A non-aluminum, non-oriented silicon steel and its preparation method

Abstract

This invention relates to an aluminum-free, non-oriented silicon steel and its preparation method, belonging to the field of metallurgical technology. Through C-Si-Ln system composition design, this invention achieves stable production of aluminum-free, non-oriented silicon steel with excellent surface quality and magnetic properties without adding Al and by reducing Si content, using an acid continuous rolling process combined with precise dimensional control throughout the entire process. This meets the requirements for upgrading motor energy efficiency and high-efficiency processing. Simultaneously, it enables high-speed production of lanthanide rare earth aluminum-free, non-oriented silicon steel without normalizing acid continuous rolling, achieving the technical effects of cost reduction, efficiency improvement, energy saving, and consumption reduction.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, and particularly relates to an aluminum-free, non-oriented silicon steel and its preparation method. Background Technology

[0002] Non-oriented silicon steel is a key soft magnetic functional material in the power, electronics, and motor manufacturing industries. Its silicon content typically ranges from 0.5% to 3.0%. Products with a silicon content exceeding 1.7% are generally classified as medium- to high-grade non-oriented silicon steel. It is widely used in core equipment such as high-efficiency motors, generators, and transformers. Its magnetic properties, surface quality, and processing performance directly determine the motor's energy efficiency rating and manufacturing efficiency. Current industrial production commonly employs the traditional C-Si-Al composition system, using Si and Al to increase resistivity and reduce eddy current losses, while using Al as the main deoxidizing and purification element to control inclusions in the steel. This is the mainstream technical approach in the industry.

[0003] Due to the significantly increased hardness and brittleness caused by high silicon and high aluminum content, conventional high-grade non-oriented silicon steels often exhibit deformed fibrous ferrite microstructure after hot rolling, making them unsuitable for direct cold rolling. A normalizing treatment process is necessary before cold rolling to achieve recrystallization. Cold rolling typically employs single-stand reversible rolling, resulting in a lengthy process, low production efficiency, and high equipment investment and manufacturing costs, contradicting the industry's trend towards green, low-carbon, and energy-saving development. For example, patent CN106702260A discloses a high-magnetic-induction, low-iron-loss non-oriented silicon steel and its production method, achieving low iron loss and high magnetic induction by controlling C, Si, and Al components. However, the process requires normalizing and pickling, leading to a long process, low efficiency, and high cost. Patent CN111471927A discloses a high-magnetic-induction non-oriented silicon steel for automotive generators and its preparation method, employing a low-silicon, high-manganese composition design to eliminate the need for normalizing. However, it lacks rare earth elements for steel purification and inclusion modification treatment, resulting in high iron loss and poor processing performance, making it difficult to meet the energy efficiency upgrade requirements of motors. Patent CN114737129A discloses a high-performance non-oriented silicon steel for wound motor cores and its production method. By adjusting Si / Al and adding a single rare earth Ce to improve toughness and magnetic properties, normalization treatment is still required. Furthermore, aluminum-containing systems are prone to alumina slag spots. The effect of a single rare earth on the modification of inclusions is limited, thus limiting the improvement of magnetic properties.

[0004] Meanwhile, the C-Si-Al composition system has inherent defects: increased Si and Al content significantly increases material hardness and brittleness, reduces toughness and processing performance, making it difficult to adapt to high-speed and high-efficiency processing technologies such as progressive dies and roll-up, thus restricting the improvement of high-end motor manufacturing efficiency; when Al is used as the main deoxidation and purification element, it easily generates fine alumina inclusions and accumulates on the strip surface to form alumina slag spots, deteriorating surface quality, while also hindering annealed grain growth and magnetic domain movement, leading to increased iron loss, reduced magnetic induction, and poor magnetic performance stability. Existing rare earth silicon steel technologies mostly use single rare earth elements, which have limited effect on controlling the spheroidization, coarsening, and uniform distribution of inclusions in steel, making it difficult to fully utilize the role of rare earth in purifying steel and optimizing magnetic properties, and the presence of aluminum always poses a risk of surface defects, failing to fundamentally solve the surface quality problem; in addition, high silicon and high aluminum content leads to poor material plasticity, making it difficult to adapt to efficient continuous acid rolling processes, and failing to achieve short-process, high-speed, low-cost, and stable production, which is incompatible with the steel industry's development needs for green environmental protection, energy conservation, and cost reduction.

[0005] In summary, against the backdrop of continuous upgrades in the energy efficiency of high-efficiency motors and the low-carbon transformation of the steel industry, existing technologies for medium- and high-grade non-oriented silicon steel are insufficient to simultaneously meet the comprehensive requirements of excellent magnetic properties, superior surface quality, good processing performance, short process, and low energy consumption. There is an urgent need to develop new aluminum-free composition systems and supporting short-process preparation processes to achieve deep purification of steel, improved surface quality, and synergistic optimization of magnetic properties and processing performance, in line with the industry's trend towards high-end and green development. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides an aluminum-free, non-oriented silicon steel and its preparation method. Through C-Si-Ln system composition design, without adding Al elements and reducing Si content, an acid continuous rolling process is adopted, along with precise dimensional control throughout the entire process. This allows for the stable preparation of aluminum-free, non-oriented silicon steel with excellent surface quality and magnetic properties, meeting the requirements for motor energy efficiency upgrades and high-efficiency processing. Simultaneously, it enables high-speed production of lanthanide rare earth aluminum-free, non-oriented silicon steel without normalizing acid continuous rolling, achieving the technical effects of cost reduction, efficiency improvement, energy saving, and consumption reduction.

[0007] The first objective of this invention is to provide an aluminum-free, non-oriented silicon steel, wherein the elemental composition and mass percentage of the aluminum-free, non-oriented silicon steel are as follows: C≤0.0020%, Si 1.00%-1.50%, Mn 0.30%-0.45%, P 0.010%-0.020%, S≤0.0020%, Ln 0.003%-0.005%, O≤0.0020%, N≤0.0025%, with the balance being Fe and other unavoidable impurities;

[0008] Ln is composed of La, Pr and Nd in a mass ratio of (5-6):(2-3):1;

[0009] Rare Earth Index I Ln =3.275-[1-(Ln)] 1.315 / [7.8(O)+3.46(S)] 0.137 =1.15-1.35; when Ln adopts a specific lanthanide rare earth ratio and rare earth index I Ln At the same time, it can effectively ensure the purification of steel and control the morphology of inclusions, and with I Ln The effect of lanthanide rare earth elements in purifying steel and reducing and coarsening inclusions is continuously enhanced, enabling the production of non-oriented silicon steel with excellent magnetic properties, while significantly improving the material's efficient processing performance.

[0010] In one embodiment of the present invention, C is a harmful element in non-oriented silicon steel. Its content is high and can easily cause magnetic aging, which will also lead to increased iron loss and decreased magnetic induction. Therefore, the mass percentage of C is controlled to C≤0.0020% to ensure the stability of the magnetic properties of silicon steel.

[0011] In one embodiment of the present invention, Si is the core alloying element of non-oriented silicon steel, which can significantly improve the resistivity of steel and reduce eddy current loss. However, excessive Si content will increase the hardness and brittleness of the material and degrade the processing performance. In order to balance the magnetic properties, stable rolling and efficient processing requirements, the Si mass percentage is controlled at 1.00%-1.50%.

[0012] In one embodiment of the present invention, Mn can increase the resistivity of steel, help reduce iron loss, and preferentially form high-melting-point MnS with S in steel, avoiding the precipitation of low-melting-point FeS along grain boundaries that would cause hot brittleness in hot-rolled plates. This can improve the hot-rolled plasticity, hot-rolled microstructure, and processing performance of silicon steel. However, excessively high Mn content will significantly reduce the phase transformation temperature, resulting in lower normalizing and final annealing temperatures and deteriorating magnetic properties, while also increasing production costs. Therefore, the mass percentage of Mn is controlled at 0.30%-0.45%, so that non-oriented silicon steel has both excellent magnetic properties and high-efficiency processing performance.

[0013] In one embodiment of the present invention, P can increase the resistivity of steel, which helps to reduce iron loss to a certain extent. Moreover, the atomic radius of P is larger than that of Fe and Si atoms, which can improve the strength and plasticity of steel and improve efficient processing performance. However, excessive P content will degrade cold working performance, cause material embrittlement, increase the difficulty of cold rolling production and easily cause strip breakage during rolling. Therefore, the mass percentage of P is controlled at 0.010%-0.020%.

[0014] In one embodiment of the present invention, S is a harmful element in non-oriented silicon steel. It easily forms fine MnS with Mn, which causes lattice distortion and increased internal stress, hinders grain growth and magnetic domain movement during finished product annealing, interferes with the magnetization process, and leads to increased iron loss and decreased magnetic induction. Excessive MnS can also cause grain boundary embrittlement and degrade efficient processing performance. Therefore, the mass percentage of S is controlled at ≤0.0020%.

[0015] In one embodiment of the present invention, Ln (lanthanide rare earth) has a strong affinity for O and S, and possesses deep deoxidation and desulfurization capabilities, and can still play a significant purification role when the O and S content is extremely low; lanthanide rare earth interacts with N, which can reduce nitrogen activity, increase nitrogen solubility and reduce dissolved nitrogen, while generating rare earth nitrides to achieve nitrogen fixation, and can also effectively control the morphology, size and distribution of oxide and sulfide inclusions in steel; an appropriate amount of rare earth can promote the aggregation of inclusions, forming uniformly distributed coarse spherical rare earth oxides, sulfides, oxysulfides and their composite inclusions with Mn in the crystal, which can completely replace MnS, reduce the number of inclusions and increase their size, and significantly coarsen the grains after stress-relief annealing, thereby reducing iron loss; however, if the Ln content is too high, the dissolved rare earth is prone to desolvation during heat treatment, leading to grain boundary embrittlement and deterioration of steel performance, so the mass percentage of Ln is controlled at 0.003%-0.005%.

[0016] In one embodiment of the present invention, O and N are harmful elements in non-oriented silicon steel, which are prone to forming fine oxide and nitride impurity points, inhibiting grain growth and degrading magnetic properties; when the content of O and N is too high, it will significantly increase iron loss. Therefore, the mass percentage of O is controlled at ≤0.0020% and the mass percentage of N is controlled at ≤0.0025%.

[0017] In one embodiment of the present invention, the thickness of the aluminum-free, non-oriented silicon steel is 0.35mm-0.50mm.

[0018] The second objective of this invention is to provide a method for preparing the aluminum-free, non-oriented silicon steel, comprising continuous casting, billet heating, rough rolling, finish rolling, laminar flow cooling, acid continuous rolling, and continuous annealing processes.

[0019] In one embodiment of the present invention, the casting speed is 0.9 m / min to 1.1 m / min;

[0020] And / or, the thickness of the slab obtained by continuous casting is 180mm-190mm, the width is 1000mm-1300mm, and the length is 9500mm-10500mm.

[0021] In one embodiment of the present invention, the billet heating is to hot charge the billet into the furnace, with the furnace temperature being 580℃-610℃, the heating time being 170min-182min, and the furnace exit temperature being 1110℃-1125℃.

[0022] In one embodiment of the present invention, the exit temperature of the roughing mill is 950°C-960°C;

[0023] And / or, the thickness of the intermediate billet obtained by rough rolling is 34mm-38mm.

[0024] In one embodiment of the present invention, the exit temperature of the finishing mill is 850°C-860°C, and the total reduction rate is 93.1%-94.2%.

[0025] In one embodiment of the present invention, the outlet temperature of the laminar flow cooling is 640°C-660°C.

[0026] In one embodiment of the present invention, the continuous acid rolling includes pickling, rinsing and cold rolling;

[0027] And / or, the pickling medium is a hydrochloric acid solution with a temperature of 78℃-85℃ and a concentration of 100g / L-150g / L;

[0028] And / or, the rinsing medium is a rinsing solution with a temperature of 65℃-75℃, the pH of the rinsing solution at the outlet is >6, and the conductivity of the rinsing solution at the outlet is ≤30μS / cm.

[0029] And / or, the total reduction rate of the cold rolling is 78.0%-84.5%.

[0030] In one embodiment of the present invention, the dew point inside the furnace during continuous annealing is -22°C to -15°C, and the tension is 3.8 N / mm. 2 -4.8N / mm 2 The heating rate is 29℃ / s-32℃ / s, the annealing temperature is 940℃-960℃, the strip speed is 135m / min-150m / min, and the holding time is 53s-56s.

[0031] In one embodiment of the present invention, the continuous annealing is carried out in a mixed atmosphere of nitrogen and hydrogen; the volume percentage of hydrogen is 18%-28%.

[0032] The technical solution of the present invention has the following advantages compared with the prior art:

[0033] (1) The aluminum-free, non-oriented silicon steel of the present invention adopts a C-Si-Ln composition system, and simultaneously satisfies a specific lanthanide rare earth ratio and rare earth index I. LnWithout adding Al and reducing Si content, by relying on the deep deoxidation and desulfurization of lanthanide rare earth Ln and controlling the morphology, size and distribution of inclusions, steel purification, inclusion reduction and coarsening and spheroidization are achieved. This avoids the defects of surface alumina slag spots from the root and simultaneously improves the surface quality, magnetic properties and high-efficiency processing performance of non-oriented silicon steel.

[0034] (2) The aluminum-free and non-oriented silicon steel described in this invention is designed with a C-Si-Ln composition system and precise control of dimensions throughout the entire process. It adopts a continuous rolling process without normalizing acid, which greatly shortens the process flow and production cycle, significantly reduces energy consumption and manufacturing costs, and improves production efficiency. It belongs to a low-energy-consumption and environmentally friendly manufacturing process that is energy-saving, low-carbon, green, cost-reducing and efficiency-enhancing. It can effectively improve the customer's processing yield and support the upgrading of motor energy efficiency level. Attached Figure Description

[0035] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:

[0036] Figure 1 A photograph of the aluminum-free, non-oriented silicon steel prepared in Example 1 of this invention;

[0037] Figure 2 This is a physical image of the non-oriented silicon steel prepared in Comparative Example 1 of the present invention. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0039] Example 1

[0040] The elemental composition and mass percentage of the aluminum-free, non-oriented silicon steel in this embodiment are as follows: C 0.0017%, Si 1.33%, Mn 0.31%, P 0.013%, S 0.0009%, Ln 0.004%, O 0.0003%, N 0.0008%, with the balance being Fe and other unavoidable impurities;

[0041] Ln is composed of La, Pr and Nd in a mass ratio of 5.5:2.5:1;

[0042] Rare Earth Index I Ln =3.275-[1-(Ln)] 1.315 / [7.8(O)+3.46(S)] 0.137 =1.24;

[0043] Its preparation specifically includes the following steps:

[0044] S1. After melting the raw materials into molten steel according to the preset composition, the steel is continuously cast at a casting speed of 1.0 m / min to produce a billet with a thickness of 185 mm, a width of 1150 mm, and a length of 10000 mm.

[0045] S2. The billet is hot-charged into the furnace at a temperature of 599℃. After 175 minutes of heating, the exit temperature reaches 1115℃. Rough rolling is then performed using a two-stand (R1+R2) rolling mill with 1+5 passes. R1 is rolled in 1 pass and R2 in 5 passes. The roughing mill exit temperature is 958℃, resulting in an intermediate billet thickness of 35mm. The intermediate billet is then finished, with a total reduction of 93.7% and an exit temperature of 855℃. After laminar cooling, the laminar cooling exit temperature is 644℃, yielding a hot-rolled steel strip.

[0046] S3. The temperature of the hot-rolled steel is controlled below 45℃, and pickling is performed using industrial hydrochloric acid with a concentration of 125g / L and a temperature of 81℃. Then, it is cold-rolled with a total cold rolling reduction of 84.1% to obtain cold-rolled steel strip.

[0047] S4. Continuous annealing is carried out in a mixed atmosphere of N2 and H2, wherein the volume percentage of H2 is 23%, the dew point in the furnace is -17℃, and the tension is 4.4 N / mm. 2 The heating rate was 30.62℃ / s, the annealing temperature was 944℃, the strip speed was 144m / min, the holding time was 53.8s, and after continuous annealing, an insulating film layer was coated on the upper and lower surfaces of the material and then finished to obtain aluminum-free, non-oriented silicon steel with a thickness of 0.35mm.

[0048] Example 2

[0049] The elemental composition and mass percentage of the aluminum-free, non-oriented silicon steel in this embodiment are as follows: C 0.0018%, Si 1.38%, Mn 0.30%, P 0.011%, S 0.0013%, Ln 0.005%, O 0.0003%, N 0.0005%, with the balance being Fe and other unavoidable impurities;

[0050] Ln is composed of La, Pr and Nd in a mass ratio of 5.5:2.5:1;

[0051] Rare Earth Index I Ln =3.275-[1-(Ln)] 1.315 / [7.8(O)+3.46(S)] 0.137 =1.31;

[0052] Its preparation specifically includes the following steps:

[0053] S1, the same as S1 in Example 1;

[0054] S2. The billet is hot-charged into the furnace at a temperature of 595℃. After 179 minutes of heating, the exit temperature reaches 1113℃. Rough rolling is then performed using a two-stand (R1+R2) rolling mill with 1+5 passes. R1 is rolled in 1 pass and R2 in 5 passes. The roughing mill exit temperature is 955℃, resulting in an intermediate billet thickness of 35mm. The intermediate billet is then finished, with a total reduction of 93.7% and an exit temperature of 853℃. After laminar cooling, the laminar cooling exit temperature is 653℃, yielding a hot-rolled steel strip.

[0055] S3. The temperature of the hot-rolled steel is controlled below 45℃, and pickling is performed using industrial hydrochloric acid with a concentration of 125g / L and a temperature of 83℃. Then, it is cold-rolled with a total cold rolling reduction of 84.1% to obtain cold-rolled steel strip.

[0056] S4. Continuous annealing is carried out in a mixed atmosphere of N2 and H2, wherein the volume percentage of H2 is 21%, the dew point in the furnace is -20℃, and the tension is 4.5 N / mm. 2 The heating rate was 31.12℃ / s, the annealing temperature was 953℃, the strip speed was 145m / min, the holding time was 53.4s, and after continuous annealing, an insulating film layer was coated on the upper and lower surfaces of the material and then finished to obtain aluminum-free, non-oriented silicon steel with a thickness of 0.35mm.

[0057] Example 3

[0058] The elemental composition and mass percentage of the aluminum-free, non-oriented silicon steel in this embodiment are as follows: C 0.0015%, Si 1.35%, Mn 0.33%, P 0.012%, S 0.0008%, Ln 0.005%, O 0.0005%, N 0.0009%, with the balance being Fe and other unavoidable impurities;

[0059] Ln is composed of La, Pr and Nd in a mass ratio of 5.5:2.5:1;

[0060] Rare Earth Index I Ln =3.275-[1-(Ln)] 1.315 / [7.8(O)+3.46(S)] 0.137 =1.30;

[0061] Its preparation specifically includes the following steps:

[0062] S1, the same as S1 in Example 1;

[0063] S2. The billet is hot-charged into the furnace at a temperature of 587℃. After 173 minutes of heating, the exit temperature reaches 1123℃. Rough rolling is then performed using a two-stand (R1+R2) rolling mill with 1+5 passes. R1 is rolled in 1 pass and R2 in 5 passes. The roughing mill exit temperature is 953℃, resulting in an intermediate billet thickness of 36mm. The intermediate billet is then finished, with a total reduction of 93.6% and an exit temperature of 857℃. After laminar cooling, the laminar cooling exit temperature is 651℃, yielding a hot-rolled steel strip.

[0064] S3. The temperature of the hot-rolled steel is controlled below 45℃, and pickling is performed using industrial hydrochloric acid with a concentration of 125g / L and a temperature of 80℃. Then, it is cold-rolled with a total cold rolling reduction of 78.3% to obtain cold-rolled steel strip.

[0065] S4. Continuous annealing is carried out in a mixed atmosphere of N2 and H2, wherein the volume percentage of H2 is 25%, the dew point in the furnace is -18℃, and the tension is 4.1 N / mm. 2 The heating rate was 29.77℃ / s, the annealing temperature was 951℃, the strip speed was 139m / min, the holding time was 55.7s, and after continuous annealing, an insulating film layer was coated on the upper and lower surfaces of the material and then finished to obtain aluminum-free, non-oriented silicon steel with a thickness of 0.50mm.

[0066] Comparative Example 1

[0067] The composition is basically the same as in Example 1, except that the elemental composition and mass percentage of the non-oriented silicon steel are as follows: C is 0.0023%, Si is 1.37%, Mn is 0.35%, Al is 0.19%, P is 0.017%, S is 0.0019%, O is 0.0003%, N is 0.0006%, and the balance is Fe and other unavoidable impurities.

[0068] Comparative Example 2

[0069] The composition is basically the same as in Example 1, except that the elemental composition and mass percentage of the aluminum-free, non-oriented silicon steel are as follows: C 0.0021%, Si 1.36%, Mn 0.44%, P 0.019%, S 0.0019%, Ln 0.004%, O 0.0017%, N 0.0009%, with the balance being Fe and other unavoidable impurities.

[0070] Ln is composed of La, Pr and Nd in a mass ratio of 5.5:2.5:1;

[0071] Rare Earth Index I Ln =3.275-[1-(Ln)] 1.315 / [7.8(O)+3.46(S)] 0.137 =1.57.

[0072] Test Example 1

[0073] Physical images of the non-oriented silicon steel prepared in Example 1 and Comparative Example 1 are shown below. Figures 1-2 As shown. From Figures 1-2 It can be seen that the aluminum-free non-oriented silicon steel prepared in Example 1 has a clean and defect-free surface with high smoothness after pickling, and excellent surface quality and processing performance. It can stably realize the short-process and efficient production of aluminum-free non-oriented silicon steel. The overall process is energy-saving, cost-reducing, and efficiency-enhancing, with significant social and economic benefits, and belongs to a low-energy green manufacturing process. The aluminum-containing non-oriented silicon steel prepared in Comparative Example 1 has obvious slag spots on its surface after pickling, and the surface quality of the finished product is poor. The root cause is that Al element was added in Comparative Example 1. This element easily forms alumina inclusions during hot rolling and annealing. Alumina slag spots are formed on the surface. However, Example 1 adopts an aluminum-free design, replacing Al with lanthanide rare earth Ln in a specific ratio of La, Pr, and Nd. Relying on the deep deoxidation and desulfurization of rare earth elements and the regulation of the morphology, size, and distribution of inclusions, the defects of alumina slag spots are avoided from the root. At the same time, with precise full-process process control, the steel is effectively purified and spheroidized inclusions are coarsened. This not only ensures the stability of the magnetic properties of silicon steel, but also significantly improves the surface quality and high-efficiency processing performance, which can fully meet the stringent requirements of high-end motor manufacturing for surface quality and processing performance.

[0074] Test Example 2

[0075] Mechanical properties and other tests were performed on the non-oriented silicon steel prepared in the examples and comparative examples:

[0076] (1) Yield strength, tensile strength, and elongation: determined according to the methods specified in GB / T 228.1-2010 "Metallic materials, tensile testing - Part 1: Test at room temperature";

[0077] (2) Hardness HV1: The hardness was determined according to the method specified in GB / T 4340.1-2024 "Metallic materials Vickers hardness test - Part 1: Test method";

[0078] (3) Magnetic properties: The magnetic properties of electrical steel strips (sheets) shall be measured in accordance with the method specified in GB / T 3655-2022 "Method for measuring the magnetic properties of electrical steel strips (sheets) using Epstein squares";

[0079] Table 1 shows the final measured results:

[0080] Table 1

[0081]

[0082] As can be seen from Table 1, the aluminum-free, non-oriented silicon steel obtained in the embodiments of the present invention has both excellent magnetic properties and good mechanical properties, and can stably meet the usage requirements of medium and high grade non-oriented silicon steel.

[0083] Comparing Example 1 and Comparative Example 1, it can be seen that Example 1 has lower iron loss, higher magnetic induction, and better surface quality and performance. The reason is that Comparative Example 1 adds Al element, which easily generates alumina inclusions and causes surface slag spots, while degrading magnetic properties. In contrast, Example 1 adopts an aluminum-free rare earth composition design, which relies on lanthanide rare earth for deep deoxidation and desulfurization, and purification of steel, eliminating alumina defects from the root and simultaneously improving magnetic properties and surface quality.

[0084] Comparing Example 1 and Comparative Example 2, it can be seen that Example 1 has better magnetic properties and better stability; the reason is that the rare earth index I of Comparative Example 2 is higher. Ln Beyond the specified range, rare earth elements are insufficient in controlling the morphology, size, and distribution of inclusions, making it difficult to fully optimize the magnetic domain structure. However, in Example 1, the rare earth index is within the reasonable range of 1.15-1.35, allowing the rare earth purification and inclusion modification effects to be fully utilized, resulting in a significant improvement in magnetic properties.

[0085] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A non-aluminum, non-oriented silicon steel, characterized in that, The elemental composition and mass percentage of the aluminum-free, non-oriented silicon steel are as follows: C≤0.0020%, Si 1.00%-1.50%, Mn 0.30%-0.45%, P 0.010%-0.020%, S≤0.0020%, Ln 0.003%-0.005%, O≤0.0020%, N≤0.0025%, with the balance being Fe and other unavoidable impurities; Ln is composed of La, Pr and Nd in a mass ratio of (5-6):(2-3):1; Rare Earth Index I Ln =3.275-[1-(Ln)] 1.315 / [7.8(O)+3.46(S)] 0.137 =1.15-1.

35.

2. The method for preparing aluminum-free, non-oriented silicon steel as described in claim 1, characterized in that, It includes continuous casting, billet heating, rough rolling, finish rolling, laminar flow cooling, acid continuous rolling, and continuous annealing processes.

3. The method for preparing aluminum-free, non-oriented silicon steel according to claim 2, characterized in that, The casting speed is 0.9 m / min - 1.1 m / min; And / or, the thickness of the slab obtained by continuous casting is 180mm-190mm, the width is 1000mm-1300mm, and the length is 9500mm-10500mm.

4. The method for preparing aluminum-free, non-oriented silicon steel according to claim 2, characterized in that, The billet heating process involves hot-charging the billet into a furnace at an initial temperature of 580℃-610℃, a heating time of 170min-182min, and an exit temperature of 1110℃-1125℃.

5. The method for preparing aluminum-free, non-oriented silicon steel according to claim 2, characterized in that, The exit temperature of the roughing mill is 950℃-960℃; And / or, the thickness of the intermediate billet obtained by rough rolling is 34mm-38mm.

6. The method for preparing aluminum-free, non-oriented silicon steel according to claim 2, characterized in that, The exit temperature of the finishing mill is 850℃-860℃, and the total reduction rate is 93.1%-94.2%.

7. The method for preparing aluminum-free, non-oriented silicon steel according to claim 2, characterized in that, The outlet temperature of the laminar flow cooling is 640℃-660℃.

8. The method for preparing aluminum-free, non-oriented silicon steel according to claim 2, characterized in that, The continuous acid rolling process includes pickling, rinsing, and cold rolling. And / or, the pickling medium is a hydrochloric acid solution with a temperature of 78℃-85℃ and a concentration of 100g / L-150g / L; And / or, the rinsing medium is a rinsing solution with a temperature of 65℃-75℃, the pH of the rinsing solution at the outlet is >6, and the conductivity of the rinsing solution at the outlet is ≤30μS / cm. And / or, the total reduction rate of the cold rolling is 78.0%-84.5%.

9. The method for preparing aluminum-free, non-oriented silicon steel according to claim 2, characterized in that, The continuous annealing process involves a furnace dew point ranging from -22°C to -15°C and a stress of 3.8 N / mm². 2 -4.8N / mm 2 The heating rate is 29℃ / s-32℃ / s, the annealing temperature is 940℃-960℃, the strip speed is 135m / min-150m / min, and the holding time is 53s-56s.

10. The method for preparing aluminum-free, non-oriented silicon steel according to claim 2, characterized in that, The continuous annealing is carried out in a mixed atmosphere of nitrogen and hydrogen; the volume percentage of hydrogen is 18%-28%.

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