GB/T 5687.6-1988 Chemical analysis methods for ferrochrome - Determination of carbon content by coulometric method GB/T5687.6-1988 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Methods far chemical analysis of ferrochromium
Coulometric method for the determination of carbon content
Methads far chemical analysis of ferrochromiumThe coulometric method for the determination of carbon content:This standard is applicable to the determination of carbon content in ferrochromium. Determination range: 0.010%～1.200%. UDC669.15'26
GB 5687.6: 88
This standard complies with the general provisions of GB1467-78 standard for chemical analysis of gold products. 1 Method summary
The sample is burned in the oxygen flow of a high-frequency induction heating furnace. The generated carbon oxide is absorbed by a known value of barium perchlorate solution. The generated perchloric acid changes the pH value of the solution. A pulse current of a certain amount of electricity is passed for electrolysis to restore the pH value of the solution to its original value. The carbon content in the sample is calculated based on the number of pulse electricity consumed in the electrolysis. 2 Reagents
2.1 Sodium carbonate: powder.
2.2 Degreased aluminum.
2.3 Glass wool.
2.4 Oxygen: purity greater than 99.5%,
2.5 Pure iron: carbon content less than 0.002%.
2.6 Tungsten particles: carbon content less than 0.002%, particle size 0.4~1,4 mm. 2.7 Potassium particles: carbon content less than 0.002%, particle size 0.4~0.8 mm. 2.8 Potassium dichromate and sulfuric acid (p1.84g/mL) solution, use it to check the solution. 2.9 Cathode cup solution: weigh 50g of crystalline barium perchlorate and dissolve it in 1000mL water, add 20mL isopropanol and mix well. 2.10 Anode cup solution: Weigh 50g of crystalline barium perchlorate and dissolve it in 250mL of water, mix well. 2.11 Reference electrode solution: Weigh 5g of crystalline barium perfluorate and 3g of sodium chloride and dissolve them in 100mL of water. After they are completely dissolved, add a few drops of 5% silver nitrate solution, heat to 60-70°C, cool and use the upper clarifier. 3 Apparatus
3.1 Coulometric carbon determination instrument (see the carbon determination gas path device diagram). Approved by the Ministry of Metallurgical Industry of the People's Republic of China on February 2, 1988 and implemented on March 1, 1989
GB 5687.688
Carbon determination instrument gas pedal device diagram
1—oxygen cylinder, 2. pressure reducing valve+3—flow ratio, 4—oxygen storage barrel, 5—gas washing bottle: 6—gas washing bottle, 7—gas washing bottle; 8—dry coal tower: 9—piston; 10—high-pressure induction heating expansion: 11—dust removal pipe: 12—desulfurization pipe: 15—four-way width; 16—diversion pump; 17—electromagnetic threshold+18—absorption cup, 13.19, 22—needle reading: 14, 20, 21—flow meter 3. 1. 1 Gas washing bottle (5): filled with sulfuric acid (p 1.84 / mL). 3.1.2 Gas washing bottle (6): filled with 40% potassium hydroxide solution. 3.1.3 Washing bottle (7): Contain potassium dichromate and sulfuric acid solution (2.8). 3.1.4 Drying tower (8): Contain sodium hydroxide. 3.1.5 Dust removal pipe (11): Contain absorbent cotton (2.2) and glass wool (2.3) 3.2 High frequency induction heating furnace: output power not less than 2kw. 3.3 Power supply regulator: 3kw.
3.4 ​​Oxygen cylinder: Equipped with a pressure valve with a flow meter, 3.5 Quality crucible; $×h, mm; 25×25, burn in a high temperature furnace above 1200C for 4h or burn with oxygen until the blank value is the lowest.
4 Sample
The sample should all pass through the 1.68 mm sieve. 5 Analysis stepsbzxz.net
5.1 Sample quantity
Weigh 0.5000g of sample.
5.2 Blank test
Carry out several blank tests with the sample and take the average value as the blank value. The blank value should be no more than 0.005% based on 0.500 0 8 samples.
5.3 Preparation before analysis
5.3.1 Add 90~100mL cathode cup solution (2.9) to the cathode cup. 5.3.2 First add powdered phosphoric acid (2.1) to the anode cup until half full, then pour the anode cup solution (2.10) into the glass and stir. After standing, the height of the precipitate should exceed the semipermeable membrane, and the platinum electrode should be completely immersed in the solution above the precipitate. 5.3.3 Add the reference electrode solution (2.11) to the reference electrode cup, and it should exceed the height of the semipermeable membrane. 5.3.4 Check the gas path. After confirming that there is no air leakage, perform multiple "end point positioning" according to the operation specified by the instrument, and select the pH value of the absorption liquid to be about 9.5.
GB 5687.6— 88
5.3.5 Use a standard sample with a carbon content close to that of the sample to be analyzed to determine the position of "electricity compensation" according to the analysis step 5.4. 5.4 Determination
5.4.1 Place the sample (5.1) in a quality crucible (3.5) and cover it with 2.0g pigeon pellets (2.6), 0.5g pure iron (2.5) and 1g tin pellets (2. 7).
5.4.2 After the instrument is normal, control the oxygen flow rate to 200~300mL/min, press the "electrolysis", "self-reset" switch, close the piston leading to the absorption cup, put down the furnace tube seal, put the quality on the support seat in the high-frequency induction heating furnace, push the furnace bolt seal, open the piston leading to the absorption cup, replace the air in the furnace, wait for the blank value to stabilize to the lowest value, press the high-voltage switch of the high-frequency induction furnace (start timing), the trial mixing starts to burn, the carbon dioxide is gradually absorbed by the absorption piece for electrolysis, put back the "convex reset" switch, when the high-frequency induction furnace plate current reaches the peak and lasts for 1 min, cut off the high-voltage switch, from the start of timing to the carbon dioxide is completely absorbed by the absorption liquid after about 1~6 minutes, read the pulse count, press the "white reset" switch, close the piston leading to the absorption cup, put down the protective tube seal bolt, and take out the quality. Calculation of analysis results
Calculate the carbon content according to the following formula:
Where:
C(%)- 0.5×10-(4-A2 ×100
A—-Pulse count of sample +
Pulse count of blank value;
m—Sample number:
0.5×10--
-Each pulse count is equivalent to the mass of carbon,B7 Allowable difference
The difference between the analysis results of the experimental results should not be greater than the allowable difference listed in the following table.%
Allowable difference
≥0.025-~0.070
>0.070~0.120
>0.120--0,400
20. 400--1.200
Additional remarks:
This standard was drafted by Gulin Ferroalloy Factory.
The main drafter of this standard is Liu Songshan.
From the date of implementation of this standard, the former Ministry of Metallurgical Industry Standard YB 584-65 "Method for Chemical Analysis of Ferrochromium" shall be used as the standard. The level mark of this standard is GB 567.6-881
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