An automatic titration analysis method for measuring the aluminum content in high aluminum alloy

Abstract

The application provides an automatic titration analysis method for measuring the aluminum content in high aluminum alloy, which adopts direct reaction of fluoride with a test solution to realize one-step direct titration, and determines the aluminum content in the range of 2.00% to 100.00%, and comprises the following steps: sample decomposition; precipitation of interfering ions; calibration of sodium fluoride standard solution; calibration of automatic potentiometric titrator; and measurement of the sample to be tested. The application solves the problems of sample pretreatment and how to avoid the influence of interfering ions on the determination of aluminum content. The titration operation, reading and calculation are automatically completed by the instrument, effectively reducing human errors, and the application has the advantages of simple operation, accurate and rapid results, wide application range and the like.

Description

Technical Field

[0001] This invention relates to the fields of chemistry and metallurgy, specifically to an analytical method for measuring the aluminum content in high-aluminum alloys, and more particularly to an automated titration analytical method for measuring the aluminum content in high-aluminum alloys. Background Technology

[0002] Currently, existing technologies for determining the aluminum content in high-aluminum alloys generally employ the fluoride salt substitution EDTA back titration method. For example, the paper "Determination of Aluminum Content in Ferroalloys by EDTA Complexation-Fluoride Salt Substitution-Copper Sulfate Titration Method" discloses a method for measuring the mass fraction of aluminum in ferroalloys. The ferroalloy sample is leached after alkali melting and acidified to remove Fe... 3+ And Al 3+ Separation, Al 3+ After complexing with EDTA (ethylenediaminetetraacetic acid), the solution is replaced with fluoride salts, and the displaced EDTA solution is titrated with a copper sulfate standard solution to calculate the aluminum mass fraction. This method requires significant manual titration and suffers from drawbacks such as endpoint deviation, human error in readings, difficulty in data monitoring, and high labor intensity. The paper "Automatic Complexometric Potentiometric Titration for the Determination of Aluminum or Aluminum, Iron, and Titanium" uses a lead ion-selective electrode as the indicator electrode, utilizing the selective complexation and displacement effects of EDTA and fluorides, with lead nitrate as the titrant. This method requires a two-step titration: first, excess EDTA is titrated, and then aluminum, iron, and titanium in feldspar are indirectly determined. This method involves numerous reagents, is cumbersome, and determines the combined amount of aluminum, iron, and titanium. The paper "Determination of Aluminum in Ethanol-Aqueous Solution by Fluorine-Aluminum Complexometric Titration Calculation Analysis" uses metallic aluminum with a purity greater than 99.99% to prepare Al... 3+ A mathematical model for the complexometric titration of aluminum ions with a fluoride ion standard solution was derived. This paper focuses on the calculation model for the complexation of fluoride ions with pure aluminum solution. It is well known to those skilled in the art that high-alumina alloys differ significantly from pure aluminum. High-alumina alloys are produced by casting aluminum ingots from metallic aluminum and low-carbon steel using processes such as vacuum smelting in industrial furnaces. In terms of measurement, the complex alloy composition, high content of high-melting-point alloying elements, and related high concentrations present numerous challenges in sample pretreatment and in avoiding the influence of interfering ions on aluminum content determination.

[0003] In summary, the existing technology has the following problems: high-aluminum alloys have complex compositions and contain many high-melting-point alloying elements, which presents many difficulties in sample pretreatment and in avoiding interference from ions in the determination of aluminum content. Summary of the Invention

[0004] This invention provides an automated titration analysis method for measuring the aluminum content in aluminum alloys, and more particularly an automated titration analysis method for measuring the aluminum content in high-aluminum alloys. This method addresses the numerous difficulties in the prior art regarding the complex composition of high-aluminum alloys, the presence of many high-melting-point alloying elements, sample pretreatment, and the avoidance of interference ions in aluminum content determination.

[0005] Therefore, this invention proposes an analytical method for measuring the aluminum content in high-aluminum alloys, and more particularly, an automated titration analytical method for measuring the aluminum content in high-aluminum alloys. To achieve the above objective, this invention provides the following technical solution:

[0006] An automated titration analysis method for measuring the aluminum content in high-aluminum alloys is disclosed. This method involves the direct reaction of a fluoride with the test solution to achieve a one-step direct titration. The aluminum content can be measured in the range of 2.00% to 100.00%. The automated titration analysis method for measuring the aluminum content in high-aluminum alloys includes the following steps:

[0007] S1: Decomposition of the sample

[0008] Weigh a high-aluminum alloy sample into a beaker, moisten it with water, add concentrated hydrochloric acid and concentrated nitric acid, and heat it on an electric furnace to dissolve it, thus obtaining a sample solution.

[0009] S2: Precipitated interfering ions

[0010] Add sodium hydroxide solution to the sample solution to precipitate iron ions. After precipitation is complete, dilute to volume in a volumetric flask, filter dry, and obtain the filtrate of the test sample.

[0011] S3: Standardization with sodium fluoride solution

[0012] An aluminum-iron standard sample, identical to the matrix in the high-aluminum alloy sample, was prepared using aluminum wire and pure iron. The aluminum-iron standard sample was then subjected to sample decomposition and precipitation of interfering iron ions to obtain an aluminum-iron standard solution. A sodium fluoride standard solution was prepared and calibrated using a fluoride ion electrode.

[0013] S4: Automatic Potentiometric Titrator Calibration

[0014] The actual concentration of the prepared sodium fluoride solution is calculated using the following formula:

[0015] C 现 =C 原 *W 理 / W 现

[0016] In the formula: C 现 —The actual concentration of the prepared sodium fluoride solution, in mol / L;

[0017] C 原—The concentration of sodium fluoride solution in the original formula is expressed in mol / L;

[0018] W 理 —Theoretical aluminum ion concentration of the prepared aluminum-iron standard sample, unit: %;

[0019] W 现 —The mass concentration data of aluminum ions measured by the instrument, in %;

[0020] Input the calculated actual concentration of the prepared sodium fluoride solution into the automatic potentiometric titrator to calibrate the automatic potentiometric titrator;

[0021] S5: Measurement of the test sample

[0022] Take the filtrate of the sample to be tested from step S2, add anhydrous ethanol and sodium chloride solution, adjust the pH of the solution with hydrochloric acid or ammonia, add buffer solution to obtain the sample to be tested solution, insert the silver-silver chloride reference electrode and fluoride ion selective electrode into the sample to be tested solution, start the potentiometric titrator to measure, and judge the end of the reaction based on the potential jump during the titration process.

[0023] Further, step S1 specifically involves: weighing 0.05-0.50g of high-aluminum alloy sample into a 250mL beaker, rinsing with water, adding 10mL of concentrated hydrochloric acid and 5mL of concentrated nitric acid, and heating on an electric furnace to dissolve the sample solution.

[0024] Further, step S2 specifically involves: after the sample solution becomes clear, cooling it, adding sodium hydroxide solution to the sample solution to precipitate iron ions, and after complete precipitation, adding 5-10 mL of excess sodium hydroxide solution, controlling the temperature at 60-80℃, keeping it warm for 10-15 min, removing it to cool, making up to 250 mL in a volumetric flask, and filtering it dry to obtain the filtrate of the sample to be tested.

[0025] Further, step S3 specifically involves: preparing an aluminum-iron standard sample consistent with the matrix in the high-aluminum alloy sample using aluminum wire with a purity >99.99% and pure iron with a purity ≥99.98%; performing sample decomposition and precipitation of interfering ions on the aluminum-iron standard sample according to steps S1 and S2 to obtain an aluminum-iron standard sample filtrate; transferring the aluminum-iron standard sample filtrate into a beaker, adding anhydrous ethanol and sodium chloride solution, adjusting the pH of the solution using hydrochloric acid or ammonia, adding a buffer solution to obtain an aluminum-iron standard sample solution; preparing a sodium fluoride standard solution and calibrating it using a fluoride ion electrode.

[0026] Further, in step S3, the aluminum-iron standard sample filtrate is transferred into a beaker, and 60 mL of anhydrous ethanol and 20 mL of sodium chloride solution are added sequentially along the inner wall of the beaker.

[0027] Furthermore, in step S3, the pH of the solution is adjusted to 4.48–4.52 using hydrochloric acid or ammonia, and 10 mL of acetic acid-sodium acetate buffer solution is added.

[0028] Furthermore, in step S3, the hydrochloric acid is prepared by diluting concentrated hydrochloric acid with water, and the volume ratio of the concentrated hydrochloric acid to the water is 1:3.

[0029] Further, step S5 specifically involves: transferring the filtrate of the sample to be tested from step S2 into a beaker, adding 60 mL of anhydrous ethanol and 20 mL of sodium chloride solution sequentially along the inner wall of the beaker, adjusting the pH of the solution to 4.48–4.52 using hydrochloric acid or ammonia, adding 10 mL of acetate-sodium acetate buffer solution to obtain the sample to be tested solution, inserting the silver-silver chloride reference electrode and fluoride ion selective electrode into the sample to be tested solution, and starting the potentiometric titrator for determination.

[0030] Furthermore, the pH of the acetic acid-sodium acetate buffer solution is 4.5.

[0031] Furthermore, the potentiometric titrator determined the reaction formula as follows: Al 3+ +6F - =AlF6 3- .

[0032] This invention detects the aluminum content in high-aluminum alloys. High-aluminum alloys have complex compositions, with numerous and high-content high-melting-point alloying elements, and interference from iron-based and coexisting elements, affecting aluminum content determination. Therefore, current automated potentiometric titration methods can address sample pretreatment and avoid the influence of interfering ions. Furthermore, this invention, based on the complexation reaction between fluoride ions and aluminum ions, also allows potentiometric titration to meet the determination requirements. In addition, the disadvantage of conventional titration methods is the need for two-step titration (adding EDTA to complex Al, then using fluoride to release the EDTA complexed with aluminum, followed by titration with zinc or copper solution), which is cumbersome and makes it difficult to determine the titration endpoint manually. This invention solves the interference between aluminum and iron through sample pretreatment (sample decomposition, precipitation of interfering ions, and standardization with sodium fluoride standard solution). Finally, the optimal fluoride ion electrode is selected as the indicator electrode, and the Al in the solution is directly titrated with fluoride solution in a one-step process. During the titration process, the titration curve can be automatically plotted, resulting in high sensitivity and accuracy and reducing human error. Furthermore, the aluminum content determination range of this invention is 2.00% to 100.00%, which is significantly wider than the determination range of EDTA titration (aluminum content determination range of 2.00% to 45.00%) and copper sulfate titration. Attached Figure Description

[0033] Figure 1 This is a potentiometric titration curve of the present invention;

[0034] The following are the symbols and their meanings: 1. First derivative (ERC curve); 2. Titration curve; 21. Equivalence point (EP1). Detailed Implementation

[0035] To provide a clearer understanding of the technical features, objectives, and effects of this invention, the invention is now described.

[0036] I. Selection of Automated Potentiometric Titration Analysis Method

[0037] High-aluminum alloys are important composite deoxidizing agents. In the steelmaking process, they can effectively reduce oxygen content, minimizing the formation of bubbles due to carbon-oxygen reactions. Simultaneously, they can refine the steel's grain structure, thereby improving impact toughness and reducing cold brittleness and aging tendency. Liuzhou Steel commonly produces high-aluminum steels such as ML08Al-1G, St37-2G-1R, and L280VK-1R, which are widely used in deep-drawn complex parts for automobiles, tractors, and enamelware industrial machinery. With the increasing demand for lightweight automobiles, the smelting of special-grade automotive steel sheets places extremely stringent requirements on raw material quality and smelting process control. Therefore, controlling the aluminum content is crucial for improving steel cleanliness. This urgently necessitates innovative methods for aluminum detection to meet the demands of the current green development era. However, existing detection methods cannot adequately determine the aluminum content in high-aluminum alloys. For example:

[0038] 1. Because high-aluminum alloys have a high aluminum content, spectrophotometric detection requires dilution and the preparation of a series of standard solutions, which is cumbersome and prone to errors.

[0039] 2. If X-ray fluorescence spectrometry is used, the powder pressing method suffers from matrix interference and particle effects. Alternatively, if the fused sample method is used, the problem of elemental metal corrosion of the platinum crucible must first be addressed. Currently, for aluminum determination using fluorescence methods, iodides or bromides are generally used as release agents. When using iodides, prolonged sample pretreatment leads to iodine sublimation, eliminating the release effect and easily causing fragment cracking. When using bromides, bromine (Br) interferes with aluminum in fluorescence, resulting in poor analytical accuracy for aluminum (Al).

[0040] 3. When using ICP spectroscopy (inductively coupled plasma spectroscopy), if the Al content is >15%, it needs to be diluted before measurement, which will introduce errors, and a series of standard solutions also need to be prepared.

[0041] Since this invention detects the aluminum content in high-aluminum alloys, and high-aluminum alloys have complex compositions with numerous and high-content high-melting-point alloying elements, there is interference from iron-based and coexisting elements, affecting the determination of aluminum content. Therefore, potentiometric titration currently meets the requirements for sample pretreatment and avoiding the influence of interfering ions. Furthermore, this invention is based on the complexation reaction between fluoride ions and aluminum ions, and potentiometric titration also meets the determination requirements. Considering these two points, potentiometric titration is more suitable, as other detection methods cannot meet the requirements. Currently, there is no specific and accurate standard for an automated potentiometric titration method in the field for detecting the aluminum content in high-aluminum alloys in the range of 2.00% to 100.00%. Therefore, how to use potentiometric titration to determine the aluminum content in high-aluminum alloys in one step is a difficult problem. II. Specific Implementation Methods

[0043] To solve the above problems, the technical solution adopted by the present invention is: an automatic titration analysis method for measuring the aluminum content in high-aluminum alloys, comprising the following steps: sample decomposition; separation of interfering substances; standardization with sodium fluoride standard solution; calibration of automatic potentiometric titrator; and measurement of the sample to be tested.

[0044] The analytical method for aluminum content in high-aluminum alloys described in this invention involves decomposing the sample with concentrated nitric acid and concentrated hydrochloric acid, using alkaline reagents to precipitate interfering ions and eliminate interfering elements such as iron and titanium, using sodium salt as an ionic strength regulator in a water-ethanol reaction system, and based on the complexation reaction between fluoride ions and aluminum ions in a medium with pH = 4.5, directly titrating the aluminum in the solution with a standard sodium fluoride solution using an automatic potentiometric titrator.

[0045] The specific reaction formula is: Al 3+ +6F - =AlF6 3- ;

[0046] 1. Experimental Procedure

[0047] The present invention will be further described in detail below with reference to embodiments: The automatic titration analysis method for measuring the aluminum content in high-aluminum alloys includes the following steps:

[0048] A. Decomposition of the sample

[0049] Weigh 0.05-0.50g of high-aluminum alloy sample into a 250mL beaker, add an appropriate amount of water to rinse, add 10mL of concentrated hydrochloric acid and 5mL of concentrated nitric acid, cover with a watch glass, and after no obvious small bubbles overflow, heat at low temperature on an electric furnace to dissolve and obtain the sample solution.

[0050] B. Precipitating interfering ions

[0051] Once the sample solution is clear and free of black particles, remove it from the container, let it cool slightly, wash the watch glass and the walls of the beaker with water, and add sodium hydroxide solution while stirring to precipitate iron ions. After precipitation is complete, add a slight excess of 5-10 mL, rinse the inner wall of the beaker, and continue to keep it at a low temperature (60-80℃) for 10-15 min. Remove and cool, then dilute to a 250 mL volumetric flask, filter dry, and obtain the filtrate of the sample to be tested.

[0052] C. Standardization with sodium fluoride standard solution

[0053] An aluminum-iron standard sample, identical to the matrix in the high-alumina alloy sample, was prepared using aluminum wire and pure iron. The aluminum-iron standard sample was then subjected to sample decomposition and precipitation of interfering iron ions to obtain an aluminum-iron standard solution. A sodium fluoride standard solution was prepared and calibrated using a fluoride ion electrode. An aluminum-iron standard sample, identical to the matrix in the high-alumina alloy sample, was prepared using aluminum wire with a purity >99.99% and pure iron with a purity ≥99.98%. The aluminum-iron standard sample was subjected to sample decomposition and precipitation of interfering ions sequentially according to steps A and B to obtain an aluminum-iron standard filtrate. 25.00 mL of the aluminum-iron standard filtrate was accurately transferred. The filtrate was placed in a beaker, and 60 mL of anhydrous ethanol and 20 mL of sodium chloride solution were added sequentially along the inner wall of the beaker. Then, the pH of the solution was adjusted to 4.48–4.52 using hydrochloric acid (the hydrochloric acid was prepared by diluting concentrated hydrochloric acid with water, and the volume ratio of concentrated hydrochloric acid to water was 1:3) or ammonia. 10 mL of acetate-sodium acetate buffer solution (the pH of the acetate-sodium acetate buffer solution was 4.5) was added. The prepared sodium fluoride standard solution was then calibrated using an aluminum-iron standard solution. The analytical electrode used during titration was a fluoride ion selective electrode.

[0054] D. Calibration of automatic potentiometric titrator

[0055] The actual concentration of the prepared sodium fluoride solution is calculated using the following formula:

[0056] C 现 =C 原 *W 理 / W 现

[0057] In the formula: C 现 —The actual concentration of the prepared sodium fluoride solution, in mol / L;

[0058] C 原 —The concentration of sodium fluoride solution in the original formula is expressed in mol / L;

[0059] W 理 —Theoretical aluminum ion concentration of the prepared aluminum-iron standard sample, unit: %;

[0060] W 现 —The mass concentration data of aluminum ions measured by the instrument, in %;

[0061] Among them, according to C原 W 理 W 现 Calculate the actual concentration of the prepared sodium fluoride solution, and then input the calculated actual concentration value of the prepared sodium fluoride solution into the automatic potentiometric titrator to calibrate the automatic potentiometric titrator;

[0062] E. Measurement of the test sample

[0063] After the instrument is calibrated, the sodium fluoride standard solution is prepared again. The second sodium fluoride standard solution is measured using the calibrated automatic potentiometric titrator to confirm whether the calibration data is correct and whether there are any problems in the previous calibration process. If there are no problems, the sample is measured.

[0064] Accurately transfer 25.00 mL of the filtrate from step B into a beaker. Add 60 mL of anhydrous ethanol and 20 mL of sodium chloride solution sequentially along the inner wall of the beaker. Adjust the pH of the solution to 4.48–4.52 using hydrochloric acid or ammonia. Add 10 mL of acetate-sodium acetate buffer solution to obtain the test solution. Insert the silver-silver chloride reference electrode and fluoride ion selective electrode into the test solution and start the potentiometric titrator for determination. The potentiometric titration diagram is shown below. Figure 1 The end of the reaction is determined by the potential jump during the titration process.

[0065] Figure 1 The x-axis represents the titration volume V of sodium fluoride standard solution added, in mL. Label 1 is the first derivative potentiometric titration curve (ERC curve, where ERC is the ratio of potential change to time, dimensionless), corresponding to the right y-axis. Label 2 is the titration curve, corresponding to the left y-axis U (U represents voltage), in millivolts (mV). Curve 1 represents the magnitude of the jump in curve 2, reflecting the rate of potential change. The highest point indicates the location of the largest potential jump, and this is used to confirm the endpoint. The relationship between the two is that the faster the potential change, the larger the ERC; conversely, a small change results in a small ERC.

[0066] The black dot 21 on curve 2 is EP1. EP1 is the equivalence point, which is the volume point at which fluoride ions react with aluminum to reach an equal amount. At this point, a change in potential will occur, that is, a curve jump will appear. When the height value of the extreme point of the ERC curve is greater than the EPC (set threshold) value, the jump can be identified as an equivalence point.

[0067] At the start of titration, the potential gradually decreases as more sodium fluoride standard solution is added. A titration curve is plotted with the volume of sodium fluoride standard solution added as the x-axis and ΔE / ΔV as the y-axis (ΔE is the potential difference, referring to the potential change between the titration endpoint and the initial point; ΔV is the titrant volume difference, referring to the difference between the titrant volume at the titration endpoint and the initial volume). The highest point of the curve is the titration endpoint. A perpendicular line is drawn from the highest point to the x-axis; the intersection point represents the volume of sodium fluoride standard solution consumed, thus allowing for the quantitative measurement of the aluminum content.

[0068] 2. Experimental Data and Results

[0069] The precision and accuracy of the automatic titration analysis method for measuring aluminum content in high-aluminum alloys of the present invention will be verified below.

[0070] 2.1 Accuracy Test

[0071] a. Three different samples were taken and compared using automatic potentiometric titration and YB / T4393-2014 method respectively. The allowable difference in Al content measurement results is ±0.40%. The results are detailed in Table 1. The determination methods of this invention all meet the requirements.

[0072] Table 1 Comparison of results between automatic potentiometric titration and the YB / T4393-2014 method

[0073]

[0074] b. The EDTA titration method and the automatic potentiometric titration method of the present invention were used to determine the aluminum content of 15 groups of low-content aluminum samples and 10 groups of high-content aluminum samples, respectively. The results are shown in Table 2. The Al content values ​​measured by the present invention are consistent with those measured by the chemical method. The Al content measurement results are all within the allowable error range, which proves that the determination method of the present invention meets the determination requirements for both low-content and high-content aluminum in the samples and has high accuracy.

[0075] Table 2 Comparison of results from automatic potentiometric titration and EDTA titration methods

[0076]

[0077] 2.2 Precision Test

[0078] To verify the precision of the method and examine its accuracy and reliability, two samples with different concentration levels were selected, and nine parallel determinations were performed for each concentration level. Sample number 3-289 (aluminum-iron standard) and sample number 2-127 (high-purity aluminum) were used as the test samples, and nine analyses were performed using automatic potentiometric titration to calculate the aluminum (Al) content. The laboratory repeatability standard deviation was confirmed according to GB / T6379.2-2004, Basic Methods for Repeatability of Measurement Methods and Results. In the following formula, Ss represents the laboratory repeatability standard deviation, calculated from the measured data, and Sr also represents the laboratory repeatability standard deviation, calculated using the repeatability limit r specified in the national standard.

[0079] Formula 1: Since only one laboratory data point is used for calculation in the experiment, i = 1, and P represents the number of measurements, which is 2. Therefore, r is calculated using the simplest formula, resulting in formula two: This indicates that, at a 95% probability level, the absolute value of the difference between two independent test results in the laboratory is less than the r value. According to formula two, we can obtain: Table 3 shows that the measured Al content values ​​for the two samples at different concentration levels were both S. S <S r The results demonstrate that the precision is controllable, indicating that the analytical method described in this invention has good precision. The results are shown in Table 3.

[0080] Table 3 Samples with precision obtained by automatic potentiometric titration method

[0081]

[0082] In summary, the method of the present invention has high accuracy and precision in detecting the aluminum content in high-aluminum alloys.

[0083] Compared with the prior art, the present invention has the following advantages:

[0084] 1. Currently, there is no domestic method for determining the aluminum content in aluminum alloys using electrochemical methods based on potential changes. This invention employs the aforementioned technical solution, and multiple experiments have proven that this method enables one-step endpoint titration, eliminating the need for stepwise determination. This invention utilizes the direct reaction of fluoride with the test solution, achieving one-step direct titration without the need for two-step back titration, resulting in smaller errors and enabling faster, more accurate, and economical quantitative testing of the aluminum content in the solution. This invention differs from the chemical analysis methods and content in the original standard (YB / T4393-2014). This method overcomes many defects and shortcomings of the existing standard, reduces experimental analysis time and costs, while meeting the analytical requirements of high-aluminum alloys. It is easily promoted and applied in actual production, providing positive guidance for smelting production. Furthermore, the aluminum content determination range studied in this invention is 2.00%–100.00%, significantly wider than the determination ranges of EDTA titration (aluminum content determination range 2.00%–45.00%) and copper sulfate titration.

[0085] 2. This invention examines the interference from iron-based elements and coexisting elements, uses sodium hydroxide for preliminary analysis of the interference, and then uses sodium chloride as an ionic strength modifier to overcome the interference by adopting appropriate methods. It mainly solves the interference between aluminum and iron, which greatly improves the accuracy of analysis.

[0086] 3. This invention selects the optimal analytical electrode as a fluoride ion selective electrode through conditional experiments, which is an analytical technique not found in existing technologies for aluminum content determination.

[0087] 4. The values ​​measured by this invention are consistent with those measured by chemical methods, and the experimental data are more accurate. The titration operation, reading, and calculation of the analytical method of this invention are completed automatically by the instrument, eliminating the need for the operator to judge the color endpoint with the naked eye. This effectively reduces human error, greatly shortens the analysis time, and reduces labor intensity. It has the advantages of simple operation, accurate and fast results, and wide applicability.

[0088] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. The various components of the present invention can be combined with each other without conflict. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. An automatic titration analysis method for measuring the aluminum content in a high aluminum alloy, characterized by, The automatic titration analysis method for measuring the aluminum content in high aluminum alloy adopts direct reaction of fluoride with the test solution to realize one-step direct titration, and the aluminum content range is 2.00%-100.00%. The automatic titration analysis method for measuring the aluminum content in high aluminum alloy comprises the following steps: S1: sample decomposition A high aluminum alloy sample is weighed in a beaker, water is added for wetting, concentrated hydrochloric acid and concentrated nitric acid are added, and heating is performed on an electric furnace to dissolve the sample, thereby obtaining a sample solution; S2: precipitation of interfering ions Sodium hydroxide solution is added to the sample solution to precipitate iron ions, and after complete precipitation, the solution is diluted to a constant volume in a volumetric flask, and dry filtration is performed, thereby obtaining a test sample filtrate; S3: calibration of sodium fluoride standard solution An aluminum-iron standard sample consistent with the matrix in the high aluminum alloy sample is prepared by using an aluminum wire and pure iron; the aluminum-iron standard sample is subjected to sample decomposition and precipitation of interfering ions to obtain an aluminum-iron standard sample solution; A sodium fluoride standard solution is prepared, and the solution is calibrated by using a fluoride ion electrode; S4: calibration of the automatic potentiometric titrator The actual concentration of the prepared sodium fluoride solution is calculated according to the following formula: C 现 =C 原 *W 理 / W 现 In the formula: C 现 - Actual solution concentration of the prepared sodium fluoride, unit: mol / L; C 原 - Theoretical concentration of the prepared sodium fluoride standard solution, unit: mol / L; W 理 - Theoretical aluminium ion concentration of the aluminium iron standard sample, in %; W 现 - actual aluminium ion concentration of the aluminium iron standard sample, in %; The calculated actual concentration of the prepared sodium fluoride solution is input into the automatic potentiometric titrator to calibrate the titrator; S5: measurement of the test sample The test sample filtrate in step S2 is removed, anhydrous ethanol and sodium chloride solution are added, hydrochloric acid or ammonia water is used to adjust the pH of the solution, a buffer solution is added, and a test sample solution is obtained; a silver-silver chloride reference electrode and a fluoride ion selective electrode are inserted into the test sample solution, and the potentiometric titrator is started to perform measurement; the reaction is determined to be complete according to the potential jump in the titration process; The step S5 is specifically as follows: the test sample filtrate in step S2 is removed into a beaker, 60 mL of anhydrous ethanol and 20 mL of sodium chloride solution are sequentially added along the inner wall of the beaker, hydrochloric acid or ammonia water is used to adjust the pH of the solution to 4.48-4.52, 10 mL of acetic acid-sodium acetate buffer solution is added, and a test sample solution is obtained; a silver-silver chloride reference electrode and a fluoride ion selective electrode are inserted into the test sample solution, and the potentiometric titrator is started to perform measurement; The reaction equation determined by the potentiometric titrator is: Al 3+ + 6F - = AlF6 3- .

2. The automatic titration analysis method for measuring the content of aluminum in a high aluminum alloy according to claim 1, characterized by, The step S1 is specifically as follows: 0.05-0.50 g of a high aluminum alloy sample is weighed into a 250 mL beaker, water is added for wetting, 10 mL of concentrated hydrochloric acid and 5 mL of concentrated nitric acid are added, and heating is performed on an electric furnace to dissolve the sample, thereby obtaining a sample solution.

3. The automatic titration analysis method for measuring the content of aluminum in a high aluminum alloy according to claim 1, characterized in that, The step S2 is specifically as follows: after the sample solution becomes clear, cooling is performed, sodium hydroxide solution is added to the sample solution to precipitate iron ions, 5-10 mL of excess sodium hydroxide solution is added after complete precipitation, the temperature is controlled at 60-80°C, and the solution is kept at this temperature for 10-15 min; the solution is then removed for cooling, diluted to a constant volume in a 250 mL volumetric flask, and dry filtered, thereby obtaining a test sample filtrate.

4. The automatic titration analysis method for measuring the content of aluminum in a high aluminum alloy according to claim 1, characterized in that, The step S3 is specifically as follows: an aluminum-iron standard sample consistent with the matrix in the high aluminum alloy sample is prepared by using an aluminum wire with a purity of >99.99% and pure iron with a purity of ≥99.98%; the aluminum-iron standard sample is subjected to sample decomposition and precipitation of interfering ions according to steps S1 and S2, thereby obtaining an aluminum-iron standard sample filtrate; the aluminum-iron standard sample filtrate is removed into a beaker, anhydrous ethanol and sodium chloride solution are added, hydrochloric acid or ammonia water is used to adjust the pH of the solution, a buffer solution is added, and an aluminum-iron standard sample solution is obtained. Prepare the standard solution of sodium fluoride and calibrate it with fluoride ion electrode.

5. The automatic titration analysis method for measuring the content of aluminum in a high aluminum alloy according to claim 4, characterized in that, In the S3 step, the aluminum-iron standard sample filtrate is taken into a beaker, 60 mL of anhydrous ethanol and 20 mL of sodium chloride solution are added along the inner wall of the beaker.

6. The automatic titration analysis method for measuring the content of aluminum in a high aluminum alloy according to claim 5, characterized in that, In the S3 step, the solution is adjusted to a pH of 4.48-4.52 using hydrochloric acid or ammonia water, and 10 mL of acetic acid-sodium acetate buffer solution is added.

7. The automatic titration analysis method for measuring the content of aluminum in a high aluminum alloy according to claim 4, characterized in that, In the S3 step, the hydrochloric acid is diluted with water, and the volume ratio of the concentrated hydrochloric acid to the water is 1:

3.

8. The automatic titration analysis method for measuring the content of aluminum in high aluminum alloy according to claim 1, characterized in that, The acetic acid-sodium acetate buffer solution has a pH of 4.5.

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