Classification and characteristics of soft magnetic materials


(1) Pure iron and low carbon steel. The carbon content […]

(1) Pure iron and low carbon steel. The carbon content is less than 0.04%, including electromagnetic pure iron, electrolytic iron and carbonyl iron. It is characterized by high saturation magnetization, low price and good processing performance. However, its low resistivity and large eddy current loss under alternating magnetic field are only suitable for static use, such as manufacturing electromagnet core, pole piece, relay and speaker magnet. Conductor, magnetic shield, etc.
(2) Iron-silicon alloy. The silicon content is 0.5% to 4.8%, and is generally used as a thin plate, commonly known as silicon steel sheet. When silicon is added to pure iron, the magnetic properties of the magnetic material change with the use time. As the silicon content increases, the thermal conductivity decreases, the brittleness increases, the saturation magnetization decreases, but the resistivity and magnetic permeability are high, and the coercive force and eddy current loss are reduced, so that it can be applied to the field of communication, manufacturing motors, transformers, The core of relays, transformers, etc. (3) Iron-aluminum alloy. Containing 6% to 16% aluminum, it has good soft magnetic properties, high magnetic permeability and electrical resistivity, high hardness and good wear resistance, but it is brittle and is mainly used to manufacture iron for small transformers, magnetic amplifiers, relays, etc. Core and magnetic head, ultrasonic transducer, etc.
(4) Iron silicon aluminum alloy. It is obtained by adding silicon to a binary iron aluminum alloy. Its hardness, saturation magnetic induction, magnetic permeability and electrical resistivity are both high. The disadvantage is that the magnetic properties are sensitive to composition fluctuations, brittleness and poor processing properties. Mainly used for audio and video heads.
(5) Nickel-iron alloy. Nickel content of 30% to 90%, also known as permalloy, through the alloying element ratio and appropriate process, can control the magnetic properties, to obtain high permeability, constant magnetic, moment magnetic and other soft magnetic materials. It has high plasticity and is sensitive to stress and can be used as pulse transformer material, inductor core and functional magnetic material.
(6) Iron-cobalt alloy. The cobalt content is 27% to 50%. Has a high saturation magnetization and low resistivity. Suitable for the manufacture of pole shoes, motor rotors and stators, small transformer cores, etc.
(7) Soft ferrite. Non-metallic ferrimagnetic soft magnetic material. High resistivity (10-2 ~ 1010 Ω · m), low saturation magnetization than metal, low price, widely used as inductance components and transformer components (see ferrite).
(8) Amorphous soft magnetic alloy. A long-range ordered, grain-free alloy, also known as metallic glass, or amorphous metal. Its magnetic permeability and resistivity are high, its coercive force is small, it is not sensitive to stress, there is no magnetocrystalline anisotropy caused by crystal structure, and it has characteristics of corrosion resistance and high strength. In addition, its Curie point is much lower than that of crystalline soft magnetic material, and the power loss is greatly reduced. It is a new type of soft magnetic material being developed and utilized.
(9) Ultrafine crystal soft magnetic alloy. A soft magnetic material discovered in the 1980s. It consists of a crystalline phase of less than 50 nm and an amorphous grain boundary phase. It has better overall properties than crystalline and amorphous alloys. It has high magnetic permeability, low coercive force, low iron loss, and saturation. High magnetic induction and good stability. The main research is now iron-based ultrafine crystal alloy.