.8%, S: ≤0.5%, Cr: 12～18%, N: ≤0.25%; the microstructure of the material is austenite;

b. The electrolyte composition used in the method is: 1.0～4.5% EDTA, 1.2～3.2% aminotriacetic acid (NTA), 0.9～3.2% quinoline-2-carboxylic acid (QCA), 1.0～3.6% Sodium citrate, 4-6% lithium chloride and the balance absolute ethanol;

c. The initial electrolysis temperature used in the method is -10-10°C; the electrolysis current density is 200-300mA/cm ² ; the etching time: 20-40min.

The preferred composition of chromium-manganese stainless steel is: Mn: 5.5-6%, Cr: 16-17%. The electrolyte composition is preferably: volume percentage: 1.8% EDTA, 2.16% aminotriacetic acid (NTA), 1.5% quinoline-2 -Carboxylic acid (QCA), 1.65% sodium citrate, 4.7% lithium chloride and the balance absolute ethanol;

The preferred composition of chromium-manganese stainless steel is: Mn: 8-9%, Cr: 17-18%. The electrolyte composition is preferably: volume percentage: 2.9% EDTA, 2.5% aminotriacetic acid (NTA), 2.1% quinoline-2 - Carboxylic acid (QCA), 2.3% sodium citrate, 5.5% lithium chloride and the balance absolute ethanol.

It is preferable to use a series circuit and multiple electrolytic cells to electrolyze multiple samples at the same time to improve the experimental efficiency.

The three-dimensional etching device of the present invention includes: an anode, a fixture, an etching solution, a sample, a constant current source, a cathode, a platinum sheet, and a constant temperature tank. Connection device method: pour the electrolyte into the electrolytic inner tank, pour the cooling liquid into the outer tank of the electrolytic tank, in order to maintain good current stability, the cathode and anode clamps are made of stainless steel, the length of the cathode is 80mm, and the width is 15mm long stainless steel sheet with a thickness of 2mm. Fix the sample on the anode with a clamp, and make sure that the bottom of the anode clamp is at the same level as the cathode. The top position of the anode fixture and the cathode is fixed with an insulating rubber rod, and the anode and the cathode are fixed on the upper cover to ensure that the anode and the cathode do not touch the inner wall of the electrolytic etching tank, and the cathode material during the etching process has less pollution to the electrolyte , which is beneficial to observe the inclusions on the surface of the sample after the etching is completed.

The three-dimensional etching reagent of the present invention is prepared from a neutral solvent, an electrolytic reaction conductive agent, and a matrix element complexing agent in a certain proportion. The volume percentage of each component in the electrolytic etching solution provided by the present invention is respectively: 1.0～4.5% EDTA, 1.2～3.2% aminotriacetic acid (NTA), 0.9～3.2% quinoline-2-carboxylic acid (QCA) , 1.0-3.6% sodium citrate, 4-6% lithium chloride and the balance absolute ethanol. The main functions of each reagent in the electrolysis process of the present invention are as follows:

EDTA: It can be complexed with metal ions such as Fe, Mn and Cr, as a basic complexing agent (volume percentage is generally 1.0-4.5%);

Aminotriacetic acid (NTA): mainly used for complexing Cr ions (volume percentage is generally 1.2-3.2%);

Quinoline-2-carboxylic acid (QCA): used as an electrolyte additive to prevent excessive dissolution of the anode metal electrode, greatly improving its service life and cycle capacity (volume percentage is generally 0.9 to 2.2%);

Sodium citrate: mainly used for complexing Mn ions (volume percentage is generally 1-3.6%);

Lithium chloride: used as a conductive agent for electrolytic reactions (volume percentage is generally 4 to 6%);

Absolute ethanol: as a neutral solvent.

For Mn: 5.5-6%, Cr: 16-17%, the optimal ratio is adopted: the volume percentage is: 1.8% EDTA, 2.16% aminotriacetic acid (NTA), 1.5% quinoline-2-carboxylic acid (QCA) , 1.65% sodium citrate, 4.7% lithium chloride and the balance absolute ethanol;

For Mn: 8-9%, Cr: 17-18%, the optimal ratio is adopted: the volume percentage is: 2.9% EDTA, 2.5% aminotriacetic acid (NTA), 2.1% quinoline-2-carboxylic acid (QCA) , 2.3% sodium citrate, 5.5% lithium chloride and the balance absolute ethanol.

The specific process of three-dimensional etching in the present invention comprises:

(1) Sample preparation and electrolyte preparation

Prepare the electrolyte solution as described above. Using cutting equipment, the sample is made into a regular cube with a volume of 10mm×10mm×10mm, and the surface of the sample to be observed is polished with 240, 400, 600, 800, 1000, 1500, 2000 mesh sandpaper in turn, polished with polishing paste, and then rubbed with alcohol. Rinse, dry, and wait for electrolysis. When the sample is thin or irregular, the electrolyzed side should face the cathode with the stainless steel fixture.

(2) Adjust the electrolysis temperature

Regulate the temperature of the cooling liquid in the electrolytic constant temperature tank, so that the etching temperature is -10 ° C ~ 10 ° C; the temperature rises, the reaction speed is accelerated, which is beneficial to shorten the reaction time, the activity of the inclusions will also increase, and it is easy to dissolve in the etching liquid. However, it is difficult to control the etching effect; when the temperature is lowered, the electrochemical reaction speed of the anode Fe is slower than that of the ion diffusion in the solution, resulting in electrochemical polarization, the etching time is long, and the etching efficiency is greatly reduced, but the etching effect is easy to control; It has been repeatedly verified that when the etching temperature is between -10°C and 10°C, the overall etching effect and etching efficiency are better.

(3) Select the current density

Appropriately increasing the current density is conducive to accelerating ion diffusion and improving electrolysis efficiency, but if the current density is too high, the dissolution of the steel matrix will be accelerated, and it is difficult to control the corrosion effect. At the same time, non-metallic inclusions in the steel are easy to fall off from the matrix, which affects the non- Observation of the original morphology of metal inclusions; when the current density is low, the dissolution of the steel matrix is too slow, although the corrosion effect can be better controlled, but the efficiency is too low, which affects the progress of the experiment. For chrome-manganese stainless steel, the current density is set to 200-300A/cm ² , at this time, the etching effect and etching efficiency can be well controlled.

(4) Corrosion process

After adjusting the etching parameters, start etching; the sample is etched in the electrolyte, the matrix of the observation surface is gradually dissolved, and the non-metallic inclusions are gradually exposed; under the same conditions as other parameters, the etching time is appropriately extended, The more the inclusions are exposed, but when the time exceeds a certain range, the inclusions will fall off from the steel matrix, and black cavities will be observed under the scanning electron microscope, and the morphology of non-metallic inclusions in the steel cannot be observed. For chromium-manganese stainless steel, the corrosion etching time is usually 25-40 minutes for the best effect.

(5) Sample post-processing

After the etching is completed, the sample is cleaned with absolute ethanol and dried in a drying oven;

(6) Observation, photography, analysis and statistics

Then use optical microscope and scanning electron microscope analysis instrument to observe and photograph the inclusions of the etched samples, and analyze and count them. until the effect of exposure.

Description of drawings

Figure 1: Electrolytic etching device;

Figure 2 Example 1: SEM image of 201 stainless steel-etched 200mA/cm ² inclusions.

Fig. 3 Example 2: SEM image of 201 stainless steel-etched 300mA/cm ² inclusions.

Figure 4 Example 3: 202 stainless steel - SEM image of inclusions etched for 30 minutes.

Figure 5 Example 4: 202 stainless steel - SEM picture of inclusions etched for 40 minutes.

Figure 6 Comparative Example 1: SEM image of 201 stainless steel-etched 300mA/cm ² inclusions.

Figure 7 Comparative Example 2: 202 stainless steel - SEM picture of inclusions etched for 30 minutes.

Detailed ways

Embodiment one:

A device for in-situ electrolytic etching of non-metallic inclusions in chromium and manganese series stainless steel, as shown in Figure 1, the device includes: 1. anode, 2. fixture, 3. etching solution, 4. sample, 5. Constant current source, 6. Cathode, 7. Platinum sheet, 8. Constant temperature bath. The connection method of the electrolytic etching device is: (1) connect the wire to the anode fixture and one end of the cathode stainless steel sheet, and connect the other end to the regulated power supply; (2) fix the sample on the anode to ensure that the sample is firm Loosen; (3) Put the cathode and anode into the constant temperature tank respectively, and keep the distance between the cathode and the anode at 30-60mm; (4) Add electrolyte to ensure that the liquid level of the electrolyte is below the highest position of the sample by 8-15mm , but far below the connection point between the wire and the cathode and anode; (5) Make the height of the electrolyte and the liquid level of the antifreeze basically the same, cover the cover of the constant temperature bath (6) check the circuit, and turn on the power. Carry out the electrolytic operation according to the given steps of the corrosion etching method: the steel sample, corrosion etching parameters, and implementation effects of this embodiment are as follows:

Electrolytic etching of 201 stainless steel (chemical composition: C: 0.1%, Si: 0.8%, Mn: 5.9%, P≤0.06%, S: 0.03%, Cr: 16.8%, N: 0.20%);

Grinding and polishing 201 stainless steel, sample size 10mm×10mm×10mm, weight 7.6g, corrosion parameters are:

For this etching solution, adopt preferred scheme 1, the volume percent of this etching solution is: 1.8% EDTA, 2.16% aminotriacetic acid (NTA), 1.5% quinoline-2-carboxylic acid (QCA), 1.65% lemon sodium chloride, 4.7% lithium chloride and the balance absolute ethanol;

Corrosion temperature: 0 ℃;

Corrosion current density: 200mA/cm ² ;

Carving time: 25min;

The effect of Embodiment 1 is shown in Figure 2.

Embodiment two:

Electrolytic etching of 201 stainless steel (chemical composition: C: 0.1%, Si: 0.8%, Mn: 5.9%, P≤0.06%, S: 0.03%, Cr: 16.8%, N: 0.20%);

Grinding and polishing 201 stainless steel, sample size 10mm×10mm×10mm, weight 7.6g, corrosion parameters are:

For this etching solution, adopt preferred scheme 1, the volume percent of this etching solution is: 1.8% EDTA, 2.16% aminotriacetic acid (NTA), 1.5% quinoline-2-carboxylic acid (QCA), 1.65% lemon sodium chloride, 4.7% lithium chloride and the balance absolute ethanol;

Corrosion temperature: 0 ℃;

Corrosion current density: 300mA/cm ² ;

Carving time: 25min;

Corrosion results are shown in Figure 3. Under the same electrolytic etching time and electrolytic etching temperature, the exposure effect of inclusions increases with the increase of current density; when the current density is 200mA/ ^cm2 , 300mA/cm ² , the large-sized inclusions are exposed more completely, and at the same time, the small-grained inclusions will break away from the matrix, resulting in analysis errors. Therefore, it is better to control the current density at 200mA/cm ² in this embodiment.

Embodiment three:

Electrolytic corrosion of 202 stainless steel (chemical composition: C: 0.1%, Si: 0.7%, Mn: 8.9%, P≤0.06%, S: 0.03%, Cr: 17.8%, N: 0.20%); The stainless steel is ground and polished, the sample size is 10mm×10mm×10mm, the weight is 7.8g, and the corrosion parameters are:

For this etching solution, adopt preferred scheme 2, the volume percent of this etching solution is: 2.9% EDTA, 2.5% aminotriacetic acid (NTA), 2.1% quinoline-2-carboxylic acid (QCA), 2.3% lemon sodium chloride, 5.5% lithium chloride and the balance absolute ethanol;

Corrosion temperature: 0 ℃;

Carving time: 30min;

Corrosion current density selection: 300mA/cm ² ;

The etching effect of this method is shown in Figure 5.

Embodiment four:

Electrolytic corrosion of 202 stainless steel (chemical composition: C: 0.1%, Si: 0.7%, Mn: 8.9%, P≤0.06%, S: 0.03%, Cr: 17.8%, N: 0.20%); The stainless steel is ground and polished, the sample size is 10mm×10mm×10mm, the weight is 7.5g, and the corrosion parameters are:

For this etching solution, adopt preferred scheme 2, the volume percent of this etching solution is: 2.9% EDTA, 2.5% aminotriacetic acid (NTA), 2.1% quinoline-2-carboxylic acid (QCA), 2.3% lemon sodium chloride, 5.5% lithium chloride and the balance absolute ethanol;

Corrosion temperature: 0 ℃;

Carving time: 40min;

Corrosion current density selection: 300mA/cm ² ;

The implementation effect is shown in Figure 6. Under the same etching current density and etching temperature, the effect of inclusion exposure is better as the etching time increases; when the etching time is 40 minutes, small particles are included and detached matrix. Therefore, it is better to control the etching time in this embodiment to 30 minutes.

Comparative example one:

Electrolytic etching of 201 stainless steel (chemical composition: C: 0.1%, Si: 0.8%, Mn: 5.9%, P≤0.06%, S: 0.03%, Cr: 16.8%, N: 0.20%);

The volume percentage of etching solution is: 6% (m/V) tetramethylammonium chloride + 18% acetylacetone + balance methanol;

Corrosion temperature: 0 ℃;

Corrosion current density: 200mA/cm ² ;

Carving time: 35min;

The implementation effect is shown in Figure 4. Compared with Example 1, under the same current density, the etching time is longer and the etching effect is not good.

Comparative example two:

Electrolytic etching of 202 stainless steel (chemical composition: C: 0.1%, Si: 0.7%, Mn: 8.9%, P≤0.06%, S: 0.03%, Cr: 17.8%, N: 0.20%);

The volume percentage of etching solution is: 6% (m/V) tetramethylammonium chloride + 18% acetylacetone + balance methanol;

Corrosion temperature: 0 ℃;

Corrosion current density: 300mA/cm ² ;

Carving time: 40min;

The implementation effect is shown in Figure 7. Under the same current density, the etching time is greatly prolonged, and the electrolytic etching effect is far inferior to that of Example 3.

Claims (3)

1. A three-dimensional etching method for chromium-manganese stainless steel inclusions is characterized by comprising the following steps:

a. aiming at the chromium-manganese stainless steel, the method has the following chemical components in percentage by mass: the chemical components are as follows: c: less than or equal to 0.3 percent, mn: 5.5-6%, P: less than or equal to 0.06 percent, si: less than or equal to 0.8 percent, S: less than or equal to 0.5 percent, cr: 16-17%, N: not more than 0.25 percent, and the normal-temperature microstructure of the material is austenite;

b. the electrolyte adopted by the method comprises the following components: 1.8% EDTA, 2.16% nitrilotriacetic acid (NTA), 1.5% quinoline-2-carboxylic acid (QCA), 1.65% sodium citrate, 4.7% lithium chloride and the balance anhydrous ethanol;

c. the electrolysis temperature adopted by the method is-10 ℃; the electrolytic current density is 200-300mA/cm ² (ii) a Etching time: 20-40 min.

2. A three-dimensional etching method for chromium-manganese stainless steel inclusions is characterized by comprising the following steps:

a. aiming at the chromium-manganese stainless steel, the method has the following chemical components in percentage by mass: the chemical components are as follows: c: less than or equal to 0.3 percent, mn:8 to 9%, P: less than or equal to 0.06 percent, si: less than or equal to 0.8 percent, S: less than or equal to 0.5 percent, cr: 17-18%, N: not more than 0.25 percent, and the normal temperature microstructure of the material is austenite;

b. the electrolyte adopted by the method comprises the following components: 2.9% EDTA, 2.5% nitrilotriacetic acid (NTA), 2.1% quinoline-2-carboxylic acid (QCA), 2.3% sodium citrate, 5.5% lithium chloride and the balance anhydrous ethanol;

c. the electrolysis temperature adopted by the method is-10 ℃; the electrolytic current density is 200-300mA/cm ² (ii) a Etching time: 20-40 min.

3. The three-dimensional etching method for chromium-manganese stainless steel inclusions according to claim 1 or 2, characterized by comprising the following steps: in order to improve the experimental efficiency, a series circuit and a plurality of electrolytic cells are adopted to electrolyze a plurality of samples simultaneously.

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