This standard specifies the method for determining the amount of free carbon in silver tungsten carbide electrical contact materials. This standard is applicable to the determination of the amount of free carbon in silver tungsten carbide electrical contact materials. Determination range: 2.00% to 5.00%. JB/T 7778.4-1995 Chemical analysis method for silver tungsten carbide electrical contact materials JB/T7778.4-1995 Standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
Chemical analysis method of silver tungsten carbide electric contact material Acid separation-gas volumetric method for determination of free carbon content Subject content and scope of application
This standard specifies the method for determination of free carbon content in silver tungsten carbide electric contact material. JB/T 7778. 4—1995Www.bzxZ.net
This standard is applicable to the determination of free carbon content in silver tungsten carbide electric contact material. Determination range: 2.00%~5.00%. 2 Reference standards
GB 223. 1--81
JB 4107.1--85
JB/T 7778. 3-1995
3 Principle of the method
Determination of carbon content in steel and alloys
General principles and general provisions for chemical analysis methods of electrical contact materials Chemical analysis methods of silver tungsten carbide electrical contact materials·Gas volumetric method for determination of total carbon content The sample is dissolved in phosphoric acid and nitric acid. Combined carbon and metal elements are dissolved in the acid, while free carbon is insoluble. Free carbon is separated by filtration with acid-washed asbestos, dried, and its free carbon content is determined by gas volumetric method. 4 Reagents and instruments
4.1 Phosphoric acid (p 1.69 g/mL).
4.2 Nitric acid (1+1).
4.3 Acid-washed asbestos: Treated at 1000℃ for 1h, put into a triangular flask and soaked with water for later use. 4.4 Water filtration device: as shown below:
1-water filter; 2-filtration bottle, 3-Goowell glass funnel; 4-plastic sieve plate, 5-rubber stopper, 6-hard rubber tube. 4.5 Instrument: Same as Chapter 5 of JB/T7778.3. 5 Analysis steps
5.1 Test materials
Approved by the Ministry of Machinery Industry on October 9, 1995
Implementation on January 1, 1996
Weigh the test materials according to Table 1, accurate to 0.0001g. Free carbon content
2.00~3.00
>3. 00~5. 00
5.2 Blank test
Carry out a blank test with the sample.
5.3 Determination
JB/T 7778. 4--1995
5.3.1 Place the sample in a 100mL beaker, add 2mL phosphoric acid (4.1) and 10mL nitric acid (4.2), heat and dissolve on a low-temperature electric furnace, and boil to drive off nitrogen oxides. Remove and cool. 5.3.2 Pour the acid-washed asbestos (4.3) into the funnel, and then use a glass rod to press the acid-washed asbestos tightly to make the asbestos layer uniform and dense, about 3mm thick. 5.3.3 Carefully pour the sample solution (5.3.1) into the funnel and filter it. Wash all the residue in the beaker into the funnel with hot water. Wash the funnel several times with hot water.
5.3.4 Stop filtering, remove the funnel, push out the plastic sieve plate with a glass rod, carefully remove the asbestos layer, and put it into the porcelain boat. 5.3.5 Put the porcelain boat into the oven and bake it at 120℃ for 2h and then take it out. 5.3.6 Raise the furnace temperature to 1050℃, first calibrate the instrument with the standard sample, and perform the following operations according to Article 6.4 of JB/T7778.3. 6 Calculation of analysis results
The percentage of free carbon is calculated according to formula (1): (Ci-C) K
Wherein: Ci—reading when burning the sample, %; Co—reading of the blank test, %,
K—temperature and pressure correction coefficient [see Appendix of GB223.1]; m-mass of the sample, g.
7 Allowable difference
The difference in analysis results between laboratories should not be greater than the allowable difference listed in Table 2. Table 2
Free carbon content
2.00~3.00
>3.00~5.00
Additional instructions:
This standard was proposed and managed by the Guilin Electric Science Research Institute of the Ministry of Machinery Industry. X100
This standard was drafted by the Guilin Electric Science Research Institute of the Ministry of Machinery Industry, and Shanghai Alloy Material General Factory participated in the drafting. The main drafters of this standard are Tang Yuelin, Li Yongkang, Ling Xiangqun68
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.