GB/T 20168-2017Rapidly-quenched neodymium iron boron permanent magnetic powder (English PDF)

3.1 Principal magnetic properties

Include the residual magnetic induction intensity (Br), intrinsic coercive force (HcJ), magnetic induction intensity coercive force (HcB) and maximum magnetic energy product [(BH)max] of permanent magnetic materials.

3.2 Additional magnetic properties

Include the residual magnetic induction intensity temperature coefficient [alpha(Br)], intrinsic coercive force temperature coefficient [alpha(HcJ)], Curie temperature (Tc), magnetization saturation trend of residual magnetic induction intensity and intrinsic coercive force of permanent magnetic materials.

3.3 Rapid quenching magnetic powder

Rapidly solidifying magnetic powder produced through the rapid quenching process, with a microcrystalline structure.

Please refer to Appendix A for the preparation process and chemical composition ratio of rapidly-quenched neodymium iron boron permanent magnetic powder.

4.1 Classification

In accordance with the intrinsic coercive force, rapidly-quenched neodymium iron boron permanent magnetic powder is classified into three categories of products: low coercive force L, medium coercive force M and high coercive force H.

4.2 Designations

In accordance with the maximum magnetic energy product, each category of products is divided into several designations. The expression method for the designations shall comply with the provisions of GB/T 17803.

4.3 Designation Expression Method

5.4 Additional Magnetic Properties and Other Physical and Chemical Properties

The additional magnetic properties and other physical and chemical properties of the product are shown in Appendix C. If the demand-side has special requirements, the supply-side and the demand-side may negotiate separately.

6.1 Principal magnetic properties

6.1.1 The principal magnetic properties of the product are tested using a vibrating sample magnetometer that satisfies the accuracy requirements. Please refer to Appendix D for the test method.

6.1.2 Upon agreement between the supply-side and the demand-side, the magnetic powder may also be made into magnets for testing. The requirements for magnetic test samples are: the bonder mass fraction is 2.5%, the density (rho) is 6.00 g/cm³ ± 0.05 g/cm³, the size is phi 10 mm x 10 mm; the test method shall comply with the provisions of GB/T 3217; the numerical rounding of the magnetic properties test results shall be carried out in accordance with the provisions of GB/T 8170. The principal magnetic property values of the test samples with corresponding magnet designations of the magnetic power are shown in Appendix E.

6.2 Particle Size

The test method for the particle size of the product shall comply with the provisions of GB/T 1480.

6.3 Appearance Quality

The appearance quality of the product is visually inspected using a 10x magnifying glass.

7.1 Inspection and Acceptance

7.1.1 The product shall be inspected by the supply-side's quality and technical supervision department to ensure that the product quality complies with the provisions of this Standard. In addition, a quality certificate shall be filled out.

7.1.2 The demand-side may inspect the received products in accordance with the provisions of this Standard. If the inspection results are inconsistent with the provisions of this Standard, the demand-side shall submit in writing to the supply-side within 1 month from the date of receipt of the products, and the supply-side and the demand-side shall negotiate and resolve this problem. If no quality objection is raised for more than 1 month, then, it will be deemed that […]

D.1 Sample Preparation Method and Test Procedures

D.1.1 Use an electronic balance with an accuracy of 0.1 mg to weigh the mass of the specimen tube (mtube) of the magnetic powder to be tested.

D.1.2 Put an appropriate amount of magnetic powder into the specimen tube and compact it. It is required that the surface shall be flattened. Then, weigh them together. Measure the sum of the mass of the magnetic powder and the mass of the specimen tube (mtube + powder). In accordance with the mass of the specimen tube (mtube), and the sum of the mass of the magnetic powder and the mass of the specimen tube (mtube + powder), calculate the mass of the magnetic powder (mpowder).

D.1.3 Drop 502 glue into the specimen tube containing the magnetic powder, so as to solidify the magnetic powder. Then, put the specimen tube into the sample pressing machine and press the sealing copper sheet into the end face of the specimen tube in parallel, so as to prevent the magnetic powder from rotating with the magnetic field during measurement.

D.1.4 After the magnetic powder is dried and solidified, put the specimen tube into the magnetizer and magnetize it along the axial direction with a pulse magnetic field of µ0H ~ 4.5 T.

D.1.5 Place the specimen tube on the vibrating sample magnetometer measurement bracket. The magnetization direction is consistent with the direction of the measuring magnetic field. Enter the type of specimen, and the mass of the magnetic powder (mpowder), the density of the magnetic powder (rho) and the demagnetization factor (N) for the demagnetization curve measurement.

D.2 Determination of Demagnetization Factor N

In accordance with the diameter (D) and length (L) of the sample, determine the demagnetization factor (N). […]