Non-oriented silicon steel with excellent electromagnetic and mechanical properties and method for manufacturing the same

Abstract

This invention discloses a non-oriented silicon steel with excellent electromagnetic and mechanical properties and its preparation method, relating to the field of non-oriented silicon steel technology. The chemical composition of the non-oriented silicon steel, by weight percentage, includes: C ≤ 0.003%, Si: 3.15~3.55%, Mn: 0.4~0.6%, Als: 0.5~0.85%, Sn: 0.03~0.06%, S ≤ 0.005%, N ≤ 0.005%, Ti ≤ 0.005%, with the remainder being Fe and unavoidable impurities. The non-oriented silicon steel of this invention has a tensile strength Rm of 580~615 MPa and a magnetic induction B... 50 The high-frequency iron loss P is 1.663~1.678T. 1.0 / 400 The iron loss is 16.5~17.1W / kg, and the anisotropy of the iron loss P1.0 / 400 at each angle deviating from the rolling direction is ≤1.2W / kg.

Description

Non-oriented silicon steel with excellent electromagnetic and mechanical properties and its preparation method Technical Field

[0001] This invention relates to the field of non-oriented silicon steel technology, specifically to a non-oriented silicon steel with excellent electromagnetic and mechanical properties and its preparation method. Background Technology

[0002] Non-oriented silicon steel is a key material for manufacturing motor and generator cores. In recent years, with the development of the motor industry, motors have begun to shift towards higher frequencies, smaller sizes, and higher efficiency, thus placing higher demands on the performance of non-oriented silicon steel: 1) Low iron loss at medium frequencies: Reducing iron losses (especially eddy current losses) at medium frequencies (such as 400Hz) is key to improving motor efficiency; 2) Low magnetic anisotropy: Ensuring uniform magnetic properties, small torque fluctuations, and smooth operation of the motor under different rotational directions; 3) High mechanical strength: Ultra-high strength facilitates high-speed stamping and automated production, reduces lamination burrs, and improves the rigidity of the motor core, resisting the centrifugal force of high-speed rotation.

[0003] However, there are inherent contradictions among the above properties: 1) To reduce iron loss, it is generally desirable to increase the Si content to increase resistivity and increase the grain size to reduce hysteresis loss. But this will lead to material embrittlement and a decrease in strength and stamping performance; 2) To obtain high strength, fine grain strengthening or precipitation strengthening is usually used, but this will increase the number of grain boundaries, hinder the movement of magnetic domains, and worsen iron loss, especially hysteresis loss; 3) Low anisotropy requires random distribution of grain orientation, while high strength often depends on specific processing texture.

[0004] CN115198199A discloses a method for producing high-strength non-oriented silicon steel. This method primarily achieves fine-grained strengthening by optimizing the chemical composition (e.g., controlling the Si content to 3.20-3.40%, adding Sn and Cu) and eliminating the normalizing process after hot rolling, directly performing cold rolling and annealing. The aim of this method is to prepare steel with low iron loss (P... 1.0 / 400 ≤18.0W / kg), high magnetic induction (B 50 Non-oriented silicon steel with a yield strength ≥500MPa (≥1.65T) and high strength is suitable for new energy drive motors. The core of this method is to improve performance and reduce costs through composition design and process simplification (eliminating normalization). This method requires extremely high control over composition (e.g., Cu needs to be precisely matched to the strength formula), and eliminating normalization may lead to uneven microstructure in hot-rolled plates, affecting the consistency of the finished product. Furthermore, high Si content and Cu addition can increase the difficulty of cold rolling and the risk of hot brittleness, potentially limiting the stability of industrial production.

[0005] CN116426810A proposes a method for preparing high-frequency, low-iron-loss non-oriented silicon steel to address the high-frequency requirements of drive motors in new energy vehicles. The method employs a high Si (2.8~3.2%) and high Al (1.0~1.5%) composition, and optimizes the grain size (100~150μm) through normalizing annealing and precisely controlled recrystallization annealing (e.g., heating rate 70~100℃ / s, specific partial pressure atmosphere), ultimately achieving high-frequency, low-iron-loss (P... 1.0 / 400 ≤13.2W / kg) and high magnetic induction (B 50 ≥1.71T). The annealing process conditions are extremely demanding (e.g., the partial pressure ratio needs to be strictly controlled between 0.0002 and 0.0005), making industrial implementation difficult. High Al content easily leads to AlN precipitation, which hinders grain growth, and the normalizing temperature is high (900~1200℃), significantly increasing energy consumption and costs.

[0006] Existing technologies mostly focus on optimizing a single property, making it difficult to simultaneously achieve high strength, low anisotropy, and excellent magnetic properties. Therefore, developing a manufacturing method for non-oriented silicon steel that can synergistically optimize the above-mentioned comprehensive properties is of great significance. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a non-oriented silicon steel with excellent electromagnetic and mechanical properties, the chemical composition of which, by weight percentage, includes:

[0008] C≤0.003%, Si: 3.15~3.55%, Mn: 0.4~0.6%, Als: 0.5~0.85%, Sn: 0.03~0.06%, S≤0.005%, N≤0.005%, Ti≤0.005%, with the remainder being Fe and unavoidable impurities.

[0009] The metallographic structure of this invention is a single ferrite, based on {110} <001> The microstructure is predominantly Gaussian textured, with some {100}-faceted textures. Ferrite has a body-centered cubic structure with relatively low magnetocrystalline anisotropy and magnetostriction. This means that magnetic domains move and rotate more easily within the ferrite, significantly reducing hysteresis loss, a crucial component of iron loss. The monolithic ferrite microstructure avoids the strong pinning effect of other phases (such as austenite and martensite) on domain movement. The pure, monolithic ferrite matrix provides a smooth path for the efficient passage of magnetic flux. <100> Crystal orientation is the direction of easy magnetization, when most grains are... <100> When the crystal orientation is parallel to the external magnetic field, the material achieves the highest magnetic induction. A single ferrite structure itself does not directly guarantee high magnetic induction, but through the synergistic effect of favorable texture and a pure matrix, highly concentrated grain orientations conducive to magnetization are formed on a pure, single ferrite matrix, ultimately resulting in high magnetic induction. 50This pushes the power output to an exceptional level of 1.663~1.678T.

[0010] A method for preparing non-oriented silicon steel with excellent electromagnetic and mechanical properties includes the following steps:

[0011] Smelting, continuous casting, heating, hot rolling, coiling, normalizing, pickling, cold rolling, continuous annealing and applying insulating coatings;

[0012] The heating temperature is controlled at 1050~1300℃;

[0013] The final rolling temperature of the hot rolling is controlled at 800~900℃;

[0014] The winding temperature is controlled at 500~700℃;

[0015] The normalizing temperature is controlled at 850~950℃, and the furnace tension is controlled at 1.2~2.2 N / mm. 2 ;

[0016] The pickling temperature is 75~80℃;

[0017] The cold rolling process employs a continuous rolling method to achieve the target thickness in a single pass.

[0018] The continuous annealing temperature is controlled at 900~1000℃, and the furnace tension is controlled at 0.6~1.2N / mm. 2 .

[0019] Furthermore, electromagnetic stirring is employed in the continuous casting process, ensuring that the equiaxed crystal ratio of the cast billet is ≥65%. By controlling the equiaxed crystal ratio in continuous casting, the uniformity of composition and microstructure is ensured from the source of casting. A high proportion of equiaxed crystals can reduce dendrite segregation and mitigate the tendency of banded structures during subsequent hot working, laying the foundation for ultimately obtaining uniform magnetic and mechanical properties.

[0020] A ≥65% equiaxed crystal ratio indicates that the slab's microstructure consists of countless small, randomly oriented grains. This initial uniformity and disorder in the continuous casting microstructure effectively breaks the directional inheritance of columnar crystals, resulting in very similar iron loss and magnetic induction at different angles in the final product. This is crucial for achieving iron loss P at various angles deviating from the rolling direction. 1.0 / 400 Anisotropy The primary prerequisite for this performance is ≤1.2W / kg.

[0021] The center of columnar crystal regions is often accompanied by severe elemental segregation (such as Si, Mn, Al), forming negative segregation bands. The compositional inhomogeneity of these micro-regions leads to abnormal ferrite stability and recrystallization behavior, which may form unfavorable textures or small grains after final annealing, reducing the overall magnetic induction.

[0022] The relatively uniform compositional distribution within the equiaxed crystal region reduces this harmful segregation. This facilitates the subsequent development of {110} uniformly across the entire plate surface through cold rolling and annealing. <001> The favorable texture of {100} creates conditions that contribute to achieving a stable and high level of magnetic induction.

[0023] The equiaxed grain structure makes the deformation resistance and plasticity of the cast billet more consistent in all directions. This results in more uniform hot and cold rolling deformation, reducing internal stress concentration and defects caused by uneven microstructure. The mechanical properties of the final product (such as tensile strength Rm) are more uniform and stable, with good batch consistency, which is crucial for meeting the stringent strength consistency requirements of high-efficiency motor cores.

[0024] Furthermore, the heating temperature is controlled at 1100~1250℃, and the heating and holding time is not less than 210 min. The strict heating regime ensures the full solid solution of alloying elements (especially the dissolution of MnS) and the homogenization of the billet structure, preparing for obtaining an ideal structure in hot rolling.

[0025] Furthermore, the final rolling temperature of the hot rolling is controlled at 850~870℃, and the coiling temperature is controlled at 550~650℃. Controlling the final rolling temperature at 850~870℃, which is above the complete recrystallization temperature, can obtain uniform and fine grains, which is beneficial to optimizing the hot rolling texture. Using a medium-temperature coiling at 550~650℃ aims to balance strength and electromagnetic properties. Too low a temperature is not conducive to magnetic properties, while too high a temperature will cause the precipitates to coarsen and reduce strength.

[0026] Furthermore, the normalizing temperature is controlled at 880~900℃, the normalizing time is 6~7 minutes, and the furnace tension is controlled at 1.5~2.0 N / mm. 2 Precise control of normalization temperature and tension is a crucial step in achieving microstructure refinement and homogenization. Appropriate temperature allows for complete recrystallization and refinement of the microstructure. Lower tension, ideally micro-tension or zero tension, is the most critical step in unlocking the material's magnetic potential and ensuring low anisotropy.

[0027] Furthermore, the total cold rolling reduction rate is controlled between 82% and 86%. A cold rolling reduction rate as high as 82% to 86% introduces significant deformation energy and a large number of uniformly distributed shear bands into the steel sheet. These shear bands will become the core dominant sites for recrystallization during subsequent annealing, significantly improving the nucleation rate and being key to obtaining fine, uniform equiaxed crystals. A cold rolling reduction rate as high as 82% to 86% is conducive to the development of favorable Gaussian texture during annealing {110} <001> To enhance magnetic induction B 50 It is of utmost importance.

[0028] Furthermore, the continuous annealing rate is controlled at 130~140 m / min, the heating section temperature is controlled at 930~970℃, the furnace tension is controlled at 0.8~1.0 N / mm², the furnace hydrogen gas fraction is controlled at 25~35%, and the furnace dew point is controlled at ≤-20℃. Low-tension annealing is the core process for achieving low magnetic anisotropy. Low tension provides a "relaxed" environment for the growth of recrystallized grains, reduces the constraint of mechanical stress on grain boundary migration, and allows grains with different orientations to grow more freely, thereby promoting the formation of random texture and significantly reducing the anisotropy of iron loss. Specific atmosphere control provides a reducing atmosphere to ensure a smooth steel plate surface; on the other hand, controlling the furnace dew point at ≤-20℃ avoids internal oxidation, ensures clean grain boundaries, and is conducive to grain growth and improved magnetic properties.

[0029] Furthermore, forced cooling is employed after normalizing, with a cooling rate of no less than 20℃ / s. During the high-temperature slow cooling process after normalizing, elements such as carbon and nitrogen dissolved in ferrite have sufficient time to precipitate at grain boundaries or within grains, forming coarse carbonitrides (such as AlN and TiC). These precipitates can become crack initiation sites during subsequent cold rolling, damaging the sheet shape. During final annealing, they can strongly pin grain boundaries and magnetic domain walls, severely deteriorating magnetic properties. Forced cooling (≥20℃ / s) allows the billet to quickly pass through the temperature range where carbonitrides are most likely to precipitate (approximately 500℃~700℃), freezing the solid solution elements and preventing them from precipitating. This significantly reduces the amount of brittle second phase, maintains the purity of the matrix, and lays the foundation for obtaining high magnetic induction. In addition, rapid cooling inhibits ferrite grain growth, fixing the fine-grained structure obtained from normalizing. This provides a fine and uniform initial structure for subsequent cold rolling processes. This uniform microstructure ensures that deformation energy is transmitted more evenly during high-pressure cold rolling, which is more conducive to the formation of a large number of uniform shear bands, which develop during annealing {110}. <001> The core nucleation site of Gaussian texture.

[0030] Furthermore, the temperature is controlled between 440-570℃ during the application of the insulating coating. This is to ensure that the insulating coating can form and adhere well to the steel plate surface, while avoiding excessively high temperatures from adversely affecting the optimized ferrite recrystallization structure (such as recovery, recrystallization, or undesirable precipitation), thus ensuring the stability of product performance.

[0031] Through innovative compositional design, the recrystallization texture is controlled by the segregation effect of Sn, improving the electromagnetic properties of the finished product. The mechanical properties are enhanced by the solid solution effects of elements such as Si, Mn, and Als. Optimization of the cold rolling process retains sufficient cold-rolled shear bands in the matrix, providing more recrystallization nucleation sites and optimizing the texture. Simultaneously, higher deformation energy storage provides a stronger driving force for subsequent recrystallization, promoting the nucleation and growth of randomly oriented grains. Innovative normalizing and continuous annealing processes employ low tension and high heating rates to increase the recrystallization nucleation driving force and nucleation rate, resulting in a more homogenized microstructure.

[0032] The beneficial effects of this invention are as follows:

[0033] 1. The tensile strength Rm of the non-oriented silicon steel of the present invention is 580~615MPa, and the magnetic induction B is... 50 The high-frequency iron loss P is 1.663~1.678T. 1.0 / 400 Iron loss P1.0 / 400 at various angles deviating from the rolling direction is 16.5~17.1 W / kg, with anisotropy. ≤1.2W / kg.

[0034] 2. By employing a composite solid solution strengthening scheme with high Si (3.15~3.55%), Mn (0.4~0.6%), and Als (0.5~0.85%), combined with optimized hot rolling, cold rolling, and annealing processes, the finished product achieved high tensile strength. As shown in the examples, its tensile strength (Rm) stably reached 580-615MPa, far exceeding the 453MPa of the comparative example, fully meeting the strength requirements of high-efficiency motor cores against centrifugal force and high-speed stamping.

[0035] 3. By adding Sn (0.03~0.06%), its property of segregating at grain boundaries is utilized to effectively suppress unfavorable textures and promote the development of favorable textures such as {100} and {110}, thereby reducing the magnetic induction (B) 50 The high magnetic flux density (PT) is increased to over 1.663T (up to 1.678T). High magnetic flux density helps reduce the risk of magnetic circuit saturation in the motor, reduces excitation requirements, and improves efficiency. The high Si and high Al design significantly improves the resistivity of the material, effectively reducing eddy current losses. Simultaneously, by controlling the process to obtain a uniform and clean ferrite structure, the resistance to domain wall movement is reduced, thus lowering hysteresis losses. Ultimately, this leads to a significant reduction in high-frequency iron losses (PT). 1.0 / 400 The concentration should be controlled at an excellent level of 16.5~17.1 W / kg.

[0036] 4. Unlike some existing technologies that eliminate normalizing to reduce costs, this invention retains and optimizes the normalizing process, ensuring the uniformity of the hot-rolled plate microstructure and laying the foundation for subsequent cold rolling and achieving consistent performance. More importantly, it innovatively employs low-tension annealing in the continuous annealing stage, which provides a free growth environment for recrystallized grains and greatly promotes the formation of random orientation texture. Attached Figure Description

[0037] Figure 1 is a metallographic photograph of the non-oriented silicon steel prepared in Example 1. Detailed Implementation

[0038] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0039] Traditional processes for improving the electromagnetic and mechanical properties of non-oriented silicon steel typically involve adding alloying elements such as Si, Mn, and Al. However, higher alloy content leads to poorer cold working properties, increased rates of edge cracking and strip breakage during cold rolling, and reduced production efficiency. Furthermore, while reducing grain size can improve mechanical properties, it also deteriorates electromagnetic properties. Simultaneously, as rotating equipment, motors require high levels of material anisotropy. Therefore, achieving excellent electromagnetic properties, superior mechanical properties, and low magnetic anisotropy through economical and convenient methods has long been a challenge in the industry.

[0040] To address the aforementioned problems, this invention proposes a non-oriented silicon steel with excellent electromagnetic and mechanical properties, and its preparation method. The chemical composition of the non-oriented silicon steel of this invention, by weight percentage, includes: C≤0.003%, Si: 3.15~3.55%, Mn: 0.4~0.6%, Als: 0.5~0.85%, Sn: 0.03~0.06%, S≤0.005%, N≤0.005%, Ti≤0.005%, with the remainder being Fe and unavoidable impurities.

[0041] The roles of each element in steel are as follows:

[0042] C: Although C can improve mechanical properties, it is a harmful element for non-oriented silicon steel, which will deteriorate the magnetic properties of silicon steel. Preferably, the present invention requires that the C content be controlled below 0.003%.

[0043] Si: Si can reduce iron loss, and its solid solution strengthening effect can improve mechanical strength. Furthermore, increasing Si content is beneficial for improving electromagnetic properties. Therefore, the Si content in this invention is controlled at 3.15%~3.55%. The combination of high Si content (3.15~3.55%) and high Al content (0.5~0.85%) significantly increases the stacking fault energy of the steel. This makes the material more prone to cross-slip during cold rolling, thereby promoting the formation of shear bands. Shear bands are crucial for subsequent annealing. <001> The preferred nucleation sites of Gaussian grains.

[0044] Mn: Mn plays a solid solution strengthening role in non-oriented silicon steel, which can improve the product strength and reduce the product iron loss. Mn and S form MnS, which reduces the S dissolved in the slab during heating and can effectively suppress hot brittleness during heating. However, if the Mn content is too high, fine MnS precipitates will be generated during hot rolling, which will prevent grain growth and deteriorate the magnetic properties. Therefore, the Mn content in this invention is controlled at 0.40%~0.60%.

[0045] Als: Al is similar to Si in that it can improve the magnetic properties and mechanical strength of the product. However, Al has a smaller impact on the brittleness of electrical steel than Si. Considering the magnetic performance requirements of the product, the Al content in this invention should be controlled at 0.5% to 0.85%.

[0046] Sn: Tin has a strong tendency to segregate at grain boundaries, adsorbing onto them, especially high-energy, high-migration-rate grain boundaries. This selectively inhibits the growth of {111} textured (unfavorable texture) grains, thus clearing the way for the growth of {110} and {100} textured grains, increasing the composition of {100} and {110} textures, thereby improving magnetic flux density. High magnetic flux density reduces the risk of magnetic circuit saturation, decreases excitation requirements, and indirectly reduces copper losses. Especially at high speeds and high loads, it ensures the flux transmission efficiency of the rotor magnetic circuit. However, Sn is expensive, and excessive addition will increase costs. Therefore, in this invention, Sn is controlled at 0.03~0.06%.

[0047] S, N, Ti: S, N, and Ti are harmful elements. To minimize their impact on the magnetic properties of the product, the content of S is ≤0.005%, the content of N is ≤0.005%, and the content of Ti is ≤0.005%. The extremely low content of C, N, S, and Ti ensures the single ferrite characteristics of the microstructure, avoids pinning of grain boundaries due to second-phase migration, and provides conditions for free and rapid grain growth during annealing, allowing grains with advantageous textures to grow fully.

[0048] The steel with the above chemical composition is pretreated with molten iron, refined in a converter, and vacuum treated before being continuously cast into slabs with a thickness of 220~250mm. Electromagnetic stirring is used in the continuous casting process to ensure that the equiaxed crystal ratio of the slab is ≥65%. The temperature of the heating furnace is controlled at 1100~1250℃ and the heating and holding time is not less than 210min.

[0049] The hot-rolled plate is rolled to a thickness of 2.2~2.5mm after 7 passes of hot rolling. Considering that the present invention has a normalizing process, the final rolling temperature is high-temperature final rolling. A high final rolling temperature can optimize the texture and improve the magnetic induction. Therefore, the final rolling temperature is controlled at 850~870℃.

[0050] Medium-temperature winding is employed. Lower winding temperatures can improve the mechanical strength of the product, but are detrimental to its electromagnetic properties. Excessively high winding temperatures, on the one hand, reduce mechanical properties, and on the other hand, promote the precipitation of carbides and nitrides, which are detrimental to electromagnetic properties. Therefore, this invention requires the hot-rolled winding temperature to be controlled between 550 and 650°C, followed by natural cooling to room temperature after winding. To ensure that the temperature drops to the target temperature before winding, laminar flow cooling is used before winding, and a post-cooling method is employed.

[0051] For the normalizing pickling line, the temperature is controlled at 880~900℃, the normalizing time is 6~7 minutes, and the tension inside the furnace is controlled at 1.5~2.0 N / mm. 2 Pickling temperature: 75~80℃; Normalizing temperature: 880~900℃ and 1.5~2.0 N / mm. 2 The micro-tension eliminates the undesirable texture inheritance that hot rolling may bring, and forms a more uniform, equiaxed initial microstructure through recrystallization. The use of micro-tension is crucial, as it ensures the equiaxing of grains, lays the foundation for the uniformity of subsequent cold rolling deformation, and is a prerequisite for obtaining a uniform texture.

[0052] The above-mentioned normalized pickled plate is rolled to the target thickness of 0.35mm in 5 to 6 passes using a single cold rolling method, with a total cold rolling reduction rate of 82% to 86%.

[0053] The cold-rolled sheet was annealed in a continuous annealing furnace. The process speed was controlled at 130~140m / min, the heating temperature was controlled at 930~970℃, and the furnace tension was 0.8~1.0N / mm. 2 The hydrogen gas fraction in the furnace is controlled at 25-35%; the dew point in the furnace is ≤-20℃; after annealing, the insulating coating is applied by a coating roller and cured at 440-570℃.

[0054] The non-oriented silicon steel product obtained by the above-mentioned process has an Rm of 580~615 MPa and a B... 50 1.663~1.678T, P 1.0 / 400 Iron loss P of finished product deviating from the rolling direction at various angles: 16.5~17.1 W / kg1.0 / 400 Anisotropy ≤1.2W / kg, of which, , Iron loss P in 10 directions of deviation from the rolling direction: 0°, 10°, 20°...90° 1.0 / 400 The average value, P i The iron loss P corresponding to direction i among the 10 directions 1.0 / 400 value.

[0055] This invention successfully prepared high-performance electrical steel through synergistic innovation in composition, process, and heat treatment. In terms of composition, the grain boundary segregation of Sn, combined with high Si and Al content, increases stacking fault energy and suppresses unfavorable {111} texture. In terms of process, high-pressure cold rolling introduces numerous shear bands as nucleation points, and combined with a high-heat-rate, low-tension annealing process, it provides a strong recrystallization driving force. The final product is a {110} texture. <001> A ferrite material with a predominantly Gaussian texture and a coarse, uniform structure was used to achieve ultra-high magnetic induction (B0). 50 :1.663~1.678T) and low iron loss (P 1.0 / 400 :16.5~17.1W / kg) and low anisotropy ( An excellent combination of ≤1.2W / kg.

[0056] The present invention will be further illustrated by the following embodiments and comparative examples.

[0057] Example 1

[0058] The chemical composition of the slab, by weight percentage, includes: C: 0.0025%, Si: 3.35%, Mn: 0.5%, Als: 0.70%, Sn: 0.05%, S: 0.004%, N: 0.002%, Ti: 0.002%, with the remainder being Fe and unavoidable impurities;

[0059] The steel with the above chemical composition is pretreated with molten iron, smelted in a converter, and vacuum treated before being continuously cast into a slab with a thickness of 230 mm. Electromagnetic stirring is used in the continuous casting process. The equiaxed crystal ratio of the slab is 66%. The temperature of the heating furnace is controlled at 1130℃ and the heating and holding time is 210 min.

[0060] The hot-rolled plate is rolled to a thickness of 2.3 mm in 7 passes, with the final rolling temperature controlled at 860℃.

[0061] The hot-rolled coiling temperature is controlled at 630℃, and the coil is allowed to cool naturally to room temperature after coiling. To ensure that the temperature before coiling is lower than the target temperature, laminar flow cooling is used before coiling, and a post-cooling method is employed.

[0062] The normalizing pickling line operates at a temperature controlled at 880℃, a normalizing time of 6 minutes, and a furnace tension controlled at 1.5 N / mm.2 Cooling is carried out between normalizing and pickling, with a cooling rate ≥20℃ / s and a pickling temperature of 75~80℃;

[0063] The above-mentioned normalized pickled plates are rolled to the target thickness of 0.35 mm in 5 to 6 passes using a single cold rolling method, with a total cold rolling reduction rate of 84.78%.

[0064] The cold-rolled sheet was annealed in a continuous annealing furnace with the process speed controlled at 130 m / min, the heating temperature controlled at 970℃, and the furnace tension at 0.9 N / mm. 2 The hydrogen gas fraction in the furnace is controlled at 25-35%; the dew point in the furnace is -23℃; after annealing, the insulating coating is applied by a coating roller and cured at 440-570℃.

[0065] The non-oriented silicon steel product obtained by the process in Example 1 has an Rm of 590 MPa and a B... 50 1.663T, P 1.0 / 400 16.7W / kg, iron loss P of finished product deviating from the rolling direction at various angles 1.0 / 400 Anisotropy =1.11W / kg.

[0066] Example 2

[0067] The chemical composition of the slab, by weight percentage, includes: C: 0.002%, Si: 3.45%, Mn: 0.45%, Als: 0.68%, Sn: 0.03%, S: 0.003%, N: 0.002%, Ti: 0.002%, with the remainder being Fe and unavoidable impurities;

[0068] The steel with the above chemical composition is pretreated with molten iron, smelted in a converter, and vacuum treated before being continuously cast into a slab with a thickness of 230 mm. Electromagnetic stirring is used in the continuous casting process. The equiaxed crystal ratio of the slab is 67%. The temperature of the heating furnace is controlled at 1135℃ and the heating and holding time is 225 min.

[0069] The hot-rolled plate is rolled to a thickness of 2.40 mm in 7 passes, with the final rolling temperature controlled at 870℃.

[0070] The hot-rolled coiling temperature is controlled at 650℃, and the coil is allowed to cool naturally to room temperature after coiling. To ensure that the temperature before coiling is lower than the target temperature, laminar flow cooling is used before coiling, and a post-cooling method is employed.

[0071] The normalizing pickling line maintains a temperature of 885℃, a normalizing time of 7 minutes, and a furnace tension of 2.0 N / mm. 2 Cooling is carried out between normalizing and pickling, with a cooling rate ≥20℃ / s and a pickling temperature of 75~80℃;

[0072] The above-mentioned normalized pickled plates are rolled to the target thickness of 0.35 mm in 5 to 6 passes using a single cold rolling method, with a total cold rolling reduction rate of 85.42%.

[0073] The cold-rolled sheet was annealed in a continuous annealing furnace with the process speed controlled at 135 m / min, the heating temperature controlled at 970℃, and the furnace tension at 0.8 N / mm. 2 The hydrogen gas fraction in the furnace is controlled at 25-35%; the dew point in the furnace is -22℃; after annealing, the insulating coating is applied by a coating roller and cured at 440-570℃.

[0074] The non-oriented silicon steel product obtained by the process in Example 2 has an Rm of 610 MPa and a B... 50 1.678T, P 1.0 / 400 17.1 W / kg, iron loss P of finished product deviating from the rolling direction at various angles 1.0 / 400 Anisotropy =1.03W / kg.

[0075] Example 3

[0076] The chemical composition of the slab, by weight percentage, includes: C: 0.002%, Si: 3.45%, Mn: 0.45%, Als: 0.68%, Sn: 0.03%, S: 0.003%, N: 0.002%, Ti: 0.002%, with the remainder being Fe and unavoidable impurities;

[0077] The steel with the above chemical composition is pretreated with molten iron, smelted in a converter, and vacuum treated before being continuously cast into a slab with a thickness of 230 mm. Electromagnetic stirring is used in the continuous casting process. The equiaxed crystal ratio of the slab is 67%. The temperature of the heating furnace is controlled at 1135℃ and the heating and holding time is 225 min.

[0078] The hot-rolled plate is rolled to a thickness of 2.40 mm in 7 passes, with the final rolling temperature controlled at 870℃.

[0079] The hot-rolled coiling temperature is controlled at 650℃, and the coil is allowed to cool naturally to room temperature after coiling. To ensure that the temperature before coiling is lower than the target temperature, laminar flow cooling is used before coiling, and a post-cooling method is employed.

[0080] The normalizing pickling line maintains a temperature of 885℃, a normalizing time of 7 minutes, and a furnace tension of 1.53 N / mm. 2 Cooling is carried out between normalizing and pickling, with a cooling rate ≥20℃ / s and a pickling temperature of 75~80℃;

[0081] The above-mentioned normalized pickled plates are rolled to the target thickness of 0.35 mm in 5 to 6 passes using a single cold rolling method, with a total cold rolling reduction rate of 85.42%.

[0082] The cold-rolled sheet was annealed in a continuous annealing furnace with the process speed controlled at 138 m / min, the heating temperature controlled at 965℃, and the furnace tension at 0.85 N / mm. 2 The hydrogen gas fraction in the furnace is controlled at 25-35%; the dew point in the furnace is -23℃; after annealing, the insulating coating is applied by a coating roller and cured at 440-570℃.

[0083] The non-oriented silicon steel product obtained by the process in Example 3 has an Rm of 615 MPa and a B... 50 1.675T, P 1.0 / 400 16.9 W / kg, iron loss P of finished product deviating from the rolling direction at various angles 1.0 / 400 Anisotropy =1.09W / kg.

[0084] Comparative Example

[0085] The chemical composition of the slab, by weight percentage, includes: C: 0.003%, Si: 2.95%, Mn: 0.20%, Als: 0.85%, S: 0.003%, N: 0.002%, Ti: 0.002%, with the remainder being Fe and unavoidable impurities;

[0086] The steel with the above chemical composition is pretreated with molten iron, smelted in a converter, and vacuum treated before being continuously cast into a slab with a thickness of 230 mm. Electromagnetic stirring is used in the continuous casting process. The equiaxed crystal ratio of the slab is 60%. The temperature of the heating furnace is controlled at 1135℃ and the heating and holding time is 225 min.

[0087] The hot-rolled plate is rolled to a thickness of 1.8 mm in 7 passes, with the final rolling temperature controlled at 840℃.

[0088] The hot-rolled coiling temperature is controlled at 650℃, and the coil is allowed to cool naturally to room temperature after coiling. To ensure that the temperature before coiling is lower than the target temperature, laminar flow cooling is used before coiling, and a post-cooling method is employed.

[0089] The normalizing pickling line maintains a temperature of 885℃, a normalizing time of 7 minutes, and a furnace tension of 2.5 N / mm. 2 Pickling temperature: 75~80℃;

[0090] The above-mentioned normalized pickled plates are rolled to the target thickness of 0.35 mm in 5 to 6 passes using a single cold rolling method, with a total cold rolling reduction rate of 80.55%.

[0091] The cold-rolled sheet was annealed in a continuous annealing furnace with the process speed controlled at 120 m / min, the heating temperature controlled at 980℃, and the furnace tension at 2.5 N / mm. 2The hydrogen gas fraction in the furnace is controlled at 25-35%; the dew point in the furnace is -13℃; after annealing, the insulating coating is applied by a coating roller and cured at 440-570℃.

[0092] The non-oriented silicon steel product obtained through the comparative process has an Rm of 453 MPa and a B... 50 1.672T, P 1.0 / 400 21.03 W / kg, iron loss P of finished product deviating from the rolling direction at various angles 1.0 / 400 Anisotropy =1.43W / kg.

[0093] Performance Description

[0094] Referring to Figure 1, a metallographic photograph of the non-oriented silicon steel prepared in Example 1 shows a typical ferrite matrix. This is due to the high Si (3.15~3.55%) and high Al (0.5~0.85%) chemical composition design of this invention, which are strong ferrite stabilizing elements, ensuring that the steel does not undergo phase transformation during cooling from the annealing temperature to room temperature, maintaining a single-phase ferrite structure throughout. The grains exhibit an equiaxed shape. This indicates that a sufficient recrystallization process occurred after cold rolling and continuous annealing. New, undistorted grains nucleate and grow from the cold-rolled deformed structure, forming equiaxed grains with similar anisotropic dimensions. As can be seen from Figure 1, the grain size distribution is relatively uniform. A uniform structure is key to obtaining low magnetic anisotropy. The grain size is moderate, neither abnormally large nor extremely small, reflecting the good balance achieved by this invention between magnetic properties (preferring large grains to reduce iron loss) and mechanical properties (preferring small grains to increase strength). This control is achieved through precise annealing temperature (930~970℃), time (determined by line speed of 130~140m / min), and crucially, low tension (0.8~1.0N / mm). 2 This is achieved through an annealing process.

[0095] The tensile strength Rm of all three embodiments was significantly higher than that of the comparative example (580-615 MPa vs 453 MPa). This is because the embodiments adopted the core compositional design of this invention, and the higher Si, Mn, and Al content produced a significant solid solution strengthening effect. In contrast, the comparative example had a lower Si content (2.95%) and an extremely low Mn content (0.20%), resulting in a weaker solid solution strengthening effect. The embodiments, through optimized processes (such as a higher cold rolling reduction rate of 82%~86% vs. 80.55% in the comparative example) and controlled annealing, achieved a finer grain structure with a better balance between strength and toughness. The grain structure of the comparative example may not be ideal due to process mismatch.

[0096] For magnetic induction (B) 50The magnetic induction of Examples 2 and 3 was superior to that of the comparative example. This is mainly attributed to the addition of Sn element in Examples 2 and 3 (while no Sn was added in the comparative example). Sn, through the segregation of grain boundaries, suppressed the development of unfavorable textures and promoted the formation of favorable magnetization orientation textures such as {100} and {110}.

[0097] For iron loss (P) 1.0 / 400 The iron losses in the three embodiments were significantly lower than those in the comparative example. This is because the high Si and high Al content in the embodiments effectively increased the resistivity of the steel, significantly reducing eddy current losses, which are the main component of iron losses. Furthermore, the embodiments strictly limited the content of harmful elements such as C, S, N, and Ti, reducing pinning points for domain wall movement and lowering hysteresis losses. Simultaneously, the uniform equiaxed ferrite grains (as shown in Figure 1) provided a smooth path for domain movement.

[0098] Iron loss anisotropy in the embodiment All values ​​are ≤1.2 W / kg, significantly better than the comparative example's 1.43 W / kg. This indicates that the material of this invention exhibits more uniform magnetic properties in different directions. The low anisotropy directly stems from the randomized recrystallization texture. This invention introduces a large number of uniformly distributed nucleation points (shear bands) through high-pressure cold rolling, combined with low-tension control during continuous annealing, providing a relatively free growth environment for grains of various orientations, avoiding excessive growth of a specific orientation (such as {111}), thereby achieving optimized texture and uniform magnetic properties.

[0099] This invention successfully overcomes the traditional contradiction of the inverse relationship between the magnetic and mechanical properties of non-oriented silicon steel through a three-pronged approach of component design, process innovation, and microstructure control. The metallographic structure shown in Figure 1 is a microscopic manifestation of the success of this approach. The data from the examples fully demonstrate that this invention maintains high magnetic induction (B... 50 ≥1.663T) and extremely low anisotropy ( While achieving a strength of ≤1.2W / kg, it also achieves high strength (Rm≥580MPa), with comprehensive performance significantly superior to that of traditional compositions and processes, meeting the stringent requirements of high-efficiency motors for the comprehensive performance of materials.

[0100] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its protection scope. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the invention, but these changes, modifications or equivalent substitutions are all within the protection scope of the pending claims of the invention.

Claims

1. A non-oriented silicon steel with excellent electromagnetic and mechanical properties, characterized in that, The chemical composition, by weight percentage, includes: Si: 3.15~3.55%, Mn: 0.4~0.6%, Als: 0.5~0.85%, Sn: 0.03~0.06%, C≤0.003%, S≤0.005%, N≤0.005%, Ti≤0.005%, with the remainder being Fe and unavoidable impurities. The preparation method sequentially includes the following steps: smelting, continuous casting, heating, hot rolling, coiling, normalizing, pickling, cold rolling, continuous annealing, and applying an insulating coating. The heating temperature is controlled at 1050~1300℃; the final rolling temperature of the hot rolling is controlled at 800~900℃; the coiling temperature is controlled at 500~700℃; the normalizing temperature is controlled at 850~950℃; and the furnace tension is controlled at 1.5~2.0 N / mm. 2 The normalizing time is 6-7 minutes, and the cooling rate from the normalizing temperature to the pickling temperature is ≥20℃ / s; the pickling temperature is 70-85℃; the cold rolling is carried out in a continuous rolling process to the target thickness in one pass, and the total cold rolling reduction rate is controlled between 82% and 86%; the continuous annealing temperature is controlled between 900-1000℃, and the furnace tension is controlled between 0.8-1.0 N / mm. 2 The hydrogen gas fraction in the furnace is controlled at 25-35%, and the dew point in the furnace is ≤-20℃; the equiaxed crystal ratio of the billet during continuous casting is ≥65%.

2. The non-oriented silicon steel with excellent electromagnetic and mechanical properties according to claim 1, characterized in that, The metallographic structure of the non-oriented silicon steel is {110}. <001> Ferrite structures with Gaussian texture and ferrite structures with {100} plane texture.

3. A method for preparing non-oriented silicon steel with excellent electromagnetic and mechanical properties as described in claim 1 or 2, characterized in that, The steps are as follows: The process includes smelting, continuous casting, heating, hot rolling, coiling, normalizing, pickling, cold rolling, continuous annealing, and applying an insulating coating; wherein the heating temperature is controlled at 1050~1300℃; the final rolling temperature of the hot rolling is controlled at 800~900℃; the coiling temperature is controlled at 500~700℃; the normalizing temperature is controlled at 850~950℃, and the furnace tension is controlled at 1.5~2.0 N / mm. 2 The normalizing time is 6-7 minutes, and the cooling rate from the normalizing temperature to the pickling temperature is ≥20℃ / s; the pickling temperature is 70-85℃; the cold rolling is carried out in a continuous rolling process to the target thickness in one pass, and the total cold rolling reduction rate is controlled between 82% and 86%; the continuous annealing temperature is controlled between 900-1000℃, and the furnace tension is controlled between 0.8-1.0 N / mm. 2 The hydrogen gas fraction in the furnace is controlled at 25-35%, and the dew point in the furnace is ≤-20℃; the equiaxed crystal ratio of the billet during continuous casting is ≥65%.

4. The method for preparing non-oriented silicon steel with excellent electromagnetic and mechanical properties according to claim 3, characterized in that: The heating temperature is controlled at 1100~1250℃, and the heating and holding time is not less than 210min.

5. The method for preparing non-oriented silicon steel with excellent electromagnetic and mechanical properties according to claim 3, characterized in that: The final rolling temperature of the hot rolling is controlled at 850~870℃, and the coiling temperature is controlled at 550~650℃.

6. The method for preparing non-oriented silicon steel with excellent electromagnetic and mechanical properties according to claim 3, characterized in that: The normalization temperature is controlled at 880~900℃.

7. The method for preparing non-oriented silicon steel with excellent electromagnetic and mechanical properties according to claim 3, characterized in that, The pickling temperature is 75~80℃.

8. The method for preparing non-oriented silicon steel with excellent electromagnetic and mechanical properties according to claim 3, characterized in that: The continuous annealing speed is controlled at 130~140m / min, and the heating section temperature is controlled at 930~970℃.

9. A motor core, characterized in that, It is made from non-oriented silicon steel as described in claim 1 or 2.

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