This standard applies to the determination of free carbon content in carbides of tungsten, titanium, niobium, tantalum, molybdenum, zirconium, hafnium and vanadium, mixed powders of these carbides and binder metals (without lubricants and binders), and pre-sintered or sintered cemented carbides of all grades produced from these carbon-based materials. Determination range: 0.02-0.50%. This standard complies with GB 1467-78 "General Principles and General Provisions for Chemical Analysis Methods of Metallurgical Products". This standard is equivalent to the international standard ISO 3908-1976 "Cemented Carbide-Determination of Insoluble (Free) Carbon-Gravimetric Method". GB/T 5124.2-1985 Chemical Analysis Method for Cemented Carbide-Determination of Free (Insoluble) Carbon Content by Gravimetric Method GB/T5124.2-1985 Standard Download Decompression Password: www.bzxz.net

National Standard of the People's Republic of China
Chemical analysis methods of hardmetals
Gravimetric method for the determinationof free(insoluble)carboncontentUDC 669.018.25
: 543.21: 546
GB 5124.2-85
This standard is applicable to the determination of free carbon in carbides of tungsten, titanium, molybdenum, aluminum, zirconium, hafnium and vanadium, mixed powders of these carbides and binder metals (without lubricants and binders), and pre-sintered or sintered hardmetals of all grades produced from these carbides. Determination range: 0.02～0.50%.
This standard complies with GB1467-78 "General Principles and General Provisions of Standards for Chemical Analysis Methods of Metallurgical Products". This standard is equivalent to the international standard IS03908-1976 "Cemented Carbide-Determination of Insoluble (Free) Carbon-Gravimetric Method". 1 Method Summary
Use hydrofluoric acid and nitric acid to decompose carbides and determine the amount of free carbon by weight. 2 Reagents and Materials
2.1 Nitric acid (2+3).
2.2 Hydrofluoric acid (specific gravity 1.12).
2.3 Acid-washed asbestos, burn at 800-1000℃ for at least 3h under strong oxidizing conditions before use, and then place in a desiccator for standby use. 3 Instruments
3.1 Platinum dish: 200ml.
3.2 Platinum Gooch crucible (or porcelain Gooch crucible or ceramic filter instead of Gooch crucible and asbestos pad). 3.3 Vacuum filtration device.
3.4 ​​Other instruments: Refer to the instruments specified in GB5124.1-85 "Chemical analysis method of cemented carbide - gravimetric determination of total carbon content".
4 Sample
In a mortar that will not change the sample composition, grind the laboratory sample into a powder that passes through a 0.18mm sieve. 5 Analysis steps
5.1 Safety measures
Asbestos can endanger human health and should not be inhaled. To avoid its dispersion, all operations using asbestos should be carried out in a well-ventilated area. Hydrofluoric acid and nitric acid are highly corrosive and must be avoided from contact or inhalation of their vapors. All operations using these acids should be carried out in a well-ventilated fume hood.
5.2 Determination of quantity
Instructions for use: The international standard is lubricant-free. Issued by the National Bureau of Standards on April 24, 1985
Implemented on February 1, 1986
GB 5124. 2—85
Two or three samples should be weighed for determination during analysis. 5.3 Sample volume
Weigh 2.50 g of sample.
5.4 Blank test
Two blanks should be made for each group of determination.
Prepare the Gooch crucible according to 5.5.2.
Put 75 ml of nitric acid (2.1) and 10 ml of hydrofluoric acid (2.2) in platinum blood (3.1) and mix well. The following shall be carried out according to 5.5.3 to 5.5.4. Www.bzxZ.net
5.5 Determination
5.5.1 Place the sample (5.3) in a platinum dish (3.1), add 75 ml of nitric acid (2.1), place the platinum on a steam bath and heat for 5 min, add 10 ml of hydrofluoric acid (2.2), and continue heating on the steam bath for 1 h until the sample is completely dissolved. Remove the platinum III and cool to room temperature. 5.5.2 Weigh a sufficient amount of acid-washed asbestos (2.3) to fill it to a depth of about 8 to 10 mm in the Gooch crucible. With the help of suction filtration, wet the sub-compacted asbestos pad with water so that it will not penetrate during filtration and the speed will not be too slow. Filter 20 to 30 ml of water and check whether the asbestos is evenly distributed. 5.5.3 Filter the contents of platinum III through the asbestos pad. Rinse the platinum III twice with a small amount of water and use about 0.5 g of acid-washed asbestos (2.3) to remove the free carbon attached to the platinum dish. Transfer the asbestos to the crucible and rinse the platinum III with water at least twice. Then wash the asbestos pad with hot water until it is acid-free and filter dry. Transfer the wet asbestos pad to a boat and dry at 110°C. 5.5.4 Asbestos pad obtained by burning in an oxygen stream according to GB5124.1-85 (5.5.3). The temperature in the combustion tube is about 1200°C. Calculation of analysis results
Calculate the percentage of free carbon according to the following formula: C (%) = 0.2729 ×
Where: m1—the amount of carbon dioxide measured in the blank test, g, m2
the amount of carbon dioxide measured in the combustion sample, g
-the amount of sample, g,
0.2729---the conversion factor for converting carbon dioxide to carbon. 7 Allowable difference
(mz - m)
The extreme difference of one or three independent measurement results shall not be greater than the allowable difference listed in the following table:%
Free carbon content
0.02~0.10
>0.10~0.50
Allowable difference of two independent measurement results
The arithmetic mean of the qualified measurement values ​​shall be the final result. Additional remarks:
This standard was proposed by China Nonferrous Metals Industry Corporation. This standard was drafted by Zhuzhou Cemented Carbide Factory. The main drafters of this standard were Wang Jishen and Lan Xingji. Allowable difference of three independent measurement results
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