This standard is applicable to the determination of carbon content in ferrochromium. Determination range: 4.00% to 10.50%. This standard complies with GB 1467-78 "General Principles and General Provisions of Chemical Analysis Methods for Metallurgical Products". GB/T 5687.7-1988 Chemical Analysis Method for Ferrochromium - Gravimetric Determination of Carbon Content GB/T5687.7-1988 Standard Download Decompression Password: www.bzxz.net

National Standard of the People's Republic of China
Methods for chemical analysis of ferrochromiumThe gravimetric method for the determinationof carbon contentbZxz.net
This standard is applicable to the determination of carbon content in ferrochromium. Determination range: 4.00%~~10.50%. UDC 669. 15'26
：543.062
GB 5687.7—88
This standard complies with GB1467—78 "General Principles and General Provisions of Standards for Chemical Analysis Methods of Metallurgical Products". 1 Summary of the method
The sample is burned at 12001350℃ in an oxygen flow, and carbon is oxidized to carbon dioxide, which is carried into the absorption bottle by oxygen and absorbed by alkali asbestos. The increase in alkali asbestos is measured, which is the amount of carbon dioxide generated, and then converted into carbon content. c + 0, → CO,
2NaOH + CO → Na,CO, + H,O
2Reagents
2.1Oxygen: purity greater than 99.5%.
2.2Magnesium perchlorate: anhydrous, granular.
2.3Flux: tin particles (0.4~0.8mm), copper wire, copper oxide, iron powder, vanadium pentoxide, etc. The carbon content in the flux should be less than 0.002%.
2.4Manganese dioxide: active, granular.
2.5Alkali asbestos.
2.6Sulfuric acid solution saturated with chromic acid: add potassium dichromate or chromic anhydride to sulfuric acid (o1.84g/mL) until saturated, and use the upper clarified solution.
Instruments and equipment
3.1The gravimetric carbon device is shown in Figure 1.
3.1.1 Oxygen cylinder (1): with pressure regulating valve. 3.1.2 Converter (3): with combustion tube containing platinum asbestos, the furnace temperature is maintained at 625℃. 3.1.3 U-shaped tube for drying and purifying oxygen (4): containing magnesium perchlorate (2.2) and alkali asbestos (2.5), separated by glass fiber. The diameter of the U-shaped tube is not less than 25mm and the height is not less than 100mm. 3.1.4 Tubular combustion furnace 5): the current can be adjusted to ensure the required temperature when burning the sample. 3.1.5 High temperature combustion tube (7): ×L, mm: 23~24×600. Approved by the Ministry of Metallurgical Industry of the People's Republic of China on February 2, 1988 and implemented on March 1, 1989
GB5687.7-88
Figure 1 Weight-based carbon determination device
1-Oxygen cylinder; 2-Mercury valve; 3-Converter; 4-U-shaped tube for drying and purifying oxygen; 5-Tube combustion furnace; 6-High temperature controller; --High temperature combustion tube; 8-Ceramic boat; 9-Palmet fiber; 10-Desulfurization bottle; 11-Drying tower; 12-Absorption bottle; 13-Absorption bottle (connected to 12 in the opposite direction); 14-Micro rotor flowmeter 3.1.6 Ceramic boat (8): 88mm or 97mm in length, should be pre-burned in a 1200℃ tube combustion furnace with oxygen until there is no carbon, or burned in a 1000℃ high temperature furnace for more than 4h, and after cooling, stored in an ungreased desiccator containing alkali asbestos or alkali lime and anhydrous calcium chloride.
3.1.7 Asbestos fiber (9): burn until no carbon is left. 3.1.8 Desulfurization bottle (10): filled with manganese dioxide (2.4). 3.1.9 Drying tower (11): filled with magnesium perchlorate (2.2). 3.1.10 Absorption bottle (12): used to absorb carbon dioxide. The bottom is evenly covered with glass fiber, and then covered with 10-15mm thick magnesium perchlorate (2.2), 3050mm thick alkali asbestos (2.5), and the top is covered with glass fiber. Oxygen is passed to constant weight under the same conditions as the test sample. The mass of the absorption bottle to be used should be less than 100 (see Figure 2). Asbestos,
Quartz fiber
Anhydrous magnesium perrhodate
4 Sample
GB 5687.7-88
Medium carbon ferrochrome samples should all pass through a 1.68mm sieve. 4.1
4.2 All high carbon ferrochrome samples should pass through a 0.125 mm sieve. 5 Analysis steps
5.1 Sample quantity
Weigh the sample and flux according to Table 1.
Carbon content, %
4. 000 ~~7. 000
7. 000~~8. 000
8. 00010. 500
5.2 Blank test
Carry out a blank test along with the sample.
5.3 Preparation before analysis
Sample amount·B
Amount of flux (optional), 8
Copper or copper oxide + iron powder
Vanadium pentahydride + iron powder
0. 5+1. 0
Connect the gravimetric carbon device, raise the furnace temperature to 1200-1350℃, check the airtightness of the instrument and the oxygen purification effect, and pass oxygen at a rate of 300-500mL/min. After 15-20 minutes, remove the absorption bottle (12), weigh it at room temperature, and put it back. 5.4 Determination
Place the sample (5.1) in a porcelain boat (8), cover it with flux according to Table 1, push the porcelain boat into the highest temperature of the high-temperature combustion tube, immediately plug the oxygen inlet, and after about 1 minute, pass oxygen at a rate of 300-500mL/min. After about 1 minute, when the combustion is finished, continue to pass oxygen for 15-20 minutes to completely remove carbon dioxide from the high-temperature combustion tube, desulfurization bottle and drying tower. Cut off the oxygen flow, close the weighed absorption bottle (12) and take out the porcelain boat, check the frit, and after confirming that the combustion is complete, remove the closed absorption bottle and weigh it at room temperature. The increase in the absorption bottle is the absorbed carbon dioxide. 6 Calculation
Calculate the percentage of carbon by the following formula:
c(%) = (m=m)×0. 2729 × 100m
Wherein: m:
mass of carbon dioxide measured by blank test, g; mass of carbon dioxide measured by combustion sample, g; m ——-sample volume, g;
0.2729——coefficient for converting carbon dioxide into carbon. 7 Allowable difference
The difference between the analysis results of laboratories should be less than the allowable difference listed in Table 2. 3.11
Additional remarks:
4. 00 10. 00
This standard was drafted by Xinyu Iron and Steel Plant.
The main drafters of this standard are Wu Taibai and Wang. GB 5687.788
Allowable Difference
From the date of implementation of this standard, the former Ministry of Metallurgical Industry Standard YB584--65 "Methods for Chemical Analysis of Ferrochromium" shall be invalid.
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