What is HICOREX? Hicorex is the Hitachi Magnetics Corp. tradename for a new family of rare-earth cobalt high energy permanent magnets. Special manufacturing techniques and equipment for this product have been developed and installed at Edmore, Michigan. Hicorex permits designs with performance levels not possible with other magnetic materials, because of the extremely high magnetic moment, the high energy product, and the favorable recoil properties which it displays. These factors have resulted in Hicorex becoming the favorite among many magnet users formerly employing alnico, ceramic, platinum cobalt permanent magnets, or electromagnetism.
HICOREX - Powder Metallurgy Hicorex magnets are fabricated by pressing small particle rare earth cobalt powder properly aligned by the influence of a magnetic field, then sintering to high densities and heat treating to optimize properties. These magnets have a preferred direction of magnetization. Radial orientation and multi-pole configurations are feasible in some instances. As with sintered Ainico, rare earth cobalt magnets lend themselves to pressing to size for many shapes, thereby reducing the amount of finish grinding. Powder preparation using high purity materials assures magnetic and physical quality of the finished magnets.
Properties of HICOREX 90, 96, 99 During the past decade, the unit properties of Hicorex permanent magnets have improved substantially. New alloys of higher unit properties have been developed. A host of new alloys with different sets of properties suited to specific applications have been introduced in the market. The above progress in material development has resulted in the use of Hicorex in a number of devices where alnico and ceramic would not function. The unit properties of Hicorex permanent magnets are markedly different than those of alnico and ceramic materials. A one to one replacement of alnico or ceramic by Hicorex will be very expensive and at times detrimental to system performance. It is very important for the designer to have a good knowledge of the magnetic properties of Hicorex before des:gning a system. The following are some key properties of Hicorex and their associated advantages in systems design. 2
Maximum Energy Product (BH) max:
The high energy product (5-6 times that of ceramic and 3-4 times that of ainico) allows the system to use a much smaller volume of magnet, thus miniaturizing the size of the system, increasing the system torque or force to inertia ratio, and reducing the system mechanical time constant.
Remanence Br The values of remanence in Hicorex permanent magnets range from 8200 gauss to around 10,000 gauss depending on the specific alloy. This high value of induction results in high flux density in the gap thus improving torque, output power, efficiency and force constant of dynamic devices.
Intrinsic and Normal Coercivity, Hci, Hc Hicorex has very high coercive force. The intrinsic coercivity (Hci) of Hicorex is up to 30 times higher than alnico and 10 times higher than ceramic. This property makes the magnet virtually immune to accidental demagnetizing effect. It allows the designer to use thin magnets (in the direction of magnetization) in his device. It makes the magnet less prone to demagnetizing in repulsion mode devices. It allows the designer to magnetize the magnet and then assemble it into his device without using a keeper as is conventionally done with some grades of alnico. 1.
Parallel Alignment (H90A, H96A, H99A)
In this method, the alignment field is parallel to the direction of pressing. The alignment field is produced by a solenoid (coil) placed around a die system in the press. Fig 1Oa demonstrates this method schematically.
Perpendicular Alignment (H90, H96B, H99B)
The alignment field in this method is generated by an electromagnet whose poles are placed against the outside walls of the die system (Fig. 10b). The direction of alignment is perpendicular to the direction of pressing.
Using a given alloy (for example Sm Co5), the magnet will exhibit higher magnetic properties using perpendicular alignment rather than using parallel alignment.
Examining the two methods of alignment one can see that there are limitations on the configuration of the magnets if perpendicular alignment is to be used. For example, an axially aligned ring magnet can not be manufactured using the perpendicular technique of alignment. Therefore it is necessary to consider the shape of the magnet to be used when designing a magnetic circuit to be sure that the desired magnetic properties can be obtained. See magnetic properties of H-90A vs H-90B and H-99A vs H-99B. Please contact us for further details.
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HICOREX Advantages
Permits use in high field strength applications such as high torque motors.
Key features for magnet users: MINIATURIZATION IS A REALITY. Best choice for watches, TVV7, and motors.
SIZE REDUCTION Smaller magnets and return paths aid system miniaturization, resulting in design economies.
MOVING-MAGNET APPLICATIONS. This design principle utilizes the high magnetic moment.
TEMPERATURE STABILITY. Only small flux changes over a wide temperature range.
RECOIL PERMEABILITY OF ONE. Allows magnetizing in or out of the final circuit without performance sacrifice.
Applications
REMARKABLE REPULSION Applications using this mode are possible because the extremely high intrinsic coercivity.
We at Hitachi Magnetics Corp. are experienced in circuit design and magnet fabrication. Magnets can be furnished as individual units or built into sub-assemblies, such as motor stators. Hicorex magnets are being used in a variety of applications. Some uses are:
RESISTS DEMAGNETIZATION
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HICOREX: High Energy Magnets From HITACHI The inside pages show the intrinsic and normal demagnetization curves for Hicorex. These curves are presented on a scale, convenient for use in graphical analysis of designs.
Typical Hicorex sub-assemblies designed and produced by Hitachi. The top row, left to right, shows a small d.c. motor stator and two low inertia cup-type motor sub-assemblies. At lower left is a sensor rotor assembly and at lower right an aero space sub-assembly.
Temp. C 50 100 159 200
B/H = ¼ B/H – ½ B/H = 1 B/H = 2 B/H = 10 -0.9 -
-0.4 -0.9 -0.3 -7.0
-0.4 -0.8 -1.4 -2.0
0.0 -0.1 -0.25 -0.5
0.0 0.0 0.0 -0.2
Thse are typical values. Changes in geometry, weight and composition cause some variation in
Irreversible Losses Hicorex exhibits a permanent or irreversible loss in properties when exposed to high temperatures. The magnitude of the loss depends upon the temperature and permeance coefficient (B/H) of the magnet. Prior exposure to high temperature for several hours stabilizes the magnet, and recycling does not produce additional irreversible loss. Stabilization at a few degrees above the expected service temperature is effective. We recommend that a service temperature of 2500C not be exceeded for Hicorex 90 and 99 materials ; 1500C for Hicorex 96. IRREVERSIBLE LOSS, PERCENT (Hicorex 90)
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irreversible losses.
Reversible Losses Stabilized magnets change properties with temperature, but these changes are completely reversible, and the properties return to the initial values when the magnet is back at room temperature. Temperature changes cause a reversible displacement of the Hicorex demagnetization curve, producing a slight decrease in properties at elevated temperatures, and conversely, a slight increase in properties at low temperatures.
necessitating expensive grinding operations. Hicorex magnets can be finished to close tolerances which, in simple shapes, is relatively inexpensive. However, c ose tolerances on complex shapes and sub-miniature sizes can be expensive.
DESIGN ASSISTANCE Hitachi Magnetics Corp. engineers can assist you in all phases of magnetic circuit design. Should such assistance be desired, furnish details on your application such as: flux density; physical limitations of magnet; air gap dimensions; proximity of stray fields; expected shock or vibration; intended magnet mounting method; and a description of your magnetizing capability. The engineers at Hitachi Magnetics Corp. will select the Hicorex magnet size and configuration which makes maximum use of Hicorex properties. 6
STANDARD SIZES
HOW TO SPECIFY Standard Magnets
Dimensions and Tolerances In Inches
Standard items should be specified by catalog number. In addition, the desired quantity, expected temperature of operation and permeance coefficient (B/H) should be stated. Temperature stabilization of magnetic properties prior to shipment is available.
Special Magnets We suggest that a sketch showing desired grade, shape, size, tolerances, direction of orientation and temperature requirement be submitted. Also advise if magnets are or are not to be magnetized prior to shipping. Magnets will be shipped in the magnetized condition unless specified otherwise. If possible, a full description of the application including circuit, layout, environmental conditions, etc. should be provided to assist in choosing proper production, inspection, and test procedures.
Discs: Dwg.# 9OC90A 9OC91A 9OC92A 9OC93A Squares: Dwg.# 90830A 9OS31A 9OS32A 9OS33A Rectangle 9OS4608 9OS461 B .010
Dia. .250 .500 .750 1,000
Tol. .010 .010 .015 .015
Thk. .100 .190 .285 .375
Tol. .005 .010 .010 .010
Side .250 .500 .750 1,000 2,000 2,100
Tol. .010 .010 .015 .015
Thk. .100 .210 .320 .425
Tol. .005 .010 .010 .010
.030
.525
.010
2,000
.030
.525
2,100
Assemblies Hitachi Magnetics Corp. is placing increased emphasis on supplying completely integrated permanent magnet circuits with one source of responsibility for design, magnetization and calibration. Often fabrication and magnetization are only feasible when magnet and circuit elements are integrated in the magnet manufacturing plant.
DIMENSIONAL TOLERANCES
Magnets are magnetized parallel to thickness (except for 9OS461 8). Magnets are shipped magnetized.
Standard Hicorex magnets, and specially fabricated shapes are available from the Permag Corp., who are distributor fabricators for HMC materials. Permag facilities are located in Los Alamitos and Sunnyvale, California; Norcross, Georgia; Elk Grove Village, Illinois; Billercia, Massachusetts; Troy, Michigan; Eden Prairie, Minnesota; Hicksville, New York; Toledo, Ohio and Richardson, Texas.
AS-SINTERED TOLERANCES, IN INCHES Dimensions Up to 0. 125 inch 0. 126 to 0.625 inch 0.626 to 1.250 inch 1.251 to 3.000 inch
Tolerances +.005 +.010 +.015 +.031
CAUTION Many metals in fine particle form can ignite spontaneously.
These as-sintered tolerances are typical values which may be expected on simple shapes and solid pieces. Rings with heavy wall thickness may be considered simple shapes. Thin-wall rings and arc segments distort considerably during sintering,
Among these metals are the rare-earths and their alloys. Grinding operations generate fine particles and care should be exer-cised in griding Hicorex magnets as fire
can result. In addition, care should be exercised in the disposal of grinding waste. This is best done by dispersing the particles in a hydrocarbon oil, for disposal as a flammable sludge. In case of fire use dry sand or graphite powder such as Lith-X from Ansul) as an extinguisher. Avoid use of water, carbon dioxide, or standard powder fire extinguishers. HITACHI MAGNETICS CORPORATION EDMORE, MICHIGAN QM TELEX HITACHI EDME 22-6309 PHONE (517) 427-5151 Litho in U.S.A.
