Methods for detecting Al2O3 in electroslag premelted slag

Abstract

The application discloses a method for detecting Al2O3 in electroslag pre-melted slag, and belongs to the technical field of chemical analysis. The method is used for effectively eliminating the interference of calcium fluoride and accurately detecting the content of free Al2O3 in the electroslag pre-melted slag, and comprises the following steps: total aluminum determination; calcium aluminate aluminum determination: a mixed solution of concentrated hydrochloric acid and water with a volume ratio of 1±0.1:1±0.1 is used as a leaching solution, electroslag pre-melted slag and the leaching solution are kept in a micro-boiling state with a mass-volume ratio of 1g:350-400mL for 45-75s, and then EDTA titration is used to determine aluminum; and finally, free Al2O3 is calculated by using a subtraction method. The application realizes accurate distinction between free Al2O3 and calcium aluminate in the electroslag pre-melted slag by strictly controlling leaching conditions, has strong anti-fluorine interference ability, and has high detection precision and accuracy.

Description

Technical Field

[0001] This invention belongs to the field of chemical analysis technology, specifically relating to a method for detecting Al2O3 in electroslag premelted slag. Background Technology

[0002] Electroslag remelting is a crucial process in the production of high-quality special steel. The removal of inclusions, control of alloy element burn-off, and optimization of ingot solidification structure are all closely related to the physicochemical properties of the slag system. Electroslag remelting slag is an alkaline melt based on calcium fluoride (CaF2), containing calcium oxide (CaO), aluminum oxide (Al2O3), magnesium oxide (MgO), and silicon dioxide (SiO2), and functions to desulfurize, dephosphorize, and remove non-metallic inclusions. Aluminum oxide is a key component of electroslag pre-melted slag, and its content directly affects the slag's electrical conductivity, desulfurization effect, and remelting stability. However, because Al2O3 is a typical high-melting-point phase, it is not easily melted during the electroslag formation process. When slag formation is insufficient, Al2O3 easily enters the steel, forming inclusions. Furthermore, some electroslag pre-melted slag products have excessively high Al2O3 content due to insufficient pre-melting, making the originally easily meltable slag difficult to melt. Therefore, the rapid and accurate determination of Al2O3 content in electroslag premelted slag is of great significance for the study of slag material systems and electroslag remelting technology.

[0003] However, the forms in which aluminum exists in electroslag pre-melting slag are quite complex, mainly including: free aluminum oxide (α-Al2O3), which exists in the form of corundum, has a high melting point, and is not easily melted; and bound aluminum (calcium aluminate), which may react with CaO during slag production to form calcium aluminate (such as CaO·Al2O3, 3CaO·Al2O3, etc.) or calcium aluminate fluoride (such as 3CaO·3Al2O3·CaF2). This portion of aluminum exists in a bound form, and its metallurgical properties differ from those of free Al2O3; it has a lower melting point and is more easily melted.

[0004] The main technical difficulties in the composition analysis of electroslag slag are as follows: (1) Difficulty in phase differentiation: Conventional full-volume analysis methods (such as X-ray fluorescence spectrometry, inductively coupled plasma atomic emission spectrometry, etc.) can only measure the total amount of aluminum, and cannot distinguish between "bound aluminum" (aluminum in calcium aluminate) and "free aluminum oxide". Measuring only the total aluminum content cannot meet the precise requirements of process control; (2) Limitations of XRD method: Although X-ray diffraction (XRD) can qualitatively analyze phases, the equipment is expensive and the operation threshold is high. For phases with low content or poor crystallinity, quantitative analysis is difficult, which makes it difficult to meet the rapid detection requirements of the production site; (3) Fluoride ion interference: Electroslag pre-melted slag generally contains a high proportion of CaF2 (usually 40%~70%), and fluorite will decompose and release fluoride ions (CaF2+ 2H2O).+ → Ca 2+ + 2HF), fluoride ions have a very strong complexing ability with aluminum, which may change the dissolution behavior of calcium aluminate or Al2O3, making the measurement results inaccurate.

[0005] CN103344636A discloses a method for determining metallic aluminum and aluminum oxide in steel slag, comprising: Step 1: Dissolving steel slag with hydrochloric acid, adding solid sodium hydroxide to the filtered solution, aluminum forms sodium aluminate, and other metal ions precipitate as hydroxides and are separated; adding excess EDTA standard solution to a slightly acidic solution, then boiling in the presence of acetic acid-ammonium acetate to form a complex with all aluminum and EDTA, using PAN as an indicator, back-tipping excess EDTA with copper sulfate standard solution until a purple-red or blue endpoint is reached, and calculating the mass fraction of metallic aluminum; Step 2: After filtering the remaining residue in Step 1, passing it through ashing filter paper, melting the sample with a mixed solvent, leaching with hydrochloric acid, separating with solid sodium hydroxide, adding excess EDTA standard solution, then boiling in the presence of acetic acid-ammonium acetate to form a complex with all aluminum and EDTA, using PAN as an indicator, back-tipping excess EDTA with copper sulfate standard solution, and calculating the mass fraction of aluminum oxide. However, this method is not suitable for the quantitative detection of free Al2O3 in electroslag pre-melted slag.

[0006] CN106290352A discloses a method for determining the aluminum oxide content in carbide slag, comprising the following steps: (1) Dissolution: First, the carbide slag sample is dissolved in hydrochloric acid, and then the insoluble matter is treated with a mixed flux to extract and dissolve it. The mixed flux is prepared by finely grinding and mixing 2 parts of anhydrous sodium carbonate and 1 part of boric acid; (2) Separation of precipitate: Hexamethylenetetramine is used to separate aluminum and iron into hydroxide precipitates; (3) Titration: The precipitate is dissolved in acid, and excess EDTA is added to completely complex with aluminum. Then, using xylenol orange as an indicator, excess EDTA is titrated with zinc standard titration solution. Sodium fluoride is then used to replace the EDTA complexed with aluminum, and titration is performed with zinc standard titration solution. This method is also not applicable to the quantitative detection of free Al2O3 in pre-melted electroslag slag.

[0007] CN104076035A discloses a method for determining the calcium oxide content in pre-melted slag, comprising: (a) mixing the pre-melted slag with water, adding glacial acetic acid to the mixture, heating the mixture to completely dissolve the calcium oxide and calcium aluminate in the pre-melted slag, and then adding methyl red solution dropwise, wherein the ratio of the volume of water in milliliters to the weight of the pre-melted slag in grams is 320-400, and the ratio of the volume of glacial acetic acid in milliliters to the weight of the pre-melted slag in grams is 20-30; (b) adding a 500 g / L ammonium nitrate solution to the mixture, heating the mixture to boiling, and then adding a 0.9 g / mL ammonia solution to the mixture. (c) Heat the mixture to boiling and maintain for 15-20 minutes, wherein the ratio of ammonium nitrate solution (mL) to pre-melted slag (g) is 150-180, and the ratio of ammonia solution (mL) to pre-melted slag (g) is 40-60; (d) Add 0.9 g / mL ammonia solution to the mixture and let it stand at room temperature for 4-5 hours, then add water to the mixture and filter to obtain a filtrate, wherein the ratio of ammonia solution (mL) to pre-melted slag (g) is 20-40; (e) Determine the calcium content in the filtrate using EDTA titration, thereby obtaining the calcium oxide content in the pre-melted slag. However, this method cannot achieve quantitative detection of free Al2O3 in electroslag pre-melted slag.

[0008] To address the aforementioned issues, it is necessary to develop a method that can effectively eliminate the interference of calcium fluoride and accurately achieve quantitative detection of free Al2O3 in electroslag premelted slag. Summary of the Invention

[0009] This invention provides an indirect method for determining total aluminum by existing methods such as XRF or chemical titration, and then relying on the difference in dissolution kinetic rates of different phases in dilute acid to achieve selective phase separation, and calculating free aluminum oxide by difference subtraction. This method can effectively eliminate the interference of calcium fluoride and accurately realize the quantitative detection of free Al2O3 in electroslag premelted slag.

[0010] To achieve the above objectives, the present invention provides a method for detecting Al2O3 in electroslag premelted slag, comprising the following steps:

[0011] A. Total aluminum determination: The total aluminum content w(Al-total) in the electroslag premelted slag was obtained;

[0012] B. Determination of aluminum in calcium aluminate:

[0013] B1. Selective leaching: After crushing and pulverizing the electroslag pre-melted slag, it is mixed with the leaching solution at a mass-to-volume ratio of 1g:350~400mL (this amount is only for leaching and does not include subsequent washing, etc.), and then leached while maintaining a gentle boil (about 93~97℃) for 45~75s. After leaching, it is filtered while hot, washed, cooled, and then diluted to a fixed volume and shaken to obtain an aluminum-containing solution. The leaching solution is a mixed solution of concentrated hydrochloric acid and water at a volume ratio of 1±0.1:1±0.1.

[0014] B2. EDTA Titration for Aluminum Determination: Mix the aluminum-containing solution with excess EDTA standard solution, heat to boiling (generally 2-3 min) to ensure complete aluminum complexation; cool, adjust the pH to 5-6, and add xylenol orange indicator (generally 3-4 drops); titrate with zinc standard solution until the solution changes from yellow to orange-red; add potassium fluoride aqueous solution, heat to boiling (generally 2-3 min) to release EDTA from the Al-EDTA complex by fluoride ions, and cool; add more xylenol orange indicator (generally 2-3 drops), and titrate with zinc standard solution until the solution changes from yellow to orange-red as the endpoint. Record the volume of zinc standard solution consumed and calculate the aluminum content w(Al-CA) in the form of calcium aluminate in the electroslag pre-melted slag.

[0015] C. Calculation of free Al2O3 by difference: The aluminum content of Al2O3 in electroslag pre-melted slag, w(Al-Al2O3), is: w(Al-Al2O3)=w(Al-total)-w(Al-CA). After conversion, the Al2O3 content in the pre-melted slag sample is obtained.

[0016] In the above-mentioned method for detecting Al2O3 in electroslag pre-melted slag, step A involves determining the total aluminum content using either XRF or titration. The XRF method involves grinding and pressing the electroslag pre-melted slag into a pellet, and then using X-ray fluorescence spectroscopy to determine the total aluminum content w(Al-total) in the electroslag pre-melted slag. The titration method involves using a mixed solvent of sodium carbonate and boric acid to melt the electroslag pre-melted slag at 905°C. After leaching with hydrochloric acid, calcium and magnesium are separated using hexamethylenetetramine. The precipitate is dissolved in acid, and then aluminum is separated from titanium and iron using a strong alkali. The filtrate is then back-titrated with copper sulfate to determine the total aluminum content w(Al-total) in the electroslag pre-melted slag.

[0017] In this invention, total aluminum can be determined using methods commonly found in the art, such as XRF or titration. In the XRF method, the sample is ground to a fineness passing through a 200-mesh sieve, the tablet pressure is 20-30 tons, the holding time is 20-30 seconds, X-ray fluorescence spectroscopy is used, and the standard curve method or theoretical α coefficient method is employed. The matrix of the standard sample and the sample to be tested are matched, and the XRF determination result is expressed in Al elemental form, i.e., the mass fraction of Al element is directly read. This invention can also use other methods to determine the total aluminum content, as long as the results are accurate.

[0018] In the method for detecting Al2O3 in electroslag premelted slag, step B1 involves crushing and pulverizing the electroslag premelted slag, passing it through a 200-mesh sieve, and collecting the material passing through the sieve.

[0019] In the method for detecting Al2O3 in electroslag premelted slag described above, in step B1, the amount of electroslag premelted slag after crushing and pulverizing is 0.25~0.5g, and the amount of leaching solution is 95~190mL. This invention strictly controls the leaching conditions, allowing calcium aluminate in the sample to selectively dissolve into the solution, while aluminum oxide remains in the solid phase, ensuring the accuracy of the results.

[0020] In the above method for detecting Al2O3 in electroslag premelted slag, step B1 involves washing the container and residue 3-4 times with leachate, followed by washing with hot water until the washing solution is free of chloride ions.

[0021] In the method for detecting Al2O3 in electroslag premelted slag, in step B2, the concentration of the EDTA standard solution is 0.03~0.10mol / L, and the ratio of aluminum-containing solution to EDTA standard solution is 2mL:1~2mL.

[0022] In the method for detecting Al2O3 in electroslag premelted slag, step B2 involves adjusting the pH using an acetic acid-sodium acetate buffer solution with a pH of 5-6.

[0023] In the method for detecting Al2O3 in electroslag premelted slag described above, in step B2, the concentration of the zinc standard solution is 0.02~0.03 mol / L.

[0024] In the above method for detecting Al2O3 in electroslag premelted slag, in step B2, the mass concentration of potassium fluoride aqueous solution is 15~25%.

[0025] In the method for detecting Al2O3 in electroslag premelted slag, in step B2, the ratio of aluminum-containing solution to potassium fluoride aqueous solution is 5 mL: 1~2 mL.

[0026] In step C of this invention, the free aluminum oxide is calculated by the difference method: the content of free aluminum oxide in the sample is calculated according to the following formula: w(Al-Al2O3)=w(Al-total)-w(Al-CA), where w(Al-Al2O3) is the mass fraction of Al present in Al2O3 in the sample (%), w(Al-total) is the measured total mass fraction of Al (%), and w(Al-CA) is the mass fraction of Al in calcium aluminate measured by dilute acid leaching method (%); the actual mass fraction of Al2O3 in the pre-melted slag w(Al2O3) is calculated by the following formula: w(Al2O3)=w(Al-Al2O3)×102 / (27×2), where the constant 102 is the molar mass value of Al2O3, and 27 is the molar mass value of Al atoms.

[0027] The beneficial effects of this invention are:

[0028] This invention employs a specific concentration of dilute acid and strictly controls leaching conditions to accurately distinguish between free Al2O3 and calcium aluminate phases in electroslag premelted slag. It boasts high detection accuracy and strong resistance to fluorine interference, effectively solving the industry problem of phase differentiation that traditional methods cannot address. Utilizing this method facilitates precise control of the effective Al2O3 content in the slag system, optimizes the electroslag remelting process, and reduces losses caused by poor electroslag formation due to high Al2O3 content in the premelted slag.

[0029] The method of this invention improves the detection efficiency by more than 50% compared with the XRD method, significantly shortens the detection time for a single sample, has good equipment compatibility, is easy to operate, has a clear detection process, and is low in cost, making it a significant advantage for widespread application. Attached Figure Description

[0030] Figure 1 The diagram shows the CaF2 phase, Al2O3 phase, and CA6 phase in a typical electroslag premelted slag.

[0031] Figure 2 The phase distribution results of the sample from Example 1 were obtained by scanning with an electron probe mapping function.

[0032] Figure 3 The phase distribution results of the sample from Example 2 were obtained by scanning with the electron probe mapping function. Detailed Implementation

[0033] The present invention will be further described in detail below through embodiments, but the scope of protection of the present invention is not limited to the embodiments described herein.

[0034] Experimental Example 1: Effect of Leaching Acid Ratio on Aluminate Solubility

[0035] 1. Dissolve 0.25g of dodecacalcium heptaaluminate (12CaO·7Al2O3) in 150mL concentrated hydrochloric acid:water = 5:95 (volume ratio) and gently boil for 1 minute. The leaching result is: the solution is turbid. Due to the turbidity of the solution, aluminum dissolution titration is not performed.

[0036] 2. Dissolve 0.25g of dodecacalcium heptaaluminate (12CaO·7Al2O3) in 150mL concentrated hydrochloric acid:water (10:90 volume ratio) and gently boil for 1 minute. The leaching result shows the solution is slightly turbid. EDTA titration of Al yielded an Al content of 23.52%.

[0037] 3. Dissolve 0.25g of dodecacalcium heptaaluminate (12CaO·7Al2O3) in 150mL concentrated hydrochloric acid:water (20:80 volume ratio) and gently boil for 1 minute. The leaching result shows a relatively clear solution. EDTA titration of Al yielded an Al content of 23.60%.

[0038] 4. Dissolve 0.25g of dodecacalcium heptaaluminate (12CaO·7Al2O3) in 150mL concentrated hydrochloric acid and water at a volume ratio of 50:50. Boil gently for 1 minute. The leaching result is a clear solution. EDTA titration of Al yielded an Al content of 23.68%.

[0039] Experimental conclusion: The present invention uses concentrated hydrochloric acid:water = 1:1 volume ratio, and boils gently for 1 minute to completely dissolve dodecacalce heptaaluminate (12CaO·7Al2O3).

[0040] Experimental Example 2: Testing the effects of Al2O3 and CaF2 on dissolution and titration

[0041] 1. Control group: 0.25g of dodecacalcium heptaaluminate (12CaO·7Al2O3) was dissolved in 150mL of concentrated hydrochloric acid:water = 1:1 volume ratio, boiled gently for 1min, and the Al content was titrated with EDTA and found to be 23.68%.

[0042] 2. Dissolve 0.25g of dodecacalcium heptaaluminate (12CaO·7Al2O3) + 0.15g of analytical grade Al2O3 mixed powder in 150mL concentrated hydrochloric acid:water = 1:1 volume ratio. Boil gently for 1min, filter, and use EDTA to titrate the Al in the filtrate. Result: The Al content of the filtrate was 23.89%.

[0043] 3. Dissolve 0.25g of dodecacalcium heptaaluminate (12CaO·7Al2O3) and 0.15g of metallurgical fluorite mixed powder in 150mL concentrated hydrochloric acid:water = 1:1 volume ratio. Boil gently for 1 minute, filter, and use EDTA to titrate the Al in the filtrate. The Al content of the filtrate is 23.48%.

[0044] Experimental conclusion: This invention uses a concentrated hydrochloric acid:water solution with a volume ratio of 1:1, which, after gentle boiling for 1 minute, can completely dissolve the dodecacalcetan heptaaluminate (12CaO·7Al2O3) in the mixed powder. The Al content of the filtrate after filtration is close to that of the control group, and it does not dissolve Al2O3. This invention can achieve the separation of the dodecacalcetan heptaaluminate phase (12CaO·7Al2O3) and the alumina phase in the residue. CaF2 does not affect the titration results.

[0045] Example 1: The method provided by this invention was used to detect the Al2O3 phase content in a 70:30 electroslag premelted slag (nominal content 70wt% CaF2, 30wt% Al2O3) from a certain manufacturer.

[0046] Sample information: Electroslag premelted slag products sold by a certain electroslag premelted slag manufacturer, with a nominal ratio of CaF2:Al2O3=70:30.

[0047] Instruments and reagents: muffle furnace, EDTA standard solution (0.05 mol / L), hydrochloric acid (analytical grade), boric acid (analytical grade), sodium carbonate (analytical grade), hexamethylenetetramine (analytical grade), xylenol orange indicator, copper sulfate (analytical grade), electron probe.

[0048] Step 1: Total Aluminum Determination

[0049] The sample was fused at 905℃ using a mixed solvent of sodium carbonate and boric acid. After leaching with hydrochloric acid, calcium, magnesium, iron, titanium, and aluminum precipitates were separated using hexamethylenetetramine. These precipitates were then dissolved in acid, followed by separation of aluminum from titanium and iron using a strong alkali. The total aluminum content of the filtrate was determined by back titration with copper sulfate. The measured total Al content was 16.31%.

[0050] Step 2: Determination of Aluminum in Calcium Aluminate

[0051] 1. Take 0.4g of electroslag pre-melted slag sample after crushing and grinding (passing through a 200-mesh sieve) and place it in a 250mL beaker.

[0052] 2. Preparation of leachate: Mix concentrated hydrochloric acid and water in a volume ratio of 1:1 and stir to prepare leachate.

[0053] 3. Selective leaching: Pour 150 mL of the leachate into a beaker containing the sample and stir well. Place the beaker on a hot plate and heat it, maintaining a gentle boil (approximately 95°C) while stirring and leaching for 1 minute.

[0054] 4. Separation: After leaching, filter the solution while hot using medium-speed quantitative filter paper, and collect the filtrate in a 250mL volumetric flask. Wash the beaker and residue 3-4 times with the leachate, then wash with hot water until the washings are free of chloride ions (test with AgNO3 solution to ensure no white precipitate is found in the filtrate). After cooling, dilute to the mark with deionized water and mix well.

[0055] 5. EDTA Titration for Aluminum Determination: Transfer 50.00 mL of the above filtrate to a 500 mL Erlenmeyer flask; add 25.00 mL (excess) of 0.05 mol / L EDTA standard solution, heat to boiling for 2 minutes to completely complex the aluminum; cool, add 10 mL of acetate-sodium acetate buffer solution (pH=5.5), and add 3-4 drops of xylenol orange indicator; titrate with 0.025 mol / L zinc standard solution until the solution changes from yellow to orange-red (ignore the reading, this indicates titration of excess EDTA); add 10 mL of 20% potassium fluoride solution, heat to boiling for 2 minutes, and cool; add 2 drops of xylenol orange indicator, and titrate with zinc standard solution until the solution changes from yellow to orange-red as the endpoint, recording the volume V (mL) of zinc standard solution consumed. The determination result shows that the Al content in the form of calcium aluminate is 2.96%.

[0056] Step 3: Calculate free Al2O3 using the difference method

[0057] The aluminum content in Al2O3 is: w(Al-Al2O3)=w(Al-total)-w(Al-CA)=16.31%-2.96%=13.35%. Converted to the Al2O3 content in the pre-melted slag sample, it is: w(Al2O3)=w(Al-Al2O3)×102 / (27×2)=25.22%.

[0058] Step 4: Accuracy Verification

[0059] The sample in this embodiment was prepared, and micro-region phase characterization was performed using an electron probe microanalysis method. The results are as follows: Figure 2 As shown, the Al2O3 phase scanning result is 25%, which is similar to the method provided in this embodiment. In summary, the method provided in this embodiment can quickly distinguish the Al2O3 phase content in electroslag premelted slag.

[0060] Example 2: The method provided by this invention was used to detect the Al2O3 phase content in a 40:30:30 electroslag premelted slag (nominal content 40wt% CaF2, 30wt% Al2O3, 30wt% CaO) from a certain manufacturer.

[0061] Sample information: Electroslag premelted slag products sold by a certain electroslag premelted slag manufacturer, with a nominal ratio of CaF2:Al2O3:CaO=70:30:30.

[0062] Instruments and reagents: muffle furnace, EDTA standard solution (0.05 mol / L), hydrochloric acid (analytical grade), boric acid (analytical grade), sodium carbonate (analytical grade), hexamethylenetetramine (analytical grade), xylenol orange indicator, copper sulfate (analytical grade), electron probe.

[0063] Step 1: Total Aluminum Determination

[0064] The sample was fused at 905℃ using a mixed solvent of sodium carbonate and boric acid. After leaching with hydrochloric acid, calcium and magnesium were separated using hexamethylenetetramine. Precipitates such as iron, titanium, and aluminum were dissolved in acid, and then aluminum was separated from titanium and iron using a strong alkali. The total aluminum content of the filtrate was determined by back titration with copper sulfate. The measured total Al content was 15.00%.

[0065] Step 2: Determination of Aluminum in Calcium Aluminate

[0066] 1. Take 0.4g of electroslag pre-melted slag sample after crushing and grinding (passing through a 200-mesh sieve) and place it in a 250mL beaker.

[0067] 2. Preparation of leachate: Mix concentrated hydrochloric acid and water in a volume ratio of 1:1 and stir to prepare leachate.

[0068] 3. Selective leaching: Pour 150 mL of the leachate into a beaker containing the sample and stir well. Place the beaker on a hot plate and heat it, maintaining a gentle boil (approximately 95°C) while stirring and leaching for 1 minute.

[0069] 4. Separation: After leaching, filter the solution while hot using medium-speed quantitative filter paper, and collect the filtrate in a 250mL volumetric flask. Wash the beaker and residue 3-4 times with the leachate, then wash with hot water until the washings are free of chloride ions (test with AgNO3 solution to ensure no white precipitate is found in the filtrate). After cooling, dilute to the mark with deionized water and mix well.

[0070] 5. EDTA Titration for Aluminum Determination: Transfer 50.00 mL of the above filtrate to a 500 mL Erlenmeyer flask; add 25.00 mL (excess) of 0.05 mol / L EDTA standard solution, heat to boiling for 2 minutes to completely complex the aluminum; cool, add 10 mL of acetate-sodium acetate buffer solution (pH=5.5), and add 3-4 drops of xylenol orange indicator; titrate with 0.025 mol / L zinc standard solution until the solution changes from yellow to orange-red (ignore the reading, this is to titrate excess EDTA); add 10 mL of 20% potassium fluoride solution, heat to boiling for 2 minutes, and cool; add 2 drops of xylenol orange indicator, and titrate with zinc standard solution until the solution changes from yellow to orange-red as the endpoint, recording the volume V (mL) of zinc standard solution consumed. The determination result shows that the Al content in the form of calcium aluminate is 14.50%.

[0071] Step 3: Calculate free Al2O3 using the difference method

[0072] The aluminum content in Al2O3 is: w(Al-Al2O3)=w(Al-total)-w(Al-CA)=15.00%-14.50%=0.50%. Converted to the Al2O3 content in the pre-melted slag sample, it is: w(Al2O3)=w(Al-Al2O3)×102 / (27×2)=0.94%.

[0073] Step 4: Accuracy Verification

[0074] The sample in this embodiment was prepared, and micro-region phase characterization was performed using an electron probe microanalysis method. The results are as follows: Figure 3 As shown, the Al2O3 phase scanning result is close to 0%, which is close to the 0.94% measured by the method provided in this embodiment. In summary, the method provided in this embodiment can quickly distinguish the Al2O3 phase content in electroslag premelted slag.

Claims

1. A method for detecting Al2O3 in electroslag premelted slag, characterized in that: Includes the following steps: A. Total aluminum determination: The total aluminum content w(Al-total) in the electroslag premelted slag was obtained; B. Determination of aluminum in calcium aluminate: B1. Selective leaching: After crushing and pulverizing the electroslag pre-melted slag, it is mixed with the leaching solution at a mass-to-volume ratio of 1g:350~400mL, and then leached while maintaining a gentle boil for 45~75s. After leaching, it is filtered while hot, washed, cooled, and then brought to a final volume and shaken to obtain an aluminum-containing solution. The leaching solution is a mixed solution of concentrated hydrochloric acid and water at a volume ratio of 1±0.1:1±0.

1. B2. EDTA Titration for Aluminum Determination: Mix the aluminum-containing solution with excess EDTA standard solution, heat to boiling to completely complex the aluminum; cool, adjust the pH to 5-6, and add xylenol orange indicator; titrate with zinc standard solution until the solution changes from yellow to orange-red; add potassium fluoride aqueous solution, heat to boiling, so that the EDTA in the Al-EDTA complex is released by fluoride ions, and cool; add more xylenol orange indicator, and titrate with zinc standard solution until the solution changes from yellow to orange-red as the endpoint, record the volume of zinc standard solution consumed, and calculate the aluminum content w(Al-CA) in the form of calcium aluminate in the electroslag premelted slag. C. Calculation of free Al2O3 by difference: The aluminum content of Al2O3 in electroslag pre-melted slag, w(Al-Al2O3), is: w(Al-Al2O3)=w(Al-total)-w(Al-CA). After conversion, the Al2O3 content in the pre-melted slag sample is obtained.

2. The method for detecting Al2O3 in electroslag premelted slag according to claim 1, characterized in that: In step A, the total aluminum content is determined by XRF or titration. The XRF method involves grinding and pressing the electroslag pre-melted slag into tablets, and then using X-ray fluorescence spectroscopy to determine the total aluminum content w(Al-total) in the electroslag pre-melted slag. The titration method involves using a mixed solvent of sodium carbonate and boric acid to melt the electroslag pre-melted slag at 905℃, leaching with hydrochloric acid, separating calcium and magnesium with hexamethylenetetramine, dissolving the precipitate with acid, and then using a strong alkali to separate aluminum from ferrotitanium. The filtrate is then titrated with copper sulfate to determine the total aluminum content w(Al-total) in the electroslag pre-melted slag.

3. The method for detecting Al2O3 in electroslag premelted slag according to claim 1, characterized in that: In step B1, the electroslag pre-melted slag is crushed and powdered, then passed through a 200-mesh sieve, and the material passing through the sieve is collected.

4. The method for detecting Al2O3 in electroslag premelted slag according to claim 1, characterized in that: In step B1, the amount of electroslag pre-melted slag after crushing and grinding is 0.25~0.5g, and the amount of leachate is 95~190mL.

5. The method for detecting Al2O3 in electroslag premelted slag according to claim 1, characterized in that: In step B1, the washing process involves washing the container and residue 3-4 times with the leachate, followed by washing with hot water until the washing solution is free of chloride ions.

6. The method for detecting Al2O3 in electroslag premelted slag according to claim 1, characterized in that: In step B2, the concentration of the EDTA standard solution is 0.03~0.10 mol / L, and the ratio of aluminum-containing solution to EDTA standard solution is 2 mL: 1~2 mL.

7. The method for detecting Al2O3 in electroslag premelted slag according to claim 1, characterized in that: In step B2, the pH is adjusted using an acetate-sodium acetate buffer solution with a pH of 5-6.

8. The method for detecting Al2O3 in electroslag premelted slag according to claim 1, characterized in that: In step B2, the concentration of the zinc standard solution is 0.02~0.03 mol / L.

9. The method for detecting Al2O3 in electroslag premelted slag according to claim 1, characterized in that: In step B2, the mass concentration of the potassium fluoride aqueous solution is 15-25%.

10. The method for detecting Al2O3 in electroslag premelted slag according to claim 1, characterized in that: In step B2, the ratio of aluminum-containing solution to potassium fluoride aqueous solution is 5 mL: 1~2 mL.

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