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Soft magnetic alloy principle and main characteristics
Magnetic alloys that are easily magnetized under the action of an external magnetic field and that have a magnetic induction (magnetism) disappear after the magnetic field is removed. Hysteresis loop area is small and narrow, the coercive force (Hc) is generally lower than 10 Oe (see precision alloys). At the end of the 19th century, low-carbon steel plates were used to make motor and transformer cores. In 1900, higher magnetic silicon steel sheets quickly replaced low-carbon steels for the manufacture of power industry products. In 1917, Ni-Fe alloy appeared to meet the needs of the telephone system at that time. Later, Fe-Co alloys (1929), Fe-Si-Al alloys (1936) and Fe-Al alloys (1950) with different magnetic properties have appeared to meet specific applications. China began producing hot-rolled silicon steel sheets in 1953. In the late 1950s, research began on the use of soft magnetic alloys in magnetic materials such as Ni-Fe and Fe-Co. In the 1960s, soft magnetic alloys were mainly produced in some major magnetic materials. In the 70s, cold-rolled silicon steel strips were produced.
The main magnetic properties of soft magnetic alloys in magnetic materials are: 1 low coercive force (Hc) and hysteresis loss (Wh); 2 higher resistivity (ρ), lower eddy current loss (We); 3 initial permeability ( Μ0) and maximum permeability (μm) are high; some alloys have a constant magnetic permeability (B/H) in the low magnetic field range; 4 high saturation magnetic susceptibility (Bs); 5 some alloy hysteresis loops are rectangular The squareness is higher than the remanence/maximum magnetic susceptibility (Br/Bm). These magnetic properties are closely related to the structural state and composition of the alloy. Impurities such as carbon, sulfur, nitrogen, and oxygen in alloys are particularly detrimental to magnetism because they distort lattices, motor brushes are difficult to magnetize, and carbon and nitrogen can cause magnetic aging. Soft magnetic alloys in magnetic materials generally require large finished grain sizes in order to reduce the Hc and Wh values. In general, the magnetic properties of ferromagnetic metals vary depending on the direction of the crystal axis. For example, the magnetization of iron in the <100> direction is easy and the magnetization in the <111> direction is difficult. Therefore controlling the grain orientation can obtain better magnetic properties in a particular direction of the material. The resistivity (ρ) of iron is low, and the addition of certain alloying elements can increase the ρ value, and the effects of adding silicon and aluminum are the most obvious. Adding any alloying element (except cobalt) to iron will reduce its saturation magnetic susceptibility Bs.
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