Method for Accurate Determination of Rare Earth Sulfide and Rare Earth Oxysulfide Inclusions in Rare Earth Weathering Steel

Abstract

The present invention discloses a method for accurately determining rare earth sulfide and rare earth oxysulfide inclusions in rare earth weathering steel, which belongs to the technical field of metal material analysis and is used to solve the problem that the prior art cannot accurately determine rare earth sulfide and rare earth oxysulfide inclusions in rare earth weathering steel. The method of the present invention comprises first electrolytically extracting the rare earth weathering steel, then separating carbides by magnetic separation, retaining inclusions, and then using EDTA solution to separate carbides and unstable rare earth sulfide inclusions, retaining rare earth oxysulfide inclusions. The method of the present invention realizes the separation of rare earth sulfide and rare earth oxysulfide inclusions in rare earth weathering steel, and after the rare earth sulfide and rare earth oxysulfide inclusions are separated, the content of rare earth sulfide and rare earth oxysulfide inclusions can be accurately determined.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material analysis, and in particular relates to a method for accurately determining rare earth sulfide and rare earth oxysulfide inclusions in rare earth weathering steel. Background Art

[0002] Non-metallic inclusions in steel have an important influence on the performance of steel. For weathering steel, the type, size, shape, distribution and content of inclusions will directly affect the corrosion resistance of steel. At present, there are few means for quantitative analysis of inclusions, and they all have certain limitations. The use of ASPEX automatic scanning electron microscope to analyze inclusions is a quantitative statistical analysis of inclusions on a two-dimensional plane. Due to the random distribution of inclusions and the small detection area, it is not necessarily possible to analyze all inclusions, and the shape of inclusions is mostly irregular, resulting in different forms on different sections, so the accuracy of quantitative determination results is not good enough; for rare earth weathering steel, according to the method in the existing literature, electrolytic extraction is used, and 1-3% HCl separation method is added to dissolve carbides, and insoluble powder is collected. After diffraction and quantitative determination, it is found that rare earth sulfide and rare earth oxysulfide have been dissolved, which is not suitable for quantitative determination of rare earth sulfide inclusions and rare earth oxysulfide inclusions in rare earth weathering steel. Summary of the invention

[0003] In view of the above analysis, the present invention aims to provide a method for accurately determining rare earth sulfide and rare earth oxysulfide inclusions in rare earth weathering steel, so as to solve the problem that the prior art cannot accurately determine rare earth sulfide and rare earth oxysulfide inclusions in rare earth weathering steel.

[0004] The purpose of the present invention is mainly achieved through the following technical solutions:

[0005] The present invention provides a method for accurately determining rare earth sulfide and rare earth oxysulfide inclusions in rare earth weathering steel, comprising first electrolytic extraction of the rare earth weathering steel, then separating carbides by magnetic separation, retaining inclusions, and then using EDTA solution to separate carbides and unstable rare earth sulfide inclusions, retaining rare earth oxysulfide inclusions.

[0006] In one possible design, this includes:

[0007] S1. preparing the sample into an electrolytic sample required for electrolytic extraction;

[0008] S2, placing the electrolysis sample in an electrolysis device for electrolysis;

[0009] S3. After the electrolysis is completed, the precipitated phase powder is brushed into a beaker, and the precipitated phase powder in the beaker is poured into a watch glass. A strong magnet is used to separate and absorb the M3C in the precipitated phase powder. After repeated separation, the remaining inclusions on the watch glass are collected on a filter membrane, and the diffraction spectrum is measured by an X-ray diffractometer, and the type of inclusions is determined based on the diffraction data;

[0010] S4, wash and dry the electrolytic sample, weigh the mass as m1, electrolyze the sample according to the above step S2, collect the precipitated phase powder, and put it into the first beaker for later use;

[0011] S5. After electrolysis, the sample is washed and dried, and the mass is weighed as m2;

[0012] S6. Continue to repeat the above S3-S4 steps with the electrolysis sample, brush the precipitated phase powder into the second beaker containing EDTA solution, weigh the mass before electrolysis as m3, and the mass after electrolysis as m4;

[0013] S7, placing the second beaker in a water bath to keep warm, then taking out the second beaker, cooling it to room temperature, filtering it, cleaning the powder and the beaker, obtaining sulfur-oxygen rare earth inclusions, and placing them in the second beaker for later use;

[0014] S8, acid dissolution: add a mixture of distilled water, HCl and HNO3 to the first beaker and the second beaker respectively, heat the two beakers until the precipitated phase powder is completely dissolved, remove and cool to room temperature, and then dilute to 100 mL respectively to obtain a first analysis test solution and a second analysis test solution;

[0015] S9. Determination of element content: Use inductively coupled plasma emission spectrometer to determine the amount of rare earth sulfide and rare earth oxysulfide inclusions in the first analysis solution, and the amount of rare earth oxysulfide inclusions in the second analysis solution.

[0016] In a possible design, in S6, the preparation method of the EDTA solution includes: weighing 1 to 3 g of disodium ethylenediaminetetraacetate powder and adding it to 100 mL of distilled water, stirring continuously with a glass rod until the powder is completely dissolved, filtering the prepared solution with quantitative filter paper, and placing the solution into a second beaker for later use.

[0017] In one possible design, in S6, the EDTA solution is prepared before use.

[0018] In a possible design, in S7, the second beaker is placed in a water bath at a temperature of 50 to 70° C. and kept warm for 10 to 20 minutes.

[0019] In a possible design, in S8, the component ratio of the mixed solution of distilled water, HCl and HNO3 is controlled as follows: the volume ratio of distilled water, HCl and HNO3 is 18-22:4-6:1-2.

[0020] In a possible design, in S1, the electrolytic sample is in the shape of a rod or a sheet. When the electrolytic sample is in the shape of a rod, the diameter is 8 to 15 mm and the length is 60 to 100 mm; when the electrolytic sample is in the shape of a sheet, the length is 60 to 100 mm, the width is 15 to 25 mm, and the thickness is 3 to 7 mm.

[0021] In a possible design, in S2, components of the electrolyte include: lithium chloride, acetylacetone and methanol; wherein the ratio of lithium chloride, acetylacetone and methanol is 9-10 g: 95-100 mL: 880-900 mL.

[0022] In one possible design, in S2, the current density is controlled to be 0.03-0.05 A / cm during electrolysis. 2 .

[0023] In one possible design, in S2, a semipermeable membrane through which ions can pass is made as a capsule.

[0024] Compared with the prior art, the present invention can at least achieve the following beneficial effects:

[0025] a) The method for accurately determining rare earth sulfide and rare earth oxysulfide inclusions in rare earth weathering steel provided by the present invention first electrolytically extracts the rare earth weathering steel, then separates the carbides by magnetic separation, retains the inclusions, and then uses EDTA solution to separate the carbides and unstable rare earth sulfide inclusions, retains the rare earth oxysulfide inclusions, thereby achieving the separation of rare earth sulfide and rare earth oxysulfide inclusions in rare earth weathering steel. After the rare earth sulfide and rare earth oxysulfide inclusions are separated, the content of rare earth sulfide and rare earth oxysulfide inclusions can be accurately determined.

[0026] b) The method of the present invention is simple, easy to operate, and has little inclusion loss. It uses a strong magnet to magnetically separate M3C. The strong magnet has strong magnetism and can quickly separate M3C carbides. In addition, the strong magnet is inexpensive and can be easily purchased in the laboratory. The operation is simple and convenient.

[0027] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the written description. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are only for the purpose of illustrating the particular invention and are not to be considered as limiting the invention. The same reference symbols denote the same components throughout the accompanying drawings.

[0029] Figure 1 is a macroscopic photograph of the electrolytic sample of the present invention;

[0030] Figure 2 is a schematic diagram of placing an electrolytic sample of the present invention in an electrolytic device;

[0031] Figure 3 is a diffraction spectrum of the precipitated phase of Q235B after magnetic separation in Example 1 of the present invention;

[0032] Figure 4 This is the diffraction spectrum of the inclusions of Q235B of Example 1 of the present invention after being separated by EDTA solution;

[0033] Figure 5 is a diffraction spectrum of the precipitated phase of Q355B after magnetic separation in Example 2 of the present invention;

[0034] Figure 6 This is a diffraction spectrum of Q355B of Example 2 of the present invention after the inclusions are separated by EDTA solution.

[0035] Reference numerals

[0036] 1-beaker, 2-cathode, 3-capsule, 4-electrolysis sample. DETAILED DESCRIPTION

[0037] The present invention is described in detail in the following examples. The examples are illustrative and intended to describe the embodiments of the present invention, but are not intended to limit the scope of the present invention.

[0038] Non-metallic inclusions in steel have an important influence on the performance of steel. For weathering steel, the type, size, shape and distribution of inclusions will directly affect the corrosion resistance of steel. Therefore, it is very important to comprehensively analyze the inclusions in steel and then analyze the weathering steel and guide the process of weathering steel. Rare earth weathering steel generally contains sulfide rare earth inclusions and sulfur-oxygen rare earth inclusions. Since the influence mechanism and change of rare earth elements on inclusions in steel are not clear, it is necessary to further explore the distribution of rare earth elements in inclusions. Therefore, when studying the inclusions in rare earth weathering steel, how to separate sulfide rare earth inclusions and sulfur-oxygen rare earth inclusions, accurately determine the content of sulfide rare earth and sulfur-oxygen rare earth inclusions in rare earth weathering steel, and then analyze the presence and distribution of rare earth elements in inclusions after adding them is an urgent problem to be solved.

[0039] The present invention provides a method for accurately determining rare earth sulfide and rare earth oxysulfide inclusions in rare earth weathering steel. The method of the present invention first performs electrolytic extraction on the rare earth weathering steel, then separates carbides by magnetic separation, retains inclusions, and then uses EDTA solution to separate carbides and unstable rare earth sulfide inclusions, retains rare earth oxysulfide inclusions, thereby achieving separation of rare earth sulfide and rare earth oxysulfide inclusions in rare earth weathering steel. After the rare earth sulfide and rare earth oxysulfide inclusions are separated, the contents of the rare earth sulfide and rare earth oxysulfide inclusions can be accurately determined.

[0040] The present invention provides a method for accurately determining rare earth sulfide and rare earth oxysulfide inclusions in rare earth weathering steel, comprising:

[0041] S1. preparing the sample into an electrolytic sample required for electrolytic extraction;

[0042] S2, placing the electrolysis sample in an electrolysis device for electrolysis;

[0043] S3. After the electrolysis is completed, the precipitated phase powder is brushed into a beaker, and the precipitated phase powder in the beaker is poured into a watch glass. A strong magnet is used to separate and absorb the M3C in the precipitated phase powder. After repeated separation, the remaining inclusions on the watch glass are collected on a filter membrane by suction, and the diffraction spectrum is measured by an X-ray diffractometer, and the type of inclusions is determined based on the diffraction data;

[0044] S4, wash and dry the electrolytic sample, weigh the mass as m1, electrolyze the sample according to the above step S2, collect the precipitated phase powder, and put it into the first beaker for later use;

[0045] S5. After the electrolysis, the sample is washed and dried, and the mass is weighed as m2. The amount of sample dissolved during the electrolysis process is m2-m1;

[0046] S6. Continue to repeat the above S3-S4 steps with the electrolysis sample, brush the precipitated phase powder into the second beaker containing EDTA solution, weigh the mass before electrolysis as m3, and the mass after electrolysis as m4; the amount of sample dissolved during the electrolysis process is m3-m4;

[0047] S7, placing the second beaker in a water bath at a temperature of 50-70°C and keeping it warm for 10-20 minutes, taking out the second beaker, cooling it to room temperature, filtering it, cleaning the powder and the second beaker, obtaining sulfur-oxygen rare earth inclusions, and placing them in the second beaker for later use;

[0048] S8, acid dissolution: add a mixture of distilled water, HCl and HNO3 to the first beaker and the second beaker respectively, heat the two beakers until the precipitated phase powder is completely dissolved, remove and cool to room temperature, and then dilute to 100 mL respectively to obtain a first analysis test solution and a second analysis test solution;

[0049] S9. Determination of element content: Use inductively coupled plasma emission spectrometry (ICP) to determine the amount of rare earth sulfide and rare earth oxysulfide inclusions in the first analysis solution, and the amount of rare earth oxysulfide inclusions in the second analysis solution.

[0050] Specifically, in the above S1, the electrolysis sample can be in the shape of a rod or a sheet. Considering that the size of the electrolysis sample is too large, the sample is too long, or too thick, it is not convenient to suspend the electrolysis, and the total current cannot be too large when electrolyzing with an organic solution, so as to avoid the electrolyte temperature rising during the electrolysis process, resulting in the loss of some inclusions; if the sample is too small, the total current is small, and the electrolysis time required to collect a sufficient amount of inclusion powder is too long, and the inclusions may be lost. Therefore, the size of the electrolysis sample is controlled as follows: when it is rod-shaped, the diameter is 8-15mm and the length is 60-100mm; when it is sheet-shaped, the length is 60-100mm, the width is 15-25mm, and the thickness is 3-7mm.

[0051] Specifically, in the above S1, if Figure 1 As shown, a groove of 2 to 4 mm is engraved at one end of the electrolytic sample for tying copper wire, and the electrolytic sample needs to be suspended for electrolysis.

[0052] Specifically, in the above S2, the components of the electrolyte include: lithium chloride, acetylacetone and methanol; wherein the ratio of lithium chloride, acetylacetone and methanol is 9-10g:95-100mL:880-900mL, preferably 10g:100mL:900mL. In the electrolyte, lithium chloride is used as a conductive ion, acetylacetone is used as a complexing agent to complex with metal ions in the matrix that enters the electrolyte after electrolysis, and methanol is used as a solvent. This electrolyte has a good electrolysis effect, and the surface of the sample is smooth after electrolysis without pitting.

[0053] Specifically, in the above S2, the preparation method of the electrolyte includes: weighing lithium chloride and adding it to methanol, stirring and dissolving it, then adding acetylacetone, stirring evenly and then putting it into a reagent bottle. In order to ensure that the precipitated phase is completely retained during electrolysis and to minimize the volatilization of the electrolyte, low-temperature electrolysis below -5°C is required, so the reagent bottle is placed in the freezer of a refrigerator for more than 2 hours.

[0054] It should be noted that in the above S2, in the preparation method of the electrolyte, lithium chloride is first added to methanol, stirred to dissolve, and then acetylacetone is added, so that the lithium chloride can be quickly and fully dissolved.

[0055] It should be noted that in the above S2, if the current density during electrolysis is too large, some inclusions (such as sulfide inclusions) may be electrolyzed together with the matrix, and some inclusions cannot be retained; if the current density is too small, the matrix cannot be completely activated and dissolved; therefore, the current density is controlled to be 0.03-0.05A / cm 2, the total current is generally controlled at 0.6-0.7A. According to the total current and current density during electrolysis, calculate the surface area of ​​the part that needs electrolysis and the length of the sample that needs electrolysis. The calculation formula for the surface area S of the part that needs electrolysis is: S = total current / current density. Stick the sample that is not electrolyzed with insulating tape, leaving only the surface of the part that needs electrolysis exposed. Controlling the surface area of ​​the part that needs electrolysis is mainly to control the current density during the electrolysis process to be maintained at 0.03-0.05A / cm 2 , ensuring that the matrix is ​​completely dissolved and the inclusions are retained.

[0056] It should be noted that in the above S2, considering that the lithium chloride + acetylacetone methanol solution may precipitate complexes after a long electrolysis time, and the complexes may contaminate the precipitated phase, a semipermeable membrane through which ions can pass may be prepared as a capsule.

[0057] Specifically, in the above S2, the method for making capsules includes: weighing cellulose acetate and dissolving it in acetone, and after the cellulose acetate is completely dissolved, pouring the mixture on the mold for making capsules, drying it, and soaking it in water for 2 to 5 minutes, peeling the capsules from the mold, and soaking them in distilled water for later use. The ratio of cellulose acetate to acetone is 45 to 50 g: 500 mL. During the electrolysis process, the capsule allows anions and cations to pass normally, while the precipitated phase powder and the like falling from the electrolysis sample cannot pass through and are collected in the capsule.

[0058] Specifically, in the above S2, if Figure 2 As shown, the electrolysis sample is placed in the electrolysis device including:

[0059] S201, a beaker 1 with a capacity of 500 mL is used as an electrolytic cell, a sheet or cylindrical stainless steel is placed in the beaker 1 as a cathode 2, and then a capsule 3 is placed, and the filtered and low-temperature frozen electrolyte is placed in the capsule, and then the beaker with the electrolyte and the cathode is placed on an electrolysis rack, and the electrolysis sample 4 is suspended in the electrolyte so that the part of the electrolysis sample that needs to be electrolyzed is completely immersed in the electrolyte;

[0060] S202, placing the electrolysis rack in the freezer compartment of a refrigerator, connecting the electrolysis power supply, connecting the negative electrode to the cathode, and connecting the positive electrode to the electrolysis sample, and after power is turned on, electrolysis is performed.

[0061] Considering that if the electrolysis time is too long, the resistance of the electrolyte will increase, and the temperature will rise during the electrolysis process, which is not conducive to completely retaining the unstable precipitated phase. Moreover, if the time is too long, the content of lithium chloride and acetylacetone in the electrolyte will change, affecting the electrolysis effect. If it is too short, the amount of collected precipitated phase powder is too small, the amount of collected inclusions is too small, it is not convenient to observe, and the statistical effect is not good enough. Therefore, in the above S2, the electrolysis time is controlled to be 3 to 4 hours. During electrolysis, the matrix of rare earth weathering steel is dissolved, and the precipitated phase is retained as insoluble residue powder.

[0062] Specifically, in the above S3, the precipitated phase powder mainly includes inclusions and M3C type carbides; the inclusions mainly include rare earth sulfide and rare earth oxysulfide inclusions. Since the inclusions are non-ferromagnetic materials and the M3C type carbides are ferromagnetic materials, a strong magnet can be used to separate the M3C in the precipitated phase powder. The strong magnet has strong magnetism and can quickly separate the M3C type carbides. In addition, the strong magnet is inexpensive and can be easily purchased in the laboratory. The operation is simple and convenient.

[0063] Specifically, the specific process of the above S3 includes:

[0064] S301. After the electrolysis is completed, turn off the power supply, take out the electrolyzed sample and soak it twice with 5-10g / L citric acid ethanol solution, and then soak it twice with anhydrous ethanol solution, clean the ions in the electrolyte attached to the sample surface, and then directly brush the precipitated phase powder that has not fallen off the sample surface with anhydrous ethanol into a beaker for standby use; if the powder is easy to fall off, the precipitated phase powder that falls into the capsule can be filtered with an imported microporous filter membrane, and washed twice with ethanol washing solution containing 10g / L citric acid and anhydrous ethanol respectively, and then the powder on the filter membrane is brushed into the beaker containing the precipitated phase powder;

[0065] S302, placing the beaker in ultrasonic waves to disperse the aggregated precipitated phase, and taking out the beaker after the ultrasonic waves are finished;

[0066] S303, take a clean watch glass (Φ100-120mm), pour the precipitated phase powder in the beaker into the watch glass, rotate in the same direction to make the precipitated phase powder concentrate in the center of the watch glass, use a strong magnet to absorb the M3C phase, wipe the M3C phase on the surface of the strong magnet with a clean paper towel, and repeatedly absorb the M3C phase until the M3C phase is separated cleanly;

[0067] S304, collecting the inclusions in the watch glass on a Φ25 mm filter membrane, measuring the diffraction spectrum using an X-ray diffractometer, and determining the type of inclusions based on the diffraction data.

[0068] Specifically, in the above S303, considering that the volume of the watch glass is relatively small, when the solution is relatively large, it cannot be poured in at one time, therefore, the powder in the beaker is poured into the watch glass in batches, that is, a portion is poured in first, and the M3C in the precipitated phase powder is separated with a strong magnet, and after repeated separation, another portion is poured in and the separation is continued.

[0069] Specifically, in the above S6, the preparation method of the EDTA solution includes: weighing 1 to 3 g of disodium ethylenediaminetetraacetate (EDTA) powder and adding it to 100 mL of distilled water, stirring continuously with a glass rod until the powder is completely dissolved, filtering the prepared EDTA solution with quantitative filter paper, and placing it in a second beaker for later use.

[0070] It should be noted that EDTA solution should not be left for too long. It is best to prepare it immediately before use to prevent it from becoming ineffective over time.

[0071] Specifically, in the above S7, after the second beaker is placed in a water bath at a temperature of 50 to 70°C for insulation, carbides and unstable rare earth sulfide inclusions can be dissolved, while sulfur-oxygen rare earth inclusions with slightly higher stability are retained. Considering that if the water bath temperature is too high and the insulation time is too long, sulfur-oxygen rare earth inclusions may be affected and partially dissolved; if the water bath temperature is too low and the insulation time is too short, carbides and unstable rare earth sulfide inclusions may not be completely dissolved, therefore, the second beaker is placed in a water bath at a temperature of 50 to 70°C for insulation for 10 to 20 minutes.

[0072] Specifically, in the above S8, if the amount of HCl and HNO3 is too large, the acidity is too high, which does not meet the sampling requirements of the ICP instrument and is relatively wasteful; if the amount of HCl and HNO3 is too small, the powder may not be completely dissolved; the acid concentration should be reduced as much as possible on the basis of ensuring that the powder can be completely dissolved. Therefore, the component distribution ratio of the mixed solution of distilled water, HCl and HNO3 is controlled to be: the volume ratio of distilled water, HCl and HNO3 is: 18-22: 4-6: 1-2.

[0073] Specifically, in the above S8, HCl is commercially available hydrochloric acid with a mass concentration of 36% to 38%; HNO3 is commercially available nitric acid with a mass concentration of 65% to 68%.

[0074] Specifically, in the above S8, the two beakers are placed on a hot plate for heating.

[0075] Specifically, in the above S9, the process of determining the element content includes: taking 0mL, 1mL, 3mL, 5mL, and 10.00mL of lanthanum and cerium standard solutions with a concentration of 10μg / mL into a 100mL volumetric flask, adding 5ml HCl and 1mL HNO3, diluting to the scale with water, using yttrium as the internal standard element, and using an inductively coupled plasma emission spectrometer (ICP) to determine the total amount of rare earth elements in the rare earth sulfide and rare earth oxysulfide inclusions in the first beaker, and the rare earth element content in the rare earth oxysulfide inclusions in the second beaker. Thus, the content of rare earth sulfide inclusions and rare earth oxysulfide inclusions is obtained.

[0076] Compared with the prior art, the method of the present invention first performs electrolytic extraction on rare earth weathering steel Q235B, then separates carbides by magnetic separation, retains inclusions, and then uses EDTA solution to separate carbides and unstable rare earth sulfide inclusions, retains sulfur-oxygen rare earth inclusions, thereby achieving the separation of rare earth sulfide and sulfur-oxygen rare earth inclusions in rare earth weathering steel. After the rare earth sulfide and sulfur-oxygen rare earth inclusions are separated, the contents of rare earth sulfide and sulfur-oxygen rare earth inclusions can be accurately determined.

[0077] The method of the invention is simple, easy to operate, and has little inclusion loss. A strong magnet is used to separate M3C by magnetic separation. The strong magnet has strong magnetism and can quickly separate M3C carbides. In addition, the strong magnet is inexpensive and can be easily purchased in laboratories. The operation is simple and convenient.

[0078] The method of the present invention for accurately determining rare earth sulfide and rare earth oxysulfide inclusions in rare earth weathering steel will be demonstrated below with specific examples.

[0079] Example 1

[0080] This embodiment provides a method for accurately determining rare earth sulfide and rare earth oxysulfide inclusions in rare earth weathering steel. The method is used to electrolytically extract rare earth weathering steel Q235B, separate carbides by magnetic separation, retain inclusions, and perform XRD diffraction on the retained inclusions. The diffraction results are as follows: Figure 3 As shown; the rare earth weathering steel Q235B was electrolytically extracted again, and the carbides and unstable rare earth sulfide inclusions were separated by EDTA solution, and the sulfur oxide rare earth inclusions were retained. The retained inclusions were subjected to XRD diffraction, and the diffraction results were shown as follows Figure 4 shown.

[0081] The method was used to perform electrolytic extraction, acid dissolution, and ICP determination of the rare earth element content in inclusions on Q235B rare earth weathering steel samples, as well as electrolytic extraction, EDTA separation, acid dissolution, and ICP determination of the rare earth element content in sulfur-oxygen rare earth inclusions. The determination results are shown in Table 1.

[0082] Specific methods include:

[0083] (1) The Q235B steel sample was prepared into a Φ10*80mm rod, with a 2mm groove engraved on one end for tying copper wire and hanging the sample for electrolysis.

[0084] (2) Prepare the electrolyte: Weigh 10g of lithium chloride and add it to 900mL of methanol. Stir to dissolve it, then add 100mL of acetylacetone, stir evenly and put it into a reagent bottle. In order to ensure that the precipitated phase is completely retained, low-temperature electrolysis is required below -5°C, so the reagent bottle is placed in the freezer for 2h.

[0085] (3) Capsule preparation: Weigh 45 g of cellulose acetate and dissolve it in 500 mL of acetone. After it is completely dissolved, pour the capsule liquid onto the mold for capsule preparation. After drying, soak it in water for a while. Peel the capsule from the capsule cup and soak it in distilled water for later use.

[0086] (4) Use a 500 mL beaker as an electrolytic cell, put a stainless steel cylinder as the cathode, place a capsule in the middle of the cathode, pour in the low-temperature frozen electrolyte, and then place the beaker with the electrolyte and cathode on the electrolysis rack. Hang the sample to be electrolyzed in the beaker so that the part of the sample to be electrolyzed is completely immersed in the electrolyte. Put the electrolysis rack in the freezer of the refrigerator, connect the power supply for electrolysis, connect the negative electrode to the cathode, and the positive electrode to the sample. After power is turned on, adjust the total current to 0.6A and electrolyze for 3 to 4 hours.

[0087] (5) After the electrolysis is completed, turn off the power supply, take out the electrolyzed sample and soak it twice in 8 g / L citric acid ethanol solution, and then soak it twice in anhydrous ethanol solution. After cleaning the ions in the electrolyte attached to the sample surface, the precipitated phase powder that has not fallen off the sample surface is directly brushed into a beaker with anhydrous ethanol for later use. The precipitated phase powder that falls into the capsule is filtered with an imported microporous filter membrane, and washed twice with an ethanol washing solution containing 10 g / L citric acid and anhydrous ethanol respectively, and then the powder on the filter membrane is brushed into the beaker containing the precipitated phase powder.

[0088] (6) Take a clean watch glass (Φ120 mm), pour the precipitated phase powder into the watch glass, rotate it in the same direction to concentrate the precipitated phase powder in the center of the watch glass, use a strong magnet to absorb the M3C phase, wipe the carbides on the surface of the strong magnet with a clean paper towel, and repeatedly absorb the carbides until the carbides are separated. Filter the inclusions in the center of the watch glass onto a Φ25 mm filter membrane, use an X-ray diffractometer to measure the diffraction spectrum, and determine the type of inclusions based on the diffraction data.

[0089] (7) In order to dissolve carbides and unstable rare earth sulfide inclusions and retain the slightly more stable rare earth oxysulfide inclusions, disodium ethylenediaminetetraacetate (EDTA) is used for separation. Preparation method of EDTA solution: weigh 2g disodium ethylenediaminetetraacetate (EDTA) powder and add it to 100mL distilled water. Stir continuously with a glass rod until the powder is completely dissolved. Filter the prepared EDTA solution with a vacuum filtration device and put it into a beaker for later use.

[0090] (8) Repeat the above electrolysis steps, brush the precipitated phase powder after electrolytic extraction into a beaker filled with EDTA solution, put the beaker into a water bath at 60°C and keep it warm for 15 min, take out the beaker, cool it to room temperature, filter it and collect it on a Φ25 mm filter membrane, use an X-ray diffractometer to measure the diffraction spectrum, and determine the type of inclusions after separation based on the diffraction data.

[0091] (9) Wash and dry the sample, weigh the mass m1, electrolyze the sample according to the above steps (4)-(5), collect the precipitated phase powder, obtain the total precipitated phase powder, put it into the first beaker for later use, wash the electrolyzed steel sample, and fully dry the steel sample in a dryer, weighing the mass m2. The amount of sample dissolved during the electrolysis process is m2-m1.

[0092] (10) Repeat the above step (9) with the same steel sample, brush the precipitated phase powder into the second beaker containing EDTA solution, weigh the mass before electrolysis m3, and the mass after electrolysis m4. The amount of sample dissolved during the electrolysis process is m3-m4.

[0093] (11) Acid dissolution: Add about 20 mL of distilled water, 5 mL of HCl, and 1 mL of HNO3 to the first beaker and the second beaker, respectively. Place the two beakers on a hot plate and heat until the precipitated phase powder is completely dissolved. Remove the beakers, cool them to room temperature, and then adjust the volumes to 100 mL to obtain the first analysis solution and the second analysis solution.

[0094] (12) Yttrium is used as an internal standard element, the amount of sample dissolved during the electrolysis process is input, and an inductively coupled plasma emission spectrometer (ICP) is used to determine the total amount of rare earth elements in the first analysis solution and the rare earth element content in the sulfur-oxygen rare earth inclusions in the second analysis solution.

[0095] The results show that the rare earth inclusion types in Q235B are mainly rare earth sulfide Ce2S3 and rare earth oxysulfide (RE)2O2S; after EDTA separation, the unstable rare earth sulfide inclusions are dissolved and the rare earth oxysulfide inclusions (RE)2O2S in the steel are retained.

[0096] Example 2

[0097] This embodiment provides a method for accurately determining rare earth sulfide and rare earth oxysulfide inclusions in rare earth weathering steel. The method is used to electrolytically extract rare earth weathering steel Q355B, separate carbides by magnetic separation, retain inclusions, and perform XRD diffraction on the retained inclusions. The diffraction results are as follows: Figure 5 As shown; the rare earth weathering steel Q355B was electrolytically extracted again, and the carbides and unstable rare earth sulfide inclusions were separated by EDTA solution, and the sulfur oxide rare earth inclusions were retained. The retained inclusions were subjected to XRD diffraction, and the diffraction results were shown as follows Figure 6 shown.

[0098] The method was used to perform electrolytic extraction, acid dissolution, and ICP determination of the rare earth element content in inclusions on Q355B rare earth weathering steel samples, as well as electrolytic extraction, EDTA separation, acid dissolution, and ICP determination of the rare earth element content in sulfur-oxygen rare earth inclusions. The determination results are shown in Table 1.

[0099] The specific method is basically the same as that of the above-mentioned embodiment 1, and the different parameters are as follows:

[0100] (5), the sample after electrolysis was taken out and soaked twice in 6 g / L citric acid ethanol solution.

[0101] (7), weigh 3 g of disodium ethylenediaminetetraacetate (EDTA) powder and add it to 100 mL of distilled water.

[0102] (8) The beaker was placed in a water bath at 55°C for 18 min.

[0103] The results show that after electrolytic extraction and magnetic separation, the rare earth inclusion types of Q355B are mainly rare earth sulfide Ce2S3 and rare earth oxysulfide (RE)2O2S; after EDTA separation, the unstable rare earth sulfide inclusions are dissolved and the rare earth oxysulfide inclusions (RE)2O2S in the steel are retained.

[0104] Table 1 Measurement results of Examples 1-2

[0105]

[0106] It can be seen from Table 1 that the present method can be used to accurately determine the content of rare earth elements in sulfide rare earth inclusions and sulfur-oxygen rare earth inclusions in rare earth weathering steel.

[0107] It should be noted that the above preparation method is the best solution obtained by the inventors after long-term and in-depth experimental research. Here, the inventors provide some solutions with poor effects during the research process as comparative examples.

[0108] Comparative Example 1

[0109] This comparative example provides a method for separating sulfide rare earth inclusions and sulfur-oxygen rare earth inclusions in rare earth weathering steel. The method is used to separate, acid-dissolve, and fix the volume of the precipitated phase powder after Q235B electrolytic extraction, and the rare earth element content is determined by ICP.

[0110] The separation test method is the same as the overall steps of Example 1, except that 1-2% hydrochloric acid is used for separation in (7) and (8).

[0111] The present method was used to electrolytically extract the rare earth weathering steel Q235B same as that in Example 1, separate the inclusions, and determine the rare earth element content by ICP after acid dissolution and constant volume. The determination results are shown in Table 2. The results show that when this method is used for separation, sulfur-oxygen rare earth inclusions are also dissolved, and the rare earth element content in the sulfur-oxygen rare earth inclusions cannot be determined.

[0112] Comparative Example 2

[0113] This comparative example provides a method for separating sulfide rare earth inclusions and sulfur-oxygen rare earth inclusions in rare earth weathering steel. The method is used to separate, acid-dissolve, and fix the volume of the precipitated phase powder after Q235B electrolytic extraction, and the rare earth element content is determined by ICP.

[0114] The separation test method is the same as the overall steps of Example 1, except that 1-2% nitric acid is used for separation in (7) and (8).

[0115] The present method is used to electrolytically extract the rare earth weathering steel Q235B same as Example 1, separate the inclusions, and use ICP to determine the rare earth element content after acid dissolution and constant volume. The measurement results are shown in Table 2. The results show that when this method is used for separation, most of the sulfur-oxygen rare earth inclusions are also dissolved, and the rare earth element content in the sulfur-oxygen rare earth inclusions cannot be accurately determined.

[0116] Table 2 Comparative Example Measurement Results

[0117]

[0118] By comparing the above embodiments and comparative examples, it can be seen that the method of the present invention can accurately determine the content of rare earth elements in sulfide rare earth inclusions and sulfur-oxygen rare earth inclusions in rare earth weathering steel, thereby obtaining the content of sulfide rare earth inclusions and sulfur-oxygen rare earth inclusions.

[0119] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for accurately determining rare earth sulfide and rare earth oxysulfide inclusions in rare earth weathering steel, characterized in that: The method comprises: S1. preparing the sample into an electrolytic sample required for electrolytic extraction; S2, placing the electrolysis sample in an electrolysis device for electrolysis; S3. After the electrolysis is completed, the precipitated phase powder is brushed into a beaker, and the precipitated phase powder in the beaker is poured into a watch glass. A strong magnet is used to separate and absorb the M3C type carbide in the precipitated phase powder. After repeated separation, the remaining inclusions on the watch glass are collected on a filter membrane, and the diffraction spectrum is measured by an X-ray diffractometer, and the type of inclusions is determined according to the diffraction data; S4, further wash and dry the electrolytic sample, weigh the mass to be m1, electrolyze the sample according to step S2, collect the precipitated phase powder, and put it into the first beaker for later use; S5. After electrolysis, the sample is washed and dried, and the mass is weighed as m2; S6. Continue to repeat step S2 for the electrolysis sample, brush the precipitated phase powder into the second beaker containing EDTA solution, weigh the mass before electrolysis as m3, and the mass after electrolysis as m4; S7, placing the second beaker in a water bath to keep warm, then taking out the second beaker, cooling it to room temperature, filtering it, cleaning the powder and the beaker, obtaining sulfur-oxygen rare earth inclusions, and placing them in the second beaker for later use; S8, acid dissolution: add a mixture of distilled water, HCl and HNO3 to the first beaker and the second beaker respectively, heat the two beakers until the precipitated phase powder is completely dissolved, remove and cool to room temperature, and then dilute to 100 mL respectively to obtain a first analysis test solution and a second analysis test solution; S9. Determination of element content: using an inductively coupled plasma emission spectrometer to determine the amount of rare earth sulfide and rare earth oxysulfide inclusions in the first analysis solution, and the amount of rare earth oxysulfide inclusions in the second analysis solution; In S6, the preparation method of the EDTA solution includes: weighing 1-3 g of disodium ethylenediaminetetraacetate powder and adding it to 100 mL of distilled water, stirring continuously with a glass rod until the powder is completely dissolved, filtering the prepared solution with quantitative filter paper, and placing the solution into a second beaker for later use.

2. The method according to claim 1, characterized in that In S6, the EDTA solution is prepared and used immediately before use.

3. The method according to claim 1, characterized in that In S7, the second beaker is placed in a water bath at a temperature of 50-70° C. and kept warm for 10-20 minutes.

4. The method according to claim 1, characterized in that: In the step S8, the component ratio of the mixed solution of distilled water, HCl and HNO3 is controlled to be: the volume ratio of distilled water, HCl and HNO3 is: 18-22:4-6:1-2.

5. The method according to claim 1, characterized in that: In S1, the electrolytic sample is in the shape of a rod or a sheet. When the electrolytic sample is in the shape of a rod, the diameter is 8-15 mm and the length is 60-100 mm; when the electrolytic sample is in the shape of a sheet, the length is 60-100 mm, the width is 15-25 mm, and the thickness is 3-7 mm.

6. The method according to claim 1, characterized in that In S2, components of the electrolyte include: lithium chloride, acetylacetone and methanol; wherein the ratio of lithium chloride, acetylacetone and methanol is 9~10g:95~100mL:880~900mL.

7. The method according to claim 1, characterized in that In S2, the current density is controlled to be 0.03~0.05A / cm during electrolysis. 2 .

8. The method according to any one of claims 1 to 7, characterized in that: In S2, a semipermeable membrane through which ions can pass is prepared as a capsule.

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