GB/T 5686.7-2022Ferromanganese，ferromanganese-silicon，nitrogen-bearing ferromanganese and manganese metal—Determination of sulfur content—Infrared absorption method and combustion-neutralization method (English PDF)

4.1 Principle

The test portion is burned in a high-frequency induction furnace with oxygen flow, and the sulfur is oxidized into sulfur dioxide, which is carried to the infrared absorption cell with the oxygen flow.

4.2 Reagents and Materials

4.2.1 Acetone, the residue after evaporation contains less than 0.0005% sulfur.

4.2.2 Magnesium perchlorate, anhydrous, granular.

4.2.3 Caustic soda asbestos, granular.

4.2.4 Glass wool.

4.2.5 Tungsten particles, with sulfur content less than 0.0005% and a particle size 0.8 mm ~ 1.4 mm.

4.3 Instruments and Equipment

4.3.1 High-frequency infrared carbon and sulfur analyzer or infrared absorption sulfur analyzer.

4.3.2 Gas source

4.3.2.1 The carrier gas system includes an oxygen container, a two-stage pressure regulator and a timing control part that ensures appropriate pressure and rated flow.

4.3.2.2 The power gas source system includes power gas (see 4.2.8), a two-stage pressure regulator and a timing control part that ensures appropriate pressure and rated flow.

4.3.3 High-frequency induction furnace

It shall satisfy the requirements for the melting temperature of the test portion.

4.3.4 Control System.

4.4 Sampling and Specimen Preparation

In accordance with the stipulations of GB/T 4010, take and prepare specimens. The ferromanganese-silicon specimens shall pass a 0.125 mm sieve, the ferromanganese and nitrogen-bearing ferromanganese specimens shall pass a 0.149 mm sieve, and the manganese metal specimens shall pass a 0.177 mm sieve.

4.5 Analytical Procedures

4.5.1 Number of determinations

For the same specimen, carry out at least 2 independent determinations.

4.5.2 Amount of test portion

The amount of test portion is weighed in accordance with Table 1 and the category of the specimen to be tested, accurate to 0.001 g.

4.5.3 Blank test

Weigh-take 1.80 g of tungsten particles (see 4.2.5) and place them in a crucible (see 4.3.6) containing 0.30 g of tin particles (see 4.2.6) in advance and determine in accordance with 4.5.5.

Repeat enough times, record the smallest, relatively stable and consistent 3 readings, calculate the average value and enter it into the instrument. When determining the specimens, the instrument will automatically deduct the blank value.

4.5.4 Analysis preparation

4.5.5 Calibration test

4.6 Expression of Analysis Results

If the absolute value of the difference between two independent analysis results of the same specimen is not greater than the repeatability limit r, then, take the arithmetic mean as the analysis result.

4.7 Precision

The precision data of this Part was determined by 10 laboratories conducting joint tests on the sulfur content in 8 different levels of ferromanganese, ferromanganese-silicon, nitrogen-bearing ferromanganese and manganese metal from November to December 2020.Each laboratory independently tested the sulfur content of each level 3 times (see Table B.1 in Appendix B for the original data of the precision test). In accordance with the statistical methods of GB/T 6379.1 and GB/T 6379.2, the precision determined is shown in Table 2.

5.1 Principle

The test portion is burned with oxygen at high temperature to oxidize all the sulfur into sulfur dioxide, which is absorbed into the hydrogen peroxide solution and turned into sulfuric acid, which is titrated with sodium hydroxide standard solution. Calculate the sulfur content.

5.2.4 Soda lime or sodium hydroxide, granular

5.3 Instruments and Equipment

5.3.1 Sulfur analyzer. Its device connection is shown in Figure 2.

5.3.2 Absorption bottle, see Figure 3.

5.4 Sampling and Specimen Preparation

In accordance with the stipulations of GB/T 4010, take and prepare specimens. The ferromanganese-silicon specimens shall pass a 0.125 mm sieve, the ferromanganese and nitrogen-bearing ferromanganese specimens shall pass a 0.149 mm sieve, and the manganese metal specimens shall pass a 0.177 mm sieve.

5.5 Analytical Procedures

5.5.1 Number of determinations

For the same specimen, carry out at least 2 independent determinations.

5.5.4 Analysis preparation

5.5.4.2 Transfer-take 40 mL of the absorption solution (see 5.2.6) into the absorption bottle (see 16 in Figure 2), add 5 drops of mixed indicator (see 5.2.7). At a flow rate of 700 mL/min ~ 900 mL/min, introduce oxygen for about 5 minutes, so as to drive out the carbon dioxide in the solution. At this time, if the solution turns red purple, then, dropwise add the sodium hydroxide standard titration solution (see 5.2.10), until the solution turns bright green.

5.5.5 Determination

5.5.5.1 Place the test specimen (see 5.5.2) in the porcelain boat (see 5.3.4), push it into the […]

5.6 Allowable Differences

The differences in the analysis results among laboratories shall not be greater than the allowable differences listed in Table 4 (see Table B.2 in Appendix B for raw test data).