Ferromagnetic substance, which are its specific parameters 15

Basic properties of magnets1The nature of magnets: Magnets are magnetic, which can attract iron and make a reputation for being a unique item.

2.Magnets have poles, and each magnet has two poles, n pole and S pole, which exist in pairs. 3.

Temporary magnets and permanent magnets: When ferromagnetic materials are magnetized, they are easy to lose their demagnetizing properties, which are called temporary magnets (..).

Magnets are capable of generating magnetic fields and have the property of attracting ferromagnetic materials such as iron, nickel, cobalt, and other metals. Magnet is a natural ore, not invented by people, the first to discover and use magnets should be Chinese, that is, the use of magnets to make a "compass", one of the four major inventions in China.

Now magnets have been used in all aspects of our lives and have become a powerful material in our lives. By synthesizing alloys of different materials, the same effect can be achieved as magnets, and the magnetic force can also be improved. Early voyagers used this magnet as their earliest compass to discern direction at sea.

The first to discover and use magnets should be the Chinese, that is, to use magnets to make "compasses", one of China's four major inventions.

Magnets can be divided into "permanent magnets" and "non-permanent magnets". Permanent magnets can be natural products, also known as natural magnets, or they can be artificially manufactured, rather than permanent magnets, and will only be magnetic under certain conditions, usually in the form of electromagnets, that is, the use of electric current to strengthen their magnetic field. Magnets, also known as magnets, refer to objects or materials that have magnetic fields around and within themselves, and are divided into two categories: natural and man-made.

Artificial magnets are usually made of metal alloys, which are highly magnetic. It can also be divided into "permanent magnets" and "non-permanent magnets", that is, "hard magnets" and "soft magnets".

ImpactMagnetic materialsThere are many external factors for magnetic properties, among which temperature and frequency are the most important.

1) Temperature. Temperature has a particularly significant effect on the magnetic properties of magnetic materials. The permeability of general metal-like magnetic materials.

and saturation magnetic burial induction intensity decreases with the increase of temperature. When the temperature exceeds a certain value, the magnetic material loses its magnetism and becomes a paramagnetic substance.

2) Frequency. The change in frequency also has an effect on the magnetic properties. As the frequency increases, the magnetic permeability of the material decreases and the core loss increases.

Brief introduction. In addition, the magnetic properties of magnetic materials do not depend only on their chemical composition, but also on the method of machining and heat treatment conditions. Internal stresses arise during the machining of metallic magnetic materials.

This force can reduce the permeability of the material and the coercivity.

increase and loss increase. In order to relieve stress and restore magnetism, annealing is necessary. Bent pins.

Properties: Neodymium magnets (rubidium magnets), also known as neodymium iron-boron magnets, are tetragonal crystals formed by neodymium, iron, and boron. The magnetic energy product (BHMAX) of this magnet is greater than that of samarium cobalt magnets, and it is the substance with the largest magnetic energy product in the world at that time.

Application: This magnet is the most magnetic permanent magnet available today and is the most commonly used rare earth magnet. NdFeB magnets are widely used in electronic products such as hard drives, mobile phones, headphones, and battery-powered tools.

Maintenance: In order to avoid corrosion damage, the surface of the permanent magnet material needs to be protected during use, such as electroplating with gold, nickel, zinc, tin, and epoxy resin spraying on the surface.

Metallic elements, silvery-white, soft, chemically active and active, easy to release electrons under the action of light, and occur in water**. It is used to make photocells and vacuum tubes.

Neodymium is a rare earth element, and NdFeB alloy is a strong magnetic material. The common ones are used for headphones, the bass is strong, and many of Sony's headphones are used. The headphones made of this magnetic material have good performance, high sensitivity, transparent and clear timbre, and good bass.

The U.S. branch of Nippon Pulse Electric Co., Ltd. has developed a new type of linear motor containing rubidium magnets, which has an outer diameter of 25mm and 35mm. Due to the use of spherical housings and robust motor housings, they are durable and have a long service life; The new use of special threads and rotors containing rare earths of neodymium magnets (neodymium magnets with tens of times the magnetic force of ferrite magnets) provide higher efficiency and high driving force for the motor. Linear motors can be used in medical instrument pumps, semiconductor wafer operating machinery, optical camera systems, and communication antenna devices.

There are three main parameters:

1) Residual induction (BR), unit: Gaussian gauss, that is, after removing the magnetic field from the saturated state, the remaining magnetic flux density represents the strength of the magnetic field that the magnet can provide to the outside world;

2) Coercive force HC (coercive force), unit: Oersteds, that is, put the magnet in a reverse applied magnetic field, when the applied magnetic field increases to a certain strength, the magnetism of the magnet will disappear, the ability to resist the applied magnetic field is called coercivity, representing the anti-demagnetization ability of the magnet;

3) Magnetic energy product bhmax, unit gauss-oersteds, that is, the magnetic field energy generated per unit volume of material, is a physical quantity of how much energy can be stored in the magnet.

For ND-Fe-B sintered magnets, the B-H magnetic receding curve is straight and HCB is approximately equal to Br, and the reverting permeability Rec slope is equal to the slope of the B demagnetization curve, i.e., Rec br Hcb. The smaller the REC, the better the stability of the magnet under dynamic operating conditions.

It is worth noting that if the b demagnetization curve of the magnet is not a straight line, the reverted permeability rec of the magnet has different values at different working points, so how to design the magnet in the most stable working state is very important.

Definition of revert permeability: when the magnet is in dynamic working conditions, the external reverse magnetic field h or the demagnetization field hd inside the magnet changes periodically, and the working point d shown in the figure below also shows periodic reciprocating changes, and the trajectory of the reciprocating change of the working point d on the B demagnetization curve of the magnet is defined as the dynamic recovery line of the magnet, and the slope of the line is the recovering permeability rec. Obviously, the reverted permeability REC characterizes the stability of the magnet under dynamic working conditions, and it is also the square degree of the demagnetization curve of the permanent magnet, so it is one of the important magnetic characteristics of the permanent magnet.

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