Method for determining trace impurity elements in iron-chromium-molybdenum-niobium alloy

Abstract

This invention provides an analytical method for determining trace impurity elements in iron-chromium-molybdenum-niobium alloys, belonging to the technical field of alloy impurity analysis and detection. The method includes several steps: sample pretreatment, sample dissolution, microwave digestion, standard solution preparation, and determination of impurity elements in the iron-chromium-molybdenum-niobium alloy. By optimizing the reagent ratio and dosage, and combining advanced microwave digestion and inductively coupled plasma mass spectrometry (ICP-MS), the invention overcomes the problems of complex sample pretreatment and long digestion time in existing technologies, shortens the sample digestion time, reduces environmental pollution, and meets the requirements of ICP-MS for determining impurity elements in iron-chromium-molybdenum-niobium alloys. It is simple, efficient, and fully dissolves the iron-chromium-molybdenum-niobium alloy.

Description

Technical Field

[0001] This invention relates to the field of alloy impurity analysis and detection technology, specifically to an analytical method for determining trace impurity elements in iron-chromium-molybdenum-niobium alloys. Background Technology

[0002] Iron-chromium-molybdenum-niobium alloys, as a class of high-performance high-temperature structural materials, possess excellent high-temperature mechanical strength, high-temperature oxidation resistance, corrosion resistance, and creep resistance. They have become core materials in high-end and critical fields such as hot-end components of aerospace engines, structural materials for nuclear reactors, corrosion-resistant equipment in chemical industries, and gas turbine blades. With the continuous improvement of the requirements for material service performance and reliability in high-end equipment manufacturing, the metallurgical purity and impurity element control level of iron-chromium-molybdenum-niobium alloys have become key indicators restricting their performance standards and engineering applications.

[0003] Throughout the entire process of alloy preparation, processing, and service, trace and minor impurity elements can significantly degrade the mechanical properties, corrosion resistance, high-temperature structural stability, and service life of materials, directly affecting the operational safety and service life of critical components. Therefore, accurate and quantitative determination of trace impurity elements in iron-chromium-molybdenum-niobium alloys is a core technical prerequisite for scientifically assessing alloy purity, characterizing material properties, and ensuring product quality and service reliability. It has irreplaceable engineering and scientific significance for achieving material quality control, process optimization, and performance improvement.

[0004] Currently, commonly used methods for metal element detection include atomic absorption spectrometry (AAS) and inductively coupled plasma optical emission spectrometry (ICP-OES). However, these methods still have certain limitations when dealing with complex matrices and determining trace elements. For example, atomic absorption spectrometry is a single-element analysis method and cannot simultaneously determine multiple component impurities, resulting in low efficiency for batch analysis of multiple trace impurities in iron-chromium-molybdenum-niobium alloys. While inductively coupled plasma optical emission spectrometry has the advantage of simultaneous multi-element determination, when dealing with high-matrix alloy samples such as iron-chromium-molybdenum-niobium alloys, its sensitivity and detection capability for trace impurities are difficult to meet the requirements for ultra-trace detection due to matrix background and spectral interference. Therefore, developing an ICP-MS analysis method that can effectively eliminate matrix interference and achieve rapid and accurate multi-element determination, especially considering the high matrix characteristics of iron-chromium-molybdenum-niobium alloys, has become a current research focus in the field of trace impurity detection. Summary of the Invention

[0005] Therefore, it is necessary to establish a rapid, efficient, and highly accurate analytical method for determining trace impurity elements in iron-chromium-molybdenum-niobium alloys. This method should be highly safe, completely digested, eliminate matrix interference, and achieve highly sensitive and accurate detection of impurity elements in iron-chromium-molybdenum-niobium alloys.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] An analytical method for determining trace impurity elements in iron-chromium-molybdenum-niobium alloys includes the following steps:

[0008] Sample preparation: The iron-chromium-molybdenum-niobium alloy sample was prepared into fine particles, and 0.1000g of the sample was accurately weighed into a digestion vessel;

[0009] Sample dissolution: Add 1-2 mL of ultrapure water to the microwave digestion vessel containing the sample for wetting, and then add 9 mL of a mixed acid solution of hydrochloric acid, nitric acid and hydrofluoric acid for digestion. The volume ratio of nitric acid: hydrochloric acid: hydrofluoric acid in the mixed acid solution is 3-5:3-5:2-3 to ensure that the mixed acid solution is in full contact with the sample.

[0010] Microwave digestion: Using microwave digestion, the sample is completely digested by undergoing the following four stages followed by natural cooling. The first stage involves raising the temperature to 120-130℃ and holding for 5-7 minutes; the second stage involves raising the temperature to 150-160℃ and holding for 5-7 minutes; the third stage involves raising the temperature to 200℃ and holding for 10-15 minutes; and the fourth stage involves raising the temperature to 220℃ and holding for 30-35 minutes.

[0011] Preparation of standard solutions:

[0012] A. Mixed standard solutions: Prepare mixed standard solutions of aluminum, cobalt, nickel, vanadium, tungsten, copper, and manganese;

[0013] B. Matrix solution preparation: According to the matrix element composition ratio of the sample, weigh out high-purity metallic iron, chromium, molybdenum and niobium reference materials respectively, add them to the mixed acid system for dissolution, and prepare a matrix solution that matches the matrix composition of the sample.

[0014] C. Preparation of a series of standard solutions: Pipette 10 mL of the matrix solution and the mixed standard solution into seven 100 mL volumetric flasks, and then add a certain amount of 10.0 μg / mL mixed standard solution to each of the seven flasks to prepare a series of standard solutions with concentrations of 0 ng / mL, 1.0 ng / mL, 2.0 ng / mL, 5.0 ng / mL, 10.0 ng / mL, 20.0 ng / mL, and 50.0 ng / mL.

[0015] D. Preparation of mixed internal standard solution: Select... 45 Sc、 103 Rh、 187 Re was used as an internal standard element to prepare a mixed internal standard solution;

[0016] Trace impurity element determination: The working parameters of the inductively coupled plasma mass spectrometer were optimized. When determining trace impurity elements in the sample solution, the measuring device was connected by a three-way connector to connect the sample injection pipeline and the mixed internal standard solution pipeline, so as to realize the online addition and synchronous determination of the internal standard element. The sample solution was introduced into ICP-MS to measure the signal intensity of each impurity element. The mixed internal standard solution was introduced online and synchronously to correct for signal drift and matrix effect. The content of each impurity element in the sample was quantitatively calculated based on the standard series working curves.

[0017] The elemental content in the iron-chromium-molybdenum-niobium alloy sample is calculated according to formula (1):

[0018] (1)

[0019] In formula (1): ρ is the mass concentration of the element to be tested in the analytical solution, in ng / mL; ρ0 is the mass concentration of the element to be tested in the blank solution, in ng / mL; V is the total volume of the test solution, in mL; and m is the mass of the sample, in g.

[0020] E. Preparation of reagent blank solution: Prepare a reagent blank solution without the test sample by using the same digestion steps and reagents as the test sample.

[0021] Preferably, the sample processing step specifically involves processing the iron-chromium-molybdenum-niobium alloy sample to a particle size ≤0.125mm or ≤120 mesh, and accurately weighing 0.1000g±0.0001g of the sample into a digestion vessel.

[0022] Preferably, in the sample dissolution step: hydrochloric acid, nitric acid and hydrofluoric acid are added sequentially to digest the sample, and the mixture is gently shaken to ensure full contact between the mixed acid and the sample, and then allowed to stand for a pre-reaction of 10-15 minutes.

[0023] Preferably, the digestion vessel is a polytetrafluoroethylene digestion vessel; the nitric acid concentration is between 65-68% and the purity level is high; the concentrated hydrochloric acid concentration is between 36-38% and the purity level is high; and the hydrofluoric acid concentration is ≥40% and the purity level is high.

[0024] Preferably, in the microwave digestion step, the microwave power is 400-600W in the first stage, 600-800W in the second stage, 800-1000W in the third stage, and 1000-1100W in the fourth stage.

[0025] Preferably, the microwave digestion step further includes, after digestion, allowing it to cool naturally, then adding 2 mL of nitric acid, transferring it to a 100 mL volumetric flask, making up to the mark with ultrapure water, and shaking well for later use.

[0026] Preferably, in the standard solution preparation step, the mixed standard solution is prepared by transferring 1 mL of 1000 μg / mL aluminum, cobalt, nickel, vanadium, tungsten, copper, and manganese standard storage solutions into 100 mL plastic volumetric flasks and diluting them to the mark with ultrapure water, resulting in a solution with a concentration of 10.0 μg / mL. The matrix solution is prepared by weighing 0.9990–1.0000 g of high-purity metallic iron, chromium, molybdenum, and niobium reference materials with the same elemental composition as the sample into a 100 mL polytetrafluoroethylene beaker, adding 1–2 mL of ultrapure water for wetting, and then sequentially adding 9 mL of a mixed acid solution of hydrochloric acid, nitric acid, and hydrofluoric acid for digestion. The volume ratio of nitric acid:hydrochloric acid:hydrofluoric acid in the mixed acid solution is 3–5:3–5:2–3, ensuring sufficient contact between the mixed acid solution and the sample. The mixture is allowed to stand at room temperature for 10–15 min for pre-reaction, and then placed in a 60–80 °C constant temperature water bath for further processing. A constant temperature water bath is best. The solution is taken until it is clear and transparent with no metal powder residue. It is then removed and cooled. After cooling, it is transferred to a 100mL volumetric flask, 10mL of nitric acid is added, and it is diluted to the mark with ultrapure water. The solution is then made up to volume and shaken well before use.

[0027] Preferably, in the standard solution preparation step, the preparation of the mixed internal standard solution specifically involves transferring a certain amount of 1.0 μg / mL... 45 Sc、 103 Rh、 187 Prepare a mixed internal standard solution of 8 ng / mL by storing Re standard stock solution in a 100 mL plastic volumetric flask.

[0028] Preferably, in the trace impurity element determination step, an inductively coupled plasma mass spectrometer with a mass resolution of no more than 0.8 amu is selected. The mass spectrometer is optimized using a mixed tuning solution, tuned to a double charge yield of less than 2.5% and an oxide yield of less than 2.5%, and specifically tuned for this alloy matrix to ensure that FeO⁺ / Fe⁺ and NbO⁺ / Nb⁺ are both less than 1.0%. Helium is introduced as the reaction gas, with a helium flow rate of 4.5 mL / min. Operating parameters are: RF power 1500 W, plasma gas flow rate 14.0 L / min, auxiliary gas flow rate 0.8 L / min, nebulizer flow rate 0.92 L / min, nebulizer temperature 2.5 °C, sampling depth 5.00 mm, sample flushing time 30 s, scanning mode peak skipping, integration residence time 80 ms, single element integration time 6 s, and isotope detection... 27 Al、 5 ¹V、 55 Mn, 59 Co、 60 Ni、 63 Cu、 184 W, during the measurement process, select 45 Sc、 103 Rh、 187Re is used as an internal index element.

[0029] Preferably, in the step of determining trace impurity elements, optimizing the operating parameters of the inductively coupled plasma mass spectrometer specifically involves continuously measuring the signal intensity of the trace impurity element to be measured in the blank solution, and calculating the detection limit of the trace impurity element to be measured by statistical calculation method to be less than 0.028 ng / mL and the quantification limit to be less than 0.077 ng / mL; performing multiple parallel repeated determinations on the test sample and the spiked recovery sample, with the relative standard deviation of the calculation method being less than 5.63% and the spiked recovery rate being between 95.0% and 105.5%.

[0030] This invention provides an analytical method for determining trace impurity elements in iron-chromium-molybdenum-niobium alloys, which has the following advantages: 1. Microwave digestion is performed using a mixed acid of high-purity HNO3, HCl, and HF, and a perchloric acid-free mixed acid system is designed to avoid the safety risks of perchloric acid and Cl. - Interference was eliminated, improving the safety of experimental operations; on the other hand, by optimizing the ratio of the digestion solution and the heating digestion time and temperature parameters of the microwave digestion program, the stable lattice structure of the iron-chromium-molybdenum-niobium alloy was effectively destroyed, significantly improving the digestion efficiency and effect of solid samples, achieving complete digestion of samples, and the dissolution recovery rate reached over 95%; 2. Standard solutions of aluminum, cobalt, nickel, vanadium, tungsten, copper, and manganese were prepared by matrix matching method, so that the matrix composition of the standard solutions and the sample solutions were consistent, effectively eliminating matrix interference of Fe, Cr, Mo, and Nb. The results were obtained by inductively coupled plasma mass spectrometry, overcoming the problem of insufficient sensitivity and detection ability of trace elements in the existing technology, and improving the accuracy and stability of detection; 3. This invention selects 45 Sc、 103 Rh、 187 Using Re as an internal standard, and by controlling plasma power and sampling depth, the collision reaction cell technology effectively eliminates multi-element interference, enabling the simultaneous detection of multiple impurity elements in iron-chromium-molybdenum-niobium alloys, ensuring detection efficiency, accuracy, and reliability. 4. This invention achieves simultaneous multi-element determination of impurity elements in iron-chromium-molybdenum-niobium alloys, offering advantages such as speed, energy saving, and high sensitivity, significantly improving analytical efficiency and detection accuracy. 5. By optimizing reagent ratios and usage, and combining advanced microwave digestion and inductively coupled plasma mass spectrometry (ICP-MS), this invention overcomes the problems of complex sample pretreatment and long digestion times in existing technologies, shortening sample digestion time and reducing environmental pollution. Detailed Implementation

[0031] An analytical method for determining trace impurity elements in iron-chromium-molybdenum-niobium alloys includes the following steps:

[0032] Step 1, Sample preparation:

[0033] Cut and grind the iron-chromium-molybdenum-niobium alloy sample to a particle size ≤0.125mm or ≤120 mesh, and accurately weigh 0.1000g±0.0001g of the sample into a polytetrafluoroethylene digestion vessel.

[0034] Step 2, sample dissolution:

[0035] Add 1-2 mL of ultrapure water to the microwave digestion vessel containing the sample for wetting, then add 9 mL of a mixed acid solution consisting of hydrochloric acid, nitric acid, and hydrofluoric acid in sequence for digestion. The volume ratio of nitric acid:hydrochloric acid:hydrofluoric acid in the mixed acid solution is 3-5:3-5:2-3, ensuring sufficient contact between the mixed acid solution and the sample. Allow the mixture to stand for a pre-reaction period of 10-15 min. The nitric acid concentration is between 65-68% and the purity level is high; the concentrated hydrochloric acid concentration is between 36-38% and the purity level is high; and the hydrofluoric acid concentration is ≥40% and the purity level is high.

[0036] Specifically, add 1 mL of ultrapure water to the microwave digestion vessel containing the sample for wetting, then add 4 mL of hydrochloric acid, 3 mL of nitric acid, and 2 mL of hydrofluoric acid in sequence, for a total of 9 mL of mixed acid solution for digestion. The volume ratio of nitric acid: hydrochloric acid: hydrofluoric acid in the mixed acid solution is 4:3:2. Gently shake to ensure that the mixed acid and the sample are in full contact, and allow to stand for a pre-reaction time of 12 min.

[0037] Alternatively, add 2 mL of ultrapure water to the microwave digestion vessel containing the sample to wet it, then add 3 mL of hydrochloric acid, 3 mL of nitric acid, and 3 mL of hydrofluoric acid in sequence for digestion, for a total of 9 mL of mixed acid solution. The volume ratio of nitric acid:hydrochloric acid:hydrofluoric acid in the mixed acid solution is 1:1:1. Shake gently to ensure that the mixed acid and the sample are in full contact, and allow it to stand for a pre-reaction for 10 min.

[0038] Alternatively, add 2 mL of ultrapure water to the microwave digestion vessel containing the sample to wet it, then add 5 mL of hydrochloric acid, 2 mL of nitric acid, and 2 mL of hydrofluoric acid in sequence for digestion, for a total of 9 mL of mixed acid solution. The volume ratio of nitric acid:hydrochloric acid:hydrofluoric acid in the mixed acid solution is 5:2:2. Shake gently to ensure that the mixed acid and the sample are in full contact, and allow it to stand for a pre-reaction for 15 min.

[0039] Alternatively, add 1.5 mL of ultrapure water to the microwave digestion vessel containing the sample to wet it, then add 2 mL of hydrochloric acid, 5 mL of nitric acid, and 2 mL of hydrofluoric acid in sequence for digestion, for a total of 9 mL of mixed acid solution. The volume ratio of nitric acid:hydrochloric acid:hydrofluoric acid in the mixed acid solution is 2:5:2. Gently shake to ensure full contact between the mixed acid and the sample, and allow it to stand for a pre-reaction for 13 min.

[0040] Alternatively, add 1 mL of ultrapure water to the microwave digestion vessel containing the sample to wet it, then add 3 mL of hydrochloric acid, 4 mL of nitric acid, and 2 mL of hydrofluoric acid in sequence for digestion, for a total of 9 mL of mixed acid solution. The volume ratio of nitric acid:hydrochloric acid:hydrofluoric acid in the mixed acid solution is 3:4:2. Shake gently to ensure that the mixed acid and the sample are in full contact, and allow it to stand for a pre-reaction for 14 min.

[0041] The use of a ternary mixed acid system of hydrochloric acid, nitric acid, and hydrofluoric acid avoids the safety risks associated with perchloric acid and interference from Cl⁻, thus improving the safety of experimental procedures. The order of addition is also crucial: HCl preferentially destroys the oxide film, HNO₃ provides oxidizing properties, and HF complexes Nb and Mo. If the order were changed to nitric acid, hydrochloric acid, and hydrofluoric acid, the alloy surface would rapidly passivate, forming a dense oxide film, leading to incomplete dissolution. This ratio has also been verified through multiple experiments, ensuring efficient and complete sample dissolution, while the water ratio prevents acid splashing during the temperature rise in the reaction process.

[0042] Step 3, microwave digestion:

[0043] The temperature and holding time ranges for the microwave digestion stage are shown in Table 1. These heating conditions ensure complete digestion of the alloy, guaranteeing digestion efficiency and effectiveness. After digestion, allow it to cool naturally, then add 2 mL of nitric acid, transfer to a 100 mL volumetric flask, and dilute to the mark with ultrapure water. Shake well and set aside.

[0044] Finally, 2 mL of nitric acid is added to ensure the acidity of the solution, prevent the hydrolysis and precipitation of the analyte, and stabilize the valence state of the analyte ions to ensure accurate and reliable measurement results.

[0045] Table 1 Microwave Digestion Program Parameters:

[0046]

[0047] Specifically, in the first stage, the temperature is raised to 120℃ and held for 7 minutes, with a microwave power of 400W; in the second stage, the temperature is raised to 150℃ and held for 7 minutes, with a microwave power of 600W; in the third stage, the temperature is raised to 200℃ and held for 15 minutes, with a microwave power of 800W; and in the fourth stage, the temperature is raised to 220℃ and held for 35 minutes, with a microwave power of 1000W.

[0048] Alternatively, the process could be as follows: First stage: raise the temperature to 130℃ and hold for 5 minutes, with a microwave power of 600W; Second stage: raise the temperature to 160℃ and hold for 5 minutes, with a microwave power of 600W; Third stage: raise the temperature to 200℃ and hold for 10 minutes, with a microwave power of 1000W; Fourth stage: raise the temperature to 220℃ and hold for 30 minutes, with a microwave power of 1100W.

[0049] Optimally, in the first stage, the temperature is raised to 120℃ and held for 5 minutes, with a microwave power of 400W; in the second stage, the temperature is raised to 150℃ and held for 5 minutes, with a microwave power of 600W; in the third stage, the temperature is raised to 200℃ and held for 10 minutes, with a microwave power of 800W; and in the fourth stage, the temperature is raised to 220℃ and held for 30 minutes, with a microwave power of 1100W.

[0050] To address the challenge of the stable chemical properties and dense crystal structure of iron-chromium-molybdenum-niobium alloys, which are difficult to destroy with conventional acids, this invention employs an optimized high-concentration mixed acid system with a four-stage gradient heating process and long-term high-temperature digestion at 220°C. To address the difficulty of dissolving tungsten in the alloy due to its high melting point and tendency to form stable carbides, this invention utilizes a high-temperature oxidizing environment. HNO3 oxidizes W to WO3, while HF dissolves the generated WO3. To address the challenge of niobium and titanium easily hydrolyzing to form insoluble hydroxides, this invention maintains an acidic environment, allowing F⁻ and Nb⁻ to react. 5 ⁺And Ti 4+ It forms a stable fluorine complex and no longer hydrolyzes and precipitates.

[0051] Step 4, Preparation of standard solution:

[0052] A. Mixed standard solution: Prepare a mixed standard solution of aluminum, cobalt, nickel, vanadium, tungsten, copper and manganese. Transfer 1 mL of the 1000 μg / mL aluminum, cobalt, nickel, vanadium, tungsten, copper and manganese standard stock solution into a 100 mL plastic volumetric flask and dilute with water to the mark. This solution is 10.0 μg / mL.

[0053] B. Matrix Solution Preparation: Based on the matrix elemental composition ratio of the sample, weigh 0.9990–1.0000 g of high-purity metallic iron, chromium, molybdenum, and niobium reference materials with the same matrix elemental composition ratio as the sample into a 100 mL polytetrafluoroethylene beaker. Specifically, for the iron-chromium-molybdenum-niobium alloy tested in this invention, the mass ratio of iron:chromium:molybdenum:niobium in the iron-chromium-molybdenum-niobium alloy is 20:18:3:5. Weigh 0.9990–1.0000 g of high-purity metal powder, wherein the mass ratio of iron powder:chromium powder:molybdenum powder:niobium powder is 20:18:3:5. Specifically, weigh 1.0000 g of high-purity metal powder, wherein the mass ratio of iron powder:chromium powder:molybdenum powder:niobium powder is 20:18:3:5, that is, iron powder: 0.4348 g, chromium powder: 0.3913 g, molybdenum powder: 0.0652 g, niobium powder: 0.1087 g. Add g to a 100ml polytetrafluoroethylene beaker, then add 1-2mL of ultrapure water to wet the sample. Next, add 9mL of a mixed acid solution of hydrochloric acid, nitric acid, and hydrofluoric acid in sequence for digestion. The volume ratio of nitric acid:hydrochloric acid:hydrofluoric acid in the mixed acid solution is 3-5:3-5:2-3. Ensure that the mixed acid solution is in full contact with the sample. The amount of mixed acid solution used in this step corresponds to the amount used in the sample dissolution in step two. Allow the mixed acid solution to be in full contact with the sample and let it stand at room temperature for 10-15 minutes for pre-reaction. Then place it in a 60-80℃ constant temperature water bath until the solution is clear and transparent with no metal powder residue. Remove and cool. After cooling, transfer it to a 100mL volumetric flask, add 10mL of nitric acid, dilute to the mark with ultrapure water, and make up to volume. Shake well and set aside for later use.

[0054] The optimal temperature for digestion is a constant-temperature water bath of 60-80℃, with 70℃ being the most suitable. A water bath temperature of 60-80℃ ensures complete dissolution of the metal powder without causing loss or contamination due to violent reactions. Below 60℃, high-purity iron-chromium-molybdenum-niobium metal powders are difficult to dissolve completely, easily producing undissolved residues and subsequent hydrolysis precipitation, leading to a mismatch between the sample matrix and the standard curve matrix, and reducing the precision and accuracy of the determination. Temperatures above 80℃ are prone to hydrolysis turbidity or trace volatilization, directly affecting the linearity and accuracy of the curve.

[0055] C. Preparation of a series of standard solutions: Transfer the matrix solution and the mixed standard solution separately and dilute them to prepare a series of standard solutions. Specifically, transfer 10 mL of the matrix solution into 7 aliquots and place them into 7 100 mL plastic volumetric flasks. Then, add a certain amount of 10.0 μg / mL mixed standard solution to each of the 7 volumetric flasks to prepare a series of standard solutions with concentrations of 0 ng / mL, 1.0 ng / mL, 2.0 ng / mL, 5.0 ng / mL, 10.0 ng / mL, 20.0 ng / mL, and 50.0 ng / mL.

[0056] D. Preparation of mixed internal standard solution: Select... 45 Sc、 103 Rh、187 Re was used as an internal standard element to prepare a mixed internal standard solution; specifically, a certain amount of 1.0 μg / mL was transferred to each solution. 45 Sc、 103 Rh、 187 Prepare a mixed internal standard solution of 8 ng / mL by storing Re standard stock solution in a 100 mL plastic volumetric flask.

[0057] Conventional methods often employ simple matrices or general standard curves, which are difficult to match the complex compositional characteristics of alloys. In contrast, this method directly prepares a high-purity matrix solution that is completely consistent with the sample based on the compositional proportions of the matrix elements Fe, Cr, Mo, and Nb. The matrix matching degree is extremely high, which can significantly reduce the mass spectrometry suppression and matrix effect of high-content iron, chromium, molybdenum, and niobium on trace impurities. This is a highly targeted and optimized design among similar high-alloy detection methods.

[0058] Traditional single internal standard calibration methods have limited applicability and struggle to simultaneously detect multiple components with wide mass ranges and significant differences in ionization energies. This proposed method, based on the mass range and ionization energy characteristics of the analyte, selects three internal standard elements—Rh, Ge, and Re—to achieve internal standard calibration across the entire mass range of elements such as Al, Co, Ni, V, W, Cu, and Mn. This effectively compensates for the shortcomings of single internal standard calibration, significantly improving the accuracy of impurity element determination and representing a methodological optimization and improvement.

[0059] E. Preparation of reagent blank solution: Prepare a reagent blank solution without the test sample by using the same digestion steps and reagents as the test sample.

[0060] Step 5, determination of trace impurity elements:

[0061] Optimize the operating parameters of the inductively coupled plasma mass spectrometer:

[0062] Eleven consecutive determinations of the blank sample solution yielded a detection limit of less than 0.028 ng / mL, calculated using three times the standard deviation of the measured values. A quantitation limit of less than 0.077 ng / mL was calculated using ten times the standard deviation of the measured values. Multiple parallel determinations of the test sample and the spiked recovered sample showed relative standard deviations of less than 5.63%, with recoveries ranging from 95.0% to 105.5%. See the experimental results below for details.

[0063] Optimization of ICP-MS detection conditions:

[0064] Instrument: Inductively Coupled Plasma Mass Spectrometer

[0065] 1. Select an inductively coupled plasma mass spectrometer with a mass resolution of no more than 0.8 amu. Optimize the mass spectrometer using a mixed tuning solution, tuning it until the double charge yield and oxide yield are less than 2.5%. Specifically tune it for this alloy matrix until FeO⁺ / Fe⁺ and NbO⁺ / Nb⁺ are both less than 1.0%, so that the instrument's strength, sensitivity, and stability reach the optimal operating parameters.

[0066] 2. Helium gas is introduced as the reaction gas, with a flow rate of 4.5 mL / min. Operating parameters: RF power 1500 W, plasma gas flow rate 14.0 L / min, auxiliary gas flow rate 0.8 L / min, nebulizer flow rate 0.92 L / min, nebulizer temperature 2.5℃, sampling depth 5.00 mm, sample flushing time 30 s, scanning mode peak skipping, integration residence time 80 ms, single element integration time 6 s, and isotope detection... 27 Al、 5 ¹V、 55 Mn, 59 Co、 60 Ni、 6 ³Cu、 184 W, during the measurement process, select 45 Sc、 103 Rh、 187 Re is used as an internal index element.

[0067] Table 2: Selection of Detectable Elements and Mass Numbers

[0068]

[0069] The elemental content in the iron-chromium-molybdenum-niobium alloy sample is calculated according to formula (1):

[0070] (1)

[0071] In formula (1): ρ is the mass concentration of the element to be tested in the analytical solution, in ng / mL; ρ0 is the mass concentration of the element to be tested in the blank solution, in ng / mL; V is the total volume of the test solution, in mL; and m is the mass of the sample, in g.

[0072] Based on the differences in elemental interference, select the appropriate determination mode, such as KED or STD determination mode, and control the collision gas flow rate; determine the analyte in the blank solution, and calculate the limit of detection and limit of quantitation; perform multiple determinations on the test sample and the spiked sample, and calculate the RSD and spiked recovery rate.

[0073] Eleven consecutive measurements were performed on the blank solution. The limit of detection (LOD) of the method was determined by taking three times the standard deviation of the determination result of the analyte in the blank solution, and the limit of quantitation (LOQ) of the method was determined by taking ten times the standard deviation. The LOD and LOQ of the method are shown in Table 3.

[0074] Table 3 Limit of detection and limit of quantitation for this method

[0075]

[0076] As shown in Table 3, the detection limit of the analyte is less than 0.028 ng / mL, and the quantitation limit is less than 0.077 ng / mL.

[0077] 2. Precision test

[0078] Two batches of samples with different contents of the elements to be tested were selected respectively to conduct precision tests on the method. The results are shown in Table 4.

[0079] Table 4 Method Precision Experiment

[0080]

[0081] As shown in Table 4, the RSDs are all less than 5.63%, indicating that the method has good precision and can meet the analytical requirements.

[0082] Accuracy test

[0083] Accurately weigh the sample for spike recovery test, calculate the spike recovery rate, and the results are shown in Table 5.

[0084] Table 5 Spiked Recovery Test of Samples

[0085]

[0086] As shown in Table 5, the recovery rate of impurity elements in the iron-chromium-molybdenum-niobium alloy is between 95.0% and 105.5%, with good accuracy.

[0087] This invention addresses the challenges of detecting impurities in iron-chromium-molybdenum-niobium alloys using inductively coupled plasma mass spectrometry (ICP-MS). Specifically, it addresses the severe interference from carbon, nitrogen, and oxygen polyatomic ions during ICP-MS determination of aluminum. Based on the differences in elemental interference, this invention selects appropriate measurement modes, such as KED or STD modes, and prioritizes the detection of high-mass isotopes. This effectively eliminates mass spectrometry interference, reduces background noise, and significantly improves the accuracy and precision of aluminum determination, providing an efficient and reliable method for the accurate detection of trace aluminum in complex matrices.

[0088] To address the problem that tungsten readily forms oxide ions such as WO⁺ in plasma, causing severe mass spectrometry interference to other analytes and leading to decreased accuracy of measurement results, this invention optimizes carrier gas flow parameters and regulates plasma operating conditions and element ionization behavior. This effectively suppresses the formation of tungsten oxide ions, significantly reduces the yield of polyatomic ions such as WO⁺ and their mass spectrometry interference with the determination of coexisting elements, and improves the accuracy and stability of simultaneous multi-element determination in complex systems. This provides a reliable technical solution for the precise analysis of trace impurity elements in tungsten-containing matrix samples.

[0089] To address the problem that high concentrations of iron, chromium, molybdenum, and niobium in samples can easily cause significant matrix inhibition effects, leading to low aluminum detection signals and distorted quantitative results, this invention employs a combined correction strategy of internal standard correction, gradient dilution, and matrix matching. This effectively compensates for the inhibitory effect of high-concentration coexisting matrices on the ionization signals of light elements, eliminates systematic biases caused by matrix effects, significantly improves the accuracy and precision of light element determination, and enables stable and reliable quantitative analysis of trace light elements in complex high-matrix samples.

[0090] For the sample 56 Fe⁺ and 56 Significant detection interference from Ni⁺ due to mass overlap of isotopes leads to 56 To address the challenges of Ni⁺ signal identification and distorted quantitative results, this invention employs a three-tiered synergistic correction strategy: "interference-free isotope selection - high-resolution mass spectrometry separation - collision / reaction cell purification." This strategy prioritizes the selection of... 58 Ni⁺、 60 Low-interference target isotopes such as Ni⁺ are used to avoid direct interference at the source. Residual isotope signals are separated by high-resolution mass spectrometry (≥10000 resolution), and then residual isotope signals are selectively eliminated using a collision / reaction cell optimized with helium / ammonia reaction mode. 56 Fe⁺ and polyatomic interfering species effectively compensate 56 Fe⁺ against 56 By eliminating interference in Ni⁺ detection and removing systematic biases, significant improvements can be achieved without complex sample pretreatment. 56 The sensitivity, precision, and accuracy of Ni⁺ detection enable stable and reliable quantitative analysis of trace nickel in complex matrix samples.

[0091] To address the problem that high concentrations of Fe, Cr, Mo, and Nb in the matrix of samples can significantly interfere with the detection of target elements, leading to deviations and insufficient accuracy in quantitative results, this invention employs a matrix matching method to prepare standard solutions. By simulating the matrix composition and concentration levels of Fe, Cr, Mo, and Nb in the sample using the standard solutions, the interference of matrix effects on the detection signal is reduced from the source. Simultaneously, the accuracy and reliability of the method are systematically verified using spike recovery validation techniques, effectively eliminating systematic errors caused by matrix interference, significantly improving the accuracy and reliability of target element determination, and achieving precise and reliable quantitative analysis of target elements in complex matrix samples.

[0092] To address the issue of Al being highly susceptible to contamination, high-purity reagents were used, and polytetrafluoroethylene (PTFE) glassware rinsed with high-purity water was employed for pretreatment and determination. This effectively eliminated matrix interference and external contamination, ensuring the accuracy and reliability of the analytical results.

[0093] To address the issues of cone clogging and signal drift caused by high matrix samples, regular replacement and cleaning of the cone are employed to reduce physical interference. Simultaneously, an internal standard element is introduced for real-time monitoring and correction, effectively suppressing signal fluctuations and matrix effects, and significantly improving measurement stability and data accuracy.

[0094] This invention establishes an analytical method for determining trace impurity elements in FeCrMoNb alloys based on microwave digestion-inductively coupled plasma mass spectrometry (ICP-MS). This method utilizes a mixed acid system composed of nitric acid, hydrochloric acid, and hydrofluoric acid. Under optimized pretreatment conditions, microwave digestion enables rapid and efficient dissolution of FeCrMoNb alloys. It achieves simple and efficient simultaneous determination of multiple impurity elements in FeCrMoNb alloys, with low detection limits and a wide linear range. This improves the convenience of FeCrMoNb alloy sample preparation, enhances the accuracy of sample detection, and reduces equipment wear and tear.

[0095] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. An analytical method for determining trace impurity elements in iron-chromium-molybdenum-niobium alloys, characterized in that... Includes the following steps: Sample preparation: The iron-chromium-molybdenum-niobium alloy sample was prepared into fine particles, and 0.1000g of the sample was accurately weighed into a digestion vessel; Sample dissolution: Add 1-2 mL of ultrapure water to the microwave digestion vessel containing the sample for wetting, and then add 9 mL of a mixed acid solution of hydrochloric acid, nitric acid and hydrofluoric acid for digestion. The volume ratio of nitric acid: hydrochloric acid: hydrofluoric acid in the mixed acid solution is 3-5:3-5:2-3 to ensure that the mixed acid solution is in full contact with the sample. Microwave digestion: Using microwave digestion, the sample is completely digested by undergoing the following four stages followed by natural cooling. The first stage involves raising the temperature to 120-130℃ and holding for 5-7 minutes; the second stage involves raising the temperature to 150-160℃ and holding for 5-7 minutes; the third stage involves raising the temperature to 200℃ and holding for 10-15 minutes; and the fourth stage involves raising the temperature to 220℃ and holding for 30-35 minutes. Preparation of standard solutions: A. Mixed standard solutions: Prepare mixed standard solutions of aluminum, cobalt, nickel, vanadium, tungsten, copper, and manganese; B. Matrix solution preparation: According to the matrix element composition ratio of the sample, weigh out high-purity metallic iron, chromium, molybdenum and niobium reference materials respectively, add them to the mixed acid system for dissolution, and prepare a matrix solution that matches the matrix composition of the sample. C. Preparation of a series of standard solutions: Pipette 10 mL of the matrix solution and the mixed standard solution into seven 100 mL volumetric flasks, and then add a certain amount of the 10.0 μg / mL mixed standard solution to each of the seven flasks to prepare a series of standard solutions with concentrations of 0 ng / mL, 1.0 ng / mL, 2.0 ng / mL, 5.0 ng / mL, 10.0 ng / mL, 20.0 ng / mL, and 50.0 ng / mL. D. Preparation of mixed internal standard solution: Select... 45 Sc、 103 Rh、 187 Re was used as an internal standard element to prepare a mixed internal standard solution; Trace impurity element determination: The working parameters of the inductively coupled plasma mass spectrometer were optimized. When determining trace impurity elements in the sample solution, the measuring device was connected by a three-way connector to connect the sample injection pipeline and the mixed internal standard solution pipeline, so as to realize the online addition and synchronous determination of the internal standard element. The sample solution was introduced into ICP-MS to measure the signal intensity of each impurity element. The mixed internal standard solution was introduced online and synchronously to correct for signal drift and matrix effect. The content of each impurity element in the sample was quantitatively calculated based on the standard series working curves. The elemental content in the iron-chromium-molybdenum-niobium alloy sample is calculated according to formula (1): (1) In formula (1): ρ is the mass concentration of the element to be tested in the analytical solution, in ng / mL; ρ0 is the mass concentration of the element to be tested in the blank solution, in ng / mL; V is the total volume of the test solution, in mL; and m is the mass of the sample, in g. E. Preparation of reagent blank solution: Prepare a reagent blank solution without the test sample by using the same digestion steps and reagents as the test sample.

2. The method of analysis for determining trace impurity elements in ferrochromium-molybdenum-niobium alloy as claimed in claim 1, wherein: The specific sample processing steps are as follows: the iron-chromium-molybdenum-niobium alloy sample is processed to a particle size ≤0.125mm or ≤120 mesh, and 0.1000g±0.0001g of sample is accurately weighed into a digestion vessel.

3. The method of analysis for determining trace impurity elements in ferrochrome-molybdenum-niobium alloys as claimed in claim 1, wherein: In the sample dissolution step: hydrochloric acid, nitric acid and hydrofluoric acid are added sequentially to digest the sample. The mixture is gently shaken to ensure full contact between the mixed acid and the sample, and then allowed to stand for a pre-reaction of 10-15 minutes.

4. The method for analyzing trace impurity elements in a ferrochromium-molybdenum-niobium alloy according to any one of claims 1 to 3, characterized in that: The digestion vessel is a polytetrafluoroethylene digestion vessel; the nitric acid concentration is between 65-68% and the purity level is high; the concentrated hydrochloric acid concentration is between 36-38% and the purity level is high; the hydrofluoric acid concentration is ≥40% and the purity level is high.

5. The analytical method for determining trace impurity elements in iron-chromium-molybdenum-niobium alloys as described in claim 1, characterized in that: In the microwave digestion step, the microwave power is 400-600W in the first stage, 600-800W in the second stage, 800-1000W in the third stage, and 1000-1100W in the fourth stage.

6. The method of analysis for determining trace impurity elements in ferrochromium-molybdenum-niobium alloys as claimed in claim 1, wherein: The microwave digestion step also includes, after digestion, allowing it to cool naturally, then adding 2 mL of nitric acid, transferring it to a 100 mL volumetric flask, making up to the mark with ultrapure water, and shaking well for later use.

7. The analytical method for determining trace impurity elements in iron-chromium-molybdenum-niobium alloys as described in claim 1, characterized in that: In the standard solution preparation steps, the mixed standard solution is prepared by transferring 1 mL of 1000 μg / mL aluminum, cobalt, nickel, vanadium, tungsten, copper, and manganese standard storage solutions into 100 mL plastic volumetric flasks and diluting them to the mark with ultrapure water. This solution is 10.0 μg / mL. The matrix solution is prepared by weighing 0.9990–1.0000 g of high-purity metallic iron, chromium, molybdenum, and niobium reference materials with the same elemental composition as the sample into a 100 mL polytetrafluoroethylene beaker. Then, 1–2 mL of ultrapure water is added for wetting, followed by the addition of 9 mL of a mixed acid solution (9 mL each of hydrochloric acid, nitric acid, and hydrofluoric acid) for digestion. The volume ratio of nitric acid:hydrochloric acid:hydrofluoric acid in the mixed acid solution is 3-5:3-5:2-3. The mixed acid solution is allowed to fully contact the sample. The mixture is allowed to stand at room temperature for 10–15 min for pre-reaction, and then placed in a 60–80 °C constant temperature water bath. The solution is then heated to 70 °C. A constant temperature water bath is best. The solution is taken until it is clear and transparent with no metal powder residue. It is then removed and cooled. After cooling, it is transferred to a 100mL volumetric flask, 10mL of nitric acid is added, and it is diluted to the mark with ultrapure water. The solution is then made up to volume and shaken well before use.

8. The method of analysis for determining trace impurity elements in ferrochrome-molybdenum-niobium alloys as claimed in claim 1, wherein: The standard solution preparation step, the mixed internal standard solution preparation is specifically that a certain amount of 1.0 μg / mL 45 Sc、 103 Rh、 187 Re standard storage solution in 100ml plastic volumetric flask, preparation is 8 ng / mL mixed internal standard solution.

9. The method of analysis for determining trace impurity elements in ferrochrome-molybdenum-niobium alloys as claimed in claim 1, wherein: In the trace impurity element determination step, an inductively coupled plasma mass spectrometer with a mass resolution of no more than 0.8 amu was selected. The mass spectrometer was optimized using a mixed tuning solution, tuned to achieve a double charge yield of less than 2.5% and an oxide yield of less than 2.5%. Specifically tuned for this alloy matrix, the FeO⁺ / Fe⁺ and NbO⁺ / Nb⁺ ratios were both less than 1.0%. Helium was introduced as the reaction gas at a flow rate of 4.5 mL / min. Operating parameters were: RF power 1500 W, plasma gas flow rate 14.0 L / min, auxiliary gas flow rate 0.8 L / min, nebulizer flow rate 0.92 L / min, nebulizer temperature 2.5℃, sampling depth 5.00 mm, sample flushing time 30 s, peak skipping scanning mode, integration residence time 80 ms, single element integration time 6 s, and isotope detection. 27 Al、 5 ¹V、 55 Mn, 59 Co、 60 Ni、 63 Cu、 184 W, during the measurement process, select 45 Sc、 103 Rh、 187 Re is used as an internal index element.

10. The method of analysis for determining trace impurity elements in ferrochrome-molybdenum-niobium alloys as claimed in claim 1, wherein: In the trace impurity element determination step, the optimized operating parameters of the inductively coupled plasma mass spectrometer are as follows: the signal intensity of the trace impurity element to be measured in the blank solution is continuously measured, and the detection limit of the trace impurity element to be measured is less than 0.028 ng / mL and the quantitation limit is less than 0.077 ng / mL by statistical calculation method; multiple parallel repeated determinations are performed on the test sample and the spiked recovery sample, and the relative standard deviation of the calculation method is less than 5.63% and the spiked recovery rate is between 95.0% and 105.5%.

Images