GOST 21639.2-93

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  ГОСТ 21639.2-93

GOST 21639.2−93 Fluxes for electroslag remelting. Methods for determination of aluminium oxide

GOST 21639.2−93

Group B09

INTERSTATE STANDARD

Fluxes for electroslag remelting

METHODS FOR DETERMINATION OF ALUMINIUM OXIDE

Fluxes for electroslag remelting.
Methods for determination of aluminium oxide

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 Technical Committee TC 145 «monitoring Methods of steel products"

INTRODUCED by Gosstandart of Russia

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. 297 inter-state standard GOST 21639.2−93 introduced directly as state standard of the Russian Federation from January 1, 1996

4 REPLACE GOST 21639.2−76

1 SCOPE

This standard specifies the titrimetric and atomic absorption methods for determination of aluminium oxide in flux for electroslag remelting at a mass fraction of from 1 to 60%.

2 NORMATIVE REFERENCES

GOST 61−75 acetic Acid. Specifications

GOST 2053−77 Sodium sulfurous 9-aqueous. Specifications

GOST 3117−78 Ammonium acetic acid. Specifications

GOST 3118−77 hydrochloric Acid. Specifications

GOST 3760−79 Ammonia water. Specifications

GOST 3773−72 Ammonium phosphate disodium. Specifications

GOST 4204−77 sulfuric Acid. Specifications

GOST 4233−77 Sodium chloride. Specifications

GOST 4328−77 Sodium hydroxide. Specifications

GOST 4332−76 Potassium carbonate — sodium carbonate. Specifications

GOST 4461−77 nitric Acid. Specifications

GOST 4463−76 Sodium fluoride. Specifications

GOST 5457−75 Acetylene, dissolved and gaseous. Specifications

GOST 5822−78 Zinc acetate 2-aqueous. Specifications*

GOST 5962−67 rectified ethyl Alcohol. Specifications**

GOST 7172−76 Potassium preservatory. Specifications

GOST 9656−75 boric Acid. Specifications

GOST 10484−78 hydrofluoric Acid. Specifications

GOST 10652−73 Salt is the disodium Ethylenediamine-N, N', N'-tetraoxane acid, 2-water (Trilon B)

GOST 11069−74 Aluminium primary. Stamps***

GOST 18300−87 ethyl rectified technical. Specifications

GOST 21639.0−93 Fluxes for electroslag remelting. General requirements for methods of analysis.

________________
* Probably a mistake of the original. Should read GOST 5823−78;
** On the territory of the Russian Federation GOST R 51652−2000;
*** On the territory of the Russian Federation GOST 11069−2001, hereinafter. — Note the CODE.

3 GENERAL REQUIREMENTS

General requirements for methods of analysis GOST 21639.0.

4 TITRIMETRIC METHOD

4.1 the essence of the method

The method is based on the formation in a weakly acidic environment, the complex aluminum compounds with Trilon B and titrating its excess with a solution of acetate of zinc.

Deformity elements (iron, titanium, etc.) previously separated by sodium hydroxide, small amounts of manganese, Nickel, sulfur is associated with sodium.

4.2 Reagents and solutions

Ammonium chloride according to GOST 3773, solutions with mass concentration of 10 and 200 g/DM.

Ammonia water according to GOST 3760 and diluted 1:1.

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

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

Hydrofluoric acid according to GOST 10484.

Potassium carbonate — sodium carbonate according to GOST 4332.

Boric acid according to GOST 9656.

Mix for fusion of the two parts of potassium carbonate — sodium carbonate is mixed with one part boric acid.

Perchloric acid, qualifications H. h, solution with the mass concentration of 1510 g/DMand diluted 1:1.

Perchloric acid saturated with boric acid in a conical flask with a capacity of 1 DMpour 500 cmof perchloric acid (1:1), heated to 50 °C and saturated with boric acid.

Nitric acid according to GOST 4461.

Potassium preservatory according to GOST 7172.

Sodium fluoride according to GOST 4463, a solution with a mass concentration of 40 g/DM.

Sodium hydroxide according to GOST 4328, solutions with a mass concentration of 100 and 200 g/DM.

The indicator Congo red, aqueous solution with a mass concentration of 1 g/DM.

The indicator methyl red, alcoholic solution with a mass concentration of 1 g/DM.

Ammonium acetate according to GOST 3117.

Acetic acid according to GOST 61.

Acetate buffer: 500 g ammonium acetate dissolved in water, add 20 cmof glacial acetic acid, mixed and adjusted to a volume of 1 DM.

Methenamine (hexamethylenetetramine), a solution with a mass concentration of 500 g/DM.

Sodium sulfide according to GOST 2053, a solution with a mass concentration of 50 g/DM.

Ethyl alcohol according to GOST 5962 or GOST 18300.

Dition, an alcoholic solution with a mass concentration of 4 g/DM(stored in a dark place for no more than 2−3 days).

Selenology orange indicator: 0.1 g of the indicator is triturated with 10 g of sodium chloride.

Universal indicator paper.

Zinc acetate 2-water according to GOST 5823, solutions with molar concentration of 0.0125 or 0.025 mol/DM: or 2,74 5,48 g of zinc acetate dissolved in 500 cmof water and add 5 cmof glacial acetic acid, transferred to a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

Aluminium, metal brand А000 according to GOST 11069.

Standard aluminium solution: 1 g of metallic aluminium is dissolved in 30 cmof hydrochloric acid (1:1) under low heat. After complete dissolution of the aluminium solution is poured into a measuring flask with a capacity of 1 DM, made up to the mark with water and mix.

1 cmstandard solution contains 0,00189 g of aluminium oxide.

Salt is the disodium Ethylenediamine-N, N, N', N'-tetraoxane acid, 2-water (Trilon B) according to GOST 10652, solutions with molar concentration of 0.0125 or 0.025 mol/DM; 4, 65 or 9.3 g Trilon B dissolved in 250−300 cmof water. The solution was filtered in a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

The mass concentration of the solution Trilon B set by the standard solution of aluminium oxide. To establish the mass concentration of Trilon B in three conical flasks with a capacity of 250 cmpour 5 cmof a standard solution of aluminium oxide, 50 cmwater, 5 cmof sodium hydroxide solution with a mass concentration of 100 g/DM, 20 cmTrilon B and neutralize with hydrochloric acid (1:1) for Congo red to the transition of color from red to blue-violet. To the neutralized solution was poured in a 20 cmacetate buffer, boil for 2−3 minutes, cool, add 0.2−0.3 g kylinalove orange or 3 cmof dithizone, and titrated with zinc acetate to a sharp transition of color from yellow to crimson red.

Mass concentration of Trilon B (), expressed in grams of alumina per 1 cmof a solution, calculated by the formula

, (1)

where is the mass concentration of aluminum oxide in a standard solution, g/cm;

 — the volume of a standard solution of aluminium oxide, see;

 — the volume of Trilon B taken for titration with excess, see;

 — the amount of zinc acetate used for back titration of the excess Trilon B, cm;

 — the ratio of the solutions of Trilon B and zinc acetate.

For establishing a relationship in three conical flasks with a capacity of 250 cmis poured from the burette 10 cmTrilon B, 50 cmwater, 5 cmof sodium hydroxide solution with a mass concentration of 100 g/DM.

The solution is neutralized with hydrochloric acid (1:1) for Congo red to the transition of color from red to blue-violet. Add 20 cmacetate buffer, 0.2−0.3 g kylinalove orange or 3 cmof dithizone and titrated acetic acid with zinc. Ratio () is calculated by the formula

, (2)

where  — the volume of Trilon B taken for titration, cm;

 — the volume of acetate of zinc, cm.

The necessary conditions for the determination of aluminium:

1) the fluoride ion must be completely removed by repeated evaporation with perchloric or sulfuric acid;

2) alkali should not contain sodium carbonate;

3) neutralizing the sodium hydroxide must pour a thin stream with vigorous stirring.

4.3 Preparation for analysis

4.3.1 Decomposition of the flux by melting

The linkage of flux with a mass of 0.5 g mixed in a platinum crucible with 5 g of a mixture for melting, sprinkle the top of the sample 0.5 g of the mixture. The crucible closed with a lid and fused at a temperature of 950−1000 °C for 15 min, cooled, placed in a beaker with a capacity of 400 cm, 150 cm pouredwater, 20 cmof hydrochloric acid and heated until complete dissolution of the melt. The crucible and the lid wash of water over the glass.

The cooled solution was carefully poured 40 cmof sulphuric acid (1:1), heated until the appearance of dense white fumes, cool the walls of the beaker is washed with water and again evaporated to copious fumes of sulfuric acid. The contents of the beaker cool, add 30 cmof hydrochloric acid, 200−250 cmof hot water and heated to dissolve the salts. The solution was cooled, transferred to a volumetric flask with a capacity of 500 cm, made up to the mark with water and mix.

If the flux contains silica and insoluble samples, filter them, filter was placed in a platinum crucible, incinerated and calcined at a temperature of 1000−1100 °C. the Precipitate is moistened with 2−3 drops of water, add 3−4 drops of sulfuric acid (1:1), 3−5 cmhydrofluoric acid and evaporate the contents of the crucible to remove vapors of sulfuric acid.

Fused with a 10-fold amount peacemaking potassium leached m in the 60−80 cmof hot water in a glass with a capacity of 250−300 cm, 30 cm, pouredhydrochloric acid and heated to dissolve the melt. The solution was cooled, combined with the main in a volumetric flask with a capacity of 500 cm, was adjusted to the mark with water, mix. From this solution determine the calcium oxide, magnesium oxide, total iron.

Removal of fluoride may be performed from a separate alikvotnih parts instead of evaporation at all

good.

4.3.2 Decomposition of the flux of perchloric acid

Weighed flux weighing 0.5 g is placed in a platinum Cup, moisten with water, add 5 cmof nitric acid, heated for 5−7 minutes, pour 5−10 cmhydrofluoric acid, then add 10 cmof perchloric acid and evaporate to copious fumes. Wash with water the walls of the Cup, pour 10 cmof perchloric acid saturated with boric acid, and evaporated to dryness. The dry residue cautiously heated at first at the cold end of the muffle, and then calcined at a temperature of 750−800 °C for 2−3 min. Calcined residue is fused with 4−5 g of potassium peacemaking at 750−800 °C for 3−5 min. In a Cup pour 30 cmof hydrochloric acid and 50 cmof hot water, gently heat the contents of the Cup, transferred to a beaker with a capacity of 400−500 cm, Cup well washed with hot water. In a Cup add hot water up to 300−350 cmand heated until complete dissolution of salts. The solution was cooled, transferred to a volumetric flask with a capacity of 500 cm, made up to the mark with water and mix.

If the sample contains barium, the solution may be slightly cloudy. From this solution take aliquote parts and determine the content of aluminium oxide, calcium oxide, magnesium oxide, total iron.

4.4 analysis

4.4.1 Department of Sesqui-oxides with hexamine

Aliquot part of the 200 cmcore solution is placed in a beaker with a capacity of 400−500 cm, add 20 cmof a solution of ammonium chloride with a mass concentration of 200 g/DM, is heated to a temperature of 70−80 °C, pH 2−3 set (for universal indicator paper) or pH meter, preparing the sample for neutralization of methyl red solution of ammonia to sediment and discoloration; an excess of ammonia is neutralized with hydrochloric acid 1:5 to dissolve the precipitated precipitate sesquioxides oxides, and then add 30 cmof hexamine. Sediment precipitated hydroxides allowed to stand at a temperature of 70−80 °C for 5−10 min, and then filtered on a medium density filter and washed 5−6 times with a solution of ammonium chloride with a mass concentration of 10 g/DM, neutralized by ammonia methyl red. The filtrate is used for determining the content of calcium oxide and magnesium oxide, and the residue — to determine the content of aluminium oxide.

4.4.2 Department of Sesqui-oxides with ammonia

Aliquot part of the 200 cmcore solution is placed in a beaker with a capacity of 400−500 cm, add 20 cmof a solution of ammonium chloride with a mass concentration of 200 g/DM; heated to a temperature of 70−80 °C, add 1−2 drops of methyl red, and precipitate sesquioxides oxides with ammonia (1:1), adding it until the color changes of indicator (weak odor). For coagulation of the precipitate the solution was heated for 3−5 min, then filtered on a medium density filter, washed 3−4 times with hot ammonium chloride solution with mass concentration 10 g/DM, neutralized by ammonia methyl red. The precipitate sesquioxides oxides washed from the filter with hot water into a glass, which conducted the deposition, and dissolved in 20 cmof hot hydrochloric acid (1:1), heated to boiling and re-precipitated sesquioxides oxides with ammonia as described above.

The precipitate was filtered through the same filter, washed 5−6 times with hot ammonium chloride solution with mass concentration 10 g/DM. The filtrates are combined and used for determination of calcium oxide and magnesium oxide

.

4.4.3 Sediment Sesqui-oxides washed into the beaker in which to conduct the deposition, the filter is washed with 20 cmof hot hydrochloric acid (1:1), then well washed with hot water. The total volume of the solution should be 60−70 cm. The solution was heated to reflux (complete dissolution of the precipitate) and neutralized with hot sodium hydroxide solution with a mass concentration of 200 g/DMon paper of the Congo under stirring until the transition of color in red, then a thin stream with vigorous stirring poured into an excess of 35−40 cmhot sodium hydroxide and 0.5 cmof sodium sulphide solution. The solution is boiled for 3−4 min to coagulate the precipitate of iron, titanium and cooled. The contents of the beaker transferred to a volumetric flask with a capacity of 250 cm, made up to the mark with water and mix well. The solution is filtered through a dry filter medium density in a dry flask, discarding first portion of filtrate.

Aliquoting a portion of the filtrate and the amount of added solution of Trilon B is determined depending on the content of aluminium in tables 1 and 2.


Table 1 — Volume of solution Trilon B, when mass fraction of aluminium oxide up to 5%

Table 2 — Volume of solution Trilon B for the mass concentration of the alumina from 5 to 60%

The solution is neutralized with hydrochloric acid at Congo red to the transition of color from red to blue-violet, poured 20 cmacetate buffer, boiled for 2−3 min. the Solution was then cooled, add 0.2−0.3 g kylinalove orange or 3 cmof dithizone. Excess Trilon B octarepeat solution of zinc acetate with a molar concentration of 0.0125 or 0.025 mol/DMto a sharp transition in color of the solution from yellow to crimson red. Through the analysis of spend control experience.

4.5 Processing of results

4.5.1 Mass fraction of aluminium oxide () in percent is calculated by the formula

, (3)

where is the mass concentration of the solution Trilon B, expressed in grams of alumina per 1 cmof solution;

 — the volume of the titrated solution of Trilon B taken in excess, cm;

 — the amount of zinc acetate solution consumed for titration of the excess of the solution Trilon B, cm;

 — the ratio of the solutions of Trilon B and zinc acetate;

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

G.

4.5.2. Norms of accuracy and norms control the accuracy of determining the mass fraction of aluminum oxide is shown in table 3.


Table 3 — Standards for monitoring the accuracy of determining the mass fraction of aluminum oxide

5 RAPID TITRIMETRIC METHOD

5.1 the essence of the method

Rapid titrimetric method for the determination of aluminium oxide is used for fluxes with a mass fraction of iron to 0.5%, and not containing titanium.

The method consists in boiling the acid solution with an excess Trilon B.

The acidity of the solution is lowered by addition of ammonia and a buffer solution, the excess Trilon B octarepeat acetate zinc. Trilent aluminum destroy by the addition of sodium fluoride. When heated, the aluminium becomes more durable fluoride connection. Vacant Trilon B octarepeat acetate zinc.

5.2 Reagents and solutions

The mass concentration of zinc acetate set for the standard solution of aluminium oxide. For this purpose a standard solution of aluminium oxide in amount corresponding mass in the sample the test sample was placed in a flask. Further, the definition of lead 5.3.

5.3 analysis

Aliquot part 50−100 cmcore solution is placed in a conical flask with a capacity of 250 cm, add from burette 10−50 cmof the solution Trilon B with molar concentration of 0.0125 or 0.025 mol/DM(depending on the mass fraction of aluminium), neutralized with ammonia, Congo red before transition of colouring from red to blue-purple, add 20 cmacetate buffer, boiled for 2−3 min, when the content of aluminum oxide more than 30% of the boiling should be extended to 7−8 min. the Solution was then cooled, add 0.2−0.3 g kylinalove orange or 2 cmof dithizone, excess Trilon B octarepeat solution of zinc acetate with a molar concentration of 0.0125 or 0.025 mol/DMto a sharp transition in color of the solution from yellow to crimson red. Add 80 cmof sodium fluoride, is heated to transfer the color of the solution from pink to yellow. The solution was cooled, added 0.1 g kylinalove orange or 2 cmof dithizone. Vacant Trilon B from Trianta aluminum octarepeat solution of zinc acetate with a molar concentration of 0.0125 or 0.025 mol/DM.

Through the analysis of spend control experience.

5.4 processing of the results

5.4.1 Mass fraction of aluminium oxide () in percent is calculated by the formula

, (4)

where is the mass concentration of acetate of zinc, expressed in grams of alumina per 1 cmof solution;

 — the volume of solution of acetate of zinc, used for titration of Trilon B, freed from trigonata of aluminium after the addition of sodium fluoride, cm;

 — the volume of solution of acetate of zinc, consumed in the titration of a solution of the reference experiment after the addition of sodium fluoride, cm;

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

.

5.4.2 Norms of accuracy and norms control the accuracy of determining the mass fraction of aluminum oxide is shown in table 3.

6 ATOMIC ABSORPTION METHOD

6.1 the essence of the method

The method is based on measuring the degree of absorption of resonance radiation by free atoms of aluminum, formed as a result of spraying the test solution into the flame nitrous oxide — acetylene.

6.2 Equipment, reagents

Spectrophotometer atomic absorption of any kind with the radiation source for aluminium.

Muffle furnace with heating temperature up to 1000 °C.

Acetylene is dissolved according to GOST 5457. Nitrous oxide gas. The compressor with the receiver, providing compressed air, or compressed air, or compressed air from the air duct with the inlet pressure in the spectrophotometer for at least 2 ATM.

Gelatin food according to GOST 11293, solution with mass concentration 10 g/DM.

The other reagents and solutions — for 4.2.

6.3 analysis

6.3.1 the flux Linkage with a mass of 0.5 g was placed in a platinum crucible, mixed with 5 g of a mixture for fusion and fused in a muffle furnace at a temperature of 950−1000 °C for 15 min. the Cooled crucible is placed in a beaker with a capacity of 250 cm, 50 cm pourhot water, 10 cmof hydrochloric acid and heated to dissolve the salts. The crucible is removed from the beaker and washed with water. If the solution is opaque, it is filtered through a dense filter, washed 2−3 times with hot hydrochloric acid (5:95) and 3−4 times with hot water. The filter is placed in a platinum crucible, dried, incinerated and the residue is fused with 1.5−2.0 g of potassium peacemaking. The cooled melt is leached to 60 cmhot hydrochloric acid (1:5). The solution is attached to the main filtrate. The combined filtrate was evaporated to wet salts, poured 30 cmof hydrochloric acid, heated to dissolve the salts, then pour 60 cmwater, 10 cmgelatin solution, mix, allow to stand in a warm place for 5−7 min and filtered silicic acid through the filter of the average density in the conical flask with a capacity of 250 cm. Precipitate was washed 3−4 times with hot hydrochloric acid (5:95) and 5−6 times with hot water. The solution was evaporated to a volume of 70−80 cm, cooled, placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

Depending on the mass fraction of aluminium oxide taken aliquot part of the solution in accordance with table 4.


Table 4 — Volume aliquote part of the solution

Aliquot part of the solution placed in a conical flask with a capacity of 100 cm, was evaporated to wet salts, pour 4 cmof hydrochloric acid, 15−20 cmof water and heated until complete dissolution of salts. The cooled solution is placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water, mix. Through the analysis of spend control experience.

Spray the solution in the reference experiment and the solution of the sample in the flame nitrous oxide — acetylene is in the order of increasing absorption to obtain stable readings for each solution. Before spraying each solution is sprayed water to wash the system and check the zero point. Measure the atomic absorption of aluminum at a wavelength of 309,3 nm.

After subtracting the atomic absorption of the solution in the reference experiment from the value of atomic absorption of a solution of the sample to find the mass of aluminum in solution of the sample in the calibration graph (in terms of aluminum oxide).

6.3.2 Construction of calibration curve

For construction of calibration curve seven platinum crucibles are placed 5 g of a mixture of alloying and conduct analysis 6.3.1.

In six conical flasks with aliquote part of the melt flow 0,5; 1,0; 2,5; 5,0; 10,0; 15,0 cmstandard solution of aluminium, which corresponds to 0,000945; 0,00189; 0,00472; 0,00945; 0,018895; 0,02834 g of aluminium oxide, for 4 cmof hydrochloric acid, made up to the mark with water and mix.

The seventh flask containing a standard solution that is used for the reference experiment. Measuring the absorbance of the resulting solutions is carried out according to 6.3.1.

6.4 Processing of results

6.4.1 Mass fraction of aluminium oxide () in percent is calculated by the formula

, (5)

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

 — the weight of the portion of the sample,

6.4.2 the Norms of accuracy and norms control the accuracy of determining the mass fraction of aluminum oxide is shown in table 3.