Sintered Ferrite Y30BH Pump Magnet
Sintering is an exogenous factor that determines the properties of MnZn ferrite materials。For a good formulation, it is one of the key factors to design the sintering process and control the sintering process accurately in order to prepare the ferrite with good performance.
In the sintering process, as well as increasing the sintering temperature, solid instead should fully promote the ferrite, ferrite grain full uniform grew up, and to control the sintering temperature not too high, so as not to cause a discontinuous, growing grains can reduce magnetic ferrite materials.
For MnZn ferrite materials in the sintering process, but also control the sintering atmosphere, which should not only control the Mn and Fe ion base, and to control the generation of ferrite contains a certain amount of Fe2 + ion, prevent the Zn2 + ions in high temperature and evaporation.
The sintering process of MnZn ferrite consists of the highest sintering temperature, the heating process, the cooling mode, the highest heat preservation time and the sintering atmosphere.
Sintering temperature and holding time is the most critical in ferrite sintering temperature curve, it directly affects the material internal solid phase reaction is completely, grain size and integrity, and sintering temperature and holding time is between mutual conditionality, to a certain degree of mutual compensation.
The maximum sintering temperature and heat preservation time of the billet prepared by different powder making processes are different for different formulations.
The effects of maximum sintering temperature and heat preservation time on magnetic energy of materials were studied by selecting the same formula and the same batch of samples prepared by the same powder making process.
For the same batch of sample billets, the sintering temperature and heat preservation time were tested in the same atmosphere according to different sintering temperature and heat preservation time (the lifting and cooling methods were the same).
Samples because the sintering temperature and holding time is mainly to the solid phase reaction speed and degree of influence, resulting in grain size and uniformity, porosity of how many there are differences and existing form, eventually leading to the performance of the samples.
When the sintering temperature is low, the ferrite grain size is small, the grain boundary is thick, the density is low, the porosity is high, the grain uniformity is poor, so the magnetic permeability is low and the magnetic energy is poor. With the increase of sintering temperature, solid phase reaction to continue and grain grew older, tend to be more uniform grain size, porosity, porosity, solid phase reaction tend to be more complete, sintered density increased, grain boundary internal stress is small, so the permeability increases.
To extend the heat preservation time, to some extent, it is similar to the mechanism of increasing the sintering temperature, that is, promoting the process of solid-phase reaction. However, it is found from the above experiments that, on the premise that the solid inverse should be basically completed, it is more effective to extend the heat preservation time appropriately at a relatively good sintering temperature than to increase the sintering temperature simply. Because of increasing sintering temperature, solid phase reaction speed will accelerate, makes the grain growth speed is not easy to control, thus prone to secondary grain growth in material, results in uneven grain, magnetic would decline. And at relatively low sintering temperature appropriately extend the time of heat preservation, can make solid phase reaction speed is not fast, and can guarantee the solid phase reaction to adequately, make grain growth more complete, grain boundary clear, so the material within appropriate and uniform grain size, eventually get samples with better comprehensive properties.