Method for measuring contents of molybdenum, copper and silicon in ferro-molybdenum alloy through X-ray fluorescence spectrometry

Abstract

The invention discloses a method for measuring the content of molybdenum, copper and silicon in ferro-molybdenum through X-ray fluorescence spectrometry. The method comprises the specific steps that S1, sample pretreatment and internal standard introduction are conducted; s2, oxidizing the sample by adopting a gradient oxidation method; s3, dynamically melting the composite flux; s4, preparing a standard fuse piece; and S5, carrying out multi-element cooperative calibration measurement. According to the method, the sample and the flux are accurately proportioned, a three-section melting procedure is adopted, a homogeneous-phase glass body is formed at high temperature, bubbles and segregation are avoided, the homogeneity of the fuse piece is remarkably improved, the influence of a mineral effect and a particle effect on a detection result is thoroughly eliminated, and high accuracy and high reproducibility of detection data are ensured; according to the method, the content of various elements such as molybdenum, copper and silicon in the ferro-molybdenum alloy can be measured at the same time, compared with a traditional method longer than 4 hours, the time consumed by the detection method is shortened to 40 minutes, the analysis period is greatly shortened, the detection efficiency is improved, the detection cost of a single sample is reduced by 50%, and the method is suitable for industrial batch detection requirements.

Description

Technical Field

[0001] The invention relates to the technical field of element content detection, and in particular to a method for determining the contents of molybdenum, copper and silicon in a molybdenum-iron alloy by using an X-ray fluorescence spectrometry method. Background Art

[0002] Ferromolybdenum is an alloy of molybdenum and iron, and its molybdenum content is usually between 50% and 65%. It is widely used as an alloy additive for steelmaking and a key raw material for military equipment. In the trading of ferromolybdenum alloy, the amount of molybdenum metal is used as the basis for settlement. Because of its high price, the accuracy of the determination of molybdenum content is extremely high. At present, the national standard GB / T 5059.1-2014 uses the lead molybdate weight method to determine the molybdenum content, which requires multiple steps such as acid dissolution → precipitation → burning → weighing. This method is cumbersome and lengthy. The single sample detection takes ≥4 hours and cannot meet the real-time control requirements of the smelting process. This method is highly dependent on the operator's experience and has a high risk of human error, such as incomplete precipitation, adsorption of impurities, etc. The actual RSD is generally >1%. In addition, it is impossible to simultaneously determine key impurity elements such as copper and silicon, and other additional methods such as ICP-AES are required, which further increases costs.

[0003] With the popularity of X-ray fluorescence spectrometer XRF, the tableting method combined with X-ray spectroscopy is also used for the determination of molybdenum content. However, due to the high hardness of molybdenum-iron alloy, the Mohs hardness is ≥6, which leads to uneven particle size distribution during sample preparation, causing serious mineral effect and particle size effect. Even if fine grinding is used to make the sample particles ≤325 mesh, the RSD is still as high as more than 2.0%, which makes it difficult to meet the accuracy requirements for the determination of molybdenum, copper and silicon contents. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for determining the molybdenum, copper and silicon contents in a molybdenum-iron alloy by X-ray fluorescence spectrometry, which solves the problems of easy corrosion of platinum yellow crucibles, low detection accuracy and long analysis cycle in the prior art, and provides an efficient and reliable analysis method for rapid and accurate detection of multi-element contents in molybdenum-iron alloys.

[0005] The technical solution adopted by the present invention is:

[0006] S1: sample preparation and internal standard introduction; Mix 0.2000±0.0001 g of molybdenum-iron alloy sample and 0.4000±0.0001 g of niobium pentoxide internal standard and place them in a platinum crucible; S2: Sample oxidation is performed using a gradient oxidation method; Wet the sample with deionized water, add 2.0-3.0 mL of concentrated nitric acid dropwise, and heat in an electric furnace until evaporated to dryness; Transfer the crucible to a muffle furnace and burn at 500°C for 10 minutes to ensure that molybdenum is completely converted into molybdenum trioxide and eliminate the interference of sulfur and carbon; S3: dynamic melting of composite flux; Weigh 6.0000±0.0001 g of lithium tetraborate-lithium metaborate composite flux with a mass ratio of 67:33, add 0.2500±0.0001 g of potassium bromide-ammonium iodide composite release agent, and adopt a three-stage melting program at 1100°C: 3 min static pre-melting stage → 15 min main melting stage, swing frequency 20 times / min → 1 min homogenization stage, let stand to eliminate bubbles; After the melt is cooled, a homogeneous glass body without cracks or crystallization is formed on the surface, and the X-ray fluorescence detection surface does not need to be polished; S4: Standard fused sheet preparation; According to steps S1-S3, prepare no less than 10 working curve standard frits covering different gradient contents of each element; S5: multi-element co-calibration determination; The working curve standard melt was measured using an X-ray fluorescence spectrometer. Each sample was measured at least twice. The instrument software was used to calculate and draw the working curve using the molybdenum, copper, and silicon content in the standard substance as the horizontal axis and the average fluorescence intensity as the vertical axis. The fluorescence intensity ratio of molybdenum to niobium was used for molybdenum. In order to eliminate the interference of Mo-Lβ on Si-Kα, the silicon working curve was regressed using the absorption influence coefficient dj method. The working curve is selected to measure the sample melt to be analyzed, and the contents of molybdenum, copper and silicon in the sample to be analyzed are calculated according to the corresponding relationship between the intensity of the analysis spectrum and the concentration; Working curve coverage range: Mo 50-65%, Copper 0.01-1.5%, Silicon 0.1-3.0%.

[0007] Specifically, the particle size of the molybdenum-iron alloy sample in S1 is 180-200 mesh.

[0008] Specifically, the temperature of the electric furnace during the oxidation process in S2 is not higher than 150°C.

[0009] Specifically, the composite release agent is prepared by potassium bromide and ammonium iodide in a mass ratio of 4:1; it can reduce the surface tension of the melt and avoid shrinkage of the edge of the melt.

[0010] Specifically, the working conditions of the X-ray fluorescence spectrometer are: rhodium target X-ray tube 50 kV / 60 mA, PET crystal is used for silicon measurement, LiF200 crystal is used for copper, and Ge crystal is used for molybdenum.

[0011] Due to the adoption of the above-mentioned technical solution, the present invention has the following advantages:

[0012] The present invention optimizes the sample pretreatment and melting sample preparation process, adopts nitric acid for gradient oxidation method, and the nitric acid low-temperature oxidation treatment converts the elements in the molybdenum-iron alloy from a reduced state to a stable oxidized state, thereby ensuring that the sample is completely converted to an oxidized state before melting, avoiding volatilization or residue of elements, making the sample more uniform and stable during the melting process, and fundamentally avoiding the risk of crucible corrosion during high-temperature melting, significantly extending the service life of the crucible, and reducing equipment maintenance costs; the sample and the flux are accurately proportioned, and a three-stage melting procedure is adopted to form a homogeneous glass body at high temperature without bubbles and segregation, thereby significantly improving the homogeneity of the melt, completely eliminating the influence of mineral effect and particle effect on the test results, and ensuring the test results. High accuracy and high reproducibility of test data; compound release agent can reduce the surface tension of the melt and avoid shrinkage of the edge of the melt; through the internal standard-melting combination technology of Nb2O5 internal standard and composite flux, the molybdenum detection RSD≤0.50%, which is significantly improved compared with the traditional weight method RSD>1%; and it solves the detection problem of trace Cu / Si in high molybdenum matrix, and significantly improves the precision and reliability of the test results; it can simultaneously determine the contents of multiple elements such as molybdenum, copper, silicon, etc. in molybdenum-iron alloy. Compared with the traditional method of more than 4 hours, the detection method of the present invention is shortened to 40 minutes, which greatly shortens the analysis cycle, improves the detection efficiency, reduces the single sample detection cost by 50%, and is suitable for industrial batch detection needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 1 is a working curve of the fluorescence intensity ratio of molybdenum to niobium according to an embodiment of the present invention.

[0014] Figure 2 It is the copper working curve of the embodiment of the present invention.

[0015] Figure 3 It is the silicon working curve of the embodiment of the present invention. DETAILED DESCRIPTION

[0016] The present invention will be further explained below in conjunction with the embodiments, which are not intended to limit the protection scope of the present invention. The purpose of disclosing the present invention is to protect all technical improvements within the scope of the present invention.

[0017] A method for determining the content of molybdenum, copper and silicon in molybdenum-iron alloy by X-ray fluorescence spectrometry, the specific steps are: S1: sample preparation and internal standard introduction; After crushing, the molybdenum-iron alloy was ground to 180-200 meshes in a planetary ball mill to ensure uniform particle size; 0.2000±0.0001 g of molybdenum-iron alloy sample was weighed and mixed with 0.4000±0.0001 g of niobium pentoxide internal standard and placed in a platinum crucible; the composition of the platinum crucible was: 95% Pt-5% Au; the addition of Nb2O5 could correct the matrix effect, and the Lβ1 spectrum of Nb had no overlapping interference with Mo-Lα.

[0018] S2: Sample oxidation is performed using a gradient oxidation method; Wet the sample with deionized water, add 2.0 mL of concentrated nitric acid dropwise, and heat in an electric furnace until evaporated to dryness; the temperature of the electric furnace is ≤150°C; The crucible was transferred to a muffle furnace and calcined at 500°C for 10 minutes to ensure that Mo was completely converted into MoO3 and eliminate interferences such as sulfur and carbon; Nitric acid has strong oxidizing properties and can effectively oxidize the reducing substances in the sample and convert them into stable oxides. Through gradient oxidation: nitric acid + high temperature burning, MoO3 volatilization loss is avoided, the recovery rate is greater than 99.5%, and the crucible is prevented from being corroded during the high temperature melting process; Table 1 is a comparison table of nitric acid addition tests; Table 1: Comparison of nitric acid dosage tests Nitric acid dosage Crucible corrosion Fused film transparency applicability 0.5 mL serious opaque not applicable 1.5 mL slight More transparent Critical value 2.0 mL none Smooth and transparent optimal 3.0 mL none Smooth and transparent excess

[0019] S3: Dynamic melting of composite flux Weigh 6.0000±0.0001 g of lithium tetraborate-lithium metaborate composite flux with a mass ratio of 67:33, add 0.2500±0.0001 g of potassium bromide-ammonium iodide composite release agent, and adopt a three-stage melting program at 1100°C: 3 min static pre-melting stage → 15 min main melting stage, swing frequency 20 times / min → 1 min homogenization stage, let stand to eliminate bubbles; After the melt is cooled, a homogeneous glass body without cracks or crystallization is formed on the surface, and the X-ray fluorescence detection surface does not need to be polished; When the amount of the composite release agent added was 0.2g-0.3g, no bubbles were generated in the prepared glass frit, and the demoulding success rate was 100%. The experimental results are shown in Table 2. Table 2: Comparison of compound release agent dosage test Serial number 1 2 3 4 5 Composite release agent 0.1g 0.15g 0.2g 0.25g 0.3g bubble have have none none none Demolding effect Disaster Disaster easy easy easy The three-stage melting was tested, and the standard values ​​of Mo, Cu, and Pb elements in the molybdenum iron standard sample YSBC37653-10 were compared with the sample state. The experimental results are shown in Table 3; Table 3: Fused piece quality verification comparison table

[0020] Note: 3min is the pre-melting time, 15min is the melting time, and 1min is the standing time.

[0021] According to the experimental results, the temperature and time of 1100℃+15 min are optimized, the fused sheet has no black impurities of unmelted particles, the deviation between the measured Mo value and the standard value is ≤0.5%, the surface of the molybdenum-iron fused sheet is smooth and transparent, and its measured value is highly consistent with the standard value, indicating that the method has good accuracy and reliability.

[0022] S4: Standard Fused Plate Preparation According to steps S1-S3, prepare no less than 10 working curve standard frits covering different gradient contents of each element.

[0023] S5: multi-element co-calibration determination; The working curve standard melt was measured using an X-ray fluorescence spectrometer. Each sample was measured at least twice. The instrument software was used to calculate and draw the working curve using the molybdenum, copper, and silicon content in the standard substance as the horizontal axis and the average fluorescence intensity as the vertical axis. The fluorescence intensity ratio of molybdenum to niobium was used for molybdenum. In order to eliminate the interference of Mo-Lβ on Si-Kα, the silicon working curve was regressed using the absorption influence coefficient dj method. The working curve is selected to measure the sample melt to be analyzed, and the contents of molybdenum, copper and silicon in the sample to be analyzed are calculated according to the corresponding relationship between the intensity of the analysis spectrum and the concentration; Working curve coverage range: Mo 50-65%, Copper 0.01-1.5%, Silicon 0.1-3.0%.

[0024] In order to avoid the interference of Fe Kβ in molybdenum-iron alloy on molybdenum spectrum, the present invention selects Lα series spectrum of molybdenum as the analysis line of the main element, and at the same time, uses niobium, which is adjacent to Mo atomic number and has similar energy absorption intensity, as the internal standard element, and selects Lβ1 series spectrum of Nb for correction. This method effectively reduces the influence of matrix effect and instrument deviation, and significantly improves the precision and accuracy of the test data. The specific instrument measurement conditions are shown in Table 4 below: Table 4: X-ray fluorescence measurement conditions element Analyze spectral lines Crystal 2θ analysis line Pipe pressure / KV Tube flow / mA detector PHA Element intensity counting time / s Background intensity counting time / s Mo Mo Lα Ge 111.70 50 60 FPC 22-72 30 / Si Si Kα PET 108.78 30 100 FPC 26-74 20 10 Cu Cu Kα LiF200 44.98 50 60 SC 24-78 10 10 Nb Nb Lβ1 LiF200 114.42 50 60 SC 24-72 20 / In this embodiment, three ferromolybdenum samples were taken and marked as 1# ferromolybdenum sample, 2# ferromolybdenum sample, and 3# ferromolybdenum sample, respectively. According to the steps and methods in this embodiment, the same ferromolybdenum sample was repeatedly measured 7 times to obtain the percentage contents of molybdenum, copper, and silicon of 1# ferromolybdenum sample, 2# ferromolybdenum sample, and 3# ferromolybdenum sample as shown in the following table: Table 5 shows the precision of molybdenum Sample No. 1st time 2nd time 3rd 4th 5th 6th 7th average value / % RSD / % 1# 52.31 52.15 52.34 52.21 52.40 52.39 52.45 52.32 0.21 2# 58.42 58.55 58.48 58.28 58.36 58.28 58.56 58.42 0.20 3# 63.32 63.25 63.58 63.47 63.29 63.39 63.40 63.39 0.18 Table 6 shows the precision of copper Sample No. 1st time 2nd time 3rd 4th 5th 6th 7th average value / % RSD / % 1# 0.85 0.84 0.83 0.85 0.84 0.84 0.83 0.84 0.97 2# 0.57 0.59 0.57 0.59 0.57 0.58 0.59 0.58 1.72 3# 0.032 0.033 0.034 0.034 0.032 0.032 0.034 0.033 3.03 Table 7 shows the precision of silicon Sample No. 1st time 2nd time 3rd 4th 5th 6th 7th average value / % RSD / % 1# 2.13 2.10 2.09 2.13 2.16 2.18 2.07 2.12 1.84 2# 0.89 0.87 0.91 0.86 0.88 0.86 0.90 0.88 2.21 3# 0.13 0.14 0.12 0.13 0.13 0.12 0.13 0.13 5.37

[0025] From the precision data in Tables 5, 6, and 7, we can conclude that: Mo: RSD≤0.21% (n=7), which is much better than the RSD>1% of the lead molybdate weight method; Copper, Silicon: RSD≤5.37%, which meets the element detection requirements; This shows that the detection method of the present invention has excellent precision and stability, especially in the detection of the major element molybdenum, the relative standard deviation of which is less than 0.5%, which significantly improves the accuracy and reliability of the analysis results.

[0026] The method of the present invention is used to measure molybdenum-iron standard samples, including metallurgical standard samples YSBC37652-10, YSBC37653-10 and national standard sample GSB03-1689-2014; as shown in Table 8, the measured fluorescence values ​​are highly consistent with the standard values ​​of molybdenum, copper and silicon in the standard samples, indicating that the method has high accuracy and reliability.

[0027] Table 8 Comparison of molybdenum, copper and lead content with standard samples Sample name serial number Standard value Mo% Fluorescence value Mo% error% Standard value Cu% Fluorescence value Cu% error% Standard value Si% Fluorescence value Si% error% Ferromolybdenum(standard sample) YSBC37652-10 61.41 61.50 -0.11 0.126 0.128 -0.002 — — — Ferromolybdenum(standard sample) GSB03-1689-2014 64.84 64.80 -0.04 0.33 0.32 0.01 0.002 0.002 0.000 Ferromolybdenum(standard sample) YSBC37653-10 57.65 57.66 0.01 0.117 0.108 0.009 0.71 0.68 0.03

[0028] Parts of the present invention not described in detail are prior art.

[0029] The embodiments selected herein for the purpose of disclosing the invention are currently considered to be suitable, but it should be understood that the invention is intended to include all changes and modifications of the embodiments that fall within the scope of the concept and invention.

Claims

1. A method for determining the content of molybdenum, copper and silicon in ferromolybdenum alloy by X-ray fluorescence spectrometry, characterized in that: The specific steps are: S1: sample preparation and internal standard introduction; Mix 0.2000±0.0001 g of molybdenum-iron alloy sample and 0.4000±0.0001 g of niobium pentoxide internal standard and place them in a platinum crucible; S2: Sample oxidation is performed using a gradient oxidation method; Wet the sample with deionized water, add 2.0-3.0 mL of concentrated nitric acid dropwise, and heat in an electric furnace until evaporated to dryness; Transfer the crucible to a muffle furnace and burn at 500°C for 10 minutes; S3: dynamic melting of composite flux; Weigh 6.0000±0.0001 g of lithium tetraborate-lithium metaborate composite flux with a mass ratio of 67:33, add 0.2500±0.0001 g of potassium bromide-ammonium iodide composite release agent, and adopt a three-stage melting program at 1100°C: 3 min static pre-melting stage → 15 min main melting stage, swing frequency 20 times / min → 1 min homogenization stage, let it stand to eliminate bubbles; S4: Standard fused sheet preparation; According to steps S1-S3, prepare no less than 10 working curve standard frits covering different gradient contents of each element; S5: multi-element co-calibration determination; The working curve standard melt was measured using an X-ray fluorescence spectrometer. Each sample was measured at least twice. The instrument software was used to calculate and draw the working curve using the content of molybdenum, copper and silicon in the standard substance as the horizontal axis and the average value of the measured fluorescence intensity as the vertical axis. The fluorescence intensity ratio of molybdenum to niobium was used for molybdenum. The absorption influence coefficient DJ method was used to regress and correct the silicon working curve. The working curve is selected to measure the sample melt to be analyzed, and the contents of molybdenum, copper and silicon in the sample to be analyzed are calculated according to the corresponding relationship between the intensity of the analysis spectrum and the concentration; Working curve coverage range: Mo 50-65%, Copper 0.01-1.5%, Silicon 0.1-3.0%.

2. The method for determining the content of molybdenum, copper and silicon in ferromolybdenum alloy by X-ray fluorescence spectrometry according to claim 1, characterized in that: The particle size of the molybdenum-iron alloy sample in S1 is 180-200 mesh.

3. The method for determining the content of molybdenum, copper and silicon in ferromolybdenum alloy by X-ray fluorescence spectrometry according to claim 1, characterized in that: The temperature of the electric furnace during the oxidation process in S2 is not higher than 150°C.

4. The method for determining the content of molybdenum, copper and silicon in ferromolybdenum alloy by X-ray fluorescence spectrometry according to claim 1, characterized in that: The composite release agent is prepared by mixing potassium bromide and ammonium iodide in a mass ratio of 4:

1.

5. The method for determining the content of molybdenum, copper and silicon in ferro-molybdenum alloy by X-ray fluorescence spectrometry according to claim 1, characterized in that: The working conditions of the X-ray fluorescence spectrometer are: rhodium target X-ray tube 50 kV / 60 mA, PET crystal for silicon measurement, LiF200 crystal for copper, and Ge crystal for molybdenum.

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