High-grade non-oriented silicon steel and normalizing-free production method thereof

Abstract

The application discloses a high-grade non-oriented silicon steel and a normalizing-free production method thereof. In the non-oriented silicon steel, C is less than or equal to 0.003 %, Si is 2.5-3.5 %, Al is 0.5-1.2 %, Mn is 0.2-0.8 %, Sn is 0.01-0.15 %, S is less than or equal to 0.0025 %, N is less than or equal to 0.0030 %, P is less than or equal to 0.03 %, Nb+Ti+V is less than or equal to 0.0050 %, and the rest is Fe and impurities. The production method is free of the normalizing process. During annealing, the cold-rolled strip steel is subjected to continuous recrystallization annealing in an annealing furnace, and the O content in the annealing furnace is controlled to be less than or equal to 20 ppm. When the temperature in the annealing furnace is less than the Curie temperature Tc, the heating rate V1 is controlled to be 80-1000 ℃ / s. When the temperature in the annealing furnace is greater than or equal to the Curie temperature Tc, the heating rate V2 is controlled to be 10-30 ℃ / s. After the temperature in the annealing furnace reaches 950-1020 ℃, the temperature is kept for 20-100 s.

Description

Technical Field

[0001] This application belongs to the field of iron and steel smelting technology, and relates to a method for producing high-grade non-oriented silicon steel without normalization, and also relates to a high-grade non-oriented silicon steel prepared by the method without normalization. Background Technology

[0002] Non-oriented silicon steel, as a soft magnetic material with excellent electromagnetic properties, is widely used in the power, electronics, and military fields. With technological advancements, non-oriented silicon steel is continuously developing towards higher magnetic induction and lower iron loss to meet the demands for miniaturization and higher efficiency in motor cores. High-grade non-oriented silicon steel, in particular, not only improves the energy conversion efficiency and output power of motors and extends their service life, but also reduces material costs, leading to its widespread application.

[0003] High-grade non-oriented silicon steel is typically produced through a process route of steelmaking-hot rolling-normalizing-cold rolling-annealing. In particular, for non-oriented silicon steel with a Si content ≥2%, normalizing is required when using a single cold rolling process to increase and homogenize the recrystallized grains in the hot-rolled plate, coarsen the grains and precipitates, strengthen the {100} and {110} components, and weaken the {111} component, thereby improving the magnetic properties of non-oriented silicon steel.

[0004] Compared to low- and medium-grade non-oriented silicon steel, high-grade non-oriented silicon steel has a more complex production process due to the addition of a normalizing process, resulting in higher production costs. Summary of the Invention

[0005] The purpose of this invention application is to provide a method for producing high-grade non-oriented silicon steel without normalization, and a high-grade non-oriented silicon steel prepared by the method described above.

[0006] To achieve one of the above objectives, one embodiment of this application provides a method for producing high-grade non-oriented silicon steel without normalization. The chemical composition of the non-oriented silicon steel, by mass percentage, includes: C≤0.003%, Si 2.5~3.5%, Al 0.5~1.2%, Mn 0.2~0.8%, Sn 0.01~0.15%, S≤0.0025%, N≤0.0030%, P≤0.03%, Nb+Ti+V≤0.0050%, with the remainder being Fe and unavoidable impurities.

[0007] The production method includes the following sequential processes: steelmaking, continuous casting, hot rolling, pickling, cold rolling, annealing, and coating.

[0008] In the hot rolling process, the continuously cast billet is heated, rough rolled, and finish rolled in sequence to obtain hot rolled strip steel;

[0009] In the annealing process, the cold-rolled strip steel is continuously recrystallized and annealed in an annealing furnace, and the O content in the annealing furnace is controlled to be ≤20ppm; when the temperature in the annealing furnace is <Curie temperature Tc, the heating rate V1 is controlled to be 80~1000℃ / s; when the temperature in the annealing furnace is ≥Curie temperature Tc, the heating rate V2 is controlled to be 10~30℃ / s; after the temperature in the annealing furnace reaches the target temperature, it is held at 950~1020℃ for 20~100s.

[0010] As a further improvement to one embodiment of this application, V1≥866.6-9366×[Sn]+29274×[Sn] 2 Wherein, [Sn] is the percentage value of Sn content in non-oriented silicon steel.

[0011] As a further improvement of one embodiment of this application, the Curie temperature Tc is 720~740°C.

[0012] As a further improvement of one embodiment of this application, in the annealing process, the protective atmosphere of the annealing furnace is a mixture of N2+H2 gas or pure N2, and the content of H2 in the N2+H2 mixture is ≤60%.

[0013] As a further improvement of one embodiment of this application, in the continuous casting process, electromagnetic stirring is adopted, the frequency of electromagnetic stirring is ≥6Hz, and the equiaxed crystal ratio of the continuous casting billet is ≥50%.

[0014] As a further improvement of one embodiment of this application, in the hot rolling process, the heating temperature is 1080~1130℃, the heating time is ≥150min, the initial rolling temperature of rough rolling is ≥1000℃, the final rolling temperature of finish rolling is ≥850℃, and the coiling temperature is ≤650℃.

[0015] As a further improvement of one embodiment of this application, in the pickling process, an acid solution is used to pickle the hot-rolled strip steel to remove the oxide scale on its surface. The acid solution is selected from hydrochloric acid, sulfuric acid, and phosphoric acid. The acid concentration in the acid solution is 50-70%, and the pickling temperature is 60-90°C.

[0016] As a further improvement of one embodiment of this application, in the cold rolling process, the hot-rolled strip steel after pickling is cold rolled at room temperature. The cold rolling is carried out by single stand rolling in multiple passes or by continuous rolling mill, and the total reduction rate is controlled to be ≥70%.

[0017] To achieve the above-mentioned application objectives, one embodiment of this application also provides a high-grade non-oriented silicon steel, which is prepared by the non-normalization production method described above.

[0018] As a further improvement to one embodiment of this application, the thickness of the high-grade non-oriented silicon steel finished product is 0.35~0.65mm, and its iron loss P 1.5 / 50 The magnetic flux density is 2.1~3.1 W / kg, and the magnetic induction intensity B is... 50 ≥1.64T.

[0019] Compared with the prior art, the beneficial effects of this application are as follows:

[0020] The method for producing high-grade non-oriented silicon steel without normalizing, through chemical composition design, increases the content of Si and Als to reduce iron loss, and adds Sn. Furthermore, it controls the heating rate at different temperature ranges during annealing, using a higher heating rate below the Curie temperature and a lower heating rate above the Curie temperature, and holding the steel at the target temperature for a period of time. This eliminates the normalizing process, promotes texture optimization, improves magnetic induction intensity, and gives the non-oriented silicon steel excellent magnetic properties. Moreover, it simplifies the process, saves production costs, and enhances product competitiveness. Detailed Implementation

[0021] One embodiment of this application provides a method for producing high-grade non-oriented silicon steel without normalization, and a high-grade non-oriented silicon steel produced using the method without normalization.

[0022] The following is a detailed description of the non-normalization production method for high-grade non-oriented silicon steel, which includes sequential processes such as steelmaking, continuous casting, hot rolling, pickling, cold rolling, annealing, and coating.

[0023] In this embodiment, the chemical composition of the high-grade non-oriented silicon steel, by mass percentage, includes: C≤0.003%, Si 2.5~3.5%, Al 0.5~1.2%, Mn 0.2~0.8%, Sn 0.01~0.15%, S≤0.0025%, N≤0.0030%, P≤0.03%, Nb+Ti+V≤0.0050%, with the remainder being Fe and unavoidable impurities.

[0024] The roles of each element in the chemical composition design scheme for non-oriented silicon steel are explained below.

[0025] C: In non-oriented silicon steel, it is considered a harmful element. High C content easily leads to magnetic aging, and high C content in the finished product will result in iron loss (P). 15 / 50 The carbon content is large, so it needs to be controlled at a low level. In this application, C is controlled to be ≤0.003%.

[0026] Si can effectively increase the resistivity of electromagnetic steel sheets and reduce iron loss, while also effectively increasing the strength of the steel sheets. However, increasing the Si content leads to increased material hardness and brittleness, thereby increasing the risk of fracture during the production process. In this application, the Si content is controlled at 2.5~3.5%.

[0027] Al: It can increase resistivity and reduce eddy current losses. Since the atomic radius of Al is smaller than that of Si, increasing the Al content can reduce lattice distortion; compared with adding Si, adding the same amount of Al results in a smaller increase in the material's brittleness and hardness, and can also improve the material's processability and magnetic properties; however, if the Al content is too high, it will lead to a decrease in the material's formability. In this application, the Al content is controlled at 0.5~1.2%.

[0028] Mn: It is also an element that increases resistivity. Mn can reduce iron loss to a certain extent. Mn can form MnS with S, thereby preventing the formation of low-melting-point FeS along the grain boundaries, which would cause hot brittleness in hot-rolled plates.

[0029] Sn: Sn is a surface-enriched and grain-bound element that can suppress surface nitriding and oxygen infiltration in finished steel plates during heat treatment. It can also improve magnetic induction by improving annealing texture. 50 This reduces iron loss. However, excessive Sn can cause the steel plate to become brittle, so the Sn content is controlled at 0.01~0.15% in this application.

[0030] S: S reacts with Mn to form fine MnS, which strongly hinders grain growth during annealing of the finished product. As the S content increases, the magnetic properties deteriorate. In addition, excessive MnS deposition can make the grain boundaries brittle, resulting in thermal brittleness and reduced processing performance. Therefore, the S content in this application is controlled to be ≤0.0025%.

[0031] Nitrogen (N): Nitrogen is a harmful element that easily forms fine AlN particles, inhibiting grain growth. When the N content exceeds 0.0030%, it can significantly increase iron loss. In this application, the N content is controlled to be ≤0.0030%.

[0032] P: P has a larger atomic radius than Fe and Si, which helps to improve strength and punching properties. However, excessive P content can lead to poor cold workability and material embrittlement. Therefore, in this application, the P content is controlled to be ≤0.03%.

[0033] Nb, Ti, and V tend to form smaller C and N compounds, which not only hinder grain growth but also promote the formation of undesirable textures. Therefore, in this application, Nb+Ti+V is controlled to be ≤0.0050%.

[0034] Overall, in terms of chemical composition design, this application adds Sn to reduce iron loss by increasing the content of Si and Als, which is beneficial for optimizing the texture in subsequent annealing processes and improving magnetic induction intensity.

[0035] The method for producing high-grade non-oriented silicon steel without normalization according to this embodiment includes the following steps.

[0036] (1) Steelmaking process

[0037] Steelmaking is carried out sequentially using KR desulfurization, converter smelting, and RH refining according to the aforementioned chemical composition design scheme. Thus, the chemical composition of the molten steel obtained in the final steelmaking process, by mass percentage, includes: C≤0.003%, Si 2.5~3.5%, Al 0.5~1.2%, Mn 0.2~0.8%, Sn 0.01~0.15%, S≤0.0025%, N≤0.0030%, P≤0.03%, Nb+Ti+V≤0.0050%, with the remainder being Fe and unavoidable impurities.

[0038] (2) Continuous casting process

[0039] The molten steel obtained from smelting is used to prepare a continuous casting billet with a thickness of 200~250mm using continuous casting equipment. The specific operation of this continuous casting process can be achieved using existing feasible continuous casting technologies, and will not be elaborated further.

[0040] Preferably, during continuous casting, electromagnetic stirring is employed, with a stirring frequency ≥6Hz and an equiaxed crystal ratio ≥50% in the continuously cast billet. By performing electromagnetic stirring above the bending point of the continuous casting machine, before the interior of the billet has solidified, coarse columnar crystals can be prevented from forming in the central region of the billet, thereby forming equiaxed crystals, preventing corrugated defects, reducing the generation of unfavorable textures in subsequent processes, and laying the foundation for avoiding normalization.

[0041] (3) Hot rolling process

[0042] The continuously cast billets obtained from the continuous casting process are sequentially heated, rough rolled, and finish rolled to obtain hot-rolled strip steel. The hot-rolled strip steel is further cooled and coiled to obtain hot-rolled coils.

[0043] Specifically, the continuously cast billet is rolled into an intermediate billet with a thickness of 35-40 mm through multiple rough rolling passes, and then rolled into a hot-rolled strip with a thickness of 2.00-2.70 mm through multiple finish rolling passes. After cooling, it is coiled into a hot-rolled coil.

[0044] The heating temperature is 1080~1130℃, and the heating time is ≥150min. Higher billet heating temperature and longer heating time can improve the hot rolling plasticity of the continuously cast billet, but it will lead to a decrease in the magnetic properties of the final non-oriented silicon steel product. Therefore, the heating temperature should be controlled as low as possible within the capacity of the rolling mill.

[0045] Specifically, continuously cast billets can be hot-charged and fed into the heating furnace for heating, or they can be cooled before being fed into the heating furnace for heating. Thus, in actual production, the choice can be made based on the specific production situation.

[0046] The initial rolling temperature of the roughing mill is ≥1000℃, the final rolling temperature of the finishing mill is ≥850℃, and the coiling temperature is ≤650℃.

[0047] Thus, based on the aforementioned chemical composition design, the hot rolling process employs low-temperature rolling and low-temperature coiling. Combined with the control of the heating time and duration of the continuously cast billet, while ensuring production efficiency and facilitating the subsequent high-temperature final rolling of the finishing mill, the probability of fine MnS and Al(C,N) precipitation is reduced. This prevents the solid solution of precipitates such as MnS in the steel during the heating process, which is conducive to the growth of the microstructure grains and thus ensures the excellent magnetic properties of the resulting non-oriented silicon steel product. In addition, by controlling the thickness of the intermediate billet after rough rolling, the final rolling temperature of the finishing mill is controlled in the high-temperature ferrite region to facilitate the formation of high-temperature ferrite and avoid the formation of deformed fibrous structures.

[0048] (4) Pickling process

[0049] Hot-rolled strip steel is pickled with an acid solution to remove oxide scale from its surface. The acid solution is selected from hydrochloric acid, sulfuric acid, and phosphoric acid. The acid concentration in the acid solution is 50-70%, and the pickling temperature is 60-90℃.

[0050] (5) Cold rolling process

[0051] After pickling, the hot-rolled strip steel is cold-rolled at room temperature. The cold rolling is carried out by single-stand multi-pass rolling or by continuous rolling mill. The total reduction rate of cold rolling is controlled to be ≥70% to obtain cold-rolled strip steel with a thickness of 0.35~0.65mm to meet the dimensional requirements of high-grade non-oriented silicon steel.

[0052] By controlling the total reduction rate, precise control of the final product thickness can be achieved, reducing the strip breakage rate during cold rolling, increasing the yield of high-grade non-oriented silicon steel, reducing production costs, and improving production efficiency.

[0053] (6) Annealing process

[0054] The cold-rolled strip steel is subjected to continuous recrystallization annealing in an annealing furnace, with the oxygen content in the furnace controlled to be ≤20ppm. Specifically, when the temperature in the annealing furnace is < Curie temperature Tc, the heating rate V1 is controlled at 80~1000℃ / s; when the temperature in the annealing furnace is ≥ Curie temperature Tc, the heating rate V2 is controlled at 10~30℃ / s; after the temperature in the annealing furnace reaches the target temperature, it is held at 950~1020℃ for 20~100s.

[0055] The Curie temperature (Tc) refers to the temperature at which the spontaneous magnetization of a magnetic material drops to zero. It is the critical point at which ferromagnetic or ferrimagnetic materials transform into paramagnetic materials. Below the Curie temperature (Tc), the magnetic material becomes ferromagnetic, and the magnetic field associated with the material is difficult to change. However, when the temperature is above the Curie temperature (Tc), the magnetic material becomes paramagnetic, and the magnetic field of the magnet changes easily with changes in the surrounding magnetic field.

[0056] In this embodiment, the Curie temperature Tc of the non-oriented silicon steel is 720~740℃. The Curie temperature Tc is related to the Si content in the non-oriented silicon steel; generally, the higher the Si content, the lower the Curie temperature Tc.

[0057] During continuous recrystallization annealing, the magnetic induction of non-oriented silicon steel gradually decreases as the annealing temperature increases. When the annealing temperature is below the Curie temperature Tc, non-oriented silicon steel exhibits strong ferromagnetism. At this temperature, rapid heating at a higher heating rate can increase the nucleation temperature of recrystallized grains, preventing grains with undesirable textures from nucleating at lower temperatures, thereby optimizing the texture. When the annealing temperature rises above the Curie temperature Tc, non-oriented silicon steel becomes paramagnetic. Using a lower heating rate is more conducive to the growth of recrystallized grains. Furthermore, when the temperature in the annealing furnace reaches 950~1020℃ and is held for 20~100s, the recrystallization texture can be optimized, enabling the non-oriented silicon steel to acquire excellent magnetic properties.

[0058] Preferably, the heating rate V1 is 100~800℃ / s.

[0059] More preferably, the heating rate V1 ≥ 866.6 - 9366 × [Sn] + 29274 × [Sn] 2 Where [Sn] is the percentage value of Sn content in non-oriented silicon steel. For example, if the Sn content is 0.012%, then [Sn] is 0.012.

[0060] Thus, by controlling the minimum heating rate in the annealing process according to the Sn content in the chemical composition design scheme, the nucleation and growth of recrystallization can be effectively controlled, especially the texture can be optimized and the proportion of favorable texture can be increased, thereby achieving the purpose of increasing the magnetic induction intensity.

[0061] Of course, the heating rate V1 still needs to satisfy V1≤1000℃ / s to achieve better results.

[0062] Preferably, the protective atmosphere of the annealing furnace is a mixture of N2 and H2 or pure N2, wherein the H2 content in the N2+H2 mixture is ≤60%. This helps to control the O content in the annealing furnace to ≤20ppm, thereby reducing surface and internal oxidation of the strip and preventing magnetic degradation.

[0063] When the annealing temperature is below the Curie temperature Tc, electromagnetic induction heating can meet the requirement of a relatively high heating rate. Electromagnetic induction heating results in a rapid temperature rise, ensuring that cold-rolled deformed structures of various texture types receive sufficient recrystallization driving force per unit time, increasing the number of grain nucleation points. In particular, it is beneficial for increasing the recrystallization temperature, thereby resulting in a larger proportion of favorable recrystallization textures.

[0064] (7) Coating process

[0065] A high-grade non-oriented silicon steel is obtained by uniformly coating the upper and lower surfaces of the annealed strip with an insulating coating. The insulation properties of the non-oriented silicon steel can be improved by coating the strip surface with an insulating coating.

[0066] The high-grade non-oriented silicon steel according to one embodiment of this application is prepared using the above-described non-normalization production method. The high-grade non-oriented silicon steel has a thickness of 0.35~0.65 mm, and as previously described, its chemical composition, by mass percentage, includes: C≤0.003%, Si 2.5~3.5%, Al 0.5~1.2%, Mn 0.2~0.8%, Sn 0.01~0.15%, S≤0.0025%, N≤0.0030%, P≤0.03%, Nb+Ti+V≤0.0050%, with the remainder being Fe and unavoidable impurities.

[0067] Testing revealed that the iron loss P of this high-grade non-oriented silicon steel was... 1.5 / 50 The magnetic flux density is 2.1~3.1 W / kg, and the magnetic induction intensity B is... 50 With a magnetic induction capacity of ≥1.64T, it exhibits excellent magnetic induction performance, meeting the energy efficiency requirements for applications in products such as motors.

[0068] Thus, the production method of high-grade non-oriented silicon steel in this application, based on the aforementioned chemical composition design, controls the heating rate in different temperature ranges during annealing. Below the Curie temperature, a larger heating rate is controlled, while above the Curie temperature, a smaller heating rate is used. After reaching the target temperature, the temperature is held for a period of time. This allows for the elimination of the normalizing process, promoting texture optimization and giving the non-oriented silicon steel excellent magnetic properties. Furthermore, it simplifies the process, saves production costs, and improves product competitiveness.

[0069] The detailed descriptions listed above are merely specific descriptions of feasible implementation methods of this application, and are not intended to limit the scope of protection of this application. All equivalent implementation methods or modifications made without departing from the spirit of the art of this application should be included within the scope of protection of this application.

[0070] The beneficial effects of this application will be further illustrated below through 10 embodiments and 11 comparative examples. Of course, these 10 embodiments are only a part of the many variations contained in this application, and not all of them.

[0071] Ten examples and eleven comparative examples each provide a high-grade non-oriented silicon steel. The chemical composition of the steel is shown in Table 1, with Si, Al, Mn and Sn contents. In addition, C≤0.003%, S≤0.0025%, N≤0.0030%, P≤0.03%, Nb+Ti+V≤0.0050%, and the remainder is Fe and unavoidable impurities.

[0072] Table 1

[0073]

[0074] The production methods of high-grade non-oriented silicon steel in 10 embodiments and 11 comparative examples are as follows.

[0075] (1) Steelmaking process

[0076] Steelmaking was carried out sequentially using KR desulfurization, converter smelting, and RH refining, according to the chemical composition design scheme shown in Table 1.

[0077] (2) Continuous casting process

[0078] The molten steel obtained from smelting is used to prepare continuously cast billets with a thickness of 200~250mm using continuous casting equipment. During continuous casting, electromagnetic stirring is adopted, with a frequency of ≥6Hz, and the equiaxed crystal ratio of the continuously cast billets is measured to be ≥50%.

[0079] (3) Hot rolling process

[0080] After heating the continuously cast billet obtained from the continuous casting process, it first undergoes multiple rough rolling passes to form an intermediate billet with a thickness of 35~40mm, and then undergoes multiple finish rolling passes to form a hot-rolled strip with a thickness of 2.00~2.70mm. After laminar flow cooling, it is coiled into a hot-rolled coil.

[0081] The heating temperature, heating time, roughing rolling start temperature, finishing rolling finish temperature, and coiling temperature of each embodiment and comparative example are shown in Table 2.

[0082] Table 2

[0083]

[0084] (4) Pickling process

[0085] Hot-rolled strip steel is pickled with an acid solution to remove oxide scale from its surface. The acid solution is selected from hydrochloric acid, sulfuric acid, and phosphoric acid. The acid concentration in the acid solution is 50-70%, and the pickling temperature is 60-90℃.

[0086] (5) Cold rolling process

[0087] The hot-rolled strip steel, after pickling, is cold-rolled at room temperature. The cold rolling is carried out using a single stand for multiple passes or a continuous rolling mill to obtain cold-rolled strip steel. The total reduction rate of the cold rolling is controlled to be ≥70%. The thickness of the cold-rolled strip steel is shown in Table 3.

[0088] (6) Annealing process

[0089] The cold-rolled strip steel is continuously recrystallized and annealed in an annealing furnace. The protective atmosphere is a mixture of N2 and H2 or pure N2. The O content in the annealing furnace is controlled to be ≤20ppm. If a mixture of N2 and H2 is used, the H2 content is controlled to be ≤60%.

[0090] During the heating process of the annealing furnace, when the temperature in the annealing furnace is less than the Curie temperature Tc, electromagnetic induction heating is used, and the heating rate V1 is shown in Table 3; when the temperature in the annealing furnace is greater than or equal to the Curie temperature Tc, the heating rate V2 is shown in Table 3; after the temperature in the annealing furnace reaches the target temperature, it is held at that temperature, and the target temperature and holding time are shown in Table 3. The Curie temperature Tc is 720~740℃.

[0091] (7) Coating process

[0092] An insulating coating is uniformly applied to the upper and lower surfaces of the annealed strip to obtain high-grade non-oriented silicon steel.

[0093] In Comparative Example 10, the final rolling temperature of the hot rolling process was too low, resulting in severe edge cracking and making it impossible to continue production. In Comparative Example 11, the coiling temperature of the hot rolling process was too high, making pickling difficult and the surface quality did not meet the requirements, thus causing the product to fall into the defective category, and therefore production was also stopped.

[0094] According to GB / T 3655 standard, the high-grade non-oriented silicon steel products obtained in Examples 1-10 and Comparative Examples 1-9 were subjected to magnetic property testing to obtain their iron loss P. 1.5 / 50 and magnetic induction intensity B 50 The data is shown in Table 3.

[0095] Table 3

[0096]

[0097] In Comparative Examples 1-9, there were instances where the chemical element content or process parameters did not meet the requirements of this application, resulting in a decrease in the magnetic induction intensity B of the final silicon steel product. 50 It does not meet the requirements for use of high-grade non-oriented silicon steel.

[0098] The high-grade non-oriented silicon steel obtained by the non-normalizing production method of one embodiment of this application in Examples 1-10 has excellent magnetic properties. It not only eliminates normalizing but also has good rollability, enabling stable production, greatly saving costs and improving product yield.

[0099] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0100] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for producing high-grade non-oriented silicon steel without normalization, characterized in that, The chemical composition of the non-oriented silicon steel, by mass percentage, includes: C≤0.003%, Si 2.5~3.5%, Al 0.5~1.2%, Mn 0.2~0.8%, Sn 0.01~0.15%, S≤0.0025%, N≤0.0030%, P≤0.03%, Nb+Ti+V≤0.0050%, with the remainder being Fe and unavoidable impurities; The production method includes the following sequential processes: steelmaking, continuous casting, hot rolling, pickling, cold rolling, annealing, and coating. In the hot rolling process, the continuously cast billet is heated, rough rolled, and finish rolled in sequence to obtain hot rolled strip steel; In the annealing process, the cold-rolled strip steel undergoes continuous recrystallization annealing in an annealing furnace, controlling the O content in the annealing furnace to be ≤20ppm; when the temperature in the annealing furnace is < Curie temperature Tc, the heating rate V1 is controlled to be ≤1000℃ / s, and V1≥866.6-9366×[Sn]+29274×[Sn] 2 Where [Sn] is the percentage value of Sn content in non-oriented silicon steel; when the temperature in the annealing furnace is ≥ Curie temperature Tc, the heating rate V2 is controlled to be 10~30℃ / s; after the temperature in the annealing furnace reaches the target temperature, it is held at 950~1020℃ for 20~100s.

2. The method for producing high-grade non-oriented silicon steel without normalization according to claim 1, characterized in that, The Curie temperature (Tc) is 720~740℃.

3. The method for producing high-grade non-oriented silicon steel without normalization according to claim 1, characterized in that, In the annealing process, the protective atmosphere of the annealing furnace is a mixture of N2 and H2 gas or pure N2, and the content of H2 in the N2 and H2 mixture is ≤60%.

4. The method for producing high-grade non-oriented silicon steel without normalization according to claim 1, characterized in that, In the continuous casting process, electromagnetic stirring is adopted, the frequency of electromagnetic stirring is ≥6Hz, and the equiaxed crystal ratio of the continuous casting billet is ≥50%.

5. The method for producing high-grade non-oriented silicon steel without normalization according to claim 1, characterized in that, In the hot rolling process, the heating temperature is 1080~1130℃, the heating time is ≥150min, the initial rolling temperature of rough rolling is ≥1000℃, the final rolling temperature of finish rolling is ≥850℃, and the coiling temperature is ≤650℃.

6. The method for producing high-grade non-oriented silicon steel without normalization according to claim 1, characterized in that, In the pickling process, hot-rolled strip steel is pickled with acid solution to remove oxide scale from its surface. The acid solution is selected from hydrochloric acid, sulfuric acid, and phosphoric acid. The acid concentration in the acid solution is 50-70%, and the pickling temperature is 60-90℃.

7. The method for producing high-grade non-oriented silicon steel without normalization according to claim 1, characterized in that, In the cold rolling process, the hot-rolled strip steel after pickling is cold rolled at room temperature. The cold rolling is carried out by single stand rolling in multiple passes or by continuous rolling mill, and the total reduction rate is controlled to be ≥70%.

8. A high-grade non-oriented silicon steel, characterized in that, It is prepared by the non-normalization production method as described in any one of claims 1 to 7.

9. The high-grade non-oriented silicon steel according to claim 8, characterized in that, The thickness of the high-grade non-oriented silicon steel finished product is 0.35~0.65mm, and its iron loss P 1.5 / 50 The magnetic flux density is 2.1~3.1 W / kg, and the magnetic induction intensity B is... 50 ≥1.64T.

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