GB/T 3518-2023Flake graphite (English PDF)

3.1 Flake graphite

Natural crystalline graphite that is shaped like fish scales, belongs to the hexagonal crystal system, and has a layered structure.

NOTE: it is equivalent to crystalline graphite in geological exploration. […]

6.1 Fixed Carbon Content, Volatile Matter, Moisture, Iron Content and Sulfur Content

The determination of fixed carbon content, volatile matter, moisture, iron content and sulfur content of flake graphite shall comply with the stipulations of GB/T 3521.

6.2 Weight of Screen Residue

The determination of the weight of screen residue of flake graphite shall comply with the stipulations of GB/T 3520.

6.3 Artificially Recreated Flake Graphite

6.3.1 Method and principle

The particle size of natural flake graphite that has been ultrasonically treated in water or sulfuric acid solution will not change, but the particle size of artificially recreated flake graphite will change. Through this principle, it can be identified whether natural flake graphite contains artificially recreated flake graphite.

6.3.2 Reagents and materials

6.3.2.1 Water: not lower than the requirements of Grade-3 water specified in GB/T 6682.

6.3.2.2 Concentrated sulfuric acid: with a density of 1.84 g/cm³.

6.3.2.3 Rapid qualitative filter paper.

6.3.3 Instruments and equipment

6.3.3.1 Balance: with an accuracy of not lower than 0.01 g.

6.3.3.2 Electric drying oven: temperature measurement range: from room temperature to 300 °C, with a temperature control accuracy of ± 2 °C.

6.3.3.3 Stopwatch.

6.3.3.4 Standard sieve: mesh size and metal wire diameter shall comply with the stipulations of GB/T 6003.1.

6.3.3.5 Vibrating sieving machine: complies with the requirements of DZ/T 0118.

6.3.3.6 Ultrasonic cleaning machine for laboratory use.

6.3.3.7 Centrifuge: with a rotation speed of 10,000 r/min ~ 30,000 r/min, and a centrifuge tube volume of 250 mL.

6.3.4 Test steps

6.3.4.1 Specimen collection

In accordance with the stipulations of GB/T 6679, take 1 kg of specimen, then, use the quartering method to divide it to 1,000 g. Use the dichotomy to divide the 1,000 g of specimen obtained through division into 2 specimens, one for specimen screening before the treatment, and one for specimen screening after the treatment.

6.3.4.2 Weight of screen residue before treatment

6.3.4.2.1 Weigh-take 50.00 g (accurate to 0.01 g) of specimen with moisture (mass fraction) less than 1% and record it as m. Pour it into the standard sieve with a sieve bottom, put on the sieve cover, and use a vibrating sieving machine for sieving (the sieving time is determined in accordance with the mesh size of the standard sieve, for standard sieves with a mesh size greater than 75 µm, perform sieving for 10 minutes; for standard sieves with a mesh size between 75 µm and 45 µm, perform sieving for 20 minutes).

6.3.4.2.2 Repeatedly perform sieving. After reaching the end of filter, stop the machine and weigh the mass (m1) of the screen residue before the treatment.

6.3.4.3 Screening residue after treatment

6.3.4.3.1 Weigh 2 portions of 80.00g (accurate to 0.01g) of the sample with moisture (mass fraction) less than 1%, pour them into 400mL beakers, add 100mL of concentrated sulfuric acid, stir evenly, and ultrasonicate on the ultrasonic cleaner for 10 minutes. Transfer it into a 250mL centrifuge tube, and centrifuge for 5 minutes at a centrifuge speed of 15000r/min. Pour the reacted sulfuric acid into a waste acid bucket. Transfer the graphite in the centrifuge tube into a 400mL beaker, and wash it with grade-3 water until the pH value of the solution is 5~6, filter with rapid qualitative filter paper, then place it in an electric drying oven at 105°C ~ 110°C for 3 hours.

6.3.4.3.2 Weigh 50.00g (accurate to 0.01g) from the two samples treated according to 6.3.4.3.1, record it as m3. Pour into the standard sieve with a sieve bottom, cover the sieve cover and use a vibrating sieve machine to sieve (the sieving time is determined according to the sieve size of the standard sieve -- 10 minutes for standard sieves larger than 75µm, 20 minutes for […]

6.3.5

X3---the difference of the weight of screen residue before and after the treatment.

X1---the weight of screen residue before the treatment.

X2---the weight of screen residue after the treatment.

6.3.6 Result expression

If the difference of the weight of screen residue before and after the treatment (X3) is greater than 5.0%, then, it shall be determined that the natural flake graphite contains artificially recreated flake graphite; if the difference of the weight of screen residue before and after the treatment (X3) is less than or equal to 5.0%, then, it shall be determined that the natural flake graphite does not contain artificially recreated flake graphite.

7.1 Classification of Inspection

7.1.1 Exit-factory inspection

The exit-factory inspection items of flake graphite are volatile matter, moisture, weight of screen residue and artificially recreated flake graphite.

7.1.2 Type inspection

The type inspection items of flake graphite are all items specified in Chapter 5. Under one of the following circumstances, type inspection shall be carried out:

a) When new products are put into production or product finalization is conducted;

b) During normal production, once a year;

c) When there are major changes in raw materials, production processes and equipment, etc., which may affect product quality;

d) When production has been suspended for more than one year and resumed;

e) When the exit-factory inspection results are significantly different from the previous type inspection results.

7.2 Principle of Batch Formation

60 t of bagged or barreled flake graphite stably and continuously produced with the same batch of raw materials and the same process shall be counted as one batch. When it is less than 60 t, it shall still be counted as one batch.

7.3 Sampling Method

The sampling method shall comply with the stipulations of GB/T 6679. The sampling size of each batch shall not be less than 1 kg.

7.4 Determination Rules

7.4.1 When the various product characteristic indicators comply with the requirements of Chapter 5, the batch of products shall be determined as qualified.

7.4.2 When a certain indicator of the product does not comply with the requirements of Chapter 5, double sampling shall be carried out for a re-inspection of the disqualified item. If the re-inspection results comply with the requirements of Chapter 5, the batch of products shall still be determined as qualified; if any item in the re-inspection results fails to comply with the requirements of Chapter 5, then, the batch of products shall be determined as disqualified.

8.1 Marking

The packaging bag of flake graphite shall be marked with product name, label, net content, production enterprise's name and address, and rain and moisture-proof signs.

Each batch of products shall be accompanied by a product certificate. The product certificate shall include product label, product batch No. inspection date, inspection conclusion, production enterprise's name and address, and shall also be stamped with the inspection seal of the production enterprise's inspection department and the seal of the inspection personnel.

8.2 Packaging

Flake graphite shall be packed in inner-coated woven bags, with a net content of (25 ± 0.25) kg per bag. Special packaging shall be determined by the supply-side and demand-side through negotiation.

8.3 Transportation

Product transportation shall be equipped with facilities to prevent the product from rain, moisture, exposure to the sun, damage and contamination.

8.4 Storage

The product shall be stored in a cool, ventilated and dry place, and facilities shall be provided to prevent the product from exposure to the sun, rain, moisture and contamination. […]