Method for determining tungsten content in ferrotungsten

Abstract

The invention discloses a method for measuring the tungsten content in ferrotungsten, and belongs to the technical field of detection and analysis of the chemical component content of metal materials, the method comprises seven steps of dissolving a sample, shielding and adjusting the pH value, buffering three times, precipitating four times, aging five times, filtering, drying and weighing six times, and calculating the content, and a shielding agent added in the second step comprises an EDTA solution, oxalic acid and hydroxylamine hydrochloride. After heating to boiling, adjusting the pH value of the solution to about 6.0 by using ammonia water and hydrochloric acid; the buffer solution added in the third step is a mixed solution of ammonium acetate and glacial acetic acid, and the pH value of the buffer solution is 6.5. According to the invention, the measuring result is accurate and stable, the operation is simple and convenient, the consumed time is short, the requirements of the steelmaking industry are met, and the detection efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of detection and analysis of chemical composition content of metal materials, and in particular relates to a method for detecting tungsten content in ferrotungsten. Background Art

[0002] In the metallurgical industry, ferrotungsten is often used as an alloying additive for steelmaking. Tungsten can not only reduce the elongation of steel, but also increase the ultimate strength and yield point of steel, while also increasing the hardness and wear resistance of steel. It is particularly important that tungsten has a good effect on the high temperature mechanical properties of steel, and it can improve heat resistance and tempering stability.

[0003] As a precious iron alloy with a tungsten content in the range of 70% to 80%, on the one hand, the total amount of tungsten needs to be clearly detected before steelmaking, otherwise it will directly affect the performance of the steel; on the other hand, the amount of tungsten used is also indirectly related to the production cost of the enterprise, so how to accurately determine the tungsten content in ferrotungsten is extremely important.

[0004] At present, the national standard detection method for tungsten in ferrotungsten is the Cinchonine gravimetric method (GB7731.1-1987). This method is cumbersome and lengthy, and it takes about 3 days to analyze once, which is difficult to meet the needs of rapid detection in production; our laboratory currently uses the thiocyanate spectrophotometric method. Although this method has a fast analysis speed, it has many interference factors and poor stability. Occasionally, there will be a phenomenon of result drift, and multiple tests are required to determine the results. In this process, a large amount of hydrochloric acid and other drugs are consumed. Therefore, it is necessary to study a detection method that is both fast, stable and accurate.

[0005] Chinese patent document CN103063541A discloses a method for determining the tungsten content in tungsten-iron alloy by 8-hydroxyquinoline weight method, which comprises the following steps:

[0006] A. Weigh 0.2000g of standard sample GBW01428 in a 250ml polytetrafluoroethylene beaker, add 20ml nitric acid, and slowly drop 10ml hydrofluoric acid. After the solution is dissolved, add 5ml perchloric acid, smoke, and cool the solution until it is concentrated to semi-dry; B. After cooling, repeatedly scrub with 15% sodium hydroxide solution and 50% hydrochloric acid solution in a 500ml quartz beaker, control the solution at 150ml, drop 30ml of 10% EDTA solution, heat the solution to boiling, add ammonia water until the solution is clear, and cool it; C. After cooling, adjust the solution with hydrochloric acid (1+1) It is bright yellow, and the pH value is about 6.0. Add 5ml buffer solution, and the pH value is 6.5. Heat to near boiling; D. Add 30ml of 8-hydroxyquinoline solution with a mass concentration of 3% under full stirring and let it stand; E. After cooling to room temperature, filter with medium-speed filter paper and pulp, wash the beaker with hot water, wash the precipitate once, filter it and carbonize it with a platinum crucible with a constant weight of 24g, then move it into a 700℃ horse-boiling furnace and burn it to constant weight to obtain tungsten trioxide. Take out the platinum crucible and place it in a desiccator to cool to room temperature. It weighs 24.1951g; F. Calculate the tungsten content in tungsten-iron alloy according to the following formula:

[0007]

[0008] Therefore, the method for determining the tungsten content in tungsten-iron alloy by 8-hydroxyquinoline weight method in the above patent document includes six steps: one is sample dissolution, two is shielding and pH value adjustment, three is buffer precipitation, four is aging, five is filtration, drying and weighing, and six is ​​content calculation. The first step of dissolving the sample is to first add nitric acid to the beaker containing the sample, then slowly drip hydrofluoric acid, and then add perchloric acid; the second step is to first transfer the dissolved sample to another beaker as much as possible, so the beaker for dissolving the sample should be repeatedly scrubbed with 15% sodium hydroxide solution and 50% hydrochloric acid solution, and the solution volume when the shielding agent is added is controlled to be 150ml, and then 30ml of 10% EDTA solution is added as a shielding agent, and the pH value is adjusted with ammonia water after boiling, and the pH value of the solution is adjusted to about 6.0 with (1+1) hydrochloric acid after cooling; the third step is buffering, that is, adding a buffer solution to make the pH value of the solution 6.5; the fourth step is precipitation, after heating to boiling, adding 8-hydroxyquinoline solution under stirring to generate yellow precipitate of tungsten; the fifth step is aging, that is, leaving the solution to stand; the sixth step is filtering, drying and weighing; the seventh step is content calculation.

[0009] The above method may be a fast and accurate method for determining the tungsten content in ferrotungsten raw materials. However, after repeated experiments using the above method, our laboratory found that the test results were not accurate and could not meet the requirements for industrial content detection. Summary of the invention

[0010] The technical problem to be solved by the present invention is to provide a method for determining the tungsten content in ferrotungsten, hoping that the measurement result can be accurate and stable, and the operation is simple and convenient, the time is short, and the requirements of the steelmaking industry are met to improve the detection efficiency.

[0011] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0012] A method for determining the tungsten content in tungsten iron comprises seven steps: sample dissolution, shielding and pH value adjustment, buffering, precipitation, aging, filtering, drying and weighing, and content calculation. In the second step, the shielding agent added comprises EDTA solution, oxalic acid and hydroxylamine hydrochloride. After heating to boiling, the pH value of the solution is adjusted to about 6.0 with ammonia water and hydrochloric acid. In the third step, the buffer solution added is a mixed solution of ammonium acetate and glacial acetic acid, and the pH value of the buffer solution is 6.5.

[0013] A further improvement of the technical solution of the present invention is that: in the first sample dissolving step, hydrofluoric acid is first added to the sample dissolving vessel containing the sample to be tested, and then nitric acid is added dropwise along the wall of the vessel; after the violent reaction stops, a sufficient amount of nitric acid is added; then the solution is heated until it is clarified, and perchloric acid is added to concentrate the solution to semi-dryness.

[0014] A further improvement of the technical solution of the present invention is that after adding perchloric acid to make the solution smoke and concentrate to semi-dryness, the four walls of the sample dissolving vessel are rinsed with water, and then a saturated boric acid solution is added, and the whole solution is transferred into a beaker.

[0015] A further improvement of the technical solution of the present invention is that: in the process of transferring all the solution into the beaker, the sample dissolving vessel should be cleaned alternately with a small amount of 15% sodium hydroxide solution and (1+1) hydrochloric acid under the condition of heating the sample dissolving vessel, and the cleaning solution is poured into the beaker; finally, the volume of the solution in the beaker is controlled to be 100 ml.

[0016] A further improvement of the technical solution of the present invention is that the preparation method of the buffer solution is: weigh 59.8g of ammonium acetate and dissolve it in water, then add the solution to 1.4ml of glacial acetic acid, then add water to dilute to 1000ml, and mix well.

[0017] A further improvement of the technical solution of the present invention is that the amount of the buffer solution added is 5% of the volume of the solution.

[0018] A further improvement of the technical solution of the present invention is that the amount of the precipitant used in the fourth step is 4.5 to 6.75 times the mass of the sample.

[0019] A further improvement of the technical solution of the present invention is that the aging standing time in the fifth step is no longer than 5 hours.

[0020] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is:

[0021] The method for determining the tungsten content in ferrotungsten of the present invention overcomes the problem of unstable detection results in the prior art, so that each measurement result can be accurate and can meet the requirements of the steelmaking industry. In addition, the method of the present invention is simple and convenient to operate, takes a short time, can improve detection efficiency, and meets the needs of rapid detection.

[0022] The shielding agents used in this invention include not only EDTA solution, but also oxalic acid and hydroxylamine hydrochloride. The addition of these shielding agents masks most of the metal ions in the tungsten iron solution that may produce precipitation, such as Fe 2+ , Fe 3+ 、Al 3+ Cr 3+ 、Be 2+ 、Zn 2+ Etc., especially the Mo contained in tungsten iron, which can be well shielded, so that these metal elements will not precipitate, making the test results more accurate and stable.

[0023] The present invention heats the solution to which the shielding agent is added to boiling, and uses ammonia water and hydrochloric acid to adjust the pH value of the solution at a relatively high temperature. When the pH value is adjusted to about 6.0 in a hot state, it can not only save time but also achieve the best precipitation and separation effects, thus creating conditions for the next step of precipitation.

[0024] The buffer solution added in the third step of the present invention is a mixture of ammonium acetate and glacial acetic acid, and the pH value of the buffer solution is 6.5. The added dosage is only 5% of the volume of the solution to be tested. This pH value and addition ratio will not affect the solubility of the precipitates of tungsten and other elements, so that the precipitation effect is the best, and the detection results can be accurate and stable.

[0025] In the method of the present invention, in the first step of sample dissolution, hydrofluoric acid is first added, and then nitric acid is added dropwise along the wall of the dish; after the violent reaction stops, a sufficient amount of nitric acid is added; in this way, the sample to be tested can be fully dissolved, and the sample dissolution effect is significantly faster than the effect of adding nitric acid first and then adding hydrofluoric acid, which can make the sample dissolve faster and more thoroughly, and can save the amount of nitric acid and hydrofluoric acid used and the sample dissolution time. After heating the solution until it is clear, perchloric acid is added to make the solution smoke and concentrate, so that fluorine and other elements that affect the stability and accuracy of the detection results in the solution can be driven out to the maximum extent. In the present invention, a saturated boric acid solution is added after smoking, and boric acid has a buffering effect, which can replenish the H consumed by the precipitation of tungstic acid to the solution. +, in order to maintain a certain acidity and prevent a sharp change in acidity, so that tungstic acid can be precipitated more completely. When the solution is moved out of the sample dissolving vessel and into the beaker, the platinum dish can be easier to clean, and the next acid-base alternating cleaning step also becomes more convenient. Under the condition of heating the sample dissolving vessel, the sample dissolving vessel is cleaned alternately with a small amount of 15% sodium hydroxide solution and (1+1) hydrochloric acid, which can minimize the residual tungsten element in the sample dissolving vessel to improve the accuracy and stability of the test results.

[0026] The ammonium acetate-glacial acetic acid buffer solution of the present invention is prepared by first dissolving ammonium acetate in water, then pouring them into glacial acetic acid, and then adding water to dilute to 1000 ml. The pH value of the solution can be controlled at 5.5-6.5 by using the buffer solution of the present invention. Under this condition, the precipitation effect is the best, so that the detection result is more accurate, the precision is higher, and the repeatability is better.

[0027] The amount of the precipitant in the present invention is preferably selected within a ratio range of 4.5 to 6.75 times the mass of the sample. If it is less than 4.5 times the mass, it is too little, which will cause incomplete tungsten precipitation; if it is greater than 6.75 times the mass, it is too much, which will not only cause waste of the precipitant, but also may cause precipitation of other metal elements that have been shielded, which will interfere with the stability of the test results.

[0028] The aging standing time of the present invention does not exceed 5 hours, and the optimal standing time is 2 hours. If the time is too long, the precipitate will change, which will greatly affect the test results; if the time is too short, the precipitation may not be completely completed, which will also affect the accuracy of the results.

[0029] In summary, the present invention overcomes the shortcomings of the cinquenine weight method (national standard method) that the operation is complicated and lengthy, and also solves the problems of many interference factors and poor stability of the currently used thiocyanate spectrophotometry. At the same time, it is a method for determining the tungsten content in tungsten iron by the 8-hydroxyquinoline weight method, which achieves good precision, accuracy and stability, and improves detection efficiency and accuracy. DETAILED DESCRIPTION

[0030] A method for determining the tungsten content in tungsten iron includes the six steps of sample dissolution, shielding and pH value adjustment, buffer precipitation, aging, filtering, drying and weighing, and content calculation as described in the background technology part.

[0031] In the first step of sample dissolution, a quantitative amount of the sample to be tested is weighed and placed in a sample dissolution vessel, and then hydrofluoric acid is added first, and then nitric acid is added dropwise along the wall of the sample dissolution vessel, so that the degree of reaction in the sample dissolution process can be slowed down; after the violent reaction stops, sufficient nitric acid is added to ensure that there is enough acid to dissolve the sample to be tested; then the solution is heated until it is clarified, so that the sample to be tested is completely dissolved, and then perchloric acid is added to make the solution smoke and concentrate it to half dryness, so that the fluorine in the solution can be driven out. The present invention dissolves tungsten iron by slowly dropping nitric acid into hydrofluoric acid and along the wall of the dish, and then adding perchloric acid after heating. The sample is dissolved more thoroughly, and compared with the comparative document, the usage of nitric acid and hydrofluoric acid and the sample dissolution time are also saved.

[0032] After adding perchloric acid to make the solution smoke and concentrate to half dry, rinse the four walls of the sample dissolving vessel with water, and then add saturated boric acid solution. Boric acid is a weak acid with a buffering effect. The H+ ionized by it can replenish the H consumed by the precipitation of tungstic acid. + , so that the solution maintains a certain acidity and prevents a sharp change in acidity. Transfer all the solution into the beaker. In the process of transferring all the solution into the beaker, the sample dissolving vessel should be heated. Under the heating condition, use a small amount of 15% sodium hydroxide solution and (1+1) hydrochloric acid to alternately clean the sample dissolving vessel, and pour the cleaning solution into the beaker so that there is no solution residue in the sample dissolving vessel; finally, control the volume of the solution in the beaker to 100ml, so that the test results are more accurate.

[0033] The shielding agents added in the second step include EDTA solution, oxalic acid, and hydroxylamine hydrochloride. After heating to boiling, ammonia and hydrochloric acid are used to adjust the pH value of the solution to about 6.0. When adjusting the pH value, ammonia and (1+1) hydrochloric acid are directly added dropwise after the solution boils until the pH value is adjusted to about 6.0. When adjusting the pH, the solution should appear bright yellow, and the pH value is about 5.0 to 6.5. When it is about 6.0, the precipitation effect is the best, the impact on the test results is the smallest, and the results are the most accurate.

[0034] The buffer solution added in the third step is a mixture of ammonium acetate and glacial acetic acid, and the pH value of the buffer solution is 6.5. The preparation method of the buffer solution is: weigh 59.8g of ammonium acetate and dissolve it in water, then add the solution to 1.4ml of glacial acetic acid, then add water to dilute to 1000ml, and mix well. The amount of buffer solution added is 5% of the volume of the solution, and the pH value of the solution can be ignored at this time.

[0035] The fourth step is precipitation. The above solution is heated to boiling, and under sufficient stirring, a precipitant concentration of 30 g / L 8-hydroxyquinoline solution is added. The amount of the precipitant is 4.5 to 6.75 times the mass of the sample. For a 3% 8-hydroxyquinoline solution, 150 ml to 225 ml of the precipitant solution is added for every gram of sample. In general, the mass of the added 8-hydroxyquinoline is 4.5 times the mass of the sample (the amount of the 3% 8-hydroxyquinoline solution is 150 ml for every gram of sample).

[0036] Then, the fifth step is to perform aging and standing. The longest aging and standing time should not exceed 5 hours, and the shortest should not be less than 0.5 hours, and 2 hours is the best. If the precipitation time exceeds 5 hours or is less than 0.5 hours, the accuracy of the measurement result will be affected.

[0037] After aging, the sixth step of filtering, drying and weighing is carried out. This step is to filter with medium-speed filter paper, first wash the beaker with hot water, then wash the precipitate with hot water 5 to 6 times, filter and dry it, then use a porcelain crucible to ash, and then move it into a muffle furnace, burn it at 750℃ for half an hour to constant weight, so that the precipitate is completely decomposed into WO3.

[0038] The sixth step is to calculate the content, using the following formula:

[0039]

[0040] In the formula: m1-the mass of the crucible and precipitate (tungsten trioxide) after calcination, g

[0041] m2- mass of the crucible, g

[0042] m-mass of the sample, g

[0043] 0.7930 is the conversion factor of tungsten trioxide to tungsten.

[0044] The present invention is further described in detail below in conjunction with embodiments:

[0045] The instruments used in the following examples are: muffle furnace, HNXSL-01A-1300 (Luoyang Haina Testing Instrument Co., Ltd.); electronic analytical balance, sensitivity 0.0001 g, Sartorius; muffle furnace (maximum range 1200° C.); rack balance.

[0046] The reagents involved are: nitric acid, ρ about 1.42 g / mL; hydrofluoric acid: ρ about 1.14 g / mL; hydrochloric acid: ρ about 1.19 g / mL; perchloric acid: ρ about 1.61 g / mL; ammonia water: ρ is 0.91 g / mL; saturated boric acid solution; 5% oxalic acid solution; 10% hydroxylamine hydrochloride; 10% EDTA (ethylenediaminetetraacetic acid disodium salt) solution; buffer solution; 8-hydroxyquinoline solution; among which:

[0047] The buffer solution is an ammonium acetate-acetic acid buffer solution, and its pH is 6.5. The preparation method is as follows: weigh 59.8g of ammonium acetate and dissolve it in water, add it to 1.4ml of glacial acetic acid, dilute it to 1000ml with water, and mix it evenly;

[0048] 8-Hydroxyquinoline solution (30 g / L): weigh 15 g of 8-hydroxyquinoline and dissolve it in 30 ml of glacial acetic acid, dilute to 500 ml with water, and mix well;

[0049] The above reagents are all analytically pure reagents, and the water used is laboratory water that complies with the requirements of GB / T6682.

[0050] Example 1: Verification with standard tungsten iron sample

[0051] In this embodiment, three tungsten standard samples, namely, 58AJT20002 tungsten standard sample (tungsten content 76.24), GBW01428 tungsten standard sample (Jilin Ferroalloy Factory, tungsten content 76.66), and CRM 590-1 tungsten standard sample (tungsten content 79.55), are used to verify the method of the present invention. That is, the three tungsten standard samples are used as test samples, and the tungsten content in the three tungsten standard samples is detected according to the following method.

[0052] Weigh 0.2000g of the above standard sample in a platinum dish for sample dissolution, add 2ml of hydrofluoric acid, add nitric acid dropwise along the wall of the dish, add 4-5ml of nitric acid after the violent reaction stops, heat, and after the solution is clarified, add 5ml of perchloric acid, smoke, until the solution is concentrated to half dry. Rinse the dish with water around, add 10ml of saturated boric acid solution, transfer the solution to a 300ml beaker, heat the platinum dish, and alternately clean the platinum dish with a small amount of 15% sodium hydroxide solution and (1+1) hydrochloric acid, pour the cleaning solution into the beaker, and dilute the solution to 100ml with water.

[0053] Add 30 ml of EDTA solution (100 g / L), 5 ml of oxalic acid (5%), and 5 ml of hydroxylamine hydrochloride (10%) to the above solution, heat, boil for 3 minutes, and then adjust the solution to bright yellow with ammonia water and (1+1) hydrochloric acid in a hot state to make the pH ≈ 6; then, add 5 ml of buffer solution with pH = 6.5, heat until the solution boils, and slowly add 30 ml of 8-hydroxyquinoline solution with a concentration of 30 g / L under sufficient stirring; then let it stand for 30 minutes; filter the solution with medium-speed filter paper, first wash the beaker with hot water, then wash the precipitate with hot water 5 to 6 times, filter it dry, and then use a porcelain crucible to ash it, then move it into a muffle furnace, burn it for half an hour to constant weight, record its weight, and calculate the percentage of tungsten in the tungsten standard sample according to the above formula.

[0054] The above method of this embodiment was repeated to measure each tungsten standard sample 6 times. The results are shown in Table 1, Table 2, and Table 3.

[0055] Table 1 58AJT20002 test results

[0056]

[0057]

[0058] Table 2 GBW01428 test results

[0059]

[0060] Table 3 CRM 590-1 test results

[0061]

[0062]

[0063] From the above table data, we can find that the test results of the three standard samples are slightly different from the standard values, meeting the measurement error requirements in the chemical standard method GB7731.1-1987, and have good accuracy; both the standard deviation and the relative standard deviation are small, indicating that the test method is reliable and has good precision.

[0064] Example 2: Actual sample testing and verification

[0065] In actual work, this laboratory used an unknown tungsten-iron sample for inspection and measured it three times according to the method in the embodiment. The test results were 76.23%, 76.28%, and 76.13% respectively, with an average value of 76.21%.

[0066] At the same time, in order to verify the accuracy of the method of the present invention, we also entrusted the sample to the Hebei Provincial Steel Product Quality Supervision and Inspection Station. The outsourced sample was tested using the national standard GB7731.1-1987 analysis method. The actual measured value was 76.40, and our detection error was less than 0.50%, which met the detection requirements of tungsten iron.

[0067] The above experiments prove that the method for detecting tungsten in ferrotungsten of the present invention achieves the purpose of rapid and convenient detection of tungsten in ferrotungsten and high precision and good accuracy of the detection results. It solves the problems of many interference factors and poor stability in the analysis process of thiocyanate spectrophotometry currently used and the cumbersome and lengthy operation of the cinquenine gravimetric method (national standard method), and can be applied to the detection of tungsten in ferrotungsten.

Claims

1. A method for determining the tungsten content in tungsten iron, comprising seven steps: sample dissolution, shielding and pH adjustment, buffering, precipitation, aging, filtering, drying and weighing, and calculating the content, characterized in that: The shielding agents added in the second step include EDTA solution, oxalic acid, and hydroxylamine hydrochloride. After heating to boiling, ammonia and hydrochloric acid are used to adjust the pH value of the solution to about 6.0; the buffer solution added in the third step is a mixture of ammonium acetate and glacial acetic acid, and the pH value of the buffer solution is 6.

5.

2. A method for determining the tungsten content in ferrotungsten according to claim 1, characterized in that: In the first dissolution step, hydrofluoric acid is first added to the dissolution vessel containing the sample to be tested, and then nitric acid is added dropwise along the wall of the vessel; after the violent reaction stops, sufficient nitric acid is added; then the solution is heated until it is clear, and perchloric acid is added to concentrate the solution to semi-dryness.

3. A method for determining the tungsten content in ferrotungsten according to claim 2, characterized in that: After adding perchloric acid to make the solution smoke and concentrate to semi-dryness, rinse the walls of the sample dissolving vessel with water, then add saturated boric acid solution and transfer all the solution into a beaker.

4. A method for determining the tungsten content in ferrotungsten according to claim 3, characterized in that: In the process of transferring all the solution into the beaker, the sample dissolving vessel should be cleaned alternately with a small amount of 15% sodium hydroxide solution and (1+1) hydrochloric acid under the condition of heating the sample dissolving vessel, and the cleaning solution should be poured into the beaker; Finally, the volume of the solution in the beaker is controlled to be 100 ml.

5. The method for determining the tungsten content in ferrotungsten according to claim 1, characterized in that: The buffer solution is prepared by weighing 59.8 g of ammonium acetate and dissolving it in water, then adding the solution to 1.4 ml of glacial acetic acid, and then adding water to dilute to 1000 ml and mixing well.

6. A method for determining the tungsten content in ferrotungsten according to claim 5, characterized in that: The amount of buffer solution added was 5% of the solution volume.

7. The method for determining the tungsten content in ferrotungsten according to claim 1, characterized in that: The amount of the precipitant used in the fourth step is 4.5 to 6.75 times the mass of the sample.

8. The method for determining the tungsten content in ferrotungsten according to claim 1, characterized in that: The aging standing time in the fifth step is no longer than 5 hours.

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