Sintered Ferrite Magnet

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.

Sintered Ferrite Magnet

Manufacturing Process of Sintered Ferrite Magnet

Sintered Ferrite Magnet Manufacturing Process

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
  • The above-mentioned data of magnetic properties and physical properties are given at room temperature.
  • The max working temperature of magnet is changeable due to length-diameter ratio, coating thickness and other environment factors.

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