Heat Treatment Of Nanocrystalline Core

The heat treatment process (annealing process) of nanocrystalline core strip plays a very key role in the magnetic properties of nanocrystalline core strip. The purpose of annealing is to eliminate the stress of the strip during spraying and winding, so that the magnetic properties of the strip can be restored to the original level as far as possible. At the same time, in the annealing process by adjusting the annealing temperature, time, magnetic field and other factors can get different performance indicators, in order to meet the performance requirements of different products, which is incomparable to other soft magnetic materials.

Annealing mode:
1, Ordinary annealing using vacuum or inert gas (argon or nitrogen) protection, annealing process does not apply magnetic field. Ordinary annealing treatment is generally applied to the core of transformers, PFC inductors and filter inductors.

2. Magnetic field annealing is protected by vacuum or inert gas (argon or nitrogen), and certain magnetic field is applied in the process of temperature rise, heat preservation and cooling. It is mainly divided into longitudinal magnetic field annealing and transverse magnetic field annealing.

Longitudinal magnetic field annealing:
In order to improve the permeability of the nanocrystalline core and obtain the rectangular hysteresis loop, a longitudinal magnetic field should be applied in the annealing process. The magnetic field application method is to apply a magnetic field along the direction of the used magnetic circuit to the nanocrystalline core (generally, a energized copper rod is applied through the core or the wire is wound). Longitudinal magnetic annealing is mainly applied to nanocrystalline core of distribution transformer, magnetic amplifier, saturated inductor and so on.

Transverse magnetic field annealing:
In order to obtain constant permeability, obtain flat hysteresis loop, and improve the frequency characteristics of the iron core, a transverse magnetic field should be applied in the annealing process. The magnetic field application method: apply a magnetic field along the axial direction to the nanocrystalline iron core (generally, the nanocrystalline iron core is placed in a energized solenoid, so that the axial direction of the iron core is parallel to the magnetic field direction). Transverse magnetic annealing is widely used in common mode inductors, switching power transformers and other nanocrystalline cores.

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