Method for detecting content of cerium element in rare earth steel

Abstract

The invention discloses a method for detecting the content of a cerium element in rare earth steel. The method comprises the following steps: preparing a sample from the rare earth steel; the sample serves as an anode, an inert electrode serves as a cathode, the anode and the cathode are connected with a direct-current power source, the mixture is immersed in electrolyte for electrolysis, and a rare earth electrolysis separated phase is obtained; washing the rare earth electrolysis separated phase with an iodine-containing methanol solution, and filtering to obtain a precipitate and a filtrate containing rare earth sulfide; washing the precipitate with hydrochloric acid and citric acid, and filtering to obtain a filtrate containing a rare earth sulfur oxide compound and a rare earth precipitate; the rare earth precipitate is rare earth oxide; dissolving the filtrate containing the rare earth sulfide, the filtrate containing the rare earth oxysulfide and the rare earth precipitate with an acid, adding perchloric acid for smoking, adding an acid, dissolving at a low temperature until the solution is clear and transparent, cooling to room temperature, and fixing the volume to obtain a to-be-tested sample; preparing a cerium standard solution; and drawing a standard curve, detecting the to-be-detected sample under the same condition, and respectively calculating the content of the cerium element in the to-be-detected sample according to the standard curve.

Description

Technical Field

[0001] The invention relates to the technical field of materials and metallurgy, and more specifically, to a method for detecting the content of cerium in rare earth steel. Background Art

[0002] Rare earth RE has active chemical properties. It reacts with almost all non-metallic elements. Adding a small amount of rare earth to steel can play a role in purification, modification and micro-alloying. Rare earth RE exists in steel in complex forms and is divided into different phases, including rare earth oxide RE 2 O 3 , Rare earth oxysulfides RE 2 O 2 S, rare earth sulfide RE x S y Each phase of rare earth in steel has different effects on the properties of steel and needs to be separated and tested.

[0003] The existing technologies for detecting the content of rare earth elements in steel include: gravimetric method "GB / T 6730.25-2021 Determination of the total amount of rare earth elements in iron ore - Oxalate gravimetric method": the sample is melted with sodium hydroxide and sodium peroxide, leached with triethanolamine, interfering elements are separated using EDTA, rare earths are precipitated with oxalic acid, the precipitate is burned at 900°C, and weighed to obtain the amount of rare earth oxides; colorimetric method "GB / T 223.49-1994 Chemical analysis method for steel and alloys - Extraction and separation - Azochlorophosphonium A spectrophotometric method for the determination of the total amount of rare earths": at a pH of about 2, iron is extracted and separated with acetylacetone-chloroform, at a pH of 5.5, rare earths and other coexisting elements are extracted and separated with PMBP-benzene, and azochlorophosphonium A is used for color development, and its absorbance is measured at a wavelength of 670 mm on a spectrophotometer, and the color development curve of gadolinium Gd is used as the working curve for determining the total amount of rare earths. However, the gravimetric method cannot identify and detect the various phases of rare earths, and the error in detecting low-content rare earth samples is large; the colorimetric method is characterized by the Gd element, and the Gd element is relatively low in rare earth content, which is easy to cause errors. Ding Meiying et al. used the ICP-AES method to determine the La, Ce, Pr, Nd, and Sm contents of rare earth inclusions in steel. This method focused on the improvement and effect of the instrument setting conditions when the ICP-AES method was used to detect rare earth elements, and did not distinguish between the various phases of rare earths in steel. Fang Keming et al. determined the rare earth content in the metal phase of 16MnRE steel, but the detection method was radioactive and had an impact on personnel health. The Chinese patent with application number 202210733911.X discloses a method for detecting the content of solid-solution rare earths in steel and its application, but the method is cumbersome to operate and can only analyze the rare earth content in the solid-solution phase, and does not involve the detection of more important rare earth oxides and sulfides. Li Jie et al. conducted research on the analysis and detection of rare earth elements lanthanum, cerium and yttrium in steel, and also did not distinguish between the phases of rare earth elements in steel.

[0004] Therefore, it is necessary to develop an experimental method including sample processing, phase separation, and instrument detection to determine the cerium content of each rare earth phase in steel. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and provide a method for detecting the cerium content in rare earth steel, which can separate the various phases of rare earth in rare earth steel and characterize its content and distribution by detecting the cerium content. This can be used as data basis to observe and analyze the influence of rare earth phase on steel performance.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A method for detecting the cerium content in rare earth steel comprises the following steps:

[0008] (1) Preparing rare earth steel into samples;

[0009] (2) using the sample as an anode and an inert electrode as a cathode, filling an electrolytic cell with an electrolyte, connecting the anode and the cathode to a DC power supply, immersing the anode and the cathode in the electrolyte for electrolysis, and obtaining a rare earth electrolytic precipitation phase;

[0010] (3) washing the rare earth electrolytic precipitation phase with an iodine-containing methanol solution and filtering it to obtain a precipitate and a filtrate containing rare earth sulfides; and washing the precipitate with hydrochloric acid and citric acid and filtering it to obtain a filtrate containing rare earth sulfur oxides and a rare earth precipitate; the rare earth precipitate is a rare earth oxide;

[0011] (4) dissolving the filtrate containing rare earth sulfide, the filtrate containing rare earth sulfur oxides, and the rare earth precipitate respectively with a mixed acid of hydrochloric acid and nitric acid, adding perchloric acid to generate smoke, then adding a mixed acid of hydrochloric acid and nitric acid to dissolve at low temperature until clear and transparent, cooling to room temperature, and fixing the volume to obtain a first sample to be tested, a second sample to be tested, and a third sample to be tested, respectively;

[0012] (5) preparing a cerium standard solution; after selecting a standard cerium mother solution, using nitric acid to prepare a cerium standard solution with a gradient concentration of 0.0 μg / mL to 1 μg / mL;

[0013] (6) Introducing the cerium standard solution into an inductively coupled plasma atomic emission spectrometer for measurement to obtain a standard curve, and detecting the first sample to be tested, the second sample to be tested, and the third sample to be tested under the same conditions, respectively, and calculating the cerium content in the first sample to be tested, the second sample to be tested, and the third sample to be tested according to the standard curve.

[0014] Implementing the embodiments of the present invention will have the following beneficial effects:

[0015] 1. This method is simple to operate and easy for other experimenters to learn. The instrument settings are simple and common, and easy for other laboratories to use.

[0016] 2. This method can detect the cerium content of each phase in steel and estimate the content and distribution of each phase of rare earth in steel, which is conducive to observing and analyzing the influence of rare earth phase on steel performance.

[0017] 3. This method requires fewer chemical reagents and is easy to obtain, which can save a lot of cost for purchasing standard samples, consume less labor, and the detection is repeatable, making it more suitable for daily detection in steel production.

[0018] 4. The present invention takes into account that the largest rare earth element contained in rare earth steel is cerium Ce and the proportion is relatively fixed (accounting for about 40% to 50%). Therefore, the present application utilizes the differences in the physical and chemical properties of various rare earth phases. First, electrolysis and chemical reagent leaching and filtration are used to separate the various rare earth phases in steel. Then, inductively coupled plasma atomic emission spectrometry is used to detect the content of cerium Ce elements in various rare earth phases. This is used as a characterization to infer the distribution and content of various rare earth phases, and then this is used as a data basis to observe and analyze the influence of rare earth phases on steel performance. The method is simple, fast, accurate, and has low detection cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the cerium element standard curve of Example 1 of the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited in any way.

[0021] The invention discloses a method for detecting the cerium content in rare earth steel, comprising the following steps:

[0022] (1) Prepare rare earth steel into samples.

[0023] In a specific embodiment, step (1) specifically includes: processing the rare earth steel into a sample in the shape of a rod or a sheet, and performing drilling and polishing to remove the oxide layer and / or rust on the surface of the sample.

[0024] In one embodiment, the sample surface area is required to be no less than 40 cm 2 , the length should be less than the height of the electrolytic cell.

[0025] (2) The sample is used as the anode and the inert electrode is used as the cathode. The electrolyte is contained in the electrolytic cell. The anode and the cathode are connected to a DC power supply and immersed in the electrolyte for electrolysis to obtain a rare earth electrolytic precipitation phase.

[0026] In a specific embodiment, an electrolytic cell of suitable size is selected, a DC power supply is used, the processed sample is used as the anode and the inert electrode is used as the cathode, good current stability is maintained, the positive and negative electrodes are fixed by insulating material equipment, the distance between the cathode and the anode is 5cm to 20cm, and the bottom positions of the anode and the cathode do not touch the inner wall of the electrolytic cell; a methanol solution of lithium chloride with a mass percentage of 1% to 4% and sulfosalicylic acid with a mass percentage of 2% to 6% is used as the electrolyte, and the volume of the electrolyte is 300mL to 2000mL according to the size of the electrolytic cell; the sample is electrolyzed under the conditions of an electrolytic reaction voltage of 25V to 30V, an electrolytic reaction temperature of less than 10°C, and an electrolytic reaction time of 2h to 48h to obtain a rare earth electrolytic precipitation phase.

[0027] (3) The rare earth electrolytic precipitation phase is washed with an iodine-containing methanol solution and filtered to obtain a precipitate and a filtrate containing rare earth sulfides; and the precipitate is washed with hydrochloric acid and citric acid and filtered to obtain a filtrate containing rare earth sulfide compounds and a rare earth precipitate; the rare earth precipitate is a rare earth oxide.

[0028] In a specific embodiment, in step (3), the mass concentration of the iodine-containing methanol solution is 10%; the mass concentration of the hydrochloric acid is 1%; and the mass concentration of the citric acid is 5%.

[0029] (4) The filtrate containing rare earth sulfide, the filtrate containing rare earth sulfur oxides, and the rare earth precipitate are respectively dissolved with a mixed acid of hydrochloric acid and nitric acid, and then perchloric acid is added to generate smoke, and then a mixed acid of hydrochloric acid and nitric acid is added to dissolve at low temperature until the mixture becomes clear and transparent, and then the mixture is cooled to room temperature and fixed to volume to obtain a first sample to be tested, a second sample to be tested, and a third sample to be tested, respectively.

[0030] (5) preparing a cerium standard solution; after selecting a standard cerium mother solution, using nitric acid with a mass concentration of 10% to prepare a cerium standard solution with a gradient concentration of 0.0 μg / mL to 1 μg / mL.

[0031] In a specific embodiment, in step (5), the preparation of the cerium standard solution specifically includes the following steps: taking 0.00mL, 1.00mL, 3.00mL, 5.00mL, 7.00mL, and 10.00mL of a standard mother solution of cerium with a concentration of 10.0μg / mL and then fixing the volume to prepare cerium standard solutions with cerium concentrations of 0.0μg / mL, 0.1μg / mL, 0.3μg / mL, 0.5μg / mL, 0.7μg / mL, and 1.0μg / mL, respectively.

[0032] (6) Introducing the cerium standard solution into an inductively coupled plasma atomic emission spectrometer for measurement to obtain a standard curve, and detecting the first sample to be tested, the second sample to be tested, and the third sample to be tested under the same conditions, respectively, and calculating the cerium content in the first sample to be tested, the second sample to be tested, and the third sample to be tested according to the standard curve.

[0033] In a specific embodiment, in step (6), the detection conditions are as follows: gas atmosphere: argon; integration time: 10s to 30s; flushing time: 20s to 60s; detection wavelength: 404.08nm; flushing pump speed: 40rpm to 60rpm; RF power: 1150W.

[0034] In a specific embodiment, in step (6), the calculation is specifically based on the following formula:

[0035] ω ref =BI ref +A (1)

[0036] Among them, ω ref : Rare earth content of standard sample, %; I ref : absorbance of the standard sample; B: slope of the working curve; A: intercept of the working curve.

[0037] In a specific embodiment, the mass content of cerium in the sample is 0.000% to 0.100%.

[0038] The following are specific embodiments

[0039] Example 1

[0040] The method for detecting the cerium content in rare earth steel of this embodiment comprises the following steps:

[0041] (1) Process the rare earth steel into rod-shaped or sheet-shaped specimens, and perform drilling and polishing to remove the oxide layer and / or rust on the surface of the specimens. The surface area of ​​the specimens should be no less than 40 cm 2 , the length should be less than the height of the electrolytic cell.

[0042] (2) Select an electrolytic cell of suitable size, use a direct current power supply, use the processed sample as the anode and the inert electrode as the cathode, maintain good current stability, use insulating material equipment to fix the positive and negative electrodes, the distance between the cathode and the anode is 5 cm, and the bottom positions of the anode and the cathode do not touch the inner wall of the electrolytic cell; use a methanol solution of 2% lithium chloride and 4% sulfosalicylic acid by mass as the electrolyte, and the volume of the electrolyte is 500 mL according to the size of the electrolytic cell; under the conditions of an electrolytic reaction voltage of 25 V, an electrolytic reaction temperature of <10° C., and an electrolytic reaction time of 48 h, the sample is electrolyzed to obtain a rare earth electrolytic precipitation phase.

[0043] (3) The rare earth electrolytic precipitation phase is washed with an iodine-containing methanol solution and filtered to obtain a precipitate and a filtrate containing rare earth sulfide; the precipitate is washed with hydrochloric acid and citric acid and filtered to obtain a filtrate containing rare earth oxysulfide and a rare earth precipitate; the rare earth precipitate is a rare earth oxide. The mass concentration of the iodine-containing methanol solution is 10%; the mass concentration of the hydrochloric acid is 1%; and the mass concentration of the citric acid is 5%.

[0044] (4) The filtrate containing rare earth sulfide, the filtrate containing rare earth sulfur oxides and the rare earth precipitate are respectively subjected to HCl and HNO 3 After the mixed acid is dissolved, add perchloric acid to make it smoke, then add HCl and HNO 3 The mixed acid is dissolved at low temperature until it is clear and transparent, cooled to room temperature, and fixed to volume to obtain a first sample to be tested, a second sample to be tested, and a third sample to be tested, respectively.

[0045] (5) Take 0.00mL, 1.00mL, 3.00mL, 5.00mL, 7.00mL, and 10.00mL of the standard stock solution of cerium with a concentration of 10.0μg / mL and dilute to volume to prepare standard cerium solutions with cerium concentrations of 0.0μg / mL, 0.1μg / mL, 0.3μg / mL, 0.5μg / mL, 0.7μg / mL, and 1.0μg / mL, respectively.

[0046] (6) The cerium standard solution is introduced into the inductively coupled plasma atomic emission spectrometer for measurement to obtain a standard curve, and the first sample to be tested, the second sample to be tested and the third sample to be tested are respectively detected under the same conditions, and the content of cerium in the first sample to be tested, the second sample to be tested and the third sample to be tested are respectively calculated according to the standard curve. The detection conditions are as follows: gas atmosphere: argon; integration time: 30 s; flushing time: 30 s; detection wavelength: 404.08 nm; flushing pump speed: 60 rpm; RF power: 1150 W.

[0047] The specific calculation is based on the following formula:

[0048] ω ref =BI ref +A (1)

[0049] Among them, ω ref : Rare earth content of standard sample, %; I ref : absorbance of the standard sample; B: slope of the working curve; A: intercept of the working curve.

[0050] Test Case

[0051] 1. Precision analysis

[0052] Standard samples of boron steel 37-8, CrNiCuMoRE 6905, and boron steel 37-9 were selected for testing according to the method of Example 1. The results are shown in Table 1.

[0053] Table 1 Precision test results

[0054]

[0055]

[0056] According to the results in Table 1, the maximum differences between the independent phase measurement results of standard samples boron steel 37-8, CrNiCuMoRE 6905, and boron steel 37-9 are all less than the maximum allowable repeatability error, so the precision of this method meets the inspection requirements.

[0057] 2. Comparative example analysis

[0058] The standard sample boron steel 37-9 was selected and measured by the method of Example 1 and the colorimetric method, wherein the colorimetric method was based on GB / T 223.49-1994 Chemical Analysis Methods for Iron and Steel and Alloys Extraction and Separation - Determination of Total Rare Earth Content by Chlorophosphonazo mA Spectrophotometric Method. The results are shown in Table 2:

[0059] Table 2 Comparison of the results of colorimetry and ICP method for each phase of rare earth in boron steel 37-9

[0060]

[0061] According to the results in Table 2, the ratios of the measurement results of each phase of the same standard sample by colorimetry and ICP are basically consistent, and this method is feasible.

[0062] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for detecting the cerium content in rare earth steel, characterized in that: The following steps are involved: (1) Preparing rare earth steel into samples; (2) using the sample as an anode and an inert electrode as a cathode, filling an electrolytic cell with an electrolyte, connecting the anode and the cathode to a DC power supply, immersing the anode and the cathode in the electrolyte for electrolysis, and obtaining a rare earth electrolytic precipitation phase; (3) washing the rare earth electrolytic precipitation phase with an iodine-containing methanol solution and filtering it to obtain a precipitate and a filtrate containing rare earth sulfides; and washing the precipitate with hydrochloric acid and citric acid and filtering it to obtain a filtrate containing rare earth sulfur oxides and a rare earth precipitate; the rare earth precipitate is a rare earth oxide; (4) dissolving the filtrate containing rare earth sulfide, the filtrate containing rare earth sulfur oxides, and the rare earth precipitate respectively with a mixed acid of hydrochloric acid and nitric acid, adding perchloric acid to generate smoke, then adding a mixed acid of hydrochloric acid and nitric acid to dissolve at low temperature until clear and transparent, cooling to room temperature, and fixing the volume to obtain a first sample to be tested, a second sample to be tested, and a third sample to be tested, respectively; (5) preparing a cerium standard solution; after selecting a standard cerium mother solution, using nitric acid to prepare a cerium standard solution with a gradient concentration of 0.0 μg / mL to 1 μg / mL; (6) Introducing the cerium standard solution into an inductively coupled plasma atomic emission spectrometer for measurement to obtain a standard curve, and detecting the first sample to be tested, the second sample to be tested, and the third sample to be tested under the same conditions, respectively, and calculating the cerium content in the first sample to be tested, the second sample to be tested, and the third sample to be tested according to the standard curve.

2. The method for detecting the cerium content in rare earth steel according to claim 1, characterized in that: Step (1) specifically comprises: processing the rare earth steel into a rod or sheet shape with a surface area of ​​not less than 40 cm 2 The sample is drilled and polished to remove the oxide layer and / or rust on the surface of the sample.

3. The method for detecting the cerium content in rare earth steel according to claim 2, characterized in that: In step (2), the electrolyte comprises the following components in percentage by weight: 1% to 4% lithium chloride and 2% to 6% methanol solution of sulfosalicylic acid.

4. The method for detecting the cerium content in rare earth steel according to claim 2, characterized in that: In step (2), the distance between the cathode and the anode is 5 cm to 20 cm; The voltage of the electrolysis reaction is 25V to 30V, the temperature of the electrolysis reaction is less than 10°C, and the time of the electrolysis reaction is 2h to 48h.

5. The method for detecting the cerium content in rare earth steel according to claim 1, characterized in that: In step (3), the mass concentration of the iodine-containing methanol solution is 10%; the mass concentration of the hydrochloric acid is 1%; and the mass concentration of the citric acid is 5%.

6. The method for detecting the cerium content in rare earth steel according to claim 1, characterized in that: In step (6), the detection conditions are as follows: gas atmosphere: argon; integration time: 10s to 30s; flushing time: 20s to 60s; detection wavelength: 404.08nm; flushing pump speed: 40rpm to 60rpm; RF power: 1150W.

7. The method for detecting the cerium content in rare earth steel according to claim 1, characterized in that: In step (6), the calculation is specifically based on the following formula: ω ref =BI ref +A(1) Among them, ω ref : Rare earth content of standard sample, %; I ref : absorbance of the standard sample; B: slope of the working curve; A: intercept of the working curve.

8. The method for detecting the cerium content in rare earth steel according to claim 1, characterized in that: In the step (5), the preparation of the cerium standard solution specifically includes the following steps: taking 0.00mL, 1.00mL, 3.00mL, 5.00mL, 7.00mL, and 10.00mL of a standard mother solution of cerium with a concentration of 10.0μg / mL and then fixing the volume to prepare cerium standard solutions with cerium concentrations of 0.0μg / mL, 0.1μg / mL, 0.3μg / mL, 0.5μg / mL, 0.7μg / mL, and 1.0μg / mL, respectively.

9. The method for detecting the cerium content in rare earth steel according to claim 1, characterized in that: The mass content of cerium in the sample is 0.000% to 0.100%.

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