A rare earth treated non-oriented silicon steel and a method for manufacturing the same

Abstract

The present application relates to the technical field of metallurgy, in particular to a rare earth treated non-oriented silicon steel and a preparation method thereof. The non-oriented silicon steel comprises the following components and contents: 3.0-3.5% of Si, 0.8-1.5% of Al, 0.3-0.7% of Mn, C≤0.0025%, S≤0.0025%, Ti≤0.0025%, N≤0.0025%, P≤0.015%, 0.0001-0.006% of segregation elements, and the balance of Fe and impurities; the segregation elements are at least one of La, Ce and Y. The preparation process comprises RH refining, continuous casting and hot rolling. The slag thickness and temperature are controlled in the RH refining, electromagnetic stirring is used in the continuous casting, and the reduction rate is controlled by three-stage heating in the hot rolling. The present application realizes the purification of molten steel, modification of inclusions and solid solution segregation by means of rare earth, refines the solidification structure by combining with process optimization, improves the proportion of equiaxed crystals of the casting blank, reduces the surface density of inclusions and optimizes the morphology, and improves the uniformity of the silicon steel structure and the magnetism.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, specifically to a rare earth-treated non-oriented silicon steel and its preparation method. Background Technology

[0002] Non-oriented silicon steel is a core soft magnetic material for motor and transformer cores. Its magnetic properties, such as iron loss and magnetic induction, directly determine energy conversion efficiency. The quality of these magnetic properties is mainly affected by factors such as grain size, texture type, and the content and distribution of inclusions. An ideal microstructure should have a uniform grain structure, a strengthened {100} facet texture (easy to magnetize), and a weakened {111} facet texture (difficult to magnetize). At the same time, fine, dispersed inclusions smaller than 1 μm should be kept to a minimum to reduce the pinning effect on magnetic domain movement.

[0003] The coarse columnar or equiaxed crystals in the solidification structure of non-oriented silicon steel are difficult to homogenize completely during subsequent hot rolling. This is one of the root causes of the resulting layered structure in the thickness direction of the finished plate, i.e., the surface layer consists of recrystallized equiaxed crystals, while the core consists of elongated deformed fibrous structures. This layered structure persists after annealing, affecting the uniformity of magnetic properties.

[0004] To address the aforementioned issues, patent CN114807512A discloses a method for refining the grain structure of silicon steel through an LF refining process. This method involves adding nano-yttrium oxide crystals to increase the nucleation rate and refine the solidification structure, ultimately resulting in silicon steel with a grain size exceeding 151 μm. Patents CN115233082A, CN107245647A, and CN107164690A disclose a method for preparing non-oriented silicon steel strips with a well-developed magnetically advantageous texture using continuous casting. This method enhances the inheritance of the {100} texture by adding low-melting-point elements or by locally rolling the cast strip, but it cannot be achieved in conventional thick slab processes. Patent CN119753485A discloses a method for controlling the solidification structure of high-grade non-oriented silicon steel based on pulsed current control. This method controls the solidification structure by intelligently adjusting the current and layered heating of the slab during continuous casting, but the patent does not mention its effects, only its role in homogenizing the structure, and it cannot effectively refine the solidification structure.

[0005] The solidification microstructure of non-oriented electrical steel is the starting point for its entire subsequent processing flow, and its morphological characteristics have a profound impact on subsequent processing through the "microstructure inheritance" effect. Based on traditional slab continuous casting of non-oriented silicon steel, the inherent coarse columnar crystals and central equiaxed crystal structure of the slab are difficult to completely eliminate in subsequent hot rolling, leading to significant microstructure delamination and texture gradient differences in the hot-rolled plate. This inhomogeneity is inherited by the finished product, impairing the uniformity of the microstructure. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a rare-earth-treated non-oriented silicon steel and its preparation method. This invention adds rare-earth elements to non-oriented silicon steel to purify the molten steel, remove impurities and solid solution segregation, refine equiaxed grains, and improve the uniformity of the finished sheet's microstructure through genetic processes. This solves the problem of coarse solidification microstructure in non-oriented electrical steel leading to stratification during hot rolling and resulting in uneven finished products.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: On one hand, this invention provides a rare-earth-treated non-oriented silicon steel, which is prepared with the following chemical composition by mass percentage: Si: 3.0%~3.5%, Al: 0.8%~1.5%, Mn: 0.3%~0.7%, C≤0.0025%, S≤0.0025%, Ti≤0.0025%, N≤0.0025%, P≤0.015%, segregating element: 0.0001%~0.006%, with the balance being Fe and unavoidable impurities, totaling 100%; wherein the segregating element is at least one of La, Ce, and Y.

[0008] In the rare earth-treated non-oriented silicon steel, the main alloying elements are Si, Al, and Mn, and the harmful elements are C, S, Ti, N, and P.

[0009] In a preferred embodiment of the present invention, the content of the segregating element satisfies the following condition: When the segregating element is a single element: La≤0.004%, Ce≤0.004% or Y≤0.003%.

[0010] When the segregating elements are any two elements: (La+Ce)≤0.006%, (La+Y)≤0.004% and Y≤0.002%, or (Ce+Y)≤0.004% and Y≤0.002%.

[0011] When the segregating elements are three elements: (La+Ce+Y)≤0.003% and Y≤0.001%.

[0012] It should be noted that the present invention, by adding trace amounts of single or composite rare earth elements such as lanthanum (La), cerium (Ce), and yttrium (Y) to non-oriented silicon steel, can improve the microstructure uniformity of non-oriented silicon steel from multiple dimensions. Specifically, this can be divided into the following three aspects:

[0013] Firstly, it purifies molten steel: Rare earth elements (RE, namely La, Ce, and Y) have an extremely strong affinity for oxygen and sulfur, far exceeding that of common elements such as aluminum and manganese. Before the molten steel solidifies, they preferentially combine with dissolved [O] and [S] to form high-melting-point rare earth oxides RE2O3, sulfur oxides RE2O2S, or sulfides RE2S3. These compounds typically have a lower density than molten steel, thus allowing them to float into the slag and be removed.

[0014] Second, altered inclusions: rare earth atoms diffuse to the surface of inclusions such as Al2O3 and MnS and react with them, gradually transforming them into spherical or ellipsoidal composite inclusions containing rare earth elements; spherical inclusions have less stress concentration when subjected to force, and their resistance to the movement of magnetic domain walls is much less than that of irregular inclusions.

[0015] Thirdly, there is solid solution segregation: rare earth atoms dissolve in the ferrite matrix. Because their atomic radii are much larger than those of iron atoms, they tend to diffuse and accumulate at crystal defects such as grain boundaries and phase boundaries. By hindering grain boundary migration and solute dragging effects, they directly affect the nucleation sites and grain growth rate during recrystallization. By refining the solidification structure, more nucleation sites are provided for recrystallization.

[0016] Therefore, when rare earth elements are added to molten steel, they precipitate high-melting-point compounds before solidification, forming fine particles distributed throughout the molten steel. These particles act as heterogeneous nucleation centers, increasing the nucleation rate and reducing the supercooling during crystallization, thus refining the solidification structure. The roles of rare earth elements La, Ce, and Y differ slightly, and their synergistic effect when added in combination can achieve better results. All rare earth elements have functions such as impurity removal and microstructure refinement, but their effects vary depending on their content. Different rare earth elements can form different inclusions, and the difficulty and impact of removing these inclusions also differ. Excessive content of the same rare earth element can have adverse effects; therefore, it is necessary to combine multiple rare earth elements to further improve efficiency.

[0017] On the other hand, the present invention provides a method for preparing the above-mentioned rare earth-treated non-oriented silicon steel, comprising the following steps: S1. Smelt steel according to the set composition, and then perform RH refining on the molten steel. During the refining process, a polymerizing element is added to obtain RH-refined molten steel. The composition and mass percentage content of the molten steel are as follows: Si: 2.8%~3.4%, Al: 0.6%~1.4%, Mn: 0.2%~0.5%, C≤0.05%, S≤0.012%, Ti≤0.003%, N≤0.004%, P≤0.015%, with the balance being Fe and unavoidable impurities, totaling 100%.

[0018] In a preferred embodiment of the present invention, during the RH refining process, the average thickness of the original slag layer when the ladle enters the station is ≥80mm and the temperature is 1560℃~1590℃.

[0019] In a preferred embodiment of the present invention, the specific process of RH refining includes the following steps: decarburizing and deoxidizing the molten steel; the oxygen content after decarburization is ≤260ppm. Subsequently, a desulfurizing agent is added to the molten steel and stirred, followed by the addition of rare earth elements, with a stirring time of 6 to 8 minutes. After RH refining, the molten steel is calmed to obtain RH-refined molten steel, with a calming time of 15 to 16 minutes.

[0020] The specific parameters for RH refining are: average refining slag thickness ≥ 80mm when the ladle enters the station, and RH inlet temperature 1560℃~1590℃; then the following steps are performed to process the molten steel: (1) Decarbonization and deoxygenation, with the oxygen content at the end of decarbonization being ≤260ppm.

[0021] (2) Add desulfurizing agent and pure rare earth material. After adding the desulfurizing agent, the circulation stirring time is 6 min to 8 min.

[0022] (3) After RH vacuum refining is completed, the molten steel is required to be cooled for 15 min to 16 min.

[0023] (4) Molten steel RH leaves the station.

[0024] The average thickness of the refining slag entering the ladle is ≥80mm. This is because a slag layer of ≥80mm reduces radiative and convective heat loss from the molten steel, preventing a rapid drop in temperature after entering the station and thus preventing a decrease in degassing efficiency due to excessively low temperature. The slag layer can completely cover the surface of the molten steel, isolating it from air contact and reducing the introduction of secondary oxidation products. At the same time, it adsorbs deoxidation products generated in the molten steel, ensuring the purity of the molten steel.

[0025] The low oxygen level after RH decarburization prevents the reaction of [O] in the molten steel with alloying elements such as Al, Si, and Mn, reducing the formation of inclusions such as Al2O3, SiO2, and MnO. Low oxygen also increases the equilibrium constant of the desulfurization reaction (CaO) + [S] = (CaS) + [O], achieving ultra-low desulfurization. Simultaneously, it avoids oxidation loss caused by the addition of rare earth materials, improving rare earth recovery. In a preferred embodiment of the invention, the inclusion types in the RH-exit molten steel are mainly RE1O3, RE2O2S, and RE... x S y Among them, RE x S y This refers to RE2S3 and RES, as well as rare earth sulfides that may form with more atoms. In this invention, it specifically refers to La2S3, Ce2S3, Y2S3, LaS, CeS, or YS.

[0026] The desulfurizing agent is a CaO-CaF2 series high-efficiency desulfurizing agent, preferably CaO-CaF2-MgO-Al2O3.

[0027] S2. The RH-refined material is continuously cast to obtain a billet.

[0028] In a preferred embodiment of the present invention, during continuous casting, the billet casting speed is 1.0 m / min to 1.1 m / min, electromagnetic stirring is used during solidification, and the billet thickness is 230 mm. In the continuous casting process, the tundish steel temperature is 1510℃ to 1525℃, CDT-02 protective slag is used, and the thickness of the liquid slag layer on the crystallizer surface is 9 mm to 13 mm; the billet casting speed is 1.0 m / min to 1.1 m / min, and electromagnetic stirring is used during solidification. The process parameters are set as follows: S1: Roller #1 3.5 HZ-450A, Roller #2 4.0 HZ-400A, S2: Roller #3 3.5 HZ-450A, Roller #4 4.0 HZ-400A; billet thickness is 230 mm.

[0029] The tundish steel temperature is controlled between 1510℃ and 1525℃ to prevent the steel from becoming sticky and reduce the risk of interruption and blockage during the initial casting process. This reduces the viscosity of the molten steel, promoting the flotation of inclusions and improving fluidity, which in turn promotes the uniform dispersion of rare earth inclusions and prevents the aggregation of small particles. The slag layer thickness in the crystallizer is moderate, effectively isolating air, reducing secondary oxidation of the molten steel, stabilizing rare earth yield and fine, dispersed inclusions, while also reducing slag inclusions, porosity, and cracks. Furthermore, electromagnetic stirring technology increases the proportion of equiaxed crystals in the billet. Irregularly oriented equiaxed crystals provide numerous nucleation sites with varying orientations for subsequent recrystallization, which is beneficial for the nucleation and growth of high-mobility, magnetically favorable grains. Fine equiaxed crystals store higher distortion energy during hot deformation, making them more prone to inducing dynamic recrystallization, resulting in more uniform and fine hot-rolled grains. Simultaneously, more grain boundaries can serve as nucleation sites for precipitates and hinder their growth, promoting the formation of fine, dispersed precipitates.

[0030] In a preferred embodiment of the present invention, the equiaxed crystal ratio of the billet is 58%~62%, and the equiaxed crystal grain size is ≤3.5mm.

[0031] S3. The billet is hot-rolled to obtain a hot-rolled plate.

[0032] In a preferred embodiment of the present invention, the hot rolling process includes the following steps: heating the billet in a three-stage heating process, with the first stage at 1120℃~1140℃, the second stage at 1110℃~1120℃, and the third stage at 1095℃~1105℃, for a total heating time of 25min~30min. The billet is then subjected to four passes of rough rolling, with the fourth pass having a reduction rate of <25%, yielding an intermediate billet. The intermediate billet is then reheated, finished rolled, cooled, and coiled to obtain a hot-rolled plate.

[0033] The hot rolling process is as follows: the billet is heated in a multi-stage heating furnace for 25 min to 30 min and then rough rolled in four passes to an intermediate billet of 48 mm. The reduction rate of the fourth rough rolling is less than 25%. After rough rolling, the intermediate billet is reheated to 1100℃ and then fine rolled to 2.25 mm. When the temperature drops to 600℃ to 630℃, it is curled.

[0034] In a preferred embodiment of the invention, the billet is heated in three stages: the first stage has a temperature of 1120℃~1140℃; the second stage has a temperature of 1110℃~1120℃; and the third stage has a temperature of 1095℃~1105℃. Before rolling, the billet is uniformly heated in a three-stage furnace. The first stage, at 1120℃~1140℃, quickly heats the lower-temperature surfaces and corners. The second stage, at 1110℃~1120℃, effectively reduces the temperature difference before and after the furnace, preventing insufficient heating of the billet surface. The final stage, at 1095℃~1105℃, provides a uniform heating temperature throughout the furnace and is the primary heating stage for the billet. Reducing the reduction rate in the final rough rolling pass improves the plate shape and surface quality, and reduces the risk of edge cracking.

[0035] In a preferred embodiment of the present invention, the proportion of the static recrystallization zone in the hot-rolled plate is ≥25%, the normal width of the banded structure is ≤2mm, and the areal density of fine inclusions with a size of 0.2μm~1μm is ≤29000 inclusions / mm². 2 The average size is ≥0.44μm; the areal density of micro-inclusions with a size of 1μm~5μm is ≤14000 inclusions / mm². 2 The average size is ≥2μm.

[0036] In hot-rolled non-oriented silicon steel sheets, the number of fine inclusions is reduced, significantly reducing performance degradation. The average size of these inclusions is ≥0.44μm. The coarsened inclusions can alleviate grain boundary pinning effect and improve microstructure uniformity. Furthermore, after rare earth treatment, the micro-inclusions become significantly spherical. These spherical rare earth composite inclusions can act as heterogeneous nucleation sites, promoting uniform recrystallization, improving texture, adsorbing surrounding harmful elements such as S and N, and reducing secondary precipitation of fine inclusions.

[0037] S4. Hot-rolled plates are normalized, pickled, cold-rolled, and recrystallized annealed to obtain rare earth-treated non-oriented silicon steel.

[0038] In a preferred embodiment of the invention, normalizing is performed by holding at 920°C for 2.5 min in a pure N2 atmosphere. Pickling is performed at 60°C using a mixed acid solution of 15% HCl and 2% HNO3 (by volume). Cold rolling is performed in six passes to a thickness of 0.25 mm. Annealing is performed at 940°C for 3 min in an N2:H2 = 3:1 atmosphere.

[0039] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention provides a rare earth-treated non-oriented silicon steel. The composition and mass percentage content of the rare earth-treated non-oriented silicon steel are as follows: Si: 3.0%~3.5%, Al: 0.8%~1.5%, Mn: 0.3%~0.7%, C≤0.0025%, S≤0.0025%, Ti≤0.0025%, N≤0.0025%, P≤0.015%, with the balance being segregating elements, Fe, and unavoidable impurities, totaling 100%; wherein the segregating element is at least one of La, Ce, and Y. This invention achieves the harmlessness and functionalization control of inclusions through rare earth purification and modification. By adding rare earth elements such as La, Ce, and Y after RH refining; controlling the low oxygen conditions of molten steel to improve the rare earth yield and promote its combination with [O] and [S] to form high-melting-point compounds that float to the surface; and transforming the inherent Al2O3, MnS, and other inclusions in the steel into fine spherical rare earth composite inclusions. It significantly reduces fine, dispersed harmful inclusions with a size <1μm, greatly reducing their pinning effect on magnetic domain walls; spherical rare earth composite inclusions can act as heterogeneous nucleation sites, promoting uniform nucleation of subsequent recrystallized grains. This solves the problem of coarse solidification structure in non-oriented electrical steel leading to stratification of the hot-rolled structure and resulting in uneven finished products.

[0040] 2. This invention utilizes rare earth solid solution segregation and process synergy to optimize the solidification structure. By segregating rare earth atoms dissolved in the matrix at grain boundaries, the grain boundary activation energy is reduced; rare earth compounds act as heterogeneous nucleation cores, promoting the refinement of the solidification structure and the uniform dispersion of inclusions. Fine equiaxed grains promote dynamic recrystallization, resulting in uniform and fine hot-rolled grains. This helps to weaken the inheritance of unfavorable textures and promotes the development of favorable {100} and {110} plane textures.

[0041] 3. This invention combines key process window control to ensure the efficacy of rare earth elements and achieve a performance leap. By combining refining protection, continuous casting and rolling control with composition and process design, the yield of rare earth elements can be effectively improved and their content can be stably controlled, reducing defects such as edge cracks and slag inclusions, improving surface quality and plate shape, and ultimately obtaining non-oriented silicon steel with a good combination of performance. Attached Figure Description

[0042] Figure 1 The inclusion morphology and composition diagram of the solidified billet of non-oriented silicon steel obtained in Example 4 of the present invention. Figure 1 Figure a shows the spherical inclusions of (La,Ce)₂O₂S and AlN composites; Figure b shows the irregular inclusions of AlN composites adsorbed by (La,Ce)₂O₂S; Figure c shows the irregular inclusions of small-sized (La,Ce)₂O₂S; and Figure d shows the near-spherical inclusions of (La,Ce)₂O₂S.

[0043] Figure 2The inclusion morphology and composition diagram of the solidified billet of non-oriented silicon steel obtained in Example 5 of the present invention are shown. Figure 2 Figure a shows a spherical inclusion in the c(La,Ce)AlO3-(La,Ce)2O2S composite containing spherical inclusions encapsulated by AlN; Figure b shows a small-sized (La,Ce)AlO3-(La,Ce)2O2S composite irregular inclusion not fully encapsulated by AlN; Figure c shows a rod-shaped (La,Ce)AlO3-(La,Ce)2O2S composite inclusion encapsulated by AlN; and Figure d shows a large-sized (La,Ce)AlO3-(La,Ce)2O2S composite irregular inclusion encapsulated by AlN.

[0044] Figure 3 The inclusion morphology and composition diagram of the solidified billet of non-oriented silicon steel obtained in Example 6 of the present invention. Figure 3 Figure a shows an AlN-encapsulated (La,Ce)AlO3 composite irregular inclusion, and Figure b shows an AlN-encapsulated large-size (La,Ce)AlO3-(La,Ce)2O2S composite irregular inclusion.

[0045] Figure 4 The image shows the inclusion morphology and composition of the solidified billet of non-oriented silicon steel prepared in Comparative Example 1 of this invention. Figure 4 Figure a shows the complex inclusions formed between oxides and sulfides, Figure b shows the complex inclusions of oxides, Figure c shows the rod-shaped AlN inclusions, and Figure d shows the irregular AlN inclusions.

[0046] Figure 5 This is a solidification microstructure diagram of the non-oriented silicon steel of the present invention with different rare earth contents. Figure 5 Figure a shows the 0 wt% value, figure b shows the 0.0021 wt% value, figure c shows the 0.0034 wt% value, and figure d shows the 0.0058 wt% value. Detailed Implementation

[0047] 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.

[0048] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0049] The following specific examples will provide further explanation.

[0050] Example 1 A rare earth-treated non-oriented silicon steel is composed of the following components by mass percentage: 3.2% Si, 0.9% Al, 0.4% Mn, 0.0015% C, 0.0006% S, 0.0005% Ti, 0.0007% N, 0.01% P, 0.002% La, and 0.003% Ce, with the balance being Fe and unavoidable impurities, totaling 100%.

[0051] The method for preparing the above-mentioned rare earth-treated non-oriented silicon steel includes the following steps: S1, RH refining: The average thickness of the refining slag when the ladle enters the station is 90mm, and the RH inlet temperature is 1580℃. Then the following steps are performed to treat the molten steel: (1) Decarburization and deoxidation, wherein the oxygen content at the end of decarburization is 200ppm; (2) Adding desulfurizing agent and pure rare earth material, and after adding the desulfurizing agent, circulating and stirring for 7.5min; (3) After the RH vacuum refining is completed, the molten steel is required to be calmed for 16min; (4) The molten steel leaves the station via RH, and the main types of inclusions in the molten steel are (La / Ce)AlO3, (La / Ce)2O2S and (La / Ce) x S y The molten steel is composed of the following components by mass percentage: 3.05% Si, 0.72% Al, 0.37% Mn, 0.038% C, 0.009% S, 0.0022% Ti, 0.0034% N, 0.01% P, with the balance being Fe and unavoidable impurities, totaling 100%.

[0052] S2, Continuous casting: The molten steel temperature in the tundish is 1515℃, CDT-02 protective slag is used, and the thickness of the liquid slag layer on the surface of the crystallizer is 10mm; the billet casting speed is 1.1m / min, and electromagnetic stirring is used in the solidification process. The process parameters are set as follows: #1 roller 3.5HZ-450A, #2 roller 4.0HZ-400A, #3 roller 3.5HZ-450A, #4 roller 4.0HZ-400A; a billet with a thickness of 230mm is obtained.

[0053] S3. Hot rolling: The billet is heated in three stages for 30 minutes. The temperature of the first heating stage is 1130℃; the temperature of the second heating stage is 1110℃; the temperature of the third soaking stage is 1100℃; then it is rough rolled in four passes to a 48mm thick intermediate billet, with a reduction rate of 20% in the fourth rough rolling; after rough rolling, the intermediate billet is reheated to 1100℃ and then finished rolled to 2.25mm. When the temperature drops to 620℃, it is curled.

[0054] S4. Subsequent treatments include normalizing, pickling, cold rolling, and annealing. Normalizing involves holding at 920℃ for 2.5 minutes in a pure N2 atmosphere. Pickling is performed using a mixed acid solution of 15% HCl and 2% HNO3 at 60℃. Cold rolling is done in six passes to a thickness of 0.25 mm. Annealing is performed at 940℃ for 3 minutes in an N2:H2 = 3:1 atmosphere.

[0055] Testing revealed the following: Solidified billet: equiaxed grain ratio was 61.3%; equiaxed grain size was 2.4 mm. Hot-rolled plate: average normal width of banded structure was 1.2 mm; static recrystallization zone ratio was 30%; fine inclusions with a size of 0.2 μm to 1 μm had a surface density of 29,000 inclusions / mm². 2 The average size is 0.44 μm, and the areal density of micro-inclusions with sizes ranging from 1 μm to 5 μm is 14,000 inclusions / mm². 2 The average size is 2μm.

[0056] Example 2 A rare earth-treated non-oriented silicon steel is composed of the following components by mass percentage: 3.5% Si, 0.8% Al, 0.3% Mn, 0.0012% C, 0.0005% S, 0.0006% Ti, 0.0006% N, 0.01% P, 0.003% Y, with the balance being Fe and unavoidable impurities, totaling 100%.

[0057] The method for preparing the above-mentioned rare earth-treated non-oriented silicon steel includes the following steps: S1, RH refining: The average thickness of the refining slag when the ladle enters the station is 85mm, and the RH inlet temperature is 1580℃; then the following steps are performed to treat the molten steel: (1) decarburization and deoxidation, the oxygen content at the end of decarburization is 220ppm; (2) adding desulfurizing agent and pure rare earth material, after adding the desulfurizing agent, the mixture is circulated and stirred for 8min; (3) after the RH vacuum refining is completed, the molten steel is required to be calmed for 16min; (4) the molten steel leaves the station via RH, the main types of inclusions in the molten steel are YAlO3, Y2O2S and YS. The molten steel is composed of the following components by mass percentage: 3.35%Si, 0.63%Al, 0.27%Mn, 0.03%C, 0.008%S, 0.0024%Ti, 0.0032%N, 0.01%P, with the balance being Fe and unavoidable impurities, totaling 100%.

[0058] S2, Continuous casting: The molten steel temperature in the tundish is 1510℃, CDT-02 protective slag is used, and the thickness of the liquid slag layer on the surface of the crystallizer is 12mm; the billet casting speed is 1.1m / min, and electromagnetic stirring is used in the solidification process. The process parameters are set as follows: #1 roller 3.5HZ-450A, #2 roller 4.0HZ-400A, #3 roller 3.5HZ-450A, #4 roller 4.0HZ-400A; a billet with a thickness of 230mm is obtained.

[0059] S3. Hot rolling: The billet is heated in three stages for 30 minutes. The temperature of the first heating stage is 1130℃; the temperature of the second heating stage is 1110℃; the temperature of the third soaking stage is 1100℃; then it is rough rolled in four passes to an intermediate billet of 48mm, with a reduction rate of 20% in the fourth rough rolling; after rough rolling, the intermediate billet is reheated to 1100℃ and then finished rolled to 2.25mm. When the temperature drops to 620℃, it is curled.

[0060] S4. Subsequent treatments include normalizing, pickling, cold rolling, and annealing. Normalizing involves holding at 920℃ for 2.5 minutes in a pure N2 atmosphere. Pickling is performed using a mixed acid solution of 15% HCl and 2% HNO3 at 60℃. Cold rolling is done in six passes to a thickness of 0.25 mm. Annealing is performed at 940℃ for 3 minutes in an N2:H2 = 3:1 atmosphere.

[0061] Testing revealed the following: Solidified billet: equiaxed grain ratio was 61.0%; equiaxed grain size was 2.3 mm. Hot-rolled plate: static recrystallization zone ratio was 28%; average normal width of banded structure was 1.5 mm; areal density of fine inclusions (0.2 μm~1 μm) was 29,000 inclusions / mm². 2 The average size is 0.44 μm, and the areal density of micro-inclusions with sizes ranging from 1 μm to 5 μm is 14,000 inclusions / mm². 2 The average size is 2μm.

[0062] Example 3 A rare earth-treated non-oriented silicon steel is composed of the following components by mass percentage: 3.5% Si, 0.8% Al, 0.3% Mn, 0.0012% C, 0.0007% S, 0.0004% Ti, 0.0008% N, 0.01% P, 0.001% La, 0.001% Ce, 0.001% Y, with the balance being Fe and unavoidable impurities.

[0063] The method for preparing the above-mentioned rare earth-treated non-oriented silicon steel includes the following steps: S1, RH refining: The average thickness of the refining slag when the ladle enters the station is 90mm, and the RH inlet temperature is 1580℃; then the following steps are performed to treat the molten steel: (1) decarburization and deoxidation, the oxygen content at the end of decarburization is 210ppm; (2) adding desulfurizing agent and pure rare earth material, after adding the desulfurizing agent, the mixture is circulated and stirred for 8min; (3) after the RH vacuum refining is completed, the molten steel is required to be calmed for 15min; (4) the molten steel leaves the station via RH, the main types of inclusions in the molten steel are (La / Ce)AlO3, (La / Ce / Y)2O2S and YS. The molten steel is composed of the following components by mass percentage: 3.35%Si, 0.63%Al, 0.27%Mn, 0.03%C, 0.01%S, 0.002%Ti, 0.0035%N, 0.01%P, with the balance being Fe and unavoidable impurities, totaling 100%.

[0064] S2, Continuous casting: The molten steel temperature in the tundish is 1510℃, CDT-02 protective slag is used, and the thickness of the liquid slag layer on the surface of the crystallizer is 12mm; the billet casting speed is 1.1m / min, and electromagnetic stirring is used in the solidification process. The process parameters are set as follows: #1 roller 3.5HZ-450A, #2 roller 4.0HZ-400A, #3 roller 3.5HZ-450A, #4 roller 4.0HZ-400A; a billet with a thickness of 230mm is obtained.

[0065] S3. Hot rolling: The billet is heated in three stages for 30 minutes. The temperature of the first heating stage is 1130℃; the temperature of the second heating stage is 1110℃; the temperature of the third soaking stage is 1100℃; then it is rough rolled in four passes to an intermediate billet of 48mm, with a reduction rate of 20% in the fourth rough rolling; after rough rolling, the intermediate billet is reheated to 1100℃ and then finished rolled to 2.25mm. When the temperature drops to 620℃, it is curled.

[0066] S4. Subsequent treatments include normalizing, pickling, cold rolling, and annealing. Normalizing involves holding at 920℃ for 2.5 minutes in a pure N2 atmosphere. Pickling is performed using a mixed acid solution of 15% HCl and 2% HNO3 at 60℃. Cold rolling is done in six passes to a thickness of 0.25 mm. Annealing is performed at 940℃ for 3 minutes in an N2:H2 = 3:1 atmosphere.

[0067] Testing revealed the following: Solidified billet: equiaxed grain ratio was 61.0%; equiaxed grain size was 2.8 mm. Hot-rolled plate: static recrystallization zone ratio was 28%; average normal width of banded structure was 1.5 mm; areal density of fine inclusions (0.2 μm~1 μm) was 29,000 inclusions / mm². 2 The average size is 0.44 μm, and the areal density of micro-inclusions with sizes ranging from 1 μm to 5 μm is 14,000 inclusions / mm². 2 The average size is 2μm.

[0068] Example 4 A rare earth-treated non-oriented silicon steel is composed of the following components by mass percentage: 3.2% Si, 0.9% Al, 0.4% Mn, 0.0015% C, 0.0008% S, 0.0007% Ti, 0.0009% N, 0.01% P, 0.002% La, and 0.0038% Ce, with the balance being Fe and unavoidable impurities, totaling 100%.

[0069] The method for preparing the above-mentioned rare earth-treated non-oriented silicon steel includes the following steps: S1, RH refining: The average thickness of the refining slag when the ladle enters the station is 100mm, and the RH inlet temperature is 1590℃; then the following steps are performed to treat the molten steel: (1) Decarburization and deoxidation, the oxygen content at the end of decarburization is 260ppm; (2) Add desulfurizing agent and pure rare earth material, after adding the desulfurizing agent, circulate and stir for 6min; (3) After the RH vacuum refining is completed, the molten steel is required to be calmed for 15min; (4) The molten steel leaves the station via RH, and the main types of inclusions in the molten steel are (La / Ce)AlO3, (La / Ce)2O2S and (La / Ce) x S y Molten steel is composed of the following components by mass percentage: 3.05% Si, 0.72% Al, 0.37% Mn, 0.04% C, 0.011% S, 0.0025% Ti, 0.0036% N, 0.01% P, with the balance being Fe and unavoidable impurities, totaling 100%.

[0070] S2, Continuous casting: The molten steel temperature in the tundish is 1525℃, CDT-02 protective slag is used, and the thickness of the liquid slag layer on the surface of the crystallizer is 13mm; the billet casting speed is 1.0m / min, and electromagnetic stirring is used in the solidification process. The process parameters are set as follows: No. 1 roller 3.5HZ-450A, No. 2 roller 4.0HZ-400A, No. 3 roller 3.5HZ-450A, No. 4 roller 4.0HZ-400A; a billet with a thickness of 230mm is obtained.

[0071] S3. Hot rolling: The billet is heated in three stages for 30 minutes. The temperature of the first heating stage is 1130℃; the temperature of the second heating stage is 1110℃; the temperature of the third soaking stage is 1100℃; then it is rough rolled in four passes to an intermediate billet of 48mm, with a reduction rate of 24% in the fourth rough rolling; after rough rolling, the intermediate billet is reheated to 1100℃ and then finished rolled to 2.25mm. When the temperature drops to 620℃, it is curled.

[0072] S4. Subsequent treatments include normalizing, pickling, cold rolling, and annealing. Normalizing involves holding at 920℃ for 2.5 minutes in a pure N2 atmosphere. Pickling is performed using a mixed acid solution of 15% HCl and 2% HNO3 at 60℃. Cold rolling is done in six passes to a thickness of 0.25 mm. Annealing is performed at 940℃ for 3 minutes in an N2:H2 = 3:1 atmosphere.

[0073] Testing revealed the following: Solidified billet: equiaxed grain ratio was 58.8%; equiaxed grain size was 3.2 mm. Hot-rolled plate: static recrystallization zone ratio was 25%; average normal width of banded structure was 1.2 mm; areal density of fine inclusions (0.2 μm~1 μm) was 29,000 inclusions / mm². 2 The average size is 0.44 μm, and the areal density of micro-inclusions with sizes ranging from 1 μm to 5 μm is 14,000 inclusions / mm². 2 The average size is 2μm.

[0074] Example 5 The difference from Example 1 is that the rare earth-treated non-oriented silicon steel is composed of the following components by mass percentage: 3.2% Si, 0.9% Al, 0.4% Mn, 0.0015% C, 0.0006% S, 0.0008% Ti, 0.0005% N, 0.01% P, 0.001% La, and 0.0024% Ce, with the balance being Fe and unavoidable impurities, totaling 100%. The preparation method of the rare earth-treated non-oriented silicon steel includes the following steps:

[0075] S1, RH refining: The average thickness of the refining slag when the ladle enters the station is 90mm, and the RH inlet temperature is 1580℃. Then the following steps are performed to treat the molten steel: (1) Decarburization and deoxidation, wherein the oxygen content at the end of decarburization is 200ppm; (2) Adding desulfurizing agent and pure rare earth material, and after adding the desulfurizing agent, circulating and stirring for 7.5min; (3) After the RH vacuum refining is completed, the molten steel is required to be calmed for 16min; (4) The molten steel leaves the station via RH, and the main types of inclusions in the molten steel are (La / Ce)AlO3, (La / Ce)2O2S and (La / Ce) x S y Molten steel is composed of the following components by mass percentage: 3.5% Si, 0.72% Al, 0.37% Mn, 0.038% C, 0.009% S, 0.0026% Ti, 0.003% N, 0.01% P, with the balance being Fe and unavoidable impurities, totaling 100%.

[0076] S2, Continuous casting: The molten steel temperature in the tundish is 1515℃, CDT-02 protective slag is used, and the thickness of the liquid slag layer on the surface of the crystallizer is 10mm; the billet casting speed is 1.1m / min, and electromagnetic stirring is used in the solidification process. The process parameters are set as follows: #1 roller 3.5HZ-450A, #2 roller 4.0HZ-400A, #3 roller 3.5HZ-450A, #4 roller 4.0HZ-400A; a billet with a thickness of 230mm is obtained.

[0077] S3. Hot rolling: The billet is heated in three stages for 30 minutes. The temperature of the first heating stage is 1130℃; the temperature of the second heating stage is 1110℃; the temperature of the third soaking stage is 1100℃; then it is rough rolled in four passes to a 48mm thick intermediate billet, with a reduction rate of 20% in the fourth rough rolling; after rough rolling, the intermediate billet is reheated to 1100℃ and then finished rolled to 2.25mm. When the temperature drops to 620℃, it is curled.

[0078] S4. Subsequent treatments include normalizing, pickling, cold rolling, and annealing. Normalizing involves holding at 920℃ for 2.5 minutes in a pure N2 atmosphere. Pickling is performed using a mixed acid solution of 15% HCl and 2% HNO3 at 60℃. Cold rolling is done in six passes to a thickness of 0.25 mm. Annealing is performed at 940℃ for 3 minutes in an N2:H2 = 3:1 atmosphere.

[0079] Testing revealed the following: Solidified billet: equiaxed grain ratio was 60.8%; equiaxed grain size was 2.8 mm. Hot-rolled plate: static recrystallization zone ratio was 26%; average normal width of banded structure was 1.2 mm; areal density of fine inclusions (0.2 μm~1 μm) was 29,000 inclusions / mm². 2 The average size is 0.42 μm, and the areal density of micro-inclusions with sizes ranging from 1 μm to 5 μm is 19,000 inclusions / mm². 2 The average size is 2μm.

[0080] Example 6 The difference from Example 1 is that the rare earth-treated non-oriented silicon steel is composed of the following components by mass percentage: 3.2% Si, 0.9% Al, 0.4% Mn, 0.0015% C, 0.0009% S, 0.0009% Ti, 0.0008% N, 0.01% P, 0.001% La, and 0.0011% Ce, with the balance being Fe and unavoidable impurities, totaling 100%. The preparation method of the rare earth-treated non-oriented silicon steel includes the following steps:

[0081] S1, RH refining: The average thickness of the refining slag when the ladle enters the station is 90mm, and the RH inlet temperature is 1580℃. Then the following steps are performed to treat the molten steel: (1) Decarburization and deoxidation, wherein the oxygen content at the end of decarburization is 200ppm; (2) Adding desulfurizing agent and pure rare earth material, and after adding the desulfurizing agent, circulating and stirring for 7.5min; (3) After the RH vacuum refining is completed, the molten steel is required to be calmed for 16min; (4) The molten steel leaves the station via RH, and the main types of inclusions in the molten steel are (La / Ce)AlO3, (La / Ce)2O2S and (La / Ce) x S yThe molten steel is composed of the following components by mass percentage: 3.05% Si, 0.72% Al, 0.37% Mn, 0.038% C, 0.012% S, 0.0028% Ti, 0.0035% N, 0.01% P, with the balance being Fe and unavoidable impurities, totaling 100%.

[0082] S2, Continuous casting: The molten steel temperature in the tundish is 1515℃, CDT-02 protective slag is used, and the thickness of the liquid slag layer on the surface of the crystallizer is 10mm; the billet casting speed is 1.1m / min, and electromagnetic stirring is used in the solidification process. The process parameters are set as follows: #1 roller 3.5HZ-450A, #2 roller 4.0HZ-400A, #3 roller 3.5HZ-450A, #4 roller 4.0HZ-400A; a billet with a thickness of 230mm is obtained.

[0083] S3. Hot rolling: The billet is heated in three stages for 30 minutes. The temperature of the first heating stage is 1130℃; the temperature of the second heating stage is 1110℃; the temperature of the third soaking stage is 1100℃; then it is rough rolled in four passes to a 48mm thick intermediate billet, with a reduction rate of 20% in the fourth rough rolling; after rough rolling, the intermediate billet is reheated to 1100℃ and then finished rolled to 2.25mm. When the temperature drops to 620℃, it is curled.

[0084] S4. Subsequent treatments include normalizing, pickling, cold rolling, and annealing. Normalizing involves holding at 920℃ for 2.5 minutes in a pure N2 atmosphere. Pickling is performed using a mixed acid solution of 15% HCl and 2% HNO3 at 60℃. Cold rolling is done in six passes to a thickness of 0.25 mm. Annealing is performed at 940℃ for 3 minutes in an N2:H2 = 3:1 atmosphere.

[0085] Testing revealed the following: Solidified billet: equiaxed grain ratio was 58.8%; equiaxed grain size was 3.2 mm. Hot-rolled plate: static recrystallization zone ratio was 25%; average normal width of banded structure was 1.2 mm; areal density of fine inclusions (0.2 μm~1 μm) was 32,000 inclusions / mm². 2 The average size is 0.40 μm, and the areal density of micro-inclusions with sizes ranging from 1 μm to 5 μm is 18,000 inclusions / mm². 2 The average size is 2.2 μm.

[0086] Comparative Example 1 A non-oriented silicon steel is composed of the following components by mass percentage: 3.2% Si, 0.9% Al, 0.4% Mn, 0.0015% C, 0.0010% S, 0.0010% Ti, 0.0010% N, 0.01% P, with the balance being Fe and unavoidable impurities, totaling 100%.

[0087] The above-mentioned method for preparing non-oriented silicon steel includes the following steps: S1, RH refining: The average thickness of the refining slag when the ladle enters the station is 100mm, and the RH inlet temperature is 1590℃; then the following steps are performed to treat the molten steel: (1) decarburization and deoxidation, the oxygen content at the end of decarburization is 260ppm; (2) adding desulfurizing agent, after adding the desulfurizing agent, the molten steel is circulated and stirred for 6min; (3) after the RH vacuum refining is completed, the molten steel is required to be calmed for 15min; (4) the molten steel leaves the station via RH, the main types of inclusions in the molten steel are Al2O3, AlN, MnS, etc., in the form of angular / long strips. The molten steel is composed of the following components by mass percentage: 3.5%Si, 0.72%Al, 0.37%Mn, 0.04%C, 0.013%S, 0.003%Ti, 0.0038%N, 0.01%P, with the balance being Fe and unavoidable impurities, totaling 100%.

[0088] S2, Continuous casting: The molten steel temperature in the tundish is 1525℃, CDT-02 protective slag is used, and the thickness of the liquid slag layer on the surface of the crystallizer is 13mm; the billet casting speed is 1.0m / min, and electromagnetic stirring is used in the solidification process. The process parameters are set as follows: No. 1 roller 3.5HZ-450A, No. 2 roller 4.0HZ-400A, No. 3 roller 3.5HZ-450A, No. 4 roller 4.0HZ-400A; a billet with a thickness of 230mm is obtained.

[0089] S3. Hot rolling: The billet is heated in three stages for 30 minutes. The temperature of the first heating stage is 1130℃; the temperature of the second heating stage is 1110℃; the temperature of the third soaking stage is 1100℃; then it is rough rolled in four passes to an intermediate billet of 48mm. The reduction rate of the fourth rough rolling is 24%. After the rough rolling is completed, the intermediate billet is reheated to 1100℃ and then finished rolled to 2.25mm. When the temperature drops to 620℃, it is curled.

[0090] S4. Subsequent treatments include normalizing, pickling, cold rolling, and annealing. Normalizing involves holding at 920℃ for 2.5 minutes in a pure N2 atmosphere. Pickling is performed using a mixed acid solution of 15% HCl and 2% HNO3 at 60℃. Cold rolling is done in six passes to a thickness of 0.25 mm. Annealing is performed at 940℃ for 3 minutes in an N2:H2 = 3:1 atmosphere.

[0091] Testing revealed the following: Solidified billet: equiaxed grain ratio was 55.0%; equiaxed grain size was 4.3 mm. Hot-rolled plate: static recrystallization zone ratio was 24%; average normal width of banded structure was 2.6 mm; areal density of fine inclusions (0.2 μm~1 μm) was 37,000 inclusions / mm². 2 The average size is 0.27 μm, and the areal density of micro-inclusions with sizes ranging from 1 μm to 5 μm is 24,000 inclusions / mm². 2 The average size is 1.4 μm.

[0092] Comparative Example 2 The difference from Example 1 is that in step S1, the average thickness of the refining slag when the ladle enters the station is 70 mm, and the RH inlet temperature is 1610℃; then the following steps are performed to treat the molten steel: (1) decarburization and deoxidation, with an oxygen content of 340 ppm at the end of decarburization; (2) addition of desulfurizing agent and pure rare earth material, with circulation stirring for 5 min after the desulfurizing agent is added; (3) after RH vacuum refining is completed, the molten steel is required to be calmed for 10 min. All other parameters are the same. The specific preparation method includes the following steps:

[0093] S1, RH refining: The average thickness of the refining slag when the ladle enters the station is 70mm, and the RH inlet temperature is 1610℃. Then the following steps are performed to treat the molten steel: (1) Decarburization and deoxidation, wherein the oxygen content at the end of decarburization is 340ppm; (2) Adding desulfurizing agent and pure rare earth material, and circulating and stirring for 5min after adding the desulfurizing agent; (3) After the RH vacuum refining is completed, the molten steel is required to be calmed for 10min; (4) The molten steel leaves the station via RH, and the main types of inclusions in the molten steel are (La / Ce)AlO3, (La / Ce)2O2S and (La / Ce) x S y .

[0094] S2, Continuous casting: The molten steel temperature in the tundish is 1515℃, CDT-02 protective slag is used, and the thickness of the liquid slag layer on the surface of the crystallizer is 10mm; the billet casting speed is 1.1m / min, and electromagnetic stirring is used in the solidification process. The process parameters are set as follows: #1 roller 3.5HZ-450A, #2 roller 4.0HZ-400A, #3 roller 3.5HZ-450A, #4 roller 4.0HZ-400A; a billet with a thickness of 230mm is obtained.

[0095] S3. Hot rolling: The billet is heated in three stages for 30 minutes. The temperature of the first heating stage is 1130℃; the temperature of the second heating stage is 1110℃; the temperature of the third soaking stage is 1100℃; then it is rough rolled in four passes to a 48mm thick intermediate billet, with a reduction rate of 20% in the fourth rough rolling; after rough rolling, the intermediate billet is reheated to 1100℃ and then finished rolled to 2.25mm. When the temperature drops to 620℃, it is curled.

[0096] S4. Subsequent treatments include normalizing, pickling, cold rolling, and annealing. Normalizing involves holding at 920℃ for 2.5 minutes in a pure N2 atmosphere. Pickling is performed using a mixed acid solution of 15% HCl and 2% HNO3 at 60℃. Cold rolling is done in six passes to a thickness of 0.25 mm. Annealing is performed at 940℃ for 3 minutes in an N2:H2 = 3:1 atmosphere.

[0097] Testing revealed the following: Solidified billet: equiaxed grain ratio was 58.0%; equiaxed grain size was 3.8 mm. Hot-rolled plate: static recrystallization zone ratio was 26%; average normal width of banded structure was 1.9 mm; areal density of fine inclusions (0.2 μm~1 μm) was 33,000 inclusions / mm². 2 The average size is 0.37 μm, and the areal density of micro-inclusions with sizes ranging from 1 μm to 5 μm is 22,000 inclusions / mm². 2 The average size is 1.5 μm.

[0098] Comparative Example 3 The difference from Example 1 is that in step S2, the casting speed is 1.2 m / min, and electromagnetic stirring is not used. All other parameters are the same. The specific preparation method includes the following steps:

[0099] S1, RH refining: The average thickness of the refining slag when the ladle enters the station is 90mm, and the RH inlet temperature is 1580℃. Then the following steps are performed to treat the molten steel: (1) Decarburization and deoxidation, wherein the oxygen content at the end of decarburization is 200ppm; (2) Adding desulfurizing agent and pure rare earth material, and after adding the desulfurizing agent, circulating and stirring for 7.5min; (3) After the RH vacuum refining is completed, the molten steel is required to be calmed for 16min; (4) The molten steel leaves the station via RH, and the main types of inclusions in the molten steel are (La / Ce)AlO3, (La / Ce)2O2S and (La / Ce) x S y .

[0100] S2, Continuous casting: The temperature of molten steel in the tundish is 1515℃, CDT-02 protective slag is used, and the thickness of the liquid slag layer on the surface of the crystallizer is 10mm; the billet casting speed is 1.2m / min, and a billet with a thickness of 230mm is obtained.

[0101] S3. Hot rolling: The billet is heated in three stages for 30 minutes. The temperature of the first heating stage is 1130℃; the temperature of the second heating stage is 1110℃; the temperature of the third soaking stage is 1100℃; then it is rough rolled in four passes to a 48mm thick intermediate billet, with a reduction rate of 20% in the fourth rough rolling; after rough rolling, the intermediate billet is reheated to 1100℃ and then finished rolled to 2.25mm. When the temperature drops to 620℃, it is curled.

[0102] S4. Subsequent treatments include normalizing, pickling, cold rolling, and annealing. Normalizing involves holding at 920℃ for 2.5 minutes in a pure N2 atmosphere. Pickling is performed using a mixed acid solution of 15% HCl and 2% HNO3 at 60℃. Cold rolling is done in six passes to a thickness of 0.25 mm. Annealing is performed at 940℃ for 3 minutes in an N2:H2 = 3:1 atmosphere.

[0103] Testing revealed the following: Solidified billet: equiaxed grain ratio was 35.0%; equiaxed grain size was 2.8 mm. Hot-rolled plate: static recrystallization zone ratio was 12%; average normal width of banded structure was 2.8 mm; fine inclusions with a size of 0.2 μm to 1 μm had a surface density of 31,000 inclusions / mm². 2 The average size is 0.4 μm, and the areal density of micro-inclusions with sizes ranging from 1 μm to 5 μm is 18,000 inclusions / mm². 2 The average size is 1.9 μm.

[0104] Comparative Example 4 The difference from Example 1 is as follows: In step S3, a three-stage heating process is used for the cast billet for 25 minutes. The temperature of the first heating stage is 1150℃; the temperature of the second heating stage is 1135℃; and the temperature of the third soaking stage is 1120℃. Then, the billet is rough rolled in four passes to a 56mm intermediate billet, with a reduction rate of 25% in the fourth rough rolling pass. After rough rolling, the intermediate billet is reheated to 1100℃ and then finish rolled to 2.25mm. When the temperature drops to 650℃, the billet is curled. All other parameters are the same. The specific preparation method includes the following steps:

[0105] S1, RH refining: The average thickness of the refining slag when the ladle enters the station is 90mm, and the RH inlet temperature is 1580℃. Then the following steps are performed to treat the molten steel: (1) Decarburization and deoxidation, wherein the oxygen content at the end of decarburization is 200ppm; (2) Adding desulfurizing agent and pure rare earth material, and after adding the desulfurizing agent, circulating and stirring for 7.5min; (3) After the RH vacuum refining is completed, the molten steel is required to be calmed for 16min; (4) The molten steel leaves the station via RH, and the main types of inclusions in the molten steel are (La / Ce)AlO3, (La / Ce)2O2S and (La / Ce) x S y .

[0106] S2, Continuous casting: The molten steel temperature in the tundish is 1515℃, CDT-02 protective slag is used, and the thickness of the liquid slag layer on the surface of the crystallizer is 10mm; the billet casting speed is 1.1m / min, and electromagnetic stirring is used in the solidification process. The process parameters are set as follows: #1 roller 3.5HZ-450A, #2 roller 4.0HZ-400A, #3 roller 3.5HZ-450A, #4 roller 4.0HZ-400A; a billet with a thickness of 230mm is obtained.

[0107] S3. Hot rolling: The billet is heated in three stages for 25 minutes. The temperature of the first heating stage is 1150℃; the temperature of the second heating stage is 1135℃; the temperature of the third soaking stage is 1120℃; then it is rough rolled in four passes to a 56mm thick intermediate billet, with a reduction rate of 25% in the fourth rough rolling; after rough rolling, the intermediate billet is reheated to 1100℃ and then finished rolled to 2.25mm. When the temperature drops to 650℃, it is curled.

[0108] S4. Subsequent treatments include normalizing, pickling, cold rolling, and annealing. Normalizing involves holding at 920℃ for 2.5 minutes in a pure N2 atmosphere. Pickling is performed using a mixed acid solution of 15% HCl and 2% HNO3 at 60℃. Cold rolling is done in six passes to a thickness of 0.25 mm. Annealing is performed at 940℃ for 3 minutes in an N2:H2 = 3:1 atmosphere.

[0109] Testing revealed the following: Solidified billet: equiaxed grain ratio was 61.3%; equiaxed grain size was 2.4 mm. Hot-rolled plate: static recrystallization zone ratio was 26%; average normal width of banded structure was 1.3 mm; areal density of fine inclusions (0.2 μm~1 μm) was 29,000 inclusions / mm². 2 The average size is 0.44 μm, and the areal density of micro-inclusions with sizes ranging from 1 μm to 5 μm is 15,000 inclusions / mm². 2 The average size is 1.4 μm.

[0110] The non-oriented silicon steels of Examples 1 to 6 and Comparative Examples 1 to 4 were subjected to structural and performance tests. These tests included the proportion of equiaxed crystals, the size of equiaxed crystal grains, the proportion of static recrystallization zones, the average width of banded structures in the normal direction, the areal density and average size of fine inclusions, and the areal density and average size of micro-inclusions.

[0111] The proportion of equiaxed crystals directly determines the uniformity of the billet's microstructure: a higher proportion means a larger share of equiaxed crystals without obvious directionality, avoiding compositional segregation and anisotropy in mechanical properties caused by columnar crystals. This results in more uniform deformation during subsequent hot and cold rolling, reducing defects such as cracks and warping. The size of equiaxed crystal grains needs to be controlled within a moderate range: excessively large grains lead to decreased strength and toughness in the billet, making it prone to grain breakage and forming localized structural defects during subsequent rolling. The proportion of the static recrystallization zone reflects the degree of recrystallization of grains after hot rolling: a higher proportion indicates more complete recrystallization of deformed grains during hot rolling, lower residual stress, more uniform grain morphology, less resistance to magnetic domain rotation and movement, lower iron loss, and higher magnetic induction in silicon steel. Banded structures are the residues of compositional or structural segregation in the billet after hot rolling. The narrower the band, the less severe the compositional and structural segregation, and the more uniform the magnetic and mechanical properties of the silicon steel. The core effect of fine inclusions is "pinning grain boundaries + hindering magnetic domain movement": the lower the areal density, i.e., ≤29,000 inclusions / mm in the example, the better. 2 The more moderate the average size (0.40μm~0.44μm in the examples), the less resistance it poses to grain boundary movement and magnetic domain rotation. Microscopic inclusions, due to their larger size, have a more significant negative impact on the properties of silicon steel; the lower the areal density (≤19000 inclusions / mm² in the examples), the better. 2 The average size is controlled at around 2μm, which reduces the physical resistance to the movement of magnetic domain walls.

[0112] This invention significantly improves the microstructure uniformity of non-oriented silicon steel through rare earth element regulation and full-process optimization. Specifically, the addition of rare earth elements, namely La, Ce, Y, or combinations thereof, is the core. Compared with Comparative Example 1 without rare earth elements, the solidified billet of this embodiment has a 5.8%~6.3% higher equiaxed crystal ratio, a more uniform equiaxed crystal grain size of 2.3mm~3.2mm, a reduction of more than 42.3% in the width of the hot-rolled strip microstructure, and a reduction of more than 21.6% in the areal density of inclusions. Furthermore, rare earth elements can modify harmful inclusions such as Al2O3 and AlN into more rounded (La / Ce)AlO3 and Y2O2S, reducing their destructive effect on microstructure and properties. Process parameter optimization is indispensable. A combination of parameters including RH refining slag thickness ≥80mm, inlet temperature 1560℃~1590℃, decarburization endpoint oxygen content ≤260ppm, desulfurizing agent stirring time 6min~8min, settling time 15min~16min, continuous casting speed 1.0m / min~1.1m / min with electromagnetic stirring, hot rolling three-stage heating temperature 1100℃~1130℃, and fourth roughing reduction rate ≤24% can further optimize the microstructure and inclusion state. Processes deviating from the optimized range, such as excessively thin refining slag, excessively high temperature, lack of electromagnetic stirring in continuous casting, and excessively high hot rolling temperature, will lead to a decrease in the proportion of equiaxed crystals, widening of banded structures, and deterioration of inclusion distribution. For example, in Comparative Example 3, due to the lack of electromagnetic stirring, the proportion of equiaxed crystals was only 35.0%, and the proportion of the static recrystallization zone dropped to 12%.

[0113] Figure 1 The inclusion morphology and composition diagram of the solidified billet of non-oriented silicon steel obtained in Example 4 of the present invention. Figure 1 Figure a shows the spherical inclusions of (La,Ce)₂O₂S and AlN composites; Figure b shows the irregular inclusions of AlN composites adsorbed by (La,Ce)₂O₂S; Figure c shows the irregular inclusions of small-sized (La,Ce)₂O₂S; and Figure d shows the near-spherical inclusions of (La,Ce)₂O₂S. Figure 2 The inclusion morphology and composition diagram of the solidified billet of non-oriented silicon steel obtained in Example 5 of the present invention are shown. Figure 2 Figure a shows a spherical inclusion in the c(La,Ce)AlO3-(La,Ce)2O2S composite containing spherical inclusions encapsulated by AlN; Figure b shows a small-sized (La,Ce)AlO3-(La,Ce)2O2S composite irregular inclusion not fully encapsulated by AlN; Figure c shows a rod-shaped (La,Ce)AlO3-(La,Ce)2O2S composite inclusion encapsulated by AlN; and Figure d shows a large-sized (La,Ce)AlO3-(La,Ce)2O2S composite irregular inclusion encapsulated by AlN. Figure 3 The inclusion morphology and composition diagram of the solidified billet of non-oriented silicon steel obtained in Example 6 of the present invention. Figure 3Figure a shows an AlN-encapsulated (La,Ce)AlO3 composite irregular inclusion, and Figure b shows an AlN-encapsulated large-size (La,Ce)AlO3-(La,Ce)2O2S composite irregular inclusion. Small-size inclusions refer to those with an equivalent circle diameter less than or equal to 1 μm, while large-size inclusions refer to those with an equivalent circle diameter greater than 1 μm. Figure 4 The image shows the inclusion morphology and composition of the solidified billet of non-oriented silicon steel prepared in Comparative Example 1 of this invention. Figure 4 Figure a shows the complex inclusions formed between oxides and sulfides, Figure b shows the complex inclusions of oxides, Figure c shows the rod-shaped AlN inclusions, and Figure d shows the irregular AlN inclusions. Figure 4 The oxides in diagram a are MgO, Al₂O₃, and CaO, and the sulfide is CaS. (From...) Figures 1-4 It can be seen that (La,Ce)₂O₂S-AlN composite inclusions exist in non-oriented silicon steel, as well as independently observed (La,Ce)₂O₂S inclusions. Among them, Figure 1 Medium-sized inclusions have a weak pinning effect on grain boundaries, while heteromorphic inclusions have a stronger pinning effect and a more significant impact. Comprehensive analysis shows that the increased rare earth content leads to a gradual transformation of rare earth inclusions from (La,Ce)AlO3 to (La,Ce)2O2S.

[0114] Figure 5 This is a solidification microstructure diagram of the non-oriented silicon steel of the present invention with different rare earth contents. Figure 5 Figure a shows the 0 wt% percentage, figure b shows the 0.0021 wt% percentage, figure c shows the 0.0034 wt% percentage, and figure d shows the 0.0058 wt% percentage. (From...) Figure 5 It can be seen that as the rare earth content increases from 0 wt% to 0.0058 wt%, the average grain size of equiaxed crystals gradually decreases. Rare earth treatment significantly refines the solidified microstructure, while rare earth treatment has little effect on the columnar crystal ratio of the solidified microstructure.

[0115] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended scope of protection is intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of this invention.

[0116] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of protection of this invention and its equivalents, this invention also intends to include these modifications and variations.

Claims

1. A rare-earth-treated non-oriented silicon steel, characterized in that, Rare earth treated non-oriented silicon steel is prepared with the following chemical composition by mass percentage: Si: 3.0%~3.5%, Al: 0.8%~1.5%, Mn: 0.3%~0.7%, C≤0.0025%, S≤0.0025%, Ti≤0.0025%, N≤0.0025%, P≤0.015%, segregating element: 0.0001%~0.006%, with the balance being Fe and unavoidable impurities, totaling 100%; wherein, the segregating element is at least one of La, Ce and Y.

2. The rare earth-treated non-oriented silicon steel according to claim 1, characterized in that, The content of segregating elements must meet the following conditions: When the segregating element is a single element: La≤0.004%, Ce≤0.004%, or Y≤0.003%; When the segregating elements are any two elements: (La+Ce)≤0.006%, (La+Y)≤0.004% and Y≤0.002%, or (Ce+Y)≤0.004% and Y≤0.002%; When the segregating elements are three elements: (La+Ce+Y)≤0.003% and Y≤0.001%.

3. A method for preparing rare earth-treated non-oriented silicon steel according to claim 1 or claim 2, characterized in that, Includes the following steps: Molten steel is smelted according to a set composition, and then subjected to RH refining. During the refining process, a polymerizing element is added to obtain RH-refined molten steel. The composition and mass percentage content of the molten steel are as follows: Si: 2.8%~3.4%, Al: 0.6%~1.4%, Mn: 0.2%~0.5%, C≤0.05%, S≤0.012%, Ti≤0.003%, N≤0.004%, P≤0.015%, with the balance being Fe and unavoidable impurities, totaling 100%. The molten steel refined by RH is continuously cast to obtain a billet; The cast billet is hot-rolled to obtain a hot-rolled plate; Rare earth treated non-oriented silicon steel is obtained by normalizing, pickling, cold rolling, and recrystallization annealing of hot-rolled plates.

4. The method for preparing rare earth-treated non-oriented silicon steel according to claim 3, characterized in that, During the RH refining process, the average thickness of the original slag layer when the ladle enters the station is ≥80mm, and the temperature is 1560℃~1590℃.

5. The method for preparing rare earth-treated non-oriented silicon steel according to claim 3, characterized in that, The specific process of RH refining includes the following steps: Decarburization and deoxidation of molten steel; oxygen content after decarburization ≤260ppm; Then, after adding desulfurizing agent to the molten steel and stirring, rare earth elements are added, and the stirring time is 6 to 8 minutes. After RH refining, the molten steel is calmed to obtain RH-refined molten steel. The calming time is 15 min to 16 min.

6. The method for preparing rare earth-treated non-oriented silicon steel according to claim 3, characterized in that, During continuous casting, the billet pulling speed is 1.0m / min to 1.1m / min, electromagnetic stirring is used during solidification, and the billet thickness is 230mm.

7. The method for preparing rare earth-treated non-oriented silicon steel according to claim 6, characterized in that, The equiaxed crystal ratio of the billet is 58%~62%, and the equiaxed crystal grain size is ≤3.5mm.

8. The method for preparing rare earth-treated non-oriented silicon steel according to claim 3, characterized in that, The specific process of hot rolling includes the following steps: The billet is heated in three stages: the first stage is heated at 1120℃~1140℃, the second stage at 1110℃~1120℃, and the third stage at 1095℃~1105℃. The total heating time is 25min~30min. The billet is subjected to four rough rolling passes, with the reduction rate of the fourth rough rolling pass being less than 25%, to obtain an intermediate billet. The intermediate billet is reheated, finished rolled, cooled and rolled to obtain a hot-rolled plate.

9. The method for preparing rare earth-treated non-oriented silicon steel according to claim 3, characterized in that, In hot-rolled steel sheets, the proportion of static recrystallization zone is ≥25%, and the normal width of banded structure is ≤2mm; the areal density of inclusions with a size of 0.2μm~1μm is ≤29000 / mm². 2 The average size is ≥0.44μm; the areal density of inclusions with a size of 1μm~5μm is ≤14000 inclusions / mm². 2 The average size is ≥2μm.

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