Key technology of heat treatment of domestic amorphous alloy core strip

Amorphous alloys with high saturation magnetic flux density, low coercivity, low loss, it is highly efficient, energy saving, environmentally friendly effects are widely used in power transformers. However, before 2009, the amorphous strip used in amorphous alloy transformers in the market of our country was almost all produced by Japan Hitachi Metals. In 2010, China's Aetna technology company with independent intellectual property rights of 10,000 tons of amorphous alloy strip production line put into operation, breaking the passive import of amorphous raw materials to the passive situation, speeding up the development of low-carbon economy in China's power industry.

The current amorphous alloy core using a nearly rectangular lap-wound structure, the core shape of the internal stress is very large, severely damaged the magnetic properties, annealing must be annealed to eliminate these stresses. Annealing annealing process is the most critical and most difficult to control the entire production process of amorphous alloy core. The domestically produced amorphous alloy strip is arc-shaped in the horizontal direction, and its internal stress is larger than that of the imported strip. In addition, with different compositions, it is more sensitive to the temperature during the heat treatment. Therefore, the appropriate annealing process for heat treatment is developed. The final core performance and quality of the domestic amorphous alloy strip is of crucial importance.

First, heat treatment annealing temperature. Suitable core annealing temperature, not only to ensure that the core to eliminate the inherent stress and restore its magnetic properties, and to be able to minimize the brittleness of amorphous alloy strip to reduce the risk of subsequent operation in the core crushing. Tests show that the final annealing temperature of the domestic amorphous alloy strip core is controlled at 375 ~ 380 ℃ for the best.

Second, heat treatment holding time. Experiments show that the unit excitation power decreases with the extension of the annealing time, and the unit no-load loss increases with the annealing time, and the brittleness of the core strip also increases with annealing time . Therefore, the user must be based on the core performance requirements, choose the best holding time.

Third, heat treatment to protect the atmosphere. Iron core is easily oxidized when annealed at high temperature. Iron core surface is oxidized, in addition to the surface of the rust, the more important will lead to significantly increase the core no-load loss. Therefore, the core in the entire heat treatment annealing process must be used to protect the atmosphere. Currently used process protection gas is nitrogen or argon.

Fourth, heating and cooling rate. As the iron core in the mass production are multiple loading, batch heat treatment, so a reasonable rate of heating and cooling, not only affect the performance of amorphous alloy core results, but also affect the production efficiency and production costs. In general, the faster the heating rate, the greater the dispersion. However, the experiment shows that the temperature dispersion of the domestic amorphous alloy strip core when reaching the high temperature zone and close to the optimal annealing temperature is small, and can be controlled within 3 ° C. Therefore, in the warming stage, the domestic amorphous alloy strip core can be quickly heated. In addition, the cooling rate is fast, for reducing the core no-load loss is beneficial, but at the same time will increase the core of the excitation power. Therefore, the best cooling rate need to accumulate empirical data to make the best choice.

Five, plus magnetic field. After the formation of amorphous alloy core, in the annealing need to add DC magnetic field to obtain good magnetic domain orientation, in order to improve its magnetic properties. The test shows that the field strength of the domestic amorphous alloy strip core annealed at about 2000A / m or the field current size at 1400A can ensure the core material to be saturated during annealing, so as to achieve the best annealing effect.