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

Abstract

The high-grade non-oriented silicon steel comprises the following components in percentage by weight: less than or equal to 0.003% of C, 2.5-3.5% of Si, 0.5-1.2% of Al, 0.2-0.8% of Mn, 0.01-0.15% of Sn, less than or equal to 0.0025% of S, less than or equal to 0.0030% of N, less than or equal to 0.03% of P, less than or equal to 0.0050% of Nb, Ti and V, and the balance of Fe and impurities. The normalizing procedure is omitted in the production method; 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 smaller than or equal to 20 ppm; the temperature in the annealing furnace is lt; when the Curie temperature is Tc, the heating rate V1 is controlled to be 80-1000 DEG C / s; when the temperature in the annealing furnace is larger than or equal to the Curie temperature Tc, the heating rate V2 is controlled to be 10-30 DEG C / s; and after the temperature in the annealing furnace reaches 950-1020 DEG C, heat preservation is conducted for 20-100 s.

Description

Technical Field

[0001] The present application belongs to the technical field of steel smelting, and relates to a normalization-free production method for high-grade non-oriented silicon steel, and also relates to high-grade non-oriented silicon steel prepared by the normalization-free production method. Background Art

[0002] As a soft magnetic material with excellent electromagnetic properties, non-oriented silicon steel is widely used in the power, electronics, and military sectors. With technological advancements, non-oriented silicon steel continues to develop toward higher magnetic induction and lower iron loss to meet the growing demand for smaller and more efficient motor cores. High-grade non-oriented silicon steel, in particular, not only improves motor energy conversion efficiency and output power, extending its service life, but also reduces material costs, leading to its widespread application.

[0003] Generally, high-grade non-oriented silicon steel is produced through the process of steelmaking-hot rolling-normalizing-cold rolling-annealing. In particular, non-oriented silicon steel with Si content ≥ 2% needs to be normalized when using a single cold rolling process to increase the number of recrystallized grains in the hot-rolled plate and make them more uniform, coarsen the grains and precipitates, strengthen the {100} and {110} components, and weaken the {111} component, thereby improving the magnetic properties of the non-oriented silicon steel.

[0004] Compared with medium and low grade non-oriented silicon steel, high grade non-oriented silicon steel has a relatively complex production process due to the addition of a normalizing process, and the production cost also increases accordingly. Summary of the Invention

[0005] The purpose of the present invention is to provide a normalization-free production method for high-grade non-oriented silicon steel, and a high-grade non-oriented silicon steel prepared by the normalization-free production method.

[0006] To achieve one of the above objectives, an embodiment of the present application provides a normalization-free production method for high-grade non-oriented silicon steel, wherein the chemical composition of the non-oriented silicon steel comprises, by mass percentage, C≤0.003%, Si 2.5-3.5%, Al0.5-1.2%, Mn 0.2-0.8%, Sn 0.01-0.15%, S≤0.0025%, N≤0.0030%, P≤0.03%, Nb+Ti+V≤0.0050%, and the remainder is Fe and unavoidable impurities; The production method includes the following steps: steelmaking, continuous casting, hot rolling, pickling, cold rolling, annealing and coating; In the hot rolling process, the continuous casting billet is sequentially heated, rough rolled, and finish rolled to obtain hot-rolled steel strip; In the annealing process, the cold-rolled steel strip is subjected to continuous recrystallization annealing in an annealing furnace, and the oxygen content in the annealing furnace is controlled to be ≤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°C / 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°C / s; after the temperature in the annealing furnace reaches the target temperature, the target temperature is kept at 950-1020°C for 20-100 seconds.

[0007] As a further improvement of an embodiment of the present application, V1≥866.6-9366×[Sn]+29274×[Sn] 2 , where [Sn] is the percentage value of Sn content in non-oriented silicon steel.

[0008] As a further improvement of an embodiment of the present application, the Curie temperature Tc is 720-740°C.

[0009] As a further improvement of one embodiment of the present application, in the annealing process, the protective atmosphere of the annealing furnace is a N2+H2 mixed gas or pure N2, and the H2 content in the N2+H2 mixed gas is ≤60%.

[0010] As a further improvement of an embodiment of the present application, electromagnetic stirring is adopted in the continuous casting process, the frequency of the electromagnetic stirring is ≥6 Hz, and the proportion of equiaxed crystals in the continuously cast billet is ≥50%.

[0011] As a further improvement of one embodiment of the present application, in the hot rolling process, the heating temperature is 1080~1130℃, the heating time is ≥150min, the starting temperature of rough rolling is ≥1000℃, the finishing temperature of fine rolling is ≥850℃, and the coiling temperature is ≤650℃.

[0012] As a further improvement of one embodiment of the present application, in the pickling process, acid solution is used to pickle the hot-rolled strip to remove the oxide scale on its surface. The acid solution is selected from one of 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.

[0013] As a further improvement of one embodiment of the present application, in the cold rolling process, the hot-rolled strip after pickling is cold rolled at room temperature, and the cold rolling is performed by a single stand for multiple passes or by a continuous rolling mill, and the total reduction rate is controlled to be ≥70%.

[0014] In order to achieve the above application purpose, an embodiment of the present application further provides a high-grade non-oriented silicon steel, which is prepared by the normalization-free production method as described above.

[0015] As a further improvement of an embodiment of the present application, the thickness of the high-grade non-oriented silicon steel product is 0.35~0.65mm, and its iron loss P 1.5 / 50 2.1~3.1W / kg, magnetic induction intensity B 50 ≥1.64T.

[0016] Compared with the prior art, the present invention has the following advantages: The normalization-free production method of high-grade non-oriented silicon steel of the present application, through chemical composition design, adds Sn on the basis of increasing the Si and Als contents to reduce iron loss, further combines with controlling the heating rates in different temperature ranges during annealing, controls a larger heating rate below the Curie temperature, adopts a smaller heating rate above the Curie temperature, and maintains the temperature for a period of time after reaching the target temperature, thereby promoting texture optimization and improving magnetic induction intensity without the normalization process, so that the non-oriented silicon steel has excellent magnetic properties, and simplifies the process flow, saves production costs, and improves product competitiveness. DETAILED DESCRIPTION

[0017] One embodiment of the present application provides a normalization-free production method for high-grade non-oriented silicon steel, and a high-grade non-oriented silicon steel produced by the normalization-free production method.

[0018] The following is a detailed introduction to the normalization-free production method of the high-grade non-oriented silicon steel. The production method includes the following steps: steelmaking, continuous casting, hot rolling, pickling, cold rolling, annealing, coating, etc., which are performed in sequence.

[0019] In this embodiment, the chemical composition of the high-grade non-oriented silicon steel includes, by mass percentage, 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%, and the rest is Fe and unavoidable impurities.

[0020] The role of each element in the chemical composition design scheme in non-oriented silicon steel is explained as follows.

[0021] C: It is considered as a harmful element in non-oriented silicon steel. High C content is prone to magnetic aging, and high C content in finished products will lead to iron loss P 15 / 50 Therefore, the C content needs to be controlled at a low level. In this application, C is controlled to be ≤ 0.003%.

[0022] Si: It effectively increases the resistivity of electromagnetic steel sheets, reduces iron loss, and improves their strength. However, increasing Si content increases the material's hardness and brittleness, increasing the risk of fracture during production. In this application, the Si content is controlled to 2.5-3.5%.

[0023] Al: It increases resistivity and reduces eddy current losses. Because Al has a smaller atomic radius than Si, increasing its content reduces lattice distortion. Compared to adding Si, adding the same amount of Al reduces the increase in material brittleness and hardness, and also improves the material's processability and magnetic properties. However, excessive Al content can impair formability. In this application, the Al content is controlled to 0.5-1.2%.

[0024] 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 and causing hot brittleness of hot-rolled plates.

[0025] Sn: Sn is a surface enrichment and grain boundary segregation element that can inhibit surface nitriding and oxygen permeation of finished steel plates during heat treatment, and can also improve the magnetic induction B by improving the annealing texture. 50 However, excessive Sn can make the steel plate brittle, so the Sn content is controlled to 0.01-0.15% in this application.

[0026] S: S and Mn form fine MnS, which strongly hinders grain growth during finished product annealing. As the S content increases, magnetic properties deteriorate. Furthermore, excessive MnS deposition can embrittle grain boundaries, leading to hot brittleness and reduced processability. Therefore, the S content in this application is controlled to ≤0.0025%.

[0027] N: N is a harmful element that tends to form tiny AlN particles that inhibit grain growth. A N content exceeding 0.0030% can significantly increase iron loss. In this application, the N content is controlled to ≤ 0.0030%.

[0028] P: P has a larger atomic radius than Fe and Si, increasing strength and improving punchability. However, excessive P content can lead to poor cold workability and embrittlement. Therefore, in this application, the P content is controlled to ≤ 0.03%.

[0029] Nb, Ti, and V: They are prone to forming smaller carbon compounds and nitrogen compounds, which not only hinder the growth of grains but also promote the formation of unfavorable textures. Therefore, in this application, Nb+Ti+V is controlled to be ≤ 0.0050%.

[0030] Generally speaking, in terms of chemical composition design, the present application increases the Si and Als contents to reduce iron loss, and then adds Sn, which is beneficial for optimizing the texture in combination with the subsequent annealing process and improving the magnetic induction intensity.

[0031] The normalization-free production method of the high-grade non-oriented silicon steel of this embodiment includes the following steps.

[0032] (1) Steelmaking process Steelmaking is carried out in sequence by KR desulfurization, converter smelting, and RH refining according to the aforementioned chemical composition design scheme. The chemical composition of the molten steel finally obtained from the steelmaking process includes, by mass percentage, the following: 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%, and the remainder is Fe and unavoidable impurities.

[0033] (2) Continuous casting process The molten steel obtained by smelting is prepared into continuous casting billets with a thickness of 200-250 mm using continuous casting equipment. The specific operations of the continuous casting process can be achieved using existing feasible continuous casting technologies and will not be described in detail.

[0034] Preferably, electromagnetic stirring is employed during continuous casting, with a frequency of 6 Hz or higher and a proportion of equiaxed grains of 50% or higher. Electromagnetic stirring, performed above the bend point of the continuous casting machine and before solidification within the continuous casting billet, prevents the formation of coarse columnar grains in the center of the billet, thereby forming equiaxed grains and preventing the formation of corrugated defects. This helps reduce the subsequent occurrence of unfavorable textures and paves the way for avoiding normalization.

[0035] (3) Hot rolling process The continuous casting process produces a continuous slab that is heated, rough rolled, and finish rolled in sequence to produce hot-rolled strip. The hot-rolled strip is then cooled and coiled to produce a hot-rolled coil.

[0036] Specifically, the continuous casting slab is subjected to multiple rough rolling passes to be rolled into an intermediate slab with a thickness of 35-40 mm, and then subjected to multiple finish rolling passes to be rolled into a hot-rolled strip with a thickness of 2.00-2.70 mm. After cooling, it is coiled into a hot-rolled coil.

[0037] The heating temperature is 1080-1130°C, and the heating time is ≥150 minutes. Higher heating temperatures and longer heating times can improve the hot-rolling plasticity of the continuously cast slab, but this can lead to lower magnetic properties in the resulting non-oriented silicon steel product. Therefore, within the capacity of the rolling mill, the heating temperature should be kept as low as possible.

[0038] Specifically, the continuous casting billet can be hot-charged and hot-sent into the heating furnace for heating, or the cooled continuous casting billet can be sent into the heating furnace for heating. In this way, in actual production, the choice can be made according to the actual production situation.

[0039] Among them, the starting rolling temperature of rough rolling is ≥1000℃, the final rolling temperature of finishing rolling is ≥850℃, and the coiling temperature is ≤650℃.

[0040] Thus, on the basis of the design of the aforementioned chemical composition, the hot rolling process adopts low-temperature rolling and low-temperature coiling, combined with the control of the heating time and heating duration of the continuous casting slab, while ensuring production efficiency and being beneficial to the high-temperature final rolling of the subsequent finishing rolling, the probability of precipitation of fine MnS and Al(C,N) is reduced, and the solid solution of precipitates such as MnS in the steel during the heating process is prevented, which is beneficial to the growth of the microstructure grains, thereby ensuring the excellent magnetic properties of the subsequent non-oriented silicon steel products; combined with the control of the thickness of the intermediate slab after rough rolling, the final rolling temperature of the finishing rolling is controlled in the high-temperature ferrite region, so as to form high-temperature ferrite and avoid the formation of deformed fiber structure.

[0041] (4) Pickling process The hot-rolled strip is pickled with an acid solution to remove the oxide scale on its surface. The acid solution is selected from one of 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.

[0042] (5) Cold rolling process The hot-rolled strip after pickling is cold rolled at room temperature. The cold rolling adopts a single stand for multi-pass rolling or a continuous rolling mill for rolling. The total reduction rate of cold rolling is controlled to be ≥70%, and a cold-rolled strip with a thickness of 0.35~0.65mm is obtained to meet the dimensional requirements of high-grade non-oriented silicon steel.

[0043] By controlling the total reduction rate, the thickness of the final product can be accurately controlled, the breakage rate of the steel strip during cold rolling can be reduced, the production yield rate of high-grade non-oriented silicon steel can be increased, production costs can be reduced, and production efficiency can be improved.

[0044] (6) Annealing process The cold-rolled steel strip undergoes continuous recrystallization annealing in an annealing furnace, controlling the oxygen content in the annealing furnace to ≤20ppm. When the annealing furnace temperature is less than the Curie temperature Tc, the heating rate V1 is controlled to be 80-1000°C / s; when the annealing furnace temperature is greater than or equal to the Curie temperature Tc, the heating rate V2 is controlled to be 10-30°C / s. After the annealing furnace temperature reaches the target temperature, it is held at a target temperature of 950-1020°C for a holding time of 20-100s.

[0045] The Curie temperature (Tc) is 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), a magnetic material becomes a ferromagnet, and the magnetic field associated with the material is difficult to change. However, above the Curie temperature (Tc), the magnetic material becomes a paramagnet, and the magnetic field of the magnet easily changes with changes in the surrounding magnetic field.

[0046] In this embodiment, the Curie temperature Tc of the non-oriented silicon steel is 720-740° C. The Curie temperature Tc is related to the Si content in the non-oriented silicon steel. Generally, as the Si content in the non-oriented silicon steel increases, the Curie temperature Tc decreases.

[0047] 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 has strong ferromagnetism. At this time, rapid heating at a higher heating rate can increase the nucleation temperature of recrystallized grains, preventing grains with unfavorable texture from nucleating at lower temperatures, thereby achieving the purpose of optimizing the texture. When the annealing temperature rises above the Curie temperature (Tc), non-oriented silicon steel becomes paramagnetic. A slower heating rate is more conducive to the growth of recrystallized grains. Furthermore, when the temperature in the annealing furnace reaches 950-1020°C and is maintained for 20-100 seconds, the recrystallization texture can be optimized, resulting in non-oriented silicon steel achieving excellent magnetic properties.

[0048] Preferably, the heating rate V1 is 100-800° C. / s.

[0049] More preferably, the heating rate V1 ≥ 866.6-9366×[Sn]+29274×[Sn] 2 , where [Sn] is the percentage of Sn content in non-oriented silicon steel. For example, if the Sn content is 0.012%, then [Sn] is 0.012.

[0050] In this way, 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 is optimized and the proportion of favorable texture is increased, thereby achieving the purpose of improving the magnetic induction intensity.

[0051] Of course, the heating rate V1 still satisfies V1≤1000°C / s to achieve better results.

[0052] Preferably, the protective atmosphere in the annealing furnace is a mixture of N2+H2 or pure N2, with the H2 content in the N2+H2 mixture being ≤60%. This helps control the O content in the annealing furnace to ≤20ppm, thereby reducing surface and internal oxidation of the steel strip and preventing magnetic degradation.

[0053] When the annealing temperature is below the Curie temperature (Tc), electromagnetic induction heating can meet the requirement for a higher heating rate. Electromagnetic induction heating provides a faster temperature rise, providing sufficient driving force for recrystallization of various cold-rolled deformed structures per unit time, increasing the number of grain nucleation sites. This is particularly beneficial for raising the recrystallization temperature, thereby increasing the proportion of favorable recrystallized textures.

[0054] (7) Coating process The insulating coating is evenly applied to the upper and lower surfaces of the annealed steel strip to obtain high-grade non-oriented silicon steel. By applying the insulating coating on the surface of the steel strip, the insulation performance of the non-oriented silicon steel can be improved.

[0055] The high-grade non-oriented silicon steel according to one embodiment of the present application is produced using the above-mentioned normalization-free production method. The high-grade non-oriented silicon steel has a thickness of 0.35-0.65 mm and, as previously described, a chemical composition by mass percentage comprising: 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.

[0056] After testing, the iron loss P of this high grade non-oriented silicon steel 1.5 / 50 2.1~3.1W / kg, magnetic induction intensity B 50 ≥1.64T, with excellent magnetic induction performance, which can meet the energy efficiency requirements of its application in motors and other products.

[0057] Thus, the production method of high-grade non-oriented silicon steel of the present application, based on the aforementioned chemical composition design, controls the heating rates in different temperature ranges during annealing to be different, controls a larger heating rate below the Curie temperature, and adopts a smaller heating rate above the Curie temperature, and keeps the temperature for a period of time after reaching the target temperature. This can promote texture optimization without the normalizing process, so that the non-oriented silicon steel has excellent magnetic properties, and simplifies the process flow, saves production costs, and improves product competitiveness.

[0058] The detailed descriptions listed above are merely specific descriptions of feasible implementation methods of the present application. They are not intended to limit the scope of protection of the present application. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present application should be included in the scope of protection of the present application.

[0059] The following 10 embodiments and 11 comparative examples are used to further illustrate the beneficial effects of the present application. Of course, these 10 embodiments are only a part of the many variations of the present application, not all of them.

[0060] The 10 embodiments and 11 comparative examples respectively provide a high-grade non-oriented silicon steel, wherein the chemical composition of the steel comprises the contents of Si, Al, Mn, and Sn as shown in Table 1. 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.

[0061] Table 1

[0062] The production methods of the high-grade non-oriented silicon steels in 10 embodiments and 11 comparative examples are specifically described as follows.

[0063] (1) Steelmaking process Steelmaking is carried out in sequence using KR desulfurization, converter smelting, and RH refining according to the chemical composition design scheme shown in Table 1.

[0064] (2) Continuous casting process The molten steel obtained by smelting is prepared into continuous casting billets with a thickness of 200-250 mm using continuous casting equipment. During continuous casting, electromagnetic stirring is adopted with a frequency of ≥6 Hz, and the equiaxed grain ratio of the continuous casting billets is measured to be ≥50%.

[0065] (3) Hot rolling process After the continuous casting billet obtained in the continuous casting process is heated, it first undergoes multiple rough rolling passes to be rolled into an intermediate billet with a thickness of 35~40mm, and then undergoes multiple finish rolling passes to be rolled into a hot-rolled strip with a thickness of 2.00~2.70mm. After laminar cooling, it is coiled into a hot-rolled coil.

[0066] The heating temperature, heating time, start rolling temperature of rough rolling, final rolling temperature of finish rolling, and coiling temperature of each embodiment and comparative example are shown in Table 2.

[0067] Table 2

[0068] (4) Pickling process The hot-rolled strip is pickled with an acid solution to remove the oxide scale on its surface. The acid solution is selected from one of 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.

[0069] (5) Cold rolling process The pickled hot-rolled strip is cold-rolled at room temperature using a single-stand multi-pass rolling process or a tandem rolling mill to produce the cold-rolled strip. The total cold-rolling reduction is controlled to be ≥70%. The thickness of the cold-rolled strip is shown in Table 3.

[0070] (6) Annealing process The cold-rolled strip is subjected to continuous recrystallization annealing in an annealing furnace. The protective atmosphere adopts N2+H2 mixed gas or pure N2, and the O content in the annealing furnace is controlled to be ≤20ppm; if N2+H2 mixed gas is used, the H2 content is controlled to be ≤60%.

[0071] During the annealing furnace heating process, 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 ≥ the Curie temperature Tc, the heating rate V2 is shown in Table 3. After the temperature in the annealing furnace reaches the target temperature, the temperature is maintained, and the target temperature and holding time are shown in Table 3. The Curie temperature Tc is 720-740°C.

[0072] (7) Coating process An insulating coating is evenly coated on the upper and lower surfaces of the annealed strip to obtain high-grade non-oriented silicon steel.

[0073] Among them, in Comparative Example 10, the final rolling temperature of the hot rolling process was too low, resulting in serious hot rolling edge cracks and the inability 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, causing the product to fall into the defective range, and therefore production was no longer continued.

[0074] According to GB / T 3655 standard, the magnetic properties of the high-grade non-oriented silicon steel products obtained in Examples 1 to 10 and Comparative Examples 1 to 9 were tested to obtain their iron loss P 1.5 / 50 and magnetic induction intensity B 50 The data are shown in Table 3.

[0075] Table 3

[0076] In Comparative Examples 1 to 9, there are cases where the chemical element content or process parameters do not meet the requirements of this application, and the magnetic induction intensity B of the silicon steel product finally obtained is 50 It cannot meet the use requirements of high-grade non-oriented silicon steel.

[0077] The high-grade non-oriented silicon steel obtained by the normalization-free production method of Examples 1 to 10 according to one embodiment of the present application has excellent magnetic properties. Not only does it eliminate normalization, but it also has good rollability and can be produced stably, which greatly saves costs and improves product yield.

[0078] It should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation method can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0079] The detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A normalization-free production method for high-grade non-oriented silicon steel, characterized in that: The chemical composition of the non-oriented silicon steel includes, by mass percentage, 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%, and the remainder is Fe and unavoidable impurities; The production method includes the following steps: steelmaking, continuous casting, hot rolling, pickling, cold rolling, annealing and coating; In the hot rolling process, the continuous casting billet is sequentially heated, rough rolled, and finish rolled to obtain hot-rolled steel strip; In the annealing process, the cold-rolled steel strip is subjected to continuous recrystallization annealing in an annealing furnace, and the oxygen content in the annealing furnace is controlled to be ≤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°C / 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°C / s; after the temperature in the annealing furnace reaches the target temperature, the target temperature is kept at 950-1020°C for 20-100 seconds.

2. The normalization-free production method for high-grade non-oriented silicon steel according to claim 1, characterized in that: V1≥866.6-9366×[Sn]+29274×[Sn] 2 , where [Sn] is the percentage value of Sn content in non-oriented silicon steel.

3. The normalization-free production method for high-grade non-oriented silicon steel according to claim 1, characterized in that: The Curie temperature Tc is 720~740℃.

4. The normalization-free production method for high-grade non-oriented silicon steel according to claim 1, characterized in that: In the annealing process, the protective atmosphere of the annealing furnace is N2+H2 mixed gas or pure N2, and the content of H2 in the N2+H2 mixed gas is ≤60%.

5. The normalization-free production method of high-grade non-oriented silicon steel according to claim 1, characterized in that: In the continuous casting process, electromagnetic stirring is adopted, the frequency of the electromagnetic stirring is ≥6 Hz, and the proportion of equiaxed grains in the continuous casting billet is ≥50%.

6. The normalization-free production method of high-grade non-oriented silicon steel according to claim 1, characterized in that: In the hot rolling process, the heating temperature is 1080-1130° C., the heating time is ≥150 min, the starting temperature of rough rolling is ≥1000° C., the final rolling temperature of finishing rolling is ≥850° C., and the coiling temperature is ≤650° C.

7. The normalization-free production method of high-grade non-oriented silicon steel according to claim 1, characterized in that: In the pickling process, the hot-rolled strip is pickled with an acid solution to remove the oxide scale on its surface. The acid solution is selected from one of 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.

8. The normalization-free production method of high-grade non-oriented silicon steel according to claim 1, characterized in that: In the cold rolling process, the pickled hot-rolled strip is cold rolled at room temperature. The cold rolling is performed by a single stand for multiple passes or by a continuous rolling mill, and the total reduction ratio is controlled to be ≥70%.

9. A high-grade non-oriented silicon steel, characterized in that: The product is prepared by the normalization-free production method according to any one of claims 1 to 8.

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

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