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Introduction to Permalloy Fe-Ni alloy is the so-called permalloy, which is a very important type of soft magnetic material. It shows high magnetic permeability and low coercive force under weak magnetic field magnetization, and has good cold working properties. By controlling the composition (changing the Ni content, adding one or several alloying elements, such as Mo, Cu, Cr and Ti, etc.) and the process, a variety of permalloys with different characteristics can be obtained. There are many, which can be regarded as the most soft magnetic materials. However, its disadvantage is that it contains more precious metal Ni. Therefore, the cost is relatively high, the production equipment is huge, the process is demanding, and the magnetism is greatly affected by the environment. The Fe-Ni alloy produced in our country has a wide range of specifications and brands, and has been issued by the Ministry of Industry and Information Technology.   Permalloy annealing process precautions Compared with the one-stage annealing (1100℃×3h) in the two-stage continuous annealing (950℃×3h→1100℃×3h), the coercive force is reduced from 217.6 A/m to 8.8A/m, and the coercive force is significantly reduced and saturated. The magnetization intensity increased slightly from 74.22 emu/g to 79.34 emu/g. This shows that the two-stage continuous annealing process is beneficial to removing impurities in the alloy, purifying the alloy, thereby improving the magnetic properties of the alloy.   Permalloy preparation 1. The two-stage continuous annealing process is beneficial to remove impurities in the alloy, purify the alloy, and at the same time improve the magnetic properties of the alloy, that is, the coercive force is reduced and the saturation magnetization is increased. 2. Prolonging the holding time is beneficial to the growth of alloy grains, reducing defects within the crystal, weakening the pinning effect on domain wall movement, and making domain wall movement easier, thus improving magnetic properties. But it’s not that the longer the heat preservation time, the better. Because at high temperatures and long holding times, the reduction and oxidation of hydrogen and impurities in the furnace pollutes the atmosphere in the furnace, and the hydrogen dew point also increases with the increase in temperature, resulting in a decrease in the magnetic properties of the alloy. Therefore, the holding time is extended to 4 hours. On the one hand, it is beneficial to improve production efficiency, and on the other hand, it also obtains better soft magnetic properties. Taking various factors into account, the optimal heat treatment process for IJ79 alloy is determined as follows: raising the temperature to 950°C in the furnace, holding it for 4 hours, then raising the temperature to 1100°C, holding it for 4 hours, and finally cooling the furnace to room temperature. 3. The effect of changes in Ni content in the alloy on its magnetic properties was studied. It was found that if the change in Ni content is too small, the effect on the magnetic properties of the alloy is not significant. Therefore, during the production process, it is only necessary to ensure that the Ni content is within the composition of the standards issued by the Ministry of Metallurgy (YB129-70). 4. Add M to the alloy. The content is beneficial to increase the saturation magnetic induction intensity and reduce the coercive force. Combining various factors, we found ultra-low H. The preferred composition of the alloy is: Ni 78.00wt%, Mo 5.00wt%, Mn 0.90wt% Si 0.40wt%, Fe balance.