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Neodymium Magnets, Sample 4: 81Fe-4B-15Nd Sintered (Sagawa 1988)
Neodymium magnets are iron, boron and neodymium. Sagawa's team at Sumitomo melted the three together, ground the casting to a powder finer than 10 µm, lined the grains up in a magnetic field while pressing them, and sintered the compact in argon. This is their sample 4, 81 % iron, 4 % boron and 15 % neodymium by atoms: 13.4 MGOe.
Source: M. Sagawa et al. (Sumitomo Special Metals), US 4,770,723 (1988). Unknown: how the pure iron, the ferroboron and the neodymium metal are made; the patent does not say. The magnetising is ours, after Przybylski et al., Sensors 16:569 (2016). The 1 kg weights are our arithmetic from the patent's atomic percentages. Picture: the patent's Fig. 8.
Ògbóǹtarìgì
2 days
Ìlànà
1
1
Weigh sample 4: 81 Fe, 4 B, 15 Nd
Weigh sample 4: 81 Fe, 4 B, 15 Nd
Sample 4 is 81 % iron, 4 % boron and 15 % neodymium by atoms. Use 99.9 % electrolytic iron, ferroboron (19.38 % B, 5.32 % Al, 0.74 % Si, 0.03 % C, the rest iron) and neodymium of 99.7 % or better. Ours: a 1 kg melt, by arithmetic: 647.4 g iron, 33.2 g ferroboron, 321.5 g neodymium. Unknown: how these three are made.
Àwọn ohun èlò fún ìgbésẹ̀ yìí:
Irin elekitirolitiki647.4 g
Ferroboron33.2 g
Irin neodymium321.5 gÀwọn irinṣẹ́ tí a nílò:
Òǹwọ̀n ìdọ́gba2
2
Melt by high frequency in argon and cast
Melt by high frequency in argon and cast
Melt the charge in a high-frequency (induction) furnace under argon and pour it into a water-cooled copper mould.
Àwọn irinṣẹ́ tí a nílò:
Ìléru induction
Ìkòkò Amọ̀ Tí Ń Kojú Iná
Argon
Àgbá gáàsì tí a fi ìfúnpá kún
Mọ́ọ̀dù bàbà tí a fi omi tutù
Ìbọ̀wọ́ Tí Ń Fara Da Ooru3
3
Stamp to 35 mesh, ball-mill to 3-10 µm
Stamp to 35 mesh, ball-mill to 3-10 µm
Crush the casting in a stamp mill until it passes a 35-mesh sieve. Then grind it in a ball mill for 3 hours, to 3-10 µm.
Àwọn irinṣẹ́ tí a nílò:
Ẹ̀rọ Lílù Òkúta
Àkójọ ajọ̀ (ihò onípele)
Ẹ̀rọ Lílọ Bọ́ọ̀lù Irin
Gíláàsì ààbò4
4
Press in a 10 kOe field at 1.5 t/cm²
Press in a 10 kOe field at 1.5 t/cm²
Line the powder up in a magnetic field of 10 kOe and press it at 1.5 tonnes per cm². Unknown: the size and shape of the magnets.
Àwọn irinṣẹ́ tí a nílò:
Ẹ̀rọ ìtẹ̀ pẹ̀lú pápá òòfà5
5
Sinter in argon at 1000-1200 °C
Sinter in argon at 1000-1200 °C
Sinter the compacts at 1000-1200 °C for about one hour in argon, then let them cool. Sample 4 measured 10.8 kG remanence, 2.8 kOe coercivity and 13.4 MGOe.
Àwọn irinṣẹ́ tí a nílò:
Ààrò Ọ̀pọ́nArgonÀgbá gáàsì tí a fi ìfúnpá kúnÌbọ̀wọ́ Tí Ń Fara Da Ooru6
6
Magnetise the magnets
Magnetise the magnets
Ours, after Przybylski et al., Sensors 16:569 (2016): put each magnet in the coil of an impulse magnetiser and discharge a capacitor bank through it. They found a field of 1200 kA/m enough to saturate N38 sintered Nd-Fe-B; their magnetiser used a 1 mF bank charged up to 5000 V, a thyristor switch and a 440-turn coil of 3 mm copper wire with an 80 mm bore.
Àwọn irinṣẹ́ tí a nílò:
Ẹ̀rọ ìfi oofa síÀwọn ohun-èlò
3- 647.4 gÀyè
- 33.2 gÀyè
- 321.5 gÀyè
Àwọn irinṣẹ́ tó nílò
14- Àyè
- Àyè
- Àyè
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