GOST 21639.8-93

• gost-216398-93.pdf (202.43 KiB)
  ГОСТ 21639.8-93

GOST 21639.8−93 Fluxes for electroslag remelting. Methods for determination of silicon dioxide

GOST 21639.8−93

Group B09

INTERSTATE STANDARD

Fluxes for electroslag remelting

METHODS FOR DETERMINATION OF SILICON DIOXIDE

Fluxes for electroslag remelting.
Methods for determination of silicon dioxide

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. 303 interstate standard GOST 21639.8−93 introduced directly as state standard of the Russian Federation from January 1, 1996

4 REPLACE GOST 21639.8−93*
________________
* Probably, the error of the original. Should read: GOST 21639.8−76. — Note the manufacturer’s database.

1 SCOPE

This standard specifies the photometric (with a mass fraction of silicon dioxide from 0.5 to 10%) and differential photometry (with a mass fraction of silicon dioxide from 10 to 25%) methods for determination of silicon dioxide in fluxes for electroslag remelting.

2 NORMATIVE REFERENCES

GOST 83−79 Sodium carbonate. Specifications

GOST 3118−77 hydrochloric Acid. Specifications

GOST 3652−69 citric Acid monohydrate and anhydrous. Specifications

GOST 3765−78 Ammonium phosphate disodium. Specifications

GOST 4332−76 Potassium carbonate — sodium carbonate. Specifications

GOST 9428−73 Silicon (IV) oxide. Specifications

GOST 9656−75 boric Acid. Specifications

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

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

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

3 GENERAL REQUIREMENTS

General requirements for methods of analysis GOST 21639.0.

4 PHOTOMETRIC METHOD

4.1 the essence of the method

The method is based on formation of yellow kremneftoristogo of heteroalicyclic followed by reduction a mixture of ascorbic and citric acid to molybdenum blue.

4.2 Equipment, reagents and solutions

Spectrophotometer or photoelectrocolorimeter.

Muffle furnace with temperature up to 1100 °C.

Hydrochloric acid according to GOST 3118, solution with a molar concentration of 3 mol/DM.

Ascorbic acid.

Citric acid monohydrate and anhydrous according to GOST 3652.

Boric acid according to GOST 9656.

Potassium carbonate — sodium carbonate according to GOST 4332.

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

Ammonium molybdate according to GOST 3765 (recrystallized according to GOST 21639.6), a solution with a mass concentration of 50 g/DM.

The recovery mixture, freshly prepared, 1 g of ascorbic and 5 g of citric acid dissolved in 100 cmof water.

Sodium carbonate according to GOST 83 and a solution with a mass concentration of 1 g/DM.

Silicon dioxide according to GOST 9428.

Standard solutions

Solution a: 0.2 g of calcined silicon dioxide is fused in a platinum crucible with 2.5 g of sodium carbonate at a temperature of 900−950 °C for 5−10 min and the melt leached with a sodium carbonate solution with a mass concentration of 1 g/DM. Then transferred to a volumetric flask with a capacity of 1 DM, made up to the mark with sodium carbonate solution and stirred.

The solution was stored in a plastic container.

The mass concentration of silica in solution is set by the gravimetric method: hydrochloric acid, sulfuric acid CHLOROSILANES or double evaporation.

Solution B: 10 cmsolution And transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with sodium carbonate solution with mass concentration of 1 g/land stirred.

Prepare before use.

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.

4.3 analysis

4.3.1 the Linkage of flux by mass specified in table 1 was placed in a platinum crucible, is mixed with 2.5 g of a mixture for melting, cover the crucible with a platinum lid, and melted in a muffle furnace at a temperature of 900−950 °C for 5−10 min.


Table 1 — the weight of the portion of the flux

The cooled crucible is placed in a plastic Cup, poured the hot solution of hydrochloric acid in accordance with the table. 10 cmof the solution Trilon B, heated to boiling, and heated in a water bath to dissolve the water. The crucible is removed from the beaker and washed with water. The contents of the beaker cooled, poured into a measuring flask with volume capacity specified in table 1, made up to the mark with water and mix.

Aliquot part of the solution is 5 cmis placed in a volumetric flask with a capacity of 100 cm, flow 50 cmwater, 5 cmof ammonium molybdate, and stirred for 10 min. pour 5 cmof restorative mixture was stirred.

The solution was topped to the mark with water and mix.

After 40 min, measure the optical density of the test solution on the spectrophotometer at a wavelength of 830 nm or photoelectrocolorimeter in the wavelength range from 640 to 900 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 find the mass of silicon dioxide in the calibration schedule.

4.3.2 Construction of calibration curve

For construction of calibration curve into nine volumetric flasks with a capacity of 100 cmis taken 1,0; 2,0; 3,0; 4,0; 5,0; 6,0; 7,0; 8,0 and 9.0 cmstandard solution B, which corresponds to 0,00002; 0,00004; 0,00006; 0,00008; 0,00010; 0,00012; 0,00014; 0,00016 and 0,00018 g of silicon dioxide. All flasks are poured at 1.6 cmof a hydrochloric acid solution, 50 cmwater, 5 cmof ammonium molybdate solution and mix. After 10 minutes, pour 5 cmrecovery mixture, made up to the mark with water and mix.

After 40 min, measure the optical density of the solution as specified in 4.3.1.

According to the obtained values of optical densities and corresponding mass of silicon dioxide build the calibration graph.

4.4 Processing of results

4.4.1 Mass fraction of silicon dioxide () in percent is calculated by the formula

, (1)

where is the mass of silica found by the calibration schedule g;

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

4.4.2 Standards of accuracy and standards for monitoring the accuracy of determining the mass fraction of silicon dioxide are shown in table 2


Table 2 — Standards accuracy control

5 THE METHOD OF DIFFERENTIAL PHOTOMETRY

5.1 the essence of the method

The essence of the method — 4.1.

5.2. Apparatus, reagents and solutions

Apparatus, reagents and solutions — for 4.2.

5.3 analysis

5.3.1. Analysis — 4.3.1 with the addition of: quality of solution comparison used a standard solution B.

5.3.2 Construction of calibration curve

To construct the calibration curve for the mass concentration of silicon dioxide from 10 to 18% in five out of six volumetric flasks with a capacity of 100 cmis taken 5,0; 6,0; 7,0; 8,0 and 9,0 cmstandard solution B, which corresponds to 0,00010; 0,00012; 0,00014; and 0,00018 0,00016 g of silicon dioxide. The sixth flask, which is taken 3.0 cmstandard solution B, is solution comparisons.

When the mass fraction of silicon dioxide from 18 to 25% in five out of six volumetric flasks with a capacity of 100 cmselect 9,0; 10,0; 11,0; 12,0, and 13,0 cmstandard solution B, which corresponds to 0,00018; 0,00020; 0,00022; and 0,00026 0,00024 g of silicon dioxide. The sixth flask, in which the selected 6.0 cmstandard solution B, is solution comparisons.

After 40 min, measure the optical density of the solution, as in 4.3.1.

According to the obtained values of optical densities and corresponding mass of silicon dioxide build the calibration graph.

5.4 processing of the results

5.4.1 Mass fraction of silicon dioxide () in percent is calculated by the formula

, (2)

where  — the amount of mass of silicon dioxide found on the calibration graph and entered in the reference solution, g;

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

5.4.2 Norms of accuracy and norms control the accuracy of determining the mass fraction of silicon dioxide are given in table 2.