Method for determining silicon content in silicon steel by inductively coupled plasma emission spectrometry

Abstract

The invention relates to the field of detection methods, and particularly discloses a method for determining the silicon content in silicon steel through inductively coupled plasma emission spectrometry. The determination method comprises the following steps: preparing a to-be-tested solution: weighing 0.10-0.20 g of a silicon steel sample, adding 10-15mL of nitric acid (1 + 2), heating and dissolving at a low temperature, boiling for 10-60s, cooling to room temperature, keeping the temperature of the solution to be less than or equal to 80 DEG C, dropwise adding 3-5mL of hydrofluoric acid, and fixing the volume to obtain the to-be-tested solution; 0.095-0.19 g of metal iron is weighed and put into a polytetrafluoroethylene beaker, and the metal iron is dissolved according to the sample dissolving method in the prepared to-be-tested solution to obtain the Fe reference solution; making a standard curve: mixing the Si reference solution and the Fe reference solution with different volumes to prepare a standard solution in an analysis gradient range, and detecting and drawing the standard curve; and detecting the to-be-detected sample, and combining the standard curve to obtain the silicon content in the silicon steel sample. The method has the advantages of high accuracy, simplicity, convenience, rapidness and short detection period.

Description

Technical Field

[0001] The present application relates to the field of detection methods, and more specifically, to a method for determining silicon content in silicon steel by inductively coupled plasma emission spectroscopy. Background Art

[0002] Silicon alloy steel with a silicon content of 1.0-4.5%, a carbon content of less than 0.08%, and a metallic iron content of ≥90% is called silicon steel. Silicon steel is mainly used as a magnetic material in motors, transformers, electrical appliances, and electrical instruments. As the silicon content increases, the resistivity of silicon steel increases and the eddy current loss decreases; when the silicon content reaches 6.5%, the magnetic properties are optimal, mainly reflected in high resistivity, high magnetic permeability, low magnetocrystalline anisotropy, and magnetostriction coefficient close to zero. Especially at high frequencies, the core loss and noise pollution of high silicon steel are greatly reduced, and the advantages are very prominent. Therefore, it is particularly important to quickly and accurately measure the key element Si content.

[0003] The related technology discloses "ICP-OES method for determining silicon, manganese and phosphorus contents in silicon steel". This method places the sample in a polytetrafluoroethylene beaker, moistens it with a small amount of water, adds 5 mL of concentrated nitric acid for dissolution reaction, slowly drops 0.5 mL of hydrofluoric acid, dissolves it at low temperature, cools it, mixes it at fixed volume, and detects it with an inductively coupled plasma emission spectrometer. However, ICP-OES has the following problems: directly using concentrated nitric acid to dissolve the sample can easily cause sample passivation, resulting in incomplete dissolution or greatly increasing the dissolution time; directly adding 0.5 mL of hydrofluoric acid after the reaction will cause part of the silicon content to overflow in the form of silicon tetrafluoride, resulting in a low test result; at the same time, HF-H2SiF6-H2O is a ternary constant boiling system with a constant boiling point of 116°C. Only in the presence of excess hydrofluoric acid and when the solution temperature is controlled not to exceed 80°C, there will be no loss of silicon. Otherwise, H2SiF6 may decompose into silicon tetrafluoride and hydrofluoric acid during solution testing or storage, resulting in silicon loss; in addition, due to the different operating habits of different staff members, different analysis results may be obtained for the same sample.

[0004] Related technologies also disclose "Spark source atomic emission spectrometry for determination of high content of silicon and boron in iron-based amorphous alloys". This method uses a large number of international standard samples and a set of independently developed control samples to expand the curve, fit the curve, and directly analyze the sample on the spark source atomic emission spectrum. However, this method has high economic and technical costs and strict equipment requirements.

[0005] The related technology "Determination of silicon and boron in iron-based amorphous alloy iron-silicon-boron" established the method of determining the silicon content in iron-based amorphous alloy iron-silicon-boron by potassium fluorosilicate precipitation titration and determining the boron in iron-based amorphous alloy iron-boron-silicon by acid dissolution neutralization titration. However, this method uses more chemical reagents, has complicated steps, and has a long analysis cycle for a single person, about 2-3 days, and has high requirements for operation.

[0006] In view of the above-mentioned related technologies, the present invention discloses a method for determining the silicon content in silicon steel, which has high detection accuracy, short analysis cycle, low analysis cost and simple operation. Summary of the invention

[0007] In order to obtain a silicon content detection method with high detection accuracy, simple and fast operation and low analysis cost, the present application provides a method for determining the silicon content in silicon steel by inductively coupled plasma emission spectroscopy.

[0008] The present application provides a method for determining the silicon content in silicon steel by inductively coupled plasma emission spectroscopy using the following technical solution: A method for determining silicon content in silicon steel by inductively coupled plasma emission spectroscopy comprises the following steps: Prepare the test solution: weigh 0.10-0.20g silicon steel sample and place it in a polytetrafluoroethylene beaker, add 10-15mL nitric acid (1+2), heat and dissolve the silicon steel sample without boiling, boil for 10-60s after complete dissolution, and cool to room temperature; keep the solution temperature ≤80°C, add 3-5mL hydrofluoric acid until the precipitate is completely dissolved, transfer to a volumetric flask after cooling, and dilute to obtain the test solution; Prepare Fe reference solution: weigh 0.095-0.19g metallic iron into a polytetrafluoroethylene beaker, add 10-15mL nitric acid (1+2), heat and dissolve the metallic iron without boiling, boil for 10-60s after complete dissolution, and cool to room temperature; keep the solution temperature ≤80°C, add 3-5mL hydrofluoric acid dropwise until the precipitate is completely dissolved, transfer to a volumetric flask after cooling, and obtain Fe reference solution; repeat the operation to obtain several Fe reference solutions; Preparation of standard curve: several Fe standard solutions were mixed with different volumes of 0.5 mg / mL Si standard solutions to prepare standard solutions with different Si concentrations, and the solutions were detected by inductively coupled plasma emission spectrometer to draw a standard curve; Silicon content detection: The sample to be tested is detected by an inductively coupled plasma emission spectrometer, and the silicon content in the silicon steel sample is obtained in combination with the standard curve.

[0009] By adopting the above technical solution, the main form of silicon in silicon steel is FeSi, MnSi or FeMnSi, and a small part of silicon forms non-metallic inclusions, such as 2Fe.SiO 2 、2MnO.SiO 2 and Al 2 O 3 .SiO 2 ; When oxidizing nitric acid (1+2) is added, the following reactions mainly occur: 3FeSi+16HNO 3 =3Fe(NO 3 ) 3 +3H 4 SiO 4 +7NO↑+2H 2 O; The reaction formula of the dissolved sample reacting with hydrofluoric acid at ≤80℃ is as follows: H 4 SiO 4 +6HF=H 2 SiF 6 +4H 2 O; HF-H 2 SiF 6 -H 2 O is a ternary constant boiling system with a constant boiling point of 116°C; in the presence of excess hydrofluoric acid, when the solution temperature is controlled not to exceed 80°C, there will be no loss of silicon. The present application cools the dissolved sample to room temperature and adds excess hydrofluoric acid to minimize the loss of silicon, thereby avoiding the possibility of silicon overflowing in the form of silicon tetrafluoride when the solution temperature is greater than 80°C when hydrofluoric acid is added dropwise, thereby improving the accuracy of the analysis results.

[0010] In addition, the present application adopts silicic acid (1+2) to dissolve the silicon steel sample, avoiding the possibility of surface passivation of the silicon steel sample caused by concentrated nitric acid, avoiding the possibility of using high-concentration acids such as sulfuric acid, phosphoric acid, boric acid, etc. to affect the physicochemical efficiency and pollute the detection equipment, and avoiding the possibility of salt effect caused by alkaline fusion operation; the present application adopts silicic acid (1+2) to ensure the full dissolution of the silicon steel sample and is beneficial to reduce silicon loss.

[0011] Preferably, the nitric acid (1+2) is obtained by mixing concentrated nitric acid and water in a volume ratio of 1:2. The concentrated nitric acid is a nitric acid solution with a mass fraction of 65-68%.

[0012] Preferably, the step of heating with nitric acid (1+2) and dissolving the silicon steel sample or metallic iron without boiling also includes: adding water appropriately to ensure that the polytetrafluoroethylene beaker or the liquid in the polytetrafluoroethylene beaker covers the silicon steel sample or metallic iron.

[0013] By adopting the above technical scheme, the possibility of increasing the sample dissolution time and dissolution effect due to the increase of nitric acid concentration and enhanced oxidizing property caused by the evaporation of water vapor during the heating process, which may cause the surface of the test silicon steel sample to passivate and increase the possibility of the silicon steel sample leaving the nitric acid solution before being completely dissolved is avoided. At the same time, the overall boiling point can be lowered, and the possibility of nitric acid decomposition and consumption when the silicon steel sample is not completely dissolved is avoided.

[0014] Preferably, the step of using hydrofluoric acid to dissolve and precipitate specifically includes: adding hydrofluoric acid dropwise into the polytetrafluoroethylene beaker while shaking it, maintaining the solution temperature at ≤80°C during the adding process, and adding the remaining hydrofluoric acid after all the solution is dissolved, and shaking well.

[0015] Preferably, the preparation method of the 0.5 mg / mL Si standard solution comprises: Take 1.0698g of silicon dioxide and put it in a platinum crucible. Add 4g of sodium carbonate and mix well. Heat until completely melted. After cooling, dissolve in water. Transfer to a volumetric flask, make up to 1000mL, and mix well.

[0016] Preferably, the step of preparing a standard curve includes standard solutions with the following Si mass fractions: 0%, 0.50%, 1.50%, 3.00%, 5.00%, and 7.75%.

[0017] Preferably, the analysis conditions of the inductively coupled plasma emission spectrometer are: Analysis power 1150W, nebulizer flow 0.50L / min, pressure 2.10-2.30bar, auxiliary gas flow 0.50L / min, cooling gas flow 12.5 L / min, analysis pump speed 50rpm, hydrofluoric acid corrosion resistance system; analysis spectrum: Si 185.067nm.

[0018] Preferably, the metallic iron is high-purity iron with an iron mass fraction greater than 99.9%.

[0019] Preferably, the water is deionized water.

[0020] In summary, this application has the following beneficial effects: 1. Since the present application adopts oxidizing nitric acid (1+2) to dissolve the sample, the possibility of passivation of the surface of the silicon steel sample is reduced, which is conducive to promoting the rapid dissolution of the silicon steel sample.

[0021] 2. In the present application, an excess of hydrofluoric acid is added after the silicon steel sample is dissolved and cooled, and the solution temperature is kept ≤80°C during the hydrofluoric acid addition process, thereby avoiding the possibility of silicon element overflowing in the form of silicon tetrafluoride and improving the accuracy of the analysis result.

[0022] 3. This application only uses two low-concentration acids to dissolve the sample, avoiding the salt effect caused by alkali fusion acidification of the sample and the influence of adding high-concentration acid on the atomization efficiency.

[0023] 4. The method of the present application overcomes the salt effect problem caused by alkaline fusion acidification of the sample, solves the problem that Si is easily volatilized to a low level or partially generates silicate solids to block the capillary of the equipment during acid decomposition of high-Si steel, and has the advantages of high accuracy, simplicity, speed and short detection cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the standard curve in Example 1 of the present application. DETAILED DESCRIPTION

[0025] To further help understand the technical solution of the present invention, the technical solution of the present invention is described in more detail below by providing several specific implementation examples. All of these described embodiments are only partial embodiments of the present invention, not all of them. The following specific embodiments may be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments; and the reaction devices, monomer compounds, etc. involved in the following embodiments are all commercially available.

[0026] The following specific embodiments may be combined with each other, and the same or similar concepts or processes therein may not be described in detail in some embodiments.

[0027] The following examples are further explanations of the present invention, but the present invention is not limited thereto. Unless otherwise specified in the examples, the percentages are all by mass.

[0028] Example Example 1

[0029] This embodiment discloses a method for determining the silicon content in silicon steel by inductively coupled plasma emission spectroscopy, comprising the following steps: S1 Process the silicon steel samples into chips or flakes, with the mass of a single sample not exceeding 0.01g.

[0030] S2 Weigh 0.1g silicon steel sample (accurate to 0.0001g), place it in a 150mL polytetrafluoroethylene beaker, add 10mL nitric acid (1+2), heat at low temperature, dissolve the sample without boiling, observe the liquid in the beaker, and add deionized water as needed to ensure that the liquid covers the sample; boil for 50s after dissolution and cool to room temperature.

[0031] S3: Keep the solution temperature ≤80℃, add 4mL of hydrofluoric acid to the beaker while shaking. After the white precipitate is completely dissolved, add the remaining hydrofluoric acid and shake well.

[0032] S4 Transfer the dissolved test solution to a 100 mL plastic volumetric flask, add deionized water to make up to volume, and shake well to obtain the test solution.

[0033] S5: Weigh 1.0698 g of silicon dioxide (mass fraction ≥ 99.95%, calcined at 1000±50℃ for 1 h and cooled to room temperature) and place it in a platinum crucible. Add 4 g of standard sodium carbonate and mix well. Heat at 1000℃ until completely melted. Cool and dissolve in an appropriate amount of deionized water. Transfer to a 1000 mL plastic volumetric flask, make up to volume, and mix well to obtain a 0.5 mg / mL Si standard solution.

[0034] S6 Weigh 6 portions of 0.095g (accurate to 0.1mg) of high-purity metallic iron (mass fraction ≥99.98%) and place them in six polytetrafluoroethylene beakers, and dissolve them according to the methods of S2-S4 to obtain Fe standard solutions. After cooling, transfer them to plastic volumetric flasks and number them 1#-6#; Referring to Table 1, transfer different volumes of Si standard solution to the Fe standard solutions of 1#-6# to obtain standard solutions with the following silicon mass fractions.

[0035] Table 1

[0036] Analysis conditions of S7 inductively coupled plasma optical emission spectrometer: An iCAP PRO XP Duo inductively coupled plasma emission spectrometer was used with a radio frequency power of 1150 W, a nebulizer flow rate of 0.50 L / min, a pressure of 2.10-2.30 bar, an auxiliary gas flow rate of 0.50 L / min, a cooling gas flow rate of 12.5 L / min, an analysis pump speed of 50 rpm, and a hydrofluoric acid corrosion-resistant system; the analysis spectrum of the element to be measured was: Si, 185.067 nm.

[0037] After setting the analysis conditions and standard values, the standard solution in S6 is sucked into the spectrometer for detection, the emission light intensity is measured, and a standard curve is drawn. The standard curve is as follows: Figure 1 As shown, the linear coefficient is ≥0.9995.

[0038] S8 takes the test liquid in S4, uses an inductively coupled plasma emission spectrometer to detect, measures the luminescence intensity, and combines it with the standard curve of S7 to obtain the silicon content in the silicon steel sample; repeats the test 6 times, and calculates the average value, standard deviation and relative standard deviation of the test results.

[0039] The above method was used to test three silicon steel samples with different silicon contents, and the results are summarized in Table 2.

[0040] Table 2

[0041] It can be seen from Table 2 that, using the method disclosed in the present application, the standard deviation of the measurement results is ≤0.017, and the relative standard deviation is ≤0.37%, indicating that the standard curve has good precision and fully meets the requirements for Si analysis in silicon steel materials.

[0042] Example 2 This example verifies the accuracy of the analysis results of the method disclosed in the present application for determining the silicon content in silicon steel by inductively coupled plasma emission spectrometry.

[0043] 1. The method in Example 1 was used to test the silicon steel standard samples YSBC15329-94 (Si: 2.86%), YSBC15331-2013 (Si: 4.18%), and YSBC15335-94 (Si: 4.72%), and the results are summarized in Table 3. The silicon steel standard samples YSBC15329-94, YSBC15331-2013, and YSBC15335-94 in this example were all purchased from the market.

[0044] 2. The silicon steel sample 3 of Example 1 was tested using the national standard GB / T223.60-1997 "Chemical analysis methods for steel and alloys - Determination of silicon content by perchloric acid dehydration gravimetric method" and compared with the test results of Example 1. The results are summarized in Table 3.

[0045] Table 3

[0046] From Table 3, it can be seen that the method of determining the silicon content in silicon steel by inductively coupled plasma emission spectrometry in the present application has the advantages of good precision and high accuracy, and can be applied to the determination of Si content in silicon steel; and the detection cycle is short, simple and fast, and the detection cost is low, which is conducive to promotion and application.

[0047] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for determining the silicon content in silicon steel by inductively coupled plasma emission spectrometry, It is characterized in that The following steps are involved: Prepare the test solution: weigh 0.10-0.20g silicon steel sample and place it in a polytetrafluoroethylene beaker, add 10-15mL nitric acid (1+2), heat and dissolve the silicon steel sample without boiling, boil for 10-60s after complete dissolution, and cool to room temperature; keep the solution temperature ≤80°C, add 3-5mL hydrofluoric acid until the precipitate is completely dissolved, transfer to a volumetric flask after cooling, and dilute to obtain the test solution; Prepare Fe reference solution: weigh 0.095-0.19g metallic iron into a polytetrafluoroethylene beaker, add 10-15mL nitric acid (1+2), heat and dissolve the metallic iron without boiling, boil for 10-60s after complete dissolution, and cool to room temperature; keep the solution temperature ≤80°C, add 3-5mL hydrofluoric acid dropwise until the precipitate is completely dissolved, transfer to a volumetric flask after cooling, and obtain Fe reference solution; repeat the operation to obtain several Fe reference solutions; Preparation of standard curve: several Fe standard solutions were mixed with different volumes of 0.5 mg / mL Si standard solutions to prepare standard solutions with different Si concentrations, and the solutions were detected by inductively coupled plasma emission spectrometer to draw a standard curve; Silicon content detection: The sample to be tested is detected by an inductively coupled plasma emission spectrometer, and the silicon content in the silicon steel sample is obtained in combination with the standard curve.

2. The method for determining the silicon content in silicon steel by inductively coupled plasma emission spectrometry according to claim 1, It is characterized in that The nitric acid (1+2) is obtained by mixing concentrated nitric acid and water in a volume ratio of 1:

2.

3. The method for determining the silicon content in silicon steel by inductively coupled plasma emission spectrometry according to claim 1, It is characterized in that The step of heating with nitric acid (1+2) and dissolving the silicon steel sample or metallic iron without boiling also includes: adding water appropriately to ensure that the polytetrafluoroethylene beaker or the liquid in the polytetrafluoroethylene beaker covers the silicon steel sample or metallic iron.

4. The method for determining the silicon content in silicon steel by inductively coupled plasma emission spectrometry according to claim 1, It is characterized in that The step of using hydrofluoric acid to dissolve and precipitate specifically includes: adding hydrofluoric acid dropwise into the polytetrafluoroethylene beaker while shaking it, keeping the solution temperature ≤80°C during the adding process, and adding the remaining hydrofluoric acid after all the solution is dissolved, and shaking well.

5. The method for determining the silicon content in silicon steel by inductively coupled plasma emission spectrometry according to claim 1, It is characterized in that The preparation method of the 0.5 mg / mL Si standard solution comprises: Take 1.0698g of standard silica in a platinum crucible, add 4g of sodium carbonate and mix well, heat until completely melted, dissolve in water after cooling, transfer to a volumetric flask, make up to 1000mL, and mix well.

6. The method for determining the silicon content in silicon steel by inductively coupled plasma emission spectrometry according to claim 5, It is characterized in that The step of preparing the standard curve includes standard solutions having the following Si mass fractions: 0%, 0.50%, 1.50%, 3.00%, 5.00%, and 7.75%.

7. The method for determining the silicon content in silicon steel by inductively coupled plasma emission spectrometry according to claim 1, It is characterized in that The analysis conditions of the inductively coupled plasma emission spectrometer are: Analysis power 1150W, nebulizer flow 0.50L / min, pressure 2.10-2.30bar, auxiliary gas flow 0.50L / min, cooling gas flow 12.5 L / min, analysis pump speed 50rpm, hydrofluoric acid corrosion resistant system; the analysis spectrum of the element to be measured is: Si185.067 nm.

8. The method for determining the silicon content in silicon steel by inductively coupled plasma emission spectrometry according to claim 1, It is characterized in that The metallic iron is high-purity iron with an iron mass fraction greater than 99.9%.

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