GOST R ISO 9686-2009

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  ГОСТ Р ИСО 9686-2009

GOST R ISO 9686−2009 Iron by direct reduction. The determination of carbon and/or sulfur. The method of infrared spectroscopy after combustion of the sample in an induction furnace

GOST R ISO 9686−2009

Group B39

NATIONAL STANDARD OF THE RUSSIAN FEDERATION

IRON BY DIRECT REDUCTION

The determination of carbon and/or sulfur. The method of infrared spectroscopy after combustion of the sample in an induction furnace

Direct reduced iron. Determination of carbon and/or sulfur content. Method of infrared spectroscopy after sample burning in induction furnace

OKS 77.080.01
AXTU 0709

Date of introduction 2010−08−01

Preface

The objectives and principles of standardization in the Russian Federation established by the Federal law of 27 December 2002 N 184-FZ «On technical regulation», and rules for the application of national standards of the Russian Federation — GOST R 1.0−2004 «Standardization in the Russian Federation. The main provisions"

Data on standard

1 PREPARED AND SUBMITTED by the Technical Committee for standardization TC 145 «monitoring Methods of steel products» based on the Russian version of the standard specified in paragraph 3

2 APPROVED AND put INTO EFFECT by the Federal Agency for technical regulation and Metrology of December 15, 2009 N 886-St

3 this standard is identical with ISO 9686:2006, «Iron by direct reduction. The determination of carbon and/or sulfur. High-frequency combustion method and measurement of infrared radiation» (ISO 9686:2006 «Direct reduced iron — Determination of carbon and/or sulfur High-frequency combustion method with infrared measurement»).

The name of this standard changed with respect to names specified international standard for compliance with GOST R 1.5−2004 (subsection 3.5).

In applying this standard it is recommended to use instead of the referenced international standards corresponding national standards of the Russian Federation, details of which are given in Appendix F

4 INTRODUCED FOR THE FIRST TIME


Information about the changes to this standard is published in the annually issued reference index «National standards», and the text changes and amendments — in monthly indexes published information «National standards». In case of revision (replacement) or cancellation of this standard a notification will be published in a monthly information index «National standards». Relevant information, notification and lyrics are also posted in the information system of General use — on the official website of the Federal Agency for technical regulation and Metrology on the Internet

1 Scope

This standard is used for determination of carbon and/or sulfur in direct reduced iron by infrared spectroscopy after combustion of the sample in the high frequency (HF) induction furnace.

The method is applicable for determining the mass fraction of carbon in the range from 0.05% to 2.5% and/or the mass fraction of sulfur in the range from 0.001% to 0.055% in iron direct reduction.

2 Normative references

This standard uses the regulatory references to the following international standards:

ISO 1042:1998 laboratory Glassware glass. Volumetric flask with one mark

ISO 7550:1985 laboratory Glassware glass. Micropipettes are disposable

ISO 7764:2006 iron Ores. Preparation of pre-dried samples for chemical analysis

ISO 10835:2007 direct reduced Iron and hot briquetting. Selection and preparation of samples

3 the essence of the method

The sample is burned in a refractory crucible in an oxygen flow in the presence of flux; the crucible is introduced into the tube for flaring of the HF furnace, the carbon is converted to carbon dioxide and sulfur to sulfur dioxide.

Each gas is determined by measuring absorption in the infrared region of the spectrum with the use of barium carbonate and potassium sulphate for building calibration dependence.

4 Reagents

Unless otherwise specified, use reagents of the established analytical purity, distilled water, further purified by distillation or other means.

4.1 Oxygen purity not less than 99.5 mass%.

The furnace pressure should be regulated using a reducer specially designed for this purpose. During operation of the reducer should be guided by the manufacturer’s instructions.

4.2 Rate of magnesium (anhydrous) grain sizes from 0.7 to 1.2 mm.

4.3 Tungsten flux (in granules) with known low mass fraction of carbon of 0.002% and the sulphur of 0.0005%.

4.4 Pure iron or iron with known low mass fractions of carbon and sulfur, as in 4.3.

4.5 Tin capsules with a capacity of 0.3 cm, with a diameter of 5 mm and a length of 17 mm.

4.6 barium Carbonate (VASO), finely ground powder.

The powder was dried at 105 °C for 3 h and cooled in a desiccator.

4.7 Standard solutions of potassium sulfate

Potassium sulfate (KSO) dried at 105 °C and cooled in a desiccator.

Potassium sulfate is weighed with accuracy of 0.0002 g in accordance with table 1.


Table 1 — the Standard solutions of potassium sulfate

Sample transferred to five volumetric flasks with one mark capacity of 100 cm, is dissolved in 50 cmof water, dilute to the mark and mix.

4.8 Ascarid use only in the determination of carbon.

5 Equipment

The usual laboratory glassware, including pipettes and volumetric flasks with one mark according to ISO 7550 and ISO 1042, respectively, as well as the following equipment.

5.1 Analyzer to determine carbon and sulfur

The analyzer is suitable for high-frequency (HF) burning samples and measuring the absorption in the infrared region of the spectrum of the formed oxides of carbon and/or sulfur. You can use analyzer of different manufacturers. Characteristics of the analyzer — see Annex C.

When operating the analyzer should follow the manufacturer’s instructions.

5.2 Ceramic crucibles for burning, and additional devices that may be required for incineration of the sample.

The crucibles must be of a certain size that is appropriate for the system, and conform to the stand so that the sample in the crucible was located at the optimum height within the inductor when it is in raised position.

The crucible pre-calcined in flowing oxygen in the furnace for at least 2 hours at a temperature of 1350 °C (or at temperature of 1000 °C, in the determination of sulfur only) and then stored in a desiccator.

For pre-calcination, it is possible to use a resistance furnace.

5.3 Pipette with a capacity of 50 µl.

6 Sampling

6.1 Laboratory test

For analysis using laboratory test particle size of 160 µm, which are selected and prepared according to ISO 10835.

6.2 Preparing pre-dried samples

Carefully mix the laboratory sample using a jig made of non-magnetic materials. Taken using a non-magnetic spatula a few single samples, so that they were representative for the whole laboratory sample.

Dried sample at a temperature of (105±2) °C according to ISO 7764.

7 control Method

Warning — Danger associated with the procedure of the analysis relates mainly burns of hands during pre-calcination of the ceramic crucibles and the subsequent combustion of the sample. Observe the usual safety precautions when working with oxygen cylinders. The oxygen released during combustion should effectively be removed from the device and space, since too high a concentration of oxygen in a confined space may cause fire. To prevent high-frequency radiation it is necessary to apply shielding.

7.1 General instructions

Oxygen clean using tubes filled with Astarita (4.8) and the rate of magnesium (4.2), oxygen consumption in idle mode support of about 0.5 DM/min.

Between the furnace chamber and the analyzer, set the filter of glass wool, which are changed as needed. The furnace chamber, the base and the absorber of the filter must be cleaned as often as possible to remove the deposits of oxides.

Oxygen consumption may vary depending on the type of analyzer and depends on the composition of the samples, but usually at the time of burning it is equal to 2.0 DM/min of the combustion temperature depends on the power of the RF generator, the geometry of the furnace, the inductor, as well as the composition and amount of sample in the crucible. The temperature may be 1700 °C or more.

When the power supply is kept for a certain interval of time recommended by the manufacturer of equipment for the stabilization of each piece of equipment.

After cleaning the oven chamber, filter replacement or interruption in the operation of the device for stabilizing operation of the equipment burned several samples, whose composition is similar to the analyzed one.

Pass oxygen through the apparatus and establish monitoring and measuring devices to zero.

7.2 Analytical sample

Weigh 0.4 g of the laboratory sample with a precision of 0.0001 g.

7.3 Blank

Hold blank in the same manner and with the same amounts of all reagents, which are used for the analysis of (7.5):

— 1.9 g tungsten flux (4.3);

— 1.3 g of pure iron (4.4);

— 1 tin capsule (4.5).

To achieve the greatest accuracy shall be conducted at least three blank experiments.

Use the average of the results of the blank experience for zero adjustment of the device in accordance with the requirements of the manufacturer.

7.4 Construction of calibration curve

7.4.1 preparation of the crucible

7.4.1.1 preparation for the construction of calibration curve for the determination of carbon

Weigh the sample barium carbonate (4.6), with accuracy to 0.0002 g in accordance with table 2 and put them in six ceramic crucibles (5.2) as shown in Appendix A.


Table 2 — Calibration a series of batches of barium carbonate for the determination of carbon

7.4.1.2 preparation for the construction of calibration curve for the determination of sulfur

Using a pipette (5.3) administered 50 ál of a standard solution of potassium sulfate (4.7) seven tin capsules in accordance with table 3.


Table 3 — Calibration solutions of potassium sulfate for the determination of sulfur

Slowly dried capsules and their contents at a temperature of from 80 °C to 90 °C for 2 h and cooled in a desiccator.

Prepared tin capsules, placed in accordance with table 3 in seven ceramic crucibles (5.2) as shown in Appendix A.

7.4.1.3 preparation for the construction of calibration curve for the joint determination of carbon and sulfur

Prepared tin capsule with the standard solutions of potassium sulfate (4.7) and barium carbonate (4.6) placed in accordance with table 4 in seven ceramic crucibles (5.2) as shown in Appendix A.


Table 4 — Calibration a series of standard substances for the joint determination of carbon and sulfur

7.4.2 Burning

Crucibles prepared as shown in Appendix A, are placed on a special stand and first burn the contents of the crucible 7 with the maximum number of carbon and/or sulfur, then the contents of the crucible 6 to test.

Make the amendment in testimony at the appropriate value.

Burn the contents of other crucibles and record results to verify the linearity of the graph.

Note — as a matrix element all the crucibles introduced sample of pure iron, equal to 0,400 g.

7.5 analysis of

Sample unknown samples are placed in crucibles, as shown in Appendix A, and is carried through the analysis as well as under construction of calibration curve. When operating the analyzer should follow the manufacturer’s instructions.

8 Processing of results

8.1 calculation of the mass fraction of carbon and sulfur

The mass fraction of carbon and sulfur in the analyzed sample is determined by calibration schedule (7.4) and the corresponding readings given the importance of the results of the blank experience.

The total value of the blank sample from all sources of pollution (oxygen, iron, tin capsules, tungsten) shall not exceed 0.01 wt.% for carbon and 0.001% by weight. for sulphur.

8.2 accuracy of the method

8.2.1 Precision and allowable discrepancies

The precision of this analytical method is expressed using the following regression equation*:
_______________
* Additional information in appendices D and E.

for carbon:

; (1)

; (2)

; (3)

; (4)

for sulphur:

; (5)

; (6)

; (7)

, (8)

where  — mass fraction of carbon or sulphur, %, pre-dried sample, calculated as follows:

for equations (1), (3), (5) and (7): inter-laboratory average value of results of parallel measurements obtained in conditions of repeatability;

for equations (2), (4), (6) and (8): interlaboratory average value of measurement results (8.2.5) two laboratories;

 — limit repetition;

 — the limit of reproducibility;

 — standard deviation of repeatability;

 — the standard deviation of reproducibility.

8.2.2 Determination of results of measurements

After evaluating the results of the parallel measurements of the admissibility of the results recognize, comparing them with the limit of repeatability , calculated according to the equation (1), preparing the crucible, as shown in Appendix A, and receive a final measurement result (8.2.5).

8.2.3 inter-laboratory precision

Interlaboratory precision is used for the conformity assessment results presented by the two laboratories. It is assumed that both laboratories analyze the samples and processing of results according to the same procedure as described in 8.2.2.

Calculate the arithmetic mean value of the determination results of the two laboratories according to the following formula

, (9)

where is the result of the determination presented by the laboratory of 1;

 — the result of the determination presented by the laboratory 2.

Substitute the value of is in equation (2) and calculate the limit of reproducibility .

If the final results are satisfactory.

8.2.4 Validation

The correctness of the analytical method should be checked with the reproduction of the values of certified characteristics according to the results of inter-laboratory experiment in a certified standard sample (ASO) or standard sample (CO).

Calculate an analytical result for ASO/using the procedures in 8.1 and 8.2, and compare it with the certified value .

In this case there are two possible situations:

a) the difference between the result and certified value is statistically insignificant;

b) the difference between the result and certified value is statistically significant,

where the result is reproduced in the laboratory by analysis of certified reference materials;

 — certified value specifications for ASO/;

 — value, depending on the type used ASO/SO:

for ASO certified under the program of interlaboratory tests

, (10)

where  — dispersion of the certified value (0 for SB, certified by only one laboratory);

 — the number of re-definitions, the received playback characteristics of ASO/SO.

WITH certified by only one laboratory, should be avoided except in those cases when it is known that they have an unbiased certified value.

8.2.5 Calculation of the final result

The final result represents the arithmetic mean value of the satisfactory analytical results for the sample analyzed or a value defined in a different way, for example using operations specified in Annex b, which is calculated with a precision to five decimal places and rounded to three decimal places as follows:

a) if the final figure of the fourth decimal place is less than 5, it is discarded and the digit of the third decimal place left unchanged;

b) if the digit to the fourth decimal place is 5 and there is a digit other than 0, the fifth decimal place or digit if the fourth decimal place is greater than 5, the digit in the third decimal place is increased by one;

c) if the digit to the fourth decimal place is 5 and the digit 0 is on the fifth decimal place, the 5 is discarded and the digit at the third decimal place left unchanged if it is equal to 0, 2, 4, 6 or 8, and increase by one if it is equal to 1, 3, 5, 7 or 9.

9 test report

The test report should include the following information:

— name and address of the testing laboratory;

— the date of publication of the test report;

— reference to this standard;

— information necessary for identification of the sample;

the results of the test;

— any unusual features noted during the analysis, and any operations not specified in this standard that could affect the results of the analysis of both the samples and certified standard substances.

Annex a (mandatory). The boot sequence of the crucible

Appendix A
(required)

Figure A. 1 — Sequence of loading of the crucible

1 — tungsten flux (4.3): 1.9 grams; 2 — pure iron (4.4): 0.4 g; 3 — analytical sample (7.2) or barium carbonate (4.6): 0.4 g; 4 — tin capsule (4.5); 5 — pure iron (4.4): 0.9 g

Figure A. 1

Annex b (recommended). Scheme eligibility check of the measurement results

The App
(recommended)

Start with parallel dimensions

Figure B. 1 — Scheme of the eligibility check of the measurement results

Figure B. 1

Application (recommended). Features of industrial induction furnaces for high frequency combustion samples and infrared sulfur analysers

Application
(recommended)

C. 1 Burning

The incinerator consists of an inductor and a high-frequency generator. The combustion chamber is a quartz tube which is mounted in the inductor. This tube has at the ends of the metal plate, reinforced with metal rings. In metal plates has inlet and outlet openings for the gas filter on the outlet to prevent the ingress of dust particles into the detection system.

The generator is typically a plant with capacity from 1.2 to 2.5 kW; the generated frequency may differ in the units of specific manufacturers. Energy from the generator serves to the induction coil that covers a quartz shielding tube and, as a rule, is cooled by air.

The crucible containing the sample, flux and flux, is placed on a stand which is set so that in the raised position the sample in the crucible is exactly inside the induction coil. This arrangement ensures effective communication when power is applied.

Typical sizes of crucibles for combustion are:

— height 25 mm;

— outer diameter — 25 mm;

— inner diameter — 20 mm;

— wall thickness — 2.5 mm;

— base thickness — 8 mm.

The diameter of the inductor, number of turns and dimensions of the furnace determine the degree of frequency; these parameters sets the instrument manufacturer. The generated temperature depends partly on these factors, but also on the properties of the metal in the crucible, the shape of the sample and the mass of the substances. Operator with some experience, can also to some extent to change these factors.

It is important that the oxides that are formed during combustion was absorbed by a filter of glass; to remove accumulated oxides, dust collector filter should be cleaned as often as possible.

C. 2 Infrared gas analyzer

The products of combustion are collected in a certain (specified) amount in the atmosphere of oxygen at a controlled pressure, and the mixture analyzed for the presence WITHand/or SO. The content of coand/or SOin a continuous oxygen flow can also be recorded during the allocation of gases in the combustion process.

The carrier gas is oxygen, containing WITHand/or SOthat passed through the analyzer system consisting of an infrared cell, usually type Luft or its equivalent (in solid state), where the measured specific absorption of infrared radiation.

Electronic measurement signal absorption is typically converted into a digital display of the contents of dioxide of carbon and/or sulfur, in percent. Analyzers are usually provided with electronic devices for adjustment of the zero scale value of the instrument (compensation for the idle experience), set the slope of the calibration curve and correction curve in case of deviation from straightness.

The devices can also be equipped with built-in automatic weighing scale and a system of correction of weight of the samples. Modern devices typically use a microprocessor.

Annex D (informative). The output of regression equations and permissible differences

Appendix D
(reference)

Regression equations in 8.2.1 were obtained by statistical evaluation of the results of international experiments conducted from 1986 to 1988 on four samples of direct reduced iron in which took part 13 laboratories from seven countries.

Graphical representation of precision data are given in Appendix E.

Used samples are listed in table D. 1.

Note 1 — Report on international experiments and statistical analysis of the obtained results (document ISO/TC 102/SC 2 N 929Е, November 1988) can be obtained through the Secretariat ISO/TC 102/SC.

Note 2 — Statistical analysis was carried out according to ISO 5725−2.


Table D. 1 — Mass fraction of carbon and sulfur in the samples

Annex E (informative). Data precision obtained in the course of the international experiment

Annex E
(reference)

Figure E. 1 — Processing using the least squares method based on the value of X for carbon

 — limit repetition;

 — the limit of reproducibility;

 — standard deviation of repeatability;

 — the standard deviation of reproducibility.

Figure E. 1 — Processing using the least squares method based on the value for carbon

Figure E. 2 — Processing method of least squares based on the value of X for sulfur

 — limit repetition;

 — the limit of reproducibility;

 — standard deviation of repeatability;

 — the standard deviation of reproducibility.

Figure E. 2 — Processing method of least squares based on the value for sulfur

Annex F (informative). Data on compliance with national standards of the Russian Federation the reference to international standards

Appendix F
(reference)

Table F. 1