GOST 21639.6-93

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  ГОСТ 21639.6-93

GOST 21639.6−93 Fluxes for electroslag remelting. Method of determination of phosphorus

GOST 21639.6−93

Group B09

INTERSTATE STANDARD

Fluxes for electroslag remelting

METHOD OF DETERMINATION OF PHOSPHORUS

Fluxes for electroslag remelting.
Method for determination of phosphorus

OKS 71.040.040*
AXTU 0709

________________

* In the index «National standards» 2006 ACS 25.160.20. -

Note the «CODE».

Date of introduction 1996−01−01

Preface

1 PREPARED by the Russian Federation — Technical Committee TC 145 «monitoring Methods of steel products"

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 17 February 1993.

The adoption voted:

3 Decree of the Russian Federation Committee on standardization, Metrology and certification from 14.06.95 No. 300 interstate standard GOST 21639.6−93 introduced directly as state standard of the Russian Federation from January 1, 1996

4 REPLACE GOST 21639.6−76

1 SCOPE

This standard sets the photometric method for the determination of phosphorus in fluxes for electroslag remelting at a mass fraction of from 0.002 to 0.04%.

The method is based on the formation of the molybdophosphoric heterophilically with subsequent restoration of its ascorbic acid in the presence of potassium Armenonville to complex compound, colored blue, and measuring the optical density of the solution on the spectrophotometer or photoelectrocolorimeter.

2 NORMATIVE REFERENCES

The present standard features references to the following standards:

GOST 83−79 Sodium carbonate. Specifications

GOST 3118−77 hydrochloric Acid. Specifications

GOST 3760−79 Ammonia water. Specifications

GOST 3765−78 Ammonium molybdate. Specifications

GOST 3773−72 Ammonium phosphate disodium. Specifications

GOST 4198−75 Potassium phosphate odnosemjannyj. Specifications

GOST 4204−77 sulfuric Acid. Specifications

GOST 4332−76 Potassium carbonate — sodium carbonate. Specifications

GOST 4461−77 nitric Acid. Specifications

GOST 5962−67 rectified ethyl Alcohol. Specifications*

GOST 10484−78 hydrofluoric Acid. Specifications

GOST 21639.0−93 Fluxes for electroslag remelting. General requirements for methods of analysis
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* On the territory of the Russian Federation GOST R 51652−2000, hereinafter. — Note the CODE.

3 GENERAL REQUIREMENTS

General requirements for method of analysis according to GOST 21639.0.

4 APPARATUS, REAGENTS AND SOLUTIONS

Spectrophotometer or photoelectrocolorimeter.

Muffle furnace with heating temperature up to 1000 °C.

Perchloric acid, a solution with a mass concentration of 1510 g/DM;

Hydrochloric acid according to GOST 3118 and diluted 1:1, 5:95.

Nitric acid according to GOST 4461.

Ascorbic acid, freshly prepared solution with a mass concentration of 20 g/DM.

Sulfuric acid according to GOST 4204, and diluted 1:1.

Hydrofluoric acid according to GOST 10484.

Ammonium chloride according to GOST 3773 and the solution with a mass concentration of 10 g/DM.

Potassium carbonate — sodium carbonate according to GOST 4332.

Sodium carbonate according to GOST 83.

Sodium peroxide.

Iron (III) nitrate 9-water solution with the mass concentration of 180 g/DM: 180 g of the reagent is dissolved by heating at 300−400 cmof water with the addition of 5 cmof nitric acid, filtered into a measuring flask with a capacity of 1 DM, cooled, made up to the mark with water and mix.

Ammonia water according to GOST 3760.

Rectified ethyl alcohol according to GOST 5962.

Ammonium molybdate according to GOST 3765 solution (recrystallized) with the mass concentration of 50 g/DM: 250 g of reagent was dissolved in 400 cmof water at a temperature of 80 °C. the Solution is filtered on a filter of dense, cooled, poured 300 cmof ethyl alcohol, mixed well and after 1 h the precipitate is vacuum-filtered on a medium density filter placed in a Buchner funnel. The precipitate is then washed 2−3 times with ethanol and dried.

1.74 g of the recrystallized ammonium molybdate dissolved in 100 cmof water, poured 20,8 cmof sulphuric acid, cool, add water to a volume of 250 cmand mixed.

Potassium armanavicius, a solution with a mass concentration of 3 g/DM.

Potassium phosphate according to GOST odnosemjannyj 4198.

Standard solutions

Solution a: 0,4393 g of single potassium phosphate, previously dried at a temperature of 100−110 °C, dissolved in water, placed in a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

Mass concentration of phosphorus in solution And is equal to 0.0001 g/cm.

Solution B: 10 cmsolution And placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

Mass concentration of phosphorus in solution B is equal to 0,00001 g/cm.

5 ANALYSIS

5.1 Decomposition of the flux is carried out by two methods.

Method I

Weighed flux weighing 0.5 g is placed in stekloproduktsii crucible, mixed with 1.5 g of potassium carbonate — sodium carbonate, is added to eight times the amount of sodium peroxide and fused in a first, less hot zone of the muffle, stirring the contents of the crucible to melt the masses, then kept at a temperature of 650−700 °C for 1−2 min.

After that, the crucible was cooled, placed in a beaker with a capacity of 300−400 cmand leached m 100−150 cmof water. Then the crucible is washed, removed. In the glass carefully pour the hydrochloric acid to dissolve the hydroxide metal, boil, pour 2 cmof iron nitrate, 20 cmof ammonium chloride, is heated to a temperature of 70−80 °C and pour ammonia until complete precipitation of the hydroxide.

The precipitate was filtered on a medium density filter and washed 6−8 times with hot solution of ammonium chloride. With water transfer the precipitate into the beaker in which precipitation was carried out, the filter is washed with 20 cmof boiling hydrochloric acid 1:1 and washed 5−6 times with hot water.

The solution was cooled, poured into a volumetric flask with a capacity of 100 cm, made up to the mark with water, mixed and filtered.

Method II

Weighed flux weighing 0.5 g is placed in a conical flask with a capacity of 100 cm, flow 20 cmmixture of nitric and hydrochloric acids in a ratio of 1:3 and moderately heated to dissolve the sample. The solution was evaporated to dryness, then pour 10 cmof hydrochloric acid and again evaporated to dryness, this operation is repeated.

Salt is dissolved in 10 cmof hydrochloric acid in low heat, pour 20 cmof water and filtered through a medium density filter in a glass with a capacity of 200 cm. The glass and the filter cake was washed 3−4 times with hot hydrochloric acid 5:95 and water. Retain the filtrate — the basic solution.

The filter with precipitate was placed in a platinum crucible, incinerated and calcined at a temperature of 800−900 °C. the crucible with the precipitate is cooled, add 2−3 drops of water, 3−5 drops of sulfuric acid 1:1, 5−6 cmhydrofluoric acid and cautiously evaporated to dryness. The residue in the crucible is fused with 1 g of sodium carbonate at a temperature of 950−1000 °C. After that the crucible was cooled, placed in a beaker with a capacity of 250 cmand leached m 60 cmof water. The contents of the Cup combined with the main solution is evaporated, poured into a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

Select aliquot part of the solution, depending on the mass fraction of phosphorus specified in table 1 in a conical flask with a capacity of 100 cm, pour 1 cmof perchloric acid and evaporate to copious fumes of perchloric acid. To the residue poured in 50 cmof water, heated to dissolve the salts, cooled, poured 5 cmof ammonium molybdate, 5 cmof ascorbic acid and 1 cmArmenonville potassium. The solution is poured into a measuring flask with a capacity of 100 cm, made up to the mark with water and mix.


Table 1 — Volume aliquote part of the solution

The optical density of analyzed solution are measured after 5−10 min on the spectrophotometer at a wavelength of 830 nm or photoelectrocolorimeter in a range of wavelengths from 620 to 670 nm.

A solution of comparison used water.

After subtracting the value of optical density of the solution in the reference experiment from the value of the optical density of the sample solution find the mass of phosphorus for the calibration schedule.

5.2 For constructing the calibration curve in seven of the eight conical flasks with a capacity of 100 cmis taken 0,5; 1,0; 1,5; 2,0; 2,5; 3,0 and 4.0 cmstandard solution B, which corresponds to 0,000005; 0,000010; 0,000015; 0,000020; 0,000025; 0,000030 and 0,000040 g of phosphorus. In each flask pour in 1 cmof perchloric acid and evaporate to copious fumes of perchloric acid. To the residue poured in 50 cmof water, heated to dissolve the salts, cooled, poured 5 cmof ammonium molybdate, 5 cmof ascorbic acid and 1 cmArmenonville potassium. The solutions were poured into volumetric flasks with a capacity of 100 cm, made up to the mark with water and mix.

Optical density of the solution measured as described in 5.1. Solution comparison is the solution of the eighth flask containing a standard solution of phosphorus.

According to the obtained values of optical densities and corresponding mass of phosphorus build a calibration curve.

6 PROCESSING OF THE RESULTS

6.1 Mass fraction of phosphorus () in percent is calculated by the formula

,

where is the mass of phosphorus in the solution of the sample, was found in the calibration schedule g;

 — the weight of the portion corresponding to aliquote part of the solution,

6.2 Standards of accuracy and standards for monitoring the accuracy of determining the mass fraction of phosphorus are shown in table 2.


Table 2 — Standards accuracy control