Magnetically soft ferrite thermosensitive magnetic core and preparation method thereof

Abstract

The invention discloses a magnetically soft ferrite thermosensitive magnetic core and a preparation method thereof. The magnetically soft ferrite thermosensitive magnetic core is characterized by comprising the following components in percentage by weight: 15 to 20 percent of ZnO, 5 to 8 percent of MgO, 5 to 10 percent of CuO, 0.001 to 0.2 percent of Bi2O3 and the balance of Fe2O3 and unavoidable impurities. The preparation method comprises the following steps of: proportioning and mixing 15 to 20 percent of ZnO, 5 to 8 percent of MgO, 5 to 10 percent of CuO and the balance of Fe2O3 and unavoidable impurities; rolling into pieces; pre-sintering; sanding primarily and sanding secondarily; granulating in a spraying mode; shaping in a pressing mode; sintering; and grinding and polishing to form the magnetic core. In the method, the Bi2O3 which is 0.001 to 0.2 weight percent based on that of a pre-sintering material is added in the procedure of sanding secondarily, so that an A-B superexchange function can be realized in the sintering process, a close crystalline structure which is similar to NiZn ferrite is formed, a sintering temperature is lowered, the curie temperature fluctuation of the magnetic core is reduced, the fluctuation range of the magnetic core is narrow, a magnetically sensitive thermal protection switch used by the magnetic core has high temperature control sensitivity, and the requirement of the magnetically sensitive thermal protection switch on the magnetic core is met.

Description

technical field [0001] The invention relates to a soft ferrite heat-sensitive magnetic core and a manufacturing method thereof, belonging to the field of oxide magnetic material manufacturing. Background technique [0002] At present, thermal magnetic cores are widely used in magnetic thermal protection switches of household appliances with a wide temperature control range, such as rice cookers and electric water heaters. The temperature-sensitive magnetic core material generally uses MgCuZn ferrite high-conductivity material, the magnetic permeability ui of this material is 1000-1350, and the fluctuation range of Curie temperature Tc of this material is 90 ° C ~ 100 ° C. [0003] The composition (percentage by weight) of the above-mentioned MgCuZn ferrite thermosensitive magnetic core contains 15% to 20% of ZnO, 5% to 8% of MgO, 5% to 10% of CuO, and the rest is Fe 2 o 3 And unavoidable impurities, and adopt the following method to prepare: it will contain ZnO 15% ~ 20%, ...

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Problems solved by technology

However, the Curie temperature characteristic of this MgCuZn ferrite thermal core is Figure 4 As shown in the middle curves N1 and N2, the abscissa in the figure represents the temperature t (°C), and the ordinate represents the initial magnetic permeability ui, from Figure 4 It can be seen from the figure that the fluctuation range of Curie temperature Tc of this material is 90℃~100℃. Therefore, this magnetic core is only suitable for household appliances. The temperature control range of household appliances is wide, and the temperature control range of its magnetic thermal protection switch Large, the control temperature range is 50 ℃ ~ 80 ℃, the range is large, and the temperature control sensitivity of the magnetic thermal protection switch is poor; the core needs a higher sintering temperature in the blank sintering process, and its sintering temperature is 1200 ℃ ~ 1240 ℃ , due to the high sintering temperature, Zn in the crystal structure 2+ The ions are volatile, causing the instability of its electromagnetic properties, and the product qualification rate is lower than 75%.

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