Ferrite magnetic material for heat-sensitive sensor

Abstract

The invention discloses a ferrite magnetic material for a heat-sensitive sensor. The ferrite magnetic material mainly contains the ingredients in percentage by weight: 34-45% of Fe2O3, 10-15% of ZnO, 5-10% of CuO, 1-3% of NiO, 0.01-0.03% of CaCO3, 0.002-0.012% of Bi2O3 and the balance of Mn3O4. The ferrite magnetic material for the heat-sensitive sensor is prepared through the steps of weighing and mixing, carrying out first-time pulping, carrying out first-time spraying granulation, prefiring, sanding, carrying out second-time spraying granulation and the like. By adopting the ingredients and the preparation method, the crystal grain of the ferrite magnetic material for the heat-sensitive sensor can be uniform, the initial magnetic permeability can be improved, the magnetic core sintered density can be improved, and the range of Curie temperature can be narrowed; the volatilization of zinc oxide can be inhibited, the specific temperature coefficient is increased, the maximum slope of magnetic permeability temperature change is high, and the temperature control accuracy is high; due to first-time pulping, namely wet mixing, all main ingredients can be mixed more uniformly, and gluing is more uniform.

Description

technical field [0001] The invention relates to a ferrite material, in particular to a ferrite magnetic material for a thermal sensor. Background technique [0002] Thermal sensors are a class of sensors used to detect thermal quantities (mainly temperature) and to achieve process control related to thermal processes. In addition to the function of detecting thermal quantities such as temperature, thermal sensors are often used to help realize automatic control related to thermal processes. The thermal sensor is one of the temperature sensors. Although there are many types of temperature sensors at present, it is still generally believed that the thermal sensor is the most marketable, potential and promising product. [0003] The Chinese Invention Patent No. 201110174152.X published on February 22, 2012 is titled "A Soft Magnetic Ferrite Thermal Core and Its Manufacturing Method". In this patent, the composition (percentage by weight) of the soft ferrite thermosensitive co...

AI Technical Summary

Problems solved by technology

[0006] 1. When Bi 2 o 3 When the content is greater than 0.01%, the initial permeability and density of the soft ferrite thermal core will also decrease, and the core will become brittle and brittle

[0007] 2. Although the fluctuation range of the Curie temperature becomes smaller, the maximum slope of the temperature change of the magnetic permeability is still small at the Curie temperature point, such as only 100-200 / °C, so the accuracy of temperature control is still low

[0008] 3. During sintering, ZnO volatilizes seriously, and the application range of soft ferrite heat-sensitive magnetic materials to frequencies is narrow;

[0009] 4. In this application, the soft magnetic ferrite heat-sensitive magnetic powder is directly rolled and pre-fired after the ingredients are mixed and added to the PVA. The PVA is directly added to the dry powder of the raw material, which is easy to make the dry powder agglomerate, resulting in uneven glue addition. Powder with little glue added or dry powder without glue will be difficult to form flakes in the flaking machine. Not only can the forming pressure not be reduced, but the dry powder will be rolled finer and the amount of fine powder will increase. On the one hand, it will cause sintering The wall of the kiln is seriously stuck; on the other hand, it will also greatly reduce the qualified rate of the final powder product

Since this patent application adopts water mixing, that is, a wet mixing process, the powder can be mixed more uniformly. However, the mixed powder is directly pre-calcined, and the mixed powder is still powdery. High, the magnetic properties of the pre-fired powder are low, such as the maximum slope of the temperature change of the magnetic permeability is only 137 / °C, and the density is only 4.5g / cm 3 Or so, the core is still brittle and brittle after sintering