GOST 21639.7-93

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  ГОСТ 21639.7-93

GOST 21639.7−93 Fluxes for electroslag remelting. Methods for determination of calcium fluoride

GOST 21639.7−93

Group B09

INTERSTATE STANDARD

Fluxes for electroslag remelting

METHODS FOR DETERMINATION OF CALCIUM FLUORIDE

Fluxes for electroslag remelting.
Methods for determination of calcium fluoride

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. 302 inter-state standard GOST 21639.7−93 introduced directly as state standard of the Russian Federation from January 1, 1996

4 REPLACE GOST 21639.7−76

1 SCOPE

This standard specifies pyrohydrolysis and titrimetric methods for determination of calcium fluoride in flux for electroslag remelting at a mass fraction from 8 to 95%.

2 NORMATIVE REFERENCES

The present standard features references to the following standards:

GOST 61−75 acetic Acid. Specifications

GOST 83−79 Sodium carbonate. Specifications

GOST 1027−67 Lead acetate. Specifications

GOST 3760−79 Ammonia water. Specifications

GOST 3770−75 Ammonium carbonate. Specifications

GOST 4233−77 Sodium chloride. Specifications

GOST 4234−77 Potassium chloride. Specifications

GOST 4328−77 Sodium hydroxide. Specifications

GOST 4461−77 nitric Acid. Specifications

GOST 4470−79 of Manganese (IV) oxide. Specifications

GOST 5817−77 tartaric Acid. Specifications

GOST 5962−67 rectified ethyl Alcohol. Specifications*
________________
* On the territory of the Russian Federation GOST R 51652−2000, hereinafter. — Note the CODE.

GOST 9428−73 Silicon (IV) oxide. Specifications

GOST 10216−75 of Bismuth (III) oxide. Specifications

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

GOST 18300−87 ethyl rectified technical. Specifications

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

3 GENERAL REQUIREMENTS

General requirements for methods of analysis GOST 21639.0.

4 PYROHYDROLYSIS METHOD

4.1 the essence of the method

The method is based on the decomposition of calcium fluoride with water vapor in a tube furnace at a temperature of 1250−1350 °C With a catalyst or a multicomponent oxide of aluminum.

Released by pyrohydrolysis hydrofluoric acid is absorbed titrated with sodium hydroxide solution.

4.2 Equipment, reagents and solutions

The installation for determining the mass fraction of calcium fluoride (figure 1) consists of an oxygen cylinder 1, provided with a pressure-reducing valve; a gas washing bottle to clean oxygen 2filled with sodium hydroxide solution with a mass concentration of 200 g/DM; spherical tube 3, filled with cotton wool and serves to trap the hydroxide, entrained oxygen; bulb 4 to produce steam; tube 5 (stainless steel or brass) with an internal diameter of 1.2−1.5 mm, connecting rubber tube with a quartz tube 6 with an inner diameter of 20−22 mm, length 550 mm; platinum-rhodium thermocouple 7connected to an automatic potentiometer type KSP-2; porcelain pumps 8 N 2−9 GOST 9147 (before use, the boat is calcined at operating temperature for 4−5 min); dogtramadol furnace 9 with silicafume heaters that provide heating to the temperature 1350 °C (the oven should have a slope of 3−4° in the direction of the receiver); ammeter 10 scale 50 for controlling the current to the heater; refrigerator 11, a holder 12; burettes 13 with auto zero; the flask 14 with a titrated solution of sodium hydroxide; absorption vessel 15; magnetic stirring bar 16; the bubbler 17; M14 socket 18, which connects the quartz tube with a bubble counter; autotransformer 19 type RNO-250−10.

Figure 1 — Installation for determination of potassium fluoride

Figure 1 — Installation for determination of potassium fluoride

Hydrochloric acid according to GOST 3118, solution with molar concentration of the equivalent 0,1 mol/DM.

Bismuth (III) oxide according to GOST 10216.

Of tungsten oxide.

Manganese (IV) oxide according to GOST 4470.

A multicomponent catalyst (WO: BiO: MnO= 1:1:0,8).

Of aluminium oxide.

The indicator methyl red.

The indicator methylene blue (medical).

Rectified ethyl alcohol according to GOST 5962 or GOST 18300.

Mixed indicator: 0.125 g methyl red is ground in a porcelain mortar with 0,083 g of methylene blue are then dissolved in 100 cmof ethanol. With the dissolution of the indicator is triturated in a mortar pestle.

Flat water: to 1 DMof boiled water pour 2 cmof the mixed indicator.

Sodium hydroxide according to GOST 4328, solutions with molar concentration of 0.05 mol/DMmass concentration of 200 g/DM.

The mass concentration of sodium hydroxide solution (in), expressed in g of fluorine per 1 cm ofthe test hydrochloric acid and calculated by the formula

, (1)

where gram equivalent of fluorine;

the molarity of the sodium hydroxide solution.

The mass concentration of sodium hydroxide solution (in), expressed in g of calcium fluoride per 1 cmof a solution, calculated by the formula

, (2)

where  — mass fraction of calcium fluoride in the standard sample, %;

 — weight of standard sample, g;

 — the volume of sodium hydroxide solution consumed for titration of the evolved hydrofluoric acid, cm;

 — the volume of sodium hydroxide solution consumed for titration of the solution in the reference experiment,

cm.

4.3 analysis

Weighed flux weighing 0.1−0.2 g (0.1 g — at a mass fraction of calcium fluoride more than 50,0%) placed in a porcelain boat, which had previously made the double amount of catalyst and mix thoroughly. A boat placed in a quartz tube, heated to a temperature of 1250−1350 °C. the Tube is quickly closed with a rubber stopper with a metal nozzle through which flow oxygen, saturated with water vapor, at a speed of 2−3 cm/s.

Formed in the process of pyrohydrolysis hydrofluoric acid is carried off the oxygen with water vapor through the condenser to the receiver.

The receiver pre-poured 100−150 cmflat water when the mass fraction of calcium fluoride up to 30% and 150−250 cmwhen the mass fraction of calcium fluoride more than 30%. The separated hydrofluoric acid octarepeat the sodium hydroxide with the mass concentration of 0.05 mol/DMto change the color of the solution from purple to green. The time of hydrolysis is chosen experimentally for each installation, with the increase of the mass fraction of calcium fluoride, the time of hydrolysis increased from 10 to 20 min.

The amount of bound hydrofluoric acid with sodium hydroxide to determine mass fraction of calcium fluoride.

Mass concentration of sodium hydroxide set at the standard sample of the flux with the corresponding fluoride of calcium.

4.4 Processing of results

4.4.1 Mass fraction of calcium fluoride () in percent is calculated by the formula

, (1)

where is the mass concentration of the sodium hydroxide solution, expressed in g of calcium fluoride per 1 cmof solution;

 — the volume of sodium hydroxide solution consumed for titration of the test solution, cm;

 — the volume of sodium hydroxide solution consumed for titration of the solution in the reference experiment, cm;

 — the weight of the portion,

If the mass concentration of sodium hydroxide is expressed in g/cmfluorine, enter the ratio with the fluorine in calcium fluoride — 2,054

7.

4.4.2 Standards of accuracy and standards for monitoring the accuracy of determining the mass fraction of calcium fluoride are shown in table 1.


Table 1 — Standards of accuracy control

5 TITRIMETRIC METHOD

5.1 the essence of the method

The method is based on the deposition of fluorine ions in the form of perchloride lead. The excess of lead is titrated with a solution of Trilon B. the Sample of the flux transferred into a solution by melting them with sodium carbonate in platinum crucibles. Aluminum is separated in the form of hydroxide carbonate ammonium.

5.2 Reagents and solutions

Sodium carbonate according to GOST 83.

Silicon dioxide according to GOST 9428.

Nitric acid according to GOST 4461, diluted 1:4.

Ammonium carbonate according to GOST 3770.

Methyl orange indicator, aqueous solution with a mass concentration of 1 g/DM.

Acetic acid according to GOST 61.

Sodium chloride according to GOST 4232, a solution with a mass concentration of 50 g/DM.

Tartaric acid according to GOST 5817, a solution with a mass concentration of 50 g/DM.

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

Potassium chloride according to GOST 4234.

Indicator eriochrome black T: 0.2 g of the indicator is triturated with 20 g of potassium chloride.

Sodium fluoride according to GOST 4463.

A standard solution of 2.21 g of sodium fluoride are dissolved in 200 cmof water and the 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 0,001 g of fluorine.

Lead acetate according to GOST 1027, the solution with a mass concentration of 25 g/DM: 25 g of acetate of lead dissolved in 200−300 cmof water with the addition of 10 cmof acetic acid.

The solution was transferred to volumetric flask with a capacity of 1 DM, adjusted to the mark with water, mixed if the solution is cloudy — filtered.

Salt is the disodium Ethylenediamine-N, N, N', N'-tetraoxane acid, 2-water (Trilon B) according to GOST 10652, solution with molar concentration of 0.025 mol/DM: 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 in the following way: 3 g of sodium carbonate is placed in a platinum crucible, add 0.2 g of powdered silicon dioxide, cover 0.5 g of sodium carbonate, the crucible is closed with the lid and fused in a muffle at a temperature of from 950 to 1000 °C for 15 min. the Crucible and lid are placed in a beaker with a capacity of 250−300 cm; 50 cm pour thehot water leached when heated. The crucible and the lid removed from the beaker, washed several times with water and poured 25 cmstandard fluorine solution, transfer the contents of the Cup into a measuring flask with a capacity of 200 cm, made up to the mark with water, mix. The solution was filtered in a dry flask through a dry filter medium density, discarding first portion of filtrate.

Aliquot part of the solution is 50 cmis placed in a beaker with a capacity of 300 cm, pour 2−3 drops of methyl orange and neutralize with nitric acid until the solution colour from red to orange. Add 5 g of ammonium carbonate and boiled until the odour of ammonia, and add 20 cmof hot water, filter in a glass with a capacity of 300 cmusing a medium density filter, washed 8−10 times with hot water. The filtrate is neutralized by methyl orange nitric acid until the solution colour from orange to red. Add 10 drops of acetic acid, 20 cmof sodium chloride solution from the burette pour 30 cmacetate of lead. The solution was stirred, heated to a temperature of 60−70 °C, then mixed to the sediment and leave it for 12 h the Contents of the beaker transferred to a volumetric flask with a capacity of 250 cm, is diluted to the mark with water and stirred, then filtered in a dry flask with a capacity of 250 cmthrough a dry filter. Aliquot part of the solution is 50 cmis placed in a conical flask with a capacity of 250 cm, flow 10 cmof tartaric acid, 10 cmof ammonia, 0.1 g of the indicator eriochrome black and titrate the excess of lead with a solution of Trilon B to switch the color of the solution from purple-violet to blue.

Mass concentration of Trilon B (), expressed in g of calcium fluoride per 1 cmof a solution, calculated by the formula

, (4)

where is the mass concentration of the solution of sodium fluoride, expressed in g of fluorine per 1 cmof the solution in g/cm;

 — the volume of a standard solution of sodium fluoride, cm;

 — the ratio of fluoride to calcium fluoride;

 — the volume of solution of acetate of lead, taken with excess, see;

 — volume of solution Trilon B, used for titration of excess of acetate of lead, cm;

 — the ratio between the volumes of the solutions of acetate of lead and Trilon B is calculated by the formula

, (5)

where is the volume of solution of acetate of lead, taken for titration, cm;

 — volume rastrera Trilon B, used for titration of excess of acetate of lead, see.

The ratio is determined as follows: 5 cmof a solution of acetate of lead is placed in a conical flask with a capacity of 250 cm, flow 50 cmwater, 10 cmof tartaric acid, 10 cmof ammonia, 0.1 g of the indicator eriochrome black and titrated until the transition of color from lilac-purple to Gol

gonna kill.

5.3 analysis

The linkage of flux with a mass of 0.2 g when the mass fraction of calcium fluoride up to 50% or 0.1 g when the mass fraction of calcium fluoride more than 50% is placed in a platinum crucible, add 0.2 g of powdered silicon dioxide, 3 g of sodium carbonate, stirred, sprinkled on top of the sample 0.5 g of sodium carbonate. Crucible lid and the sample is gently melted first in the less hot zone of the muffle, then kept at a temperature of 950−1000 °C for 15 min. the Hot melt was poured onto a polished plate of stainless steel. The frozen melt and the crucible is placed in a beaker with a capacity of 300 cm, 100 cm pouredhot water and boiled until complete decomposition of water. The crucible and the lid removed from the beaker, washed several times with warm water. The solution with precipitate was cooled, transferred to a volumetric flask with a capacity of 200 cm, made up to the mark with water and mix. The solution was filtered in a dry flask through a dry filter medium density, discarding first portion of filtrate.

Aliquot part of the solution is 50 cmis placed in a beaker with a capacity of 300 cm, add 2−3 drops of methyl orange and neutralize with nitric acid until the solution colour from red to orange. Add 5 g of ammonium carbonate and boiled until the odour of ammonia (in this case silicic acid and aluminum stand out as a gelatinous precipitate), then add 20 cmof hot water, filter in a glass with a capacity of 300 cmusing the medium density filter and washed with hot water 8−10 times. The filtrate is neutralized by methyl orange nitric acid until the solution colour from orange to red. Add 10 drops of acetic acid, 20 cmof potassium chloride solution from the burette pour the lead acetate — 30 cmwhen the mass fraction of calcium fluoride up to 50%, 40 cm — more than 50%. The solution was stirred, heated to a temperature of 60−70 °C, then mixed to the sediment and leave it for 12 h the Contents of the beaker transferred to a volumetric flask with a capacity of 250 cm, is diluted to the mark with water and stirred, filtered through a dry filter into a dry flask with a capacity of 250 cm.

Aliquot part of the solution is 50 cmis placed in a conical flask with a capacity of 250 cm, flow 10 cmof tartaric acid, 10 cmof ammonia, 0.1 g of the indicator eriochrome black and titrate the excess of lead with a solution of Trilon B to switch the color of the solution from purple-violet to blue.

Throughout the analysis is carried out to control

lny experience.

5.4 processing of the results

5.4.1 Mass fraction of calcium fluoride () in percent is calculated by the formula

, (6)

where is the volume of solution of acetate of lead, taken for deposition of fluorine-ion, cm;

 — volume of solution Trilon B, used for titration of excess of acetate of lead, cm;

 — the ratio between the volumes of the solutions of acetate of lead and Trilon B, set by reference to experience;

 — mass concentration of Trilon B, expressed in g of calcium fluoride per 1 cmof the solution in g/cm;

 — the weight of the portion,

G.

5.4.2 Norms of accuracy and norms control the accuracy of determining the mass fraction of calcium fluoride are shown in table*.
________________
* The text matches the original. Probably should read «table 1». — Note the CODE.