Ferrite magnet, otherwise referred as ceramic magnet, is developed by Japanese scholars Dr. Yogoro Kate and Dr. Takeshi Takei in 1930. As nonmetallic type of permanent magnetic material, ferrite magnet is utilizing iron oxide (Fe2O3), Barium Carbonate (BaCO3) or Strontium Carbonate (SrCO3) as raw material and then manufactured through ceramics process. Maximum operating temperature of sintered ferrite magnet can arrive 250 degrees Celsius. Sintered ferrite magnet also has superior corrosion resistance. Sintered ferrite magnet is generally used in various areas in the past several decades and its market share is still very large even the application range of sintered Neodymium magnets is more and more extensive. The most representative applications of sintered ferrite magnet include loudspeakers, permanent magnet (PM) motors and generators.
Manufacturing Process of Sintered Ferrite Magnet
Magnetic Properties of Sintered Ferrite Magnet
There are three standards for the grade of sintered ferrite magnet: United States Industry Standard, International Electrotechnical Commission Standard, and Chinese Standard. International Electrotechnical Commission Standard is confined to European. The grade is made up of the minimum value of the maximum energy product in SI unit “kJ/m3” and intrinsic coercivity in SI unit “kA/m”. For United Stated Industry Standard, grade of sintered ferrite magnet is generally labelled with the letter “C” and a number, such as C5 and C8. Since most production of sintered ferrite magnet is in China, Chinese nomenclature system has taken over the naming right of grade. All grades beginning with the letter “Y” which is an identifier for sintered ferrite magnet. The number following it represent the maximum energy product and any letter after the number is an additional identifier.
Standard | Grade | Remanence Br | Coercivity Hcb | Intrinsic Coercivity Hcj | Max. Energy Product (BH)max | ||||
mT | kG | kA/m | kOe | kA/m | kOe | kJ/m3 | MGOe | ||
Chinese Standard | Y8T | 200-235 | 2.0-2.35 | 125-160 | 1.57-2.01 | 210-280 | 2.64-3.52 | 6.5-9.5 | 0.8-1.2 |
Y10T | 200-235 | 2.0-2.35 | 128-160 | 1.61-2.01 | 210-280 | 2.64-3.52 | 6.4-9.6 | 0.8-1.2 | |
Y20 | 320-380 | 3.2-3.8 | 135-190 | 1.70-2.39 | 140-195 | 1.76-2.45 | 18.0-22.0 | 2.3-2.8 | |
Y22H | 310-360 | 3.1-3.6 | 220-250 | 2.76-3.14 | 280-320 | 3.52-4.02 | 20.0-24.0 | 2.5-3.0 | |
Y23 | 320-370 | 3.2-3.7 | 170-190 | 2.14-2.39 | 190-230 | 2.39-2.89 | 20.0-25.5 | 2.5-3.2 | |
Y25 | 360-400 | 3.6-4.0 | 135-170 | 1.70-2.14 | 140-200 | 1.76-2.51 | 22.5-28.0 | 2.8-3.5 | |
Y26H | 360-390 | 3.6-3.9 | 220-250 | 2.76-3.14 | 225-255 | 2.83-3.20 | 23.0-28.0 | 2.9-3.5 | |
Y26H-1 | 360-390 | 3.6-3.9 | 200-250 | 2.51-3.14 | 225-255 | 2.83-3.20 | 23.0-28.0 | 2.9-3.5 | |
Y26H-2 | 360-380 | 3.6-3.8 | 263-288 | 3.30-3.62 | 318-350 | 4.00-4.40 | 24.0-28.0 | 3.0-3.5 | |
Y27H | 370-400 | 3.7-4.0 | 205-250 | 2.58-3.14 | 210-255 | 2.64-3.20 | 25.0-29.0 | 3.1-3.6 | |
Y28 | 370-400 | 3.7-4.0 | 175-210 | 2.20-2.64 | 180-220 | 2.26-2.76 | 26.0-30.0 | 3.3-3.8 | |
Y28H-1 | 380-400 | 3.8-4.0 | 240-260 | 3.02-3.27 | 250-280 | 3.14-3.52 | 27.0-30.0 | 3.4-3.8 | |
Y28H-2 | 360-380 | 3.3-3.8 | 271-295 | 3.41-3.71 | 382-405 | 4.80-5.09 | 26.0-30.0 | 3.3-3.8 | |
Y30 | 370-400 | 3.7-4.0 | 175-210 | 2.20-2.64 | 180-220 | 2.26-2.76 | 26.0-30.0 | 3.3-3.8 | |
Y30BH | 380-390 | 3.8-3.9 | 223-235 | 2.80-2.95 | 231-245 | 2.90-3.08 | 27.0-30.0 | 3.4-3.8 | |
Y30H-1 | 380-400 | 3.8-4.0 | 230-275 | 2.89-3.46 | 235-290 | 2.95-3.64 | 27.0-32.0 | 3.4-4.0 | |
Y30H-2 | 395-415 | 3.95-4.15 | 275-300 | 3.46-3.77 | 310-335 | 3.90-4.21 | 27.0-32.5 | 3.4-4.1 | |
Y32 | 400-420 | 4.0-4.2 | 160-190 | 2.01-2.39 | 165-195 | 2.07-2.45 | 30.0-33.5 | 3.8-4.2 | |
Y32H-1 | 400-420 | 4.0-4.2 | 190-230 | 2.39-2.89 | 230-250 | 2.89-3.14 | 31.5-35.0 | 4.0-4.4 | |
Y32H-2 | 400-440 | 4.0-4.4 | 224-240 | 2.81-3.02 | 230-250 | 2.89-3.14 | 31.0-34.0 | 3.9-4.3 | |
Y33 | 410-430 | 4.1-4.3 | 220-250 | 2.76-3.14 | 225-255 | 2.83-3.20 | 31.5-35.0 | 4.0-4.4 | |
Y33H | 410-430 | 4.1-4.3 | 250-270 | 3.14-3.39 | 250-275 | 3.14-3.46 | 31.5-35.0 | 4.0-4.4 | |
Y34 | 420-440 | 4.2-4.4 | 200-230 | 2.51-2.89 | 205-235 | 2.58-2.95 | 32.5-36.0 | 4.1-4.5 | |
Y35 | 430-450 | 4.3-4.5 | 215-239 | 2.70-3.00 | 217-241 | 2.73-3.03 | 33.1-38.2 | 4.2-4.8 | |
Y36 | 430-450 | 4.3-4.5 | 247-271 | 3.10-3.41 | 250-274 | 3.14-3.44 | 35.1-38.3 | 4.4-4.8 | |
Y38 | 440-460 | 4.4-4.6 | 285-305 | 3.58-3.83 | 294-310 | 3.69-3.90 | 36.6-40.6 | 4.6-5.1 | |
Y40 | 440-460 | 4.4-4.6 | 330-354 | 4.15-4.45 | 340-360 | 4.27-4.52 | 37.5-41.8 | 4.7-5.3 | |
American Standard | C1 | 230 | 2.3 | 148 | 1.86 | 258 | 3.5 | 8.36 | 1.05 |
C5 | 380 | 3.8 | 191 | 2.4 | 199 | 2.5 | 27 | 3.4 | |
C7 | 340 | 3.4 | 258 | 3.23 | 318 | 4 | 21.9 | 2.75 | |
C8 / C8A | 385 | 3.85 | 235 | 2.95 | 242 | 3.05 | 27.8 | 3.5 | |
C8B | 420 | 4.2 | 232 | 2.913 | 236 | 2.96 | 32.8 | 4.12 | |
C9 | 380 | 3.8 | 280 | 3.516 | 320 | 4.01 | 26.4 | 3.32 | |
C10 | 400 | 4 | 280 | 3.52 | 284 | 3.57 | 30.4 | 3.82 | |
C11 | 430 | 4.3 | 200 | 2.512 | 204 | 2.56 | 34.4 | 4.32 | |
C12 | 400 | 4 | 290 | 3.65 | 318 | 4 | 32 | 4 | |
European Standard | HF8/22 | 200/220 | 2.00/2.20 | 125/140 | 1.57/1.76 | 220/230 | 2.76/2.89 | 6.5/6.8 | 0.8/1.1 |
HF20/19 | 320/333 | 3.20/3.33 | 170/190 | 2.14/2.39 | 190/200 | 2.39/2.51 | 20.0/21.0 | 2.5/2.7 | |
HF20/28 | 310/325 | 3.10/3.25 | 220/230 | 2.76/2.89 | 280/290 | 3.52/3.64 | 20.0/21.0 | 2.5/2.7 | |
HF22/30 | 350/365 | 3.50/3.65 | 255/265 | 3.20/3.33 | 290/300 | 3.64/3.77 | 22.0/23.5 | 2.8/3.0 | |
HF24/16 | 350/365 | 3.50/3.65 | 155/175 | 1.95/2.20 | 160/180 | 2.01/2.26 | 24.0/25.5 | 3.0/3.2 | |
HF24/23 | 350/365 | 3.50/3.65 | 220/230 | 2.76/2.89 | 230/240 | 2.89/3.01 | 24.0/25.5 | 3.0/3.2 | |
HF24/35 | 360/370 | 3.60/3.70 | 260/270 | 3.27/3.39 | 350/360 | 4.40/4.52 | 24.0/25.5 | 3.0/3.2 | |
HF26/16 | 370/380 | 3.70/3.80 | 155/175 | 1.95/2.20 | 160/180 | 2.01/2.26 | 26.0/27.0 | 3.2/3.4 | |
HF26/18 | 370/380 | 3.70/3.80 | 175/185 | 2.20/2.33 | 180/190 | 2.26/2.39 | 26.0/27.0 | 3.3/3.4 | |
HF26/24 | 370/380 | 3.70/3.80 | 230/240 | 2.89/3.01 | 240/250 | 3.01/3.14 | 26.0/27.0 | 3.3/3.4 | |
HF26/26 | 370/380 | 3.70/3.80 | 230/240 | 2.89/3.01 | 260/270 | 3.27/3.39 | 26.0/27.0 | 3.3/3.4 | |
HF26/30 | 385/395 | 3.85/3.95 | 260/270 | 3.27/3.39 | 300/310 | 3.77/3.89 | 26.0/27.0 | 3.3/3.4 | |
HF28/26 | 385/395 | 3.85/3.95 | 250/265 | 3.14/3.33 | 260/275 | 3.27/3.45 | 28.0/30.0 | 3.5/3.8 | |
HF28/28 | 385/395 | 3.85/3.95 | 260/270 | 3.27/3.39 | 280/290 | 3.50/3.60 | 28.0/30.0 | 3.5/3.8 | |
HF30/26 | 395/405 | 3.95/4.05 | 250/260 | 3.14/3.33 | 260/270 | 3.27/3.39 | 30.0/31.5 | 3.8/3.9 | |
HF32/17 | 410/420 | 4.10/4.20 | 160/170 | 2.01/2.14 | 165/175 | 2.07/2.20 | 32.0/33.0 | 4.0/4.1 | |
HF32/22 | 410/420 | 4.10/4.20 | 215/225 | 2.70/2.83 | 220/230 | 2.76/2.89 | 32.0/33.0 | 4.0/4.1 | |
HF32/25 | 410/420 | 4.10/4.20 | 240/250 | 3.01/3.14 | 250/260 | 3.14/3.27 | 32.0/33.0 | 4.0/4.1 | |
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C5 = HF26/18 = Y30; C8 / C8A = Y30H-1; C1 = Y8T / Y10T; C7 = Y26H-2;
C8B = Y33; C9 = Y30H-2; C10 = Y33H; C11 = Y34; C12 = Y30H-2.
Physical Properties of Sintered Ferrite Magnet
Working stability of sintered ferrite magnet is strongly tied to their physical properties except magnetic properties. Sintered ferrite magnet is extremely prone to chipping or breaking owing to inherent brittleness.
Parameter | Unit | Value |
Density | g/cm3 | 4.9-5.1 |
Vickers Hardness | D.P.N | 400-700 |
Compression Strength | N/mm2 | 680-720 |
Coefficient of Thermal Expansion | 10-6/°C | C⊥: 10, C∥15. |
Electrical Resistance | mΩ·cm | 1 x 1010 |
Thermal Conductivity | W/(cm·℃) | 0.029 |
Tensile Strength | Pa | 34 x 106 |
Modulus of Elasticity | Pa | 1.8 x 1011 |
Flexural Strength | Pa | 62 x 106 |
Compression Strength | Pa | 895 x 106 |
Poisson’s Ratio | – | 0.28 |
Curie Temperature | ℃ | 450 |