Ultrathin oriented silicon steel and preparation method thereof

Abstract

The invention discloses ultrathin oriented silicon steel and a preparation method thereof.The method comprises the steps that materials are selected, specifically, a steel billet is selected, and the steel billet comprises, by mass, 0.040%-0.055% of C, 2.8%-3.3% of Si, 0.050%-1.0% of Mn, 0.020%-0.030% of S, 0.020%-0.030% of Al, 0.0020%-0.0055% of N, 0.40%-0.50% of Cu, 0.002%-0.005% of Bi and the balance Fe and inevitable impurities; sequentially rolling the steel billet through a hot rolling process and a cold rolling process with the reduction rate being smaller than or equal to 93% to obtain a cold-rolled steel billet; and carrying out annealing post-treatment on the cold-rolled steel billet to obtain a finished product. According to the ultrathin oriented silicon steel and the preparation method thereof, the magnetic induction intensity of the oriented silicon steel can be improved, and the loss of a grid-connected transformer at the frequency of 50-400 Hz is effectively reduced.

Description

Technical Field

[0001] The invention relates to the technical field of oriented silicon steel rolling, and in particular to ultra-thin oriented silicon steel and a preparation method thereof. Background Art

[0002] In order to meet the development needs of new energy efficient, long-distance transmission and grid-connected technology, new energy grid-connected equipment is developing in the direction of medium frequency, large capacity and compactness. Although increasing the frequency can reduce the size and weight of the transformer, it will also significantly increase the transformer loss and temperature rise. In addition, the insulation material also needs to withstand a higher level of voltage, which puts higher requirements on the performance of the insulation material. If the frequency is increased to high frequency (≥1kHz), there will be problems such as core design, heat dissipation, and insulation, and it is necessary to match high-cost power devices such as silicon carbide, making it difficult to increase the transformer frequency and single-cell capacity. Taking all factors into consideration, the current 50-400Hz is a suitable frequency range for grid-connected transformers for new energy such as wind power to increase capacity, reduce costs, and meet the needs of long-distance large-capacity transmission and grid-connected engineering applications of new energy.

[0003] Oriented silicon steel refers to steel with highly concentrated {110} <001> The Si-Fe soft magnetic material with Goss texture is obtained by secondary recrystallization during high temperature annealing, thus obtaining a perfect single {110} <001> Texture, easy magnetization performance under directional magnetic field. Oriented silicon steel is mainly used to make iron cores of transformers, generators, ballasts, relays, electromagnetic switches and other devices, and is one of the most important functional materials for the development of the power industry.

[0004] At present, the transformers for new energy grid-connected use mostly adopt conventional oriented silicon steel with a thickness of ≥0.18mm, which has high loss in the frequency range of 50-400Hz. As a result, the wind power grid-connected transformers currently developed have a series of problems such as high loss, high temperature rise, large size and high cost, which limits the technological development of wind power grid-connected equipment. Therefore, it is necessary to further reduce the loss of oriented silicon steel under 50-400Hz conditions.

[0005] Reducing the thickness of oriented silicon steel to make ultra-thin oriented silicon steel (for example, oriented silicon steel with a thickness of ≤0.18mm) can significantly reduce iron loss and improve its comprehensive performance, but thickness reduction will also bring a series of technical difficulties. In the production process of oriented silicon steel, the formation of Goss texture is mainly through cold rolling and annealing. During the cold rolling process, the grains are elongated and form a certain orientation. Then, through annealing, these oriented grains will recrystallize to form grains with specific orientation. The formation mechanism of Goss texture mainly includes primary recrystallization and secondary recrystallization processes. When the steel is thinned, the driving force of the surface energy on the growth of secondary grains increases, and the decomposition and diffusion of inhibitors are intensified during high-temperature annealing. When secondary recrystallization occurs, the number and distribution of inhibitors are lacking, resulting in a decrease in their inhibitory ability, and secondary recrystallization is not easy to complete, and the magnetic properties and stability are reduced.

[0006] Therefore, it is necessary to adopt effective measures such as enhanced inhibition to develop a complete secondary recrystallization to compensate for the problem of reduced magnetic properties of oriented silicon steel during the thickness thinning process. Summary of the invention

[0007] The purpose of the present invention is to solve the technical problem that in the thinning process of preparing ultra-thin oriented silicon steel, the magnetic properties are reduced because the inhibitory force of the inhibitor is reduced and it is difficult to develop a complete secondary recrystallization.

[0008] The purpose of the present invention is to adopt the following technical solutions to achieve:

[0009] The present invention provides a method for preparing ultra-thin oriented silicon steel, the preparation method comprising:

[0010] Material selection: selecting a steel billet, wherein the chemical composition of the steel billet comprises, by mass percentage, C: 0.040-0.055%, Si: 2.8-3.3%, Mn: 0.050-1.0%, S: 0.020-0.030%, Al: 0.020-0.030%, N: 0.0020-0.0055%, Cu: 0.40-0.50%, Bi: 0.002-0.005%, and the balance is Fe and unavoidable impurities;

[0011] The steel billet is sequentially subjected to a hot rolling process and a cold rolling process with a first reduction ratio of ≤93% to obtain a cold-rolled steel billet;

[0012] The cold-rolled steel billet is subjected to an annealing post-treatment process to obtain an ultra-thin oriented silicon steel product.

[0013] Preferably, the hot rolling process adopts segmented hot rolling, which includes: sequentially rolling the steel billet through a first hot rolling pass and a second hot rolling pass, controlling the thickness of the steel billet after the first hot rolling pass to be 2.0-2.3 mm, and controlling the thickness of the steel billet after the second hot rolling pass to be 1.4-1.8 mm.

[0014] Preferably, the thickness of the finished ultra-thin oriented silicon steel product is 0.1-0.15 mm.

[0015] Preferably, the first hot rolling is high temperature hot rolling, the initial temperature of the high temperature hot rolling is 1150-1250°C, and the final rolling temperature is 950-1050°C.

[0016] Preferably, the second hot rolling adopts low temperature hot rolling, the initial temperature of the low temperature hot rolling is 700-800°C, and the final rolling temperature is 550-650°C.

[0017] Preferably, the reduction ratio of the second hot rolling is 20-30%.

[0018] Preferably, the cold rolling rate is 100-250 m / min.

[0019] Preferably, after the hot rolling process and before the cold rolling process, the process further includes:

[0020] The steel billet obtained after the hot rolling process is subjected to intermediate annealing treatment at a temperature of 1000-1150° C. for 2-5 minutes.

[0021] Preferably, the post-annealing treatment process is carried out under a protective atmosphere, and the protective atmosphere is a mixed gas composed of nitrogen and hydrogen in a volume ratio of 9-10:1.

[0022] Based on the same inventive concept, the present invention also provides an ultra-thin oriented silicon steel prepared by the preparation method as described above.

[0023] Preferably, the chemical composition of the ultra-thin oriented silicon steel comprises, by mass percentage, Si: 2.8-3.3%, Mn: 0.050-1.0%, Cu: 0.40-0.50%, Al≤0.0005%, Bi≤0.0001%, C≤0.0002%, N≤0.0002%, S≤0.0002%, and the remainder is Fe and unavoidable impurities.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] On the first aspect, the embodiments of the present invention optimize the chemical composition design of ultra-thin oriented silicon steel to enhance the inhibitory effect of the inhibitor, thereby enhancing the stability of the inhibitor in processes such as hot rolling, cold rolling, and annealing, giving full play to the inhibitory effect, inhibiting the normal growth of primary crystallized grains, and promoting the secondary recrystallization behavior of Goss oriented grains to fully occur, so that the final product has excellent magnetic properties and low iron loss.

[0026] In the second aspect, the ultra-thin oriented silicon steel with a thickness in the range of 0.1-0.15 mm prepared by the preparation method of the present invention has a loss P of 0.1-0.15 mm at an operating frequency of 50 Hz. 1.7 / 50 ≤0.55W / kg, loss P at medium frequency 200Hz 1.5 / 200 ≤3.5W / kg, loss P at medium frequency 400Hz 1.0 / 400 ≤4.7W / kg, magnetic induction B800≥1.90T, that is, it has lower loss at a frequency of 50-400Hz and has excellent magnetic properties, which can meet the application of finished silicon steel in 50Hz industrial frequency and 100-400Hz medium frequency equipment, and is suitable for equipment such as wind power and other new energy grid-connected transformers, meeting the application needs of new energy long-distance and large-capacity transmission and grid-connected engineering; and, the preparation method of the present invention only adopts one cold rolling process, compared with the traditional preparation method of ultra-thin oriented silicon steel using multiple cold rolling processes such as secondary and tertiary cold rolling processes, the process flow is short, the energy consumption is low, the production efficiency is high, the cost is low, and the needs of enterprises for high-efficiency production are met. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is an electron microscope scanning image of the secondary recrystallization of the ultra-thin oriented silicon steel obtained in Example 1 of the present invention;

[0028] Figure 2 This is an electron microscope scanning image of the secondary recrystallization of the ultra-thin oriented silicon steel obtained in Example 2 of the present invention;

[0029] Figure 3 This is an electron microscope scanning image of the secondary recrystallization of the ultra-thin oriented silicon steel obtained in Example 3 of the present invention;

[0030] Figure 4 This is an electron microscope scanning image of the secondary recrystallization of the ultra-thin oriented silicon steel obtained in Example 4 of the present invention;

[0031] Figure 5 This is an electron microscope scanning image of the secondary recrystallization of the ultra-thin oriented silicon steel obtained in Example 5 of the present invention;

[0032] Figure 6 This is an electron microscope scanning image of the secondary recrystallization of the ultra-thin oriented silicon steel obtained in Example 6 of the present invention;

[0033] Figure 7 This is an electron microscope scanning image of the secondary recrystallization of the ultra-thin oriented silicon steel obtained in Comparative Example 1 of the present invention;

[0034] Figure 8 This is an electron microscope scanning image of the secondary recrystallization of the ultra-thin oriented silicon steel obtained in Comparative Example 2 of the present invention;

[0035] Fig. 9 This is an electron microscope scanning image of the secondary recrystallization of the ultra-thin oriented silicon steel prepared in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0036] Below in conjunction with the drawings and Examples, the specific embodiments of the present invention are described in further detail. The following examples are used to illustrate the present invention, but are not used to limit the scope of the present invention. Any product identical or similar to the present invention obtained by combining the features of the present invention and other prior arts under the enlightenment of the present invention, all falls within the protection scope of the present invention. The specific experimental steps or conditions not indicated in the embodiments can be carried out according to the operation or conditions of the conventional experimental steps described in the documents in this area. The reagents used or the instruments not indicated by the manufacturer are all conventional reagent products that can be obtained by commercial purchase.

[0037] The present invention provides a method for preparing ultra-thin oriented silicon steel, comprising the following steps:

[0038] S101: Material selection: selecting a steel billet, wherein the chemical composition of the steel billet comprises, by mass percentage, C: 0.040-0.055%, Si: 2.8-3.3%, Mn: 0.050-1.0%, S: 0.020-0.030%, Al: 0.020-0.030%, N: 0.0020-0.0055%, Cu: 0.40-0.50%, Bi: 0.002-0.005%, and the balance is Fe and unavoidable impurities;

[0039] S102: rolling the steel billet in sequence through a hot rolling process and a cold rolling process with a primary reduction ratio of ≤93% to obtain a cold-rolled steel billet;

[0040] S103: subjecting the cold-rolled steel billet to an annealing post-treatment process to obtain an ultra-thin oriented silicon steel product.

[0041] As an important electrical material, oriented silicon steel is widely used in the fields of electricity, electronics, etc. In order to obtain excellent magnetic properties and processing performance, inhibitors need to be added during the production process. On the one hand, the inhibitors hinder the grain boundary migration of the primary recrystallization grains, inhibit the normal growth of the primary grains, and cause secondary recrystallization behavior, thereby improving the orientation performance and making the crystal structure in the silicon steel more regular and orderly. On the other hand, it can effectively slow down the growth rate of the grains and obtain a fine and uniform grain structure. This crystal structure and grain structure are conducive to improving the magnetic permeability of the material and reducing iron loss, so that the oriented silicon steel shows better performance in the application.

[0042] In the process of preparing ultra-thin oriented silicon steel, a large reduction rate is required for rolling, which will increase the driving force of surface energy on the growth of secondary grains, and the inhibitors will decompose and diffuse more during cold rolling, high temperature annealing and other stages. When secondary recrystallization occurs, the amount of inhibitors precipitated is small and diffusely distributed, resulting in a decrease in the inhibitory effect, making it difficult to perfect the secondary recrystallization, and the magnetic properties of the final product are poor. Therefore, it is necessary to use inhibitors with stronger inhibitory effects to reduce the impact of thickness reduction on the performance of oriented silicon steel under large reduction rates.

[0043] The present invention optimizes the chemical composition design of ultra-thin oriented silicon steel to enhance the inhibitory effect of the inhibitor, thereby enhancing the stability of the inhibitor in the processes of hot rolling, cold rolling, annealing, etc., giving full play to the inhibitory effect, inhibiting the normal growth of the primary crystallization grains, and promoting the secondary recrystallization behavior of the Goss oriented grains to fully occur, so that the final product has excellent magnetic properties and low iron loss. The design principles of each chemical element are specifically described as follows:

[0044] Si: 2.8% or more and 3.3% or less

[0045] Silicon is a basic element in oriented silicon steel. During the rolling process, silicon interacts with other elements such as iron to form a specific grain orientation structure, which can effectively improve the magnetic permeability and reduce hysteresis loss and eddy current loss. When the silicon content in oriented silicon steel is lower than 2.8%, the above-mentioned effects cannot be effectively exerted. However, when the silicon content is higher than 3.3%, the recrystallization structure and inhibitors will become unstable, resulting in imperfect secondary recrystallization, and causing the magnetic saturation magnetic field intensity of the oriented silicon steel to decrease, thereby affecting its magnetic permeability. In addition, excessive silicon content will also lead to increased hardness and increase the difficulty of rolling. Therefore, in the oriented silicon steel in the embodiment of the present invention, Si The mass percentage of the element is controlled within the range of 2.8-3.3%.

[0046] C: 0.040% or more and 0.055% or less

[0047] Carbon is one of the elements that affect the strength and toughness of steel. With the increase of carbon content, the strength of steel will be significantly improved, but the brittleness will gradually increase, resulting in a decrease in toughness. A higher carbon content may also cause magnetic aging, so the carbon content in steel should not be too low or too high. At high temperatures, carbon is also an element that stabilizes austenite. During the hot rolling process, a certain carbon content must be maintained to ensure uniform crystal structure. When the content is lower than 0.040%, the proportion of γ phase obtained during the hot rolling process is low, which is not conducive to phase change rolling to form a uniform Goss texture. However, if the content is higher than 0.055%, coarse carbides will appear, which are difficult to remove in the decarburization process, reducing the decarburization efficiency. Therefore, the mass percentage of the C element in the oriented silicon steel of the embodiment of the present invention is controlled within the range of 0.040-0.055%.

[0048] Mn: 0.050% or more and 1.000% or less

[0049] Manganese is an important component element for forming the inhibitor MnS. This inhibitor helps to control the growth and orientation of grains in the production process of oriented silicon steel. The appropriate manganese content can make the grains grow and orient in a way that is conducive to obtaining good magnetic properties during hot rolling, cold rolling, annealing and other processes, thereby improving the magnetic permeability. In addition, manganese can also increase the resistivity and reduce eddy current losses. However, the manganese content in the steel should not be too low or too high. When the manganese content is lower than 0.050%, it will lead to insufficient formation of inhibitors, affecting the control effect of grain orientation, and then increase the iron loss and reduce the magnetic induction of the oriented silicon steel. When the manganese content is higher than 1%, it is easy to form a mixed dual-phase structure of α and γ, introduce too many impurity phases, cause secondary recrystallization instability, and thus affect the stability of its magnetic properties. Therefore, the mass percentage of the Mn element in the oriented silicon steel of the embodiment of the present invention is controlled within the range of 0.050-1.000%.

[0050] S: 0.020% or more and 0.030% or less

[0051] Sulfur is the formation of uniform and fine MnS and Cu 2 S and other inclusions have good thermal stability, which is beneficial to inhibit the grain growth rate during the primary crystallization process and promote secondary recrystallization. The sulfur content needs to match the copper and manganese content to precipitate MnS and Cu 2 S and other inhibitor particles inhibit the normal growth of primary grains, making the {110} <001> The primary grains in one orientation can swallow up the surrounding primary grains in other orientations during high-temperature annealing and grow abnormally, that is, secondary recrystallization occurs.

[0052] However, during the high-temperature heating and thinning rolling process of steel with a large reduction rate, as the driving force of the external surface energy increases, these fine inclusions will accelerate decomposition and diffusion during high-temperature annealing, reducing the inhibitory effect during the crystallization process. Therefore, it is necessary to provide appropriate sulfur, copper and manganese content to precipitate sufficient inhibitor particles, strengthen the inhibitory effect, and develop a perfect secondary recrystallization. If the sulfur content in the steel is lower than 0.020%, the inhibitor particles precipitated are insufficient and will be quickly decomposed and diffused, which is not conducive to the improvement of the secondary recrystallization structure, the magnetic induction decreases, and the magnetic properties fluctuate greatly. After completing the primary crystallization and secondary crystallization, high-temperature annealing is required to decompose the sulfide inclusions and remove the sulfur element in the product. If the sulfur content is too high, the cost of high-temperature annealing to purify the sulfur element will increase. Therefore, the mass percentage of the S element in the oriented silicon steel of the embodiment of the present invention is controlled within the range of 0.020-0.030%.

[0053] Al: 0.020% to 0.030% inclusive, N: 0.0020% to 0.0055% inclusive

[0054] Aluminum mainly forms AlN particles with nitrogen, which have an inhibitory effect on MnS and Cu. 2 S and other elements jointly inhibit the normal growth of primary grains and promote secondary recrystallization. Within the appropriate range of aluminum and nitrogen content, a small and uniform primary grain size can be obtained, a large amount of AlN particles are precipitated, and the inhibitory effect is strong. If the aluminum content in the steel is lower than 0.020% or the nitrogen content is lower than 0.0020%, the amount of AlN particles precipitated is small, the directional inhibition effect is weak, the secondary recrystallization is imperfect, and even no secondary recrystallization can occur. If the aluminum content in the steel is higher than 0.035% or the nitrogen content is higher than 0.0055%, at high temperatures, the AlN particles will be coarsened, the density and volume fraction of the precipitated phase will be reduced, and the amount of precipitation will be sharply reduced, resulting in a decrease in the inhibitory force of the precipitated phase and a decrease in magnetic properties. Therefore, in the oriented silicon steel of the embodiment of the present invention, the mass percentage of the Al element is controlled within the range of 0.020-0.030%, and the mass percentage of the N element is controlled within the range of 0.0020-0.0055%.

[0055] Cu: 0.40% or more and 0.50% or less

[0056] Copper is similar to manganese, and mainly forms Cu with sulfur, which has an inhibitory effect. 2 S and other copper-containing inhibitors. Cu 2 S has lower solid solution temperature and precipitation temperature than Cu 2 S, as the main inhibitor, is beneficial to reduce the heating temperature of steel. 2 S particles can also effectively pin the grain boundaries and enhance the suppression effect of primary grains. 2 S begins to precipitate in large quantities during the hot rolling process. The segregation degree in thin steel is less than that in thick steel. The low heating temperature and short heating time of thin steel are helpful to control the coarsening and growth of precipitates, so that a large number of precipitates are precipitated in the form of fine and dispersed distribution, which is conducive to the smooth secondary recrystallization. When the copper content in steel is lower than 0.40%, coarse MnS+AlN composite inclusions are easily precipitated first, and the solid solution temperature of AlN and MnS is higher than that of Cu. 2 S, cannot effectively play the role of Cu 2 When the copper content in the steel is higher than 0.50%, the copper-containing phase will coarsen under the high temperature of hot rolling, resulting in a decrease in the inhibitory force of the precipitated phase, which is not conducive to the improvement of the secondary recrystallization structure, the magnetic properties will decrease, and the manufacturing cost will increase. Therefore, the mass percentage of the Cu element in the oriented silicon steel of the embodiment of the present invention is controlled within the range of 0.40-0.50%.

[0057] Bi: 0.002% or more and 0.005% or less

[0058] Bismuth is a grain boundary segregation element and has the function of auxiliary inhibitor. 2Inhibitor particles such as S exist in a mutually embedded or symbiotic form, which can pin the grain boundaries and prevent the grains from growing, thereby reducing the primary grain size and making the grains finer and more dispersed, which is beneficial to the improvement of the secondary recrystallization structure and the improvement of the magnetic properties of oriented silicon steel. When the bismuth content in the steel is lower than 0.002%, the above-mentioned inhibitory effect cannot be effectively exerted, and when the bismuth content in the steel is higher than 0.005%, it will affect the decarburization efficiency and increase the manufacturing cost. Therefore, the mass percentage of the Bi element in the oriented silicon steel of the embodiment of the present invention is controlled within the range of 0.002-0.005%.

[0059] In some embodiments, in step S102, the hot rolling process adopts segmented hot rolling to gradually thin the steel billet; the segmented hot rolling includes: sequentially rolling the steel billet with a first hot rolling pass and a second hot rolling pass, controlling the thickness of the steel billet after the first hot rolling pass to be 2.0-2.3 mm, and controlling the thickness of the steel billet after the second hot rolling pass to be 1.4-1.8 mm.

[0060] The first hot rolling can be performed at high temperature to control the thickness to 2.0-2.3 mm, and the second hot rolling can be performed at low temperature to further control the final hot rolling thickness to 1.4-1.8 mm.

[0061] The use of segmented step-by-step thinning can, on the one hand, reasonably control the force on the billet and avoid plastic deformation caused by excessive stress; on the other hand, since the thinner the billet is, the greater the influence of temperature and reduction rate on the crystal structure, segmented hot rolling can first use high-temperature hot rolling, and then use low-temperature hot rolling after thinning to a certain thickness, thereby fully reducing the influence on the hot-rolled structure.

[0062] The present invention finds that if the thickness of the high temperature hot rolling stage is greater than 2.3mm and the thickness of the low temperature hot rolling stage is greater than 1.8mm, it will have an adverse effect on the secondary recrystallization, and the phenomenon of no secondary recrystallization occurs in some areas. Therefore, the embodiment of the present invention preferably controls the final thickness of the high temperature hot rolling to 2.0-2.3mm, and the final thickness after the low temperature hot rolling to 1.4-1.8mm.

[0063] Specifically, in some embodiments, the initial temperature of high-temperature hot rolling is 1150-1250°C, and the final rolling temperature is 950-1050°C; the initial temperature of low-temperature hot rolling is 700-800°C, and the final rolling temperature is 550-650°C.

[0064] The high-temperature hot-rolled steel billet has low deformation resistance, and shear deformation makes it easier to obtain sufficient initial Goss texture; the low-temperature hot rolling temperature is lower, and the reduction rate can be controlled within the range of 20%-30%, and the cold rolling rate can be controlled within the range of 100-250m / min. The lower temperature and reduction rate reduce the deformation of the steel billet and reduce the impact on the high-temperature hot rolling structure.

[0065] In some embodiments, in step S103, the post-annealing treatment process is performed under a protective atmosphere, and the protective atmosphere is a mixed gas composed of nitrogen and hydrogen in a volume ratio of 9-10:1.

[0066] Annealing post-treatment process usually includes decarburization, nitriding, high temperature annealing and other processes to remove impurities such as carbon, nitrogen, sulfur and other elements that affect the magnetic properties of the product. 2 The large proportion can delay the ripening rate of high inhibitors, improve the inhibition force, and promote the smooth secondary recrystallization of Goss-oriented grains.

[0067] In some embodiments, after the hot rolling process and before the cold rolling process, the process further includes: subjecting the steel billet obtained after the hot rolling process to an intermediate annealing treatment at a temperature of 1000-1150° C. for 2-5 minutes.

[0068] In some embodiments, after the above-mentioned hot rolling, cold rolling, and annealing post-treatment processes, the thickness of the ultra-thin oriented silicon steel product is 0.1-0.15mm. 0.10-0.15mm thin-gauge oriented silicon steel has excellent magnetic properties and low loss in the range of 50-400Hz, and can be used for industrial frequency 50Hz electrical equipment, as well as 100-400Hz medium frequency electrical equipment. It can be applied to wind power grid-connected transformers to reduce loss, cost and other problems, and expand the technical development of wind power grid-connected equipment; and the preparation method of the present invention only uses one cold rolling process, compared with the traditional preparation method of ultra-thin oriented silicon steel using multiple cold rolling processes such as secondary and tertiary cold rolling processes, the process flow is short, the energy consumption is low, the production efficiency is high, the cost is low, and the needs of enterprises for high-efficiency production are met.

[0069] Based on the same inventive concept, an embodiment of the present invention further provides an ultra-thin oriented silicon steel, which is prepared by the above-mentioned method for preparing ultra-thin oriented silicon steel.

[0070] In some preferred embodiments, the chemical composition of the finished ultra-thin oriented silicon steel comprises, by mass percentage: Si: 2.8-3.3%, Mn: 0.050-1.0%, Cu: 0.40-0.50%, Al≤0.0005%, Bi≤0.0001%, C≤0.0002%, N≤0.0002%, S≤0.0002%, and the balance is Fe and unavoidable impurities.

[0071] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to explain the present invention, and are not used to limit the present invention.

[0072] Example

[0073] The chemical compositions of the steel billets for preparing ultra-thin oriented silicon steel in Examples 1-20 of the present invention and Comparative Examples 1-16 are according to the parameters in Tables 1 and 2.

[0074] Table 1: Chemical composition of steel billets for preparing ultra-thin oriented silicon steel in Examples 1-20 of the present invention

[0075]

[0076] Table 2: Chemical composition of steel billets for preparing ultra-thin oriented silicon steel in Comparative Examples 1-16

[0077]

[0078]

[0079] Embodiment 21

[0080] The method for preparing the ultra-thin oriented silicon steel according to the embodiment of the present invention specifically comprises the following steps:

[0081] 1) Material selection: Select a steel billet having the chemical composition of Example 1 above;

[0082] 2) The steel billet is subjected to segmented hot rolling: firstly, high temperature hot rolling is adopted, the initial temperature of high temperature hot rolling is 1250°C, the final rolling temperature is 1050°C, and the thickness of the oriented silicon steel after hot rolling is controlled to be 2.3mm; after high temperature hot rolling, the steel billet is cooled to 800°C for low temperature hot rolling, the final rolling temperature is 650°C, and the thickness of the oriented silicon steel after hot rolling is controlled to be 1.8mm;

[0083] 3) Intermediate annealing: The hot-rolled steel billet is annealed in N 2 Annealing under protective atmosphere, annealing temperature is 1150℃, annealing time is 5min;

[0084] 4) Cold rolling: the steel billet after intermediate annealing is subjected to a large reduction rate cold rolling, the reduction rate is ≤93%, the rolling rate is 250m / min, the rolling passes are 4 times, and the thickness after rolling is 0.1-0.15mm;

[0085] 5) Annealing post-treatment: The cold rolled steel billet is heated to 90% N 2 +10%H 2 After decarburization, nitriding and high temperature annealing under a protective atmosphere, the finished ultra-thin oriented silicon steel is obtained.

[0086] Embodiment 22

[0087] The method for preparing ultra-thin oriented silicon steel provided in this embodiment is the same as that in embodiment 21, except that:

[0088] In step 1), the chemical composition of the steel billet includes, by mass percentage, C: 0.055%, Si: 2.8%, Mn: 0.050%, S: 0.020%, Al: 0.030%, N: 0.0055%, Cu: 0.40%, Bi: 0.005%, and the remainder is Fe and unavoidable impurities.

[0089] In step 2), the initial temperature of high-temperature hot rolling is 1150°C, the final rolling temperature is 950°C, and the thickness of the oriented silicon steel after hot rolling is controlled to be 2.0 mm; after high-temperature hot rolling, the steel is cooled to 700°C for low-temperature hot rolling, the final rolling temperature is 550°C, the reduction rate is controlled within the range of 20-30%, and the thickness of the oriented silicon steel after hot rolling is 1.4 mm.

[0090] In step 3), the intermediate annealing temperature is 1000° C. and the annealing time is 2 min.

[0091] In step 4), the cold rolling reduction ratio is ≤93%, the rolling rate is 100 m / min, and the rolling passes are 6 times; the thickness after rolling is 0.1-0.15 mm.

[0092] Embodiment 23

[0093] The method for preparing ultra-thin oriented silicon steel provided in this embodiment is the same as that in embodiment 21, except that:

[0094] In step 1), the chemical composition of the steel billet includes, by mass percentage, C: 0.050%, Si: 3.0%, Mn: 0.080%, S: 0.025%, Al: 0.027%, N: 0.0035%, Cu: 0.45%, Bi: 0.003%, and the remainder is Fe and unavoidable impurities.

[0095] In step 2), the initial temperature of high-temperature hot rolling is 1180°C, the final rolling temperature is 1040°C, and the thickness of the oriented silicon steel after hot rolling is controlled to be 2.0 mm; after high-temperature hot rolling, the steel is cooled to 750°C for low-temperature hot rolling, and the final rolling temperature is 580°C, and the thickness of the oriented silicon steel after hot rolling is controlled to be 1.5 mm.

[0096] In step 3), the intermediate annealing temperature is 1050° C. and the annealing time is 3 min.

[0097] In step 4), the cold rolling reduction ratio is ≤93%, the rolling speed is 180 m / min, and the rolling passes are 6 times; the thickness after rolling is 0.1-0.15 mm.

[0098] Embodiment 24

[0099] The method for preparing ultra-thin oriented silicon steel provided in this embodiment is the same as that in embodiment 21, except that:

[0100] In step 1), the chemical composition of the steel billet includes, by mass percentage, C: 0.049%, Si: 2.9%, Mn: 0.059%, S: 0.026%, Al: 0.025%, N: 0.0049%, Cu: 0.41%, Bi: 0.004%, and the remainder is Fe and unavoidable impurities.

[0101] In step 2), the initial temperature of high-temperature hot rolling is 1160°C, the final rolling temperature is 960°C, and the thickness of the oriented silicon steel after hot rolling is controlled to be 2.0 mm; after high-temperature hot rolling, the steel is cooled to 800°C for low-temperature hot rolling, the final rolling temperature is 630°C, and the thickness of the oriented silicon steel after hot rolling is controlled to be 1.6 mm.

[0102] In step 3), the intermediate annealing temperature is 1100° C. and the annealing time is 3 min.

[0103] In step 4), the cold rolling reduction ratio is ≤93%, the rolling rate is 140 m / min, and the rolling passes are 5 times; the thickness after rolling is 0.1-0.15 mm.

[0104] Embodiment 25

[0105] The method for preparing ultra-thin oriented silicon steel provided in this embodiment is the same as that in embodiment 21, except that:

[0106] In step 1), the chemical composition of the steel billet includes, by mass percentage, C: 0.047%, Si: 3.0%, Mn: 0.053%, S: 0.027%, Al: 0.024%, N: 0.0042%, Cu: 0.43%, Bi: 0.0035%, and the remainder is Fe and unavoidable impurities.

[0107] In step 2), the initial temperature of high-temperature hot rolling is 1170°C, the final rolling temperature is 985°C, and the thickness of the oriented silicon steel after hot rolling is controlled to be 2.1 mm; after high-temperature hot rolling, the steel is cooled to 730°C for low-temperature hot rolling, and the final rolling temperature is 630°C, and the thickness of the oriented silicon steel after hot rolling is controlled to be 1.6 mm.

[0108] In step 3), the intermediate annealing temperature is 1080° C. and the annealing time is 4 minutes.

[0109] In step 4), the cold rolling reduction ratio is ≤93%, the rolling speed is 180 m / min, and the rolling passes are 5 times; the thickness after rolling is 0.1-0.15 mm.

[0110] Embodiment 26

[0111] The method for preparing ultra-thin oriented silicon steel provided in this embodiment is the same as that in embodiment 21, except that:

[0112] In step 1), the chemical composition of the steel billet includes, by mass percentage, C: 0.051%, Si: 2.9%, Mn: 0.084%, S: 0.027%, Al: 0.028%, N: 0.0036%, Cu: 0.43%, Bi: 0.0034%, and the remainder is Fe and unavoidable impurities.

[0113] In step 2), the initial temperature of high-temperature hot rolling is 1230°C, the final rolling temperature is 1035°C, and the thickness of the oriented silicon steel after hot rolling is controlled to be 2.2 mm; after high-temperature hot rolling, the steel is cooled to 780°C for low-temperature hot rolling, and the final rolling temperature is 630°C, and the thickness of the oriented silicon steel after hot rolling is controlled to be 1.7 mm.

[0114] In step 3), the intermediate annealing temperature is 1110° C. and the annealing time is 3 min.

[0115] In step 4), the cold rolling reduction ratio is ≤93%, the rolling speed is 220 m / min, and the rolling passes are 5 times; the thickness after rolling is 0.1-0.15 mm.

[0116] Comparative Example 17

[0117] The preparation method of the ultra-thin oriented silicon steel in this comparative example is the same as that in Example 21, except that the chemical composition of the steel billet comprises, by mass percentage, the following: C: 0.051%, Si: 2.9%, Mn: 0.084%, S: 0.027%, Al: 0.028%, N: 0.0036%, Cu: 0.30%, Bi: 0.001%, and the remainder is Fe and unavoidable impurities.

[0118] Comparative Example 18

[0119] The preparation method of the ultra-thin oriented silicon steel in this comparative example is the same as that in Example 21, except that the chemical composition of the steel billet comprises, by mass percentage, the following: C: 0.051%, Si: 2.9%, Mn: 0.084%, S: 0.027%, Al: 0.028%, N: 0.0036%, Cu: 0.25%, Bi: 0.0015%, and the remainder is Fe and unavoidable impurities.

[0120] Comparative Example 19

[0121] The preparation method of the ultra-thin oriented silicon steel in this comparative example is the same as that in Example 21, except that the chemical composition of the steel billet comprises, by mass percentage, the following: C: 0.051%, Si: 2.9%, Mn: 0.084%, S: 0.027%, Al: 0.028%, N: 0.0036%, Cu: 0.6%, Bi: 0.008%, and the remainder is Fe and unavoidable impurities.

[0122] Comparative Example 20

[0123] The preparation method of the ultra-thin oriented silicon steel in this comparative example is the same as that in Example 21, except that the chemical composition is mainly: C: 0.051%, Si: 2.9%, Mn: 0.084%, S: 0.027%, Al: 0.028%, N: 0.0036%, Cu: 0.8%, Bi: 0.010%, and the remainder is Fe and unavoidable impurities.

[0124] Comparative Example 21

[0125] The preparation method of the ultra-thin oriented silicon steel in this comparative example is the same as that in Example 21, except that: in the segmented hot rolling process, the thickness of the oriented silicon steel after high-temperature hot rolling is 2.5 mm, and the thickness of the oriented silicon steel after low-temperature hot rolling is 2.0 mm.

[0126] Comparative Example 22

[0127] The preparation method of the ultra-thin oriented silicon steel in this comparative example is the same as that in Example 21, except that: in the segmented hot rolling process, the thickness of the oriented silicon steel after high-temperature hot rolling is 2.8 mm, and the thickness of the oriented silicon steel after low-temperature hot rolling is 2.2 mm.

[0128] Comparative Example 23

[0129] The preparation method of the ultra-thin oriented silicon steel in this comparative example is the same as that in Example 21, except that: in the segmented hot rolling process, the thickness of the oriented silicon steel after high-temperature hot rolling is 3.0 mm, and the thickness of the oriented silicon steel after low-temperature hot rolling is 2.5 mm.

[0130] Comparative Example 24

[0131] The preparation method of the ultra-thin oriented silicon steel in this comparative example is the same as that in Example 21, except that during the cold rolling process, the cold rolling reduction rate is 95%.

[0132] Comparative Example 25

[0133] The preparation method of the ultra-thin oriented silicon steel in this comparative example is the same as that in Example 21, except that during the cold rolling process, the cold rolling reduction rate is 98%.

[0134] The preparation methods of the ultra-thin oriented silicon steels of Examples 1-20 of the present invention and Comparative Examples 1-16 have the same preparation steps and process conditions as those of Example 21 of the present invention, except for the different chemical compositions of the steel billets.

[0135] The chemical composition of the steel billets for preparing ultra-thin oriented silicon steel in Examples 27-46 of the present invention is the same as that in Example 3 of the present invention, the preparation steps are the same as those in Example 21, and the process conditions are according to the parameters in Table 3.

[0136] Table 3: Preparation process conditions of ultra-thin oriented silicon steel in Examples 27-46 of the present invention

[0137]

[0138] Performance Test:

[0139] 1. Observation of secondary recrystallization morphology by scanning electron microscope

[0140] The finished products obtained in Examples 21-26 were observed under an electron microscope to have a perfect secondary recrystallization structure (e.g. Figure 1-6 As shown), it can be seen that after the preparation process of the present invention, secondary recrystallization behavior will still occur smoothly and completely after cold rolling, annealing and other processes, generating a sharp Goss texture, so that the finished ultra-thin oriented silicon steel has excellent magnetic properties and low iron loss.

[0141] Comparative Examples 1-16 are comparative experiments on the effects of the contents of C, Si, Mn, S, Al, N, Cu, and Bi in the chemical composition of the steel billet on the secondary recrystallization structure. The morphology of the secondary recrystallization structure was observed using an electron microscope. It was found that some areas of Comparative Examples 1-16 did not experience secondary recrystallization.

[0142] The copper and bismuth content of Comparative Examples 17-20 are all outside the protection scope of the embodiments of the present invention. Figure 7 is a scanning image of the secondary recrystallization structure morphology of the oriented silicon steel obtained in Example 17 observed under an electron microscope. The scanning images of the secondary recrystallization structures of Examples 17-20 are similar to Figure 7 It can be seen from the microscope crystal structure morphology scanning that although secondary recrystallization has completely occurred, the Goss grain orientation deviation angle is large.

[0143] Compared with Example 21 of the present invention, in the stage of segmented hot rolling, the final thickness of the high-temperature hot rolling is greater than 2.3 mm and the final thickness of the low-temperature hot rolling is greater than 1.8 mm. Figure 8 is a scanning image of the secondary recrystallization structure morphology of the oriented silicon steel obtained in Example 21 observed under an electron microscope. The secondary recrystallization structure morphologies of Examples 22 and 23 are similar to those of Figure 8 It can be seen from the microscope crystal structure morphology scanning that secondary recrystallization has not occurred in some areas.

[0144] Compared with Example 21 of the present invention, in Comparative Examples 24 and 25, the reduction ratio is greater than 93% during the cold rolling stage. Fig. 9 The secondary recrystallization structure morphology of the oriented silicon steel obtained in Example 24 is observed under an electron microscope, and the secondary recrystallization structure morphology scanning diagram of Example 25 is Fig. 9 It can be seen from the microscope crystal structure morphology scanning that secondary recrystallization has not occurred in some areas.

[0145] 2. Magnetic properties and iron loss detection

[0146] The core loss P of the ultra-thin oriented silicon steel prepared in Examples 1-46 and Comparative Examples 1-25 was tested respectively. 1.7 / 50 , P 1.5 / 200 , P 1.0 / 400 And the magnetic induction intensity B 800 The test results are shown in Table 4 and Table 5:

[0147] Table 4: Iron loss and magnetic induction intensity test results of ultra-thin oriented silicon steel of Examples 1-46 of the present invention

[0148]

[0149]

[0150] Table 5: Iron loss and magnetic induction intensity test results of ultra-thin oriented silicon steel of comparative examples 1-25

[0151]

[0152]

[0153] It can be concluded from Table 4 and Table 5 that the magnetic properties and core loss of the ultra-thin oriented silicon steel of the embodiment of the present invention are better than those of the comparative example. It can be seen that the ultra-thin oriented silicon steel prepared by the method of the present invention has excellent magnetic properties and low iron loss, especially has lower loss at a frequency of 50-400Hz, and the loss P is less than 0.01% at an operating frequency of 50Hz. 1.7 / 50 ≤0.55W / kg, loss P at medium frequency 200Hz 1.5 / 200 ≤3.5W / kg, loss P at medium frequency 400Hz 1.0 / 400 ≤4.7W / kg, magnetic induction B800≥1.90T. It can be seen that the preparation process of the present invention can effectively improve the magnetic properties of ultra-thin oriented silicon steel with a thickness in the range of 0.1-0.15mm, and reduce its loss at a frequency of 50-400Hz, which can meet the application of finished products in 50Hz industrial frequency and 100-400Hz medium frequency equipment, and is suitable for equipment such as grid-connected transformers for new energy such as wind power, meeting the application requirements of long-distance large-capacity transmission and grid-connected engineering of new energy, and has short process flow, low energy consumption, high production efficiency and low cost, meeting the needs of enterprises for high-efficiency production.

[0154] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A method for preparing ultra-thin oriented silicon steel, characterized in that: The following steps are involved: Material selection: selecting a steel billet, wherein the chemical composition of the steel billet comprises, by mass percentage, C: 0.040-0.055%, Si: 2.8-3.3%, Mn: 0.050-1.0%, S: 0.020-0.030%, Al: 0.020-0.030%, N: 0.0020-0.0055%, Cu: 0.40-0.50%, Bi: 0.002-0.005%, and the balance is Fe and unavoidable impurities; The steel billet is sequentially subjected to a hot rolling process and a cold rolling process with a first reduction ratio of ≤93% to obtain a cold-rolled steel billet; The cold-rolled steel billet is subjected to an annealing post-treatment process to obtain an ultra-thin oriented silicon steel product.

2. The preparation method according to claim 1, characterized in that: The hot rolling process adopts segmented hot rolling, which includes: rolling the steel billet in sequence through a first hot rolling pass and a second hot rolling pass, controlling the thickness of the steel billet after the first hot rolling pass to be 2.0-2.3 mm, and controlling the thickness of the steel billet after the second hot rolling pass to be 1.4-1.8 mm.

3. The preparation method according to claim 1 or 2, characterized in that: The thickness of the finished ultra-thin oriented silicon steel product is 0.1-0.15 mm.

4. The preparation method according to claim 2, characterized in that: The first hot rolling adopts high temperature hot rolling, the initial temperature of the high temperature hot rolling is 1150-1250°C, and the final rolling temperature is 950-1050°C.

5. The preparation method according to claim 2, characterized in that: The second hot rolling adopts low temperature hot rolling, the initial temperature of the low temperature hot rolling is 700-800°C, and the final rolling temperature is 550-650°C.

6. The preparation method according to claim 2, characterized in that: The reduction ratio of the second hot rolling is 20-30%.

7. The preparation method according to claim 2, characterized in that: The cold rolling rate is 100-250 m / min.

8. The preparation method according to claim 1, characterized in that: The method further includes: after the hot rolling process and before the cold rolling process: The steel billet obtained after the hot rolling process is subjected to intermediate annealing treatment at a temperature of 1000-1150° C. for 2-5 minutes.

9. The preparation method according to claim 1, characterized in that: The post-annealing treatment process is carried out under a protective atmosphere, and the protective atmosphere is a mixed gas composed of nitrogen and hydrogen in a volume ratio of 9-10:

1.

10. An ultra-thin oriented silicon steel prepared by the preparation method according to any one of claims 1 to 9.

11. The ultra-thin oriented silicon steel according to claim 10, characterized in that: The chemical composition of the ultra-thin oriented silicon steel comprises, by mass percentage, Si: 2.8-3.3%, Mn: 0.050-1.0%, Cu: 0.40-0.50%, Al≤0.0005%, Bi≤0.0001%, C≤0.0002%, N≤0.0002%, S≤0.0002%, and the remainder is Fe and unavoidable impurities.

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