Ferrite Magnet

Ferrite magnet is made of SrO or BaO and Fe2O3 by ceramic processing technology. Ferrite magnet is very hard and brittle, and requires specialized machining techniques. Moreover, ferrite magnets enjoy in an unmagnetized state. Due to their low cost, Ferrite magnet enjoy a very wide range of applications, from motors and loudspeakers to toys and crafts, and are the most widely used permanent magnets today.


Manufacturing Process


Pressing and sintering involve pressing very fine ferrite powder in a die firstly, and then sintering this pressed magnet. All fully dense Ferrite magnet is produced this way. Ferrite magnet can be wet pressed or dry pressed. Wet pressing yields better magnetic properties, but poorer physical tolerances. Generally, the powder is dry for grade 1 or 5 materials, and wet for grade 8 and higher materials.

 

Sintering involves subjecting the material to high temperatures to fuse the pressed powder together, thus creating a solid material. Ferrite magnet produced through this process usually needs some finish machining, otherwise surface finishes and tolerances are not acceptable. Some manufacturers extrude instead of press wet powder slurry and then sinter the material. This is sometimes done for arc segment shapes, where the arc cross-section is extruded in lengths, sintered, and then cut into length.


Machining


Ferrite magnet is brittle, and prone to chipping and cracking. Special machining techniques must be used to machine this material. We are fully equipped to machine these materials to your blueprint specifications.


Surface treatments


The corrosion resistance of Ferrite magnet is considered excellent , and no surface treatments are required. However, Ferrite magnet may have a thin film of fine magnet powder on the surface and for clean, non-contaminated applications, some form of coating may be required.


Magnetizing


Ferrite magnet requires magnetizing fields of about 10 kOe. They can be magnetized with multiple poles on one or both pole surfaces.


Anisotropic grades are oriented in the manufacturing direction, and must be magnetized in the direction of orientation. Isotropic grades are not oriented and can be magnetized in any direction, although some degree of greater magnetic strength will be found in the magnetizing dimension, usually through the shortest dimension.

 

                    

 

Magnetic properties of Ferrite magnet

 

Grade Residual Induction Coercive Force Intrinsic Coercive Force Maximum Energy Product Maximum Working Temperature
Br Hcb Hcj (BH)max Tw
mT kA/m kA/m kJ/m3
[kGs] [kOe] [kOe] [MGOe]
HF8/22 200-220 125-140 220-230 6.5-6.8 300°
[2.00-2.20] [1.57-1.76] [2.76-2.89] [0.8-1.1]
HF20/19 320-333 170-190 190-200 20.0-21.0 300°
[3.20-3.33] [2.14-2.39] [2.39-2.51] [2.5-2.7]
HF20/28 310-325 220-230 280-290 20.0-21.0 300°
[3.10-3.25] [2.76-2.89] [3.52-3.64] [2.5-2.7]
HF22/30 350-365 255-265 290-300 22.0-23.5 300°
[3.50-3.65] [3.20-3.33] [3.64-3.77] [2.8-3.0]
HF24/16 350-365 155-175 160-180 24.0-25.5 300°
[3.50-3.65] [1.95-2.20] [2.01-2.26] [3.0-3.2]
HF24/23 350-365 220-230 230-240 24.0-25.5 300°
[3.50-3.65] [2.76-2.89] [2.89-3.01] [3.0-3.2]
HF24/35 360-370 260-270 350-360 24.0-25.5 300°
[3.60-3.70] [3.27-3.39] [4.40-4.52] [3.0-3.2]
HF26/16 370-380 155-175 160-180 26.0-27.0 300°
[3.70-3.80] [1.95-2.20] [2.01-2.26] [3.3-3.4]
HF26/18 370-380 175-185 180-190 26.0-27.0 300°
[3.70-3.80] [2.20-2.33] [2.26-2.39] [3.3-3.4]
HF26/24 370-380 230-240 240-250 26.0-27.0 300°
[3.70-3.80] [2.89-3.01] [3.01-3.14] [3.3-3.4]
HF26/26 370-380 230-240 260-270 26.0-27.0 300°
[3.70-3.80] [2.89-3.01] [3.27-3.39] [3.3-3.4]
HF26/30 385-395 260-270 300-310 26.0-27.0 300°
[3.85-3.95] [3.27-3.39] [3.77-3.89] [3.3-3.4]
HF28/26 385-395 250-265 260-275 28.0-30.0 300°
[3.85-3.95] [3.14-3.33] [3.27-3.45] [3.5-3.8]
HF28/28 385-395 260-270 280-290 28.0-30.0 300°
[3.85-3.95] [3.27-3.39] [3.50-3.60] [3.5-3.8]
HF30/26 395-405 250-260 260-270 30.0-31.5 300°
[3.95-4.05] [3.14-3.33] [3.27-3.39] [3.8-3.9]
HF32/17 410-420 160-170 165-175 32.0-33.0 300°
[4.10-4.20] [2.01-2.14] [2.07-2.20] [4.0-4.1]
HF32/22 410-420 215-225 220-230 32.0-33.0 300°
[4.10-4.20] [2.70-2.83] [2.76-2.89] [4.0-4.1]
HF32/25 410-420 240-250 250-260 32.0-33.0 300°
[4.10-4.20] [3.01-3.14] [3.14-3.27] [4.0-4.1]

 

Physical properties of Ferrite magnets

 

Parameters Units Indicators
Recoil Permeability Gs/Oe 1.05-1.3
Curie Temperature ≥450
Temp.Coeff.of Br ℃/% -0.2
Temp.Coeff.of Hcj ℃/% -0.2-0.5
Density g/cm3 4.6-5.0
Specific Resistance Ω.cm ≥106 
Coefficient of Thermal Expansion 10-6/k 7-15X10-6
Hardness   46 - 50