GOST 13938.13-93

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  ГОСТ 13938.13-93

GOST 13938.13−93 Copper. Methods for determination of oxygen

GOST 13938.13−93
Group B59

INTERSTATE STANDARD

COPPER

Methods for determination of oxygen

Copper. Methods of determination of oxygen

AXTU 1709

Date of introduction 1995−01−01

Preface

1 was DEVELOPED by Gosstandart of Russia

SUBMITTED by the Technical Secretariat of the Interstate Council for standardization, Metrology and certification

2 ADOPTED by the Interstate Council for standardization, Metrology and certification 21 October 1993

The adoption voted:

3 Decree of the Russian Federation Committee on standardization, Metrology and certification from 02.06.94 N 160 inter-state standard GOST 13938.13−93 introduced directly as state standard of the Russian Federation from 01.01.95.

4 REPLACE GOST 13938.13−77

INFORMATION DATA

REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

This standard establishes the procedure for determination of oxygen in copper recovery methods melting (electrolytic, molten or deformed when the mass fraction of oxygen from the 0.0003 to 0.5%) and metallographic (in-molded or deformed when the mass fraction of oxygen from 0.01% to 0.15%).

1. GENERAL REQUIREMENTS

1.1. General requirements for methods of analysis GOST 25086 with additions.

1.1.1. Determination of the mass of analyzed samples should be conducted on the scales with the measurement error not more than 0.0005 g.

1.1.2. The accuracy of the analysis is controlled by analysis of standard samples of composition of copper GOST 8.315*. When excluded systematic error is allowed to monitor the accuracy of analysis results by way of varying the sample.
________________
* On the territory of the Russian Federation GOST 8.315−97. Here and further. — Note the manufacturer’s database.

1.1.3. Control the accuracy of the results of the analysis should be conducted at least 1 time per month, as well as the replacement of reagents and materials.

2. THE METHOD OF REDUCTIVE MELTING

The method is based on measuring the amount of carbon monoxide resulting from the interaction of the carbon of the crucible with the oxygen of the molten sample.

The method of reductive melting has two options: restorative melting in vacuum (vacuum extraction method) and reduced melting in a current of neutral gas — the carrier gas.

2.1. Norms of accuracy of measurements

2.1.1. As standards for precision measurement with confidence probability of 0.95 is used:

the ratio of convergence  — the maximum permissible difference between results of two parallel determinations;

a standard repeatability  — the maximum permissible difference between results of the primary and secondary testing.

2.1.2. Equations for calculation of permissible differences given in table.1, where is the arithmetic mean of two parallel definitions, and  — the average of the two results of the analysis of the same sample.

Table 1

2.1.3. The standards of accuracy linked to relevant indicators of convergence and reproducibility ratios

(1)

, (2)

where is the relative standard deviation of precision definitions;

 — the relative standard deviation of reproducibility of the analysis results.

2.1.4. The error of the result of the analysis with the excluded systematic error is calculated by the formula

. (3)

2.1.5. The numerical value of the result of the analysis must end with the digit in the discharge, which begins with the value of error.

2.2. Apparatus, materials and reagents

2.2.1. The devices based on the method of reductive melting in a vacuum:

-911М1, 1403М1 design Giredmet and similar.

Express oxygen analyzers based on the method of reductive melting under a stream of neutral carrier gas: AK-7516 design NGO Chermetavtomatika, V-16, V-116; RO-316, LECO, USA and similar.

Instrument subject to metrological certification according to GOST 8.326*.
______________
* On the territory of the Russian Federation are PR 50.2.009−94**.
** PR 50.2.009−94 abrogated on the basis of the order of the Ministry of industry and trade of 30.11.2009 N 1081. — Note the manufacturer’s database.

2.2.2. For preparing samples for analysis and carrying out analysis used the following materials and reagents:

nitric acid according to GOST 4461;

acetic acid according to GOST 61;

orthophosphoric acid according to GOST 6552;

the technical rectified ethyl alcohol according to GOST 18300;

distilled water according to GOST 6709;

bars of Nickel GOST 13083;

standard samples for composition of copper GOST 8.315;

files GOST 1465;

the hand grip according to GOST 4045;

thermometer laboratory according to GOST 13646;

the stopwatch according to GOST 8.286 or GOST 8.423;

tweezers according to GOST 21241;

laboratory scales according to GOST 24104*.
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* On the territory of the Russian Federation GOST 24104−2001. — Note the manufacturer’s database.

Notes:

1. The list does not include reagents and materials used in the operation specific types of instruments specified in the relevant instructions.

2. Allowed to use different equipment, reagents and materials for the precision of the measurements is below the specified in this standard.

2.3. Preparation for assay

2.3.1 Preparation of samples

2.3.1.1. Sampling is carried out according to normative-technical documentation for specific products. Samples for analysis can be in the form of compact pieces of wire, ribbon, foil and shavings (powder). Compact sample should not have cracks, burrs, pits.

2.3.1.2. The mass of samples depending on the mass fraction of oxygen is shown in table.2.

Table 2

Note. For models of analyzers of oxygen in the carrier gas with the small capacity of the crucible is allowed to decrease the upper limit of sample mass by 2−3 times.

2.3.1.3. Compact samples clamped in a Vice and cleaned with a file, fine cut, remove burrs, degreased with alcohol and dried on a clean surface.

2.3.1.4. Samples with a mass fraction of oxygen less than 0,003%, as well as samples of complex configuration, for which complicated machining of the surface, or thickness (diameter) of less than 3 mm regardless of the mass fraction of oxygen in them, is further subjected to etching in a freshly prepared Etchant solution consisting of 62.5 ppm acetic acid, about 27.5 ppm of phosphoric acid and 10.0 ppm of nitric acid. Etching conditions: freshly prepared solution was heated to 60 °C, is immersed in the sample and etched for 60 s. Then the sample was washed with distilled water and alcohol. Allowed to poison the samples of the same batch of metal simultaneously in the same volume of Etchant. After etching, the specimen should have a bright shiny surface without spots.

2.3.1.5. Prepared for analyzing samples stored in air not more than 2 hours.

2.3.2. For the arbitration analysis and the determination of oxygen in copper containing impurities with a high affinity to oxygen by the method of reductive melting in a vacuum, must be used in the Nickel bath, that is pre-degassed Nickel alloy.

2.3.2.1. For the preparation of the bath material Nickel cut into pieces of 1.5−2 g; washed in alcohol and dried.

2.3.3. Training equipment

2.3.3.1. The instrument is ready to work according to production instructions.

2.3.3.2. The Nickel bath is prepared after degassing of the crucible. At a temperature of 1700 °C crucible load of 3.5−4.0 g of Nickel and after 5−7 minutes of degassing of the melt reduce the temperature to 1650 °C.

2.3.3.3. Indicator of the readiness of the instrument for analysis of oxygen in copper in the range of mass fraction regulated by this standard, is the average value of the steady-state the amendments the reference experiment and its convergence.

Note. The minimum detectable amount of oxygen in micrograms (absolute limit of detection) depending on the average value of amendments reference experiment is calculated using the formula

. (4)

2.3.3.4. For instrument recovery method of melting in a vacuum medium the correction control of the experience, measured in a 3 min extraction, in terms of oxygen should not exceed: 1.5 µg at a temperature of 1350 °C; 3,0 µg at a temperature of 1650 °C; the maximum difference between the measured successively amended, shall not exceed 1.0 µg of oxygen.

2.3.3.5. Preparation for instrument analysis method of reductive melting in a carrier gas includes:

complete at least two control experiments with different crucible and calculating the arithmetic mean of the values obtained with the amendments the reference experiment and maximum difference between them. The instrument is ready for analysis, if these figures do not exceed, respectively, 3 and 2 µg of oxygen;

the calibration (control of previously conducted calibration) of the measuring cell of the analyzer for calibration gas by means of a metering device or by standard samples of the composition with a certified mass fraction of oxygen in the same order as in the subject analysis of copper.

2.4. Analysis

2.4.1. Sample through a gateway is introduced into the furnace space, and then into the crucible where it is melted and oxygen interaction of the melt with carbon. The extracted gas is transported to the measuring part of the installation. Depending on the type of apparatus used are transported using a vacuum pump or carrier gas stream.

Note. When determining the mass fraction of oxygen in the samples containing more than 0.002% of the analyzers on the method of restoration of the fusion of the carrier gas is allowed to download the samples directly into the crucible after degassing bypassing the gateway.

2.4.2. The analyzer based on the method of reductive melting in a vacuum, the analysis no bath held at a temperature of 1300−1350 °C. When working with Nickel bath, the temperature of the extraction 1600−1650 °C. Mass fraction of Nickel in the melt as dilution with copper should not fall below 50%; you must keep a record of entering the molten mass of copper, and periodically fill it with pieces of Nickel. The duration of extraction in both temperature regimes is 3−5 minutes depending on the mass fraction of oxygen in copper.

2.4.3. The analyzer based on the method of reductive melting in a carrier gas, flow rate of carrier gas, the mode of the analysis (temperature and duration of degassing and extraction of oxygen) is determined by the type of device and the manufacturer’s recommendations and mass fraction of oxygen in the samples and is 20−30 C. High extraction rate is due to the rapid heating of the crucible-capsules up to 2500−2600 °C.

The completeness of extraction is controlled by repeated determination of oxygen in the analysed sample. The result of re-definition should not exceed the permissible correction control experience. The blank experiment is performed through 5−6 definitions.

2.5. Processing of the results

2.5.1. When using instruments equipped with microprocessors or electronic devices, the results of determinations are issued automatically. On other devices they are calculated according to the method of the manufacturer.

2.5.2. The analysis result should be the arithmetic mean of two parallel definitions , if the absolute value of the difference between them does not exceed the permissible values , calculated according to the table.1.

2.5.3. The absolute value of the difference between the results of the analysis of the same sample must not exceed the allowable divergence , calculated according to the table.1.

2.5.4. Control of accuracy of analysis results is carried out in accordance with clause 1.1.2.

The result of the analysis of a standard sample meets the specified accuracy, if the difference between the certified mass fractions of oxygen and reproduced, is defined as the arithmetic mean of two parallel definitions, regulatory convergence does not exceed the normative values of 0.71 reproducibility. The norms are calculated according to table.1.

Control of accuracy of analysis results by way of a variation of a sample is carried out simultaneously with the analysis of the party brass. With this aim, choose one of the samples as a control and perform two additional definitions of oxygen in the samples control sample whose mass differs from the installed tab.2 is not less than 2 times.

The result of the analysis of the control sample meets the specified accuracy, if the difference between two analysis results , and check samples obtained from different batches does not exceed the value calculated by the formula

, (5)

where  — an indicator of convergence.

3. METALLOGRAPHIC METHOD (for the interval from 0.01 to 0.15%)

The method is based on a comparison under a microscope of thin sections made from samples molded or deformed copper, with the reference photomicrographs.

3.1. Sampling

3.1.1. For metallographic analysis from the ingot taken two samples in the size not less 10х10х20 mm cut in the longitudinal and transverse directions.

The working area of the cone must be at least 10x10 mm and removed from the mold and peel from the Gating part of the ingot not less than 20 mm.

3.1.2. In the analysis of the deformed copper and articles allowed a smaller working area of the cone, but not less than 20 mm.

Note. Determination of the mass fraction of oxygen in the products of a thickness less than 2 mm is not possible.

3.2. Preparation of thin sections

The working surface of the sections treated mechanically polished to obtain a mirror surface and degreased with alcohol. The working surface of the cone should not have debris and scratches noticeable at magnification 200.

3.3. Analysis

Every thin section examined under a microscope at 200 magnificationin diffused light in the longitudinal and transverse directions. On the cone randomly select at least 5 fields, each of which determine the mass percent of oxygen by comparison with standard photographs (Fig.1−12). The identification of inclusions of cuprous oxide is carried out in polarized light, in which they acquire a ruby-red colour. Mass fraction of oxygen corresponding to this cone, defined as the arithmetic average of the mass fraction for the selected fields of view. Perform the same with the second socket.

3.4. Processing of the results

The analysis result should be the arithmetic mean of the results obtained when viewing two sections, if the difference between them does not exceed the admissible normative values , calculated at confidence probability 0,95 according to the formula

. (6)

If the differences exceed the allowable values, a second analysis on the newly selected samples.

Damn.1. Standard N 1. Material — deformed copper, the mass fraction of oxygen is 0.01%, lighting — diffused light

Standard N 1

Damn.1. Material — deformed copper, the mass fraction of oxygen is 0.01%, lighting — diffused light

Damn.2. The Standard N 2. Material — deformed copper, the mass fraction of oxygen, 0,03%, lighting — diffused light

The Standard N 2

Damn.2. Material — deformed copper, the mass fraction of oxygen, 0,03%, lighting — diffused light

Damn.3. The Standard N 3. Material — deformed copper, the mass fraction of oxygen of 0.06%, lighting — diffused light

The Standard N 3

Damn.3. Material — deformed copper, the mass fraction of oxygen of 0.06%, lighting — diffused light

Damn.4. Standard N 4. Material — deformed copper, the mass ratio of oxygen — 0.09 percent, lighting — diffused light

Standard N 4

Damn.4. Material — deformed copper, the mass ratio of oxygen — 0.09 percent, lighting — diffused light

Damn.5. Standard No. 5. Material — deformed copper, the mass fraction of oxygen and 0.12%, lighting — diffused light

The Standard N 5

Damn.5. Material — deformed copper, the mass fraction of oxygen and 0.12%, lighting — diffused light

Damn.6. Standard No. 6. Material cast copper, the mass fraction of oxygen is 0.01%, lighting — diffused light

The Benchmark N 6

Damn.6. Material cast copper, the mass fraction of oxygen is 0.01%, lighting — diffused light

Damn.7. Standard No. 7. Material cast copper, the mass fraction of the oxygen — 0,015%, lighting — diffused light

Etalon N 7

Damn.7. Material cast copper, the mass fraction of the oxygen — 0,015%, lighting — diffused light

Damn.8. Benchmark # 8. Material cast copper, the mass fraction of oxygen is 0.022%, lighting — diffused light

The Standard N 8

Damn.8. Material cast copper, the mass fraction of oxygen is 0.022%, lighting — diffused light

Damn.9. Standard No. 9. Material cast copper, the mass fraction of oxygen, of 0.035%, lighting — diffused light

Etalon N 9

Damn.9. Material cast copper, the mass fraction of oxygen, of 0.035%, lighting — diffused light

Damn.10. The Standard N Is 10. Material cast copper, the mass fraction of oxygen of 0.06%, lighting — diffused light

Etalon N 10

Damn.10. Material cast copper, the mass fraction of oxygen of 0.06%, lighting — diffused light

Damn.11. Etalon N 11. Material cast copper, the mass ratio of oxygen — 0.09 percent, lighting — diffused light

Etalon N 11

Damn.11. Material cast copper, the mass ratio of oxygen — 0.09 percent, lighting — diffused light

Damn.12. The Standard N 12. Material cast copper, the mass fraction of oxygen is 0.15%, lighting — diffused light

The Standard N 12

Damn.12. Material cast copper, the mass fraction of oxygen is 0.15%, lighting — diffused light