Method for rapidly detecting chemical components in thin steel plate below 2mm by using direct-reading spectrometer

Abstract

The invention discloses a method for rapidly detecting chemical components in a thin steel plate below 2mm by using a direct-reading spectrometer, belongs to the technical field of physical and chemical detection, and aims to solve the problem that a sample with the thickness of less than 2mm in the national standard GB / T 4336-2016 cannot be directly analyzed by using spark discharge atomic emission spectrometry. The method comprises the following operation steps: confirming conditions such as a sample preparation mode, a sample spectrum excitation limit thickness, influence of sample flatness and use of a special sample clamp, optimizing working conditions of an instrument, and establishing a method for measuring 13 elements such as C, Si, Mn, P, S, Cr, Ni, Cu, Al, Nb, V, Ti and N in a carbon steel and low alloy steel sheet with the thickness not less than 0.20 mm through spark discharge atomic emission spectrometry. And verifying the precision and accuracy of the determination result of each element, and comparing the results to show that the determination result of each element is consistent with the standard GB / T 4336-2016. The method does not need to decompose a sample, and has the characteristics of accurate and rapid determination and good stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal physical and chemical detection, and particularly relates to a method for rapidly detecting chemical components in thin steel plates with a thickness of less than 2 mm by using a direct-reading spectrometer. Background Art

[0002] In recent years, in the fields of home appliance manufacturing, precision electronic and electrical industries, automotive industry, machinery manufacturing, etc., the use of thin steel plates and steel strips has been increasing. Whether the chemical components meet the standards directly affects the product quality of thin steel plates and steel strips (hardness, metallographic structure and mechanical properties). The direct-reading spectrometer has the advantages of fast analysis speed and high accuracy, and is used to analyze the accurate content of various elements in metal products. However, at present, in the method GB / T 4336—2016 for determining carbon steel and medium and low alloy steel, it is required that the sample thickness is greater than 2 mm, while in the actual detection process, samples with a thickness less than 2 mm will be encountered. For the detection of chemical components of thin steel plates and steel strips, the biggest feature and difficulty is that the sample is too thin. When grinding, the temperature of the sample rises, the sample is easily deformed, and it is easily punctured during spectral excitation, seriously affecting the experimental results. Therefore, it has practical significance to rapidly and accurately determine the chemical components in thin plates of carbon steel and medium and low alloy steel by using a spark source atomic emission spectrometer. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a method for rapidly detecting chemical components in thin steel plates with a thickness of less than 2 mm by using a direct-reading spectrometer. This method mainly optimizes the sample preparation process, determines the sample preparation methods and spectral excitation limit thicknesses for samples of different thicknesses, the influence of sample flatness and the use of special sample fixtures, optimizes measurement parameters, etc., and establishes an analytical method for elements such as C, Si, Mn, P, S, Cr, Ni, Cu, Al, Nb, V, Ti, etc. in thin plates with a thickness less than 2 mm by using the spark source atomic emission spectrometry, so as to achieve a rapid, economical and accurate measurement method for testing carbon steel and low alloy steel thin plates.

[0004] The technical problem to be solved by the present invention is: by optimizing the sample preparation method, selecting appropriate fixtures, etc., and confirming the thickness limit of thin plate samples for direct-reading spectral inspection through experiments, determining the optimal test conditions, and carrying out the accuracy and precision verification work of the detection method, the inspection of thin plate (0.20 mm - 2.00 mm) samples is solved. To solve the above technical problem, the steps of the present invention are as follows: Step 1: Conduct on-site preparation for the direct-reading spectrometer; Step 2: Optimize the sample preparation method according to requirements; Step 3: Process the test specimen to make it a sample that meets the detection requirements of the direct-reading spectrometer; Step 4: Determine the spectral excitation limit thickness of the sample Step 5. Use of the special fixture for thin plate samples and the combination of the pressing block Step 6. Optimize the instrument flushing, pre-ignition, and exposure times; Step 7. Ensure the purity of argon gas and determine the argon gas flow rate; Step 8. Select a suitable quality control calibration sample; Step 9. Conduct the precision and accuracy tests of the method.

[0005] Furthermore, in the said Step 1, the process of on-site preparation is as follows: 1) Power on and ventilate the spectrometer to stabilize it, maintain the direct-reading spectrometer, and calibrate the curve; 2) Furthermore, in the said Steps 2 and 3, the optimized sample preparation method is as follows: After surface treatment by heating and soaking with HCL solution or NaOH solution, quickly polish it with a belt sander and set it aside for use.

[0006] Furthermore, in the said Step 4, determine that the spectral excitation limit thickness of the thin steel plate sample is 0.20 mm. Samples with a thickness less than 0.20 mm are not suitable for analysis by the direct-reading spectrometry method.

[0007] Furthermore, in the said Step 5, after using the special fixture and the combination of the pressing block, almost no depression and blue color change can be seen on the back of the sample.

[0008] Furthermore, in the said Step 6, optimize the instrument flushing, pre-ignition, and exposure times; appropriately increase the pre-ignition and integration times, and the analysis results are more stable; for thin plate samples, if the pre-ignition time is extended, the sample may be punctured, affecting the accuracy of the test results. The experimental selection of the flushing time is 8 s, the pre-ignition time is 4 s, and the exposure time is 12 s.

[0009] Furthermore, in the said Step 7, the process of ensuring the purity of argon gas and determining the argon gas flow rate is as follows: Ensure that the purity of argon gas meets the standard through two-stage purification by an argon gas purifier (CZA-4N / MP2000). The argon gas pressure meets the requirements when it is between 0.50 Mpa and 0.55 Mpa.

[0010] Furthermore, in the said Step 8, the self-made thin plate control sample method can eliminate the influence of systematic deviation. Select thin plate samples of the same brand, with similar thickness, composition, and the same metallurgical structure for production samples. Determine the value by chemical methods and use them as control samples to calibrate the production samples. At the same time, it can reduce the frequency of instrument curve standardization, reduce the consumption of standard samples, and improve the inspection efficiency.

[0011] Furthermore, in the said Step 9, conduct the precision and accuracy tests of the method to verify the feasibility of the inspection method.

[0012] The special fixture includes a support base, a horizontal balance beam and a compression screw; there are two support bases, which are located on the left and right sides respectively; the support base includes a base and a support column, three threaded holes are opened on the base, a vertical support column is connected in the central threaded hole, and screws are installed in the other two threaded holes to fix the support base to the spectrometer spark table plate; the horizontal cross beam is connected between the two support columns, and the horizontal cross beam is detachably connected to the two support columns respectively; a through threaded hole is opened in the center of the horizontal cross beam, a vertical compression screw is connected in the threaded hole, and a knob is provided at the top of the compression screw; a cylindrical heat-conducting copper block for flattening the thin plate is placed below the center of the horizontal cross beam, and the cylindrical heat-conducting copper block is compressed by rotating the compression screw.

[0013] The beneficial effects of the present invention are as follows: This application determines the sample preparation method for thin steel plate samples of different thicknesses; systematically studies the parameter conditions, operation steps and inspection precautions during the determination of multi-element contents in thin steel plates. Determines the thickness limit of thin steel plates inspected by direct-reading spectroscopy, solves the problem that samples with a thickness less than 2 mm in GB / T 4336-2016 cannot be directly analyzed by direct-reading spectroscopy, and expands the inspection sample thickness of thin plate samples directly inspected by the direct-reading spectroscopy method in GB / T 4336. Effectively improves the accuracy and reliability of the results of rapid quantitative analysis of thin plate samples by spark direct-reading spectroscopy. In order to make the above and other objects, features and advantages of the present invention more obvious and understandable, the following preferred embodiments are specifically described in detail as follows. Description of the Drawings

[0014] Figure 1 It is a schematic structural diagram of the fixture of the present invention; Figure 2 It is a front view of the fixture of the present invention; Figure 3 It is a top view of the fixture of the present invention; In the figure: 1 - support base, 101 - support column, 102 - base, 3 - horizontal cross beam, 4 - compression screw, 5 - retaining pin, 6 - spark table plate. Specific Embodiments

[0015] The present invention will be described in detail below in conjunction with the embodiments: Such as Figures 1-3As shown in the figure, it includes a support base 1, a horizontal crossbeam 3, and a pressing screw 4. There are two support bases 1, which are located on the left and right sides respectively; the support base 1 includes a base 102 and a support column 101. Three threaded holes are provided on the base 102, and the threaded holes are arranged at equal intervals on the same plane. A vertical support column 101 is connected in the central threaded hole, and screws are installed in the other two threaded holes to fix the support base 1 to the table board of the spectrometer spark table. The horizontal crossbeam 3 is connected between the two support columns 101. The left U-shaped hole of the horizontal crossbeam 3 is connected to the left support column 101, and the right reverse U-shaped hole of the horizontal crossbeam 3 is connected to the right support column 101. A through threaded hole is provided in the center of the horizontal crossbeam 3, and a vertical pressing screw 4 is connected in the threaded hole. A knob is provided at the top of the pressing screw 4. By rotating the pressing screw 4 to press the cylindrical heat-conducting copper block to fix the position of the thin-plate metal sample, the thin-plate metal sample can be firmly and reliably clamped in the excitation hole of the spark table, so as to adjust the position of the thin-plate metal sample on the excitation table of the direct-reading spectrometer.

[0016] Step 1: Conduct on-site preparation for the direct-reading spectrometer Power on and ventilate the spectrometer to stabilize it, perform maintenance on the direct-reading spectrometer, and calibrate the curve.

[0017] Step 2: Optimize the sample preparation method according to requirements The optimized sample preparation method is as follows: First, cut the sample into a rectangle of 30 - 40 mm × 100 mm; if there is oil stain or coating on the surface of the thin-plate sample, using a grinding wheel to polish cannot completely remove the oil stain and coating on the sample surface. In this case, the sample can be heated and soaked in HCl or NaOH solution for surface treatment before determining the chemical composition.

[0018] Step 3: Process the test sample to make it meet the requirements of the direct-reading spectrometer for testing samples The following 3 preparation methods are respectively adopted: (1) For samples with too thin or uneven surfaces, do not polish them, directly wipe them with anhydrous ethanol, and dry them for later use; (2) For samples with too thin or uneven surfaces that are not suitable for grinding with a sanding machine, polish them by hand with sandpaper, wipe them with anhydrous ethanol, and dry them for later use; (3) Grind them with a sanding machine and set aside. Samples with a thickness less than 0.30 mm are polished by hand with sandpaper, and samples with a thickness of 0.3 - 2.00 mm are polished with a sanding machine.

[0019] Step 4: Determine the spectral excitation limit thickness of the sample Under the optimized selected working conditions, thin plate samples of carbon steel and low alloy steel with different thicknesses were excited. It was found that the back of the sample was slightly sunken and the color turned blue. When samples with a thickness less than 0.20 mm were excited, the samples became thinner, melted and adhered, and were easily punctured during excitation. Through experiments, it was confirmed that the spectral excitation limit thickness of thin plate samples of carbon steel and medium and low alloy steel was 0.20 mm, and samples with a thickness less than 0.20 mm were not suitable for analysis by spark discharge atomic emission spectrometry.

[0020] Step Five: Use of the special fixture and pressing block combination for thin plate samples The flatness of the surface of the thin plate sample directly affects the excitation effect. When an uneven sample is excited, the sample does not fit tightly with the spark table and light leakage is likely to occur, directly affecting the precision and correctness of the results. Therefore, when inspecting thin plate samples, especially samples with an uneven surface, a special fixture and pressing block combination need to be used to press the sample to ensure that the sample fits tightly with the excitation table board. The more uneven the surface of the sample, the more obvious the depression on the back of the excitation point of the sample and the change in color to blue. However, for the sample after using the special fixture and pressing block combination, almost no depression and color change to blue can be seen on the back.

[0021] Step Six: Optimize the instrument flushing, pre-burning and exposure times The main working conditions of the instrument were investigated by the orthogonal test method. The results showed that under the original working curve conditions, appropriately increasing the pre-burning and integration times made the measurement results more stable. For thin plate samples, extending the pre-burning time might puncture the samples and affect the accuracy of the test results. Considering comprehensively, the flushing time was selected as 8 s, the pre-burning time as 4 s, and the exposure time as 12 s.

[0022] Step Seven: Ensure the purity of argon and determine the argon flow rate When analyzing ultra-low carbon, phosphorus, sulfur and nitrogen elements, their analysis wavelengths are C (133.6 nm), P (178.3 nm), S (180.7 nm), N (149.3 nm) respectively. The wavelengths belong to the ultraviolet region. To avoid the influence of air, the excitation discharge process should be carried out in an argon atmosphere. If the purity of argon does not meet the requirements, the test precision will be affected; the purity of argon for spectral analysis must reach more than 99.999%. If the purity does not meet the standard, an argon purifier must be connected in the gas path and purified through two stages of the argon purifier (CZA-4N / MP2000) to ensure that the purity of argon meets the standard.

[0023] Step Eight: Select appropriate quality control calibration samples Since there are no dedicated standard samples for carbon steel and low alloy steel thin plates in the market, conventional bulk standard substances are used for daily quality control. However, there are systematic deviations in the metallurgical structures between the bulk standard substances and the thin plate specimens. To eliminate the influence of systematic deviations, the experiment adopted the method of using self-made carbon steel and low alloy steel thin plate control samples. Thin plate specimens of the same grade were selected, with similar thickness, composition, and the same metallurgical structure for production samples. The values were determined using national standard methods (C and S were determined according to GB / T 20123—2006 "Determination of total carbon and sulfur contents in steel - Infrared absorption method after combustion in high-frequency induction furnace (conventional method)"; N was determined according to GB / T 20124—2006 "Determination of nitrogen content in steel - Inert gas fusion thermal conductivity method (conventional method)"; the results of the remaining elements were determined according to GB / T 20125—2006 "Determination of multi-element contents in low alloy steels - Inductively coupled plasma atomic emission spectrometry"). These were used to correct the determination results of the specimens as control samples. At the same time, it can reduce the frequency of standardizing the instrument working curve, reduce the consumption of conventional bulk standard samples, and improve the inspection efficiency.

[0024] Step Nine: Conduct precision and accuracy tests on the method 1. Precision test According to the above experimental conditions, different thickness samples were detected 10 times, and the results are shown in Table 1.

[0025] As can be seen from the above table, the accuracy and precision of this method are good.

[0026] 2. Trueness comparison test Under the experimental conditions of this method, different thickness thin plate samples were analyzed, and the determination results are shown in Table 2 Comparison of spectral and chemical analysis results of carbon steel thin plates with different thicknesses Under the experimental conditions of this method, for different thickness thin plate samples, the average determination values obtained from parallel determinations 3 times were compared with the determination values of infrared carbon-sulfur analysis method, inert gas fusion thermal conductivity method, and ICP-AES method to observe their stability and accuracy. The determination results are shown in Table 2. The detection results of the thin plates are consistent with the determination results of other analysis methods, the measurement accuracy is reliable, the results are consistent, and the results of the comparative experiment are relatively satisfactory.

Claims

1. A method for quickly testing the chemical composition of thin steel plates less than 2 mm using a direct reading spectrometer, characterized in that: Use different steel thin plates with thickness ranging from 0.20mm to 2.0mm as the samples to be tested; use a sanding machine to grind the sample surface to make it flat, smooth and free of oxide layer; select the working curve for standardization correction, and select a control sample similar to the test sample for quality control. After meeting the requirements, use a special fixture to press and fix the sample so that the sample fits tightly with the excitation platen, and perform quantitative measurement and analysis on the sample; The special fixture includes a support seat, a horizontal beam and a pressing screw; The support base includes two, and the two support bases are separated on the left and right sides; the support base includes a base and a support column, and three threaded holes are opened on the base, the central threaded hole is connected to the vertical support column, and screws are installed in the other two threaded holes to fix the support base to the spark table of the spectrometer; The horizontal beam is connected between the two support columns, and the horizontal beam and the two support columns are detachably connected; a through screw hole is opened in the center of the horizontal beam, a vertical clamping screw is connected in the screw hole, and a knob is provided on the top of the clamping screw; a cylindrical thermal conductive copper block for flattening the thin plate is placed below the center of the horizontal beam, and the cylindrical thermal conductive copper block is clamped by rotating the clamping screw.

2. The method for rapidly testing the chemical composition of thin steel plates with a thickness less than 2 mm using a direct reading spectrometer according to claim 1, characterized in that: The detailed sample processing method is as follows: 1) Select the sample preparation method: After surface treatment by heating and soaking in HCL solution or NaOH solution, use a belt sander to quickly polish and set aside; 2) The maximum thickness of the sample spectrum excitation is determined to be no less than 0.20 mm.

3. The method for rapidly testing the chemical composition of a thin steel plate with a thickness less than 2 mm using a direct reading spectrometer according to claim 1, characterized in that: The experiment selected a flushing time of 8s, a pre-burning time of 4s, and an exposure time of 12s.

4. According to the method of claim 1 for rapidly testing the chemical composition of thin steel plates less than 2 mm in thickness using a direct reading spectrometer, the purity of argon is improved by an argon purifier, and the argon pressure is controlled at 0.50 MPa to 0.55 MPa.

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