GOST 7727-81

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  ГОСТ 7727-81

GOST 7727−81 aluminum-based Alloys. Methods of spectral analysis (with Amendments No. 1, 2)

GOST 7727−81

Group B59

INTERSTATE STANDARD

ALUMINUM ALLOYS

Methods of spectral analysis

Aluminium alloys. Methods of spectral analysis

AXTU 1709

Date of introduction 1982−07−01

INFORMATION DATA

1. DEVELOPED AND INTRODUCED by the Ministry of aviation industry of the USSR

2. APPROVED AND put INTO EFFECT by Decision of the USSR State Committee for standards from 15.06.81 g N 2942

3. REPLACE GOST 7727−75

4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

5. The expiration time limit is removed by the Resolution of Gosstandart from 02.04.92 N 357

6. EDITION (August 2002) with Amendments No. 1, 2 approved in December 1986, April 1992 (IUS 3−87, 7−92)


This standard specifies methods for determining the spectral content of alloying elements and impurities (copper, magnesium, manganese, iron, silicon, titanium, zinc, vanadium, lithium, cadmium, beryllium, Nickel, chromium, zirconium, cerium, sodium, lead, tin, antimony, arsenic, boron) in cast and wrought aluminum alloys.

1. GENERAL REQUIREMENTS

1.1. The content of alloying elements and impurities in alloys is determined by calibration graphs constructed by standard samples (CO). Use two methods of calibration of instruments: the method of «three standards» and method «test standard».

Registration of spectra — the photographic or photoelectric.

The analysis of the photographic method of calibration graphs constructed in the coordinates:

,

where is the difference of pochernenija lines of the designated element and an element of comparison;

 — mass fraction of the element in.

 — relative strength line of the designated item and line comparison.

The analysis of the PV method, the calibration graphs constructed in the coordinates:

; ; ,

where is the indication of the output of the measuring device.

1.2. The analysis used the State standard samples (GSO) N 484−74 — 490−74; 532−74 — 538−74; 584−74 — 588−74; 748−75 — 752−75; 958−76 — 961−76; 1062−76 — 1069−76; 1161−77 — 1165−77; 1196−77 — 1199−77; 1200−77 — 1205−77; 1206−77 — 1211−77; 1212−77 — 1217−77; 1251−77 — 1255−77; 1305−78 — 1308−78; 1620−79 — 1623−79; 1672−79 — 1676−79; 1884−80 — 1887−80; 1888−80 — 1890−80; 2201−81 — 2206−81; 2821−83 — 2825−83; 2877−84 — 2880−84; 3225−85 — 3234−85; 3430−86 — 3434−86; 3697−87 — 3703−87; 4219−88 — 4222−88; 4234−88 — 4238−88; 4344−88 — 4348−88; 4413−88 — 4419−88; 5047−89 — 5050−89; 5067−89 — 5071−89; 5276−90 — 5279−90; 5383−90 — 5389−90; industry standard sample (CCA) N 4−85 — 8−85; 8−84 — 11−84; 12−84 — 16−84; 16−81 — 20−81; 17−84 — 19−84; 21−81 — 25−81; 26−81 — 29−81; 53−82 — 57−82; 58−82 — 61−82; 66−83 — 73−83; 371−88 — 376−88; 391−89 — 394−89; 411−90 — 414−90.

It allowed the application of standard samples of the enterprise (SOP) newly-issued standard samples of aluminum alloy in all categories that meet the requirements of GOST 8.315.

(Changed edition, Rev. N 2).

1.3. Sampling is carried out according to normative-technical documentation.

1.4. Check of correctness of definition of a mass fraction of elements is carried out on control samples, comparing the results of spectral analysis with the results of the analysis performed by chemical methods according to GOST 11739.1 — GOST 11739.24 at least once a quarter.

The permissible value of the absolute differences must be calculated by the formula

,

where the result of analysis of sample made by chemical method, %;

 — the result of a sample analysis performed by the spectral method, %;

 — the standard deviation characterizing the reproducibility of spectral analysis;

 — the standard deviation characterizing the reproducibility of chemical analysis results.

(Changed edition, Rev. N 1, 2).

2. PHOTOGRAPHIC METHOD OF SPECTRAL ANALYSIS

2.1. The essence of the method

The method is based on the excitation spectrum of the alloy arc or spark discharge, with subsequent registration on the photographic plate by a spectrograph.

2.2. Apparatus, materials and reagents

Spectrograph with quartz optics, a medium dispersion type of ISP-30.

Spark generator of the type IG-3 or IVS-23 or arc type DG-2 or IVS-28.

Microphotometer type MF-2 and IPV-460.

The damping of the three — and nine -.

Coals spectral brands of high purity-7−3, C-2, C-3 in the form of bars with diameter 6 mm.

Bars aluminum brands A99, A97 according to GOST 11069, with a diameter of 3−8 mm.

Photographic plates of the spectral types 1, 2, 3, ES, UPS, SFC-01, the SFC-02, the SFC-03, PFS-04, the SFC-05 sensitivity 3 to 20 units.

The lathe table type of TV 16.

A device for grinding coal.

The developer consisting of two solutions.

Solution I:

distilled water according to GOST 6709 — 1000 cm;

metol (para-methylaminophenol) — 2 g;

sodium sanitarily 7-water on the other 6−09−1457* — 104 g or sodium sanitarily according to GOST 195 — 52 g;
________________
* Document authoring is. For additional information, please refer to the link. — Note the manufacturer’s database.

hydroquinone (paradoxians) according to GOST 19627 — 10 g;

potassium bromide according to GOST 4160 — 2 g.

Solution II:

distilled water according to GOST 6709 — 1000 cm;

sodium carbonate according to GOST 83 — 54 g.

Before the manifestation of the solutions I and II are mixed in a ratio of 3:1.

Fixer:

distilled water according to GOST 6709 — 1000 cm;

sodium thiosulfate crystal according to GOST 244 — 300 g;

ammonium chloride according to GOST 3773 — 60

Allowed the use of other devices, equipment, materials and reagents, subject to obtaining the metrological characteristics specified in this standard.

2.3. Preparation for assay

For the analysis of used samples (after sharpening): round bars or square cross-section with a diameter of from 5 to 50 mm, length 30−100 mm, profiles, disks, strips of a thickness not less than 2 mm, «fungi», with the diameter of the «cap» of 30−50 mm, thickness not less than 5 mm.

Allowed to use samples of smaller size in the presence of SOPS of appropriate dimensions.

Ubeskrivelig the surface of the samples are adjusted to a plane by machining. The parameter of surface roughness should be not more than 20 µm according to GOST 2789. With samples in the form of «fungus», obtained by pouring metal in the mold, is removed from the bottom side (with cap) layer 1.5−2 mm; rod shaped samples with a diameter of 5−10 mm obtained by pouring metal in the mold, remove 5−10 mm. If the cast rod has a flat end face, allowed the removal of metal from the yard to a depth of 0.2−0.5 mm.

The preparation of analyzed samples (AO) and to the analysis should be similar for this series of measurements. On the treated surface are not allowed voids, scratches, cracks, and slag inclusions.

Protivoelektrodom sharpen on a sphere of radius 3−6 mm, cone angle 120° or truncated cone with ground diameter of 1−2 mm with a sharpening angle of 40−60°.

2.4. Analysis

The conditions of analysis of the photographic method of the type spectrograph ISP-30 are given in table.1.

Table 1

Notes:

1. The exposure time is set depending on the sensitivity of photographic plates; it must be at least 15

2. In determining cerium in order to obtain one spectrogram using two exposures with the stripped parts of the sample (30 from each).

3. Carrying out analysis with the use of pairs of electrodes with sharpening one of the electrodes on the plane.

4. In the analysis sheets and bars with dimensions smaller than provided in this standard allowed a range of modes of operation of the light sources and application of SOPS relevant AO.


Wavelength of analytical spectral lines and ranges of detectable concentrations are given in table.2.

Table 2

________________
* The line of beryllium 313,04 nm used for the analysis of alloys not containing vanadium.
** Line of boron 249,77 nm used for the analysis of alloys not containing iron.
*** The line of silicon 251,61 nm used for the analysis of alloys containing no titanium.

Notes:

1. The spectral lines of elements, limited in the table paranteza can be in accordance with specified ranges of mass fraction are combined in an analytical pair of lines of comparison depending on the selected conditions of analysis.

2. The Roman numeral I to the values of wavelengths is from a line to a neutral atom, figure II — once ionized atom.

3. If the comparison lines using the background, the latter is measured near the line of the element.


The analysis by the method of «three standards» choose FROM the analyzed alloy in an amount of not less than three, the spectra of co and AO are photographed on the same photographic plate at the selected conditions of analysis with randomization of the order of shooting. For each co and AO photographed three of the spectrum.

Measure the blackening of the selected analytical lines and lines of comparison, the count value difference of the blackening for the analytical line pairs, and the arithmetic average of the three spectra.

Build a calibration curve in the coordinates: .

This schedule is suitable for the analysis of those samples, the spectra of which are filmed along with on a single photographic plate.

The contents of the element in AO find for the calibration schedule.

The exposure time is selected such in which, provided the normal blackening of analytical lines.

In the analysis of small mass fraction of allowed characteristic curve, carefully constructed in neoteric. The calibration graph constructed in this case in the coordinates:

,

where is the intensity of the line of the designated element;

 — the intensity of the comparison lines or background area of the element.

The analysis by the method of «controlling standard» in addition to the standard samples that are used to build the basic calibration curve using a standard sample of enterprises, which must satisfy the following requirements:

the chemical composition should be as close as possible to the middle of the range mass fraction specified in the normative-technical documentation on the alloy, or to the average chemical composition of the JSC;

on the physical properties, shape and size of SOP should be possible to approach the AO.

The work begins with the construction of the basic calibration curve. On one photographic plate spectra photographed WITH this alloy, together with the spectra of the DIS. Spectra each WITH and SOP photographed five times. The average difference values of pucherani build the calibration schedule of the main photographic plates in the coordinates: .

In the analysis of samples of aluminum alloys at the operating plate photographed spectra of AO three times each and the spectra SOP four times. Determine the difference pucherani analytical line pairs for SOP and AO (and ) as the average of the corresponding number of spectra. The value is multiplied by the magnitude of conversion factor . The conversion factor is introduced to account for the properties of the emulsion working plates, calculated by the formula

,

where is the difference of pochernenija auxiliary line pair aluminum or difference pucherani line of aluminium for the two steps of the attenuator, calculated for several spectra WITH and SOPS for the main photographic plates (assuming that between and no systematic differences);

 — the difference between pochernenija the same lines of aluminium and the same steps of the attenuator, calculated for a working photographic plates SOP and AO.

To calculate use a couple of lines of aluminium 265,24 nm — nm 256,79 and of 305.00 nm — nm 305,71 etc.

Through the point with coordinates ; (where  — mass fraction of the element in the SOP) conduct work schedule, parallel to the main, and determine mass fraction in JSC using the value .

Allowed to operate by using a constant calibration curve, built according WITH, the spectra of which are photographed on the main plate in the coordinates .

On the plate photographed spectra AO and SOPS.

Mass fraction of the element in AO is determined by a constant calibration graphics using the value .

To simplify the calculations calibration curve can be artificially reduced to 45°. In this case, instead of the coefficient factor should be used

,

where  — the angle of the calibration chart for the main plates, constructed in the coordinates , or , a calibration curve performed under an angle of 45° from the point of intersection of the initial graph (straight line) with the abscissa axis.

2.2−2.4. (Changed edition, Rev. N 1, 2).

2.5. Processing of the results

2.5.1. The final result of the analysis be the arithmetic mean of three parallel measurements obtained on the three spectrograms, provided

;

where is the greatest result of the parallel measurements;

least the result of the parallel measurements;

 — the relative standard deviation characterizing the precision of measurements;

 — the arithmetic mean calculated from parallel measurements (=3).

When you conduct proximate analysis and the determination of mass fraction of elements less than 1% is allowed, the resulting analysis to calculate the two parallel measurements and provided that .

(Changed edition, Rev. N 1, 2).

2.5.2. If the difference between the results of the analysis and one of the limit values of element content for this alloy is in absolute value less than or equal to

,

where is the number of samples (=1 or 2);

 — the relative standard deviation characterizing the reproducibility of the analysis;

 — the average result of the analysis of one or two definitions.

The analysis is carried out by chemical methods according to the standards specified in claim 1.4.

(Changed edition, Rev. N 1).

2.5.3. Values and for photographic analysis method are given in table.3.

(Changed edition, Rev. N 1, 2).

Table 3

2.5.4. Methods of calculation and are given in the Appendix.

3. THE METHOD OF PHOTOELECTRIC SPECTRAL ANALYSIS

3.1. The method is based on the excitation spectrum of the arc or spark discharge with the registration of the intensity of spectral lines with the help of photovoltaic installation.

3.2. Equipment and materials

Photovoltaic plant (quantometer) types of DFS-10M, DFS-36, MFS-4, MFS-6, MFS-8.

Generator types, IG-3, Economics-1, UGE-4, IVS-1, IVS-28, Arcus.

Spectral clean coal brands high purity-7−3, C2, C3 in the form of bars with diameter 6 mm.

Bars of aluminium brands A99, A97 according to GOST 11069, with a diameter of 6−8 mm.

The lathe type of TV 16.

A device for grinding coal.

Allowed to use other equipment, equipment and materials subject to receipt of the metrological characteristics specified in this standard.

(Changed edition, Rev. N 1).

3.3. Sample preparation

The samples prepared in accordance with paragraph 2.3.

3.4. Analysis

The analysis is carried out according to the methods of «three standards» or «control standard».

The conditions of analysis are given in table 4.

Table 4

________________
* The width of exit slit is selected depending on the mass fraction of an element and the degree of doping of the alloy.


Wavelength of analytical spectral lines and ranges of detectable concentrations are given in table.5

Table 5

Note. As lines of comparison use lines of aluminium: I 396,15; I 394,40; I 360,17; I 305,01; I 266,04; I 256,80 or undecomposed light.


The analytical lines chosen depending on the mass fraction of the element in the sample and output slots on the carriages quantometer. The use of other analytical lines, provided that they provide the metrological characteristics specified in the present standard.

The contents of the element in AO in the analysis by the method of «three standards» are determined using a calibration curve built in.

For devices in which the indication of the measuring device is proportional to the logarithm of the intensity of the spectral lines of the calibration graphs constructed in the coordinates: .

The spectra of each of co and AO are registering at least three times.

The analysis by the method of «reference standard» for devices type I: build the primary calibration curve in the coordinates: . In the analysis of AO spectra recorded SOP and AO. Through the point with coordinates ; conduct work schedule parallel to the main and for determining the mass fraction of the element AO.

The analysis by the method of «reference standard» for devices type II: record the spectra, averaged samples to build a calibration curve in the coordinates: and continue to the intersection with the axis of concentrations. The point of intersection will be the «pivot point» calibration curve, assuming the constancy of the «zero» reading device on the corresponding channel and straightness calibration curve.

Before analysis the samples of the recorded spectra SOP, through the point with coordinates: ; and «point of rotation» is carried out working calibration curve, which determine the mass fraction of the element in AO.

If the calibration curve constructed in the coordinates: , work schedule is carried out parallel to the main, through the point with coordinates: ; and for determining the mass fraction of the element in AO.

(Changed edition, Rev. N 1, 2).

3.5. Processing of the results

3.5.1. Processing of the results of the analysis carried out in accordance with PP.2.5.1; 2.5.2.

3.5.2. Values and for photographic analysis method are given in table.3.

(Changed edition, Rev. N 1).

APP (mandatory). TO EVALUATE THE ACCURACY OF SPECTRAL ANALYSIS

APP
Mandatory

1. The accuracy of spectral analysis — the quality of measurements that reflects the closeness of their results to the true value of the measurand is determined by the magnitude of systematic and random errors provided that the failures are excluded from the calculations (random errors obey the normal distribution law).

2. When properly configured, the spectral instrument and the implementation of the recommendations of the standard procedure of analysis the main sources of systematic errors are errors associated with the influence of structure and chemical composition of samples on the results of the analysis.

These errors should be identified by comparison of the results of the analysis of samples, performed chemical and spectral methods on a large sample (minimum 20 samples).

If the presence of such errors is selected, they eliminate the adjustment of the position calibration curve SOP.

3. The result of the analysis of the sample obtained as the arithmetic mean, for example, of the three (two) of parallel measurements, i.e., three (two) spectra should be regarded as one definition.

4. Reproducibility of spectral analysis — the quality of measurements that reflects the closeness to each other of the results of measurements made under different conditions, characterized by the value of the relative standard deviation of a single determination .

5. For calculation choose at least five samples of one brand of alloy having approximately the same chemical composition, and within 5 days conduct their analysis series (one series per day).

Spectra in each series is produced in a different sequence, i.e. randomization.

One series of spectra recorded on the same photographic plate.

On each photographic plate to receive three of the spectrum of each sample and three FROM each spectrum. The latter is necessary for the construction or adjustment of the calibration graphs.

By the photoelectric registration before making a measurement, adjust the position of the calibration graphs, and then spectra of the samples.

Just from each sample get for 5 days for 15 measurements (five definitions).

For each sample calculate the standard deviation by the formula

, (1)

where is the average mass fraction of the element in the -th sample is calculated from five determinations;

 — mass fraction of the element at the -th definition in the -th sample computed from the three measurements

the number of samples (=5).

Calculate the standard deviation by the formula

, (2)

where , ,…  — standard deviation, calculated respectively for first, second, etc. samples according to the formula (1);

 — the number of samples (=5).

The relative standard deviation characterizing the reproducibility of the analysis calculated by the formula

, (3)

where is the average mass fraction of element in the samples, calculated according to the formula

, (4)

where , ,…  — mass fraction of the element respectively in the first, second, etc. samples, calculated from 5 determinations.

Control the reproducibility of the recommended once in 3−6 months. The resulting values should not exceed the values given in table.3.

(Changed edition, Rev. N 1).

6. Repeatability of measurements the quality of measurements that reflects the closeness to each other of the results of measurements made under the same conditions, is characterized by a relative standard deviation of a single measurement .

7. The value of the find in series of 20 parallel measurements for one sample with correctly configured equipment.

The standard deviation is calculated by the formula

, (5)

where is the average mass fraction of the element in the sample is calculated from 20 parallel measurements;

 — mass fraction of element in the sample computed from the -th measurement;

 — the number of measurements in series (=20).

The relative standard deviation characterizing the repeatability of measurements, calculated by the formula

. (6)

8. In the analysis it is often necessary to estimate the error of the result of the analysis and confidence limits. At p = 0.95 and excluded systematic error is calculated by the formula

, (7)

where is the number of definitions by which the computed result of the analysis of the sample (usually in the spectral analysis =1 or 2);

the result of analysis of the sample, calculated according to the definitions.

Computed value means that with a reliability of 95% the true value of the designated value lies in interval

and ,

the most likely result is .

If the confidence interval overlaps defined (GOST 1583 and GOST 4784), the analysis recommended a different, more accurate method.

9. The offset of the calibration curve relative to the base (drift level SOP) is considered significant if it exceeds the standard deviation of the four measurements, i.e. when the necessary adjustments to the schedule,

where is the number of parallel measurements for SOP, which is controlled by the position of the chart (=4);

 — mass fraction of the element in the SOP.

The position of the calibration chart, it is recommended to monitor SOP 1−2, 1−3 times per shift.

10. A comprehensive assessment of the operation of the generator excitation spectrum, the spectral device and electronic measuring devices are recommended periodically by determining the relative standard deviation for a series of 20 parallel measurements by the formulas (5) and (6).

The value found is compared , i.e. the standard deviation, which was calculated previously, when you configured the instrument.

The comparison is performed according to a criterion. If more than the table value , it indicates that the instrument requires tuning.

At confidence probability 0.95 and the number of measurements in series (=20) =2,1.

This inspection is recommended once in 1−3 months.

(Changed edition, Rev. N 1, 2).