Method for detecting lead and bismuth elements in aluminum alloy based on direct-reading spectrometer standard sample joint control

Abstract

The invention discloses a method for detecting lead and bismuth elements in aluminum alloy based on direct-reading spectrometer standard sample joint control, and relates to the field of detection of lead and bismuth elements in aluminum alloy, the method comprises the following operation steps: S1, preparing a sample to be detected; s2, selection and pretreatment of a standard sample; s3, initializing a spectrograph system; s4, double-standard-sample joint control calibration is carried out; s5, detecting a sample to be detected; and S6, result verification and precision control. According to the method for detecting the lead and bismuth elements in the aluminum alloy based on direct-reading spectrometer standard sample joint control, the detection blind area of a traditional direct-reading spectrometer on the low-content lead and bismuth elements is broken through, spectral interference caused by the matrix effect is eliminated through a double-standard-sample joint control mechanism, system errors are greatly reduced, and the detection accuracy is improved. According to the method, the consistency of detection results of different batches and different operators can be guaranteed, meanwhile, the limitation on the surface roughness of the sample is relaxed, the grinding time and the equipment loss are reduced, and the detection efficiency is multiplied through parallel calibration and detection steps.

Description

Technical Field

[0001] The present invention relates to the field of detection of lead and bismuth elements in aluminum alloys, and particularly relates to a method for detecting lead and bismuth elements in aluminum alloys based on the control of standard samples by a direct-reading spectrometer. Background Art

[0002] Lead and bismuth elements are usually added to aluminum alloys to improve the cutting performance of products. A high content of lead elements will reduce the strength and ductility of aluminum alloys, and at the same time cause hot brittleness. A high content of bismuth elements will reduce the toughness. During element detection, the contents of lead and bismuth elements also need to be detected. The aluminum alloy used in this product requires that the lead and bismuth contents are less than 30 ppm. A spectrometer using a channel photomultiplier (CPM) detector can measure a minimum of 5 ppm of lead and bismuth, but it is expensive and not suitable for products with low production capacity. In the production process, a spectrometer with a lower price will be used for detection. However, when using a direct-reading spectrometer to detect element contents, standard samples need to be used for calibration, and the corresponding standard samples of aluminum alloys cannot detect lead and bismuth with low contents. The traditional detection scheme uses a spectrometer with a channel photomultiplier detector, which can detect a minimum of 5 ppm of Pb and Bi. However, the equipment is expensive and not suitable for small and medium-sized production lines. Moreover, the Bi element is missing in the aluminum alloy standard sample (such as EK6061), and the Pb element content is marked as an estimated value (0.0043%), which cannot meet the accurate calibration requirements of low-content elements, resulting in significant deviations in detection results. Summary of the Invention

[0003] The main purpose of the present invention is to provide a method for detecting lead and bismuth elements in aluminum alloys based on the control of standard samples by a direct-reading spectrometer, which can effectively solve the problems in the background art. To achieve the above purpose, the technical solution adopted by the present invention is as follows: A method for detecting lead and bismuth elements in aluminum alloys based on the control of standard samples by a direct-reading spectrometer includes the following operating steps: S1: Preparation of the sample to be measured. Prepare aluminum alloy 6061 after forging and machining of an aluminum ingot. Use sandpaper with a mesh size of more than 120 to polish the surface of aluminum alloy 6061, thoroughly remove the oxide layer, ensure that the detection surface of aluminum alloy 6061 is flat and smooth, cover its size with the excitation area of the spark table, ultrasonically clean it with acetone and absolute ethanol for 3 minutes in sequence, and then dry it with nitrogen. S2: Selection and pretreatment of standard samples. Prepare a standard sample combination, including EK6061 and pure aluminum 0607, and perform surface grinding and cleaning on it synchronously with the sample to be measured to ensure consistent excitation conditions. S3: Initialization of the spectrometer system, including equipment configuration: a direct-reading spectrometer equipped with a CMOS detector; the excitation source is a high-voltage spark generator with an energy parameter of 8-10 J; the light chamber environment is a constant temperature of 25 ± 0.5 °C, and the purity of argon is ≥ 99.999%. Environmental control: argon pressure is 0.55 MPa; laboratory temperature and humidity are 23 ± 1 °C; optical path stabilization time is preheating ≥ 2 hours; S4: Dual standard sample control calibration, including primary standard sample calibration: In the instrument software, select the "type standardization" module, input the elemental certification values of the EK6061 standard sample, continuously excite the standard sample 3 times, and take the average light intensity to establish the calibration curve for major elements; Trace standard sample calibration: Create a new "additional calibration" channel, select Pb and Bi elements, input the elemental certification values of pure aluminum 0607, excite 3 times, and generate the exclusive calibration curves for Pb and Bi; S5: Detection of samples to be tested. Place the sample to be tested on the spark table, ensure airtightness, and set the excitation parameters: pre-ignition time: 5 seconds, used to remove the surface interference layer; integration time: 10 seconds, used to ensure the acquisition of trace element signals; Start excitation, collect the intensities of characteristic spectral lines: Pb characteristic spectral line: 283.306 nm; Bi characteristic spectral line: 306.772 nm, and then automatically call the control calibration curve to calculate the element content; S6: Result verification and precision control. Continuously detect the same sample 5 times and calculate the relative standard deviation. Preferably, in the S1, the elemental certification values of aluminum alloy 6061 in wt% are Si 0.69%, Fe 0.18%, Cu 0.25%, Mn 0.1%, Mg 0.98%, Cr 0.22%, Zn 0.013%, Ti 0.031%, Pb 0.0006%, Bi 0.0016%, and its surface roughness Ra ≤ 6.3 μm. Preferably, in the S2, for EK6061, Southwest Aluminum is selected, and its elemental certification values are: Si 0.729 ± 0.01 wt%, Fe 0.196 ± 0.005 wt%, Cu 0.291 ± 0.008 wt%, Pb 0.0043 ± 0.0005 wt%; for pure aluminum 0607, Fushun Aluminum Factory is selected, and its elemental certification values are: Pb 0.0076 ± 0.0003 wt%, Bi 0.0033 ± 0.0002 wt%. Preferably, in the S2, before using each batch of standard samples, they need to be verified by a spark direct-reading spectrometer. The light intensity fluctuation of major elements ≤ 5%. If it exceeds the tolerance, the standard sample is invalidated. Preferably, in the S6, when continuously detecting the same sample to be tested 5 times, the relative standard deviation of Pb and Bi needs to be ≤ 5%. If it exceeds the tolerance, re-execute the steps of S3. At the same time, randomly select 1 tenth of the samples for retesting by ICP-MS. It is required that when the content ≥ 20 ppm, the result of the direct-reading spectrometer ≤ 8%, and when the content < 20 ppm, the absolute value difference ≤ 2 ppm. Compared with the prior art, the present invention provides a method for detecting lead and bismuth elements in aluminum alloy based on the control of standard samples by a direct-reading spectrometer, which has the following beneficial effects: 1. The method for detecting lead and bismuth elements in aluminum alloy based on the control of standard samples by a direct-reading spectrometer can improve the detection accuracy. The detection lower limit of Pb / Bi reaches 10 ppm, which is better than the 30 ppm lower limit of conventional spectrometers. The relative error is ≤15%, meeting the requirements of industrial quality control. Using a CMOS spectrometer to replace CPM equipment can effectively reduce the overall detection cost, and at the same time, the detection cost of a single sample can also be effectively reduced. 2. The method for detecting lead and bismuth elements in aluminum alloy based on the control of standard samples by a direct-reading spectrometer shortens the control calibration process to 20 minutes, supports on-line detection in the production line, and can complete the analysis of 15 samples per hour. This method can also be adapted to the operating systems of mainstream spectrometers such as ARL and OBLF. By adjusting the standard sample combination, it can be extended to other aluminum alloys, such as 7075, 5052 and elements Sb, Sn, etc. 3. The method for detecting lead and bismuth elements in aluminum alloy based on the control of standard samples by a direct-reading spectrometer breaks through the detection blind area of traditional direct-reading spectrometers for low-content lead and bismuth elements, successfully quantifies trace components at the 10 ppm level, eliminates spectral interference caused by matrix effects through a double-standard sample control mechanism, greatly reduces systematic errors, establishes a calibration system resistant to environmental fluctuations, ensures the consistency of detection results for different batches and different operators, at the same time relaxes the restrictions on the surface roughness of samples, reduces polishing time and equipment wear, and doubles the detection efficiency by parallelizing the calibration and detection steps. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flowchart of the present invention. DETAILED DESCRIPTION OF THE INVENTION In order to make the technical means, creative features, achieved purposes and functions of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments. Example 1: As Figure 1 shown, the method for detecting lead and bismuth elements in aluminum alloy based on the control of standard samples by a direct-reading spectrometer includes the following operation steps: S1: Preparation of the sample to be tested. Prepare aluminum alloy 6061 after forging and machining of an aluminum ingot. Polish the surface of the aluminum alloy 6061 with sandpaper of 120 mesh or above to thoroughly remove the oxide layer, ensuring that the detection surface of the aluminum alloy 6061 is flat and smooth. Cover the spark table excitation area with its size. Ultrasonically clean it with acetone and absolute ethanol for 3 minutes in sequence, and then dry it with nitrogen. The elemental certification values of the aluminum alloy 6061 in wt% are Si 0.69%, Fe 0.18%, Cu 0.25%, Mn 0.1%, Mg 0.98%, Cr 0.22%, Zn 0.013%, Ti 0.031%, Pb 0.0006%, Bi 0.0016%, and its surface roughness Ra ≤ 6.3 μm; S2: Standard sample selection and pretreatment. Prepare a standard sample combination, including EK6061 and pure aluminum 0607. Synchronously polish and clean their surfaces with the sample to be tested to ensure consistent excitation conditions. For EK6061, select Southwest Aluminum, and its elemental certification values are: Si 0.729 ± 0.01 wt%, Fe 0.196 ± 0.005 wt%, Cu 0.291 ± 0.008 wt%, Pb 0.0043 ± 0.0005 wt%; for pure aluminum 0607, select Fushun Aluminum Factory, and its elemental certification values are: Pb 0.0076 ± 0.0003 wt%, Bi 0.0033 ± 0.0002 wt%. Before using each batch of standard samples, verify them through a spark direct-reading spectrometer. The light intensity fluctuation of the major elements is ≤ 5%. If it exceeds the tolerance, the standard sample is invalidated; S3: Initialization of the spectrometer system, including equipment configuration: a direct-reading spectrometer equipped with a CMOS detector; the excitation source is a high-voltage spark generator with an energy parameter of 8 - 10 J; the light chamber environment is a constant temperature of 25 ± 0.5 °C, and the argon purity ≥ 99.999%; Environmental control: the argon pressure is 0.55 MPa; the laboratory temperature and humidity are 23 ± 1 °C; the light path stabilization time is ≥ 2 hours for preheating; S4: Dual-standard sample joint control calibration, including primary standard sample calibration: Select the "type standardization" module in the instrument software, input the elemental certification values of the EK6061 standard sample, continuously excite the standard sample 3 times, and take the average light intensity to establish a calibration curve for the major elements; Trace standard sample calibration: Create an "additional calibration" channel, select the Pb and Bi elements, input the elemental certification values of pure aluminum 0607, and excite 3 times to generate exclusive calibration curves for Pb and Bi; S5: Detection of the sample to be tested. Place the sample to be tested on the spark table to ensure airtightness. Set the excitation parameters: pre-burning time: 5 seconds, used to remove the surface interference layer; integration time: 10 seconds, used to ensure the acquisition of trace element signals; Start excitation and collect the intensities of characteristic spectral lines: Pb characteristic spectral line: 283.306 nm; Bi characteristic spectral line: 306.772 nm, then automatically call the interlock calibration curve to calculate the element content; S6: Result verification and precision control. Continuously detect the same sample 5 times, calculate the relative standard deviation. When continuously detecting the same sample to be measured 5 times, the relative standard deviations of Pb and Bi need to be ≤5%. If it exceeds the tolerance, re-execute the steps of S3. At the same time, randomly select 10% of the samples for retesting by ICP-MS. It is required that when the content ≥20 ppm, the result of the direct-reading spectrometer ≤8%, and when the content <20 ppm, the absolute value difference ≤2 ppm. Example 2: A method for interlock detection of lead and bismuth elements in aluminum alloy based on a direct-reading spectrometer, including the following operation steps: S1: Preparation of the sample to be measured. Prepare aluminum alloy 6061 after forging and machining of aluminum ingots. Use sandpaper with a mesh size of more than 120 to polish the surface of aluminum alloy 6061, thoroughly remove the oxide layer, ensure that the detection surface of aluminum alloy 6061 is flat and smooth, cover its size with the excitation area of the spark table, ultrasonically clean it with acetone and absolute ethanol for 3 minutes in sequence, and then dry it with nitrogen. The certified values of the elements of aluminum alloy 6061 are wt%: Si 0.69%, Fe 0.18%, Cu 0.25%, Mn 0.1%, Mg 0.98%, Cr 0.22%, Zn 0.013%, Ti 0.031%, Pb 0.0006%, Bi 0.0016%, and its surface roughness Ra ≤6.3 μm; S2: Standard sample selection and pretreatment. Prepare a standard sample combination, including EK6061 and pure aluminum 0607, and perform surface grinding and cleaning on them synchronously with the sample to be measured to ensure consistent excitation conditions. Select Southwest Aluminum for EK6061, and its certified values of elements are: Si 0.729±0.01 wt%, Fe 0.196±0.005 wt%, Cu 0.291±0.008 wt%, Pb 0.0043±0.0005 wt%; select Fushun Aluminum Factory for pure aluminum 0607, and its certified values of elements are: Pb 0.0076±0.0003 wt%, Bi 0.0033±0.0002 wt%. Each batch of standard samples needs to be verified by a spark direct-reading spectrometer before use, and the light intensity fluctuation of the main elements ≤5%. If it exceeds the tolerance, the standard sample is invalidated; S3: Initialization of the spectrometer system, including equipment configuration: a direct-reading spectrometer equipped with a CMOS detector; the excitation source is a high-voltage spark generator with an energy parameter of 8-10 J; the light chamber environment is a constant temperature of 25±0.5°C, and the argon purity ≥99.999%; Environmental control: the argon pressure is 0.55 MPa; the laboratory temperature and humidity are 23±1°C; the optical path stabilization time is preheating ≥2 hours; S4: Dual-standard sample joint control calibration, including primary standard sample calibration: In the instrument software, select the "Type Standardization" module, input the element certification values of the EK6061 standard sample, excite the standard sample 3 times continuously, take the average light intensity to establish the calibration curve for major elements. The following are the original data after excitation: Element Light intensity value (count) Calculated content (%) Pb 1.258 0.00074 Bi 892 0.00018 ; Trace standard sample calibration: Create a new "Additional Calibration" channel, select Pb and Bi elements, input the element certification values of pure aluminum 0607, excite 3 times, and generate the exclusive calibration curves for Pb and Bi. The following are the average values of the three measurements: ICP-MS comparison data: Pb 8.1 ppm, Bi 1.9 ppm; Relative deviation: Pb - 8.6%, Bi - 5.3%, meeting the requirement of ≤±15%; S5: Detection of samples to be tested. Place the sample to be tested on the spark table, ensure airtightness, and set the excitation parameters: Pre-ignition time: 5 seconds, used to remove the surface interference layer; Integration time: 10 seconds, used to ensure the collection of trace element signals; Start excitation, collect the intensity of characteristic spectral lines: Pb characteristic spectral line: 283.306 nm; Bi characteristic spectral line: 306.772 nm. Then automatically call the joint control calibration curve to calculate the element content; S6: Result verification and precision control. Continuously detect the same sample 5 times, calculate the relative standard deviation. For the same sample to be tested continuously detected 5 times, the relative standard deviation of Pb and Bi needs to be ≤5%. If it exceeds the tolerance, re-execute the steps of S3. At the same time, randomly select 10% of the samples for retesting by ICP-MS. It is required that when the content ≥20 ppm, the result of the direct-reading spectrometer ≤8%, and when the content <20 ppm, the absolute value difference ≤2 ppm. The following is the relative standard deviation table: Compared with ICP-MS (Inductively Coupled Plasma Mass Spectrometry), the deviation ≤±8%. Based on the above content, it can be seen that this method can improve the detection accuracy. The detection limit of Pb / Bi reaches 10 ppm, which is better than the 30 ppm lower limit of conventional spectrometers. The relative error ≤15%, meeting the industrial-grade quality control requirements. Using a CMOS spectrometer to replace the CPM equipment can effectively reduce the overall detection cost, and at the same time, the detection cost of a single sample can also be effectively reduced; The joint control calibration process is shortened to 20 minutes, which can support on-line detection on the production line. 15 samples can be analyzed per hour. This method can also be adapted to the operating systems of mainstream spectrometers such as ARL and OBLF. By adjusting the standard sample combination, it can be extended to other aluminum alloys, such as 7075, 5052 and elements Sb, Sn, etc.; Break through the detection blind area of traditional direct-reading spectrometers for low-content lead and bismuth elements, successfully quantify trace components at the 10 ppm level, eliminate spectral interference caused by matrix effects through a dual-standard sample control mechanism, greatly reduce systematic errors, establish a calibration system resistant to environmental fluctuations, ensure the consistency of detection results for different batches and different operators. At the same time, relax the restrictions on the surface roughness of samples, reduce polishing time and equipment wear, and achieve a multiple-fold increase in detection efficiency through parallelized calibration and detection steps. The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for jointly controlling and detecting lead and bismuth elements in aluminum alloy based on a direct-reading spectrometer standard sample, characterized in that: It includes the following operation steps: S1: Preparation of the sample to be tested. Prepare the aluminum alloy 6061 after forging and machining of the aluminum ingot. Polish the surface of the aluminum alloy 6061 with sandpaper of more than 120 meshes to thoroughly remove the oxide layer, ensure that the detection surface of the aluminum alloy 6061 is flat and smooth, cover its size to the excitation area of the spark table, ultrasonically clean it with acetone and absolute ethanol in sequence for 3 minutes, and then dry it with nitrogen; S2: Selection and pretreatment of the standard sample. Prepare the standard sample combination, including EK6061 and pure aluminum 0607, and perform surface grinding and cleaning on them synchronously with the sample to be tested to ensure consistent excitation conditions; S3: Initialization of the spectrometer system, including equipment configuration: a direct-reading spectrometer equipped with a CMOS detector; the excitation source is a high-voltage spark generator with an energy parameter of 8 - 10J; the optical chamber environment is a constant temperature of 25 ± 0.5°C, and the purity of argon gas is ≥ 99.999%; Environmental control: the argon gas pressure is 0.55MPa; the temperature and humidity in the laboratory are 23 ± 1°C; the optical path stabilization time is ≥ 2 hours for preheating; S4: Dual-standard sample joint control calibration, including main standard sample calibration: select the "type standardization" module in the instrument software, input the element certification values of the EK6061 standard sample, continuously excite the standard sample 3 times, and take the average light intensity to establish the calibration curve of the main elements; Trace standard sample calibration: create a new "additional calibration" channel, select the elements of Pb and Bi, input the element certification values of pure aluminum 0607, and excite 3 times to generate the exclusive calibration curves of Pb and Bi; S5: Detection of the sample to be tested. Place the sample to be tested on the spark table to ensure airtightness, and set the excitation parameters: pre-ignition time: 5 seconds, used to remove the surface interference layer; integration time: 10 seconds, used to ensure the acquisition of trace element signals; Start excitation, collect the intensities of characteristic spectral lines: Pb characteristic spectral line: 283.306nm; Bi characteristic spectral line: 306.772nm, and then automatically call the joint control calibration curve to calculate the element content; S6: Result verification and precision control. Continuously detect the same sample 5 times and calculate the relative standard deviation.

2. The method for jointly controlling and detecting lead and bismuth elements in aluminum alloy based on a direct-reading spectrometer standard sample according to claim 1, characterized in that: The element certification values of the aluminum alloy 6061 in S1 are wt%: Si 0.69%, Fe 0.18%, Cu 0.25%, Mn 0.1%, Mg 0.98%, Cr 0.22%, Zn 0.013%, Ti 0.031%, Pb 0.0006%, Bi 0.0016%, and its surface roughness Ra ≤ 6.3μm.

3. The method for detecting lead and bismuth elements in aluminum alloy based on the standard sample joint control of a direct-reading spectrometer according to claim 1, wherein: In S2, for EK6061, Southwest Aluminum is selected, and its element certification values are: Si 0.729 ± 0.01wt%, Fe 0.196 ± 0.005wt%, Cu 0.291 ± 0.008wt%, Pb 0.0043 ± 0.0005wt%; for pure aluminum 0607, Fushun Aluminum Factory is selected, and its element certification values are: Pb 0.0076 ± 0.0003wt%, Bi 0.0033 ± 0.0002wt%.

4. The method for detecting lead and bismuth elements in aluminum alloy based on the control of standard samples by direct-reading spectrometer according to claim 1, characterized in that: In S2, each batch of standard samples needs to be verified by a spark direct-reading spectrometer before use, and the light intensity fluctuation of its main elements ≤ 5%. If it exceeds the tolerance, the standard sample will be invalidated.

5. The method for detecting lead and bismuth elements in aluminum alloy based on the control of reference samples of direct-reading spectrometers according to claim 1, characterized in that: In S6, the same sample to be tested is continuously detected 5 times. The relative standard deviation of Pb and Bi needs to be ≤5%. If it exceeds the tolerance, the steps of S3 are re-executed. At the same time, 10% of the samples are randomly selected for retesting by ICP-MS. It is required that when the content ≥20 ppm, the result of the direct-reading spectrometer ≤8%, and when the content <20 ppm, the absolute value difference ≤2 ppm.

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