Rapid sample preparation method of stainless steel oxygen, nitrogen and hydrogen detection sample

Abstract

The invention discloses a rapid sample preparation method of a stainless steel oxygen, nitrogen and hydrogen detection sample, which comprises the following steps: 1) electrolyzing to remove oxides: taking a stainless steel sample to be detected as an anode and an MMO titanium-based platinum coating electrode as a cathode, and electrolyzing in a sulfuric acid-hydrogen peroxide mixed electrolyte at the current density of 5-25 A / dm, the temperature of 15-30 DEG C and the time of 30-120 s; 2) hydraulic shearing: shearing the electrolyzed sample into particles with the mass of 0.5-1.2 g; (3) stepped ultrasonic cleaning, wherein absolute ethyl alcohol ultrasonic cleaning and acetone ultrasonic cleaning are sequentially adopted; and 4) drying. The hydrogen evolution reaction is effectively inhibited through the cathode depolarization effect of hydrogen peroxide, hydrogen element loss or pollution is avoided, surface residues are thoroughly removed in combination with stepped ultrasonic cleaning, mechanical high temperature and abrasive contact do not exist in the whole process, external oxygen and nitrogen interference is completely eradicated, the accuracy of analysis results is improved, reproducibility is excellent, and the method is suitable for industrial production. The method is especially suitable for on-the-spot quick analysis and batch detection scenes.

Description

Technical Field

[0001] This invention belongs to the field of test sample preparation technology, specifically relating to a rapid sample preparation method for stainless steel oxygen, nitrogen, and hydrogen detection samples. Background Technology

[0002] The oxygen, nitrogen, and hydrogen content in stainless steel is a key indicator for evaluating its metallurgical quality and overall performance, directly affecting the material's strength, toughness, corrosion resistance, resistance to hydrogen embrittlement, and weldability. Especially in high-end equipment manufacturing and new energy fields, the control requirements for these three gaseous elements are extremely stringent. Therefore, accurate and rapid determination of oxygen, nitrogen, and hydrogen content is crucial for material quality control.

[0003] Currently, the industry typically prepares test samples by mechanical turning or grinding, followed by shearing and cleaning, and then performs elemental analysis using inert gas melting thermal conductivity or infrared spectroscopy. However, existing sample preparation methods have the following inherent drawbacks in practical applications: 1. Hydrogen distortion: The local high temperature generated during machining (which can easily exceed the hydrogen diffusion critical temperature of 200~300℃) will cause hydrogen on the sample surface and near the surface to diffuse out rapidly, resulting in a significantly lower hydrogen content detection result. At the same time, the coolant and lubricant used in the machining process may introduce additional hydrogen contamination, further interfering with the accuracy of the detection.

[0004] 2. Abnormal oxygen element detection: During mechanical turning or grinding, abrasive particles from cutting tools and sandpaper (such as those made of alumina or silicon carbide) can easily embed into the stainless steel matrix, introducing external oxygen contamination and leading to higher oxygen analysis results. In addition, the high temperature generated during machining can cause the formation of oxide films such as Fe3O4 on the sample surface, which not only exacerbates the oxygen content detection deviation but also causes oxygen peak tailing, affecting the stability of the detection data.

[0005] 3. Low efficiency and throughput bottleneck: Traditional methods rely on manual processing of samples one by one, using mechanical turning or grinding. The preparation of a single sample often takes 6-12 minutes, which is difficult to match the production rhythm of rapid smelting and cannot meet the urgent need for rapid pre-furnace analysis to guide production. At the same time, this method is difficult to achieve batch and parallel sample preparation. When faced with large-scale testing tasks, the overall processing capacity becomes a significant bottleneck, limiting the response speed and capacity of analytical laboratories.

[0006] The advantages and disadvantages of traditional sample preparation methods for oxygen, nitrogen, and hydrogen analysis of stainless steel are shown in Table 1:

[0007] Chinese patent CN1962963A discloses a method for removing oxide scale from the surface of stainless steel workpieces using an electrolytic process. The key technical point of this patent is that a prepared electrolyte is delivered to an electrolytic cell, and the stainless steel workpiece is placed in the cell, using a stainless steel plate as the cathode and the stainless steel workpiece as the anode, with direct current applied for electrolysis; the electrolysis current density is 10~80 A / dm³. 2 The voltage is 10~12 volts, the temperature is 60℃, and the time is 1~3 minutes. It is especially suitable for removing oxide scale from the surface of hot-formed stainless steel workpieces.

[0008] Chinese patent CN101824645A discloses a method for removing oxide scale from the surface of stainless steel using micro-arc. The method involves using the stainless steel part to be treated as the anode and the stainless steel part as the cathode in the treatment solution of an electrolytic cell, and applying a certain voltage between the anode and cathode to generate micro-arc discharge at the interface between the treatment solution and the stainless steel part to be treated. The generated micro-arc removes the oxide scale from the surface of the stainless steel part to be treated.

[0009] Chinese patent CN103906864A discloses a method for pickling stainless steel in an oxidizing electrolytic acid bath. This method uses stainless steel strip as one of the electrodes, employs a sulfuric acid-hydrogen peroxide composite electrolyte system, and applies current using an electrode assembly arranged in a cathode-anode-cathode configuration. The ferrous sulfate generated during pickling is converted to ferric sulfate, and the strong oxidizing properties of ferric sulfate promote the stripping of chromium-rich oxide scales from the stainless steel surface. This method aims to reduce the use of hydrofluoric acid and nitric acid, lower environmental costs and material consumption, and improve the pickling efficiency of continuous production lines. The current density of this process is 1~100 A / dm³. 2 The temperature ranges from 21 to 82℃.

[0010] The aforementioned electrolysis-related patents aim to improve the appearance and surface quality of industrial-grade stainless steel workpieces or strips. Their process parameters are designed around efficiency and cost control for large-scale production, failing to consider core requirements for analytical sample preparation such as "no significant damage to the matrix, no elemental contamination, and no hydrogen permeation." Existing processes for removing stainless steel oxide scale allow for a small amount of dissolution of the stainless steel matrix to improve descaling efficiency, and post-treatment only includes simple rinsing and drying. Directly using these processes for analytical sample preparation will lead to the following problems: 1. The electrolysis process did not suppress the hydrogen evolution side reaction, which may cause hydrogen atoms to penetrate into the sample or existing hydrogen to escape, interfering with the hydrogen content detection results; 2. Trace dissolution of the matrix can alter the original chemical composition of the sample, affecting the accuracy of component analysis; 3. The post-processing procedure is crude, and electrolyte residue may introduce external contaminants such as oxygen and nitrogen, which cannot meet the sample cleanliness requirements for high-precision gas element analysis.

[0011] In summary, while existing industrial electrolytic descaling technologies are suitable for production, they fall short of the stringent requirements of analytical testing for sample preservation and high cleanliness. Therefore, there is an urgent need to develop a novel, low-destructive, pollution-free, and highly efficient sample preparation method that can remove surface oxide scale while completely preserving the original oxygen, nitrogen, and hydrogen content of the sample, providing a reliable pretreatment solution for high-precision gas analysis. Summary of the Invention

[0012] The purpose of this invention is to provide a rapid sample preparation method for stainless steel oxygen, nitrogen, and hydrogen detection samples. This method achieves rapid and non-destructive removal of oxide scale and contaminants from the sample surface, avoids hydrogen evolution side reactions and matrix dissolution, and obtains a clean sample with an intact matrix. This ensures that the subsequent oxygen, nitrogen, and hydrogen content detection results have high accuracy, reliability, and reproducibility.

[0013] To achieve the above objectives, the technical solution of the present invention is as follows: A rapid sample preparation method for detecting oxygen, nitrogen, and hydrogen in stainless steel samples includes the following steps: 1) Electrolytic removal of oxides Electrolysis was used to remove metal oxides from the surface of the stainless steel sample. The stainless steel sample was used as the anode, and the MMO titanium-based platinum coated electrode was used as the cathode. The electrolysis current density was 5~25 A / dm³. 2 The electrolysis temperature is 15~30℃, and the electrolysis time is 30~120s; The electrolyte used in the electrolysis process is a mixed aqueous solution of sulfuric acid and hydrogen peroxide, wherein the mass percentage of sulfuric acid in the electrolyte is 10-25% and the mass percentage of hydrogen peroxide is 3-10%. 2) Hydraulic shearing The stainless steel sample to be tested after step 1) is sheared to obtain a granular sample. 3) Stepped ultrasonic cleaning Particulate samples were cleaned using a two-stage ultrasonic process. First stage ultrasonic cleaning: The cleaning medium is anhydrous ethanol, and the ultrasonic cleaning time is 50~90s; The second stage of ultrasonic cleaning: the cleaning medium is acetone, and the ultrasonic cleaning time is 30~60s; 4) Drying After ultrasonic cleaning, the sample is placed in a clean environment with no oil, no dust, and a relative humidity of ≤30%, and dried with argon or helium gas with a purity of ≥99.99% to obtain stainless steel oxygen, nitrogen, and hydrogen test samples.

[0014] Preferably, the specific surface area of ​​the MMO titanium-based platinum coated electrode is 10~25m². 2 / g, of which the titanium-based purity is ≥99.5%.

[0015] Preferably, the distance between the anode and the cathode is 2~10cm, and more preferably 3~5cm.

[0016] Preferably, in step 2), a hydraulic shearing machine is used for shearing.

[0017] Preferably, the mass of the particulate sample is 0.5~1.2g.

[0018] Preferably, the stainless steel sample to be tested has a length of 30~100mm and a diameter or width of 1~8mm.

[0019] In the rapid sample preparation method described in this invention: This invention employs an electrolytic method to remove metal oxides from the surface of a stainless steel sample. The stainless steel sample is used as the anode, and an MMO titanium-based platinum-coated electrode is used as the cathode. The main reaction mechanism of the electrolysis process is as follows: Anodic region: Electrochemical and chemical dissolution of chromium and iron oxides on the stainless steel surface mainly occurs, with the reaction formula: Cr₂O₃ + 6H₂O + →2Cr 3+ +3H₂O, Fe₂O₃ + 6H₂O + →2Fe 3+ +3H₂O. Optimize electrolysis parameters and control the electrolysis current density to 5~25 A / dm³. 2 The electrolysis temperature is 15~30℃, the electrolysis time is 30~120s, and the dissolution reaction of the base metal (M→M) n+ +ne- (where M represents Fe, Cr, Ni, etc.) is suppressed to a minimum.

[0020] Cathode region: The core reaction is the preferential reduction reaction of hydrogen peroxide (H2O2): H2O2 + 2H+ + +2e-→2H2O, this reaction acts as a cathode depolarizer, effectively competing for and significantly inhibiting hydrogen ion (H+) ions. + The reduction and hydrogen evolution reaction (2H) + +2e→H2↑).

[0021] This invention employs a sulfuric acid-hydrogen peroxide composite electrolyte system during electrolysis. Sulfuric acid provides a strongly acidic environment and conductive ions to break down and dissolve the oxide film (Cr2O3, Fe2O3) on the sample surface. Hydrogen peroxide plays a crucial role in the system: as a cathode depolarizer, it preferentially undergoes a reduction reaction at the cathode (H2O2 + 2H+) before hydrogen ions. + The mechanism of +2e-→2H2O competitively and strongly inhibits the hydrogen evolution reaction (2H+2e-→2H2O). +The hydrogen peroxide (+2e→H2↑) reaction occurs. Its core value lies in two aspects: firstly, it effectively prevents the generation and infiltration of external hydrogen atoms into the sample during electrolysis; secondly, it avoids the escape of pre-existing hydrogen from the sample due to hydrogen evolution at the cathode. Therefore, the presence of hydrogen peroxide is crucial to ensuring that the hydrogen content detection results are not interfered with by the sample preparation process and accurately reflect the original sample state. Simultaneously, it also accelerates the overall removal efficiency of the oxide layer to a certain extent.

[0022] The mass percentage of hydrogen peroxide in the electrolyte is controlled between 3% and 10%, which helps to improve the stability of hydrogen element analysis. When no hydrogen peroxide is added or the hydrogen peroxide content is <3%, the RSD of hydrogen increases significantly. However, when the hydrogen peroxide content is >10%, the electrolysis reaction will be too fast, which can easily cause slight corrosion on the sample surface, change the original chemical composition of the sample, and affect the authenticity of the component analysis.

[0023] Sulfuric acid in the electrolyte provides the necessary acidity and conductive ions for electrolysis. Its mass percentage and current density together determine the driving force and selectivity of electrolysis. Insufficient sulfuric acid content or current density results in incomplete removal of the oxide layer, while excessive content can damage the substrate. Therefore, this invention, through research, controls the mass percentage of sulfuric acid in the electrolyte at 10%~25% and the current density at 5~25 A / dm³. 2 .

[0024] Electrolysis temperature mainly regulates reaction kinetics. This invention controls the electrolysis temperature at 15~30℃, which can provide sufficient kinetic energy to ensure the dissolution rate of oxides and improve electrolysis efficiency. It can also effectively suppress side reactions that may be caused by excessively high temperature (>30℃), such as rapid decomposition of hydrogen peroxide, evaporation of electrolyte, and aggravated corrosion of the substrate. This ensures that the electrolysis process is stable, uniform, and free from over-corrosion, thereby obtaining high-quality samples with consistent surface conditions.

[0025] This invention controls the sulfuric acid content in the electrolyte to 10%~25% and the hydrogen peroxide content to 3%~10%, combined with the control of electrolysis parameters (current density 5~25 A / dm³). 2 The electrolysis temperature is 15~30℃ and the electrolysis time is 30~120s. This ensures efficient removal of oxides while avoiding "over-corrosion" or intergranular corrosion of the stainless steel substrate. It can obtain high-quality samples with a matte silver surface, no oxide scale residue, and no corrosion pits in a short time, laying the foundation for accurate subsequent analysis.

[0026] The cathode uses an MMO titanium-based platinum-coated electrode. This cathode material combines a high-purity substrate with a high specific surface area platinum coating. The titanium-based purity is not less than 99.5 wt%, and its specific surface area is 10~25 m². 2 / g, this design brings the following beneficial effects: 1. High catalytic activity and excellent stability: The platinum coating on the surface has high catalytic activity and high hydrogen evolution overpotential, which can efficiently promote the occurrence of the main cathode reaction (H2O2 reduction) and strongly inhibit the hydrogen evolution side reaction; at the same time, it ensures that the electrode has excellent chemical stability in strongly acidic electrolyte, with no harmful substances leaching out and avoiding sample contamination.

[0027] 2. Strong mechanical properties and long service life: The high-strength titanium substrate provides solid support for the surface catalytic layer, giving the electrode good mechanical strength, dimensional stability and wear resistance, thus greatly extending its service life.

[0028] 3. Optimize reaction kinetics and suppress side reactions: specific surface area of ​​10~25m² 2 The design achieves a balance between the effective reaction area and mass transfer efficiency of the electrode. This design moderately reduces the actual current density on the cathode surface, effectively suppressing hydrogen evolution side reactions, while ensuring sufficient active sites and favorable mass transfer conditions to guarantee the efficient execution of the main reaction (H2O2 reduction). This fundamentally ensures the accuracy of hydrogen content analysis.

[0029] This invention addresses the complexity of contaminants, their occurrence states, and the ultimate requirement for ultra-high cleanliness in the preparation of oxygen, nitrogen, and hydrogen detection samples from stainless steel. The cleaning process employs a two-stage ultrasonic cleaning method: the first stage uses anhydrous ethanol for 50-90 seconds, followed by acetone for 30-60 seconds. The core of this method lies in utilizing the sequential action of solvents with different polarities, combined with the physical enhancement of ultrasonic cavitation, to construct a highly efficient, targeted, deep, and reproducible purification process. This is a crucial control point for ensuring the accuracy of the final analytical data, especially the hydrogen content data.

[0030] The stainless steel sample particles after electrolysis and hydraulic shearing exhibit multifaceted and complex surface contaminants, primarily including: inorganic ions remaining from the electrolyte (such as SO42-). 2- H + The contaminants include trace metal ions, trace amounts of lubricating grease or organic impurities that may be introduced during the shearing process, environmental moisture adsorbed by the sample itself, and suspended particles in the air, as well as gas molecules adsorbed on the fresh, active surface of the metal surface due to high-energy shearing. For complex contaminants, this invention employs an anhydrous ethanol-acetone stepped ultrasonic cleaning strategy: Phase 1: Anhydrous Ethanol Ultrasonic Cleaning. This phase utilizes the hydrophilicity of anhydrous ethanol and its excellent solubility for polar and ionic substances. The primary goal is to efficiently dissolve and remove trace amounts of water molecules, electrolyte residues, and water-soluble impurities adsorbed on the sample surface and fresh cut surfaces. The cavitation effect generated by ultrasound creates extremely high local instantaneous pressure and microjets near the sample surface, effectively destroying contaminants and achieving deep physical separation of residues and particles. The high volatility of ethanol also lays the foundation for rapid drying in subsequent steps.

[0031] The second stage: Acetone ultrasonic cleaning. This stage utilizes acetone's strong dissolving power for non-polar (weakly polar organic matter) such as greases, as well as its excellent dehydration and volatility, to achieve three core objectives: 1) to thoroughly dissolve and remove organic contaminants that were not removed in the first stage; 2) to act as a "displacement agent," completely removing trace amounts of ethanol and moisture remaining on the microscopic rough surfaces or crevices of the sample; and 3) its rapid evaporation characteristics create favorable conditions for subsequent argon drying. Similarly, the introduction of ultrasound ensures that acetone can rapidly penetrate all geometrically complex areas of the sample (such as burrs and micro-cracks), achieving thorough cleaning without any blind spots.

[0032] In this invention, the strict "ethanol first, acetone later" sequence ensures that the hydrophilic surface cleaned with ethanol is more conducive to the uniform spreading and penetration of the acetone solution. More importantly, acetone, as the final cleaning agent, constitutes the last line of defense against the introduction of exogenous hydrogen (H). Any residual ethanol or water may pyrolyze in the inert gas melting furnace of the analytical instrument, producing hydrogen gas and causing a difficult-to-correct positive deviation in the hydrogen content detection results. This invention, through the powerful "displacement" of acetone and thorough removal under ultrasonic assistance, maximizes the accuracy of the detection results.

[0033] After ultrasonic cleaning, the samples are dried in an oil-free, dust-free environment with a relative humidity of ≤30% using argon or helium gas with a purity of ≥99.99%. This is to prevent the samples from coming into contact with oxygen, nitrogen, and water vapor in the environment during the drying process, thus avoiding secondary contamination. In particular, it is crucial to prevent moisture adsorption from causing an increase in hydrogen background, which is a key step in ensuring the accuracy of oxygen, nitrogen, and hydrogen detection results.

[0034] This invention conducts the electrolysis, shearing, and ultrasonic cleaning processes at relatively low temperatures, avoiding the high temperatures generated on the sample surface during mechanical turning or grinding, and eliminating the physical introduction of external oxygen and nitrogen. Combined with subsequent stepped ultrasonic cleaning and high-purity inert gas drying, the process is carried out in an oil-free, dust-free, and low-dew-point clean environment, completely preventing the adsorption of O2, N2, and H2O from the air, ensuring the accuracy of the oxygen, nitrogen, and hydrogen content in the sample.

[0035] Furthermore, the electrolytically treated stainless steel samples are sheared using a hydraulic shearing machine to obtain granular samples with a mass of 0.5~1.2g. The upper limit of the granular sample mass (≤1.2g) is limited by the volume of the standard analytical crucible and the load-bearing capacity of the high-frequency induction furnace. If the sample is too heavy, it may lead to incomplete combustion or slag splashing, or even saturation of the detector signal. The lower limit of the granular sample mass (≥0.5g) is to control weighing error and ensure that the relative error introduced by weighing is reduced when weighing with a microbalance, thereby ensuring the accuracy and reproducibility of the final analytical results.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Highly accurate and reliable analytical results: This invention employs an electrolytic method to prepare stainless steel samples for oxygen, nitrogen, and hydrogen detection. Through a unique electrolyte system, leveraging the crucial depolarization effect of hydrogen peroxide at the cathode, combined with an MMO titanium-based platinum-coated cathode electrode, it efficiently strips the oxide layer (Cr2O3, Fe2O3) from the stainless steel sample surface while inhibiting hydrogen evolution. This fundamentally prevents interference with the original hydrogen content of the sample during preparation (preventing both penetration and escape), and avoids surface corrosion that could alter the original chemical composition and affect the accuracy of component analysis. The entire process involves no mechanical high-temperature or abrasive contact, eliminating the physical introduction of external oxygen and nitrogen. Subsequent stepped ultrasonic cleaning and high-purity inert gas drying are conducted in an oil-free, dust-free, low-dew-point clean environment, thoroughly removing contaminants from the sample surface while preventing secondary adsorption of O2, N2, and H2O from the air. Therefore, the method of the present invention ensures that the prepared sample can truly reflect the original content of oxygen, nitrogen and hydrogen in the stainless steel matrix, the analytical spectrum baseline is stable and there is no tailing phenomenon, the results are highly accurate and reproducible, and ensures that the RSD of oxygen and nitrogen is ≤5% and the RSD of hydrogen is ≤8.5% in the detection results.

[0037] 2. Significantly Improved Sample Preparation Efficiency and Throughput: The entire sample preparation process described in this invention can be completed within 3-5 minutes, and multiple samples can be processed at once. In contrast, traditional mechanical turning or grinding methods can only prepare one sample at a time, and the preparation time for a single sample is 6-12 minutes. The sample preparation efficiency of this invention is far higher than that of traditional mechanical sample preparation methods, perfectly meeting the urgent need for rapid analysis before the furnace in the steel smelting process.

[0038] 3. Good consistency and reproducibility of results: Based on electrochemical principles, the process parameters (current, time, temperature, etc.) can be precisely quantified and controlled, eliminating the uncertainty of human operation and ensuring a high degree of consistency and reliability between the surface state and analytical data of different batches of samples. Attached Figure Description

[0039] Figure 1 Images of electrolytic samples of different grades of stainless steel; Figure 2 Comparison of oxygen analysis spectra of 304 austenitic stainless steel prepared using different sample preparation methods; Figure 3 Comparison of oxygen analysis spectra of 410 ferritic stainless steel prepared by different sample preparation methods. Detailed Implementation

[0040] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0041] 1. Experimental Samples and Apparatus Examples 1-17 and Comparative Examples 1-4 used 20Cr13 stainless steel samples (Φ6mm×90mm) as anodes, with oxygen, nitrogen and hydrogen contents identified as 0.0022wt%, 0.0170wt% and 0.00023wt%, respectively.

[0042] Examples 18 and Comparative Examples 11-12 used 316L austenitic stainless steel samples (Φ5.5mm×100mm); the oxygen, nitrogen and hydrogen contents were identified as 0.0027wt%, 0.057wt%, and 0.00053wt%, respectively.

[0043] Example 19 used a 430 ferritic stainless steel sample (Φ6mm×30mm), with oxygen, nitrogen and hydrogen contents of 0.0017wt%, 0.036wt% and 0.00013wt%, respectively.

[0044] Examples 20 and Comparative Examples 5-10 used 304 stainless steel standard samples (Φ6mm×30mm), with oxygen, nitrogen and hydrogen contents identified as 0.0030wt%, 0.036wt%, and 0.00055wt%, respectively.

[0045] In the examples and comparative examples, the cathodes used were MMO titanium-based platinum-coated electrodes, and the anodes and cathodes were placed in a 500 mL beaker for electrolysis.

[0046] 2. Sample surface evaluation method: The surface condition of the samples was evaluated and graded using a combination of visual (macro) and optical microscopy (micro) methods, based on the standards established in Table 2.

[0047]

[0048] Analytical accuracy evaluation: Three samples were prepared in parallel for each set of parameters, and the oxygen, nitrogen and hydrogen contents were determined. The average relative standard deviation (RSD) of the determination results of each element was used to evaluate the process stability.

[0049] The process parameters for the embodiments and comparative examples of this invention are shown in Tables 3 and 4. The oxygen, nitrogen, and hydrogen contents measured in stainless steel samples for the embodiments and comparative examples of this invention are shown in Table 5.

[0050] Figure 1 The figures show the typical morphology of different grades of samples after electrolysis in the embodiments of the present invention. As can be seen from the figures, after electrolysis of different grades of samples according to the method described in the present invention, the oxide layer on the sample surface is completely peeled off, revealing a uniform metallic color.

[0051] Electrolysis current density is 5~25 A / dm 2 The electrolysis temperature is 15~30℃, and the electrolysis time is 30~120s; The electrolyte is a mixed aqueous solution of sulfuric acid and hydrogen peroxide, wherein the mass percentage of sulfuric acid in the electrolyte is 10-25% and the mass percentage of hydrogen peroxide is 3-10%.

[0052] In Comparative Example 1, the electrolysis current density was low, the electrolysis time was too long, and the surface of the sample after electrolysis was unqualified, failing to meet the requirements for oxygen, nitrogen, and hydrogen element analysis.

[0053] In Comparative Example 2, the electrolysis current density was too high and the electrolysis time was too short, resulting in an unqualified sample surface after electrolysis, which could not meet the requirements for oxygen, nitrogen, and hydrogen element analysis.

[0054] In Comparative Example 3, the electrolysis time was too long and the sulfuric acid content in the electrolyte was too low, resulting in unqualified sample surfaces after electrolysis, which could not meet the requirements for oxygen, nitrogen, and hydrogen element analysis.

[0055] In Comparative Example 4, the electrolysis time was too short, the sulfuric acid content in the electrolyte was too high, and the sample surface was unqualified after electrolysis, failing to meet the requirements for oxygen, nitrogen, and hydrogen element analysis.

[0056] In Comparative Example 5, the electrolysis parameters met the requirements of this invention, and the sample surface was excellent after electrolysis. However, no cleaning was performed after electrolysis, and the RSD values ​​of the oxygen, nitrogen, and hydrogen content were high when the samples were directly tested.

[0057] In Comparative Example 6, the electrolysis parameters met the requirements of this invention, and the sample surface was excellent after electrolysis. However, during the cleaning process, only anhydrous ethanol was used for immersion cleaning, resulting in a high RSD value for the final measured oxygen, nitrogen, and hydrogen content.

[0058] In Comparative Example 7, the electrolysis parameters met the requirements of this invention, the sample surface was excellent after electrolysis, and the sample was ultrasonically cleaned with anhydrous ethanol alone for 90 seconds after electrolysis. The RSD values ​​of the oxygen, nitrogen and hydrogen content measured at the end were relatively high.

[0059] In Comparative Example 8, the electrolysis parameters met the requirements of this invention, the sample surface was excellent after electrolysis, and the sample was cleaned by immersion in acetone as a single medium after electrolysis. The RSD values ​​of the oxygen, nitrogen and hydrogen content measured at the end were relatively high.

[0060] In Comparative Example 9, the electrolysis parameters met the requirements of this invention, the sample surface was excellent after electrolysis, and the sample was ultrasonically cleaned with only acetone for 45 seconds after electrolysis. The RSD values ​​of the oxygen, nitrogen and hydrogen content measured at the end were relatively high.

[0061] In Comparative Example 10, the electrolysis parameters met the requirements of this invention, the sample surface was excellent after electrolysis, and the sample was cleaned by soaking in anhydrous ethanol and acetone after electrolysis. The RSD values ​​of the oxygen, nitrogen and hydrogen content were high in the final measurement.

[0062] In the embodiments of the present invention, the RSD of oxygen and nitrogen in the sample measurements is ≤5%, and the RSD of hydrogen is ≤8.5%. The low RSD values ​​indicate that the samples prepared by the method of the present invention have good consistency and surface cleanliness, which can meet the requirements for accurate determination of oxygen, nitrogen and hydrogen in stainless steel, and verify the efficiency and reliability of the method.

[0063] The results of the embodiments and comparative examples of the present invention fully demonstrate that the synergistic effect of the combined process of "electrolytic removal of oxide layer + stepped ultrasonic cleaning" adopted in the present invention is the key to obtaining a clean and consistent sample surface and ensuring high accuracy and high stability of oxygen, nitrogen and hydrogen analysis.

[0064] Comparative Example 11: Samples were prepared using the traditional mechanical turning method, using the same 316L austenitic stainless steel as in Example 1 of this invention. The test results are shown in Table 4.

[0065] Comparative Example 12: Samples were prepared using the traditional mechanical grinding method, using the same 316L austenitic stainless steel as in Example 1 of this invention. The test results are shown in Table 4.

[0066] Compared with Comparative Examples 11 and 12, the traditional turning method is easily affected by tool wear and cooling medium contamination, resulting in poor long-term stability between batches. It is also poorly applicable to irregularly shaped samples and thin-walled, easily deformable samples, and the sample preparation time for a single sample usually exceeds 10 minutes. The mechanical grinding method easily introduces a surface deformation layer and secondary oxidation, leading to higher oxygen measurement results and increased RSD fluctuations.

[0067] More importantly, this method achieves high-throughput batch sample preparation for the first time. While ensuring data stability (oxygen and nitrogen RSD ≤ 5%, hydrogen RSD ≤ 8.5%), the efficiency is increased to more than 3 times that of turning and mechanical grinding methods. It is particularly suitable for high-time-sensitivity scenarios such as furnace pre-analysis and rapid multi-batch testing, and has significant advantages in industrial applications.

[0068] Figure 2 Comparison of oxygen analysis spectra of samples prepared from 304 austenitic stainless steel using the method, turning method, and grinding method described in this invention. Figure 3 Comparison of oxygen analysis spectra of samples prepared from 410 ferritic stainless steel using the method described in this invention, the turning method, and the grinding method. Figure 2 , Figure 3 The comparison of the spectra provides a more intuitive view that the oxygen analysis spectrum of samples prepared by the traditional mechanical grinding method has obvious abnormal peaks (tailing), reflecting the negative impact of surface contamination on the analysis results.

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Claims

1. A rapid sample preparation method for detecting oxygen, nitrogen, and hydrogen in stainless steel samples, characterized in that, Includes the following steps: 1) Electrolytic removal of oxides Electrolysis was used to remove metal oxides from the surface of the stainless steel sample. The stainless steel sample was used as the anode, and the MMO titanium-based platinum coated electrode was used as the cathode. The electrolysis current density was 5~25 A / dm³. 2 The electrolysis temperature is 15~30℃, and the electrolysis time is 30~120s; The electrolyte used in the electrolysis process is a mixed aqueous solution of sulfuric acid and hydrogen peroxide, wherein the mass percentage of sulfuric acid is 10-25% and the mass percentage of hydrogen peroxide is 3-10%. The specific surface area of ​​the MMO titanium-based platinum coated electrode is 10~25m². 2 / g, of which the titanium-based purity is ≥99.5%; 2) Hydraulic shearing The stainless steel sample to be tested after step 1) is sheared to obtain a granular sample. 3) Stepped ultrasonic cleaning Particulate samples were cleaned using a two-stage ultrasonic process. First stage ultrasonic cleaning: The cleaning medium is anhydrous ethanol, and the ultrasonic cleaning time is 50~90s; The second stage of ultrasonic cleaning: the cleaning medium is acetone, and the ultrasonic cleaning time is 30~60s; 4) Drying After ultrasonic cleaning, the sample is placed in a clean environment with no oil, no dust, and a relative humidity of ≤30%, and dried with argon or helium gas with a purity of ≥99.99% to obtain stainless steel oxygen, nitrogen, and hydrogen test samples.

2. The rapid sample preparation method for detecting oxygen, nitrogen, and hydrogen in stainless steel as described in claim 1, characterized in that, In step 1), the distance between the anode and the cathode is 2~10cm.

3. The rapid sample preparation method for detecting oxygen, nitrogen, and hydrogen in stainless steel as described in claim 1, characterized in that, In step 1), the distance between the anode and the cathode is 3~5cm.

4. The rapid sample preparation method for detecting oxygen, nitrogen, and hydrogen in stainless steel as described in claim 1, characterized in that, In step 2), a hydraulic shearing machine is used for shearing.

5. The rapid sample preparation method for stainless steel oxygen, nitrogen, and hydrogen detection samples as described in claim 1 or 4, characterized in that, In step 2), the mass of the particulate sample is 0.5~1.2g.

6. The rapid sample preparation method for detecting oxygen, nitrogen, and hydrogen in stainless steel as described in claim 1, characterized in that, The stainless steel sample to be tested has a length of 30~100mm and a diameter or width of 1~8mm.

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