A rapid detection method for the tellurium content of free-cutting stainless steel containing tellurium

Abstract

A rapid detection method for the tellurium content of free-cutting stainless steel containing tellurium, comprising: 1) preparing at least 5 standard samples with tellurium contents of 0.0001-0.19 wt%; 2) selecting the working spectral line wavelength of tellurium to be 214.22-215.22 nm and setting the working pre-ignition time to 21-45 seconds; 3) performing light intensity analysis on the standard samples to establish a tellurium percentage content-light intensity standard analysis curve, i.e., a C-I standard analysis curve; 4) preparing one control sample within each of two tellurium content ranges; 5) detecting the tellurium contents C1 and C2 of the two control samples; 6) detecting the light intensity values I1 and I2 of the tellurium element in the control samples, and calculating the percentage contents of the tellurium element in the control samples as C1' and C2' respectively through the C-I standard analysis curve; 7) correcting the C-I standard analysis curve to a C'-I standard analysis curve; 8) detecting the light intensity value I of the test sample S , and calculating the percentage content C of the tellurium element in the test sample by using the corrected C'-I standard analysis curve S .

Description

Technical Field

[0001] The present invention relates to the technical field of analytical chemistry detection, and particularly relates to a method for detecting the tellurium content of tellurium-containing free-cutting stainless steel. Background Art

[0002] Tellurium-containing free-cutting stainless steel is a new type of environmentally friendly free-cutting stainless steel. For example, Chinese Patent Publication No. CN111286580A discloses a low-carbon tellurium-containing high-sulfur free-cutting steel slab and its production method; Chinese Patent Publication No. CN101597725A discloses free-cutting chromium stainless steel for ballpoint pen tips; Chinese Patent Publication No. CN107058906A discloses stainless steel wire for ballpoint pen tips and its preparation method.

[0003] It can be seen from the above three patents that the chemical composition weight percentages of tellurium-containing free-cutting stainless steel are generally: C ≤ 0.030%, Si ≤ 1.00%, Mn ≤ 2.00%, P 0.01 - 0.070%, S 0.15 - 0.50%, Cr 19 - 21%, Te 0.01 - 0.07%; among them, tellurium, as an environmentally friendly free-cutting element, is listed as an important control index for industrial smelting production.

[0004] During the refining stage of the smelting production of tellurium-containing free-cutting stainless steel, pure tellurium needs to be added. Due to the low melting point (452°C) and low boiling point (1390°C) of pure tellurium, evaporation occurs after it is added to the molten steel, resulting in unstable content dissolved in the molten steel. Therefore, in order to ensure that the tellurium content of free-cutting stainless steel is within the control range of the production process, it is necessary to quickly and accurately detect the tellurium content in the molten steel during the smelting process.

[0005] The current status of the detection technology for tellurium content in existing steel is shown in Table 1:

[0006] Table 1

[0007]

[0008]

[0009] As can be seen from Table 1, the existing inductively coupled plasma emission spectrometry, oscillopolarography, and atomic fluorescence spectrometry cannot meet the requirements of rapid smelting detection in terms of timeliness because the samples need to be acid-dissolved before analysis. X-ray fluorescence spectrometry and atomic emission photoelectric direct-reading spectrometry only require surface grinding before analysis and can meet the requirements of rapid smelting detection in terms of timeliness. However, due to the lack of standard samples of tellurium-containing free-cutting stainless steel in the domestic and international markets, the two methods are still in the qualitative and semi-quantitative stages in terms of accuracy. As a rapid detection method for metallurgical furnace front, X-ray fluorescence spectrometry must be equipped with an infrared carbon-sulfur analyzer because it cannot detect carbon elements. In comparison, photoelectric direct-reading spectrometry for metallurgical furnace front analysis can not only meet the requirements of rapid analysis but also meet the detection requirements in terms of element diversity.

[0010] Therefore, the research and development of a quantitative analysis method for detecting tellurium-containing free-cutting stainless steel by atomic emission photoelectric direct-reading spectrometer has practical significance for meeting the rapid detection requirements of smelting production.

[0011] In the existing technology, there is no rapid quantitative detection method for the tellurium content of tellurium-containing free-cutting stainless steel developed by atomic emission photoelectric direct-reading spectrometer. The main technical difficulties are as follows: 1. There is no working spectral line developed specifically for detecting the tellurium content of tellurium-containing free-cutting stainless steel at home and abroad; 2. As free-cutting elements sulfur and tellurium, they increase the difficulty of exciting samples by the photoelectric direct-reading spectrometer; 3. The high content of non-metallic elements in free-cutting stainless steel leads to obvious matrix effects during the detection process. Summary of the Invention

[0012] The purpose of the present invention is to provide a detection method for the tellurium content of tellurium-containing free-cutting stainless steel, which can accurately and rapidly detect the tellurium content in tellurium-containing free-cutting stainless steel, and has practical significance for meeting the requirements of accurate input of tellurium raw materials and reducing refining time in industrial smelting production and the development of tellurium-containing free-cutting stainless steel products.

[0013] To achieve the above purpose, the technical solution of the present invention is as follows:

[0014] The rapid detection method for the tellurium content of the tellurium-containing free-cutting stainless steel described in the present invention includes the following steps:

[0015] 1) Prepare at least 5 free-cutting stainless steel standard samples with tellurium content in the range of 0.0001 - 0.19 wt%;

[0016] 2) Select the working spectral line wavelength of tellurium on the atomic emission photoelectric direct-reading spectrometer to be 214.22 - 215.22 nm, and set the working pre-ignition time of the atomic emission photoelectric direct-reading spectrometer to be 21 - 45 seconds;

[0017] 3) Use the atomic emission photoelectric direct-reading spectrometer to analyze the light intensity of the standard samples, and establish a tellurium percentage content - light intensity standard analysis curve, that is, a C-I standard analysis curve;

[0018] 4) Prepare one control sample respectively in two ranges of tellurium content of 0.025 - 0.035 wt% and 0.045 - 0.055 wt%;

[0019] 5) Use inductively coupled plasma emission spectrometry to detect the tellurium content of the two control samples, and the tellurium contents are C1 and C2 respectively;

[0020] 6) Detect the light intensity values I1 and I2 of tellurium element in the two control samples by using an atomic emission photoelectric direct-reading spectrometer, and calculate the percentage contents C1’ and C2’ of tellurium element in the two control samples respectively through the C-I standard analysis curve based on the obtained light intensity values I1 and I2 of tellurium element in the two control samples;

[0021] 7) Correct the C-I standard analysis curve to a C’-I standard analysis curve, where C’ = C + 1 / 2 * (C1 - C1’ + C2 - C2’);

[0022] 8) Detect the light intensity value I of the test sample by using an atomic emission photoelectric direct-reading spectrometer S , and calculate the percentage content C of tellurium element in the test sample through the corrected C’-I standard analysis curve based on the obtained light intensity value I of the test sample S . S .

[0023] Preferably, the tellurium content range of the standard sample is 0.0005 - 0.19 wt%.

[0024] Preferably, the working conditions of the atomic emission photoelectric direct-reading spectrometer are as follows: argon gas flow rate ≥ 800 L / h, argon gas purity ≥ 99.999%, vacuum degree ≤ 2.0 Pa, tungsten electrode φ4 - 7 mm, 30 - 120° cone angle, analysis gap 3 - 6 mm, purge time 2 - 5 s, pre-burning time 21 - 45 s, integration time 10 - 20 s.

[0025] Preferably, in step 3), the mathematical equation for establishing the C-I standard analysis curve is: C = 3.51558 * 10 -9 *I 2 + 1.09122 * 10 -5 *I - 4.847 * 10 -2 , where C is the percentage content of tellurium element in the standard sample and I is the light intensity value of the standard sample.

[0026] Preferably, in step 7), the mathematical equation for establishing the corrected C’-I standard analysis curve is:

[0027] C’ = 3.51558 * 10 -9 *(I 2 - 0.5 * I1 2 - 0.5 * I2 2 ) + 1.09122 * 10 -5 *(I - 0.5 * I1 - 0.5 * I2) + 0.5 * (C1 + C2)

[0028] Wherein, C' is the percentage of tellurium in the standard sample after calibration, I is the light intensity value of the standard sample, I1 is the light intensity value detected by control sample 1, I2 is the light intensity value detected by control sample 2, C1 is the percentage of tellurium in control sample 1, and C2 is the percentage of tellurium in control sample 2.

[0029] Preferably, in step 2), the detector of tellurium in the atomic emission photoelectric direct reading spectrometer adopts a photomultiplier tube + filter.

[0030] Preferably, in step 2), the atomic emission photoelectric direct reading spectrometer selects the working spectral line wavelength of tellurium as λ=214.28 nm.

[0031] The tellurium content of the standard sample of tellurium-containing free-cutting stainless steel prepared by the present invention is in the range of 0.0001-0.19%, covering the tellurium content range of the existing tellurium-containing free-cutting stainless steel.

[0032] The present invention uses an atomic emission photoelectric direct reading spectrometer as a detection instrument. Compared with the use of an inductively coupled plasma emission spectrometer and a polarographic instrument, the use of an atomic emission photoelectric direct reading spectrometer can directly detect samples with a polished surface, without the need for complex mechanical processing and pre-analysis pretreatment such as sample cuttings, strong acid heating and dissolution, and microwave digestion, thereby shortening the detection time. Compared with the combination of X-ray fluorescence spectrometry and carbon-sulfur analyzer, the operation is simple and the instrument and equipment cost is low.

[0033] Preferably, the atomic emission photoelectric direct reading spectrometer uses a photomultiplier tube as a detection element, and selects the tellurium element wavelength of 214.28nm as the working spectrum line. The working spectrum line is obtained by tracing and comparing the half-peak width and peak value of the three characteristic wavelengths of the tellurium element 214.28nm, 225.90nm, and 238.58nm, and obtaining 214.28nm as the preferred working spectrum line.

[0034] The samples with fixed values were introduced into the standard sample library of QSG750-Ⅱ atomic emission photoelectric direct reading spectrometer, and the purge time of 3 seconds, pre-combustion time of 32 seconds, and integration time of 17 seconds were selected as instrument excitation conditions to establish a standard analysis curve. Compared with the pre-combustion time of 9 seconds for ordinary steel grades, the pre-combustion excitation conditions selected in the present invention are based on the chemical composition of free-cutting stainless steel and are more preferred.

[0035] The control sample was prepared based on the chemical composition requirements of the process for smelting tellurium-containing free-cutting stainless steel before furnace smelting. The tellurium content of the sample was determined using the ICP test results and imported into the material library of the atomic emission photoelectric direct reading spectrometer. The control sample was used to calibrate the standard analysis curve to establish the analysis method. Compared with directly analyzing the sample using the standard analysis curve, the analysis method established using the control sample can effectively eliminate the interference caused by the matrix effect and can quickly correct the error caused by the drift of the curve.

[0036] Preferably, a photomultiplier tube and a filter are used as the detection elements for tellurium in the present invention.

[0037] The basis for selecting the working spectral lines of the atomic emission photoelectric direct-reading spectrometer in the method of the present invention is to select the characteristic spectral lines with the highest peak intensity and the narrowest half-peak width of the tracing curve as the working spectral lines.

[0038] The preferred range of the "pre-ignition time" of the atomic emission photoelectric direct-reading spectrometer described in the present invention is 21 to 45 seconds.

[0039] In the national standard GBT11170-2008 Determination of multi-element contents in stainless steels - Spark discharge atomic emission spectrometric method, the pre-ignition time is specified to be 2 to 20 seconds. The stipulation of this pre-ignition time is mainly to avoid the following several influences:

[0040] 1. As the pre-ignition time increases, the analysis gap (the distance between the sample analysis surface and the tungsten electrode) increases unevenly, and this uneven increase leads to unstable excitation;

[0041] 2. As the pre-ignition time increases, the intensity value of the excited light decreases, and the decrease in the light intensity affects the accuracy and stability of the detection results;

[0042] 3. If the pre-ignition time is too short, the atomized vapor of the sample is insufficient, that is, the excitation is incomplete, resulting in a low detection result.

[0043] Currently in China, for metal materials that are difficult to excite, a longer pre-ignition time is adopted. It should be noted that the extension of this pre-ignition time is adjusted within the scope specified by the detection standards of their respective materials. The adjustment of this pre-ignition time mainly includes the following two methods:

[0044] The first is to change the pre-ignition time; excite the same high-standard sample once at each pre-ignition time; record the excited intensity value; through the trend graph of the intensity value and the pre-ignition time, select the time period with the least decrease in the light intensity value as the working pre-ignition time.

[0045] The second is to change the pre-ignition time; excite the same high-standard sample multiple times at each pre-ignition time; calculate the relative standard deviation (RSD) of the intensity values of multiple excitations; through the trend graph of the RSD of the intensity value and the pre-ignition time, select the time period with a small RSD value as the working pre-ignition time.

[0046] The adjustment method of the "pre-ignition time" of the atomic emission photoelectric direct-reading spectrometer described in the present invention, compared with the existing domestic adjustment methods currently, the same point is that both methods evaluate the relationship between the stability of the intensity value and the pre-ignition time, that is, evaluate the influence of extending the pre-ignition time on the stability of the instrument. In comparison, the advantages of the present invention are:

[0047] 1. The time range of evaluation is extended from "2 - 20 seconds" to "3 - 45 seconds".

[0048] 2. The intensity ratios (I H / I L ) of high and low standard samples at different pre - combustion times are evaluated. The larger the (I H / I L ), the higher the sensitivity and the higher the detection accuracy. That is, this index shows that extending the pre - combustion time will also affect the sensitivity of the instrument.

[0049] The purpose of adjusting the "pre - combustion time" of the atomic emission photoelectric direct - reading spectrometer of the present invention is as follows:

[0050] 1. Prolonging the pre - combustion time not only affects the stability of the instrument but also affects the sensitivity of the instrument.

[0051] 2. For the photoelectric direct - reading spectrometer for detecting tellurium in free - cutting stainless steel containing tellurium, selecting the pre - combustion time in the range of 21 - 45 seconds is beneficial to improving the stability and accuracy of the detection process.

[0052] The mathematical equation for the present invention to use two control samples to correct the standard analysis curve is C’ = 3.51558*10 -9 *(I 2 - 0.5*I1 2 - 0.5*I2 2 ) + 1.09122*10 -5 *(I - 0.5*I1 - 0.5*I2)+0.5*(C1 + C2), where C’ is the percentage content of tellurium after the standard sample is corrected, I is the light intensity value of the standard sample, I1 is the light intensity value detected by control sample 1, I2 is the light intensity value detected by control sample 2, C1 is the percentage content of tellurium in control sample 1, and C2 is the percentage content of tellurium in control sample 2.

[0053] Two calibration methods currently used in photoelectric direct - reading spectroscopy detection:

[0054] 1. Directly use the standard analysis curve to detect the test sample. This method first verifies the drift of the standard analysis curve by detecting the deviation between the results of the control sample or standard sample and the standard value. When the drift deviation is less than the limit value, the test sample is detected. When the drift deviation reaches the limit value, the instrument is completely calibrated with a standardized standard sample and then the test sample is detected.

[0055] 2. Use a single control sample to correct the standard analysis curve and then detect the test sample. This method first uses a single control sample to correct the standard analysis curve with a mathematical equation. If the drift deviation to be corrected is less than the limit value, correction is carried out and then the test sample is detected. If the drift deviation to be corrected reaches the limit value, the test sample is detected after complete standardization.

[0056] Compared with the existing two calibration methods, a single control sample can calibrate the matrix effect of the sample to a certain extent, which is more preferable.

[0057] The calibration method adopted in the present invention is to use two control samples to calibrate the standard analysis curve through the mathematical equation C’ = C + 1 / 2*(C1 - C1’ + C2 - C2’). For the calibration of a single control sample, the element content is selected at the median of the smelting production process composition range. Compared with the single control sample calibration, the element contents of the two control samples adopted in the present invention are respectively prepared with a control sample in two ranges of tellurium content of 0.025 - 0.035 wt% and 0.045 - 0.055 wt%, so that the calibration range covers the entire composition range of the smelting production process. In comparison, the advantages of the present invention are as follows: the calibration of the standard analysis curve is changed from single-point calibration to interval calibration, which improves the detection range of the calibrated curve. Secondly, the ability to correct the matrix effect is greater than that of the single control sample calibration. The present invention verifies and compares the deviation situations of the two calibration methods for detecting the same sample. For details, see Figure 7 。

[0058] The present invention uses two control samples to calibrate the standard analysis curve to establish a detection method, aiming to provide a more preferable method for correcting curve drift and matrix effect. The mathematical equation of the preferred calibration method provided by the present invention is: C’ = C + 1 / 2*(C1 - C1’ + C2 - C2’).

[0059] The present invention develops a detection method by using an optical emission spectrometer as a detection instrument, which can quickly detect tellurium elements in free-cutting stainless steel containing tellurium. The detection method of the present invention takes 4 - 10 minutes to detect the sample to be tested, which can effectively guarantee the refining time and feeding times of the industrial smelting of free-cutting stainless steel containing tellurium.

[0060] The time consumed by the detection method described in the present invention is as follows: sample processing takes 1 - 3 minutes, instrument analysis takes 2 - 5 minutes, and data processing takes 1 - 2 minutes, and the total time is 4 - 10 minutes. The detection time consumed by inductively coupled plasma emission spectrometry and oscillopolarography is as follows: sample processing takes 120 - 150 minutes, instrument analysis takes 3 - 10 minutes, and data processing takes 10 - 20 minutes, and the total time is 133 - 180 minutes.

[0061] In the sample processing stage of the detection methods using inductively coupled plasma emission spectrometers and polarographs, it is necessary to grind the surface of the steel sample to remove the oxide scale, then drill chips using a drill press, then weigh a quantitative chip sample using an analytical balance, and then heat and dissolve the chip sample in an acid solution. After dissolution, it is volumetrically fixed using a volumetric flask. The whole process is time-consuming, requires many devices, and has high operation requirements. In comparison, when using an optical emission spectrometer for detection in the sample processing stage, only the surface to be detected needs to be processed using a spectral grinding machine or a milling machine to make the surface flat and free of oxide scale, with the abrasive grain size being 60 - 120 mesh, and it only takes 1 - 3 minutes.

[0062] The durations of the three detection methods, namely inductively coupled plasma emission spectrometers, polarographs, and optical emission spectrometers, are similar in the instrument analysis stage. In the data processing stage, for the detection method using an optical emission spectrometer, the computer directly outputs the weight percentage of the tellurium element in the test sample, and then calculates the average value of the results of parallel tests as the detection result; while for the detection methods using inductively coupled plasma emission spectrometers and polarographs, the computer outputs the weight concentration of the element to be detected in the solution, and then calculates the weight percentage of the tellurium element in the test sample based on the sample weighing amount and the volumetric fixation and aliquot ratio in the relevant sample pretreatment, and then calculates the average value of the results of parallel tests as the detection result. In comparison, the optical emission spectrometer is faster than the other two methods in the data processing stage. Description of the Drawings

[0063] Figures 1 to 3 It is a verification diagram of the working spectral lines (wavelengths 214.28nm, 225.90nm, 238.58nm) of the tellurium element on the atomic emission optical emission spectrometer;

[0064] Figure 4 It is a trend diagram of the standard deviation of the intensity value changing with the pre - ignition time;

[0065] Figure 5 It is a trend diagram of the intensity ratio changing with the pre - ignition time;

[0066] Figure 6 It is a standard analysis curve diagram of tellurium;

[0067] Figure 7 It is a deviation comparison diagram of two calibration methods. Detailed Embodiments

[0068] The following further describes the present invention in combination with embodiments and drawings.

[0069] The rapid detection method for the tellurium content of the free - cutting stainless steel containing tellurium according to the present invention includes the following steps:

[0070] 1) Prepare at least 5 free - cutting stainless steel standard samples with tellurium content in the range of 0.0001 - 0.19 wt%;

[0071] 2) Select the working spectral line wavelength of tellurium on the atomic emission photoelectric direct-reading spectrometer in the range of 214.22 - 215.22 nm, and set the working pre-burning time of the atomic emission photoelectric direct-reading spectrometer to 21 - 45 seconds;

[0072] 3) Use the atomic emission photoelectric direct-reading spectrometer to analyze the light intensity of the standard sample, and establish a tellurium percentage content - light intensity standard analysis curve, namely the C-I standard analysis curve;

[0073] 4) Prepare one control sample respectively in two ranges of tellurium content of 0.025 - 0.035 wt% and 0.045 - 0.055 wt%;

[0074] 5) Use inductively coupled plasma emission spectrometry to detect the tellurium content of the two control samples, and the tellurium contents are C1 and C2 respectively;

[0075] 6) Use the atomic emission photoelectric direct-reading spectrometer to detect the light intensity values I1 and I2 of the tellurium element in the two control samples. The percentage contents of the tellurium element in the two control samples, namely C1' and C2', are calculated through the C-I standard analysis curve with the obtained light intensity values I1 and I2 of the tellurium element in the two control samples;

[0076] 7) Correct the C-I standard analysis curve to the C'-I standard analysis curve, where C' = C + 1 / 2 * (C1 - C1' + C2 - C2');

[0077] 8) Use the atomic emission photoelectric direct-reading spectrometer to detect the light intensity value I of the test sample S , and the obtained light intensity value I of the test sample S Calculate the percentage content C of the tellurium element in the test sample through the corrected C'-I standard analysis curve S .

[0078] Preferably, the tellurium content range of the standard sample is 0.0005 - 0.19 wt%.

[0079] Preferably, the working conditions of the atomic emission photoelectric direct-reading spectrometer are: argon gas flow rate ≥ 800 L / h, argon gas purity ≥ 99.999%, vacuum degree ≤ 2.0 Pa, tungsten electrode φ4 - 7 mm, 30 - 120° cone angle, analysis gap 3 - 6 mm, purge time 2 - 5 seconds, pre-burning time 21 - 45 seconds, integration time 10 - 20 seconds.

[0080] Preferably, in the step 3), the mathematical equation for establishing the C-I standard analysis curve is: C = 3.51558 * 10 -9 * I 2 + 1.09122 * 10 -5 * I - 4.847 * 10 -2, where C is the percentage content of tellurium in the standard sample, and I is the light intensity value of the standard sample.

[0081] Preferably, in step 7), the mathematical equation for establishing the corrected C’-I standard analysis curve is:

[0082] C’ = 3.51558*10 -9 *(I 2 -0.5*I1 2 -0.5*I2 2 ) + 1.09122*10 -5 *(I - 0.5*I1 - 0.5*I2) + 0.5*(C1 + C2)

[0083] where C’ is the percentage content of tellurium in the standard sample after correction, I is the light intensity value of the standard sample, I1 is the light intensity value detected by control sample 1, I2 is the light intensity value detected by control sample 2, C1 is the percentage content of tellurium in control sample 1, and C2 is the percentage content of tellurium in control sample 2.

[0084] Preferably, in step 2), the detector for tellurium in the atomic emission photoelectric direct-reading spectrometer uses a photomultiplier tube + filter.

[0085] Preferably, in step 2), the working spectral line wavelength of tellurium selected by the atomic emission photoelectric direct-reading spectrometer is λ = 214.28 nm.

[0086] Example 1 Establish an analytical method for the tellurium content of free-cutting stainless steel containing tellurium

[0087] Step 1) Prepare standard samples

[0088] 1.1 Use a small induction furnace as the heating equipment, and smelt and prepare 13 standard samples of free-cutting stainless steel containing tellurium with free-cutting stainless steel and pure tellurium as raw materials. The standard sample numbers are Te-00 to Te-12;

[0089] 1.2 Grind the surface of the prepared standard sample with a spectral grinding machine to remove the surface oxide layer, and drill chips on the bottom and side of the standard sample after cleaning; Preferably, the chip samples are detected by inductively coupled plasma emission spectrometry for tellurium content determination, and the determination results are shown in Table 2.

[0090] Table 2

[0091] Standard sample number Te-00 Te-01 Te-02 Te-03 Te-04 Te-05 Te-06 Te / % 0.0005 0.0006 0.0006 0.0008 0.0026 0.0038 0.0079 Standard sample number Te-07 Te-08 Te-09 Te-10 Te-11 Te-12 Te / % 0.014 0.019 0.035 0.043 0.12 0.19

[0092] Step 2) Use a QSG750-II atomic emission photoelectric direct-reading spectrometer, and find that the atomic emission characteristic spectral line wavelengths of tellurium element are:

[0093] λ1 = 214.28 nm, λ2 = 238.58 nm, λ3 = 225.90 nm, λ4 = 214.72 nm,

[0094] λ5 = 200.20 nm, λ6 = 238.32 nm, λ7 = 208.12 nm, λ8 = 199.42 nm,

[0095] λ9 = 225.55 nm, λ 10 = 226.56 nm.

[0096] According to the grating equation d(sinψ + sinθ) = nλ and the grating parameters and the diameter of the optical chamber of the instrument, the positions on the diaphragm corresponding to 10 wavelengths are calculated respectively, and a photomultiplier tube and a filter are installed at the vacant positions among the 10 positions;

[0097] Use the standard sample with the highest tellurium content (Te-12: 0.19%) in step 1) for tracing; select the position with the narrowest full width at half maximum and the highest peak value as the working spectral line of tellurium element by comparing the tracing curves at each position, see Figures 1 to 3 .

[0098] Turn on the QSG750-II type atomic emission photoelectric direct-reading spectrometer and set the working conditions:

[0099] The vacuum degree is pumped to ≤2.0 Pa, a tungsten electrode with φ6 mm and a 90° cone angle is used, the analysis gap of the excitation stage is 4 mm, the argon gas flow rate is 800 L / h, the purity is ≥99.999%, the purging time is 3 seconds, the pre-burning time is 3 seconds, and the integration time is 17 seconds.

[0100] Adjust the pre-burning time:

[0101] Change the pre-burning time. Under the conditions of pre-burning times of 3 s, 6 s, 9 s, 12 s, 15 s, 18 s, 21 s, 24 s, 27 s, 30 s, 33 s, 36 s, 39 s, 42 s, and 45 s respectively, the Te-04 and Te-12 samples in step 1) are excited 6 times respectively; record the intensity values of tellurium element at each pre-burning time of the two standard samples respectively; calculate the average value and relative standard deviation of the intensity of the Te-12 sample, and calculate the average value of the intensity of the Te-04 sample; make a trend graph of the standard deviation of the intensity value of the Te-12 sample changing with the pre-burning time, and make a trend graph of the intensity ratio of the Te-12 and Te-04 samples changing with the pre-burning time. The two trend graphs are shown in detail in Figure 4 , Figure 5 , as Figure 4 , Figure 5 It can be obtained that when the pre-burning time is 21 - 45 s, RSD ≤ 1.07%, and the intensity ratio is stable at 2.54.

[0102] Step 3) Establish the standard analysis curve of tellurium percentage content - light intensity, i.e., the C-I standard analysis curve

[0103] 3.1 Import of standard values and intensity registration of standard samples

[0104] Use a spectroscopic grinding machine to grind the bottom surface of the standard samples (Te-00 to Te-12) prepared in Step 1) with alumina sandpaper of 60-80 mesh to be flat, clean, and defect-free. Place the standard samples on the excitation stage, and select the curve intensity registration interface in the instrument analysis software to excite the standard samples 3 times, and register the average intensity of each standard sample for 3 times. Import the standard values of the standard samples into the standard sample database of the atomic emission photoelectric direct-reading spectrometer analysis software. The standard values and light intensity values of each standard sample are shown in Table 3.

[0105] Table 3

[0106] Standard sample number Light intensity value Tellurium content wt% Te-00 2409 0.0001 Te-01 2439 0.0006 Te-02 2478 0.0006 Te-03 2474 0.0007 Te-04 2553 0.0026 Te-05 2638 0.0038 Te-06 2763 0.0079 Te-07 3020 0.014 Te-08 3082 0.019 Te-09 3551 0.035 Te-010 3948 0.043 Te-011 5428 0.12 Te-012 6865 0.19

[0107] 3.2 Fitting of the standard analysis curve

[0108] Use the analysis software of the QSG750-II atomic emission photoelectric direct-reading spectrometer to fit the standard analysis curve and mathematical equation of tellurium element. See the curve fitting result in Figure 6 . The mathematical equation of the standard analysis curve of tellurium element is:

[0109] C = 3.51558*10 -9 *I 2 +1.09122*10 -5 *I - 4.847*10 -2

[0110] where C is the percentage content of tellurium element in the standard sample, and I is the light intensity value of the standard sample.

[0111] Step 4) Correct the C-I standard analysis curve to the C'-I standard analysis curve

[0112] 4.1 Preparation and value determination of control samples

[0113] According to the tellurium element control range of 0.01 - 0.07% in the industrial production process, prepare two control samples. Among them, the tellurium content of control sample K1 is designed at 0.028%, and the tellurium content of control sample K2 is designed at 0.055%. The preparation process and value determination are the same as those in Step 1) above. The chemical composition value determinations of control samples K1 and K2 are shown in Table 4.

[0114] Table 4

[0115] Name C(％) Mn (%) S(％) Cr(％) Te (%) K1 0.019 1.13 0.235 23.77 0.028 K2 0.020 0.97 0.263 23.56 0.055

[0116] Note: The balance is the Fe matrix and unavoidable trace elements.

[0117] 4.2 Calibrating the Standard Analysis Curve Using Control Samples

[0118] Grind the detection surfaces of the control samples K1 and K2 smoothly, cleanly, and defect - free using a spectroscopic grinding machine with alumina sandpaper of 60 - 80 mesh; import the standard values of the control samples into the material library of the analysis software of the atomic emission photoelectric direct - reading spectrometer respectively; detect the control samples K1 and K2 six times each in the standard analysis curve calibration interface of the analysis software, and record the average light intensity values of the six detections of K1 and K2 as I1 and I2. Denote the tellurium element contents of K1 and K2 as C1 (0.028%) and C2 (0.055%) as the set values, and adopt the mode of adding and calculating the arithmetic mean as the calibration method.

[0119] This detection method is named K - BJG, and the mathematical equation of the calibrated C’ - I standard analysis curve is: C’ = 3.51558×10 -9 *(I 2 - 0.5×I1 2 - 0.5×I2 2 ) + 1.09122×10 -5 *(I - 0.5×I1 - 0.5×I2)+0.5×(C1 + C2)

[0120] Among them, C’ is the percentage content of tellurium in the standard sample after calibration, I is the light intensity value of the standard sample, I1 is the light intensity value detected for sample K1, I2 is the light intensity value detected for sample K2, C1 is the percentage content of tellurium in sample K1, and C2 is the percentage content of tellurium in sample K2.

[0121] That is, use the atomic emission photoelectric direct - reading spectrometer with double control samples to detect the light intensity value I of the test sample S , and obtain the light intensity value I of the test sample S . Substitute it into the C’ - I standard analysis curve equation to obtain the percentage content of the tellurium element in the test sample.

[0122] C S = 3.51558×10 -9 *(I S 2 - 0.5×I1 2 - 0.5×I2 2 ) + 1.09122×10 -5 *(I S - 0.5×I1 - 0.5×I2)+0.5×(C1 + C2).

[0123] Example 2 Precision and Accuracy of the K - BJG Detection Method

[0124] 1. Precision of the K-BJG Detection Method

[0125] 1) Take 5 samples of tellurium-containing free-cutting stainless steel, numbered SY-01, SY-02, SY-03, SY-04, and SY-05; use a spectroscopic grinding machine and alumina sandpaper with a particle size of 60-80 mesh to grind the surfaces of control samples K1, K2, and the samples to be tested to be flat, clean, and defect-free; detect control samples K1 and K2 3 times at the calibration interface of the K-BJG detection method, take the average value of the 3 times for pre-detection calibration, and after calibration, detect the 5 samples 10 times at the K-BJG analysis interface respectively, and calculate the average value of the 10 times and the relative standard deviation RSD respectively.

[0126] Table 5 Unit: Weight percentage

[0127]

[0128] As shown in Table 5, for tellurium-containing free-cutting stainless steel samples with a tellurium content of 0.01-0.07% detected by the K-BJG detection method, the relative standard deviation is less than 3%.

[0129] 2. Accuracy of the K-BJG Detection Method

[0130] Use a spectroscopic grinding machine and alumina sandpaper with a particle size of 60-80 mesh to grind the surfaces of standard samples numbered SY-01, SY-02, SY-03, SY-04, SY-05 and control samples K1, K2 to be flat, clean, and defect-free; detect control samples K1 and K2 3 times at the calibration interface of the K-BJG detection method, take the average value of the 3 times for pre-detection calibration, and after calibration, detect the 5 standard samples 3 times at the analysis interface of the K-BJG detection method respectively, and calculate the average value of the 3 times of the 5 standard samples as the detection result; then detect the drill chips of the 5 standard samples by inductively coupled plasma emission spectrometry, and compare with the detection results of the method of the present invention as shown in Table 6.

[0131] Table 6 Unit: Weight percentage

[0132] Name SY-01 SY-02 SY-03 SY-04 SY-05 K-BJG test result 0.011 0.021 0.033 0.052 0.073 ICP test result 0.010 0.022 0.031 0.051 0.074 Deviation value <![CDATA 0.001 > <![CDATA 0.001 > <![CDATA 0.002 > <![CDATA 0.001 > <![CDATA 0.001 >

[0133] As shown in Table 6, for tellurium-containing free-cutting stainless steel samples with a tellurium content of 0.01-0.07% detected by the K-BJG detection method, the deviation of the tellurium content from the detection result of inductively coupled plasma emission spectrometry does not exceed 0.002%.

[0134] Example 3 Comparative Experiment on Detection Methods of Single Control Sample and Double Control Sample

[0135] 1. Establishment of the Single Control Sample Detection Method

[0136] 1.1 According to the control range of tellurium element in industrial production process, which is 0.01 - 0.07%, a control sample K0 is prepared, and the tellurium content of the control sample K0 is designed at 0.043%. The preparation process and its certification are the same as those in step 1) above. The certified chemical composition of the control sample K0 is shown in Table 7.

[0137] Table 7 Unit: weight percentage

[0138] Name C Mn S Cr Te ICP test result 0.018 1.08 0.247 23.82 0.043

[0139] 1.2 Use a spectroscopic grinding machine with alumina sandpaper of 60 - 80 mesh to grind the detection surface of the control sample K0 to be flat, clean and defect-free. Import the standard values of the control sample into the material library of the analysis software of the atomic emission photoelectric direct-reading spectrometer respectively. Calibrate the K0 sample 6 times on the calibration interface of the standard analysis curve in the analysis software, and register the average value of the light intensity of the 6 times as I0. Denote the tellurium element content of K0 as C0(0.043) as the set value, and adopt the summation mode as the calibration method. This detection method is named K-BJG-1, and the calibrated C-I standard analysis curve is C”-I, and its mathematical equation is:

[0140] C” = 3.51558 * 10 -9 *(I 2 -I0 2 ) + 1.09122 * 10 -5 *(I - I0) + C0

[0141] That is, use the atomic emission photoelectric direct-reading spectrometer to detect the light intensity value I S of the test sample with a single control sample, and obtain the light intensity value I S of the test sample. Substitute it into the C”-I standard analysis curve equation to obtain the percentage content of tellurium element in the test sample:

[0142] C S = 3.51558 * 10 -9 *(I S 2 -I0 2 ) + 1.09122 * 10 -5 *(I S -I0) + C0

[0143] 2. Precision test

[0144] The surfaces of the test samples numbered SY-01, SY-02, SY-03, SY-04, SY-05 and the K0 sample were ground smooth, clean and defect-free using a spectroscopic grinding machine with alumina sandpaper of 60-80 mesh. The control sample K0 was detected 3 times on the calibration interface of the K-BJG-1 detection method, and the average value of the 3 times was taken for pre-detection calibration. After calibration, the 5 samples were respectively detected 10 times on the K-BJG-1 analysis interface, and the average value of the 10 times and the relative standard deviation were calculated respectively. See Table 8.

[0145] Table 8 Unit: weight percentage

[0146]

[0147]

[0148] As can be seen from Table 5 and Table 8, for the tellurium-containing free-cutting stainless steel samples with tellurium content of 0.01-0.07 wt%, the relative standard deviation detected by the K-BJG detection method is ≤3%. For the K-BJG-1 detection method, the relative standard deviation of the tellurium-containing free-cutting stainless steel samples with tellurium content of 0.01-0.07 wt% is only 3.02% for the SY01 sample. This shows that the precision of these two analysis methods is basically the same.

[0149] 3. Accuracy test

[0150] The surfaces of the test samples numbered SY-01, SY-02, SY-03, SY-04, SY-05 and the K0 sample were ground smooth, clean and defect-free using a spectroscopic grinding machine with alumina sandpaper of 60-80 mesh; the control sample K0 was detected 3 times on the calibration interface of the K-BJG-1 detection method, and the average value of the 3 times was taken for pre-detection calibration. After calibration, the 5 samples were respectively detected 3 times on the K-BJG-1 analysis interface, and the average value of the 3 times of the samples was calculated respectively. The summary of the detection results of the samples by K-BJG, K-BJG-1 and ICP is shown in Table 9, and the deviation of the two methods from the ICP detection results is compared by a line chart in Figure 7 .

[0151] Table 9 Unit: weight percentage

[0152]

[0153]

[0154] From Table 9 and Figure 7It can be seen that the accuracy of the K-BJG detection method for detecting tellurium content in the ranges of 0.01 - 0.03% and 0.05 - 0.07% is better than that of the K-BJG-1 detection method, that is, the ability to correct the curve drift using double control samples is greater than that using single control samples.

Claims

1. A rapid detection method for the tellurium content of free-cutting stainless steel containing tellurium, characterized in that, It includes the following steps: 1) Prepare at least 5 free-cutting stainless steel standard samples with tellurium content in the range of 0.0001 - 0.19 wt%; 2) On the atomic emission photoelectric direct-reading spectrometer, select the working spectral line wavelength of tellurium in the range of 214.22 - 215.22 nm, and set the working pre-burning time of the atomic emission photoelectric direct-reading spectrometer to 21 - 45 seconds; 3) Use the atomic emission photoelectric direct-reading spectrometer to analyze the light intensity of the standard samples, and establish a tellurium percentage content - light intensity standard analysis curve, i.e., the C-I standard analysis curve; 4) Prepare one control sample respectively in two ranges of tellurium content of 0.025 - 0.035 wt% and 0.045 - 0.055 wt%; 5) Use inductively coupled plasma emission spectrometry to detect the tellurium content of the two control samples, and the tellurium contents are C1 and C2 respectively; 6) Use the atomic emission photoelectric direct-reading spectrometer to detect the light intensity values I1 and I2 of tellurium element in the two control samples, and calculate the percentage contents of tellurium element in the two control samples as C1' and C2' respectively through the C-I standard analysis curve with the obtained light intensity values I1 and I2 of tellurium element in the two control samples; 7) Correct the C-I standard analysis curve to the C'-I standard analysis curve, where C' = C + 1 / 2 * (C1 - C1' + C2 - C2'); 8) Detect the light intensity value I of the test sample using an atomic emission photoelectric direct-reading spectrometer S , and obtain the light intensity value I of the test sample S Calculate the percentage content C of tellurium element in the test sample by using the corrected C’-I standard analysis curve S .

2. The rapid detection method for the tellurium content of the free-cutting stainless steel containing tellurium according to claim 1, characterized in that, The tellurium content range of the standard samples is 0.0005 - 0.19 wt%.

3. The rapid detection method for the tellurium content of the free-cutting stainless steel containing tellurium according to claim 1, characterized in that, The working conditions of the atomic emission photoelectric direct-reading spectrometer are: argon gas flow rate ≥ 800 L / h, argon gas purity ≥ 99.999%, vacuum degree ≤ 2.0 Pa, tungsten electrode φ4 - 7 mm, 30 - 120° cone angle, analysis gap 3 - 6 mm, purge time 2 - 5 seconds, pre-burning time 21 - 45 seconds, integration time 10 - 20 seconds.

4. The rapid detection method for the tellurium content of the free-cutting stainless steel containing tellurium according to claim 1, characterized in that, In step 3), the mathematical equation for establishing the C-I standard analysis curve is: C = 3.51558*10 -9 *I 2 + 1.09122*10 -5 *I - 4.847*10 -2 , where C is the percentage content of tellurium element in the standard sample, and I is the light intensity value of the standard sample.

5. The rapid detection method for the tellurium content of the free-cutting stainless steel containing tellurium according to claim 1, characterized in that, For step 7), the mathematical equation established for the corrected C'-I standard analysis curve is: C’ = 3.51558 * 10 -9 *(I 2 - 0.5 * I1 2 - 0.5 * I2 2 ) + 1.09122 * 10 -5 *(I - 0.5 * I1 - 0.5 * I2) + 0.5 * (C1 + C2) Where C' is the percentage content of tellurium in the standard sample after correction, I is the light intensity value of the standard sample, I1 is the light intensity value detected for control sample 1, I2 is the light intensity value detected for control sample 2, C1 is the percentage content of tellurium in control sample 1, and C2 is the percentage content of tellurium in control sample 2.

6. The rapid detection method for the tellurium content of the free-cutting stainless steel containing tellurium according to claim 1, characterized in that, In step 2), the detector of tellurium in the atomic emission photoelectric direct-reading spectrometer uses a photomultiplier tube + filter.

7. The rapid detection method for the tellurium content of the free-cutting stainless steel containing tellurium according to claim 1 or 6, characterized in that, In step 2), the working spectral line wavelength of tellurium selected by the atomic emission photoelectric direct-reading spectrometer is λ = 214.28 nm.

Images