Method for determining calcium fluoride content in flux for corrosion-resisting steel through ion chromatography

Abstract

The invention relates to the technical field of flux component determination, in particular to a method for determining the content of calcium fluoride in flux for corrosion-resisting steel through ion chromatography. The invention discloses a method for measuring the content of calcium fluoride in welding flux for corrosion-resisting steel through ion chromatography. The method comprises the following steps: S100, preparing a sample to be measured; s200, pretreating a to-be-detected sample, and preparing a diluted filtrate; s300, setting working parameters of the ion chromatograph; s400, calibrating an instrument, and determining by adopting an ion chromatograph; and S500, measuring the calcium fluoride content of the to-be-measured sample. The method for determining the content of calcium fluoride in the flux for corrosion-resisting steel through ion chromatography has the advantage that the welding quality is guaranteed. And the welding flux does not need to be subjected to experimental detection before welding, so that the welding flux is saved.

Description

Technical Field

[0001] This invention relates to the field of flux composition determination technology, and in particular to a method for determining the calcium fluoride content in flux for corrosion-resistant steel by ion chromatography. Background Technology

[0002] Calcium fluoride is an important component of welding flux, effectively reducing the high-temperature viscosity of slag, improving slag fluidity, enhancing weld formation, and improving the mechanical properties of weld metal. Under high temperatures, fluorine gas is generated, which combines with hydrogen atoms to form H₂F, which is then discharged from the molten pool, reducing the hydrogen content and the probability of hydrogen porosity. When the calcium fluoride content in the flux is below 5%, the aforementioned effects are not achieved; however, excessively high content leads to poor arc stability and affects weld formation. Therefore, the calcium fluoride content in the flux has a significant impact on weld performance. Accurate and rapid determination of its composition is of great guiding significance for weld quality monitoring and the safe service life of materials.

[0003] However, flux is usually purchased or customized and used directly, so the composition of the flux is rarely measured. The few instances where flux composition is measured primarily involve detecting substances produced after the flux is heated. For example, Chinese invention patent CN121199368A discloses a vacuum welding device and anti-oxidation method for streaming media audio chips. The device includes a main frame, a vacuum chamber module, an atmosphere control module, a laser module, a drive control module, an image detection module, and a composition detection module. The image and composition detection modules are integrated into a precision welding head. A microscope camera is used for positioning and morphology inspection before and after welding, and a Fourier transform infrared spectrometer is used to detect various gaseous components volatilized by the pre-coated flux in real time. By analyzing the proportional relationships of different gaseous components, the real-time welding temperature is calculated, and the laser power is controlled in a closed loop to accurately and stably stabilize the welding heat input. This method has low detection efficiency, and the measured components are those resulting from changes in the flux after heating. It cannot obtain the content of flux components before welding, especially the content of calcium fluoride, thus failing to guarantee welding quality. Experimental testing of the flux before welding resulted in a waste of flux. Summary of the Invention

[0004] In view of this, the present invention aims to provide a method for determining the calcium fluoride content in flux used for corrosion-resistant steel by ion chromatography. This method establishes an analytical method for calcium fluoride content in flux using an ion chromatograph, solving problems such as low detection efficiency, the determination of components that have changed after heating, the inability to obtain the content of flux components, especially calcium fluoride, before welding, thus failing to guarantee welding quality, and the waste of flux due to experimental testing before welding.

[0005] To address the above problems, the present invention provides a method for determining the calcium fluoride content in flux for corrosion-resistant steel by ion chromatography, comprising:

[0006] S100. Prepare the sample to be tested. Treat the corrosion-resistant steel flux sample into uniform granules, remove impurities, divide the sample into multiple portions, each with a mass of 10~20 g, sieve the sample through a 200-mesh sieve, dry it at a temperature of 105℃~110℃ for 1 hour, and then place it in a desiccator to cool to room temperature.

[0007] S200. Pre-treat the sample to be tested and prepare a diluted filtrate.

[0008] S300: Set the operating parameters of the ion chromatograph, use gradient elution, pass through a conductivity detector, set the column oven temperature to 30℃, and the volume of the quantitative injection loop to 25μL, and determine the quantitative value by peak area.

[0009] S400, instrument calibration, transfer fluoride ion standard solution to water and dilute to 100 mL, then serially dilute to prepare a series of standard solutions containing 0, 0.5, 1.0, 5.0 and 10.0 μg / mL of fluoride, and determine using an ion chromatograph;

[0010] S500: Determination of calcium fluoride content in the sample: Take 15 mL of water, push it through the H column, and let it stand flat for 15 min to fully activate it. Take 10 mL of the solution diluted in step S200 and push it into the activated H column. Discard the first 2 mL of filtrate, collect the remaining filtrate, and inject the filtrate into an ion chromatograph for analysis. Calculate the calcium fluoride content in the flux.

[0011] Furthermore, in step S100, the flux sample for corrosion-resistant steel is free of grease, metal surface contamination, brush bristles, and paper scraps.

[0012] Furthermore, in step S200, the method for preprocessing the sample to be tested includes:

[0013] S210. Weigh 4g of potassium sodium carbonate at the bottom of the crucible and weigh 0.1g of flux sample.

[0014] S220. Cover the sample with 2g of potassium sodium carbonate and incubate at 990℃ for 20 minutes.

[0015] S230, after taking it out, wash it with water and soak it, add 10 drops of ethanol, and make up to 200 mL in a volumetric flask;

[0016] S240, dry filter 30mL of filtrate and keep it. Take 2mL of filtrate and dilute it to a 100mL volumetric flask.

[0017] Furthermore, the resistivity of the water used for washing in step S200 is 18.25 MΩ·cm.

[0018] Furthermore, the gradient rinsing operating conditions in step S300 are as follows:

[0019] S310, rinsing time is 0-9 min, rinsing concentration is 2 mmol / L;

[0020] S320, rinsing time is 9-9.1 min, rinsing concentration is increased from 2 mmol / L to 50 mmol / L;

[0021] S330, rinsing time is 9.2-24 min, rinsing concentration is 50 mmol / L.

[0022] Furthermore, in step S300, the rinsing solution is potassium hydroxide, the flow rate is 1.0 mL / min, and the suppressor current is 99 mA.

[0023] Furthermore, the fluoride ion standard solution in step S400 is a GSB 04-2071-2007 type fluoride ion standard solution with a concentration of 100 μg / mL.

[0024] Furthermore, during instrument calibration in step S400, the determination steps for the series of standard solutions are consistent with those for the test samples.

[0025] Furthermore, in steps S400 and S500, the resistivity of the experimental water is 18.25 MΩ·cm.

[0026] Furthermore, before injecting the filtrate collected in step S500 into the ion chromatograph, ensure that the operating parameters of the ion chromatograph are consistent with the parameters set in step S300.

[0027] Compared with existing technologies, the method for determining the calcium fluoride content in flux for corrosion-resistant steel by ion chromatography described in this invention has the following advantages:

[0028] The advantage of this technical solution lies in the use of ion chromatography to establish an analytical method for the calcium fluoride content in the flux, which improves detection efficiency and accurately obtains the content of flux components, especially calcium fluoride, before welding, thus ensuring welding quality. It eliminates the need for experimental testing of the flux before welding, saving flux. Attached Figure Description

[0029] Figure 1 The images show ion chromatograms of fluoride at different eluent concentrations as described in the embodiments of this application.

[0030] Figure 2 This is an ion chromatogram of fluoride ions as described in the embodiments of this application;

[0031] Figure 3 The calibration curves of fluoride ions at different concentrations as described in the embodiments of this application;

[0032] Figure 4 Calibration curves of fluoride ions at different mass concentrations as described in the embodiments of this application;

[0033] Figure 5 This is a partial ion chromatogram before and after fluoride ion spiking, as described in the embodiments of this application. Detailed Implementation

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0035] In this invention, the terms "first," "second," "upper," and "lower," etc., are used for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," "upper," or "lower" may explicitly or implicitly include at least one of those features. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. Where the technical solutions of the embodiments can be combined, they are all within the scope of protection claimed by this invention.

[0036] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0037] A method for determining the calcium fluoride content in flux for corrosion-resistant steel by ion chromatography, comprising:

[0038] S100. Prepare the test sample. Treat the corrosion-resistant steel flux sample into uniform granules, remove impurities, and ensure that the corrosion-resistant steel flux sample is free of grease, metal surface contamination, brush lint, and paper scraps. Divide the sample into multiple portions, each weighing 10~20g. After sieving the sample through a 200-mesh sieve, dry it at 105℃~110℃ for 1 hour, and then place it in a desiccator to cool to room temperature.

[0039] S200. Pretreatment of the sample to be tested and preparation of diluted filtrate. Methods for pretreatment of the sample to be tested include:

[0040] S210. Take two platinum crucibles, weigh 4g of potassium sodium carbonate at the bottom of the crucible, and weigh 0.1g of flux sample (accurate to 0.0001g).

[0041] S220. Cover the sample with 2g of potassium sodium carbonate and incubate at 990℃ for 20 minutes.

[0042] S230, after taking it out, wash it with water and soak it. Add 10 drops of ethanol and make up to 200mL in a volumetric flask. The resistivity of the water used for washing is 18.25MΩ·cm.

[0043] S240, dry filter 30mL of filtrate and keep it for later use, take 2mL of filtrate and dilute it to a 100mL volumetric flask;

[0044] S300: Set the operating parameters of the ion chromatograph, use gradient elution, pass through a conductivity detector, set the column oven temperature to 30℃, and the volume of the quantitative injection loop to 25μL, and determine the quantitative value by peak area.

[0045] The working conditions for gradient rinsing are as follows:

[0046] S310, rinsing time is 0-9 min, rinsing concentration is 2 mmol / L;

[0047] S320, rinsing time is 9-9.1 min, rinsing concentration is increased from 2 mmol / L to 50 mmol / L;

[0048] S330, rinsing time is 9.2-24 min, rinsing concentration is 50 mmol / L.

[0049] The eluent was potassium hydroxide, the flow rate was 1.0 mL / min, and the suppressor current was 99 mA.

[0050] S400. Instrument calibration: The determination procedure for the series of standard solutions should be consistent with that for the test sample. Dilute the fluoride ion standard solution to 100 mL with water, and then serially dilute to prepare a series of standard solutions containing 0, 0.5, 1.0, 5.0, and 10.0 μg / mL of fluoride. The fluoride ion standard solution is GSB 04-2071-2007 type, with a concentration of 100 μg / mL. Determination is performed using an ion chromatograph.

[0051] S500: Determination of calcium fluoride content in the sample. Extract 15 mL of water, push it through an H-column, and allow it to stand for 15 minutes to fully activate. Take 10 mL of the diluted solution from step S200 and push it into the activated H-column. Discard the first 2 mL of filtrate, collect the remaining filtrate, and inject it into an ion chromatograph for analysis. Calculate the calcium fluoride content in the flux. Before injecting the collected filtrate into the ion chromatograph, ensure that the operating parameters of the ion chromatograph are consistent with the parameters set in step S300. The resistivity of the experimental water is 18.25 MΩ·cm.

[0052] The above method establishes an analytical method for the calcium fluoride content in welding flux using ion chromatography, improving detection efficiency and accurately obtaining the content of flux components, especially calcium fluoride, before welding, thus ensuring welding quality. It eliminates the need for pre-welding experimental testing of the flux, saving flux resources.

[0053] The above measurement method is illustrated below with specific examples.

[0054] Example 1

[0055] The instruments used in the determination method of this invention include a D10NEX AQUION ion chromatograph (HPIC, Thermo Fisher Scientific, USA), a Chromeleon 7 data acquisition system, GZY-P90-UV and GZY-PS-40-W laboratory ultrapure water systems (Hunan Kelton Water Co., Ltd.), a CP64 electronic analytical balance (Sartorius, Germany, d=0.1 mg), an Sx3-8-10ASP fiber ceramic resistance furnace, and a graphite constant temperature electric heating plate. Fluoride ion standard solution: GSB 04-2071-2007 (100 μg / mL, Steel Research Institute Nake Testing Technology Co., Ltd.), commercially available analytical grade potassium carbonate, analytical grade ethanol, fresh ultrapure water with a resistivity of 18.25 MΩ•cm, and high-purity nitrogen (φ(N2)≥99.99%).

[0056] Injection volume: Excessive injection volume may cause peak broadening, reducing resolution and requiring longer analysis time to achieve the desired separation. Therefore, selecting an appropriate injection volume while ensuring sensitivity is crucial. Considering the actual concentration and polarity of fluoride ions in the flux, preliminary experiments were conducted, and the final injection volume was determined to be [specific value missing].

[0057] 25 μL is a suitable temperature range that effectively reflects the true condition of the sample while ensuring both detection sensitivity and accuracy.

[0058] To further describe the operating parameters of this experimental method, such as mobile phase concentration, a PROD.COL.IP.AS18.4×250 mm anion exchange column and a PROD.COL.IP.AG18.4×50 mm anion exchange protectant were used to investigate the effect of mobile phase concentration on the separation of fluoride speciation. The column temperature was set at 30 °C, the flow rate at 1.0 mL / min, and the injection volume at 25 μL. Potassium hydroxide generated online by EGC was used as the eluent. The effects of eluent concentrations of 0.5, 1, 2, 5, 10, and 15 mmol / L on the separation and retention of fluoride ions were investigated, and the potassium hydroxide eluent concentration was optimized. The chromatographic separation behavior of fluoride under different eluent concentrations is shown below. Figure 1 As shown.

[0059] As the potassium hydroxide concentration increased from 0.5 mmol / L to 15 mmol / L, the shorter the retention time of fluoride ions, indicating faster desorption (elution) of fluoride ions adsorbed on the chromatographic column. In actual flux samples, in addition to fluoride ions, SiO2, Al2O3 (45-47%), CaCO3, MgO, and other matrix components are dissolved in the solution in ionic form and eluted, mainly occurring between 10-24 min. Therefore, when selecting the mobile phase concentration, it is essential to ensure that the fluoride ion peaks do not overlap with the matrix peaks and that the fluoride ion peak shape conforms to a normal distribution.

[0060] When the potassium hydroxide concentration was 0.5 mmol / L, the eluent concentration was too low to completely elute and separate fluoride ions. When the potassium hydroxide concentration was 1 mmol / L, the retention time of fluoride ions was 12.26 min, with a resolution of 4.19 against a similar matrix peak, indicating poor separation. When the potassium hydroxide concentration was 2 mmol / L, the retention time of fluoride ions was 7.89 min, with a resolution of 11.41 against a similar matrix peak. When the potassium hydroxide concentration was 5 mmol / L, the retention time of fluoride ions was 4.87 min, with a resolution of 1.89 against a similar matrix peak, requiring a longer matrix rinsing time. When the potassium hydroxide concentration was 10 mmol / L, the retention time of fluoride ions was 3.91 min, with a resolution of 3.43 against a similar matrix peak. When the potassium hydroxide concentration was 15 mmol / L, the retention time of fluoride ions was 3.91 min, with a resolution of 3.43 against a similar matrix peak. At a concentration of mmol / L, the retention time of fluoride ions was 3.59 min, and the resolution with the nearest matrix peak was 2.62. Therefore, when using a PROD.COL.IP.AS18.4×250 mm anion exchange column to separate calcium fluoride from flux, selecting 2 mmol / L potassium hydroxide as the mobile phase can separate fluoride ions from the sample within 9 min, demonstrating good separation performance. The experimental results of retention time and resolution of fluoride with adjacent peaks at different eluent concentrations are shown in Table 1 below.

[0061] Table 1

[0062]

[0063] The method calibration curve and limits of detection and quantitation were tested. Appropriate amounts of fluoride ion standard solution were diluted to 100 mL with ultrapure water, and then serially diluted to prepare a series of standard solutions containing 0, 0.5, 1.0, 5.0, and 10.0 μg / mL of fluoride. Following the experimental method, ion chromatography was used for determination. The characteristic peak of fluoride appeared at 7.89 min. The precision of the actual sample was good, and the method was stable. The obtained ion chromatogram of fluoride ions is shown below. Figure 2 As shown.

[0064] A standard curve was plotted with mass concentration (μg / mL) on the x-axis and peak area (μS·min) on the y-axis, as shown below. Figure 3and Figure 4 As shown. The fitted equation is y = 0.51629x + 0.01231, and the correlation coefficient is 0.9999.

[0065] The blank solution was measured 10 times in parallel according to the experimental method. The limit of detection and the limit of quantitation were calculated by 3 times and 10 times the standard deviation of the blank, respectively. The results are shown in Table 2 below. The limit of detection and the limit of quantitation of calcium fluoride were 0.0039 μg / L and 0.013 μg / L, respectively.

[0066] Table 2

[0067]

[0068] For the precision and accuracy tests of the method, four flux samples were selected, and the fluorine content in the samples was measured six times in parallel according to the experimental method to examine the precision of the method. The results are shown in Table 3 below. The relative standard deviation (RSD, n=6) of the actual sample measurement results was less than 3%, indicating that the method has good repeatability.

[0069] Table 3

[0070]

[0071] Recovery tests were performed under optimal chromatographic conditions. Ion chromatograms before and after fluoride ion spike are shown below. Figure 5 The total amount and recovery rate measured before and after spiked are shown in Table 4 below. The results show that the recovery rate of this method is 91.4-106.1%, the method has high accuracy, and can meet the testing requirements.

[0072] Table 4

[0073]

[0074] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for determining the calcium fluoride content in flux for corrosion-resistant steel by ion chromatography, characterized in that, include; S100. Prepare the sample to be tested. Treat the corrosion-resistant steel flux sample into uniform granules, remove impurities, divide the sample into multiple portions, each with a mass of 10~20 g, sieve the sample through a 200-mesh sieve, dry it at a temperature of 105℃~110℃ for 1 hour, and then place it in a desiccator to cool to room temperature. S200. Pre-treat the sample to be tested and prepare a diluted filtrate. S300: Set the operating parameters of the ion chromatograph, use gradient elution, pass through a conductivity detector, set the column oven temperature to 30℃, and the volume of the quantitative injection loop to 25μL, and determine the quantitative value by peak area. S400, instrument calibration, transfer fluoride ion standard solution to water and dilute to 100 mL, then serially dilute to prepare a series of standard solutions containing 0, 0.5, 1.0, 5.0 and 10.0 μg / mL of fluoride, and determine using an ion chromatograph; S500: Determination of calcium fluoride content in the sample: Take 15 mL of water, push it through the H column, and let it stand flat for 15 min to fully activate it. Take 10 mL of the solution diluted in step S200 and push it into the activated H column. Discard the first 2 mL of filtrate, collect the remaining filtrate, and inject the filtrate into an ion chromatograph for analysis. Calculate the calcium fluoride content in the flux.

2. The method for determining the calcium fluoride content in flux for corrosion-resistant steel by ion chromatography according to claim 1, characterized in that, The flux sample for corrosion-resistant steel in step S100 was free of grease, metal surface contamination, brush bristles, and paper scraps.

3. The method for determining the calcium fluoride content in flux for corrosion-resistant steel by ion chromatography according to claim 1, characterized in that, In step S200, the method for preprocessing the sample to be tested includes: S210. Weigh 4g of potassium sodium carbonate at the bottom of the crucible and weigh 0.1g of flux sample. S220. Cover the sample with 2g of potassium sodium carbonate and incubate at 990℃ for 20 minutes. S230, after taking it out, wash it with water and soak it, add 10 drops of ethanol, and make up to 200 mL in a volumetric flask; S240, dry filter 30mL of filtrate and keep it. Take 2mL of filtrate and dilute it to a 100mL volumetric flask.

4. The method for determining the calcium fluoride content in flux for corrosion-resistant steel by ion chromatography according to claim 3, characterized in that, The resistivity of the water used for washing in step S200 is 18.25 MΩ·cm.

5. The method for determining the calcium fluoride content in flux for corrosion-resistant steel by ion chromatography according to claim 1, characterized in that, The gradient rinsing working conditions in step S300 are as follows: S310, rinsing time is 0-9 min, rinsing concentration is 2 mmol / L; S320, rinsing time is 9-9.1 min, rinsing concentration is increased from 2 mmol / L to 50 mmol / L; S330, rinsing time is 9.2-24 min, rinsing concentration is 50 mmol / L.

6. The method for determining the calcium fluoride content in flux for corrosion-resistant steel by ion chromatography according to claim 1, characterized in that, In step S300, the rinsing solution is potassium hydroxide, the flow rate is 1.0 mL / min, and the suppressor current is 99 mA.

7. The method for determining the calcium fluoride content in flux for corrosion-resistant steel by ion chromatography according to claim 1, characterized in that, The fluoride ion standard solution in step S400 is a GSB 04-2071-2007 type fluoride ion standard solution with a concentration of 100 μg / mL.

8. The method for determining the calcium fluoride content in flux for corrosion-resistant steel by ion chromatography according to claim 1, characterized in that, During instrument calibration in step S400, the determination steps for the series of standard solutions are consistent with those for the test samples.

9. The method for determining the calcium fluoride content in flux for corrosion-resistant steel by ion chromatography according to claim 1, characterized in that, In steps S400 and S500, the resistivity of the experimental water is 18.25 MΩcm.

10. The method for determining the calcium fluoride content in flux for corrosion-resistant steel by ion chromatography according to claim 1, characterized in that, Before injecting the filtrate collected in step S500 into the ion chromatograph, ensure that the operating parameters of the ion chromatograph are consistent with the parameters set in step S300.

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