Chinese magnet datasheets are full of "GB/T" numbers, and they are not decoration. "GB" means a Chinese national standard; the "/T" marks it as recommended rather than mandatory. The digits identify the document, and the year shows which edition applies — for example GB/T 13560-2017. Here is a simple map of the family.
GB/T 13560 — the main spec for sintered NdFeB
This is the core document. It defines the grades — N, M, H, SH, UH, EH and TH — with the magnetic limits for each and how they are tested. When a supplier quotes "N42SH per GB/T 13560-2017", this standard is what the numbers mean. The current 2017 edition even covers higher-coercivity grades than the international IEC standard.
GB/T 3217 — how the numbers are measured
A grade is only as good as the measurement behind it. GB/T 3217 is the standard for measuring the magnetic curve in a closed circuit — the test that produces the Br, Hcb, Hcj and (BH)max values on every datasheet. Think of it as the rulebook for the test machine.
The supporting cast
- GB/T 23588 — production scrap: how to classify it, measure its rare-earth content, and sample it fairly. This is the basis for scrap trading.
- GB/T 34490 — recycled (remanufactured) sintered NdFeB magnets.
- GB/T 18880 — bonded NdFeB magnets, a different material family.
- GB/T 4180 — sintered samarium-cobalt magnets.
Two practical tips
First, check the year: a certificate citing the 2000 or 2009 edition may not meet a drawing based on 2017. Second, write the magnetic limits explicitly on your drawing — remanence and coercivity — not just a grade name, because "N42SH" is not identical across every supplier and standard.
Read on: grades explained → · density and physical testing →