Magnetic material knowledge sharing from an automatic batching manufacturer of magnetic materials

Published Time:

2022-04-28

Matter is primarily composed of molecules, which in turn are made up of atoms. Atoms consist of a nucleus and electrons. Within the atom, electrons revolve and rotate around the nucleus, both of which generate magnetism. However, in most substances, the directions of electron movement are diverse and chaotic, resulting in the mutual cancellation of magnetic effects. Therefore, most substances, under normal conditions, appear to be non-magnetic.

1. Why do magnets have magnetism?

Matter is mainly composed of molecules, molecules are composed of atoms, and atoms are composed of atomic nuclei and electrons. Inside atoms, electrons revolve and rotate around the atomic nucleus, both of which produce magnetism. However, in most substances, the directions of electron movement are different and chaotic, and the magnetic effects cancel each other out. Therefore, most substances do not appear to have magnetism under normal circumstances.

Ferromagnetic materials such as iron, cobalt, nickel, or ferrite are different. The electrons inside them can spontaneously arrange and combine in a small range through the spin system to form a spontaneous magnetization region, which is called a magnetic domain. After the ferromagnetic material is magnetized, the magnetic domains inside are neatly arranged and aligned in the same direction, strengthening the magnetism, thus forming a magnet. The process of a magnet attracting iron is the process of magnetizing the iron block. The magnetized iron block and the magnet attract each other due to the interaction between different polarities, and the iron block firmly "sticks" to the magnet.

2. How to define the performance of a magnet?

There are three main performance parameters to determine the performance of a magnet:

Remanence Br: When a permanent magnet is magnetized to technical saturation and the external magnetic field is removed, the remaining Br is called magnetic induction intensity.

Coercivity Hc: The intensity of the reverse magnetic field required to reduce the B of a permanent magnet magnetized to technical saturation to zero is called magnetic induction coercivity, or coercivity for short.

Energy product BH: Represents the magnetic energy density established in the air gap (space between the two magnetic poles of the magnet), that is, the magnetostatic energy per unit volume of the air gap.

3. How to classify metallic magnetic materials?

Metallic magnetic nanomaterials can be divided into two categories: permanent magnet materials and soft magnetic materials. Materials with intrinsic coercivity greater than 0.8kA/m are usually called permanent magnet materials, and materials with intrinsic coercivity less than 0.8kA/m are called soft magnetic materials.

4. Several commonly used magnets are ranked in order of magnetic force from largest to smallest: neodymium iron boron magnets, samarium cobalt magnets, alnico magnets, and ferrite magnets.

5. Analogy of prices of different magnetic materials?

Ferrite: Low and medium performance, lowest price, good temperature characteristics, corrosion resistance, good performance-price ratio

NdFEB: Highest performance, good price, high strength, not heat-resistant, corrosion-resistant

Samarium Cobalt: High performance, highest price, brittle, excellent temperature characteristics, corrosion-resistant

Alnico: Medium-low performance, moderate price, excellent temperature characteristics, corrosion-resistant, poor anti-interference ability

Samarium cobalt, ferrite, and neodymium iron boron can be made by sintering and bonding. Sintered magnets have high magnetism and poor formability, while bonded magnets have good formability but much lower performance. Alnico alloys can be made by casting and sintering. Cast magnets have high performance and poor formability, while sintered magnets have low formability.

Tags:

Some issues with PVC centralized feeding

Knowledge of automatic batching of magnetic materials - Magnetic material cognition