Just doing our bit to help make better cars. High-performance thin-shape anisotropic magnets FB13B / FB14H

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1 Just doing our bit to help make better cars. High-performance thin-shape anisotropic magnets FB13B / FB14H Making a giant leap toward slimmer ferrite magnets Magnet usage is considered a barometer of the maturity of industrial society. In recent years, rare-earth neodymium magnets have risen to the top of the market in terms of production value, but resource-abundant ferrite magnets continue to dominate the field in production volume. Thus, improving ferrite magnet performance can be the key to addressing many issues facing society as a whole, including energy-saving solutions, environmental concerns, and resource conservation. TDK has developed a new production method using FB12 material basis, which boasts some of the best properties in the world, to create a mass production technique for FB13B/FB14H high-performance thin-shape anisotropic ferrite magnets that are only approximately 1.0 mm thick. These new magnets not only contribute to reductions in electrical vehicle motor size and weight, but also make the design of a wide variety of motors and actuators more free and flexible 01

2 The world's first ferrite magnet discovered by accident The world's first ferrite magnet was discovered in 1930 by Dr. Yogoro Kato and Dr. Takeshi Takei, two professors at the Tokyo Institute of Technology. Dr. Takei, a student of Dr. Kato, was investigating how lowering zinc yield during the zinc refining process affected the physical properties of ferrite when he happened upon ferrite with high magnetism levels. Up to that point, magnets had almost always been composed of metal, but Dr. Takei made the monumental discovery that like iron rust, ferrite's primary component was ferric oxide, making it a viable magnet material. Dr. Takei's discovery was a ferrite magnet with the spineltype crystal structure represented by the MOFe2O3 chemical formula, a magnet later commercialized as the "OP magnet." However, the product's low magnetic force limited its scope of application. Mass production of practical ferrite magnets began after the development of magnetoplumbite (MO6Fe2O3) ferrite magnets in the 1950s. Now, the main products in the field include Ba (barium) ferrite magnets and Sr (strontium) ferrite magnets. Due to the fact that ferrite magnets are ceramic (metal-oxide) magnets with oxygen atoms that do not affect magnetism, they will always demonstrate less magnetic force than metal magnets of the same volume. However, advances in material technology and sintering technology elevated the magnetic properties of ferrite magnets to rival those of alnico magnets (common alloy magnets) by the 1960s, paving the way for the use of ferrite magnets in speakers, motors, and other areas. The fundamental principles of magnetic balance Attraction Attraction Electromagnet Sample Sample magnetization is measured by balancing the attraction on the coil. Electromagnet Dr. Yogoro Kato (L) and Dr. Takeshi Takei (R) One day in June 1930, Dr. Takei accidentally forgot to turn off his laboratory equipment before going home. The next day, the ferrite had taken on incredible magnetic properties, disrupting the magnetic balance (the magnetic field cooling effect). This marked the discovery of the world's first ferrite magnet. 02

3 TDK High Performance Ferrite Magnets, FB series Sr ferrite magnets are often used in situations that require strong magnetic force. This is because Sr magnets offer the best residual flux density (Br) and coercive force (HCJ) of all ferrite magnets. Sr ferrite is represented by the SrO6Fe2O3 chemical formula, but adding trace elements improves properties. Although researchers have made exhaustive searches for a wide array of different material compositions, leading many to believe that ferrite magnets had reached their maximum property potential, TDK developed La-Co (lanthanum-cobalt) type ferrite magnet,fb9 series in 1997,taking advantage of new material composition to achieve remarkable improvements over conventional magnet properties. Using this new composition, the FB9 series succeeded in improving maximum energy product by approximately 30% over the traditional FB6 series. The key to unlocking the maximum potential of the material lies in TDK's process technology, one of the company's core technologies. FB12, which entered the market in 2007, is a new material that surpasses the magnetic properties of the FB9 series by miniaturizing and homogenizing ferrite powder and establishing microstructure controls. FB12 has over 20% greater maximum energy product than the FB9 series, makes dramatic improvements to demagnetization resistance in lowtemperature regions, and maintains stable power over a broad temperature scope ranging from -40 to 150 C (TDK owns many patents worldwide on La-Co type ferrite magnets). 03

4 Contributing to motor miniaturization ( Ferrite magnet type small motors) Since ferrite magnet is a kind of ceramic,it used to be difficult to produce thinner size less than 3mm by its conventional production method. However,the demands of thin magnet design is increasing to make electrical DC motors smaller and lighter. Thus,TDK developed new production method of ferrite magnets which is called NS1. NS1 applies TDK s own high density filling method with FB12 material basis,which enable to produce high-performance thin-shape anisotropic ferrite magnets. The proper thickness size is 1.0mm 2.5mm. FB13B and FB14H are newly developed by utilizing NS1 method. The figire below shows the example of motor miniaturization by using high-performance thin-shape anisotropic hard ferrite material (FB13B,FB14H) in a multipolarized motor design. Characteristic distribution Residual flux density Br [mt] Coercive force HCJ [ka/m] 04

5 Achieving motor characteristics close to the one with neodymium bonded magnet type By increasing the demand trend for motor miniaturization in recent years,neodymium bonded magnet having its configuration flexibility is also highly considered for several motor applications. When applied to motors for electrical items in demanding usage environments, however, neodymium bond magnets must be coated to improve heat resistance and corrosion resistance reliability. TDK's high-performance thin-shape anisotropic ferrite magnets (FB13B, FB14H) take advantage of the properties of ferrite with excellent heat resistance and corrosion resistance, thus eliminating the need for any additional coating. The magnetization can also be easily applied to motors after assembly (see the table below for more information). The figure shows an example of replacing a neodymium bond magnet with a FB13B/FB14H magnet. The process involves adjusting housing thickness/magnet wall thickness, but does not require any changes to motor diameter or rotor diameter. Nd bond system Conventional ferrite NS1 method ferrite Br(mT) HCJ(kA/m) HCJ temperature coefficient (%/ ) Heat resistance Corrosion resistance Thin-shape product configuration freedom Ease of magnetization Anisotropy *2 Isotropy FB6B FB13B *2 Neodymium bond magnet FB13B C-type magnet (thickness: 1.1 mm) Housing C-type magnet (thickness: 2.0 mm) 05

6 Special configuration (e.g wide-arc shape) enable small motor to improve the torque Breaking through the limitations of conventional methods, the NS1 method allows a greater degree of ferrite magnet configuration freedom and ensures compatibility with special wall shapes. The method can, for example, make it possible to use a C-type motor magnet in a wide-arc configuration that wraps around the rotor without having to modify the basic design of the motor part. This maximizes the use of empty space in the motor case, and, by taking full advantage of FB13B/ FB14H potential, achieves motor performance that rivals that of neodymium magnets. As shown in the graph below, the new material provides a significant boost in the starting torque of the motor, but combining it with a wide-arc shape produces an even greater increase in torque, comparing favorably with the performance of neodymium magnets. By optimizing particle orientation and thus improving magnetization orientation, the magnet achieves the world's best ferrite magnet properties. The new FB13B/FB14H materials, products of TDK's material technology, process technology, and other core technologies, make thin-shape, high-performance ferrite magnets a reality and a big part of reducing the size and improving the performance of various motors and actuators. Conventional shape Wide-arc shape FB5D FB13B FB13B Neodymium bond magnet Conventional shape Conventional shape Wide-arc shape Conventional shape 06

7 Main features Contribute to compact in and lighter weight motor design by realizing thin-shape magnet production ( thickness : mm) Excellent heat resistance, corrosion resistance, and ease of magnetization Further improvement of irreversible demagnetization durability at lower temp. with FB12 material basis. ( Higher coercive force HCJ, and excellent temp. coefficient of HCJ) Optimized grain orientation control improves the magnetic anisotropy to create ferrite magnets with the world s highest performance Support for specially-shaped configurations allows greater design freedom Main applications Power windows, seat actuators, fuel pumps, other small motors and actuators Magnetic properties/physics Mechanical properties Material Composition Residual flux density Br Coercive force HCB Coercive force HCJ Maximum energy product (BH)max Recoil permeability Temperature coefficient of Br Br/Br/ T Curie temperature Tc Coefficient of thermal expansion L/L/ T Specific heat Density Deflection strength Compressive strength Tensile strength C// C FB13B FB14H SrO Fe2O3 SrO Fe2O3 [mt] 475±10 470±10 (kg) 4.75± ±0.1 [ka/m] 340±20 355±20 (koe) 4.27± ±0.25 [ka/m] 380±20 430±20 (koe) 4.77± ±0.25 [kj/m 3 ] 44.0± ±1.6 (MGOe) 5.5± ±0.2 µrec 1.05 to to 1.1 [%/K] (%/ ) [K] ( ) [1/K](1/ ) 15x x10 6 [1/K](1/ ) 10x x10 6 [J/kg K] (cal/g ) [kg/m 3 ] 5.07 to 5.17x to 5.12x10 3 (g/cm 3 ) 5.07 to to 5.12 [N/m 2 ] 0.5 to 0.9x to 0.9x10 8 (kgf/mm 2 ) 5 to 9 5 to 9 [N/m 2 ] >6.9x10 8 >6.9x10 8 (kgf/mm 2 ) >70 >70 [N/m 2 ] 0.2 to 0.5x to 0.5x10 8 (kgf/mm 2 ) 2 to 5 2 to