Method for regulating the loss valley temperature of manganese-zinc ferrite

Abstract

The application provides a method for regulating the loss valley point temperature of manganese-zinc ferrite, which comprises the following steps: (1) after the manganese-zinc ferrite powder is pressed into a shape, sintering is carried out under oxygen partial pressures P0, P1 and P2, and the corresponding loss valley point temperatures T0, T1 and T2 are measured; (2) an initial compensation coefficient k is calculated; (3) the sintering oxygen partial pressure P is calculated by P=P0+(Ttarget-T0) / k, sintering is carried out under the oxygen partial pressure, and the actual valley point temperature Tactual of the obtained product is measured; (4) the data points are combined, a linear relationship is fitted by using the least square method, and a revised compensation coefficient k' is obtained; and (5) the sintering oxygen partial pressure is calculated by using the revised compensation coefficient k', the manganese-zinc ferrite powder is pressed into a shape, sintering is carried out under the oxygen partial pressure P', and the manganese-zinc ferrite with a target loss valley point temperature is prepared. By means of the method of "calculation-compensation", the quantitative regulation of the valley point temperature can be realized without changing the powder ratio of the manganese-zinc ferrite.

Description

Technical Field

[0001] This invention relates to the field of manganese-zinc ferrite magnetic material preparation technology, and in particular to a method for controlling the loss valley temperature of manganese-zinc ferrite. Background Technology

[0002] MnZn ferrite cores are core magnetic components in electronic devices such as switching power supplies, transformers, and inductors, and their performance directly determines the energy conversion efficiency and electromagnetic compatibility of the entire system. These cores require low power loss, good temperature stability, and long-term reliability over a wide temperature and frequency range to adapt to diverse applications in consumer electronics, industrial power supplies, communication equipment, new energy, and automotive electronics. Especially in recent years, with the rapid development of electric vehicles, on-board chargers, and DC-DC converters, cores are often exposed to high-temperature environments such as engine compartments, placing extremely stringent requirements on wide-temperature-range low-loss characteristics. In applications requiring wide-temperature operation, such as automotive and power supplies, the ideal loss-temperature characteristic is a bathtub-shaped loss-temperature curve for the core, with the lowest loss point (valley) located on the high-temperature side of the entire operating temperature range, for example, between 100 and 120°C. This is mainly because the magnetocrystalline anisotropy constant and magnetostriction coefficient of MnZn ferrite change with temperature; when the anisotropy constant approaches zero, the loss reaches a minimum, forming the valley. If the valley point temperature is too low, the core loss will increase sharply under high temperature conditions due to the deviation from the zero anisotropy point, causing the core to heat up, efficiency to decrease, and even leading to thermal runaway of the system. Therefore, accurately controlling the valley point temperature to the high temperature side is the core to ensure high temperature and low loss operation.

[0003] The conventional manufacturing process for MnZn ferrite cores typically involves: pre-calcined powder granulation → pressing and molding → high-temperature sintering. First, iron, manganese, and zinc oxide raw materials are mixed and pre-calcined, undergoing a preliminary solid-state reaction to generate a ferrite phase. The resulting powder is then pulverized to obtain pre-calcined powder. To improve the powder's flowability and formability, an aqueous solution of organic binders such as PVA (polyvinyl alcohol) is usually added during the granulation stage. Granulated powder with good filling properties and uniform particle size is produced through methods such as spray granulation. The granulated powder is then pressed into green bodies of the desired shape using an automatic press and fed into a high-temperature sintering furnace for sintering under precisely controlled temperature and atmosphere profiles. During the low-temperature stage of sintering (approximately 300-500°C), the organic components such as PVA gradually decompose and volatilize, providing a clean grain boundary environment for subsequent solid-state diffusion and densification. The final microstructure of the magnetic core, including grain size, grain boundary characteristics, porosity distribution, cation valence state, and Fe ion concentration, is strongly dependent on the sintering process parameters. Therefore, the control of key properties such as core loss, initial permeability, and loss valley temperature is largely determined by the sintering regime.

[0004] In existing technologies, the mainstream method for controlling the loss valley temperature of MnZn ferrite is to adjust the main formulation ratio or add additives such as Co. Studies have confirmed that precisely controlling the ratio of Fe2O3, ZnO, Mn3O4, and Fe... 2+ The content of sintering powder can be used to set the valley point temperature. However, for companies that directly use purchased granulated powder in their production, it is difficult to significantly change the valley point temperature at the formulation level. The valley point temperature of the product is often too low, failing to meet the requirements of high-temperature applications. Furthermore, the inconsistencies between different batches of purchased powder make it impossible to achieve consistently high valley point temperatures solely through a uniform sintering process. Currently, there is still a lack of an industrial method for purchasing granulated powder that can quantitatively and controllably shift the valley point temperature towards the high-temperature range using sintering parameters. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention provides a method for regulating the valley temperature of manganese zinc ferrite without changing the raw material ratio of manganese zinc ferrite. The valley temperature can be quantitatively regulated by the "calculation-compensation" method, and the difference between batches of powder can be solved by the self-correction algorithm based on actual measurement feedback.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] This invention provides a method for regulating the valley point temperature of manganese-zinc ferrite loss, the method comprising the following steps:

[0008] (1) After the manganese zinc ferrite powder is pressed into shape, it is sintered under oxygen partial pressures P0, P1 and P2 respectively, and the loss valley temperature T0, T1 and T2 corresponding to the manganese zinc ferrite are measured; wherein, P1 and P2 are symmetrically set on both sides of P0, that is, P0- P1=P2- P0.

[0009] (2) Calculate the initial compensation coefficient k according to the formula k = (T1 - T2) / (P1 - P2);

[0010] (3) Based on the target valley point temperature T, calculate the sintering oxygen partial pressure P by P = P0 + (T_target – T0) / k. After pressing the manganese-zinc ferrite powder into shape, sinter it according to this oxygen partial pressure and measure the actual valley point temperature T_actual of the obtained product.

[0011] (4) Combine the data points (P, T_real) with (P0, T0), (P1, T1), and (P2, T2) from step (1), fit the linear relationship using the least squares method, and obtain the revised compensation coefficient k', with the formula:

[0012]

[0013] In the formula, n is the number of data points involved in the fitting, and Pi and Ti are the oxygen partial pressure and measured valley temperature of each data point;

[0014] (5) Using the revision factor k', the sintering oxygen partial pressure is calculated according to P' = P0 + (T_standard – T0) / k'; after the manganese-zinc ferrite powder is pressed into shape, it is sintered under the oxygen partial pressure P' to obtain manganese-zinc ferrite with the target loss valley temperature.

[0015] This invention establishes an initial compensation coefficient k through a symmetrical experimental design (P1 and P2 are symmetrically distributed on both sides of P0), establishing a linear relationship between the change in oxygen partial pressure and the movement of the valley temperature, thereby achieving accurate calculation of "target temperature → required oxygen partial pressure". Then, through experimental feedback and least squares fitting, the initial coefficient k is upgraded to a revised compensation coefficient k', making the compensation coefficient more accurate and achieving precise quantitative control of the valley temperature of manganese-zinc ferrite loss.

[0016] This invention provides a method for controlling the valley point temperature without relying on formula adjustments and based entirely on sintering parameter control. It can quantitatively achieve the directional movement of the valley point temperature for different batches of powder, so that the valley point temperature accurately reaches the target range.

[0017] In this invention, P0 refers to the oxygen partial pressure in the conventional preparation process of manganese-zinc ferrite, and the numerical parameter can be selected according to the actual situation.

[0018] As a preferred embodiment of the present invention, the manganese-zinc ferrite powder comprises Fe2O3, ZnO and MnO.

[0019] Preferably, the mass ratio of Fe2O3, ZnO and MnO in the manganese-zinc ferrite powder is (66-70):(5-9):(20-24), for example, it can be 66:5:20, 70:9:24, 66:5:24, 70:9:20 or 68:8:22, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] As a preferred embodiment of the present invention, the manganese-zinc ferrite powder further includes additives.

[0021] Preferably, the additive includes silicon dioxide and / or calcium carbonate.

[0022] Preferably, the mass percentage of additives in the manganese-zinc ferrite powder is 2.2%-3.0%, for example, it can be 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9% or 3.0%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] As a preferred technical solution of the present invention, the pressing pressure is 370-390 MPa, for example, it can be 370 MPa, 374 MPa, 378 MPa, 382 MPa, 386 MPa or 390 MPa, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] As a preferred technical solution of the present invention, the sintering temperature is 1260-1350℃, for example, it can be 1260℃, 1270℃, 1280℃, 1290℃, 1300℃, 1310℃, 1320℃, 1330℃, 1340℃ or 1350℃, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0025] As a preferred technical solution of the present invention, the holding time for sintering is 320-400 min, for example, it can be 320 min, 330 min, 340 min, 350 min, 360 min, 370 min, 380 min, 390 min or 400 min, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] As a preferred technical solution of the present invention, the heating rate of the sintering is 1.63-5.00 ℃ / min, for example, it can be 1.63 ℃ / min, 2.00 ℃ / min, 2.50 ℃ / min, 3.00 ℃ / min, 3.50 ℃ / min, 4.00 ℃ / min, 4.50 ℃ / min or 5.00 ℃ / min, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0027] As a preferred technical solution of the present invention, the oxygen partial pressure P0 is in the range of 1.5%-3.5%, for example, it can be 1.5%, 2.0%, 2.5%, 3.0% or 3.5%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] As a preferred technical solution of the present invention, the oxygen partial pressure P1 is in the range of 0.5%-3.0%, for example, it can be 0.5%, 1.0%, 1.5%, 2.0%, 2.5% or 3.0%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] As a preferred technical solution of the present invention, the oxygen partial pressure P2 is in the range of 2.5%-4.5%, for example, it can be 2.5%, 3.0%, 3.5%, 4.0% or 4.5%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0031] (1) The method for regulating the valley temperature of manganese zinc ferrite provided by the present invention can achieve quantitative regulation of valley temperature by only sintering process parameters (oxygen partial pressure), without changing the powder ratio of manganese zinc ferrite, and is simple to operate and easier to implement.

[0032] (2) The method for regulating the temperature of the loss valley point of manganese-zinc ferrite provided by the present invention upgrades the initial k coefficient to the revised compensation coefficient k' through actual measurement feedback and least squares fitting, which allows the method to continuously accumulate data and the compensation coefficient to become more and more accurate, and can improve the process instability caused by batch differences.

[0033] (3) The method for regulating the valley point temperature of manganese-zinc ferrite provided by the present invention can quickly respond to customer needs and obtain the target valley point temperature value when the enterprise is in mass production, so as to achieve wide temperature characteristics. Detailed Implementation

[0034] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0035] This embodiment provides a method for regulating the valley point temperature of manganese-zinc ferrite loss, the method comprising the following steps:

[0036] (1) After pressing manganese zinc ferrite powder (including Fe2O3, ZnO and MnO in a mass ratio of (66-70): (5-9): (20-24) and additives in a mass percentage of 2.2%-3.0%) into shape, the pressing pressure is 370-390 MPa, and sintering is carried out under oxygen partial pressures P0, P1 and P2 respectively. The sintering temperature is 1260-1350℃, the holding time is 320-400min, the heating rate is 1.63-5.00℃ / min, and the loss valley temperature T0, T1 and T2 corresponding to the obtained manganese zinc ferrite are measured.

[0037] (2) Calculate the initial compensation coefficient k according to the formula k = (T1 - T2) / (P1 - P2);

[0038] (3) Based on the target valley point temperature T, calculate the sintering oxygen partial pressure P with P = P0 + (T_target – T0) / k. After pressing the manganese-zinc ferrite powder into shape according to the above process, sinter it according to this oxygen partial pressure and measure the actual valley point temperature T_actual of the obtained product.

[0039] (4) Combine the data points (P, T) with (P0, T0), (P1, T1), and (P2, T2) from step (1), fit the linear relationship using the least squares method, and obtain the revised compensation coefficient k'. The formula is as follows, and k' is obtained.

[0040]

[0041] (5) Using the revision factor k', calculate the sintering oxygen partial pressure according to P' = P0 + (T_standard – T0) / k'; press the manganese-zinc ferrite powder into shape according to the above process, and sinter it under the oxygen partial pressure P' to obtain manganese-zinc ferrite with the target loss valley temperature.

[0042] It should be clarified that any use of the process provided in the embodiments of the present invention or any substitution or change of conventional data falls within the protection and disclosure scope of the present invention.

[0043] Example 1

[0044] This embodiment provides a method for regulating the valley point temperature of manganese-zinc ferrite loss, the method comprising the following steps:

[0045] (1) After pressing the manganese zinc ferrite powder (including Fe2O3, ZnO and MnO in a mass ratio of 68.48:6.9:21.75 and silica as an additive with a mass percentage of 2.87%) into shape, the pressing pressure was 380 MPa, and sintering was carried out at oxygen partial pressures P0 3%, P1 2% and P2 4%, respectively. The sintering temperature was 1290℃, the holding time was 370 min, and the heating rate was 4.00 ℃ / min. The loss valley temperatures T0, T1 and T2 of the obtained manganese zinc ferrite were measured to be 78℃, 71℃ and 85℃, respectively.

[0046] (2) Calculate the initial compensation coefficient k=7 according to the formula k = (T1-T2) / (P1-P2);

[0047] (3) Based on the target valley point temperature T_standard 105℃, the sintering oxygen partial pressure P = 6.86% is calculated as P = P0 + (T_standard – T0) / k. After pressing the manganese-zinc ferrite powder into shape according to the above process, sintering is carried out according to this oxygen partial pressure. The actual valley point temperature T_actual = 110℃ of the obtained product is measured.

[0048] (4) Combine the data points (P, T) with (P0, T0), (P1, T1), and (P2, T2) from step (1), fit the linear relationship using the least squares method, and obtain the revised compensation coefficient k'. The formula is as follows, and we get k'=8.09.

[0049]

[0050] (5) Using the revision factor k', the sintering oxygen partial pressure P' = 6.34% is calculated according to P' = P0 + (T_standard – T0) / k'; the manganese-zinc ferrite powder is pressed into shape according to the above process, and sintered at an oxygen partial pressure P' 6.34% to obtain manganese-zinc ferrite with a target loss valley temperature of 105℃.

[0051] Example 2

[0052] This embodiment provides a method for regulating the valley point temperature of manganese-zinc ferrite loss, the method comprising the following steps:

[0053] (1) After pressing the manganese zinc ferrite powder (including Fe2O3, ZnO and MnO in a mass ratio of 66:9:22, and calcium carbonate additive in a mass percentage of 3.0%) into shape, the pressing pressure was 370 MPa, and sintering was carried out at oxygen partial pressures of P0 1.5%, P1 0.5% and P2 2.5%, respectively. The sintering temperature was 1260℃, the holding time was 400 min, and the heating rate was 1.63℃ / min. The loss valley temperatures T0, T1 and T2 of the obtained manganese zinc ferrite were measured to be 84℃, 77℃ and 88℃, respectively.

[0054] (2) Calculate the initial compensation coefficient k=5.5 according to the formula k = (T1-T2) / (P1-P2);

[0055] (3) Based on the target valley point temperature T_standard 95℃, the sintering oxygen partial pressure P = 3.5% is calculated as P = P0 + (T_standard – T0) / k. After pressing the manganese-zinc ferrite powder into shape according to the above process, sintering is carried out according to this oxygen partial pressure. The actual valley point temperature T_actual = 92℃ of the obtained product is measured.

[0056] (4) Combine the data points (P, T) with (P0, T0), (P1, T1), and (P2, T2) from step (1), fit the linear relationship using the least squares method, and obtain the revised compensation coefficient k'. The formula is as follows, and we get k'=4.9.

[0057]

[0058] (5) Using the revision factor k', calculate the sintering oxygen partial pressure according to P' = P0 + (T_standard – T0) / k'; press the manganese-zinc ferrite powder into shape according to the above process, and sinter it at an oxygen partial pressure P' = 3.7% to obtain manganese-zinc ferrite with the target loss valley temperature.

[0059] Example 3

[0060] This embodiment provides a method for regulating the valley point temperature of manganese-zinc ferrite loss, the method comprising the following steps:

[0061] (1) After pressing manganese zinc ferrite powder (including Fe2O3, ZnO and MnO in a mass ratio of 70:5:22.5 and silica as an additive with a mass percentage of 2.5%) into shape, the pressing pressure is 390 MPa, and sintering is carried out at oxygen partial pressures of PO 3.5%, P1 2.5% and P2 4.5%, respectively. The sintering temperature is 1350℃, the holding time is 320 min, and the heating rate is 1.63℃ / min. The loss valley temperatures T0, T1 and T2 of the obtained manganese zinc ferrite are measured to be 90℃, 86℃ and 95℃, respectively.

[0062] (2) Calculate the initial compensation coefficient k=4.5 according to the formula k = (T1-T2) / (P1-P2);

[0063] (3) Based on the target valley point temperature Tstandard = 100℃, the sintering oxygen partial pressure P = 5.7% is calculated using P = P0 + (Tstandard – T0) / k. After pressing the manganese-zinc ferrite powder into shape according to the above process, sintering is carried out according to this oxygen partial pressure. The actual valley point temperature Tactual of the obtained product is measured to be 103℃.

[0064] (4) Combine the data points (P, T) with (P0, T0), (P1, T1), and (P2, T2) from step (1), fit the linear relationship using the least squares method, and obtain the revised compensation coefficient k'. The formula is as follows, and we get k'=5.3.

[0065]

[0066] (5) Using the revision factor k', calculate the sintering oxygen partial pressure according to P' = P0 + (T_standard – T0) / k'; press the manganese-zinc ferrite powder into shape according to the above process, and sinter it at an oxygen partial pressure P' = 5.4 to obtain manganese-zinc ferrite with the target loss valley temperature.

[0067] Performance testing

[0068] The manganese-zinc ferrite with the target loss valley temperature prepared in the example was subjected to loss valley temperature test. The test method was as follows: the sintered magnetic core sample was subjected to wide-temperature loss test using a BH tester, and the actual valley temperature Tactual was calculated. The calculation method was as follows: the loss was calculated using the Steinmetz formula, and the results are shown in Table 1.

[0069]

[0070] As can be seen from Table 1, the three embodiments of the present invention use the same "calculation and compensation" method to determine the basic sintering process. By adjusting the oxygen partial pressure, they can all approach the target valley temperature with a small deviation rate, indicating that this compensation method is accurate and effective.

[0071] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for regulating the valley point temperature of manganese-zinc ferrite loss, characterized in that, The method includes the following steps: (1) After the manganese zinc ferrite powder is pressed into shape, it is sintered under oxygen partial pressures P0, P1 and P2 respectively, and the loss valley temperature T0, T1 and T2 corresponding to the manganese zinc ferrite are measured; wherein, P1 and P2 are symmetrically set on both sides of P0, that is, P0- P1= P2-P0. (2) Calculate the initial compensation coefficient k according to the formula k = (T1 - T2) / (P1 - P2); (3) Based on the target valley point temperature T, calculate the sintering oxygen partial pressure P by P = P0 + (T_target – T0) / k. After pressing the manganese-zinc ferrite powder into shape, sinter it according to this oxygen partial pressure and measure the actual valley point temperature T_actual of the obtained product. (4) Combine the data points (P, T_real) with (P0, T0), (P1, T1), and (P2, T2) from step (1), fit the linear relationship using the least squares method, and obtain the revised compensation coefficient k', with the formula as follows: In the formula, n is the number of data points involved in the fitting, and Pi and Ti are the oxygen partial pressure and measured valley temperature of each data point; (5) Using the revision factor k', the sintering oxygen partial pressure is calculated according to P' = P0 + (T_standard – T0) / k'; after the manganese-zinc ferrite powder is pressed into shape, it is sintered under the oxygen partial pressure P' to obtain manganese-zinc ferrite with the target loss valley temperature.

2. The method according to claim 1, characterized in that, The manganese-zinc ferrite powder includes Fe2O3, ZnO, and MnO; Preferably, the mass ratio of Fe2O3, ZnO and MnO in the manganese-zinc ferrite powder is (66-70):(5-9):(20-24).

3. The method according to claim 1 or 2, characterized in that, The manganese-zinc ferrite powder also includes additives; Preferably, the additive includes silicon dioxide and / or calcium carbonate; Preferably, the mass percentage of additives in the manganese-zinc ferrite powder is 2.2%-3.0%.

4. The method according to any one of claims 1 to 3, characterized in that, The pressure for compression molding is 370-390 MPa.

5. The method according to any one of claims 1 to 4, characterized in that, The sintering temperature is 1260-1350℃.

6. The method according to any one of claims 1 to 5, characterized in that, The holding time for sintering is 320-400 min.

7. The method according to any one of claims 1 to 6, characterized in that, The heating rate for sintering is 1.63 - 5.00 °C / min.

8. The method according to any one of claims 1 to 7, characterized in that, The oxygen partial pressure P0 ranges from 1.5% to 3.5%.

9. The method according to any one of claims 1 to 8, characterized in that, The oxygen partial pressure P1 ranges from 0.5% to 3%.

10. The method according to any one of claims 1 to 9, characterized in that, The oxygen partial pressure P2 is in the range of 2.5%-4.5%.

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