INTERSTATE STANDARD

STEEL

METHOD OF PHOTOELECTRIC SPECTRAL ANALYSIS

Official publication

INTERSTATE COUNCIL FOR STANDARDIZATION, METROLOGY AND CERTIFICATION

Preface

1 DEVELOPED by the Russian Federation, Interstate Technical Committee MTK 145 “Methods of control of metal products”

INTRODUCED by Gosstandart of Russia

2 ADOPTED by the Interstate Council for Standardization, Metrology and Certification (protocol N° 11-97 of April 25, 1997)

3 Resolution of the State Committee Russian Federation on standardization, metrology and certification dated September 23, 1997 No. 332, the interstate standard GOST 18895-97 was put into effect directly as state standard Russian Federation since January 1, 1998

4 INSTEAD GOST 18895-81

© IPC Standards Publishing House, 1998

This standard cannot be fully or partially reproduced, replicated and distributed as an official publication on the territory of the Russian Federation without the permission of the State Standard of Russia

1 Scope of application................................................... .........1

3 Sampling and preparation...................................................

4 Equipment and materials...................................................

5 Preparation for analysis....................................................

6 Conducting the analysis...................................................

7 Processing the results...................................................

Appendix A Conditions for carrying out analysis on photovoltaic installations......8

INTERSTATE STANDARD

Photoelectric spectral analysis method

Steel. Method of photoelectric spectral analysis

Date of introduction 1998-01-01

I AREA OF APPLICATION

This standard establishes a photoelectric spectral method for determining the mass fraction of elements in steel, %:

The method is based on the excitation of atoms of steel elements by an electric discharge, decomposition of the radiation into a spectrum, measurement of analytical signals proportional to the intensity or logarithm of the intensity of spectral lines, and subsequent determination of the mass fractions of elements using calibration characteristics.

GOST 8.315-97 GSI. Standard samples of the composition and properties of substances and materials. Basic provisions

GOST 859-78 Copper. Stamps

GOST 2424-83 Grinding wheels. Specifications GOST 6456-82 Sanding paper. Technical specifications GOST 7565-81 (ISO 377-2-89) Cast iron, steel and alloys. Sampling method for chemical composition

GOST 10157-79 Argon gaseous and liquid. Technical specifications GOST 21963-82 Cutting wheels. Specifications

Official publication

3 SAMPLE SELECTION AND PREPARATION

Selection and preparation of samples - in accordance with GOST 7565 with addition. The sample surface intended for searching is ground flat. Holes, slag inclusions, tarnished colors and other defects are not allowed on the surface.

4 EQUIPMENT AND MATERIALS

Photoelectric vacuum and air installations with individual calibration.

Cutting machine types 8230 and 2K337.

Grinding machine model ZE881.

Sharpening and grinding machine (grinding and emery machine) type TSCH-500.

Universal machine for sharpening electrodes model KP-35.

Screw-cutting lathe Model 1604.

Cutting discs 400 x 4*x 32 mm according to GOST 21963.

Electrocorundum abrasive wheels with a ceramic binder, grain size No. 50, hardness ST-2, dimensions 300 x 40 x 70 mm according to GOST 2424.

Sanding paper type 2 on paper grade BSh-200 (P7) from normal corundum with a grain size of 40-60 according to GOST 6456.

Argon gas of the highest grade according to GOST 10157.

Electric furnace for drying and cleaning argon type SUOL-0.4.4/12-N2-U4.2.

In the case of using vacuum photovoltaic installations, permanent electrode rods of silver, copper and tungsten with a diameter of 5-6 mm or tungsten wire with a diameter of 1-2 mm and a length of at least 50 mm are used.

For airborne photovoltaic installations, copper rods of grades M00, Ml, M2 according to GOST 859 and carbon rods of grade SZ with a diameter of 6 mm and a length of at least 50 mm are used.

To determine the mass fraction of elements in rolled steel, vacuum and air photovoltaic installations are used. If the sample does not completely cover the hole in the vacuum setup stand, use a contact chamber (see Figure 1) or another device that limits the hole in the stand table.

Figure 1 - Contact chamber for a vacuum spectrometer

It is allowed to use other equipment, equipment and materials that ensure the accuracy of analysis provided for by this standard.

5 PREPARATION FOR ANALYSIS

5.1 Preparation of the installation for measurements is carried out in accordance with the instructions for maintenance and operation of the installation.

5.2 Calibration of each photovoltaic installation is carried out experimentally when introducing a measurement technique using reference standards (RM) of composition, certified in accordance with GOST 8.315.

It is allowed to use homogeneous samples analyzed by standardized or certified methods of chemical analysis,

5.3 During the initial calibration, at least five series of measurements are performed on different days of operation of the photovoltaic installation. In a series, for each RM, two pairs of parallel (performed one after the other on the same surface) measurements are carried out. The order of pairs of parallel measurements for all SDs in the series is randomized. The arithmetic mean value of the analytical signals for the series and the arithmetic mean value of the analytical signals for five series of measurements for each reference standard are calculated.

Calibration characteristics are established by calculation or graphically, which are expressed in the form of a formula, graph or table. Calibration characteristics are used to determine the mass fractions of controlled elements directly or taking into account the influence of the chemical* composition and physical and chemical properties of the object.

For installations interfaced with a computer, the calibration procedure is determined software. In this case, the accuracy of the analysis results must meet the requirements of this standard.

5.4 When repeating calibration, it is allowed to reduce the number of series to two.

5.5 In the case of operational calibration (obtaining calibration characteristics with each batch of analyzed samples), at least two parallel measurements are performed for each RM.

6 CONDUCTING THE ANALYSIS

6.1 The conditions for conducting analysis on photovoltaic installations are given in Appendix A (Tables AL, A.2).

6.2 The wavelengths of spectral lines and the range of mass fractions of elements are given in Appendix A (Table A.3).

6.3 Perform two parallel measurements of the analytical signal values ​​for each controlled element of the analyzed sample under the conditions adopted during calibration. Three parallel measurements are allowed.

7 PROCESSING RESULTS

7.1 If the discrepancy between the values ​​of the analytical signal, expressed in units of mass fraction, is no more than d cx (Table 1) for two parallel measurements and 1.2 d cx for three parallel measurements, calculate the arithmetic mean value.

It is allowed to express the value of the analytical signal and the discrepancies of parallel measurements in units of the scale of the reading and recording device of the photovoltaic installation. In this case, d cx is expressed in units of the scale of the reading and recording device using established calibration characteristics.

If the discrepancies between parallel measurements exceed the permissible values ​​d cx (1.2 d cx), the analysis is repeated.

7.2 The final result of the analysis is taken as the arithmetic mean of two or three parallel measurements that meet the requirements of 7.1.

7.3 Monitoring the stability of analytical results

7.3.1 Monitoring the stability of calibration characteristics for the upper and lower limits of the measurement range is carried out at least once per shift using RM or homogeneous samples. It is allowed to carry out monitoring only for the upper limit or middle of the measurement range.

For CO (sample), two parallel measurements of the analytical signal are performed. The values ​​of the analytical signal N are expressed in units of mass fraction or scale of the reading and recording device of the photovoltaic installation.

7.3.2 If the discrepancy between the values ​​of the analytical signal for parallel measurements does not increase d cx (Table 1), calculate the arithmetic mean value N and the difference AN = N$ - N> where N 0 is the value of the analytical signal for the CO (sample), obtained by the method specified in 5.3.

Table 1 - Norms and standards for accuracy control

End of table 1

7.3.3 If AN exceeds the permissible value 5^ (Table 1), measurements are repeated in accordance with 7.3.1. If during repeated measurements AN exceeds the permissible value, the calibration characteristic is restored. The procedure for restoring the calibration characteristic for each installation is determined by its analytical and design capabilities.

7.3.4 Extraordinary stability control is carried out after repair or maintenance of a photovoltaic installation.

7.3.5 During operational calibration, stability control is not carried out.

7.3.6 For installations interfaced with a computer, the stability control procedure is determined by the software. In this case, the accuracy of the analysis results must meet the requirements of this standard.

7.4 Monitoring the reproducibility of analytical results

7.4.1 Monitoring the reproducibility of the results of spectral analysis is carried out by determining the mass fractions of elements in previously analyzed samples.

7.4.2 The number of repeated determinations must be at least 0.3% of the total number of determinations during the controlled period.

7.4.3 The reproducibility of measurements is considered satisfactory if the number of discrepancies between the primary and repeated analyzes exceeding the permissible value (Table 1) is no more than 5% of the number of controlled results.

7.5 Monitoring the accuracy of analysis results

7.5.1 Accuracy control is carried out by selective comparison of the results of spectral analysis of samples with the results of chemical analysis performed by standardized or certified methods.

7.5.2 The number of results during accuracy control must be at least 0.3% of the total number of determinations during the controlled period.

7.5.3 The accuracy of measurements is considered satisfactory if the number of discrepancies in the results of spectral and chemical analysis exceeding the permissible value (Table 1) is no more than 5% of the number of controlled results.

7.5.4 It is permissible to carry out verification of correctness using the method of spectral analysis based on reproducing the values ​​of the mass fractions of elements in the enterprise’s RM.

7.6 When meeting the requirements of this standard, the error of the analysis result (with a confidence probability of 0.95) should not exceed the limit value A (Table 1).

Conditions for analysis in photovoltaic installations

Table A.1

Table A.2

Note - Parameters are selected within the specified values

Table A.3

Continuation of table L.Z

End of table A 3

Note - Lines are selected specifically for the analytical technique depending on their I intensity, type of photovoltaic installation, overlap of other lines, placement possibilities; exit slots on the device carriages_

UDC 669.14.001.4:006.354 MKS 77.080.40 V39 OKSTU 0809

Key words: steel, analysis, photoelectric spectral method, sample, equipment, materials, result, error of results

Editor L I Nakhimova Technical editor V I Prusakova Proofreader RA Mentova Computer layout A N Zolotareva

Issued by persons No. 021007 dated 10 08 95 Handed over to the set 03 12 97 Signed for printing 27 02 98 Uslpechl 1.86 Uch-izdl 1.40

Circulation 335 copies С 1226 Zak 899

IPC Publishing House of Standards 107076, Moscow, Kolodezny Lane, 14 Typed at the Publishing House on a PC

Branch of IPK Publishing House of Standards - type “Moscow Printer” Moscow, Lyalin lane, 6

Atomic emission spectral analysis is the most widely used method for determining elemental abundances in a wide variety of natural and artificial materials. With its help, you can analyze solid, liquid and gaseous substances for almost all chemical elements, from alkaline earth metals to inert gases. The multi-element nature of the method, as well as the fairly low detection limits of elements, combined with the relatively low cost of analysis and the ease of its implementation, place it in the category of essential for any analytical laboratory that claims to perform a wide range of analytical work.

The emission spectrum of the sample, excited in a light source, is recorded using a spectrograph, spectroscope or spectrometer (monochromator or polychromator). In this regard, all methods of conducting atomic emission spectral analysis can be divided into three groups: spectrographic, visual and spectrometric (with photoelectric recording of the spectrum). Methodologically, each of these groups has its own specifics associated with the method of recording the analytical signal and obtaining information about the presence and content of the determined elements in the analyzed samples. Along with this, some methodological techniques developed for one group of methods can be successfully applied to another group with minor modifications that take into account the specifics of spectrum registration.

Spectrographic analysis

Registration of the atomic emission spectrum of a sample on a photographic plate allows one to obtain a very large amount of information about the elemental composition of the analyzed object. However, very often the task of analysis does not include extracting all the information contained in the photographed spectrum. It is enough to have information, for example, about the qualitative elemental composition of the sample or about the quantitative content of certain elements in it. In accordance with this, spectrographic analysis is divided into two types: qualitative and quantitative.

Qualitative analysis

When conducting high-quality atomic emission spectral analysis, three types of problems can be distinguished:

1. general qualitative analysis to determine the component composition of the sample;
2. private qualitative analysis, with the help of which the presence or absence of one or more desired (predetermined) elements in a given sample is established;
3. qualitative analysis of trace elements, allowing to determine the presence of polluting or impurity elements in small concentrations in a sample of the analyzed material.

To perform high-quality atomic emission spectral analysis, an arc light source is most often used, in which the resonant spectral lines of the atoms of the vast majority of the elements of the periodic table are excited. Mendeleev. Due to the fact that the emission spectrum of an arc discharge has been sufficiently well studied, an experienced spectrum analyst can determine the elemental composition of the analyzed sample from the density of blackening of the spectral lines recorded on a photographic plate and make an approximate estimate of the content of individual components in it.

Qualitative analysis of metals and alloys is carried out with the excitation of the spectrum in an alternating current arc at a current strength of 5-10 A. In this case, one of the electrodes (usually the bottom) is the analyzed sample, and the other electrode is made from a carbon, aluminum or copper rod by sharpening its end to cone. If it is not necessary to determine trace element contents, then for general qualitative analysis of metal samples, along with excitation in an alternating current arc, spark excitation of the spectrum can be used. In the latter case, a resistance R ≈ 100 Ohm is included in the discharge circuit of the low-voltage spark electrical power generator (U = 1 kV, C = 50 μF, L = 100 μH), which makes the discharge damped. The spectrum of such a light source is close to the arc spectrum in terms of the nature of the emission of spectral lines and is therefore more convenient for deciphering and conducting qualitative analysis. When analyzing monolithic metal samples, multi-stage photography is not used, since it is obvious that the spectra obtained in this case will be identical. However, the sample should still be searched before spectrum exposure.

The high-voltage spark (U = 12 kV, C = 10 µF, L = 500 µH) is also suitable for general qualitative analysis of metals and alloys, when it is not necessary to determine elements with a content of less than 10–20%. In this case, an increase in inductance has a beneficial effect on the detection of elements with low excitation energies.

Semi-quantitative analysis

The semi-quantitative method of spectrographic analysis includes techniques that not only determine the presence of any elements in a sample, but also approximately determine their content. An important feature of this method is the speed of its implementation, therefore it is used mainly to solve such analytical problems for which the speed of analysis is more important than its accuracy.

The methodological foundations and a number of methods for conducting semi-quantitative analysis were developed back in the 20–30s, i.e., during the period of transition from qualitative to quantitative spectrographic analysis. Semi-quantitative analysis, which is essentially a type of quantitative spectral analysis, is methodically based on a subjective (visual) comparison of the intensities of spectral lines either in the spectrum of the analyzed sample or in the spectra of the analyzed and reference samples.

Method of appearance and strengthening of lines

It is obvious that with a decrease in the concentration of any element in a series of samples of the same macro-composition, the intensity of the spectral lines of the element in the corresponding spectra will decrease, provided that the parameters of excitation and recording of the spectra remain unchanged. Since the spectral lines belonging to the element being determined have different intensities, as its concentration decreases, the weaker lines will disappear in the spectrum earlier than the more intense ones. As a result, based on the absence in the spectra of some and the presence of other, more intense, lines of a given element, one can draw a conclusion about its concentration in the sample.

Spectrum comparison method

The essence of the spectral comparison method is that the blackening densities of the spectral lines of the determined elements in the spectrum of the sample are compared with those in the spectra of several reference samples that contain these elements in different concentrations. To do this, a certain number of spectra of the analyzed sample are simultaneously photographed on a photographic plate using a Hartmann diaphragm so that between these spectra there remain horizontal unexposed strips of photographic emulsion with a width equal to the height of the spectral lines.

The method of comparing spectra is very convenient when it is necessary to obtain an answer to the question: a given element is present in the analyzed sample in a concentration higher or lower than a given concentration. To carry out such an analysis, it is enough to have the spectrum of one reference sample, the content of the element in which is equal to the limit concentration. Carefully developed methods make it possible to determine the concentration of an element in a sample using the method considered with an error of 15-20%.

Method of stepwise attenuation of spectral lines (Clair method)

The stepwise attenuation method is based on the fact that the intensity of spectral lines photographed during excitation of the spectrum of one analyzed sample is reduced stepwise in height using a special attenuator placed directly in front of the entrance slit of the spectrograph. Based on a visual examination of the spectral lines in the spectra of standard samples photographed in this way, it is possible to compile tables or plot the dependence of the number of observed steps for the analytical lines of elements on their concentration in the sample.

Quantitative Analysis

The task of quantitative spectral analysis is to determine the quantitative content of the elements under study in a sample based on the relative intensity of the analytical pair of lines.

Quantitative spectral analysis is based on the fact that the intensity of the spectral lines of the element being determined is related to its concentration. However, the intensity of spectral lines depends not only on the concentration of the analyzed element, but also on a number of other factors, which are practically impossible to take into account. In this regard, changing the absolute intensities of spectral lines is a difficult task, and the results of quantitative determinations based on measuring the absolute intensities of spectral lines cannot be considered sufficiently reliable. Therefore, in practice, quantitative spectral analysis is carried out by measuring the relative intensity of two lines: the analytical and the comparison line. The lines of an element whose content in the sample is constant are selected as comparison lines. Such a pair of lines must meet the homology condition, i.e. their relative intensity should depend little on the excitation conditions. This is possible if:

1. both lines have the same or similar excitation potentials;
2. the ionization potentials of atoms of elements that produce an analytical pair of lines are also very close.

In this case, the intensities of both lines should not differ sharply from each other.

Three standards method

To ensure the uniformity of elemental composition measurements, in particular, state standard samples (GSO) are used by the method of atomic spectral analysis. Without touching on the procedure for certifying the elemental composition of GSO, it should be noted that these samples are a kind of And if, on an industry or individual enterprise scale, methods are developed and used based on the use of reference samples produced in-house, then these samples must be compared (or correlated) with GSO. If such a correlation is impossible for some reason (for example, there is no state standard standard for the analyzed objects), then industry standard samples (IRM) or enterprise standard samples (SOP) must be certified accordingly.

Along with the reference samples mentioned above, in the practice of spectral analysis, working reference samples are used, which are produced, for example, weekly due to high consumption or instability of their chemical composition over time. For these samples, it is necessary to have a certified method for their preparation or, if possible, their composition should be compared with SOP, OCO or GSO. The criteria for objective assessment of the conformity of the composition when certifying or comparing comparison samples of different levels are based on methods of statistical processing of measurement results.

The method of reference samples, or the method of three standards, consists in the fact that according to the method used for analysis, along with the spectra of the analyzed samples, the spectra of several, but not less than three, comparison samples are photographed on the same photographic plate. These spectra measure the analytical signals of the element being determined, the content of which is known in the reference samples. Next, a calibration dependence is constructed, according to which the content of the measured element is determined for the analytical signal of the analyzed sample.

Visual spectral analysis

The visual method of atomic emission spectral analysis differs from spectrographic and photometric analysis, primarily in that observation of the spectrum and measurement of the relative intensities of spectral lines in it are subjective, since the direct receiver of radiation is the eye of a particular person. The visible region of the spectrum used in this method, from approximately 400 to 760 nm, greatly limits the analytical capabilities in terms of detection limits, since the most sensitive spectral lines of elements, with the exception of alkali and alkaline earth metals, are in the shorter wavelength region of the spectrum. Nevertheless, the visual method of analysis is widely used in spectroanalytical practice due, first of all, to methodological simplicity, high speed and expressness of determinations, and low cost of analysis. The most important area of ​​application of the visual spectral analysis method is monitoring the content of alloying and other impurities in metal alloys and steels during the production process or for sorting. In addition, the method is used for the analysis of dielectric powder samples, liquids and solutions, and even gas mixtures.

To carry out analysis with visual recording of the spectrum, mainly prism instruments called spectroscopes are used, which are divided into two types: styloscopes and stylometers. Stylometers, unlike steeloscopes, are equipped with a photometric device that allows not only to examine the spectrum of the sample under study, but also to measure the relative intensities of spectral lines. In addition, the optical design of the stylometer creates two identical spectra in the observer’s field of view from one light source, which can be shifted relative to each other and thereby establish the analytical line and the comparison line next to each other.

Spectral analysis with photoelectric spectrum recording

Analysis with photoelectric recording of the spectrum (spectrometric analysis), just like visual analysis, differs from the spectrographic method in the speed of obtaining analytical information about the sample, since it is based on direct photometry of the intensities of spectral lines directly during operation of the light source. Moreover, unlike the visual method, analysis with photoelectric recording is an objective method. Another very important feature of this method is that it allows for almost complete automation of the analytical process, including processing the analytical signal on a PC and issuing analysis results in archived form.

For the first time, photoelectric recording of the spectrum was used in the 20s by G. Lundegard, measuring the intensities of spectral lines emitted by a flame using a photocell. Currently, all produced flame photometers are equipped with a photoelectric spectrum recording unit.

In the early 40s, ARL and Baird designed and manufactured the first multichannel installations, which were later called quantum meters. In these installations, a polychromator is used as a spectral device, which has many output slits, behind which photocells or photomultipliers are installed. The number of output slits in modern quantum meters produced by different companies can range from several tens to hundreds.

For quite a long time, the main purpose of quantum meters was atomic emission spectral analysis of steels and alloys. Therefore, the light sources that equipped these installations were an alternating current arc and a spark discharge. However, with the advent of a light source with inductively coupled plasma, a number of foreign and domestic instrument-making companies began to produce multichannel installations called ICP spectrometers. Since solutions of a wide variety of materials and substances, as well as natural and industrial waters, can be analyzed in an inductively coupled plasma light source, the use of these installations for multi-element atomic emission spectral analysis has significantly expanded in relation to the objects of analysis.

An important attribute of modern quantum meters is a computer, which not only processes analytical signals coming from the photomultiplier to the recording device and calculates concentrations and errors in their determination, but also controls the operation of all installation systems. Calibration data for various materials, as well as analysis results, which can be requested at any time, are stored in the computer memory.

There are and are widely used atomic emission spectrometers, in which photodiode matrices are used to record the spectrum, installed in the focal plane of the spectrograph camera lens instead of a photographic plate. The registration process using a photodiode array, controlled via a computer, occurs in three stages. At the first stage, the duration of which is about 1 ms, the accumulation of photoelectric potential occurs on all elements of the matrix. The second stage is reading the information accumulated on individual photodiodes about the amount of light flux incident on them (1 μs). The third stage completes the radiation registration cycle by erasing all information contained in the photodiode cells of the matrix by zeroing their potentials and bringing the matrix to its original state (1 μs). Since the longest, as we see, is the first registration stage, the duration of one cycle as a whole is determined precisely by the accumulation stage and is approximately 1 ms. Thus, approximately 103 cycles of recording the spectral region covered by one matrix occur in one second. If it is necessary to record the spectrum in a wider range of wavelengths, then two or more matrices installed side by side in the same plane are used. In this case, the time of each registration cycle increases in proportion to the number of matrices used.

The use of photodiode matrices, which are called CCD boards, in photometric atomic emission spectral analysis makes it possible to combine in one registration method the advantages of photoelectric registration and registration using a photographic plate, including the accumulation of spectra of analyzed samples in computer memory. The latter circumstance opens up wide opportunities for creating a data bank on the spectra of a wide variety of samples.

INTERSTATE STANDARD

STEEL

METHOD OF PHOTOELECTRIC SPECTRAL ANALYSIS

INTERSTATE COUNCIL
ON STANDARDIZATION, METROLOGY AND CERTIFICATION
Minsk

Preface

1 DEVELOPED by the Russian Federation, Interstate Technical Committee MTK 145 “Methods of control of metal products”

INTRODUCED by Gosstandart of Russia

2 ADOPTED by the Interstate Council for Standardization, Metrology and Certification (Protocol No. 11-97 of April 25, 1997)

3 By Decree of the State Committee of the Russian Federation for Standardization, Metrology and Certification dated September 23, 1997 No. 332, the interstate standard GOST 18895-97 was put into effect directly as the state standard of the Russian Federation on January 1, 1998.

INTERSTATE STANDARD

STEEL

Photoelectric spectral analysis method

Steel. Method of photoelectric spectral analysis

Date of introduction 1998-01-01

1 AREA OF APPLICATION

This standard establishes a photoelectric spectral method for determining the mass fraction of elements in steel, %:

carbon from 0.010 to 2.0;

sulfur » 0.002 » 0.20;

phosphorus » 0.002 » 0.20;

silicon » 0.010 » 2.5;

manganese » 0.050 » 5.0;

chromium » 0.010 » 10.0;

nickel » 0.010 » 10.0;

cobalt » 0.010 » 5.0;

copper » 0.010 » 2.0;

aluminum » 0.005 » 2.0;

arsenic » 0.005 » 0.20;

molybdenum » 0.010 » 5.0;

tungsten » 0.020 » 5.0;

vanadium » 0.005 » 5.0;

titanium » 0.005 » 2.0;

niobium » 0.010 » 2.0;

boron » 0.001 » 0.10;

zirconium » 0.005 » 0.50.

The method is based on the excitation of atoms of steel elements by an electric discharge, decomposition of the radiation into a spectrum, measurement of analytical signals proportional to the intensity or logarithm of the intensity of spectral lines, and subsequent determination of the mass fractions of elements using calibration characteristics.

2 REGULATORY REFERENCES

Electrocorundum abrasive wheels with ceramic bond, grit number 50, hardness ST-2, size 300x40x70 mm according to GOST 2424.

Sanding paper type 2 on paper grade BSh-200 (P7) from normal electrocorundum with a grain size of 40 - 60 according to GOST 6456.

Argon gas of the highest grade according to GOST 10157.

Electric furnace for drying and cleaning argon type SUOL-0.4.4/12-N2-U4.2.

In the case of using vacuum photovoltaic installations, permanent rod electrodes of silver, copper and tungsten with a diameter of 5 - 6 mm or tungsten wire with a diameter of 1 - 2 mm and a length of at least 50 mm are used.

For airborne photovoltaic installations, copper rods of grades M00, M1, M2 according to GOST 859 and carbon rods of grade C3 with a diameter of 6 mm and a length of at least 50 mm are used.

To determine the mass fraction of elements in rolled steel, vacuum and air photovoltaic installations are used. If the sample does not completely cover the hole in the vacuum setup stand, use a contact chamber (see Figure 1) or another device that limits the hole in the stand table.

1 - gaskets; 2 - plate; 3 - spring; 4 - contact

Figure 1 - Contact chamber for a vacuum spectrometer

It is allowed to use other equipment, equipment and materials that ensure the accuracy of analysis provided for by this standard.

5 PREPARATION FOR ANALYSIS

5.1 Preparation of the installation for measurements is carried out in accordance with the instructions for maintenance and operation of the installation.

5.2 Calibration of each photovoltaic installation is carried out experimentally when introducing a measurement technique using standard samples (RM) of composition certified in accordance with GOST 8.315.

It is permissible to use homogeneous samples analyzed using standardized or certified methods of chemical analysis.

5.3 During the initial calibration, at least five series of measurements are performed on different days of operation of the photovoltaic installation. In a series, for each RM, two pairs of parallel (performed one after the other on the same surface) measurements are carried out. The order of pairs of parallel measurements for all SDs in the series is randomized. The arithmetic mean value of the analytical signals for the series and the arithmetic mean value of the analytical signals for five series of measurements for each reference standard are calculated.

Calibration characteristics are established by calculation or graphically, which are expressed in the form of a formula, graph or table. Calibration characteristics are used to determine the mass fractions of controlled elements directly or taking into account the influence of the chemical composition and physical and chemical properties of the object.

For installations interfaced with a computer, the calibration procedure is determined by the software. In this case, the accuracy of the analysis results must meet the requirements of this standard.

5.4 When repeating calibration, it is allowed to reduce the number of series to two.

5.5 In the case of operational calibration (obtaining calibration characteristics with each batch of analyzed samples), at least two parallel measurements are performed for each RM.

6 CONDUCTING THE ANALYSIS

6.1 The conditions for conducting analysis on photovoltaic installations are given in Appendix A (Tables A.1, A.2).

6.2 The wavelengths of spectral lines and the range of mass fractions of elements are given in Appendix A (Table A.3).

6.3 Perform two parallel measurements of the analytical signal values ​​for each controlled element of the analyzed sample under the conditions adopted during calibration. Three parallel measurements are allowed.

7 PROCESSING RESULTS

7.1 If the discrepancy between the values ​​of the analytical signal, expressed in units of mass fraction, is no more than d cx(Table 1) for two parallel measurements and 1.2 d cx for three parallel measurements, calculate the arithmetic mean.

It is allowed to express the value of the analytical signal and the discrepancies of parallel measurements in units of the scale of the reading and recording device of the photovoltaic installation. In this case d cx expressed in units of the scale of the reading and recording device using established calibration characteristics.

If the discrepancies between parallel measurements exceed the permissible values d cx(1,2d cx) the analysis is repeated.

7.2 The final result of the analysis is taken as the arithmetic mean of two or three parallel measurements that meet the requirements of 7.1.

7.3 Monitoring the stability of analytical results

7.3.1 Monitoring the stability of calibration characteristics for the upper and lower limits of the measurement range is carried out at least once per shift using RM or homogeneous samples. It is allowed to carry out monitoring only for the upper limit or middle of the measurement range.

For CO (sample), two parallel measurements of the analytical signal are performed. Analytical signal values N expressed in units of mass fraction or scale of the reading and recording device of a photovoltaic installation.

7.3.2 If the discrepancy between the values ​​of the analytical signal for parallel measurements does not exceed d cx(Table 1), calculate the arithmetic mean and difference D N=N 0 - , Where N 0 - the value of the analytical signal for CO (sample), obtained by the method specified in 5.3.

Table 1 - Norms and standards for accuracy control

7.3.3 If D N exceeds the permissible value δ st (table 1), measurements are repeated in accordance with 7.3.1. If during repeated measurements D N exceeds the permissible value, the calibration characteristic is restored. The procedure for restoring the calibration characteristic for each installation is determined by its analytical and design capabilities.

7.3.4 Extraordinary stability control is carried out after repair or maintenance of a photovoltaic installation.

7.3.5 During operational calibration, stability control is not carried out.

7.3.6 For installations interfaced with a computer, the stability control procedure is determined by the software. In this case, the accuracy of the analysis results must meet the requirements of this standard.

7.4 Monitoring the reproducibility of analytical results

7.4.1 Monitoring the reproducibility of the results of spectral analysis is carried out by determining the mass fractions of elements in previously analyzed samples.

7.4.2 The number of repeated determinations must be at least 0.3% of the total number of determinations during the controlled period.

7.4.3 Measurement reproducibility is considered satisfactory if the number of discrepancies between the primary and re-analysis exceeds the permissible value d V (Table 1) constitutes no more than 5% of the number of monitored results.

7.5 Monitoring the accuracy of analysis results

7.5.1 Accuracy control is carried out by selective comparison of the results of spectral analysis of samples with the results of chemical analysis performed by standardized or certified methods.

7.5.2 The number of results during accuracy control must be at least 0.3% of the total number of determinations during the controlled period.

7.5.3 The accuracy of measurements is considered satisfactory if the number of discrepancies between the results of spectral and chemical analysis exceeds the permissible value d n (Table 1) constitutes no more than 5% of the number of monitored results.

7.5.4 It is permissible to carry out verification of correctness using the method of spectral analysis based on reproducing the values ​​of the mass fractions of elements in the enterprise’s RM.

7.6 When meeting the requirements of this standard, the error of the analysis result (with a confidence probability of 0.95) should not exceed the limit value D (Table 1).

APPENDIX A

Conditions for analysis in photovoltaic installations

Table A.1

Table A.2

Table A.3

Key words: steel, analysis, photoelectric spectral method, sample, equipment, materials, result, error of results

Optical emission spectral analysis (OESA)

Optical emission spectral analysis (OESA) - one of the most common methods for analyzing the elemental composition of materials. The most important advantages of OESA are its speed (expressness) along with high accuracy and low detection limits, low cost, and ease of sample preparation.

The main areas of application are the analysis of the composition of metals and alloys in metallurgy and mechanical engineering, the study of geological samples and mineral raw materials in the mining industry, the analysis of water and soil in ecology, the analysis of motor oils and other technical fluids for metal impurities in order to diagnose the condition of machines and mechanisms...

The operating principle of an optical emission spectrometer is quite simple. It is based on the fact that the atoms of each element can emit light of certain wavelengths - spectral lines, and these wavelengths are different for different elements. In order for atoms to begin emitting light, they must be excited - by heat, electrical discharge, laser or some other method. The more atoms of a given element are present in the analyzed sample (sample), the brighter the radiation of the corresponding wavelength will be.

The figure shows a functional diagram of an optical emission spectrometer. It consists of the following main parts:

• a stand in which the analyzed sample is installed with a spectrum excitation source - a device that causes the sample atoms to emit light;
• a polychromator that decomposes the radiation of a sample into a spectrum and makes it possible to separate the radiation of different atoms, i.e. highlight the spectral lines of the analyzed elements;
• radiation receivers (for example, photomultiplier tubes - PMTs) with a registration system that converts light into an electrical signal, registers it and transmits it to a computer;
• a computer that calculates the concentrations of the analyzed elements and controls all components of the device.

The intensity of the spectral line of the analyzed element, in addition to the concentration of the analyzed element, depends on a large number of different factors. For this reason, it is impossible to theoretically calculate the relationship between line intensity and the concentration of the corresponding element. That is why standard samples that are similar in composition to the sample being analyzed are required for analysis. These standard samples are first exposed (burned) on the device.

Based on the results of these burns, a calibration graph is constructed for each analyzed element, i.e. dependence of the intensity of the spectral line of an element on its concentration. Subsequently, when analyzing samples, these calibration graphs are used to recalculate the measured intensities into concentrations.

Standard samples

Standard samples are samples with a known elemental composition. They are necessary for calibration of the optical emission spectrometer.

Standard samples are usually produced in sets; Each kit must be accompanied by a passport, which shows the concentrations of all elements and the errors with which these concentrations are determined.

Requirements for the standard samples used:

1. Compliance with the analyzed samples in terms of chemical composition.
2. The content of analyzed elements in the standards should cover the entire range of possible mass fractions of the element in the samples.
3. Uniform distribution of all elements in a set of standard samples.
4. Maximum correspondence to the analyzed samples in terms of structure and physicochemical properties.
5. Stability of composition and properties for a long period of time.
6. The minimum number of standards with a uniform distribution of concentrations for calibration is 4-6 samples.

Preparing samples for analysis

It is difficult to overestimate the importance of rational sample selection and proper preparation for obtaining reliable and reliable analytical results. In our experience, at least half of erroneous test results are due to errors in sampling and sample preparation.

It should be borne in mind that in reality several milligrams of a sample from its surface are analyzed. Therefore, to obtain correct results, the sample must be homogeneous in composition and structure, and the composition of the sample must be identical to the composition of the metal being analyzed.

When analyzing metal in a foundry or smelter, it is recommended to use special molds for casting samples. In this case, the sample shape, generally speaking, can be arbitrary. It is only necessary that the sample being analyzed has sufficient surface area and can be clamped in a stand.

To take a sample during incoming inspection of sampling materials, cutting machines, scissors, etc. can be used.

Special adapters can be used to analyze small samples such as rods or wires. The preparation of the surface being analyzed also plays a very important role.

When analyzing aluminum and copper alloys, it is recommended to prepare the sample surface on lathes or milling machines; in some cases a file can be used to prepare the surface. In this case, overheating of the sample surface and the cutting tool should be avoided, because overheating can change the composition and structure of the material in a layer of approximately 0.1-0.3 mm.

For steels, cast irons and other durable materials, treatment with abrasive paper (sandpaper) or a medium-sized abrasive stone, 40 or 60 according to GOST 3647-80, is used to prepare the analyzed surface. It should be borne in mind that many abrasive materials, when grinding, introduce silicon, aluminum and phosphorus into the sample surface with abrasive particles, which can affect the analysis results.

Emission spectral analysis is a complex procedure consisting of a number of different operations:

1. Selection of spectral lines of the analyzed elements and adjustment of the spectrometer to these lines;
2. Selection of optimal analysis modes for specific materials;
3. Selection of standard samples for spectrometer calibration;
4. Calibration of the spectrometer according to selected standard samples;
5. Sampling and preparing it for analysis;
6. Exposure (burning) of the sample on an emission spectrometer (usually 2 or 3 times);
7. Processing the results.

To obtain reliable analysis results, it is necessary that all of the above operations be performed correctly in compliance with all necessary requirements. It is important to understand the error of the results obtained.

The combination of all the above operations is called the Measurement Methodology.

Of course, if you are analyzing materials “for yourself,” it is enough that your laboratory assistants know how to perform all the listed operations and do it quite accurately and efficiently. However, if you want the results obtained to be convincing for your customers to whom you supply products, your suppliers or other third-party organizations, you need to develop an official document regulating the entire procedure for preparing and conducting analysis - a Measurement Methodology (MVI).

The developed MVI must be certified in the prescribed manner. The main purpose of MVI certification is to confirm the possibility of measurements using a given MVI with a measurement error not exceeding that specified in the document regulating the MVI.

The procedure for the development and certification of MVI is determined by GOST R 8.563-96 “Measurement Methods”.

Currently, there are a number of MVIs that have undergone certification and standardization and brought to the level of State standards.

The list (incomplete) of such GOSTs is given below:

GOST 5905-2004. (ISO 10387:1994) Chrome metal. Methods of atomic emission spectral analysis.

GOST 22536.0-87. Carbon steel and unalloyed cast iron. General requirements for analysis methods.

GOST 27809-95.

GOST 2787-75. Ferrous secondary metals. General technical conditions.

GOST 7565-81. Cast iron, steel and alloys. Sampling method for chemical composition.

GOST 27611-88. Cast iron. Photoelectric spectral analysis method.

GOST 27809-88. Cast iron and steel. Methods of spectrographic analysis.

GOST 15527-2004. Copper-zinc alloys (brass), processed by pressure. Methods of atomic emission spectral analysis.

GOST 24231-80. Non-ferrous metals and alloys. Methods of spectral analysis.

GOST 12223.1-76. Iridium. Spectral analysis method.

GOST 12227.1-76. Rhodium. Spectral analysis method.

GOST 6012-98. Nickel, Methods of chemical-atomic emission spectral analysis.

GOST 24018.0-90. Nickel-based heat-resistant alloys. General requirements for analysis methods.

GOST 3240.0-76. Magnesium alloys. General requirements for analysis methods.

GOST 15483.10-2004. Tin. Methods of atomic emission spectral analysis.

GOST 21996-76. Cold-rolled, heat-treated steel strip. Photoelectric spectral analysis methods.

GOST 9717.1-82. Copper. Method of spectral analysis using metal standard samples with photoelectric recording of the spectrum.

GOST 20068.3-79. Tin-free bronzes. Method of spectral analysis using oxide standard samples with photographic recording of the spectrum.

GOST 9716.2-79. Copper-zinc alloys. Method of spectral analysis using metal standard samples with photoelectric recording of the spectrum.

GOST 24231-80. Non-ferrous metals and alloys. General requirements for the selection and preparation of samples for chemical analysis.

GOST 13348-74. Lead-antimony alloys. Spectral analysis method.

GOST 17261-77. Zinc. Spectral method of analysis.

GOST 23328-78. Antifriction zinc alloys. Methods of spectral analysis.

GOST 8857-77. Lead. Spectral analysis method.

GOST 9519.0-82. Calcium babbits. General requirements for spectral analysis methods.

GOST 9519.1-77. Calcium babbits. Method of spectral analysis using cast metal standard samples.

GOST 9519.2-77. Calcium babbits. Method of spectral analysis using synthetic standard samples.

GOST 23902-79. Titanium alloys. Methods of spectral analysis.

GOST 7727-81. Aluminum alloys. Spectral analysis method.

GOST ISO 7347-94. Ferroalloys. Experimental methods for monitoring systematic errors in sampling and sample preparation

GOST R 50065-92. Ferroalloys. Experimental methods for assessing quality variation and methods for monitoring sampling accuracy.

METHOD OF PHOTOELECTRIC SPECTRAL ANALYSIS

GOST 18895-81

Official publication

USSR STATE COMMITTEE ON STANDARDS Moscow

DEVELOPED by the Ministry of Ferrous Metallurgy of the USSR CONTRACTORS

N. P. Lyakishev, V. P. Zamaraev, N. V. Buyanov, A. V. Titovets, A. V. Krinevskaya, A. I. Ustinova, E. A. Sveshnikova.

INTRODUCED by the USSR Ministry of Ferrous Metallurgy

Member of the Board A. A. Kugushin

APPROVED AND ENTERED INTO EFFECT by the Decree of the USSR Military Committee on Standards dated December 29, 1981>

GOST 18895-81 Page. 9

Continuation of the table. 2

UDC 669.14.001.4:006.354 Group B39

STATE STANDARD OF THE USSR UNION

Photoelectric spectral analysis method

Steel. Method of photoelectric spectral analysis

Instead of GOST 18895-73

By Decree of the USSR State Committee on Standards dated December 29, 1981 No. 5720, the validity period was established

from 01.01. 1983 to 01.01. 1988

Failure to comply with the standard is punishable by law

This standard establishes a photoelectric spectral method for determining elements in steel, %:

Official publication ★

Reproduction is prohibited

© Standards Publishing House, 1982

The method is based on the excitation of steel atoms by an electric discharge, decomposition of the radiation into a spectrum, measurement of analytical signals proportional to the intensity or logarithm of the intensity of spectral lines, and subsequent determination of the element content using calibration characteristics.

1. SAMPLE SELECTION AND PREPARATION

1.1. Sampling and preparation of samples - according to GOST 7565-81. The sample surface intended for searching is ground flat. Holes, slag inclusions, tarnish and other defects are not allowed on the surface; surface roughness Rz should be no more than 20 microns according to GOST 2789-73.

2. EQUIPMENT AND MATERIALS

2.1. Photoelectric vacuum and air installations with individual calibration.

Cutting machines type 8230 and 2K337.

Grinding machine model ZE881.

Sharpening and grinding machine (grinding and emery machine) type TSh 500.

Universal machine for sharpening electrodes model KP-35.

Screw-cutting lathe model 1604.

Cutting discs 400X4X32 according to GOST 21963-76.

Electrocorundum abrasive wheels with ceramic bond, grit number 50, hardness ST-2, size 300X40X70 according to GOST 2424-75.

Sanding paper type ШБ-200, grain size No. 40-50 according to GOST 6456-75.

2.2. In the case of using vacuum photovoltaic installations, permanent rod electrodes of silver, copper and tungsten with a diameter of 5-6 mm or tungsten wire with a diameter of 1-2 mm and a length of at least 50 mm are used.

For airborne photovoltaic installations, copper rods of grade M00, Ml, M2 according to GOST 858-78 and carbon rods with a diameter of 6 mm and a length of at least 50 mm are used.

2.3. To determine the mass fraction of elements in rolled steel, vacuum and air photovoltaic installations are used. If the sample does not completely cover the hole in the tripod of the vacuum photovoltaic installation, use a contact chamber (see drawing) or another device that limits the hole in the tripod table.

GOST 18895-81 Page. 3

Contact chamber for vacuum spectrometer

/-contact: 2-dinner; I-plate: 4-spacer

2.4. It is allowed to use other equipment, equipment and materials that ensure the accuracy of analysis provided for by this standard.

3. PREPARATION FOR ANALYSIS

3.1. Preparation of the installation for measurements is carried out in accordance with the description of the maintenance and operation of the installation.

3.2. The calibration of each photovoltaic installation is carried out experimentally when introducing a measurement technique using reference standards (RM) of composition, certified in accordance with GOST 8.315-78.

3.3. During the initial calibration, at least five series of measurements are performed on different days of operation of the photovoltaic installation. In a series, for each RM, two pairs of parallel (performed one after the other on the same surface) measurements are carried out.

The order of pairs of parallel measurements for all SDs in the series is randomized. The arithmetic mean value of the analytical signals for the series and the arithmetic mean value of the analytical signals for five series of measurements for each reference standard are calculated.

Calibration characteristics are established by calculation or graphically, which are expressed in the form of a formula, graph or table.

Calibration characteristics are used to determine the mass fraction of controlled elements directly or taking into account the influence of the chemical composition and physical and chemical properties of the object.

3.4. Repeated calibration is carried out in accordance with clause 3.3, while a reduction in the number of measurements is allowed.

4. ANALYSIS

4.1. The analysis conditions are given in the recommended appendix (see Tables 1, 2).

4.2. The wavelengths of the spectral lines and the range of mass fraction values ​​are given in Table. 1.

Table 1

GOST 18895-81 Page. 5

Continuation of the table. 1

Continuation of the table. 1

GOST 18895-81 Page, 7

Continuation of the table. 1

From the given lines, the optimal lines are selected for a specific analytical technique depending on their intensity, the type of photovoltaic installation, the overlap of other lines, and the possibility of placing output slits on the device carriages.

4.3. Three parallel measurements are performed for each controlled element of the analyzed sample. Two parallel measurements are allowed.

Page 8 GOST 18895-81

5. PROCESSING RESULTS

5.1. The arithmetic mean of two or three parallel determinations is taken as the final result of the analysis.

5.2. If the discrepancy between the values ​​of the analytical signal, expressed in units of mass fraction, is no more than d cx (Table 2) for three parallel measurements or 0.8 d cx for two parallel measurements, calculate the arithmetic mean of these determinations.

Table 2