Permanent magnet alloy fingerMagnetizationAfter removing the external magnetic field, it can still remain highremanenceOfMagnetic alloy。Permanent magnet alloy not only has high hardness and mechanical properties, but also has strong resistanceDemagnetizationAbilityCoercivityHigh value (more than 20kA/m), magnetic "hard" and other characteristics, so it is also calledHard magnetic alloy。
Permanent magnet alloy ismagnetic material It can be generally divided intoHard magnetic alloyandSoft magnetic alloy。Hard magnetic alloy is permanent magnetic alloy. Its permanent magnetic properties are good. Once it is saturated and magnetized, the magnetic field can be removed, and it can also maintain strong and stable magnetism for a long time.It has high intrinsic coercivity and strong anti demagnetization.Hard magnetic alloys include platinum cobalt alloy, samarium cobalt alloy, neodymium iron boron alloy, etc., which are commonly used in stomatology to make magnetic retainers.Soft magnetic alloy has high permeability and low coercivity. It is nonmagnetic and easy to be magnetized in a strong magnetic field. Once it is separated from the magnetic field, its magnetism disappears.Soft magnetic alloys include iron aluminum, iron cobalt, palladium cobalt nickel alloys, etc.It can be cast into any shape. The department of stomatology usually makes yoke and armature, which are combined with permanent magnets to form a closed magnetic circuit magnetic retainer.[1]
Permanent magnet alloy is also called "magnetic alloy".Hysteresis loop is the basic characteristic curve of magnetic materials.Coercive force HcThe alloy lower than 10Oe is soft magnetic alloy, for which HcThe value should be as small as possible, that is, the smaller the area enclosed by the hysteresis loop, the better.HcThe minimum value is about 0.002Oe.HcThe alloy with the value of 10-300Oe is called“Semi hard magnetic alloy”。HcAlloys with values higher than 300Oe are called "hard magnetic alloys".As a hard magnetic alloy, H is usually expectedcThe larger the area enclosed by the hysteresis loop, the bettercThe highest value is about 10000 Oe.Magnetic alloybelong toPrecision alloyAs a functional material, it is widely used in industry.
history
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natureExistingNatural magnetThe phenomenon of He Yongci was discovered in China very early.According to textual research, China has used natural resources in the Warring States PeriodmagnetitePolishedcompass, called "Sinan", was first recorded in Han Feizi's Youdu Chapter in the 3rd century BC.It is generally believed that the development history of modern permanent magnet alloy began in 1880, when the best permanent magnet alloy was carbon steel containing 1%~1.5% carbon, which was hardened by high temperature quenching.Its magnetism is very low,Maximum magnetic energy productLess than 2kJ/m.,CoercivityThe value is less than 4kA/m.Gradually developed at the beginning of the 20th centuryTungsten steelAnd chrome steel, so that the magnetism is slightly improved.In 1917, cobalt steel containing 35% cobalt appeared, makingMagnetic energy productIncrease to 8kJ/m.The coercivity is also increased to 20kA/m.
The development of permanent magnetic materials has gone through three stages: alloy magnet, ferrite and rare earth transition metal magnet.According to the level of magnetism, it can be roughly divided into two categories:[2]
1) General permanent magnetic materials, mainly including quenched martensitic steel, Al Ni Co alloy, Mn Al alloy, Fe Cr Co alloy, Cu Ni Fe alloy, Fe Co V alloy and permanent magnet ferrite, have poor magnetism, and the maximum magnetic energy product (BH) max generally does not exceed 80kJ/m3;
2)Rare earth permanent magnetic materials, such as samarium cobalt magnets (such as Sm Co5, SmtwoCoseventeenNd-Fe-B magnets, iron based rare earth nitrides and nanocomposite rare earth permanent magnets have excellent magnetic properties, among which the theoretical prediction value of the maximum magnetic energy product of NdFeB is as high as 500~600kJ/m3.
In 1931, the Japanese Mishima discovered the iron nickel aluminum based dispersion hardening alloy, which greatly improved the permanent magnetic properties.On this basis, cobalt, copper, titanium, niobium and other elements are added, andMagnetic field heat treatmentAnd directional crystallization and solidification, which became the most influential technology in the middle of the 20th centuryAluminium nickel cobaltIt is a permanent magnet alloy.The laboratory level reached (BH) max=108kJ/m3, and the maximum coercivity reached 150kA/m.Such alloys are produced in large quantities in the United States, Japan, Germany, Netherlands, Britain and other countries.During this period, a series ofDeformed permanent magnet alloy, such as iron cobalt tungsten and iron cobalt molybdenumPlatinum cobalt alloy, CopperFerronickelas well asIron cobalt vanadium alloyAnd iron chromium cobalt series, manganese aluminum carbon and other permanent magnet alloys.After the 1950s, with the gradual understanding of the physical and metallurgical properties of permanent magnet alloys, especially through the in-depth study of the internal structure and coercivity mechanism of the alloys, a series of high-performance permanent magnet alloys were developed, which made permanent magnet alloys obtain amazing development.especiallyRare earth permanent magnetThe appearance ofRare earth cobalt permanent magnet alloyThe laboratory level has reached (BH) max=262.7kJ/m3.RCo5 (R stands forrare earth element）Type A alloy is called the first generation rare earth permanent magnet alloy, and type R2Co17 alloy is called the second generation rare earth permanent magnet alloy.In 1983, Japanese Sagawa and others inventedNdFeB Permanent magnet alloy, called the third generation rare earth permanent magnet alloyMaximum magnetic energy productIt has reached 431.4kJ/m.,It has created the highest record of permanent magnet performance.For more than 100 yearsMagnetic energy productIt has increased by nearly 250 times,CoercivityIt has increased by nearly 100 times.The samarium iron nitrogen alloy under development is called the fourth generationRare earth permanent magnetAlloy.A new mechanism of dual phase nanocrystalline rare earth permanent magnetic alloy has also been developed.Permanent magnet alloys in different periods are shown in Figure 1:
Figure 1
China began to develop permanent magnet alloys in the late 1950s, and formally produced deformable permanent magnets andAluminium nickel cobaltIt is a permanent magnet alloy, and its magnetic properties are equivalent to those of similar products in the world.Some alloys, such as directionally crystallized Al Ni Co alloy, also created (BH) max=108kJ/m in the laboratory.The highest record of.In the early 1970s, China began to develop rare earth permanent magnet alloys. The varieties of alloys produced and the level of laboratory research are close to the international level, but there is a slight gap in the level of industrial production.
classification
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There are many kinds of permanent magnet alloys, no less than one hundred.According to the production process and usage habits, it can be generally divided into five categories:Rare earth permanent magnetAlloy,Aluminium nickel cobaltIt is a permanent magnet alloy, which canDeformed permanent magnet alloy, manganese aluminum carbon permanent magnet alloy and bonded rare earth permanent magnet alloy.
performance parameter
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Permanent magnet alloys are used in open circuit state as magnetic field source or action source.Choose different permanent magnet alloys according to different applicationsmagnetic circuit, forming the required magnetic field,magnetic field intensityThe size of is closely related to the magnetic properties and magnetic circuit of the alloy.
The magnetic field of its air gapstrength
Where Vm, Bm and Hm are the volumes of magnets respectively,Magnetic inductionandmagnetic field intensity；Vg and Hg are the volume and magnetic field strength of the air gap.Bm and Hm are equivalent toDemagnetization curveB and H at point A above.(Bm · Hm)=(B · H) YesPermanent magnetenergy density 2 times of, sayMagnetic energy product。The curve of magnetic energy product changing with B is calledMagnetic energyCurve, where the product of BD and HD corresponding to point D has the maximum value, calledMaximum magnetic energy product, expressed in (BH) max or (BH) m.Obviously, the larger the (BH) max of the permanent magnet alloy is, the better, and (BH) max is related to the residual magnetic induction strength andCoercivityClosely related.Therefore, the main basis for measuring the magnetic properties of permanent magnet alloys is the four parameters on the demagnetization curve, namely[3]
(1) (BH) max: maximum magnetic energy product, kJ/m3 (kJ/m3).
(4) Bonding process.For production of bonded permanent magnet alloy
(5) Warm extrusion process.Mainly used in the manufacture of manganese aluminum carbon alloy
purpose
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Permanent magnet alloy is an important functional material indispensable to modern industry and science and technology.People useMagnetic energyInteraction with magnetic energy, magnetic energy and electrical energy to convert magnetic energy into electrical energy or mechanical energy;Use the effect of magnetic field on materials to change the microstructure of materials, promote energy conservation and environmental protection.In all these devices, permanent magnetic alloys play an important role.[4]
Its main uses include: (1) electromechanical equipment and devices.Mainly including: variousPermanent magnet motorSuch as DC (rectifier and brushless) motorsSynchronous motor, swing andLinear motor、servo motor , torque orStepper motor；variousPermanent magnet generatorasalternator, AuxiliaryExciter, polyphase synchronous machine, ignition or other pulse generators;Various electromechanicalBrakeSuch as printer typehead drive, computer floppy disk drive (also known as voice coil motor VCM), laser focus and tracker (used for CD, VCRData processor)。Aircraft positioning brake, robot, etc;Moving coil ammeter and circuit breaker, micro displacement relay, etc.
(2) Acoustic transducer.Including: variousSounder, such as speakers, headphonesTelephone receiver, bellBuzzerandultrasonicSounder, etc;Sound receiver, such as microphone, ultrasonicPickup；And audio and video pickups.
(3)magnetic forceMechanics.It is mainly made of magnetic attraction and repulsion: clamping and lifting devices, such asElectromagnetic crane, machine tool chucks and fixtures, refrigerator door seals, advertising signs and toys;Traction devices, such as conveyor belt, concentratorCopierdrum;Couplers, such as synchronous torqueCouplingMagnetic water pump, linearFollower, oil buoy, etc;Magnetic bearingAnd magnetic levitation, such as passive watt hour metersUltracentrifugationDevicegyroscope, satellite kinetic wheelvortexMolecular pump、Maglev vehicleEtc.
