A method for determining acid-insoluble aluminum in aluminum-magnesium-calcium alloy

Abstract

The present invention relates to a method for determining acid-insoluble aluminum in aluminum-magnesium-calcium alloys. Based on the chemical properties of the aluminum-magnesium-calcium alloy, dilute nitric acid and room-temperature magnetic stirring are used to separate acid-soluble aluminum from acid-insoluble aluminum. The acid-insoluble aluminum is detected using an inductively coupled plasma mass spectrometer. The present invention has the advantages of high accuracy, good precision, a wide detection range, and a low detection limit. It is a pre-detection method for raw materials used in steelmaking, providing more accurate information on the composition and content of raw materials for steelmaking technology, and offering technical support and assurance for lean steelmaking.

Description

Technical Field

[0001] The present invention relates to testing technology, in particular to a method for determining acid-insoluble aluminum in aluminum-magnesium-calcium alloy. Background Art

[0002] Aluminum-magnesium-calcium-iron alloy is one of the primary raw materials for steelmaking and serves as an effective deoxidizer. The aluminum content in aluminum-magnesium-calcium-iron alloys generally ranges from 55% to 60%. Existing detection methods focus solely on the detection of total aluminum in aluminum-magnesium-calcium alloys, but there are currently no methods for detecting the acid-insoluble aluminum. With the continuous rise in domestic raw material prices, the demand for analytical accuracy is also increasing. Accurately measuring aluminum content and distinguishing the presence of aluminum in aluminum-magnesium-calcium alloys is of great practical significance to steelmaking production.

[0003] Currently, there are no national standards or other relevant methods for the determination of acid-insoluble aluminum in aluminum-magnesium-calcium-iron alloys. Most papers focus on methods for detecting acid-insoluble aluminum in steel, and these methods are often chemical or inductively coupled plasma spectroscopy. There is no method for detecting acid-insoluble aluminum in aluminum-magnesium-calcium alloys using inductively coupled plasma mass spectrometry.

[0004] Acid-insoluble aluminum in finished steel poses a significant risk. Currently, testing for this content primarily focuses on finished steel, with little attention paid to the raw materials used in steelmaking. Steelmaking is a complex chemical process, and accurate testing of the chemical composition and structure of raw materials is crucial for ensuring the quality of finished steel and a preventative measure against contamination of molten steel during the process. Summary of the Invention

[0005] The present invention provides a method for determining acid-insoluble aluminum in aluminum-magnesium-calcium alloy. The purpose of the present invention is to propose a pre-detection method for raw materials for steel smelting, to provide more accurate composition and content of raw materials for steel smelting technology, and to provide technical support and guarantee for lean steelmaking.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for determining acid-insoluble aluminum in aluminum-magnesium-calcium alloy comprises the following steps:

[0008] 1) Sample digestion: Place the sample in a 250mL beaker and slowly add 1-10mL of water dropwise. After no obvious reaction, slowly add 10-70mL of nitric acid in portions. Control the temperature between 10-30°C and stir magnetically. React until there is no obvious change in the sample. Heat to 30-60°C, stir magnetically again, then cool and let stand.

[0009] 2) Separation of acid-soluble aluminum from acid-insoluble aluminum: Filter with slow filter paper, rinse the precipitate with dilute nitric acid, and rinse the residual dilute nitric acid with water;

[0010] 3) Extraction and melting of acid-insoluble aluminum: Place the sample obtained in step 2) in a porcelain crucible and dry it in an electric furnace at 300-450°C for 50-80 minutes. Remove the crucible and ash it in a muffle furnace at 800-1000°C for 20-40 minutes. Weigh the ashed material.

[0011] Weigh 0.3-3.0g of mixed alkaline flux and put it into ash-free filter paper; put the ash into the alkaline mixed flux, stir evenly, then wrap it with ash-free filter paper and tighten the mouth, put it on a porcelain crucible, pad the bottom of the porcelain crucible with carbon powder, and place the porcelain crucible 3-5cm away from the door of the muffle furnace; heat it in stages: the first stage is 100-300℃, the current is 8 amperes; the second stage is 300-600℃, the current is 12 amperes; after reaching 600±5℃, put the porcelain crucible into the furnace. The crucible is pushed inward parallel to the temperature by 3 to 8 cm and kept for 10 to 30 minutes. The third stage is 600 to 850 ° C, the current is 15 amperes, and after reaching 900 ± 5 ° C, the porcelain crucible is pushed inward parallel to the temperature by 3 to 8 cm and kept for 10 to 25 minutes. The fourth stage is 850 to 950 ° C, the current is 15 amperes, and after reaching 950 ± 5 ° C, the porcelain crucible is pushed inward parallel to the temperature by 3 to 8 cm, the door is closed for 28 to 40 minutes, and then taken out and cooled.

[0012] 4) Prepare the sample for testing: Remove the carbon powder and place the ash sample in a 150mL beaker. Add 8-15mL of nitric acid and heat at 100-200°C to dissolve the ash sample. After the ash sample is completely dissolved, cool to room temperature and transfer to a 100mL volumetric flask. Adjust to volume and mix thoroughly.

[0013] 5) Combined with inductively coupled plasma mass spectrometry detection, a standard aluminum working curve is configured and the analysis results are calculated.

[0014] The sample diameter is less than 0.100 mm.

[0015] The sample mass is 0.5 to 5.0000 g.

[0016] In the above step 1), the concentration of nitric acid is such that the volume ratio of nitric acid to water is 10% to 30%.

[0017] The magnetic stirring in step 1) is controlled to have a rotation speed between 60 and 240 r / min, a first stirring time of 3 to 12 h, a second stirring time of 0.5 to 2 h, and a standing time of 2 to 6 h.

[0018] The alkaline mixed flux is a mixture of sodium carbonate, boric acid and lithium tetraborate, wherein the sodium carbonate is 5% to 50%, the boric acid is 5% to 50% and the lithium tetraborate is 5% to 50%.

[0019] In the above step 4), the concentration of nitric acid is such that the volume ratio of nitric acid to water is 20% to 70%.

[0020] The specific method of the above step 5) is:

[0021] a. Prepare aluminum standard stock solution and develop standard solution working curve according to different aluminum standard stock solution concentrations;

[0022] b. The sample solution was introduced into an inductively coupled plasma mass spectrometer (ICP-MS) via a peristaltic pump. After the device stabilized for 1 hour, a working curve established using a prepared aluminum standard stock solution was used for testing and calculations.

[0023] c. Use argon as the power gas, and the argon gas volume fraction is greater than 99.99%;

[0024] d. Test the above step 4) obtained by analyzing the test solution and the blank test solution, the instrument automatically processes the data according to the working curve, calculates and outputs the mass concentration of aluminum;

[0025] e. The content of aluminum element is expressed as the mass fraction of the element W Al Calculation, the value is expressed in %, according to formula (1):

[0026]

[0027] In formula (1): w Al ——Mass fraction of aluminum element to be measured;

[0028] c0——the concentration of aluminum in the blank solution, in μg / mL;

[0029] c1——mass concentration of aluminum in the sample solution, in μg / mL;

[0030] V——total volume of test solution, in mL;

[0031] m——mass of the sample, in g.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention separates acid-soluble aluminum from acid-insoluble aluminum based on the chemical properties of aluminum-magnesium-calcium alloy by using dilute nitric acid and room temperature magnetic stirring, and detects the acid-insoluble aluminum by using an inductively coupled plasma mass spectrometer. The present invention has the advantages of high accuracy, good precision, wide detection range, low detection limit, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0035] The present invention will be described in more detail by way of examples. These examples are merely descriptions of the best mode of carrying out the present invention and do not limit the scope of the present invention in any way.

[0036] A method for determining acid-insoluble aluminum in aluminum-magnesium-calcium alloy comprises the following steps:

[0037] 1) Sample digestion: Place the sample in a 250mL beaker and slowly add 1-10mL of water dropwise. After no obvious reaction, slowly add 10-70mL of nitric acid in portions. Control the temperature between 10-30°C and stir magnetically. React until there is no obvious change in the sample. Heat to 30-60°C, stir magnetically again, then cool and let stand.

[0038] 2) Separation of acid-soluble aluminum from acid-insoluble aluminum: Filter with slow filter paper, rinse the precipitate with dilute nitric acid, and rinse the residual dilute nitric acid with water;

[0039] 3) Extraction and melting of acid-insoluble aluminum: Place the sample obtained in step 2) in a porcelain crucible and dry it in an electric furnace at 300-450°C for 50-80 minutes. Remove the crucible and ash it in a muffle furnace at 800-1000°C for 20-40 minutes. Weigh the ashed material.

[0040] Weigh 0.3-3.0g of mixed alkaline flux and put it into ash-free filter paper; put the ash into the alkaline mixed flux, stir evenly, then wrap it with ash-free filter paper and tighten the mouth, put it on a porcelain crucible, pad the bottom of the porcelain crucible with carbon powder, and place the porcelain crucible 3-5cm away from the door of the muffle furnace; heat it in stages: the first stage is 100-300℃, the current is 8 amperes; the second stage is 300-600℃, the current is 12 amperes; after reaching 600±5℃, put the porcelain crucible into the furnace. The crucible is pushed inward parallel to the temperature by 3 to 8 cm and kept for 10 to 30 minutes. The third stage is 600 to 850 ° C, the current is 15 amperes, and after reaching 900 ± 5 ° C, the porcelain crucible is pushed inward parallel to the temperature by 3 to 8 cm and kept for 10 to 25 minutes. The fourth stage is 850 to 950 ° C, the current is 15 amperes, and after reaching 950 ± 5 ° C, the porcelain crucible is pushed inward parallel to the temperature by 3 to 8 cm, the door is closed for 28 to 40 minutes, and then taken out and cooled.

[0041] 4) Prepare the sample for testing: Remove the carbon powder and place the ash sample in a 150mL beaker. Add 8-15mL of nitric acid and heat at 100-200°C to dissolve the ash sample. After the ash sample is completely dissolved, cool to room temperature and transfer to a 100mL volumetric flask. Adjust to volume and mix thoroughly.

[0042] 5) Combined with inductively coupled plasma mass spectrometry detection, a standard aluminum working curve is configured and the analysis results are calculated.

[0043] The sample diameter is less than 0.100 mm.

[0044] The sample mass is 0.5 to 5.0000 g.

[0045] In the above step 1), the concentration of nitric acid is such that the volume ratio of nitric acid to water is 10% to 30%.

[0046] The magnetic stirring in step 1) is controlled to have a rotation speed between 60 and 240 r / min, a first stirring time of 3 to 12 h, a second stirring time of 0.5 to 2 h, and a standing time of 2 to 6 h.

[0047] The alkaline mixed flux is a mixture of sodium carbonate, boric acid and lithium tetraborate, wherein the sodium carbonate is 5% to 50%, the boric acid is 5% to 50% and the lithium tetraborate is 5% to 50%.

[0048] In the above step 4), the concentration of nitric acid is such that the volume ratio of nitric acid to water is 20% to 70%.

[0049] The specific method of the above step 5) is:

[0050] a. Prepare aluminum standard stock solution and develop standard solution working curve according to different aluminum standard stock solution concentrations;

[0051] Prepare aluminum standard stock solution: weigh 0.1000g of aluminum metal (W Al ≥99.999%), place in a 50mL dual-purpose bottle, add 5mL of hydrochloric acid (1+1), heat at 120°C until completely dissolved, add 15mL of water, heat to dissolve, cool, transfer to a 1000mL volumetric flask, dilute to the mark with water, and mix thoroughly. The concentration of this solution is 100.00μg / mL, which can then be diluted stepwise to 10.00μg / mL, 1.00μg / mL, and 0.10μg / mL.

[0052] A working curve configuration example: Transfer the aluminum standard stock solution to a 100mL volumetric flask, add 10mL of nitric acid (1+2), mix, and dilute to volume. The working curve is shown in Table 1.

[0053] Table 1 Working curve of aluminum concentration in standard solution

[0054]

[0055]

[0056] b. The sample solution was introduced into an inductively coupled plasma mass spectrometer (ICP-MS) via a peristaltic pump. After the instrument stabilized for 1 hour, a working curve was established using the prepared aluminum standard stock solution for testing and calculation. The correlation coefficient of the working curve for aluminum was required to be ≥0.9995.

[0057] c. Use argon as the power gas, and the argon gas volume fraction is greater than 99.99%;

[0058] d. Test the above step 4) obtained by analyzing the test solution and the blank test solution, the instrument automatically processes the data according to the working curve, calculates and outputs the mass concentration of aluminum;

[0059] The determination method of the present invention takes into account the possibility of residual aluminum in the reagents used to prepare the sample, so the blank test solution is also measured;

[0060] e. The content of aluminum element is expressed as the mass fraction of the element W Al Calculation, the value is expressed in %, according to formula (1):

[0061]

[0062] In formula (1): w Al ——Mass fraction of aluminum element to be measured;

[0063] c0——the concentration of aluminum in the blank solution, in μg / mL;

[0064] c1——mass concentration of aluminum in the sample solution, in μg / mL;

[0065] V——total volume of test solution, in mL;

[0066] m——mass of the sample, in g.

[0067] The present invention uses equipment:

[0068] Inductively coupled plasma mass spectrometer (Thermo Fisher Scientific, USA, model: iCAP Q);

[0069] Acid purifier (Savillex, USA, model: DST-4000).

[0070] Each sample of the present invention was analyzed independently three times.

[0071] Precision control of the present invention:

[0072] The absolute difference between the measured values ​​of two independent test results obtained under repeatability conditions shall not exceed the repeatability limit (r) within the range of the average values ​​given below, and the excess of the repeatability limit (r) shall not exceed 5%. The repeatability limit (r) shall be determined by linear interpolation based on the data in Table 2.

[0073] Table 2 Repeatability limit (r)

[0074]

[0075] The allowable difference between laboratories should not be greater than that in Table 3.

[0076] Table 3 Allowable differences between laboratories

[0077]

[0078] Example 1: Measurement of the content of acid-insoluble aluminum in aluminum-magnesium-calcium alloy HB2203118

[0079] The calculation results using the method of the present invention are as follows: the content of acid-insoluble aluminum in the aluminum-magnesium-calcium alloy HB2203118 is 0.00085%.

[0080] Example 2: Measurement of the Acid-Insoluble Aluminum Content in the Aluminum-Magnesium-Calcium Alloy HB2204005

[0081] The experimental process is the same as that of Example 1. The calculated results show that the content of acid-insoluble aluminum in the aluminum-magnesium-calcium alloy HB2204005 is 0.00112%.

[0082] The present invention has the following advantages:

[0083] 1) The sample treatment process of the present invention is carried out at room temperature using magnetic stirring and a single dilute nitric acid dissolution method, which has the advantage of a simple matrix background.

[0084] 2) The separation effect of the present invention is good. Under room temperature conditions, magnetic stirring can effectively separate acid-soluble aluminum from acid-insoluble aluminum. Magnetic stirring for 24 hours at room temperature can ensure that the acid-soluble aluminum in the sample reacts completely.

[0085] 3) The present invention uses an inductively coupled plasma mass spectrometer, which is one of the most advanced detection equipment in existing trace detection, with the characteristics of low detection limit, wide detection range, fast detection speed and strong anti-interference ability.

[0086] 4) The present invention has a wide detection range and a low detection limit. Since it uses an inductively coupled plasma mass spectrometer, its detection range is much wider than that of an inductively coupled plasma spectrometer, and its detection limit can reach the ppb level, which is not available in an inductively coupled plasma spectrometer.

Claims

1. A method for determining acid-insoluble aluminum in aluminum-magnesium-calcium alloy, characterized in that: The method comprises the following steps: 1) Sample digestion: Place the sample in a beaker and add 1-10 mL of water dropwise. After no reaction occurs, add 10-70 mL of nitric acid in portions. Control the temperature between 10-30°C and stir magnetically. React until the sample shows no change. Heat to 30-60°C and stir magnetically again. Then cool and allow to stand. 2) Separation of acid-soluble aluminum from acid-insoluble aluminum: Filter with slow filter paper, rinse the precipitate with dilute nitric acid, and rinse the residual dilute nitric acid with water; 3) Extraction and melting of acid-insoluble aluminum: Place the sample obtained in step 2) in a porcelain crucible and dry it in an electric furnace at 300-450°C for 50-80 minutes. Remove the crucible and ash it in a muffle furnace at 800-1000°C for 20-40 minutes. Weigh the ashed material. Weigh 0.3-3.0 g of a mixed alkaline flux and place it on ash-free filter paper; place the ash in the alkaline mixed flux and stir evenly, then wrap it with ash-free filter paper and tighten the mouth, place it on a porcelain crucible, pad the bottom of the porcelain crucible with carbon powder, and place the porcelain crucible 3-5 cm from the door of the muffle furnace; heat it in stages: first stage 100-300°C, second stage 300-600°C; after reaching 600±5°C, push the porcelain crucible inward parallelly by 3-8 cm and hold it for 10-30 minutes; third stage 600-850°C, after reaching 900±5°C, push the porcelain crucible inward parallelly by 3-8 cm and hold it for 10-25 minutes; fourth stage 850-950°C, after reaching 950±5°C, push the porcelain crucible inward parallelly by 3-8 cm, close the door for 28-40 minutes, remove it, and cool it; 4) Prepare the sample by volume: Remove the carbon powder and place the ash sample in a beaker. Add 8-15 mL of nitric acid and heat at 100-200°C to dissolve the ash sample. After the ash sample is completely dissolved, cool to room temperature, transfer to a volumetric flask, adjust to volume, and mix thoroughly. 5) Combined with inductively coupled plasma mass spectrometry detection, a standard aluminum working curve is configured and the analysis results are calculated.

2. The method for determining acid-insoluble aluminum in aluminum-magnesium-calcium alloy according to claim 1, characterized in that: The sample diameter is less than 0.100 mm.

3. The method for determining acid-insoluble aluminum in aluminum-magnesium-calcium alloy according to claim 1, characterized in that: The sample mass is 0.5 to 5.0000 g.

4. The method for determining acid-insoluble aluminum in aluminum-magnesium-calcium alloy according to claim 1, characterized in that: In the above step 1), the concentration of nitric acid is such that the volume ratio of nitric acid to water is 10% to 30%.

5. The method for determining acid-insoluble aluminum in aluminum-magnesium-calcium alloy according to claim 1, characterized in that: The magnetic stirring in step 1) is controlled to have a rotation speed between 60 and 240 r / min, a first stirring time of 3 to 12 h, a second stirring time of 0.5 to 2 h, and a standing time of 2 to 6 h.

6. The method for determining acid-insoluble aluminum in aluminum-magnesium-calcium alloy according to claim 1, characterized in that: The alkaline mixed flux is a mixture of sodium carbonate, boric acid and lithium tetraborate, wherein the sodium carbonate is 5%-50%, the boric acid is 5%-50% and the lithium tetraborate is 5%-50%.

7. The method for determining acid-insoluble aluminum in aluminum-magnesium-calcium alloy according to claim 1, characterized in that: In the above step 4), the concentration of nitric acid is such that the volume ratio of nitric acid to water is 20% to 70%.

8. The method for determining acid-insoluble aluminum in aluminum-magnesium-calcium alloy according to claim 1, characterized in that: The specific method of the above step 5) is: a. Prepare aluminum standard stock solution and develop standard solution working curve according to different aluminum standard stock solution concentrations; b. The sample solution was introduced into the inductively coupled plasma mass spectrometer via a peristaltic pump, and the working curve established using the prepared aluminum standard stock solution was tested and calculated; c. Use argon as the power gas, and the argon gas volume fraction is greater than 99.99%; d. Test the above step 4) obtained by analyzing the test solution and the blank test solution, the instrument automatically processes the data according to the working curve, calculates and outputs the mass concentration of aluminum; e. The content of aluminum element is expressed as the mass fraction of the element W Al Calculation, the value is expressed in %, according to formula (1): In formula (1): w Al ——Mass fraction of aluminum element to be measured; c0——the concentration of aluminum in the blank solution, in μg / mL; c1——mass concentration of aluminum in the sample solution, in μg / mL; V——total volume of test solution, in mL; m——mass of the sample, in g.

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