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High magnetic permeability and low coercivity of low-frequency soft magnetic materials

A low-frequency soft magnetic material with high magnetic permeability and low coercivity in a weak magnetic field. Early iron-nickel alloys were used for telephone communications, and later a method of heat treatment and vacuum smelting was used to greatly improve the properties of the alloy. The magnetic permeability of Ni78% Fe-Ni alloy in the weak magnetic field is about 10-20 times higher than that of silicon steel. It is widely used in sensitive relays, magnetic shielding, telephone and radio transformers, precision AC and DC meters, and current transformers (see Transformer). By adding elements such as molybdenum, manganese, cobalt, copper, and chromium to the iron-nickel alloy, a ternary and quaternary iron-nickel alloy having a larger initial permeability μi and a maximum permeability μm can be obtained. Iron-nickel alloys have a narrow and steep hysteresis loop, have a large magnetic permeability and a small coercive force in a weak magnetic field, but its resistivity is not large, and it is only suitable for working in a frequency range below 1 MHz. Otherwise, the eddy current loss is too high. Iron-nickel alloys have good processing properties and can be made into a variety of components with complex shapes and precise dimensional requirements. However, its magnetic properties are relatively sensitive to mechanical stress, and process factors have a greater influence on the soft magnetic material energy. For example, stamping will decrease the μb, so the product performance consistency is not easy to meet. Iron-nickel alloys have high costs. The characteristics and uses of commonly used iron-nickel alloys are listed in the table. In addition to Invar, Kovar, and Permalloy, iron-nickel alloys include the following alloys: (1) 68Fe+27Ni+5Mo and 53Fe+42Ni+5Mo, which have a very high coefficient of thermal expansion. Thermostat bimetal, heat exchangers and various temperature adjustment devices. (2) 46Ni+54Fe, known as platinum, has the same coefficient of expansion as platinum, has good corrosion resistance, and can replace platinum in some applications. (3) 42Ni+58Fe, which can be used as vacuum tube sealing wire instead of platinum. (4) 36NJ+12Cr+52Fe, a constant elastic alloy with a thermo-elasticity coefficient equal to zero, commonly used as a hairpin, watch balance, and precision instrument parts. Melting method ingots, pressure processing into the material.

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