Flux motor stator based on soft magnetic composite material warm-pressing molding and manufacturing method thereof

Abstract

The invention discloses a magnetic flux motor stator based on soft magnetic composite material warm-pressing molding and a manufacturing method thereof, and relates to the technical field of motor stators. The preparation method comprises the following steps: mixing iron-based powder with chromic acid, phosphoric acid, water and composite wax according to different proportions, and carrying out insulation coating treatment; carrying out preheating treatment on the coated powder in a mold cavity which is heated to 80 DEG C; the preheated iron-based powder is pressurized through operation of a pressing machine and a mold frame; after pressure maintaining, the press demolds the formed pressed blank; the formed pressed blank is transferred into a steam treatment furnace for gradient sintering, synthetic wax in the product is removed, and gaps are formed in the product; introducing water vapor and nitrogen to generate a compact oxidation film on the surface of the product; and cooling to room temperature along with the furnace, and taking out under nitrogen sweeping. According to the method, a warm-pressing forming method is adopted, the magnetic induction intensity of the stator can reach the maximum value at the mold temperature of 80 DEG C, the magnetic core loss reaches the minimum value, higher density is achieved, and the magnetic conductivity is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of motor stator technology, and in particular relates to a flux motor stator based on warm pressing of soft magnetic composite material and its manufacturing method. Background Technology

[0002] Traditional silicon steel axial flux motors suffer from high eddy current losses at high frequencies, reaching up to 286 W / kg (1T / 1kHz), low axial space utilization, and difficult machining of complex structures. Soft magnetic composite materials, on the other hand, can be integrally molded using traditional powder metallurgy methods, reducing the machining difficulty of axial flux motors. Furthermore, soft magnetic composite materials exhibit lower eddy current losses at high frequencies, at 127 W / kg (1T / 1kHz), which can improve the motor's output capacity.

[0003] Traditional soft magnetic composite materials suffer from low mechanical strength. For example, SMC stators formed by cold pressing have a mechanical strength of only 20-50 MPa, which cannot meet the strength requirements of axial flux motors under high-speed rotation, making them prone to cracking. Furthermore, the manufacturing process of SMC stators formed by cold pressing also has defects. Poor pressure uniformity during cold pressing leads to uneven product density, with lower density at the center and higher density at the edges, resulting in a density deviation of ±0.2 g / cm³. 3 Furthermore, temperature deviations during sintering can lead to over- or under-sintering of the product, and incomplete decomposition of the lubricant can create micropores on the product surface, increasing porosity by approximately 3% and consequently increasing eddy current losses by 20-30%. Internal stress control issues can result in elastic after-effect stress release during pressing and demolding, and uneven sintering cooling rates generating thermal stress, which in turn affects the stator's flatness (>0.1 mm / m) and leads to insufficient air gap. Introducing warm pressing can improve strength, with the density of the pressed product exceeding 7.5 g / cm³. 3 At the same time, under high density, the permeability of SMC stator can be significantly improved, reaching 850. Based on this, this scheme proposes a method for preparing SMC stator by warm pressing, which can not only improve the strength of stator, but also optimize the magnetic properties of stator, including high permeability and low loss. Summary of the Invention

[0004] This invention provides a flux motor stator based on warm pressing of soft magnetic composite material and its manufacturing method, which solves the above problems.

[0005] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0006] The flux motor stator of the present invention, based on the warm pressing molding of soft magnetic composite material, uses the following weight percentages of 0.3-0.6wt% chromic acid, 0.6-1.2wt% phosphoric acid, 3-6wt% water, 0.1-0.6wt% silicone resin, and 0.2-0.6wt% composite wax to perform an insulating coating treatment on iron-based powder, and then molds the iron-based powder after insulating coating.

[0007] Furthermore, the particle size of the iron-based powder is <150μm.

[0008] A method for manufacturing a flux motor stator based on warm pressing of soft magnetic composite materials, used for manufacturing the aforementioned flux motor stator based on warm pressing of soft magnetic composite materials, includes the following steps:

[0009] S1. The iron-based powder is coated with chromic acid, phosphoric acid, water, silicone resin and composite wax according to the corresponding weight percentages.

[0010] S2. Heat the mold to 80℃, where the mold is heated by evenly distributed heating rods, and the temperature difference between each heating rod is controlled within ±2.5℃; then fill the mold cavity with the coated iron-based powder for preheating treatment.

[0011] S3. Pressurize the loosely packed iron-based powder filling the mold with a press, increase the pressure to 800MPa at a rate of 66MPa / s, and hold the pressure for 1s.

[0012] S4. After holding the pressure, the press releases the pressure and performs the demolding action of the formed blank, so that the formed blank is removed from the mold cavity. The temperature of the pressed blank after demolding is 85℃.

[0013] S5. The resulting compact is transferred to a steam treatment furnace for gradient sintering as follows:

[0014] ① Raise the room temperature to 320℃ and keep it warm for 2 hours to remove the synthetic wax in the product and create gaps in the product;

[0015] ② Introduce water vapor and nitrogen in a 1:1 volume ratio. The water vapor is introduced after being vaporized from liquid water.

[0016] The water vapor flow rate is 12-14 m³ / h 3 / h, nitrogen flow rate is 10-12m 3 / h, the temperature of the compact is raised from 320℃ to 520℃ and held for 20min, so that a dense oxide film is formed on the surface of the product;

[0017] ③ Increase nitrogen flow rate to 20m 3 / h, enabling the product to be rapidly cooled with the furnace at a cooling rate greater than 15℃ / min.

[0018] The present invention has the following advantages over the prior art:

[0019] (1) This scheme adopts the warm pressing molding method, which allows the magnetic flux density of the stator to reach the maximum value and the core loss to reach the minimum value at a mold temperature of 80℃.

[0020] (2) Iron-based powder with a particle size of less than 150 μm, treated with insulating coating by different proportions of chromic acid, phosphoric acid, water and composite wax, is filled into the mold cavity at 80°C and pressurized to 800 MPa at a rate of 66 MPa / s to achieve a density of at least 7.5 g / cm³. 3 It has higher density and significantly improved magnetic permeability;

[0021] (3) After the prepared compact is demolded, it is gradient sintered, heated from room temperature to 320°C and held for 2 hours. This can remove the synthetic wax in the product and create gaps in the product. In the subsequent steam treatment, the steam can completely enter the interior of the product to form a dense oxide film. The temperature is then raised from 320°C to 520°C and held for 20 minutes. Nitrogen and water vapor are introduced. Heat treatment at this temperature can effectively release the internal stress of the product, improve the resistivity of the product, and ensure that the water vapor can oxidize at this temperature.

[0022] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a graph showing the changes in magnetic induction intensity detected at mold temperatures of 90°C, 80°C, and 70°C in an embodiment of the present invention.

[0025] Figure 2 This is a graph showing the change in core loss detected at mold temperatures of 80°C and 70°C in an embodiment of the present invention.

[0026] Figure 3 This is a diagram showing the state of the press before it is pressed, in an embodiment of the present invention, during the powder loading process.

[0027] Figure 4 This is a state diagram of the press during pressing in an embodiment of the present invention;

[0028] Figure 5 This is a state diagram during demolding in an embodiment of the present invention;

[0029] Figure 6 This is a distribution diagram of the heating rods and thermocouples in the female mold in an embodiment of the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] This invention relates to a flux motor stator based on warm pressing of soft magnetic composite materials. The iron-based powder is insulated by coating it with the following weight percentages: 0.3-0.6 wt% chromic acid, 0.6-1.2 wt% phosphoric acid, 3-6 wt% water, 0.1-0.6 wt% silicone resin, and 0.2-0.6 wt% composite wax. The insulated iron-based powder is then molded. The particle size of the iron-based powder is <150 μm.

[0032] A method for manufacturing a flux motor stator based on warm pressing of soft magnetic composite materials, used for manufacturing the aforementioned flux motor stator based on warm pressing of soft magnetic composite materials, includes the following steps:

[0033] S1. The iron-based powder is coated with chromic acid, phosphoric acid, water, silicone resin and composite wax according to the corresponding weight percentages.

[0034] S2. Heat the mold to 80℃, where the mold is heated by heating rods, with 8 heating rods evenly distributed in the mold (e.g., Figure 6 As shown), the temperature difference is controlled within ±2.5℃; then the coated iron-based powder is filled into the mold cavity;

[0035] S3. Pressurize the loosely packed iron-based powder filling the mold with a press, increase the pressure to 800MPa at a rate of 66MPa / s, and hold the pressure for 1s.

[0036] S4. After holding the pressure, the press releases the pressure and performs the demolding action of the formed blank, so that the formed blank is removed from the mold cavity. The temperature of the pressed blank after demolding is 85℃.

[0037] S5. The resulting compact is transferred to a steam treatment furnace for gradient sintering as follows:

[0038] ① Raise the room temperature to 320℃ and keep it at that temperature for 2 hours to remove the synthetic wax from the product, causing interstitial cells to form in the product.

[0039] The gap allows steam to fully penetrate the product during subsequent steam treatment, forming a dense oxide film.

[0040] ② Introduce water vapor and nitrogen in a 1:1 volume ratio. The water vapor is introduced after being vaporized from liquid water.

[0041] The water vapor flow rate is 12-14 m³ / h 3 / h, nitrogen flow rate is 10-12m 3 The compact is heated from 320℃ to 520℃ per hour and held at this temperature for 20 minutes. Heat treatment at this temperature effectively releases internal stress, increases resistivity, and ensures proper oxidation by water vapor. The 20-minute holding time ensures complete oxidation by water vapor, maintaining high resistivity. Too short a time results in incomplete oxidation, while too long a time deepens the oxide layer, affecting the product's resistivity.

[0042] ③ Increase nitrogen flow rate to 20m 3 / h, allowing the product to be cooled at a rate >15℃ / min under nitrogen saturation.

[0043] The furnace is rapidly cooled to room temperature, and the finished flux motor stator is obtained upon removal.

[0044] The SMC type stator was prepared using the above-described process.

[0045] Using warm pressing molding, at a mold temperature of 70-90℃, the magnetic induction intensity of the product is tested at different temperatures using a BH testing and analysis instrument. Figure 1 The magnetic flux density shown reaches its maximum value of 1.61 T at 80℃; as Figure 2 As shown, the core loss is lowest at 80℃, at 132 W / kg. Furthermore, as the temperature increases, the magnetic induction intensity decreases while the core loss increases. This is because excessively high temperatures damage the insulating layer on the surface of the magnetic powder core, increasing the loss.

[0046] like Figure 3-5 As shown, taking the existing TKN-F750×300 molding press as an example, the SMC type stator is prepared using the above-mentioned technical solution formula; the molding press includes an upper die punch plate 1, an upper die punch cover 2, an upper die punch 3, a mandrel 4, a female die 5, a first lower die punch 6, a first punch cover 7, a first punch pad 8, a second lower die punch 9, a second punch cover 10, a second punch pad 11, a mandrel connecting rod 12, a mandrel pressure cover 13, a mandrel pressure pad 14, a thermocouple 16 set on the female die 5, and heating rods 15 arranged around it;

[0047] Temperature is detected using thermocouples. In high-temperature environments (typically 300-500°C), water vapor (H2O) reacts with iron (Fe) to form iron(III) oxide (Fe3O4), with the reaction formula: 3Fe + 4H2O → Fe3O4 + 4H2↑. Fe3O4 (magnetite) is a dense and stable oxide layer that effectively isolates oxygen and moisture, preventing further corrosion of the metal.

[0048] The change in resistivity is due to a change in composition; pure iron with low resistivity is transformed into magnetite with high resistivity. Steam treatment creates a dense magnetite film on the product surface, transforming pure iron into ferrite. Increasing the nitrogen flow rate from 12m³ / h... 3 / h upgraded to 20nm 3 / h.

[0049] The suppression action is as follows:

[0050] Powder filling status:

[0051] The first lower die punch 6 and the second lower die punch 9 rise to the preset height. Their final rising position determines the height of the mold cavity sidewall. The top of the mandrel 4 is precisely adjusted to be flush with the upper surface of the middle die. The female die 5 remains in the powder loading position (usually also the highest position); the upper die punch 3 is raised and moved away from the upper surface of the middle die, leaving space for powder loading, and the powder corresponding to the formula of this solution is loaded;

[0052] Molding state:

[0053] The upper die punch 3 descends into the female die 5, applying the main pressing force. Under the pressure (overcoming the force of the support cylinder or spring), the female die 5 floats downwards by approximately 10-20mm. This is typically a controlled, relatively slow movement. The mandrel 4 floats downwards along with the middle die (usually synchronized with the middle die or controlled by an independent force system). In the later stages of pressing, its tip precisely enters the guide hole or clearance hole corresponding to the bottom of the upper punch. The mandrel 4 and the second lower die punch 9 actively descend a preset distance during the pressing process (usually in the middle to later stages). This distance is typically less than the floating amount of the middle die. The first die cover 7 and the second stamping cover 10 remain fixed, serving as bottom support and forming reference.

[0054] Demolding state

[0055] The upper die punch 3 returns and rises, completely exiting the female die 5; the female die 5 continues to descend (or is pushed downwards by the ejector cylinder) until its upper end face is flush with the top of the fixed lower inner punch; the mandrel 4 descends synchronously (usually in conjunction with the female die 5), and eventually its top end is also flush with the top of the fixed lower inner punch; the first lower die punch 6 and the second lower die punch 9 descend until their upper end faces are flush with the upper end face of the female die 5. At this point, the entire outer contour and center hole of the blank are completely exposed on the same plane formed by the top surfaces of the first lower die punch 6, the second lower die punch 9, and the female die 5. The blank loses all constraints and is "lifted out" of the mold cavity.

[0056] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A flux motor stator based on warm-press molding of soft magnetic composite material, characterized in that, The iron-based powder is coated with 0.3-0.6 wt% chromic acid, 0.6-1.2 wt% phosphoric acid, 3-6 wt% water, 0.1-0.6 wt% silicone resin, and 0.2-0.6 wt% composite wax in the following weight percentages, and then the coated iron-based powder is molded.

2. The flux motor stator based on warm pressing of soft magnetic composite material according to claim 1, characterized in that, The particle size of the iron-based powder is <150μm.

3. A method for manufacturing a flux motor stator based on warm pressing of soft magnetic composite material, used to manufacture the flux motor stator based on warm pressing of soft magnetic composite material as described in any one of claims 1-2, characterized in that, Includes the following steps: S1. The iron-based powder is coated with chromic acid, phosphoric acid, water, silicone resin and composite wax according to the corresponding weight percentages. S2. Heat the mold to 80℃, where the mold is heated by evenly distributed heating rods, and the temperature difference between each heating rod is controlled within ±2.5℃; then fill the mold cavity with the coated iron-based powder for preheating treatment. S3. Pressurize the loosely packed iron-based powder filling the mold through a press and mold frame, increase the pressure to 800MPa at a rate of 66MPa / s, and hold the pressure for 1s. S4. After holding the pressure, the press releases the pressure and performs the demolding action of the formed blank, so that the formed blank is removed from the mold cavity. The temperature of the pressed blank after demolding is 85℃. S5. The resulting compact is transferred to a steam treatment furnace for gradient sintering as follows: ① Raise the room temperature to 320℃ and keep it at that temperature for 2 hours to remove the synthetic wax from the product, causing the product to produce gap; ② Introduce water vapor and nitrogen in a volume ratio of 1:

1. The water vapor is vaporized after passing through liquid water. The steam flow rate is 12-14 m³ / h. 3 / h, nitrogen flow rate is 10-12m 3 / h, the temperature of the compact is raised from 320℃ to 520℃ and held for 20min, so that a dense oxide film is formed on the surface of the product; ③ Increase nitrogen flow rate to 20m 3 / h, enabling the product to be rapidly cooled with the furnace at a cooling rate greater than 15℃ / min.

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