GB/T 5686.5-2023Ferromanganese,ferromanganese-silicon,nitrogen-bearing ferromanganese and manganese metal—Determination of carbon content—The Infrared absorption method,the gasometric method,the gravimetric method and the coulometric method (English PDF)

4.1 Principle

Burn the sample in a high-frequency induction furnace with an oxygen flow. The carbon is converted into carbon dioxide and carried to the infrared absorption cell along with the oxygen flow. The infrared detector measures its absorption of infrared rays of a specific wavelength.

4.2 Reagents and materials

4.2.1 Acetone. the carbon content (mass fraction) of the residue after evaporation shall be less than 0.000 5%.

4.2.2 Anhydrous magnesium perchlorate, granular.

4.2.3 Caustic soda asbestos, granular.

4.2.4 Glass wool.

4.2.5 Tungsten particles, carbon content (mass fraction) less than 0.000 5%, particle size 0.8 mm ~ 1.4 mm.

4.2.11 Crucible tongs or long-handled tweezers.

4.3 Instruments and apparatuses

4.3.1 High-frequency infrared carbon and sulfur analyzer or infrared absorption carbon analyzer 4.3.1.1 High frequency infrared carbon and sulfur analyzer or infrared absorption carbon analyzer (sensitivity is 0.000 1%). The device connection diagram is shown in.

4.3.2 Air source system

4.3.2.1 The carrier gas system includes an oxygen cylinder, a two-stage pressure regulator and a timing control section to ensure the provision of appropriate pressure and rated flow.

4.3.2.2 The power gas source system includes power gas (4.2.9), a two-stage pressure regulator and a timing control section to ensure the provision of appropriate pressure and rated flow.

4.3.3 High frequency induction furnace

The melting temperature requirements of the sample shall be met.

4.3.4 Control system. […]

4.4 Sample taking

Collect and prepare samples in accordance with the provisions of GB/T 4010. The ferromanganese-silicon samples shall pass through a 0.125 mm sieve hole; the nitrogen-bearing ferromanganese samples shall pass through a 0.149 mm sieve hole; the manganese metal samples shall pass through a 0.177 mm sieve hole.

4.5 Procedure

4.5.1 Number of determinations

Make at least 2 independent determinations on the same sample.

4.5.3 Blank test

4.5.3.1 Ferromanganese-silicon. Weigh 0.40 g of pure iron (4.2.7) and place it in a ceramic crucible (4.2.10) pre-filled with 0.30 g of tin particles (4.2.6); cover it with 1.80 g of tungsten particles (4.2.5); measure according to 4.5.5. Repeat enough times; record the smallest and relatively stable three readings; calculate the average value and input it into the instrument. When measuring the sample, the instrument will automatically deduct the blank value.

4.5.4 Analysis preparation

4.5.5 Test calibration

4.5.6 Determination

4.5.6.1 According to the type and carbon content range of the sample to be tested, respectively select the best analytical conditions of the instrument, such as the combustion integration time of the instrument, the setting of the comparison level (or set number), etc.

4.6 Expression of analysis results

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

4.7 Precision

The precision data of this document was determined in 2022 by nine laboratories which conducted joint tests on the carbon content in ferromanganese-silicon, ferromanganese, nitrogen-bearing ferromanganese and manganese metal of eight different levels. Each laboratory independently tested the sulfur content at each level three times (see Appendix B for the original data of the precision test) according to the statical methods in GB/T 6379.1 and GB/T 6379.2. The precision determined is shown in Table 2.

5.1 Principle

Preheat the sample in a tubular combustion furnace and burn with oxygen. Collect the generated carbon dioxide and other mixed gases in a gas measuring tube after desulfurization; then, use potassium hydroxide solution to collect the carbon dioxide, and measure the volume of the remaining gas. The difference in volume before and after absorption is the volume of carbon dioxide, which is then converted into carbon content.

5.2 Reagents and materials

5.2.10 Potassium hydroxide solution, 400 g/L.

5.2.11 Sodium chloride solution, 260 g/L. Use methyl red solution as the indicator, and add sulfuric acid solution (1+1) dropwise until it becomes acidic.

5.2.12 Oxygen, purity greater than 99.5%.

5.3 Instruments and apparatuses

5.3.1 Carbon meter using gasometric method

5.3.1.1 The carbon meter using gasometric method is shown in Figure 2.

5.3.1.2 Gas washing bottle, filled with sulfuric acid solution saturated with chromic acid (5.2.9).

5.3.1.3 Gas washing bottle, filled with soda lime or sodium hydroxide (5.2.3).

5.3.1.4 Drying tower, filled with activated alumina (5.2.4).

5.3.1.5 High temperature combustion tube, (23 mm ~ 24 mm) × 600 mm.

5.3.1.6 Tubular combustion furnace, adjustable current to ensure the required, temperature for burning the sample.

5.3.1.7 Asbestos fiber (5.2.2), burned until no carbon is left.

5.3.1.8 Desulfurization tube, filled with active manganese dioxide (5.2.5).

5.3.1.11 Absorber, containing potassium hydroxide solution (5.2.10)

5.3.1.12 Small piston, one side ventilated to the atmosphere.

5.3.2 Long hook

Made of low carbon nickel-chromium wire or heat-resistant alloy wire.

5.4 Sample taking

Collect and prepare samples in accordance with the provisions of GB/T 4010.

Ferromanganese-silicon and ferromanganese with medium and high carbon content shall all pass through the 0.125 mm sieve hole; ferromanganese with low carbon content shall all pass through the 0.149 mm sieve hole.

5.5 Procedure

5.5.1 Number of determinations

Make at least 2 independent determinations on the same sample.

6.1 Principle

Burn the sample in an oxygen flow at 1 200 °C ~ 1 350 °C. The generated carbon dioxide is carried into the absorption bottle by oxygen and absorbed by the caustic soda asbestos. Measure the weight gain of the caustic soda asbestos, which is the content of carbon dioxide generated; then, convert into carbon content. The main reaction formula is as follows. […]

6.2 Reagents and materials

6.2.8 Sulfuric acid solution saturated with chromic acid. Add potassium dichromate or chromic anhydride to sulfuric acid (6.2.7) until it is saturated and use the above-part clear solution.

6.3 Instruments and apparatuses

6.3.1 Carbon meter using gravimetric method

6.3.1.2 Oxygen cylinder, provided with pressure regulating valve.

6.3.1.3 Reforming furnace, equipped with a combustion tube filled with platinum asbestos, the furnace temperature is maintained at 625 °C.

6.3.1.4 U-shaped tube for drying and purifying oxides (see 4 in Figure 3), filled with anhydrous magnesium perchlorate (6.2.2) and caustic soda asbestos (6.2.5) and is separated by glass fiber. The diameter of the U-shaped tube is not less than 25 mm and the height is not less than 100 mm.

6.3.1.5 Tubular combustion furnace, adjustable current to ensure the required, temperature for burning the sample.

6.3.1.6 High temperature combustion tube, (23 mm ~ 24 mm) × 600 mm.

6.3.1.7 Porcelain boat, 88 mm or 97 mm in length, shall be preliminarily burned in a […]

6.4 Sample taking

Collect and prepare samples in accordance with the provisions of GB/T 4010. The samples shall pass through a 0.149 mm sieve.

6.5 Procedure

6.5.1 Number of determinations

Make at least 2 independent determinations on the same sample.

6.5.2 Sample mass

Weigh the sample and flux according to Table 5, with the sample accurate to 0.000 1 g and the flux accurate to 0.01 g.

6.5.3 Blank test

Carry out a blank test along with the sample.

6.5.4 Analysis preparation

Connect the carbon meter using gravimetric method; raise the furnace temperature to 1 200 °C ~ 1 350 °C; check the airtightness of the instrument and the oxygen purification effect; introduce oxygen at a rate of 300 mL/min ~ 500 mL/min. After 15 min ~ 20 min, remove the absorption bottle (see 12 in Figure 3); weigh it at room temperature; put it back.

6.5.6 Result calculation

Calculate the carbon content in the sample according to Formula (3).

7.1 Principle

Burn the sample in the oxygen flow of a high-frequency induction heating furnace. The generated carbon dioxide is absorbed by a barium perchlorate solution with a known pH value. The generated perchloric acid changes the pH value of the solution. Pass a pulse current of a certain amount of electricity through the solution for electrolysis to restore the pH value of the solution to its original value. Calculate the carbon content in the sample based on the pulse electricity consumed in the electrolysis.

7.2 Reagents and materials

7.2.1 Barium carbonate, powder.

7.2.2 Cotton wool.

7.2.3 Glass wool.

7.2.4 Sodium hydroxide.

7.3 Instruments and apparatuses

7.3.1 Carbon meter using coulometric method

7.3.1.1 The carbon meter using coulometric method is shown in Figure 5.

7.3.1.2 Gas washing bottle (see 5 in Figure 5), containing sulfuric acid (rho = 1.84 g/mL).

7.3.1.3 Gas washing bottle (see 6 in Figure 5), containing potassium hydroxide solution (400 g/L).

7.3.1.4 Gas washing bottle (see 7 in Figure 5), containing potassium dichromate saturated sulfuric acid solution (7.2.9).

7.3.2 High frequency induction heating furnace

The output power is not less than 2 kW.

7.3.3 Power regulator

The power is 3 kW.

7.3.4 Oxygen cylinder

Equipped with a pressure reducing valve with flow meter.

7.3.5 Crucible

The size is phi25 mm × 25 mm, and it is burned in a high-temperature heating furnace above 1 200 °C for 4 h or burned with oxygen until the blank value is the lowest.

7.4 Sample taking

Collect and prepare samples in accordance with the provisions of GB/T 4010. The samples shall all pass through a 0.177 mm sieve.

7.5 Procedure

7.5.1 Number of determinations

Make at least 2 independent determinations on the same sample.

7.5.2 Sample mass

Weigh 0.500 g of sample, accurate to 0.000 1 g.

7.5.3 Blank test

Carry out blank tests several times with the sample and take the average value as the blank value. The blank value calculated based on 0.50 g sample shall not be greater than 0.005%.

7.5.4 Analysis preparation

7.5.5 Determination

Place the sample (see 7.5.2) in a crucible (7.3.5) and cover it with 1.5 g of tungsten granules (7.2.6), 0.3 g of pure iron (7.2.8) and 0.3 g ~ 0.5 g of tin granules (7.2.7).

After the instrument is normal, control the oxygen flow rate to 200 mL/min ~ 300 mL/min; press the "electrolysis" and "self-reset" switches; close the piston leading to the absorption cup; put down the furnace tube sealing bolt support; place the crucible (7.3.5) on the support seat inside the high-frequency induction heating furnace (7.3.2);