Silicon steel finished product based on porous carbon-based catalyst and preparation method thereof

Abstract

The invention discloses a silicon steel finished product based on a porous carbon-based catalyst and a preparation method thereof.The method comprises the steps that a hydrothermal-inert atmosphere high-temperature calcination method is adopted, and metal and / or N-doped graphene aerogel with the BET specific surface area larger than or equal to 700 m / g and the pore diameter of 2-5 nm is prepared; pre-coating the surfaces of silicon particles with the metal and / or N-doped graphene aerogel through a spray drying method, and forming a porous carbon-based catalyst layer on the surfaces of the silicon particles to obtain coated silicon particles; mixing the coated silicon particles with iron powder to form mixed powder, and adding ethanol, a lanthanum-containing compound and a cerium-containing compound into the mixed powder for ball milling to obtain composite powder; and the composite powder is subjected to spark plasma sintering and post-treatment, and a finished silicon steel product is obtained. The compactness, the magnetic performance and the corrosion resistance of the silicon steel finished product material are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrical steel manufacturing, and particularly relates to a silicon steel finished product based on a porous carbon-based catalyst and a preparation method thereof. BACKGROUND

[0002] The traditional powder metallurgy process of non-oriented silicon steel has significant deficiencies in the control of impurities, inclusions and grain boundary oxides, and generally lacks efficient dynamic regulation mechanisms for powder composition and sintering atmosphere. As a result, the material is insufficiently densified, the grain size is large, and the inclusion content is high, thereby limiting the improvement of magnetic properties, mechanical strength and corrosion resistance. Simple addition of a single rare earth or carbon source cannot achieve in-situ purification and uniform distribution of impurities, and the finished product has high magnetic hysteresis loss, poor stability and consistency, and cannot meet the requirements of new energy equipment manufacturing. SUMMARY

[0003] The present application provides a silicon steel finished product based on a porous carbon-based catalyst and a preparation method thereof, which realizes efficient in-situ purification of impurities and grain refinement in silicon steel, and improves the densification, magnetic properties and corrosion resistance of the silicon steel finished product.

[0004] In one aspect, the present application provides a preparation method of a silicon steel finished product based on a porous carbon-based catalyst, which comprises the following steps: A metal and / or N-doped graphene aerogel with a BET specific surface area of 700 m² / g or more and a pore size of 2-5 nm is prepared by a hydrothermal-inert atmosphere high-temperature calcination method, and the metal includes at least one of iron and chromium; The metal and / or N-doped graphene aerogel is pre-coated on the surface of silicon particles by a spray drying method to form a porous carbon-based catalyst layer on the surface of the silicon particles, thereby obtaining coated silicon particles; the coated silicon particles are mixed with iron powder to form a mixed powder, and ethanol, a lanthanum-containing compound and a cerium-containing compound are added to the mixed powder for ball milling, thereby obtaining a composite powder; The composite powder is subjected to spark plasma sintering and post-processing to obtain a silicon steel finished product.

[0005] Further, the content of impurity elements in the aerogel is 0.01 wt.% or less, the thickness of the catalyst layer is 5-15 nm, and the loading amount is 0.2-1.0 wt.%; and the mass ratio of ethanol, lanthanum element and cerium element is 1:1:3.

[0006] Further, the rotation speed of the atomization disc of the spray drying is 8000 rpm, the atmosphere is argon, and the outlet temperature of the spray drying is equal to the boiling point of the solvent used for the spray drying; The step of adding ethanol, a lanthanum-containing compound and a cerium-containing compound to the mixed powder for ball milling to obtain a composite powder comprises: The mixed powder is added with ethanol, a lanthanum-containing compound and a cerium-containing compound, and the mixed powder, the ethanol, the lanthanum-containing compound and the cerium-containing compound are ball milled at 300-500 rpm for 3-6 hours to obtain the composite powder.

[0007] Further, the composite powder is subjected to spark plasma sintering and post-treatment to obtain the silicon steel product, comprising: The composite powder is pressed into a disc with a diameter of 20 mm by cold isostatic pressing at 200-350 MPa, and the disc is vacuum dried at 120°C for more than or equal to 4 hours; The dried disc is placed in a laser-assisted micro-melting post-treatment device, and a pulsed laser is used to perform rapid surface remelting on the peripheral edge region of the disc to form a shaped disc; The shaped disc is subjected to spark plasma sintering, pickling and annealing to obtain the silicon steel product.

[0008] Further, the shaped disc is subjected to spark plasma sintering, pickling and annealing to obtain the silicon steel product, comprising: A BN protective layer is coated on a sintering mold, the shaped disc is placed in the sintering mold, CO2 / O2 is introduced as a mixed protective gas, the heating rate is set to 75-150°C / min, the temperature is raised to 600°C for 10 min of pre-heat preservation, the temperature is then continuously raised to 1050-1250°C and kept for 20-60 min before cooling to room temperature to obtain a sintered silicon steel disc; The sintered silicon steel disc is pickled with dilute hydrochloric acid for 30 min to remove the surface oxide scale and impurities, and then washed with clean water and dried; The dried sintered silicon steel disc is cold-rolled and annealed to obtain the silicon steel product.

[0009] Further, the dried sintered silicon steel disc is cold-rolled and annealed to obtain the silicon steel product, comprising: The dried sintered silicon steel disc is placed in a cold rolling mill for cold rolling, and is subjected to multi-pass room temperature rolling processing with a total deformation of 60%-80%, gap lubrication cooling is used, the thickness reduction rate of each pass is 10%-20%, and the roller speed is 50-100 m / min to obtain a cold-rolled sheet with Ra≤0.8 μm and grain size of 6-7 μm; The cold-rolled sheet is annealed under argon for 2 h, the heating rate during annealing is 5-15°C / min, and the annealed sheet is slowly cooled to room temperature to obtain the silicon steel product.

[0010] Further, the cold-rolled sheet is annealed under argon for 2 h, with a heating rate of 5-15℃ / min, and then slowly cooled to room temperature to obtain the silicon steel product, including: The cold-rolled sheet is annealed under argon for 1-1.5 h at 750-800℃; The cold-rolled sheet is annealed under argon for 0.5-1 h at 850-900℃; The annealed sheet is slowly cooled to room temperature at a rate of ≤5℃ / min to obtain the silicon steel product.

[0011] Further, the metal and / or N-doped graphene is Fe-N-graphene, the doping ratio of nitrogen in the Fe-N-graphene aerogel is 5-8 at%, the doping ratio of iron is 1.0-2.0 at%, the heating furnace of the hydrothermal-inert atmosphere high-temperature calcination method is controlled at 1000-1120℃, the holding time is 90-100 min, and the air cooling method is used to cool to room temperature.

[0012] Further, after obtaining the coated silicon particles, the method further comprises: The coated silicon particles are cleaned by plasma to increase the surface Zeta potential by ≥10 mV.

[0013] In another aspect, the application provides a silicon steel product based on a porous carbon-based catalyst, which is prepared by the above method, and the composition and weight percentage content of the silicon steel product are: Si: 2.5-4.0 wt.%, La and Ce elements: 0.1-0.2 wt.%, Ti: 0-0.2 wt.%, metal and / or N-doped graphene: 0.2-1.0 wt.%, and the rest is iron and impurities; The grain boundary inclusion of the silicon steel product is <600 ppm, the average grain size is 6-7μm, the coercive force is 850-900 A / m, the loss P15 / 50 is 4.0-5.5 W / kg, and the magnetic induction intensity B50 is 1.6-1.7T.

[0014] The application has the following advantages: The application adopts a hydrothermal-inert atmosphere high-temperature calcination method to prepare metal and / or N-doped graphene aerogel with a BET specific surface area of 700 m2 / g or more and a pore size of 2-5 nm; the metal and / or N-doped graphene aerogel is pre-coated on the surface of silicon particles by a spray drying method to form a porous carbon-based catalyst layer on the surface of the silicon particles, so that the porous carbon catalyst is uniformly dispersed to obtain coated silicon particles; the metal and / or N-doped graphene is sprayed to realize in-situ dynamic purification of oxygen impurities, grain refinement and performance improvement through a high specific surface area porous structure; then the coated silicon particles are mixed with iron powder to form a mixed powder, and ethanol, a lanthanum-containing compound and a cerium-containing compound are added to the mixed powder for ball milling to obtain a composite powder; and a new type of non-oriented silicon steel finished product is obtained through discharge plasma sintering and post-processing of the composite powder. Through the synergistic mode of the porous carbon-based oxygen reduction catalyst and the dynamic atmosphere spark plasma sintering (SPS), efficient in-situ purification and grain refinement of impurities in the silicon steel are realized, and the density, magnetic performance and corrosion resistance of the material are greatly improved, overcoming the defects of the traditional powder metallurgy process, such as difficult purification of impurities, insufficient density and limited performance improvement. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0016] Figure 1 is a flow chart of a preparation method of a silicon steel finished product based on a porous carbon-based catalyst provided by the embodiments of the present application. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0018] Here, it also needs to be explained that, in order to avoid the unnecessary details from obscuring the present application, only the structures and / or processing steps closely related to the scheme of the present application are shown in the drawings, and other details not closely related to the present application are omitted.

[0019] It is also to be noted that the terms "comprising", "comprises" or any other variation thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0020] The embodiment provides a high-efficiency preparation process capable of dynamically purifying, migrating and removing oxygen impurities in a sintering process, effectively refining grains and reducing inclusion and residual oxygen content. Figure 1 As shown in the figure, the embodiment provides a silicon steel finished product preparation method based on a porous carbon-based catalyst, including the following steps: S1, a hydrothermal-inert atmosphere high-temperature calcination method is used to prepare metal and / or N-doped graphene aerogel with a BET specific surface area of greater than or equal to 700 m² / g and a pore size of 2-5 nm; the metal includes at least one of iron and chromium; S2, the metal and / or N-doped graphene aerogel is pre-coated on the surface of silicon particles by a spray drying method to form a porous carbon-based catalyst layer on the surface of the silicon particles, thereby obtaining coated silicon particles; the coated silicon particles are mixed with iron powder to form a mixed powder, and ethanol, a lanthanum-containing compound and a cerium-containing compound are added to the mixed powder for ball milling, thereby obtaining a composite powder; S3, the composite powder is subjected to spark plasma sintering and post-processing to obtain a silicon steel finished product.

[0021] In the embodiment, industrial pure iron, high-purity silicon and other main component raw materials are fully ground, pressed and sintered into a plate material in a ball milling device and a spark plasma sintering furnace, and then subjected to annealing treatment under the protection of an Ar atmosphere after normal temperature pickling, so that low-iron-loss corrosion-resistant non-oriented silicon steel is finally obtained.

[0022] In the raw material weighing process, the weight percentage content is as follows: Si: 2.5-4.0 wt.%, La+Ce: 0.1-0.2 wt.%, Ti: 0-0.2 wt.%, metal and / or N-doped graphene: 0.2-1.0 wt.%, and the rest is iron and unavoidable impurities; wherein the temperature of the hydrothermal-inert atmosphere high-temperature calcination method is 1000-1200°C. The metal and / or N-doped graphene aerogel is a porous carbon-based catalyst, which is pre-coated on the surface of silicon particles by a spray drying method, with a thickness of 5-15 nm, to ensure uniform dispersion and a loading amount of 0.2-1.0 wt.%.

[0023] In this embodiment, the metal and / or N-doped graphene can be metal-doped graphene, N-doped graphene, or metal-N-doped graphene; wherein the metal can be iron, chromium, or a mixture of iron and chromium; wherein Fe-N co-doping provides the best synergistic catalytic activity, and separate N / Fe doping is also possible but with reduced efficiency, and Cr-N can be used instead of Fe-N, and Fe-B is weaker; and the substrate is preferably graphene to optimize the pores and activity, and although graphite and BN can have good performance to some extent, their catalytic stability is poorer than that of graphene.

[0024] For example, the metal and / or N-doped graphene is Fe-N-graphene, the doping ratio of nitrogen in the Fe-N-graphene aerogel is 5-8 at%, and the doping ratio of iron is 1.0-2.0 at%, which meets the dispersibility of the catalyst under a high specific surface area (BET≥700 m² / g) and avoids the increase of inclusions caused by iron agglomeration, thereby realizing dynamic migration of oxygen impurities and grain refinement. The temperature of the heating furnace of the hydrothermal-inert atmosphere high-temperature calcination method is controlled at 1000-1120°C, the holding time is 90-100 min, and the air cooling method is used to cool to room temperature.

[0025] For example, after obtaining the coated silicon particles, the method further comprises: The coated silicon particles are cleaned by plasma to increase the surface Zeta potential by ≥10 mV to enhance the subsequent densification bonding.

[0026] For example, the content of impurity elements in the aerogel is ≤0.01 wt.%, the thickness of the catalyst layer is 5-15 nm, and the loading is 0.2-1.0 wt.%; and the mass ratio of ethanol, lanthanum element, and cerium element is 1:1:3.

[0027] For example, the atomization disc rotation speed of the spray drying is 8000 rpm, the atmosphere is argon, and the outlet temperature of the spray drying is equal to the boiling point of the solvent used for the spray drying; The method of adding ethanol, lanthanum-containing compounds, and cerium-containing compounds to the mixed powder and ball milling to obtain a composite powder comprises: The method of adding ethanol, lanthanum-containing compounds, and cerium-containing compounds to the mixed powder and ball milling to obtain a composite powder comprises:

[0028] In this embodiment, the mixture of rare earths La and Ce and Ti is used to assist in grain boundary strengthening and impurity dispersion. The ball-milled composite powder requires a grain size D50 of less than 8 μm, no obvious agglomeration, no overlapping of Si and Fe single peaks in XRD analysis, and uniform distribution of the catalyst observed by surface scanning electron microscopy.

[0029] For example, the process of obtaining silicon steel products by discharge plasma sintering and post-treatment of the composite powder includes: The composite powder is pressed into discs with a diameter of 20 mm using cold isostatic pressing technology at 200~350 MPa, and the discs are then vacuum dried at 120°C for a drying time of 4 hours or more. After drying, the wafer is placed in a laser-assisted micro-melting post-processing device, and a pulsed laser is used to perform rapid surface remelting on the peripheral edge area of ​​the wafer to form a shaped wafer. The shaped wafers are subjected to spark plasma sintering, pickling, and annealing to obtain the finished silicon steel product.

[0030] For example, the step of subjecting the shaped wafer to spark plasma sintering, pickling, and annealing to obtain the finished silicon steel product includes: A BN protective layer is coated on the sintering mold. The shaped disc is placed in the sintering mold, and CO2 / O2 is introduced as a mixed protective gas. The heating rate is set to 75~150°C / min. The temperature is raised to 600°C and held for 10 min. The temperature is then raised to 1050~1250°C and held for 20~60 min before cooling to room temperature to obtain the sintered silicon steel sheet. The sintered silicon steel sheet was pickled with dilute hydrochloric acid for 30 minutes to remove surface oxide scale and impurities; and after pickling, it was rinsed with clean water and dried. The dried sintered silicon steel discs are cold rolled and annealed to obtain the finished silicon steel product.

[0031] This embodiment employs a two-stage heating method to effectively suppress grain boundary oxidation inclusions and promote the homogenization of orientation texture, thereby improving the magnetic and mechanical properties of non-oriented silicon steel by 10-15%.

[0032] For example, the step of cold rolling and annealing the dried sintered silicon steel wafers to obtain the finished silicon steel product includes: The dried sintered silicon steel discs are placed into a cold rolling mill for cold rolling. The process involves multiple passes of room temperature rolling, with the total deformation controlled at 60% to 80%. Intermittent lubrication and cooling are used, with a thickness reduction rate of 10% to 20% per pass and a roll speed of 50 to 100 m / min, to obtain cold-rolled sheets with Ra ≤ 0.8 μm and grain size of 6 to 7 μm. The cold-rolled sheet was annealed under argon atmosphere for 2 hours, with a heating rate of 5-15℃ / min during annealing. After annealing, it was slowly cooled to room temperature to obtain the finished silicon steel product.

[0033] For example, the cold-rolled sheet is annealed under argon atmosphere for 2 hours, with a heating rate of 5-15°C / min during annealing. After annealing, it is slowly cooled to room temperature to obtain the silicon steel product, comprising: The cold-rolled sheet is subjected to a single annealing treatment under argon atmosphere at a temperature of 750~800℃ for 1~1.5 h. The cold-rolled sheet is subjected to a secondary annealing treatment at a temperature of 850~900℃ for 0.5~1 h. The secondary annealed sheet is slowly cooled to room temperature at a rate of ≤5℃ / min to obtain the finished silicon steel product.

[0034] For example, Fe-N-graphene aerogel with a BET specific surface area ≥700 m² / g and a pore size of 2~5 nm can be prepared by hydrothermal-inert atmosphere high-temperature calcination method, with impurity element content ≤0.01 wt.%. The catalyst is pre-coated onto the surface of silicon particles by spray drying. The slurry containing Fe-N-graphene aerogel is dried using a closed-loop centrifugal spray dryer, and the coating thickness on the surface of silicon particles is controlled to be 5~15 nm. The porous carbon-based catalyst coating layer yields highly stable coated silicon particles. The spray drying is performed under the following conditions: the atomizing disc speed is 8000 rpm, the atmosphere is argon, and the spray drying outlet temperature is equal to the boiling point temperature of the solvent, so that the porous carbon catalyst is uniformly dispersed with a loading of 0.2~1.0 wt.%.

[0035] For example, this embodiment provides a method for preparing silicon steel products based on porous carbon-based catalysts, including: (1) Catalyst preparation and coating: Fe-N-graphene aerogel with a BET specific surface area ≥700 m² / g and a pore size of 2~5 nm was prepared by hydrothermal-inert atmosphere high-temperature calcination method. The impurity element content was ≤0.01 wt.% and the hydrothermal-inert atmosphere high-temperature calcination temperature could be 1000-1200℃. The catalyst was pre-coated onto the surface of silicon particles using a spray drying method. A closed-loop centrifugal spray dryer was used to dry the slurry containing Fe-N-graphene aerogel, controlling the coating thickness to 5-15 nm on the silicon particle surface. This porous carbon-based catalyst coating layer resulted in highly stable coated silicon particles. The spray drying operation conditions were: atomizing disc speed of 8000 rpm, argon atmosphere, and spray dryer outlet temperature equal to the solvent boiling point temperature, ensuring uniform dispersion of the porous carbon catalyst. The porous carbon-based catalyst (Fe-N-graphene aerogel) was pre-coated onto the surface of silicon particles using a spray drying method, controlling the thickness to 5-15 nm, ensuring uniform dispersion and a loading of 0.2-1.0 wt.%. The porous carbon-based oxygen reduction catalyst was Fe-N-graphene aerogel with a BET ≥ 700 m² / g, and was XPS-doped with a nitrogen doping ratio of 5-8 at% and an iron doping ratio of 1.0-2.0 at%. This range satisfies the requirements for a high specific surface area (BET ≥ 700 m² / g). This process achieves optimal dispersion (m² / g) while avoiding iron agglomeration that leads to increased inclusions, thus realizing the goals of dynamic migration of oxygen impurities and grain refinement. The furnace temperature is controlled at 1000-1120℃, with a holding time of 90-100 min, followed by air cooling to room temperature. After ball milling and coating steps, plasma cleaning is used to increase the surface Zeta potential by ≥10 mV to enhance subsequent densification bonding.

[0036] (2) Composite powder mixing: The raw materials are fully mixed according to a certain composition ratio (average particle size is about 9.8~10.0μm), and ethanol, lanthanum and cerium are added on this basis. The mass ratio of rare earth is 1:1:3. The mixture is placed in a ball mill and ball-milled at 300~500 rpm to make the composition of the mixture uniform. In step (1), the composite powder mixing in the subsequent step (2) involves mixing the coated silicon particles with other raw materials (such as industrial pure iron) in a certain proportion, adding ethanol, La and Ce (mass ratio of mixture 1:1:3), and ball-milling at 300~500 rpm for 3~6 hours to achieve composition homogenization. While the ball milling process may cause slight mechanical wear or localized peeling, the coating layer design provides a certain margin and adhesion, and the ball milling conditions are relatively mild (medium to low speed, avoiding high-intensity damage). Therefore, it will not significantly affect the overall thickness or catalytic efficiency. Subsequent XRD and SEM analyses are required to confirm that the catalyst distribution remains uniform and without significant agglomeration, ensuring that even with trace losses, dynamic oxygen impurity purification can be maintained, achieving grain refinement and performance improvement. The mixing of rare earth elements La and Ce with Ti is used to assist in grain boundary strengthening and impurity dispersion. Furthermore, the ball-milled composite powder is required to have a grain size D50 of less than 8 μm, no significant agglomeration, no overlapping Si and Fe peaks in XRD analysis, and uniform catalyst distribution observed by surface scanning electron microscopy.

[0037] (3) Static pressing and drying: The composite powder is pressed into Φ20mm round discs by cold isostatic pressing at 200~350MPa and dried under vacuum at 120°C for no less than 4h.

[0038] (4) Shaping: After drying, the wafer is rapidly remelted around its perimeter using laser-assisted micro-melting post-treatment technology to improve the initial densification and edge bonding strength. In the shaping step, the Φ20mm wafer, after static pressing and drying, is placed in a laser-assisted micro-melting post-treatment device. An Nd:YAG pulsed laser (wavelength 1064 nm, pulse frequency 20-50 Hz, average power 50-100 W) is used to rapidly remelt the perimeter edge area of ​​the wafer. Specifically, the remelting is performed on a region of approximately 1-3 mm bandwidth on the outer perimeter edge of the wafer. The laser beam is uniformly swept at a scanning speed of 10-20 mm / s to achieve local micro-melting without affecting the internal structure. This ensures that the surface of the edge material melts rapidly and resolidifies, thereby improving the initial densification, strengthening the edge bonding strength, and reducing potential micro-crack hazards. This process is carried out under an inert Ar atmosphere and lasts for 30-60 seconds to match the requirements of subsequent sintering processes, avoid grain coarsening or the introduction of oxidation impurities caused by excessive heat input, and ultimately provide a more uniform and stable preform for sintering.

[0039] (5) Sintering: After coating the sintering mold with a BN protective layer, insert the wafers and introduce a CO2 / O2 mixed protective gas. The concentration of the mixed protective gas can be 0.5%-1.5%; the heating rate is 75~150°C / min, preheating at 600°C for 10min, raising to 1050~1250°C, and holding at the lower temperature for 20~60min; the CO2 / O2 concentration (1:1 or 2:1) is dynamically controlled throughout the sintering process, and the wafers are slowly cooled to room temperature after sintering. The purpose of this experiment is to use spark plasma sintering (SPS) technology to perform high-temperature densification treatment on pre-pressed wafers in a mold coated with a BN protective layer. At the same time, by dynamically controlling the concentration of the CO2 / O2 mixed protective gas, the in-situ purification, migration and removal of oxygen impurities can be achieved, thereby effectively refining the grains, reducing the content of inclusions and residual oxygen, improving the density, magnetic properties and mechanical properties of the material, and ultimately meeting the synergistic optimization requirements of high-performance non-oriented silicon steel.

[0040] (6) Pickling and cold rolling: The sintered silicon steel sheet is pickled with dilute hydrochloric acid for 30 min to thoroughly remove the surface oxide scale and impurities. After pickling, it is rinsed with clean water and dried. The dried sintered silicon steel disc (Φ20mm) is placed into a cold rolling mill for multi-pass room temperature rolling. The total deformation is controlled at 60%~80% (the initial thickness is about 2~3mm, and the final sheet size is about 25mm wide, about 80mm long, and 0.3~0.5mm thick). The thickness reduction rate is 10%~20% per pass, the roll speed is 50~100m / min, and the intermittent lubrication and cooling are used to ensure no cracks and a smooth surface (Ra≤0.8μm). At the same time, the grain size is refined to 6~7μm, the orientation texture is homogenized, and the edge bonding strength is improved.

[0041] (7) Annealing treatment: The cold-rolled sheet is finally annealed under Ar atmosphere for 2 hours. The heating rate during annealing is preferably 5-15℃ / min. After annealing, it is slowly cooled to room temperature. After cold rolling, the sheet is directly annealed under Ar atmosphere protection (preferably 850-900℃, heating rate 5-15℃ / min, holding for 2 hours, and slowly cooled to room temperature) to effectively suppress grain boundary oxidation inclusions. The annealing process can adopt a two-stage temperature plateau + slow cooling process (the first stage is set at 750-800℃ for 1-1.5 hours to complete stress release and rare earth / impurity diffusion, the second stage is at 850-900℃ for 0.5-1 hours to optimize recrystallization texture and suppress abnormal grain growth, and then slowly cooled to room temperature at a rate of ≤5℃ / min to ensure that the magnetic and mechanical properties of non-oriented silicon steel are improved by 10-15%), which effectively suppresses grain boundary oxidation inclusions and promotes the homogenization of orientation texture.

[0042] The non-oriented silicon steel product obtained in this embodiment has grain boundary inclusions of <600 ppm, refines the average grain size to the 6-7 μm range, reduces coercivity to 850-900 A / m, significantly lowers loss P15 / 50 to 4.0-5.5 W / kg, and magnetic induction intensity B50 = 1.6-1.7T, resulting in an overall performance improvement of 10-15%. This method can dynamically purify, migrate, and remove oxygen impurities during sintering, effectively refining grains and reducing inclusion and residual oxygen content, thereby significantly improving the density, magnetic properties, and mechanical properties of silicon steel materials, achieving a synergistic breakthrough in multiple performance indicators, and ensuring the industrial feasibility of the process and the consistency of the finished products.

[0043] This embodiment also provides a porous carbon-based catalyst silicon steel product, which is prepared by the above method. The composition and weight percentage content of the silicon steel product are as follows: Si: 2.5~4.0 wt.%, La and Ce: 0.1~0.2 wt.%, Ti: 0~0.2 wt.%, metal and / or N-doped graphene: 0.2~1.0 wt.%; the remainder is iron and impurities. The finished silicon steel product has grain boundary inclusions of <600 ppm, an average grain size of 6~7 μm, a coercivity of 850~900 A / m, a loss P15 / 50 of 4.0~5.5 W / kg, and a magnetic induction intensity B50 of 1.6-1.7T.

[0044] For example, metal and / or N-doped graphene can be Fe-N co-doped graphene.

[0045] The following specific embodiments illustrate the method for preparing silicon steel products based on porous carbon-based catalysts according to the present invention.

[0046] Example 1 (1) Catalyst preparation and coating: 1.0 g of graphene oxide was dispersed in 80 mL of deionized water using a hydrothermal-inert atmosphere high-temperature calcination method. The mixture was ultrasonically treated for 2 h to form a uniform GO colloid. 0.15 g of ferric nitrate nonahydrate and 5 mL of ammonia were added, and the mixture was magnetically stirred for 1 h until completely dissolved. The mixture was transferred to a 100 mL hydrothermal reactor, sealed, and placed in an oven. The temperature was increased to 180 °C at 5 °C / min and maintained for 24 h.

[0047] (2) Inert atmosphere high-temperature calcination step: The precursor was placed in an alumina boat in a tubular high-temperature furnace and heated to 1000 ℃ at 10 ℃ / min under argon protection, and held for 90 min. After calcination, it was slowly cooled to room temperature at 10 ℃ / min to obtain Fe-N-graphene aerogel catalyst. BET test showed a specific surface area of ​​702 m² / g, BJH pore size analysis showed an average pore size of 3.0 nm; XPS analysis showed an N doping ratio of 6.2 at.% and an iron doping ratio of 2 at; the total content of impurity elements (ICP-OES detection) was ≤0.01 wt.%.

[0048] (3) Composite powder mixing: Weigh 86.425 g of industrial pure iron powder (D50=10 μm, purity ≥99.9%), 10.0 g of high-purity silicon-coated powder, and 0.1 g of Ti powder (D50=5 μm, purity ≥99.9%) according to the above component ratio. Add 20 mL of ethanol, lanthanum nitrate hexahydrate, and cerium nitrate hexahydrate, with a La:Ce:total powder mass ratio of 1:1:3. Transfer the mixture to a planetary ball mill (ZrO2 tank, φ10 mm ZrO2 balls), with a ball-to-material ratio of 10:1, a rotation speed of 300 rpm, and ball mill for 2 h (intermittent, stopping for 10 min every 30 min to prevent overheating). After ball milling, vacuum dry (80 ℃, 4 h) to obtain composite powder. XRD analysis showed no overlapping Si / Fe peaks; laser particle size analysis showed D50=6.8 μm, with no agglomeration; SEM surface scanning showed uniform catalyst distribution.

[0049] (4) Static pressing and drying: The composite powder was pressed into Φ20mm discs using cold isostatic pressing at 200MPa and dried under vacuum at 120°C for 4 hours; 0.5 g of the composite powder was placed into a φ20 mm mold and held at 200 MPa for 5 minutes using a cold isostatic press to obtain green discs (approximately 2.5 mm thick). The discs were placed in a vacuum drying oven (120 ℃, vacuum degree -0.1 MPa) and dried for 4 hours, with a moisture content ≤0.1 wt.%.

[0050] (5) Laser-assisted micro-melting and shaping: The dried disc is fixed on the laser micro-melting equipment platform. The laser power is 20 W and the scanning speed is 500 mm / s. A single-track circular scan is performed along the perimeter of the disc (1 mm wide) and the disc is remelted once. After the treatment, the edge densification is improved by 15% and the bonding strength is increased by 20%.

[0051] (6) Spark Plasma Sintering: The inner wall of the sintering mold (φ20 mm graphite mold) is coated with a BN protective layer (thickness 0.2 mm), a disc is inserted, and placed in an SPS furnace. A CO2 / O2 mixed protective gas is introduced (CO2 volume ratio 1.0%, O2 0.5%, total flow rate 200 mL / min, dynamically controlled throughout: CO2 / O2 = 1:1 before 600 ℃, then adjusted to 2:1). The program controls the temperature to rise from room temperature (75 ℃ / min) to 600 ℃, pre-hold for 10 min; continue to rise to 1150 ℃, hold for 30 min (pressure 50 MPa, pulse voltage 3 kV, duty cycle 50%); after sintering, cool slowly to room temperature at 20 ℃ / min. A sintered disc (thickness 1.8 mm, diameter 20 mm, initial density 95%) is obtained. (7) Pickling and cold rolling: The sintered sheet was immersed in dilute hydrochloric acid (5 vol.% HCl, room temperature) for 30 min (magnetically stirred at 200 rpm), and gently shaken once every 10 min. It was rinsed 5 times with deionized water (ultrasonicated for 5 min each time) and dried with nitrogen. The surface oxide scale and impurities were completely removed, and the mass loss was ≤0.5 wt.%. The pickled sheet was rolled on a four-roll cold rolling mill with a total deformation of 50% (10% deformation per pass, 5 passes, intermittent annealing to avoid cracking) to obtain a sheet with a thickness of 0.35 mm (size 25 mm × 80 mm). (8) Annealing: During the annealing process, the sheet was placed in a tube furnace and heated to the annealing temperature of 880 ℃ at a rate of 5 ℃ / min under the protection of argon (purity ≥99.999%, flow rate 150 mL / min) (two-stage plateau: 800 ℃ for 30 min + 880 ℃ for 2 h), and then slowly cooled to room temperature at a rate of 3 ℃ / min. The final properties were measured with an average grain size of 6.5 μm (EBSD); density of 99.6% (Archimedes method); and iron loss P. 15 / 50 =4.5 W / kg (single-piece iron loss meter, f=50 Hz, B=1.5 T); bending strength 365 MPa (three-point bending method); surface corrosion resistant area 68% (SEM area statistics after 96 h of salt spray test).

[0052] Example 2 (1) Catalyst preparation and coating: 1.5 g of graphene oxide was dispersed in 100 mL of deionized water using a hydrothermal-inert atmosphere high-temperature calcination method. The mixture was ultrasonically treated for 2 h to form a uniform GO colloid. 0.15 g of ferric nitrate nonahydrate and 5 mL of ammonia were added, and the mixture was magnetically stirred for 1 h until completely dissolved. The mixture was transferred to a 100 mL hydrothermal reactor, sealed, and placed in an oven. The temperature was increased to 180 °C at 5 °C / min and maintained for 24 h.

[0053] (2) Inert atmosphere high-temperature calcination step: The precursor was placed in an alumina boat in a tubular high-temperature furnace and heated to 1000 ℃ at 10 ℃ / min under argon protection, and held for 90 min. After calcination, it was slowly cooled to room temperature at 10 ℃ / min to obtain Fe-N-graphene aerogel catalyst. BET test showed a specific surface area of ​​805 m² / g, BJH pore size analysis showed an average pore size of 5.0 nm; XPS analysis showed an N doping ratio of 6.8 at.% and an iron doping ratio of 2 at; the total content of impurity elements (ICP-OES detection) was ≤0.01 wt.%.

[0054] (3) Composite powder mixing: Weigh 86.425 g of industrial pure iron powder (D50=10 μm, purity ≥99.9%), 10.0 g of high-purity silicon-coated powder, and 0.1 g of Ti powder (D50=5 μm, purity ≥99.9%) according to the above component ratio. Add 20 mL of ethanol, lanthanum nitrate hexahydrate, and cerium nitrate hexahydrate, with a La:Ce:total powder mass ratio of 1:2:3. Transfer the mixture to a planetary ball mill (ZrO2 tank, φ10 mm ZrO2 balls), with a ball-to-material ratio of 10:1, a rotation speed of 300 rpm, and ball milling for 5 h. After ball milling, vacuum dry (80℃, 4 h) to obtain composite powder. XRD analysis showed no overlapping Si / Fe peaks; laser particle size analysis showed D50=6.8 μm, with no agglomeration; SEM surface scanning showed uniform catalyst distribution.

[0055] (4) Static pressing and drying: The composite powder was pressed into Φ20mm discs using cold isostatic pressing at 250MPa and dried under vacuum at 120°C for 5h; 0.5 g of the composite powder was placed into a φ20 mm mold and held at 200 MPa for 5 min using a cold isostatic press to obtain green discs (approximately 2.5 mm thick). The discs were placed in a vacuum drying oven (120 ℃, vacuum degree -0.1 MPa) and dried for 4 h, with a moisture content ≤0.1 wt.%.

[0056] (5) Laser-assisted micro-melting and shaping: The dried disc is fixed on the laser micro-melting equipment platform. The laser power is 20 W and the scanning speed is 500 mm / s. A single-track circular scan is performed along the perimeter of the disc (width 1 mm) and the disc is remelted once.

[0057] (6) Spark Plasma Sintering: The inner wall of the sintering mold (φ20 mm graphite mold) is coated with a BN protective layer (thickness 0.2 mm), a disc is inserted, and placed in an SPS furnace. A CO2 / O2 mixed protective gas is introduced (CO2 volume ratio 1.0%, O2 0.5%, total flow rate 200 mL / min, dynamically controlled throughout: CO2 / O2 = 1:1 before 600 ℃, then adjusted to 2:1). The program controls the temperature increase from room temperature (75 ℃ / min) to 600 ℃, preheating for 10 min; then continues to increase to 1200 ℃, and lowering for 30 min. After sintering, the temperature is slowly cooled to room temperature at 20 ℃ / min. A sintered disc (thickness 1.8 mm, diameter 20 mm, initial density 95%) is obtained. (7) Pickling and cold rolling: The sintered sheet was immersed in dilute hydrochloric acid (5 vol.% HCl, room temperature) for 30 min (magnetically stirred at 200 rpm), and gently shaken once every 10 min. It was rinsed 5 times with deionized water (ultrasonicated for 5 min each time) and dried with nitrogen. The surface oxide scale and impurities were completely removed, and the mass loss was ≤0.5 wt.%. The pickled sheet was rolled on a four-roll cold rolling mill with a total deformation of 50% (10% deformation per pass, 5 passes, intermittent annealing to avoid cracking) to obtain a sheet with a thickness of 0.35 mm (size 25 mm × 80 mm). (8) Annealing: During the annealing process, the sheet was placed in a tube furnace and heated to the annealing temperature of 880 ℃ at a rate of 8+ ℃ / min under argon protection (two-stage plateau: 800 ℃ for 30 min + 880 ℃ for 2 h), and then slowly cooled to room temperature at a rate of 3 ℃ / min. The final properties were: average grain size 6.82 μm; density 98.8% (Archimedes method); iron loss P 15 / 50 =5.16 W / kg; flexural strength 359 MPa (three-point bending method); surface corrosion resistant area 61% (SEM area statistics after 96 h of salt spray test).

[0058] Comparative Example 1 (1) Catalyst preparation and coating: Fe-N-graphene aerogel was prepared by hydrothermal-inert atmosphere high-temperature calcination at 1000℃, with impurity element content ≤0.01 wt.%; the catalyst was pre-coated onto the surface of silicon particles by spray drying, with the coating thickness controlled at 10 nm, so that the porous carbon catalyst was uniformly dispersed and the loading was 0.3 wt.%. (2) High-temperature calcination and composite powder mixing: The precursor was placed in an alumina boat in a tubular high-temperature furnace and heated to 1000 ℃ at 10 ℃ / min under argon protection, and held for 90 min. After calcination, it was slowly cooled to room temperature at 10 ℃ / min to obtain Fe-N-graphene aerogel catalyst. According to BET test, the specific surface area was 810 m² / g, and the average pore size was 6.0 nm according to BJH pore size analysis; XPS analysis showed that the N doping ratio was 6.2 at.%, the iron doping ratio was 5 at%, and the total content of impurity elements (ICP-OES detection) was ≤0.01 wt.%. The raw materials were fully mixed according to a certain composition ratio, and ethanol, lanthanum and cerium were added on this basis. The mass ratio of rare earth elements to the mixture was 1:1:3. The mixture was placed in a ball mill and ball-milled at 300 rpm for 2 h to make the composition of the mixture uniform. (3) Static pressing and drying: The composite powder was pressed into Φ20mm discs by cold isostatic pressing at 200MPa and dried under vacuum at 120°C for 4h; (4) Shaping: After drying, the disc is rapidly remelted around the periphery of the disc using laser-assisted micro-melting post-processing technology to improve the initial densification degree and edge bonding strength; (5) Sintering: After coating the sintering mold with a BN protective layer, insert the disc and introduce a CO2 / O2 mixed protective gas. The heating rate is 75°C / min, preheat at 600°C for 10min, then raise to 1150°C and hold for 30min. The CO2 / O2 concentration is dynamically controlled throughout the sintering process. After sintering, the temperature is slowly cooled to room temperature. (6) Pickling and cold rolling: The sintered silicon steel sheet was pickled with dilute hydrochloric acid for 30 minutes to thoroughly remove the surface oxide scale and impurities. After pickling, it was rinsed with clean water and dried. The pickled sheet was rolled on a four-roll cold rolling mill with a total deformation of 50% (10% deformation per pass, 5 passes, intermittent annealing to avoid cracking) to obtain a sheet with a thickness of 0.35 mm (size 25 mm × 80 mm). (7) Annealing treatment: The cold-rolled sheet was finally annealed under argon atmosphere for 2 h, with a heating rate of 5 °C / min during annealing. After annealing, it was slowly cooled to room temperature. A new type of non-oriented high-silicon steel with an average grain size of 8.2 μm, a density of 87.2%, an iron loss of 7.1 W / kg, a bending strength of 284 MPa, and a surface corrosion-resistant area of ​​49% was obtained.

[0059] Comparative Example 2 (1) Catalyst preparation and coating: Fe-N-graphene aerogel was prepared by hydrothermal-inert atmosphere high-temperature calcination at 1000℃, with impurity element content ≤0.01 wt.%; the catalyst was pre-coated onto the surface of silicon particles by spray drying, with the coating thickness controlled at 10 nm, so that the porous carbon catalyst was uniformly dispersed and the loading was 0.3 wt.%. (2) High-temperature calcination and composite powder mixing: The precursor was placed in an alumina boat in a tubular high-temperature furnace and heated to 1000 ℃ at 10 ℃ / min under argon protection, and held for 90 min. After calcination, it was slowly cooled to room temperature at 10 ℃ / min to obtain Fe-N-graphene aerogel catalyst. According to BET test, the specific surface area was 550 m² / g, and the average pore size was 1.5 nm according to BJH pore size analysis; XPS analysis showed that the N doping ratio was 6.2 at.%, the iron doping ratio was 0.5 at%, and the total content of impurity elements (ICP-OES detection) was ≤0.01 wt.%. The raw materials were fully mixed according to a certain composition ratio, and ethanol, lanthanum and cerium were added on this basis. The mass ratio of rare earth elements to the mixture was 1:1:3. The mixture was placed in a ball mill and ball-milled at 300 rpm for 2 h to make the composition of the mixture uniform. (3) Static pressing and drying: The composite powder was pressed into Φ20mm discs by cold isostatic pressing at 200MPa and dried under vacuum at 120°C for 4h; (4) Shaping: After drying, the disc is rapidly remelted around the periphery of the disc using laser-assisted micro-melting post-processing technology to improve the initial densification degree and edge bonding strength; (5) Sintering: After coating the sintering mold with a BN protective layer, insert the disc and introduce a CO2 / O2 mixed protective gas. The heating rate is 75°C / min, preheat at 600°C for 10min, then raise to 1150°C and hold for 30min. The CO2 / O2 concentration is dynamically controlled throughout the sintering process. After sintering, the temperature is slowly cooled to room temperature. (6) Pickling and cold rolling: The sintered silicon steel sheet was pickled with dilute hydrochloric acid for 30 minutes to thoroughly remove the surface oxide scale and impurities. After pickling, it was rinsed with clean water and dried. The pickled sheet was rolled on a four-roll cold rolling mill with a total deformation of 50% (10% deformation per pass, 5 passes, intermittent annealing to avoid cracking) to obtain a sheet with a thickness of 0.35 mm (size 25 mm × 80 mm). (7) Annealing treatment: The cold-rolled sheet was finally annealed under argon atmosphere for 2 h, with a heating rate of 5 °C / min during annealing. After annealing, it was slowly cooled to room temperature. A new type of non-oriented high-silicon steel with an average grain size of 5.4 μm, a density of 88.2%, an iron loss of 6.8 W / kg, a bending strength of 304 MPa, and a surface corrosion-resistant area of ​​51% was obtained.

[0060] Comparative Example 3 (1) Catalyst preparation and coating: Fe-N-graphene aerogel was prepared by hydrothermal-inert atmosphere high-temperature calcination at 1000℃, with impurity element content ≤0.01 wt.%; the catalyst was pre-coated onto the surface of silicon particles by spray drying, with the coating thickness controlled at 10 nm, so that the porous carbon catalyst was uniformly dispersed and the loading was 0.3 wt.%. (2) High-temperature calcination and composite powder mixing: The precursor was placed in an alumina boat in a tubular high-temperature furnace and heated to 1000 ℃ at 10 ℃ / min under argon protection, and held for 90 min. After calcination, it was slowly cooled to room temperature at 10 ℃ / min to obtain Fe-N-graphene aerogel catalyst. According to BET test, the specific surface area was 880 m² / g, and the average pore size was 10.0 nm according to BJH pore size analysis; XPS analysis showed that the N doping ratio was 9.5 at.%, the iron doping ratio was 2 at%, and the total content of impurity elements (ICP-OES detection) was ≤0.01 wt.%. The raw materials were fully mixed according to a certain composition ratio, and ethanol, lanthanum and cerium were added on this basis. The mass ratio of rare earth elements to the mixture was 1:1:3. The mixture was placed in a ball mill and ball-milled at 300 rpm for 2 h to make the composition of the mixture uniform. (3) Static pressing and drying: The composite powder was pressed into Φ20mm discs by cold isostatic pressing at 200MPa and dried under vacuum at 120°C for 4h; (4) Shaping: After drying, the disc is rapidly remelted around the periphery of the disc using laser-assisted micro-melting post-processing technology to improve the initial densification degree and edge bonding strength; (5) Sintering: After coating the sintering mold with a BN protective layer, insert the disc and introduce a CO2 / O2 mixed protective gas. The heating rate is 75°C / min, preheat at 600°C for 10min, then raise to 1150°C and hold for 30min. The CO2 / O2 concentration is dynamically controlled throughout the sintering process. After sintering, the temperature is slowly cooled to room temperature. (6) Pickling and cold rolling: The sintered silicon steel sheet was pickled with dilute hydrochloric acid for 30 minutes to thoroughly remove the surface oxide scale and impurities. After pickling, it was rinsed with clean water and dried. The pickled sheet was rolled on a four-roll cold rolling mill with a total deformation of 50% (10% deformation per pass, 5 passes, intermittent annealing to avoid cracking) to obtain a sheet with a thickness of 0.35 mm (size 25 mm × 80 mm). (7) Annealing treatment: The cold-rolled sheet was finally annealed under argon atmosphere for 2 h, with a heating rate of 5 °C / min during annealing. After annealing, it was slowly cooled to room temperature. A new type of non-oriented high-silicon steel with an average grain size of 10.2 μm, a density of 81.3%, an iron loss of 7.36 W / kg, a bending strength of 275 MPa, and a surface corrosion-resistant area of ​​50% was obtained.

[0061] Comparative Example 4 (1) Catalyst preparation and coating: Fe-N-graphene aerogel was prepared by hydrothermal-inert atmosphere high-temperature calcination at 1000℃, with impurity element content ≤0.01 wt.%; the catalyst was pre-coated onto the surface of silicon particles by spray drying, with the coating thickness controlled at 10 nm, so that the porous carbon catalyst was uniformly dispersed and the loading was 0.3 wt.%. (2) High-temperature calcination and composite powder mixing: The precursor was placed in an alumina boat in a tubular high-temperature furnace and heated to 1000 ℃ at 10 ℃ / min under argon protection, and held for 90 min. After calcination, it was slowly cooled to room temperature at 10 ℃ / min to obtain Fe-N-graphene aerogel catalyst. According to BET test, the specific surface area was 480 m² / g, and the average pore size was 8 nm according to BJH pore size analysis; XPS analysis showed that the N doping ratio was 3.2 at.%, the iron doping ratio was 2 at%, and the total content of impurity elements (ICP-OES detection) was ≤0.01wt.%. The raw materials were fully mixed according to a certain composition ratio, and ethanol, lanthanum and cerium were added on this basis. The mass ratio of rare earth elements to the mixture was 1:1:3. The mixture was placed in a ball mill and ball-milled at 300 rpm for 2 h to make the composition of the mixture uniform. (3) Static pressing and drying: The composite powder was pressed into Φ20mm discs by cold isostatic pressing at 200MPa and dried under vacuum at 120°C for 4h; (4) Shaping: After drying, the disc is rapidly remelted around the periphery of the disc using laser-assisted micro-melting post-processing technology to improve the initial densification degree and edge bonding strength; (5) Sintering: After coating the sintering mold with a BN protective layer, insert the disc and introduce a CO2 / O2 mixed protective gas. The heating rate is 75°C / min, preheat at 600°C for 10min, then raise to 1150°C and hold for 30min. The CO2 / O2 concentration is dynamically controlled throughout the sintering process. After sintering, the temperature is slowly cooled to room temperature. (6) Pickling and cold rolling: The sintered silicon steel sheet was pickled with dilute hydrochloric acid for 30 minutes to thoroughly remove the surface oxide scale and impurities. After pickling, it was rinsed with clean water and dried. The pickled sheet was rolled on a four-roll cold rolling mill with a total deformation of 50% (10% deformation per pass, 5 passes, intermittent annealing to avoid cracking) to obtain a sheet with a thickness of 0.35 mm (size 25 mm × 80 mm). (7) Annealing treatment: The cold-rolled sheet was finally annealed under argon atmosphere for 2 hours. The heating rate during annealing was 5℃ / min. After annealing, it was slowly cooled to room temperature. A new type of non-oriented high-silicon steel with an average grain size of 9.6 μm, a density of 84.2%, an iron loss of 7.05 W / kg, a bending strength of 292 MPa, and a surface corrosion-resistant area of ​​52% was obtained.

[0062] Comparative Example 5 (1) Catalyst preparation and coating: A hydrothermal-inert atmosphere high-temperature calcination method was used. 5.0 g of graphene oxide was dispersed in 20 mL of deionized water and ultrasonically treated for 2 h to form a uniform GO colloid. 0.15 g of ferric nitrate nonahydrate and 5 mL of ammonia were added, and the mixture was magnetically stirred for 1 h until completely dissolved. The mixture was transferred to a 100 mL hydrothermal reactor, sealed, and placed in an oven. The temperature was increased to 180 °C at 5 °C / min and held for 24 h. The catalyst was pre-coated onto the surface of silicon particles by spray drying, with a coating thickness controlled at 100 nm to ensure uniform dispersion of the porous carbon catalyst. The loading was 2.3 wt.%. (2) High-temperature calcination and composite powder mixing: The precursor was placed in an alumina boat in a tubular high-temperature furnace and heated to 1000 ℃ at 10 ℃ / min under argon protection, and held for 90 min. After calcination, it was slowly cooled to room temperature at 10 ℃ / min to obtain Fe-N-graphene aerogel catalyst. According to BET test, the specific surface area was 813 m² / g, and the average pore size was 6.0 nm according to BJH pore size analysis; XPS analysis showed that the N doping ratio was 6.2 at.% and the iron doping ratio was 2 at.%; the total content of impurity elements (ICP-OES detection) was ≤0.01 wt.%. The raw materials were fully mixed according to a certain composition ratio, and ethanol, lanthanum and cerium were added on this basis. The mass ratio of rare earth elements to the mixture was 1:1:3. The mixture was placed in a ball mill and ball-milled at 300 rpm for 2 h to make the composition of the mixture uniform. (3) Static pressing and drying: The composite powder was pressed into Φ20mm discs by cold isostatic pressing at 200MPa and dried under vacuum at 120°C for 4h; (4) Shaping: After drying, the disc is rapidly remelted around the periphery of the disc using laser-assisted micro-melting post-processing technology to improve the initial densification degree and edge bonding strength; (5) Sintering: After coating the sintering mold with a BN protective layer, insert the disc and introduce a CO2 / O2 mixed protective gas. The heating rate is 75°C / min, preheat at 600°C for 10min, then raise to 1150°C and hold for 30min. The CO2 / O2 concentration is dynamically controlled throughout the sintering process. After sintering, the temperature is slowly cooled to room temperature. (6) Pickling and cold rolling: The sintered silicon steel sheet was pickled with dilute hydrochloric acid for 30 minutes to thoroughly remove the surface oxide scale and impurities. After pickling, it was rinsed with clean water and dried. The pickled sheet was rolled on a four-roll cold rolling mill with a total deformation of 50% (10% deformation per pass, 5 passes, intermittent annealing to avoid cracking) to obtain a sheet with a thickness of 0.35 mm (size 25 mm × 80 mm). (7) Annealing treatment: The cold-rolled sheet was finally annealed under argon atmosphere for 2 h, with a heating rate of 5 °C / min during annealing. After annealing, it was slowly cooled to room temperature. A new type of non-oriented high-silicon steel with an average grain size of 5.1 μm, a density of 90.5%, an iron loss of 6.8 W / kg, a bending strength of 287 MPa, and a surface corrosion-resistant area of ​​46% was obtained.

[0063] Comparative Example 6 (1) Catalyst preparation and coating: A hydrothermal-inert atmosphere high-temperature calcination method was used. 0.5 g of graphene oxide was dispersed in 200 mL of deionized water and ultrasonically treated for 2 h to form a uniform GO colloid. 0.15 g of ferric nitrate nonahydrate and 5 mL of ammonia were added, and the mixture was magnetically stirred for 1 h until completely dissolved. The mixture was transferred to a 100 mL hydrothermal reactor, sealed, and placed in an oven. The temperature was increased to 180 °C at 5 °C / min and maintained for 24 h. The catalyst was pre-coated onto the surface of silicon particles using a spray drying method, with a coating thickness controlled at 2 nm to ensure uniform dispersion of the porous carbon catalyst. The loading was 0.05 wt.%. (2) High-temperature calcination and composite powder mixing: The precursor was placed in an alumina boat in a tubular high-temperature furnace and heated to 1000 ℃ at 10 ℃ / min under argon protection, and held for 90 min. After calcination, it was slowly cooled to room temperature at 10 ℃ / min to obtain Fe-N-graphene aerogel catalyst. According to BET test, the specific surface area was 402 m² / g, and the average pore size was 1.0 nm according to BJH pore size analysis; XPS analysis showed that the N doping ratio was 6.2 at.% and the iron doping ratio was 2 at.%; the total content of impurity elements (ICP-OES detection) was ≤0.01 wt.%. The raw materials were fully mixed according to a certain composition ratio, and ethanol, lanthanum and cerium were added on this basis. The mass ratio of rare earth elements to the mixture was 1:1:3. The mixture was placed in a ball mill and ball-milled at 300 rpm for 2 h to make the composition of the mixture uniform. (3) Static pressing and drying: The composite powder was pressed into Φ20mm discs by cold isostatic pressing at 200MPa and dried under vacuum at 120°C for 4h; (4) Shaping: After drying, the disc is rapidly remelted around the periphery of the disc using laser-assisted micro-melting post-processing technology to improve the initial densification degree and edge bonding strength; (5) Sintering: After coating the sintering mold with a BN protective layer, insert the disc and introduce a CO2 / O2 mixed protective gas. The heating rate is 75°C / min, preheat at 600°C for 10min, then raise to 1150°C and hold for 30min. The CO2 / O2 concentration is dynamically controlled throughout the sintering process. After sintering, the temperature is slowly cooled to room temperature. (6) Pickling and cold rolling: The sintered silicon steel sheet was pickled with dilute hydrochloric acid for 30 minutes to thoroughly remove the surface oxide scale and impurities. After pickling, it was rinsed with clean water and dried. The pickled sheet was rolled on a four-roll cold rolling mill with a total deformation of 50% (10% deformation per pass, 5 passes, intermittent annealing to avoid cracking) to obtain a sheet with a thickness of 0.35 mm (size 25 mm × 80 mm). (7) Annealing treatment: The cold-rolled sheet was finally annealed under argon atmosphere for 2 hours. The heating rate during annealing was 5℃ / min. After annealing, it was slowly cooled to room temperature. A new type of non-oriented high-silicon steel with an average grain size of 2.7μm, a density of 95.6%, an iron loss of 6.3W / kg, a bending strength of 307 MPa, and a surface corrosion-resistant area of ​​53% was obtained.

[0064] Comparative Example 7 (1) Catalyst preparation and coating: Fe-N-graphene aerogel with a BET specific surface area ≥700 m² / g and a pore size of 3 nm was prepared by hydrothermal-inert atmosphere high-temperature calcination at 1000℃, with impurity element content ≤0.01 wt.%; the catalyst was pre-coated onto the surface of silicon particles by spray drying, with the coating thickness controlled at 10 nm, so that the porous carbon catalyst was uniformly dispersed and the loading was 0.3 wt.%. (2) High-temperature calcination and composite powder mixing: The precursor was placed in an alumina boat in a tubular high-temperature furnace and heated to 1000 ℃ at 10 ℃ / min under argon protection, and held for 90 min. After calcination, it was slowly cooled to room temperature at 10 ℃ / min to obtain Fe-N-graphene aerogel catalyst. According to BET test, the specific surface area was 702 m² / g, and the average pore size was 3.0 nm according to BJH pore size analysis; XPS analysis showed that the N doping ratio was 6.2 at.% and the iron doping ratio was 2 at.%; the total content of impurity elements (ICP-OES detection) was ≤0.01 wt.%. 86.425 g of industrial pure iron powder (D50=10 μm, purity ≥99.9%), 10.0 g of high-purity silicon coated powder, and 0.1 g of Ti powder (D50=5 μm, purity ≥99.9%) were weighed according to the above composition ratio. 20 mL of ethanol, lanthanum nitrate hexahydrate, and cerium nitrate hexahydrate were added, with a La:Ce:total powder mass ratio of 1:1:3. The mixture was transferred to a planetary ball mill (ZrO2 jar, φ10 mm ZrO2 balls) at a ball-to-powder ratio of 10:1, at a speed of 1000 rpm, and milled for 2 h. After milling, the mixture was vacuum dried (80 ℃, 4 h) to obtain the composite powder.

[0065] (3) Static pressing and drying: The composite powder was pressed into Φ20mm discs by cold isostatic pressing at 200MPa and dried under vacuum at 120°C for 4h; (4) Shaping: After drying, the disc is rapidly remelted around the periphery of the disc using laser-assisted micro-melting post-processing technology to improve the initial densification degree and edge bonding strength; (5) Sintering: After coating the sintering mold with a BN protective layer, insert the disc and introduce a CO2 / O2 mixed protective gas. The heating rate is 75°C / min, preheat at 600°C for 10min, then raise to 1150°C and hold for 30min. The CO2 / O2 concentration is dynamically controlled throughout the sintering process. After sintering, the temperature is slowly cooled to room temperature. (6) Pickling and cold rolling: The sintered silicon steel sheet was pickled with dilute hydrochloric acid for 30 minutes to thoroughly remove the surface oxide scale and impurities. After pickling, it was rinsed with clean water and dried. The pickled sheet was rolled on a four-roll cold rolling mill with a total deformation of 50% (10% deformation per pass, 5 passes, intermittent annealing to avoid cracking) to obtain a sheet with a thickness of 0.35 mm (size 25 mm × 80 mm). (7) Annealing treatment: The cold-rolled sheet was finally annealed under argon atmosphere for 2 hours. The heating rate during annealing was 5℃ / min. After annealing, it was slowly cooled to room temperature. A new type of non-oriented high-silicon steel with an average grain size of 3μm, a density of 91.5%, an iron loss of 6.6W / kg, a bending strength of 310 MPa, and a surface corrosion-resistant area of ​​52% was obtained.

[0066] Comparative Example 8 (1) Catalyst preparation and coating: Fe-N-graphene aerogel with a BET specific surface area ≥700 m² / g and a pore size of 3 nm was prepared by hydrothermal-inert atmosphere high-temperature calcination at 1000℃, with impurity element content ≤0.01 wt.%; the catalyst was pre-coated onto the surface of silicon particles by spray drying, with the coating thickness controlled at 10 nm, so that the porous carbon catalyst was uniformly dispersed and the loading was 0.3 wt.%. (2) High-temperature calcination and composite powder mixing: The precursor was placed in an alumina boat in a tubular high-temperature furnace and heated to 1000 ℃ at 10 ℃ / min under argon protection, and held for 90 min. After calcination, it was slowly cooled to room temperature at 10 ℃ / min to obtain Fe-N-graphene aerogel catalyst. According to BET test, the specific surface area was 702 m² / g, and the average pore size was 3.0 nm according to BJH pore size analysis; XPS analysis showed that the N doping ratio was 6.2 at.% and the iron doping ratio was 2 at.%; the total content of impurity elements (ICP-OES detection) was ≤0.01 wt.%. 86.425 g of industrial pure iron powder (D50=10 μm, purity ≥99.9%), 10.0 g of high-purity silicon coated powder, and 0.1 g of Ti powder (D50=5 μm, purity ≥99.9%) were weighed according to the above composition ratio. 20 mL of ethanol, lanthanum nitrate hexahydrate, and cerium nitrate hexahydrate were added, with a La:Ce:total powder mass ratio of 1:1:3. The mixture was transferred to a planetary ball mill (ZrO2 jar, φ10 mm ZrO2 balls) at a ball-to-powder ratio of 10:1, at a speed of 50 rpm, and milled for 2 h. After milling, the mixture was vacuum dried (80 ℃, 4 h) to obtain the composite powder.

[0067] (3) Static pressing and drying: The composite powder was pressed into Φ20mm discs by cold isostatic pressing at 200MPa and dried under vacuum at 120°C for 4h; (4) Shaping: After drying, the disc is rapidly remelted around the periphery of the disc using laser-assisted micro-melting post-processing technology to improve the initial densification degree and edge bonding strength; (5) Sintering: After coating the sintering mold with a BN protective layer, insert the disc and introduce a CO2 / O2 mixed protective gas. The heating rate is 75°C / min, preheat at 600°C for 10min, then raise to 1150°C and hold for 30min. The CO2 / O2 concentration is dynamically controlled throughout the sintering process. After sintering, the temperature is slowly cooled to room temperature. (6) Pickling and cold rolling: The sintered silicon steel sheet was pickled with dilute hydrochloric acid for 30 minutes to thoroughly remove the surface oxide scale and impurities. After pickling, it was rinsed with clean water and dried. The pickled sheet was rolled on a four-roll cold rolling mill with a total deformation of 50% (10% deformation per pass, 5 passes, intermittent annealing to avoid cracking) to obtain a sheet with a thickness of 0.35 mm (size 25 mm × 80 mm). (7) Annealing treatment: The cold-rolled sheet was finally annealed under argon atmosphere for 2 hours. The heating rate during annealing was 5℃ / min. After annealing, it was slowly cooled to room temperature. A new type of non-oriented high-silicon steel with an average grain size of 10.2μm, a density of 81.7%, an iron loss of 10.5W / kg, a bending strength of 274 MPa, and a surface corrosion-resistant area of ​​45% was obtained.

[0068] As can be seen, the silicon steel products obtained in the comparative examples, including those with excessive or insufficient Fe doping, excessive or insufficient N doping, excessive catalyst addition, excessively thick coating, excessively thin catalyst coating, excessively high ball milling speed, and excessively low ball milling speed, have higher density, lower iron loss, higher bending strength, and higher surface corrosion-resistant area compared to the comparative examples.

[0069] This invention employs a hydrothermal-inert atmosphere high-temperature calcination method to prepare metal and / or N-doped graphene aerogels with a BET specific surface area ≥700 m² / g and a pore size of 2~5 nm. The metal and / or N-doped graphene aerogels are pre-coated onto the surface of silicon particles using a spray drying method, forming a porous carbon-based catalyst layer on the silicon particle surface. This ensures uniform dispersion of the porous carbon catalyst, resulting in coated silicon particles. The spraying of metal and / or N-doped graphene aims to achieve in-situ dynamic purification of oxygen impurities, grain refinement, and performance improvement through the high specific surface area porous structure. The coated silicon particles are then mixed with iron powder to form a mixed powder. Ethanol, a lanthanum-containing compound, and a cerium-containing compound are added to the mixed powder, followed by ball milling to obtain a composite powder. The composite powder is then subjected to spark plasma sintering and post-treatment to obtain a novel non-oriented silicon steel product. By employing a synergistic approach of porous carbon-based oxygen reduction catalyst and dynamic atmosphere discharge plasma sintering (SPS), efficient in-situ purification of impurities and grain refinement in silicon steel were achieved, significantly improving the material's density, magnetic properties, and corrosion resistance. This overcomes the shortcomings of traditional powder metallurgy processes, such as difficulty in impurity purification, insufficient density, and limited performance improvement.

[0070] The above-disclosed embodiments are merely a few preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing silicon steel based on a porous carbon-based catalyst, characterized in that, The method includes: A metal and / or N-doped graphene aerogel with a BET specific surface area ≥700 m² / g and a pore size of 2~5 nm was prepared by a hydrothermal-inert atmosphere high-temperature calcination method; the metal includes at least one of iron and chromium. The metal and / or N-doped graphene aerogel is pre-coated onto the surface of silicon particles by spray drying, forming a porous carbon-based catalyst layer on the surface of the silicon particles, resulting in coated silicon particles; the coated silicon particles are mixed with iron powder to form a mixed powder, and ethanol, a lanthanum-containing compound, and a cerium-containing compound are added to the mixed powder and ball-milled to obtain a composite powder; The composite powder is subjected to spark plasma sintering and post-treatment to obtain silicon steel finished product.

2. The method according to claim 1, characterized in that, The aerogel contains ≤0.01 wt.% impurity elements, the catalyst layer has a thickness of 5~15 nm and a loading of 0.2~1.0 wt.%, and the mass ratio of ethanol, lanthanum, and cerium is 1:1:

3.

3. The method according to claim 1, characterized in that, The atomizing disc of the spray dryer rotates at 8000 rpm, the atmosphere is argon, and the outlet temperature of the spray dryer is equal to the boiling point of the solvent used in the spray dryer. The process involves adding ethanol, a lanthanum-containing compound, and a cerium-containing compound to the mixed powder and then ball milling it to obtain a composite powder, comprising: Ethanol, a lanthanum-containing compound, and a cerium-containing compound are added to the mixed powder, and the mixed powder, the ethanol, the lanthanum-containing compound, and the cerium-containing compound are ball-milled at 300-500 rpm for 3-6 hours to obtain the composite powder.

4. The method according to claim 1, characterized in that, The process of obtaining silicon steel products by discharge plasma sintering and post-treatment of the composite powder includes: The composite powder is pressed into discs with a diameter of 20 mm using cold isostatic pressing technology at 200~350 MPa, and the discs are then vacuum dried at 120°C for a drying time of 4 hours or more. After drying, the wafer is placed in a laser-assisted micro-melting post-processing device, and a pulsed laser is used to perform rapid surface remelting on the peripheral edge area of ​​the wafer to form a shaped wafer. The shaped wafers are subjected to spark plasma sintering, pickling, and annealing to obtain the finished silicon steel product.

5. The method according to claim 4, characterized in that, The process of subjecting the shaped wafers to spark plasma sintering, pickling, and annealing to obtain the finished silicon steel product includes: A BN protective layer is coated on the sintering mold. The shaped disc is placed in the sintering mold, and CO2 / O2 is introduced as a mixed protective gas. The heating rate is set to 75~150°C / min. The temperature is raised to 600°C and held for 10 min. The temperature is then raised to 1050~1250°C and held for 20~60 min before cooling to room temperature to obtain the sintered silicon steel sheet. The sintered silicon steel sheet was pickled with dilute hydrochloric acid for 30 minutes to remove surface oxide scale and impurities; and after pickling, it was rinsed with clean water and dried. The dried sintered silicon steel discs are cold rolled and annealed to obtain the finished silicon steel product.

6. The method according to claim 5, characterized in that, The process of cold rolling and annealing the dried sintered silicon steel discs to obtain the finished silicon steel product includes: The dried sintered silicon steel discs are placed into a cold rolling mill for cold rolling. The process involves multiple passes of room temperature rolling, with the total deformation controlled at 60% to 80%. Intermittent lubrication and cooling are used, with a thickness reduction rate of 10% to 20% per pass and a roll speed of 50 to 100 m / min, to obtain cold-rolled sheets with Ra ≤ 0.8 μm and grain size of 6 to 7 μm. The cold-rolled sheet was annealed under argon atmosphere for 2 hours, with a heating rate of 5-15℃ / min during annealing. After annealing, it was slowly cooled to room temperature to obtain the finished silicon steel product.

7. The method according to claim 6, characterized in that, The cold-rolled sheet was annealed under argon atmosphere for 2 hours, with a heating rate of 5-15°C / min. After annealing, it was slowly cooled to room temperature to obtain the finished silicon steel product, comprising: The cold-rolled sheet is subjected to a single annealing treatment under argon atmosphere at a temperature of 750~800℃ for 1~1.5 h. The cold-rolled sheet is subjected to a secondary annealing treatment at a temperature of 850~900℃ for 0.5~1 h. The secondary annealed sheet is slowly cooled to room temperature at a rate of ≤5℃ / min to obtain the finished silicon steel product.

8. The method according to claim 1, characterized in that, The metal and / or N-doped graphene is Fe-N-graphene, and the nitrogen doping ratio in the Fe-N-graphene aerogel is 5~8 at%, and the iron doping ratio is 1.0~2.0 at%. The temperature of the heating furnace in the hydrothermal-inert atmosphere high-temperature calcination method is controlled at 1000-1120℃, the holding time is 90-100 min, and the temperature is cooled to room temperature by air cooling.

9. The method according to claim 1, characterized in that, After obtaining the coated silicon particles, the method further includes: The coated silicon particles were cleaned using plasma to increase the surface zeta potential by ≥10 mV.

10. A finished silicon steel product based on a porous carbon-based catalyst, characterized in that, The silicon steel product is prepared by the method according to any one of claims 1-9, and the composition and weight percentage content of the silicon steel product are as follows: Si: 2.5~4.0 wt.%, La and Ce: 0.1~0.2 wt.%, Ti: 0~0.2 wt.%, metal and / or N-doped graphene: 0.2~1.0 wt.%; the remainder is iron and impurities. The finished silicon steel product has grain boundary inclusions of <600 ppm, an average grain size of 6~7 μm, a coercivity of 850~900 A / m, a loss P15 / 50 of 4.0~5.5 W / kg, and a magnetic induction intensity B50 of 1.6-1.7T.

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