Determination method for phosphorus content in sintered flux

Abstract

The invention provides a method for measuring the content of phosphorus in sintered flux. The method comprises the following steps: S1, providing a to-be-measured sample; s2, adding a flux into the to-be-tested sample to obtain a mixed sample, melting the mixed sample under a high-temperature condition, and cooling the melt to obtain a cooled sample; s3, adding a hydrochloric acid solution into the cooled sample, and heating to leach the phosphorus element to obtain a leached solution; s4, perchloric acid is added into the leaching solution, heating evaporation is conducted till smoke is generated, and phosphorus is oxidized into orthophosphoric acid; s5, under the preset acidity condition, bismuth salt and ammonium molybdate are added into the leaching solution generating orthophosphoric acid, bismuth phosphorus molybdenum yellow ternary heteropolyacid is generated after reaction, ascorbic acid is added, and bismuth phosphorus molybdenum blue is generated after reaction; and S6, measuring the absorbance of the solution containing bismuth phosphorus molybdenum blue through a spectrophotometer, and calculating to obtain the phosphorus content of the to-be-tested sample. According to the method for measuring the phosphorus content in the sintered flux, the measuring accuracy is improved, and the measuring process is simpler and more efficient.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical component detection, and particularly to a method for determining the phosphorus content in a sintered welding flux. Background Art

[0002] For the determination of the phosphorus content in a sintered welding flux, there is currently no applicable national standard method, nor any industry analysis method for reference. The determination methods recorded in JB / T7948.6-2017 "Chemical Analysis Methods for Welding Fluxes - Part 6: Determination of Phosphorus Content" include two methods: the molybdenum blue photometric method and the bismuth phosphomolybdenum blue photometric method.

[0003] When using the first method, the sintered welding flux cannot be completely dissolved, so it is not applicable.

[0004] When using the second method, when determining the phosphorus content by the bismuth phosphomolybdenum blue photometric method, it is necessary to dissolve the sample simultaneously with the determination of manganese oxide, aluminum oxide, iron oxide, calcium oxide, and magnesium oxide, etc. There are relatively many influencing factors to consider, and the operation steps are relatively cumbersome, and it is easily interfered by the determination of other elements. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies existing in the prior art, and to provide a method for determining the phosphorus content in a sintered welding flux, so as to make the determination process of the phosphorus content in the sintered welding flux simpler, more efficient, and more accurate.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A method for determining the phosphorus content in a sintered welding flux, comprising the following steps: S1. Provide a test sample; S2. Add a flux to the test sample to obtain a mixed sample, melt the mixed sample under high-temperature conditions, and then cool the melt to obtain a cooled sample; S3. Add a hydrochloric acid solution to the cooled sample, heat to leach out the phosphorus element to obtain a leaching solution; S4. Add perchloric acid to the leaching solution and heat to evaporate until it smokes to oxidize the phosphorus into orthophosphoric acid; S5. Under a preset acidity condition, add a bismuth salt and ammonium molybdate to the leaching solution generating the orthophosphoric acid, react to generate a bismuth phosphomolybdic yellow ternary heteropolyacid, and add ascorbic acid, and react to generate bismuth phosphomolybdenum blue; S6. Measure the absorbance of the solution containing the bismuth phosphomolybdenum blue by a spectrophotometer, and calculate the phosphorus content of the test sample.

[0007] Further, step S1 includes the following steps: The test sample is ground to make the particle size of the sample less than 200 mesh, dried in the temperature range of 105°C - 110°C, and then cooled to room temperature to obtain the test sample to be tested.

[0008] Further, step S2 includes the following steps: Put 0.1 g of the test sample to be tested and 2 g of the mixed flux into a platinum crucible, and then cover 1 g of the flux in the crucible to obtain the mixed sample; the flux includes anhydrous sodium carbonate and sodium tetraborate, and the mass ratio of anhydrous sodium carbonate to sodium tetraborate is 2:1; Heat and melt the mixed sample at a temperature of 950°C - 1000°C for 15 minutes - 20 minutes. After the melting is completed, make the melt adhere to the inner wall of the crucible, and cool the crucible to obtain a cooled sample.

[0009] Further, step S3 includes the following steps: Put the crucible into a beaker containing 20 ml of hydrochloric acid, heat the beaker to dissolve the melt adhering to the inner wall of the crucible, then wash and take out the crucible to leach out the phosphorus element to obtain a leaching solution.

[0010] Further, step S4 includes the following steps: Add sulfuric acid and perchloric acid to the beaker, heat and evaporate until white smoke appears to oxidize phosphorus into orthophosphoric acid. After slightly cooling the beaker, add water to the beaker, continue to cool to room temperature, dilute to a volume of 50 ml and filter to obtain a test solution.

[0011] Further, step S5 includes the following steps: Under the preset acidity condition, take 10 ml of the test solution and place it in a 50 - ml volumetric flask. Then add 10 ml of the mixed solution, 5 ml of ascorbic acid and 10 ml of absolute ethanol to the volumetric flask, and dilute with water to 50 ml, and let it stand to obtain a working solution; the mixed solution includes bismuth nitrate solution and ammonium molybdate solution.

[0012] Further, the bismuth nitrate solution and the ammonium molybdate solution in the mixed solution are mixed in equal volumes; The preparation steps of the bismuth nitrate solution are as follows: Take 2.5 g of bismuth nitrate and dissolve it in 400 ml of sulfuric acid (1 + 7), heat to dissolve and then filter; The concentration of the ammonium molybdate solution is 2.5%.

[0013] Further, step S6 includes the following steps: Use the blank test as the reference solution in a colorimetric cell, measure the absorbance of the working solution at a wavelength of 680 nm on a spectrophotometer, find out the corresponding phosphorus content from the working curve, and calculate the phosphorus content of the test sample to be tested.

[0014] Further, the working curve is drawn in the following manner: Measure 0 mL, 1 mL, 4 mL, 6 mL, and 8 mL of phosphorus standard solution respectively, and place them in 50-mL volumetric flasks. Add 6 mL of perchloric acid to the volumetric flasks, add water to 10 mL, then add 10 mL of the said mixed solution, 5 mL of ascorbic acid, and 10 mL of absolute ethanol, dilute with water to 50 mL, let stand. Using the reagent blank solution as the reference solution, measure the absorbance at a wavelength of 680 nm on a spectrophotometer. Draw the working curve with the phosphorus content as the abscissa and the absorbance as the ordinate.

[0015] Further, the phosphorus content of the test sample is calculated in the following manner: ; wherein, m1 is the phosphorus content found from the working curve, in micrograms; m is the mass of the test sample, in grams; V1 is the volume of the phosphorus standard solution taken, in mL; V is the total volume of the solution in the volumetric flask, in mL.

[0016] According to the technical solution of the present invention, the method for determining the phosphorus content in the sintered flux provided by the present invention melts the test sample through a flux, then leaches out the phosphorus element with a hydrochloric acid solution, then oxidizes the phosphorus to orthophosphoric acid by adding perchloric acid, reacts with bismuth salt and ammonium molybdate to form a ternary heteropolyacid of phosphorus molybdenum yellow, and forms bismuth phosphorus molybdenum blue after reduction with ascorbic acid. Then the absorbance can be measured by a spectrophotometer, and further the mass fraction of the phosphorus element can be calculated. The whole process is very simple and efficient, realizes the separate determination of the phosphorus element, is not interfered by the determination of other elements, and improves the accuracy of the determination. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a flow schematic diagram of the method for determining the phosphorus content in the sintered flux of the embodiment of the present invention.

[0018] Figure 2 is a schematic diagram of the working curve drawn in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs. The terms used in the specification of this invention are for the purpose of describing specific embodiments only and are not intended to limit the invention.

[0021] As Figure 1 shown, the method for determining the phosphorus content in the sintered welding flux of the embodiments of this invention includes the following steps: S1. Provide the test sample.

[0022] Specifically, after grinding the sample, pass it through a 200-mesh sieve or other means to make the particle size of the sample less than 200 mesh, and dry it at a temperature range of 105°C - 110°C for 1 hour, then place it in a desiccator to cool to room temperature to obtain the test sample.

[0023] S2. Add a flux to the test sample to obtain a mixed sample, melt the mixed sample under high-temperature conditions, and then cool the melt to obtain a cooled sample.

[0024] Specifically, weigh 0.1 g of the test sample with an analytical balance, the weighing accuracy of the analytical balance is accurate to 0.1 mg, then weigh 2 g of the mixed flux, place them together in a platinum crucible, stir evenly, and then cover 1 g of flux in the crucible to obtain a mixed sample. The flux includes anhydrous sodium carbonate and sodium tetraborate, the mass ratio of anhydrous sodium carbonate to sodium tetraborate is 2:1, and the purities of both anhydrous sodium carbonate and sodium tetraborate are of analytical purity.

[0025] Cover the crucible lid, heat and melt the mixed sample in a high-temperature furnace at a temperature condition of 950°C - 1000°C for 15 minutes - 20 minutes. After the melting is completed, take out the crucible and rotate the crucible to make the melt adhere to the inner wall of the crucible, and cool the crucible to obtain a cooled sample.

[0026] S3. Add hydrochloric acid solution to the cooled sample, heat to leach out the phosphorus element to obtain a leaching solution.

[0027] Specifically, wipe the outer wall of the crucible with filter paper, then put the crucible into a beaker containing 20 ml of hydrochloric acid (1+1), heat the beaker to dissolve the melt adhering to the inner wall of the crucible, wash the crucible with water, and take out the crucible from the beaker to leach out the phosphorus element to obtain a leaching solution.

[0028] This invention adopts the method of alkali fusion to completely melt the test sample, and then leaches out the phosphorus element by the method of hydrochloric acid leaching.

[0029] S4. Add perchloric acid to the leaching solution, heat and evaporate until fuming to oxidize the phosphorus into orthophosphoric acid.

[0030] Specifically, add 2 - 4 drops of sulfuric acid (1 + 1) and 6 mL of perchloric acid (density 1.67 g / mL) into a beaker, heat and evaporate until white fumes are emitted to oxidize phosphorus into orthophosphoric acid. After 2 minutes, remove the beaker from the heat, stop heating, let the beaker cool slightly, then add 20 mL of water into the beaker, continue to cool to room temperature, transfer it into a 50 - mL volumetric flask, dilute it with water to a volume of 50 mL, and perform dry filtration to obtain the test solution.

[0031] In step S3, all test samples have formed leaching solutions, and all are subjected to heat - fuming treatment with perchloric acid. Compared with the prior - art method of first acid - dissolving, then alkali - fusing the insoluble residue and acid - leaching, the present invention not only has a simpler process flow, but also can avoid the situation where the sample after alkali - fusing cannot participate in the fuming reaction with perchloric acid, thus improving the accuracy of detection.

[0032] S5. Under the preset acidity condition, add bismuth salt and ammonium molybdate into the leaching solution that generates orthophosphoric acid. After reaction, bismuth phosphomolybdate yellow ternary heteropolyacid is formed, and then add ascorbic acid. After reaction, bismuth phosphomolybdate blue is formed.

[0033] Specifically, under the preset acidity condition, accurately pipette 10 mL of the test solution into a 50 - mL volumetric flask, then add 10 mL of the mixed solution, 5 mL of ascorbic acid (1% concentration, freshly prepared), and 10 mL of absolute ethanol (mass fraction 99.5%) into the volumetric flask, and dilute with water to 50 mL. After mixing evenly, let it stand for 10 minutes to prepare the working solution; the mixed solution includes bismuth nitrate solution and ammonium molybdate solution. The preparation steps of the bismuth nitrate solution are as follows: Dissolve 2.5 g of bismuth nitrate in 400 mL of sulfuric acid (1 + 7), heat to dissolve and then filter. The concentration of the ammonium molybdate solution is 2.5%. Mix the bismuth nitrate solution and the ammonium molybdate solution in equal volumes to obtain the above - mentioned mixed solution, and the mixed solution is prepared when needed.

[0034] S6. Measure the absorbance of the solution containing bismuth phosphomolybdate blue with a spectrophotometer, and calculate the phosphorus content of the test sample.

[0035] Use a 1 - cm - 3 - cm colorimetric cell, use the blank reagent of the blank test as the reference solution, measure the absorbance of the working solution at a wavelength of 680 nm on the spectrophotometer, find the corresponding phosphorus content from the working curve, and calculate the phosphorus content of the test sample.

[0036] The working curve is drawn in the following way: Measure 0 mL, 1 mL, 2 mL, 4 mL, 6 mL, 8 mL, 12 mL, and 16 mL of phosphorus standard solution respectively, and place them in 50-mL volumetric flasks. Add 6 mL of perchloric acid (1+4) to the volumetric flasks, add water to 10 mL, then add 10 mL of the above-mentioned mixed solution, 5 mL of ascorbic acid (1% concentration, freshly prepared), and 10 mL of anhydrous ethanol (mass fraction 99.5%). Dilute with water to 50 mL, mix well, and let stand for 10 minutes. Using the reagent blank solution as the reference solution, measure the absorbance at a wavelength of 680 nm on a spectrophotometer. Plot a working curve with the phosphorus content as the abscissa and the absorbance as the ordinate.

[0037] Preparation of phosphorus standard solution: Weigh 0.4394 g of potassium dihydrogen phosphate (primary standard reagent KH2PO4 %>99.99, pre-dried at 110°C ± 5°C for 2 hours and then cooled to constant weight in a desiccator) and dissolve it in 200 mL of water. Add 10 mL of perchloric acid (density 1.67 g / mL), then transfer it to a 1000-mL volumetric flask and dilute to the mark with water, and mix well to obtain the first solution. 1 mL of this solution contains 100 μg of phosphorus.

[0038] Transfer 20.00 mL of the first solution to a 1000-mL volumetric flask and dilute to the mark with water, and mix well to obtain the phosphorus standard solution. 1 mL of this solution contains 2 μg of phosphorus.

[0039] The phosphorus content of the test sample is calculated as follows: ; where m1 is the phosphorus content obtained from the working curve, in micrograms; m is the mass of the test sample, in grams; V1 is the volume of the phosphorus standard solution taken, in milliliters; and V is the total volume of the solution in the volumetric flask, in milliliters.

[0040] The difference between the analysis results of each experiment should not be greater than the allowable difference listed in Table 1. When verifying with a standard test (blank test), the difference between the analysis result and the standard value of the standard sample should not be greater than half of the allowable difference listed in Table 1.

[0041]

[0042] Such as Figure 2As shown in the figure, it is the working curve graph of the embodiment of the present application. The colorimetric cuvette selected is 1 cm, and the concentration of the phosphorus standard solution selected is 2 μg / mL. When 0 mL of the phosphorus standard solution is taken (V1 = 0 mL), the mass number is 0 μg (m1 = 0 μg), and the absorbance at this time is 0; when 1 mL of the phosphorus standard solution is taken (V1 = 1 mL), the mass number is 2 μg (m1 = 2 μg), and the absorbance at this time is 0.028; when 2 mL of the phosphorus standard solution is taken (V1 = 2 mL), the mass number is 4 μg (m1 = 4 μg), and the absorbance at this time is 0.056; when 4 mL of the phosphorus standard solution is taken (V1 = 4 mL), the mass number is 8 μg (m1 = 8 μg), and the absorbance at this time is 0.086; when 6 mL of the phosphorus standard solution is taken (V1 = 6 mL), the mass number is 12 μg (m1 = 12 μg), and the absorbance at this time is 0.136; when 8 mL of the phosphorus standard solution is taken (V1 = 8 mL), the mass number is 16 μg (m1 = 16 μg), and the absorbance at this time is 0.188; when 12 mL of the phosphorus standard solution is taken (V1 = 12 mL), the mass number is 24 μg (m1 = 24 μg), and the absorbance at this time is 0.268; when 16 mL of the phosphorus standard solution is taken (V1 = 16 mL), the mass number is 32 μg (m1 = 32 μg), and the absorbance at this time is 0.352.

[0043] The water used in the above experiments can be distilled water, deionized water or water of equivalent purity (which should comply with the provisions of GB / T6682).

[0044] The method for determining the phosphorus content in the sintered flux provided by the embodiment of the present application has a simple process and is easy to operate. It can separately determine the phosphorus element in the sintered flux without being interfered by the determination of other elements, effectively improving the determination efficiency and meeting the determination requirements of the phosphorus element in the sintered flux with a phosphorus content below 0.06% (usually between 0.02% - 0.04%). It has been improved in terms of sample weighing amount, flux type, sample melting temperature, sample melting time and the drawing of the working curve, and has achieved good analysis results.

[0045] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combinations of these technical features do not conflict, they should be considered as the scope described in this specification.

[0046] The above embodiments merely represent the preferred embodiments of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A method for determining the phosphorus content in a sintering flux, characterized in that: The following steps are involved: S1. Provide the sample to be tested; S2, adding a flux to the sample to be tested to obtain a mixed sample, melting the mixed sample under high temperature conditions, and then cooling the melt to obtain a cooled sample; S3, adding hydrochloric acid solution to the cooled sample, heating to leach phosphorus element, and obtaining a leaching solution; S4, adding perchloric acid to the leaching solution, and heating and evaporating the solution until smoke is emitted, so as to oxidize phosphorus into orthophosphoric acid; S5. Under a preset acidity condition, a bismuth salt and ammonium molybdate are added to the leaching solution for generating the orthophosphoric acid to generate bismuth phosphomolybdate yellow ternary heteropoly acid, and ascorbic acid is added to generate bismuth phosphomolybdate blue after reaction; S6. Measuring the absorbance of the solution containing the bismuth phosphomolybdenum blue by a spectrophotometer, and calculating the phosphorus content of the sample to be tested.

2. The method for determining the phosphorus content in sintering flux according to claim 1, characterized in that: Step S1 includes the following steps: The sample is ground to a particle size of less than 200 meshes, dried at a temperature range of 105° C. to 110° C., and then cooled to room temperature to obtain the sample to be tested.

3. The method for determining the phosphorus content in sintering flux according to claim 2, characterized in that: Step S2 includes the following steps: 0.1 g of the sample to be tested and 2 g of a mixed flux are placed in a platinum crucible, and then 1 g of the flux is covered in the crucible to obtain the mixed sample; the flux comprises anhydrous sodium carbonate and sodium tetraborate, and the mass ratio of the anhydrous sodium carbonate to the sodium tetraborate is 2:1; The mixed sample is heated and melted at a temperature of 950° C. to 1000° C. for 15 to 20 minutes. After the melting is completed, the molten material is attached to the inner wall of the crucible, and the crucible is cooled to obtain a cooled sample.

4. The method for determining the phosphorus content in sintering flux according to claim 3, characterized in that: Step S3 includes the following steps: The crucible is placed in a beaker containing 20 ml of hydrochloric acid, and the beaker is heated to dissolve the molten material adhering to the inner wall of the crucible. The crucible is then washed and taken out to leach phosphorus to obtain a leaching solution.

5. The method for determining the phosphorus content in sintering flux according to claim 4, characterized in that: Step S4 includes the following steps: Sulfuric acid and perchloric acid are added to the beaker, and the mixture is heated and evaporated until white smoke is emitted to oxidize phosphorus into orthophosphoric acid. After the beaker is cooled slightly, water is added to the beaker, and the mixture is further cooled to room temperature, diluted to a fixed volume, and filtered to obtain a solution to be tested.

6. The method for determining the phosphorus content in sintering flux according to claim 5, characterized in that: Step S5 includes the following steps: Under the preset acidity condition, 10 ml of the solution to be tested is placed in a 50 ml volumetric flask, and then 10 ml of the mixed solution, 5 ml of ascorbic acid and 10 ml of anhydrous ethanol are added to the volumetric flask, and water is added to dilute it to 50 ml, and the working solution is obtained by standing; the mixed solution includes a bismuth nitrate solution and an ammonium molybdate solution.

7. The method for determining the phosphorus content in sintering flux according to claim 6, characterized in that: The bismuth nitrate solution and the ammonium molybdate solution in the mixed solution are mixed in equal volumes; The preparation steps of the bismuth nitrate solution are as follows: 2.5 grams of bismuth nitrate is dissolved in 400 milliliters of sulfuric acid, heated to dissolve, and then filtered; The concentration of the ammonium molybdate solution is 2.5%.

8. The method for determining the phosphorus content in sintering flux according to claim 7, characterized in that: Step S6 includes the following steps: In a cuvette, a blank test is used as a reference solution, and the absorbance of the working solution is measured on a spectrophotometer at a wavelength of 680 nm. The corresponding phosphorus content is found from the working curve, and the phosphorus content of the sample to be tested is calculated.

9. The method for determining the phosphorus content in sintering flux according to claim 8, characterized in that: The working curve is drawn in the following way: 0 ml, 1 ml, 4 ml, 6 ml and 8 ml of phosphorus standard solution were measured respectively and placed in 50 ml volumetric flasks respectively, 6 ml of perchloric acid was added to the volumetric flask, water was added to 10 ml, 10 ml of the mixed solution, 5 ml of ascorbic acid and 10 ml of absolute ethanol were added, the solution was diluted to 50 ml with water, and the solution was allowed to stand for 10 minutes. The reagent blank solution was used as a reference solution, and absorbance was measured on a spectrophotometer at a wavelength of 680 nm. A working curve was drawn with phosphorus content as the abscissa and absorbance as the ordinate.

10. The method for determining the phosphorus content in sintering flux according to claim 9, characterized in that: The phosphorus content of the sample to be tested is calculated in the following manner: ； Among them, m1 is the phosphorus content found on the working curve, in micrograms; m is the sample mass, in grams; V1 is the volume of the measured phosphorus standard solution, in milliliters; V is the total volume of the solution in the volumetric flask, in milliliters.

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