Key technology of heat treatment of amorphous alloy iron core strip

At present, the amorphous alloy core adopts an approximately rectangular lap winding structure. The internal stress of the formed core is very large and the magnetic properties are seriously damaged. These stresses must be eliminated by heat treatment and annealing. Heat treatment annealing process is the most critical and difficult process to control in the whole manufacturing process of amorphous alloy core. The domestic amorphous alloy strip has a transverse arc, and its internal stress is greater than that of the imported strip. In addition, due to the different composition, it is more sensitive to the temperature during heat treatment. Therefore, the formulation of appropriate heat treatment annealing process is very important to the final core performance and quality of domestic amorphous alloy strip.

1、 Heat treatment annealing temperature. The appropriate annealing temperature of the core should not only eliminate the internal stress of the core and restore its magnetic properties, but also reduce the brittleness of the amorphous alloy strip and the risk of crushing in the subsequent operation of the core. The results show that the best annealing temperature for the core of domestic amorphous alloy strip is 375 ~ 380 ℃.

2、 Heat treatment holding time. The experimental results show that the unit excitation power decreases with the extension of annealing time, while the unit no-load loss of core increases with the extension of annealing time, and the brittleness of core strip also increases with the increase of annealing time. Therefore, the best holding time must be selected according to the user's requirements for core performance.

3、 Heat treatment protective atmosphere. The iron core is easily oxidized during high temperature heat treatment and annealing. After the core surface is oxidized, in addition to the rust on the surface, the no-load loss of the core will increase significantly. Therefore, the core must be protected by atmosphere during the whole heat treatment and annealing process. At present, the commonly used process shielding gas is nitrogen or argon.

4、 Heating and cooling rate. Because the iron core is subject to multiple loading and batch heat treatment in batch production, the reasonable heating and cooling rate not only affects the performance results of amorphous alloy iron core, but also affects the production efficiency and production cost. Generally speaking, the faster the heating rate, the greater the dispersion. However, the experiments show that the temperature dispersion of domestic amorphous alloy strip core is small when it reaches the high temperature zone and approaches the optimal annealing temperature point, which can be almost controlled within 3 ℃. Therefore, in the heating stage, the domestic amorphous alloy strip core can be heated directly and rapidly. In addition, the fast cooling speed is beneficial to reduce the no-load loss of the core, but it will increase the excitation power of the core at the same time. Therefore, the best cooling rate needs to accumulate empirical data to make the best choice.

5、 Applied magnetic field. The formed amorphous alloy core needs additional DC magnetic field to obtain good domain orientation during annealing, so as to improve its magnetic properties. The test shows that the field strength of domestic amorphous alloy strip core during annealing needs about 2000a / m or the magnetic field current is 1400A, which can ensure the core material saturation during annealing, so as to achieve the best annealing effect.