Grades
Br, Hcb, Hcj and (BH)max
The four numbers that actually specify a sintered magnet.
Ando’s performance article walks the four catalogue numbers buyers should put on a print:
- Br — remanence. How much flux density remains after the magnetizing field is removed.
- Hcb — coercivity of induction. Resistance to demagnetization as seen on the B-H curve.
- Hcj — intrinsic coercivity. The stronger measure of resistance to reverse fields and temperature.
- (BH)max — maximum energy product. The headline “strength” number, in kJ/m³ or MGOe.
Grades published on product pages include N35–N52, N35M–N50M, N33H–N48H and N30SH–N35SH. The letter after the number is the temperature / coercivity class, not a marketing suffix. Raw materials, press orientation, sintering and the humidity history of the part all move these numbers — which is why a grade on a carton is not a substitute for incoming inspection when the application is a motor.