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Heat treatment of amorphous strip

Heat treatment of amorphous strip


Amorphous alloys have the advantages of high magnetic induction, low coercivity, and inferior damage, so they are widely used in power transformers with high efficiency, energy saving, and environmental protection.

The amorphous alloy cores up to now are considered suitable and use a nearly rectangular lap winding structure. The formed core has a large external stress, and the special magnetic properties are severely damaged. The heat treatment and annealing capability must be used to eliminate these stresses. The heat treatment annealing process is the most critical and difficult to control process in the whole manufacturing process of the curved-vertical alloy core. The transverse direction of the domestic amorphous alloy strip is arc-shaped, and its external stress is larger than that of the imported strip. In addition, the composition is different, and the sensitivity to the temperature during heat treatment is stronger. Because of this, it is formulated Suitable heat treatment annealing process is crucial to the final iron performance and quality of domestic amorphous alloy strips.

  1. Heat treatment annealing temperature. An appropriate iron core annealing temperature not only guarantees the elimination of the external stress of the iron core and reduces its special magnetic properties, but also reduces the brittleness of the amorphous alloy strip and reduces the risk of breaking the iron core during subsequent operations. Attempts have shown that the final annealing temperature of domestic amorphous alloy strip cores is better to be controlled at 375-380°C.

  2. Warm-keeping time for heat treatment. Experiments show that the unit excitation power decreases with the extension of the annealing time, and the unit no-load damage loss of the core increases with the extension of the annealing time, and the brittleness of the core strip also increases with the increase of the annealing time. Because of this, be sure to choose the best warming time according to the user's requirements for iron temperament.

  3. Heat treatment tries its best to take care of the atmosphere. The iron core is easily oxygenated during high temperature heat treatment annealing. After the surface of the iron core is oxygenated, in addition to the rust on the surface, the more important thing is that the no-load damage of the iron core will increase. Because of this, the iron core must be considered appropriate during the entire heat treatment annealing process, and the atmosphere must be taken care of as much as possible. The processes commonly used up to now try their best to take care of the gas being nitrogen or argon.

  4. increase and decrease the temperature speed gently. Because iron cores are mass-produced with multiple loadings and batch heat treatments, a reasonable increase and decrease of temperature speed will not only affect the final result of the performance of amorphous alloy cores, but also affect the production rate and production capital. Generally speaking, the faster the temperature rises, the greater the dispersion. However, experiments have shown that the temperature dispersion of domestic amorphous alloy strip cores when they reach the high temperature zone and close to the annealing temperature is small, and can almost be controlled within 3°C. Therefore, in the stage of temperature rise, the domestic amorphous alloy strip core can be directly heated up quickly. In addition, the speed of lowering the temperature is fast, which is good for reducing the no-load damage of the iron core, but the excitation power of the iron core is increased in the same special situation. Therefore, reducing the temperature speed requires accumulating empirical values for selection.

  5. Apply a magnetic field. The formed amorphous alloy core must be annealed with a DC magnetic field to obtain a satisfactory magnetic domain orientation, so as to improve its special magnetic properties. Attempts have shown that the field strength during annealing of the domestic amorphous alloy strip core needs to be about 2000A/m or the magnetic field current volume is 1400A to ensure that the core material reaches the high limit during annealing, which can achieve the annealing effect.

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