Directional silicon steel and method for producing the same

Abstract

In the present invention, a grain-oriented silicon steel is disclosed which contains, in mass percentage, 90% or more of Fe and unavoidable impurities, and in addition the following chemical elements: C: 0.020 to 0.080%, Si: 2.00 to 4.50%, Mn: 0.01 to 0.10%, S ≤ 0.005%, acid-soluble aluminum Al: 0.010 to 0.040%, N: 0.002 to 0.015%, Nb: 0.006 to 0.120%, and at least one selected from P: 0.01 to 0.10%, Sn: 0.01 to 0.30%, and Cu: 0.01 to 0.50%. In the present invention, a method for manufacturing the grain-oriented silicon steel is further disclosed, the method including the following: smelting and casting; heating; hot rolling; cold rolling; decarburization annealing; nitriding; application of an annealing separator; high-temperature annealing; and application of an insulation coating and scoring. The grain-oriented silicon steel and the method for manufacturing the same according to the present invention are environmentally friendly and have low energy consumption, achieve a high level of harmony between high magnetic induction intensity and low magnetic strain, and have a very wide range of application prospects.

Description

Technical Field

[0001] Technical Field The present invention relates to oriented silicon steel and a method for manufacturing the same, and more particularly to oriented silicon steel having low magnetic strain and a method for manufacturing the same.

Background Art

[0002] Background Oriented silicon steel is a soft magnetic material characterized by a sharp {110}<001> orientation (i.e., Goss grains). Oriented silicon steel, which is an important functional material, is generally used in the manufacture of transformer cores.

[0003] In the prior art, depending on different magnetic properties and Goss grain orientation degrees, oriented silicon steel can be generally divided into general oriented silicon steel (abbreviated as CGO) and high magnetic oriented silicon steel (abbreviated as Hi-B); compared with CGO silicon steel, Hi-B silicon steel has lower iron loss, higher magnetic induction intensity, and smaller magnetic strain. In recent years, as attention to the noise performance of transformers has increased, the noise performance of transformers has become an important indicator for manufacturers. Since the magnetic strain of oriented silicon steel has a decisive influence on the noise performance of transformers, oriented silicon steel with small magnetic strain has become a research hot spot.

[0004] In the manufacturing process of oriented silicon steel, the prior art mainly reduces the magnetic strain of oriented silicon steel through the following three technical routes: 1) increasing the Goss grain orientation degree of the oriented silicon steel product, 2) reducing the thickness of the oriented silicon steel product, and 3) applying a high-tension coating. All of these three technical routes can reduce the magnetic strain of oriented silicon steel.

[0005] CN111748731A (disclosed on October 9, 2020, "Directional Silicon Steel with Low Magnetostriction and Its Manufacturing Method") produces a preferred particle orientation (rearrangement of magnetic domain structure) caused by a part of magnetic inhomogeneity due to a partially sequential structure arrangement by subjecting a silicon steel substrate to hot rolling and magnetic annealing under specific conditions. As a result, the unidirectional magnetic anisotropy along the rolling direction increases (i.e., the volume of 180° magnetic walls increases and the volume of 90° magnetic walls decreases). Thereby, the volume of 90° magnetic domains of the directional silicon steel product decreases, and thus the magnetostriction of the directional silicon steel decreases, and consequently the overall noise level of the transformer decreases. This application performed magnetic annealing under the following conditions: a magnetic annealing temperature of 750 - 200 °C, a magnetic field oriented in the rolling direction or the transverse direction, and a pulsed magnetic field (50 ms, 1 - 10 Hz) with a magnitude of 2500 A / m DC magnetic field + 50000 A / m short-time pulsed magnetic field. The obtained directional silicon steel product has L v A(17 / 50) < 55 dB(A).

[0006] CN105220071A (disclosed on January 6, 2016, "Directional Silicon Steel with Low Noise Characteristics and Its Manufacturing Method") discloses a directional silicon steel having 0.1% ≤ Cu ≤ 0.5% and 0.01% ≤ S ≤ 0.05% in the directional silicon steel substrate, and the atomic ratio Cu / S satisfies: 5 ≤ Cu / S ≤ 10. During the manufacturing process of the directional silicon steel, the coating tension on the steel surface and the particle size of the product are strictly controlled. The L v A(17) < 55 dB(A), and the vibration generated by the core of the transformer made of this directional silicon steel is small. As a result, the overall noise level of the transformer is reduced.

[0007] CN107881411A (disclosed on April 6, 2018, "Low-Iron-Loss Silicon Steel Products for Low-Noise Transformers and Their Manufacturing Methods") discloses low-iron-loss and low-noise oriented silicon steel. This application strictly controls the perpendicular reflectance R of the magnesium silicate bottom layer of the oriented silicon steel substrate to visible light to be 40-60%, and ensures that the magnesium silicate bottom layer has a uniform luminance, thereby reducing iron loss and reducing magnetostriction / reducing noise. The vibration noise of the magnetostriction of the final product is less than 60 dB(A), which is particularly suitable for transformers.

[0008] It can be seen that by controlling both the 90° magnetic domain distribution and the coating tension level, magnetostriction can be reduced to a certain extent. However, all of these methods require the use of additional external devices or conditions to reduce magnetostriction, and the magnitude of magnetostriction reduction is not significant. For example, in CN111748731A, by applying a magnetic field, the 90° magnetic domain can be affected and the volume of the 180° magnetic wall can be increased. However, when the Goss texture of the oriented silicon steel substrate itself is not sharp enough, the magnitude of magnetostriction reduction by subsequent external application conditions is relatively limited. Also, the method of refining the magnetic domain by increasing the coating tension has the same problem and also has very high requirements for coating properties. Furthermore, in some prior arts, magnetostriction can be reduced to a certain extent by reducing the thickness of the silicon steel sheet. However, since silicon steel has a high silicon content, it is more difficult to roll silicon steel to a thinner thickness, and it also leads to an increase in cost.

[0009] Therefore, there are significant limitations in the prior art of reducing magnetostriction by increasing the coating tension and decreasing the thickness of silicon steel. In contrast, by improving the Goss grain orientation degree of the grain-oriented silicon steel itself (for example, by optimizing the chemical composition and adjusting the manufacturing process to improve the Goss grain orientation degree of the grain-oriented silicon steel product), that is, by reducing the declination angle of Goss grains, thereby increasing the magnetic induction intensity, it is possible to fundamentally reduce the magnetostriction of the grain-oriented silicon steel. Also, in the strategic goal of "carbon peaking and carbon neutrality", energy conservation and environmental protection have also become one of the focuses of the current production process. On the premise of reducing energy consumption, ensuring the high-quality and stable production of grain-oriented silicon steel has become one of the important research and development directions of grain-oriented silicon steel.

[0010] For the above reasons, the inventors expect to develop a new type of low-magnetostriction grain-oriented silicon steel and its manufacturing method that can essentially improve the magnetic induction intensity of grain-oriented silicon steel and reduce the magnetostriction of grain-oriented silicon steel (by reducing the declination angle of Goss grains) based on a green and consumption-reducing manufacturing process through highly designing the chemical composition of grain-oriented silicon steel and reasonably optimizing the manufacturing process. Thereby, a high level of harmony between the high magnetic induction intensity and low magnetostriction of grain-oriented silicon steel can be achieved.

Summary of the Invention

Means for Solving the Problems

[0011] Overview The object of the present invention is to provide a grain-oriented silicon steel and its manufacturing method. This grain-oriented silicon steel has excellent harmony in magnetic properties (especially regarding high magnetic induction intensity and low magnetostriction), and at the same time, the consumption of energy media in the manufacturing process is significantly reduced.

[0012] The first aspect of the present invention provides a grain-oriented silicon steel containing, by mass percentage, 90% or more of Fe and unavoidable impurities, in addition to the following components: C: 0.020 to 0.080%, Si: 2.00 to 4.50%, Mn: 0.01 to 0.10%, S ≤ 0.005%, acid-soluble aluminum Al: 0.010 to 0.040%, N: 0.002 to 0.015%, Nb: 0.006 to 0.120%, and at least one selected from P: 0.01 to 0.10%, Sn: 0.01 to 0.30%, and Cu: 0.01 to 0.50%.

[0013] Preferably, the grain-oriented silicon steel contains the following components by mass percentage: C: 0.020 to 0.080%, Si: 2.00 to 4.50%, Mn: 0.01 to 0.10%, S ≤ 0.005%, acid-soluble aluminum Al: 0.010 to 0.040%, N: 0.002 to 0.015%, Nb: 0.006 to 0.120%, and at least one selected from P: 0.01 to 0.10%, Sn: 0.01 to 0.30%, and Cu: 0.01 to 0.50%; the balance being Fe and unavoidable impurities.

[0014] Preferably, the grain-oriented silicon steel has a thickness of 0.15 to 0.30 mm.

[0015] Preferably, the grain-oriented silicon steel has a magnetic induction intensity of B8 > 1.95 T and a magnetostrictive vibration velocity sound pressure level of L v A < 50 dB(A).

[0016] Another aspect of the present invention provides a method for manufacturing the above grain-oriented silicon steel, including the following steps: 1) Smelting and casting molten steel to produce a slab; 2) Heating the slab; 3) Hot rolling including rough rolling, coiling, holding, and final rolling; 4) Cold rolling; 5) Decarburization annealing; 6) Nitriding; 7) Applying an annealing separator; 8) High-temperature annealing; 9) Apply an insulating coating and then perform scoring to produce grain-oriented silicon steel.

[0017] Preferably, in step 1), the thickness of the slab is 180 - 250 mm.

[0018] Preferably, in step 2), the heating temperature of the slab is 900 - 1150 °C.

[0019] This application uses an inhibitor post - process for nitriding treatment, so the content of inhibitor elements in the slab is relatively low. The heating temperature in step 2) contributes to reducing energy consumption and simultaneously obtaining sufficient inhibitors. If the heating temperature of the slab is lower than 900 °C, the inhibitor elements cannot be effectively solid - solved; if the heating temperature of the slab is higher than 1150 °C, it will increase energy consumption and the thermal load of the heating furnace. Therefore, the heating temperature of the slab in step 2) is preferably controlled to be 900 - 1150 °C.

[0020] Preferably, the thickness of the intermediate slab at the end of rough rolling is 35 - 50 mm.

[0021] Preferably, in step 3), the finishing temperature of rough rolling is higher than 950 °C, the coiling temperature is 800 - 1050 °C, the coiling time is 30 - 200 s, and the initial temperature of the final rolling is lower than 1050 °C.

[0022] This application can ensure that the finishing temperature of rough rolling is set higher than 950°C, the coil winding temperature is 800 - 1050°C, whereby the coil winding time is 30 - 200 s, and the initial temperature of the subsequent final rolling is lower than 1050°C. At this coil winding temperature, during the coil winding and holding processes, the layers of the hot-rolled sheet itself heat each other, so additional heating is unnecessary; also, the coil winding between rough rolling and final rolling enables more complete recrystallization of the hot-rolled sheet structure and simultaneously allows some of the inhibitor to be dispersed and precipitated. If the coil winding temperature is lower than 800°C or the coil winding time is less than 30 s, the desired recrystallization effect of the hot-rolled sheet structure cannot be achieved; if the coil winding temperature is higher than 1050°C or the coil winding time exceeds 200 s, the grain structure of the intermediate slab and the precipitated inhibitor coarsen, which has an adverse effect on the subsequent structure and the development of the Goss texture. Therefore, it is preferable to set the temperature and / or time of the hot rolling process within the above ranges.

[0023] Preferably, before step 4) and after step 3), a skin pass annealing treatment is performed, and the skin pass annealing temperature does not exceed 1000°C, preferably 800 - 1000°C, more preferably 800 - 980°C, and the skin pass annealing time is 20 - 200 s.

[0024] The inventors have conducted extensive research and surprisingly found that the skin pass annealing of hot-rolled sheets at an annealing temperature of approximately 1100 - 1200°C, as routinely performed according to the current prior art, not only results in an overly large particle structure of the skin pass sheet but also causes coarsening of the inhibitor and ultimately degrades the magnetic properties.

[0025] By coiling and holding the rough-rolled sheet at a temperature of 800 to 1050 °C, after decarburization annealing, without performing subsequent normalizing annealing or performing normalizing annealing at a normalizing annealing temperature of 1000 °C or lower, a ratio of more than 10% is achieved for Goss grains with a tilt angle of less than 3°, thereby making it possible to obtain a grain-oriented silicon steel product having a desired Goss grain orientation degree and magnetic induction strength. On the other hand, when the rough-rolled sheet is not coiled and held, or when the normalizing annealing temperature after coiling and holding is higher than 1000 °C, the ratio of Goss grains with a tilt angle of less than 3° in the steel sheet after decarburization annealing is significantly low (i.e., significantly less than 10%).

[0026] Preferably, in step 4), the reduction ratio of cold rolling is >80%.

[0027] Preferably, in step 5), the decarburization annealing temperature is 800 to 900 °C. If the decarburization annealing temperature is lower than 800 °C, the decarburization effect is not significant; if the decarburization annealing temperature is higher than 900 °C, the grains after primary recrystallization become too coarse, affecting secondary recrystallization.

[0028] Preferably, in step 5), in the steel sheet after decarburization annealing, the ratio of Goss grains with a tilt angle of less than 3° is more than 10%. In this specification, the "ratio of Goss grains with a tilt angle of less than 3° in the steel sheet after decarburization annealing" refers to the ratio (%) of the number of Goss grains with a tilt angle of less than 3° to the total number of Goss grains.

[0029] In this specification, the "tilt angle" refers to the tilt angle of Goss grain orientation. The tilt angle and the ratio of Goss grains are observed and counted by a scanning electron microscope equipped with an electron backscatter diffraction (EBSD) system.

[0030] Preferably, in step 6), the amount of nitridation is 50 to 280 ppm.

[0031] This application uses an inhibitor post-process for nitriding treatment. That is, the nitriding treatment needs to be carried out before high-temperature annealing to form an inhibitor sufficient to suppress the growth of primary recrystallized grains. If the amount of nitriding is less than 50 ppm, the amount of inhibitor formation is insufficient; if the amount of nitriding is more than 280 ppm, it will have an adverse effect on the formation of the magnesium silicate bottom layer during the high-temperature annealing process. Based on these considerations, the amount of nitriding in step 6) of the present invention is strictly controlled to be 50 - 280 ppm.

[0032] In step 7), the annealing release agent may be an annealing release agent commonly used in the art, preferably MgO.

[0033] Preferably, in step 8), the annealing temperature is 1100 - 1250 °C, and the annealing time is longer than 25 hours.

[0034] In step 9), an insulating coating may be formed using a coating liquid commonly used in the art, such as by applying a coating liquid containing phosphate, colloidal silicon dioxide, and anhydrous chromate. Scoring may be performed using a scoring method commonly used in the art, such as laser scoring, electrochemical scoring, tooth roller scoring, high-pressure water beam scoring, etc.

[0035] Compared with the prior art, the oriented silicon steel and its manufacturing method according to the present invention achieve the following beneficial effects: The inventors have found through many experiments that the orientation degree of Goss grain nuclei in primary recrystallization has a decisive influence on the orientation degree of Goss grains and the magnetic induction intensity of the product. Therefore, the inventors optimized the design of related process parameters so that the proportion of Goss grains with a deviation angle of less than 3° in the steel sheet after decarburization annealing exceeds 10%, thereby obtaining an oriented silicon steel product having the desired orientation degree of Goss grains and magnetic induction intensity.

[0036] Based on a manufacturing process that is environmentally friendly and reduces consumption, the present invention obtains a grain-oriented silicon steel with a harmonious combination of high magnetic induction intensity and low magnetostriction. The grain-oriented silicon steel in the present invention has excellent magnetic properties (magnetic induction intensity B8 > 1.95T, magnetostriction vibration velocity sound pressure level L v A < 50 dB(A)), and has good economic advantages and application prospects.

Embodiments for Carrying Out the Invention

[0037] Detailed Description As a result of intensive research, the inventors of the present invention surprisingly found that by designing the chemical composition of the above-mentioned grain-oriented silicon steel, a grain-oriented silicon steel with excellent comprehensive performance (particularly, high magnetic induction intensity and low magnetostriction) can be obtained. Specifically, the design principles of each of the above chemical elements are as follows. In the present application, the content of an element is expressed in mass percentage unless otherwise specified.

[0038] C: The addition of an appropriate amount of C ensures that an appropriate proportion of γ-phase can be obtained in the hot rolling or annealing process, which contributes to the precipitation of finely dispersed inhibitors. When the C content in the steel is lower than 0.020%, the proportion of γ-phase is low, which is disadvantageous for the precipitation of inhibitors; when the C content in the steel is higher than 0.080%, the decarburization cost becomes high. Based on these considerations, the C content in the grain-oriented silicon steel of the present invention is controlled to be 0.020 - 0.080%, preferably 0.022 - 0.073%.

[0039] Si: Si is the main element for reducing iron loss. To ensure the quality of silicon steel products, the Si content in the steel should not be too low or too high. When the Si content in the silicon steel is lower than 2.00%, it is difficult to obtain the desired low iron loss in grain-oriented silicon steel products; when the Si content in the steel is higher than 4.50%, cold rolling becomes difficult and the product yield decreases. Based on these considerations, the Si content in the grain-oriented silicon steel of the present invention is controlled to be 2.00 - 4.50%, preferably 2.19 - 4.29%.

[0040] Mn: The addition of an appropriate amount of Mn can form a small amount of MnS auxiliary inhibitor in the continuous casting and hot rolling processes, which can effectively improve the microstructure and rolling properties of the grain-oriented silicon steel. To ensure the performance of the grain-oriented silicon steel, the Mn content in the steel must be strictly controlled. If the Mn content is less than 0.01%, it is harmful to obtain the desired microstructure and rolling properties of the silicon steel; if the Mn content exceeds 0.10%, the slab heating temperature will increase significantly, and coarse MnS inhibitors are likely to be formed. Based on these considerations, the Mn content in the grain-oriented silicon steel of the present invention is controlled to be 0.01 - 0.10%, preferably 0.01 - 0.09%.

[0041] S: S can form auxiliary inhibitors such as MnS and Cu2S. However, it should be noted that the S content in the steel should not be too high. If the S content in the steel is too high, the slab heating temperature will increase significantly, which is not favorable for production. Based on these considerations, the S content in the grain-oriented silicon steel of the present invention is controlled to be S ≤ 0.005%, preferably ≤ 0.004%.

[0042] Acid-soluble aluminum Al: Acid-soluble aluminum Al is an important component for the formation of the main inhibitor AlN. If the acid-soluble aluminum Al content in the steel is lower than 0.010%, the inhibitor will be insufficient; if the acid-soluble aluminum Al content in the steel is higher than 0.040%, the inhibitor AlN will coarsen. Therefore, the acid-soluble aluminum Al content in the silicon steel needs to be strictly controlled. Based on these considerations, the acid-soluble aluminum Al content in the grain-oriented silicon steel of the present invention is controlled to be 0.010 - 0.040%, preferably 0.012 - 0.039%.

[0043] N: The addition of an appropriate amount of N can appropriately suppress particle growth. The addition of N in silicon steel can cooperate with acid-soluble aluminum Al to form AlN before nitridation, thereby effectively suppressing the growth of primary recrystallized particles. When the N content in the steel is lower than 0.002%, the growth of primary recrystallized particles cannot be effectively suppressed; when the N content in the steel is higher than 0.015%, the difficulty of steelmaking significantly increases. Based on these considerations, the N content in the oriented silicon steel of the present invention is controlled to be 0.002 to 0.015%, preferably 0.003 to 0.014%.

[0044] Nb: To lower the slab heating temperature, the contents of Mn and Cu are relatively low, which results in insufficient precipitation of MnS and Cu2S. Therefore, an appropriate amount of Nb is added to the silicon steel to compensate for the insufficient inhibition ability of the inhibitor. Nb can form an auxiliary inhibitor Nb(C,N) and play the role of an auxiliary inhibitor. Also, due to the relatively low solid solution temperature of Nb(C,N), it can also lower the heating temperature of the slab. When the Nb content in the steel is lower than 0.006%, the formed inhibitor Nb(C,N) cannot fully exert its inhibitory effect; when the Nb content in the steel is higher than 0.120%, the inhibitory effect is too strong, preventing the occurrence of secondary recrystallization. Based on these considerations, the Nb content in the oriented silicon steel of the present invention is controlled to be 0.006 to 0.120%, preferably 0.006 to 0.118%.

[0045] P and Sn: Both P and Sn are grain boundary segregation elements. The addition of appropriate amounts of P and Sn in silicon steel can act as auxiliary inhibitors. When the contents of P and Sn in the steel are each lower than 0.01%, the auxiliary inhibitor effect cannot be fully exerted; when the contents of P and Sn in the steel are each higher than 0.10% and 0.30%, respectively, it has an adverse effect on decarburization and nitridation. Based on these considerations, the P content in the oriented silicon steel of the present invention is controlled to be 0.01 to 0.10%, preferably 0.02 to 0.08%, and the Sn content is controlled to be 0.01 to 0.30%, preferably 0.02 to 0.25%.

[0046] Cu: Adding an appropriate amount of Cu in silicon steel can not only form auxiliary inhibitors such as Cu2S, but also effectively expand the γ-phase region, and thus can promote the precipitation of other inhibitors. However, it should be noted that the Cu content in the steel should not be too low or too high. If the Cu content in the silicon steel is less than 0.01%, the above effects cannot be fully exerted; if the Cu content in the silicon steel is higher than 0.50%, the manufacturing cost will increase. Based on these considerations, the Cu content in the grain-oriented silicon steel of the present invention is controlled to be 0.01 - 0.50%, preferably 0.02 - 0.48%, for example 0.02 - 0.39%.

[0047] Hereinafter, the grain-oriented silicon steel of the present invention and its manufacturing method will be further described and exemplified in relation to specific examples. However, the following description is an illustrative description for explaining the present invention and is not intended to limit the technical scope of the present invention to the described content.

[0048] Examples 1 - 12 The grain-oriented silicon steels of Examples 1 - 12 of the present invention are manufactured by the following steps: 1) Smelt and cast molten steel according to the composition shown in Table 1 below to produce a slab with a thickness of 180 - 250 mm. 2) Heat the slab at a temperature of 900 - 1150°C. 3) Rough rolling, coiling and holding of the slab and final rolling: The finishing temperature of the rough rolling is higher than 950°C, the coiling temperature is 800 - 1050°C, the coiling time is 30 - 200 s, and the initial temperature of the final rolling is lower than 1050°C. 4) Cold roll to a final plate thickness of 0.15 - 0.30 mm, where the reduction ratio of the cold rolling is >80%. 5) Decarburize and anneal at a temperature of 800 - 900°C. 6) Nitriding, where the amount of nitriding is 50 - 280 ppm. 7) Apply an annealing separator. 8) High-temperature annealing, where the annealing temperature is 1100 - 1250°C, and the annealing time is longer than 25 hours. 9) Apply an insulating coating and perform scoring to produce a grain-oriented silicon steel with a thickness of 0.15 to 0.30 mm.

[0049] It should be noted that for examples other than Example 10 and Example 11, they were also subjected to a normalizing annealing treatment (the normalizing annealing temperature was 1000 °C or lower, and the normalizing annealing time was 20 to 200 s) between Step 3) and Step 4).

[0050] Comparative Examples 1 - 20 Comparative Examples 1 - 20 used a similar process to produce grain-oriented silicon steel. Here, for comparative examples other than Comparative Example 16, they were also subjected to a normalizing annealing treatment between Step 3) and 4). However, the chemical compositions and process parameters of the grain-oriented silicon steels in Examples 1 - 12 satisfied the claims of the present invention, while at least one of the chemical compositions and / or process parameters of Comparative Examples 1 - 20 did not satisfy the claims of the present invention.

[0051] The chemical compositions of the grain-oriented silicon steels in Examples 1 - 12 and Comparative Examples 1 - 20 are shown in Table 1.

[0052]

Table 1 - 1

[0053]

Table 1 - 2

[0054] The specific process parameters for Examples 1 - 12 and Comparative Examples 1 - 20 in the above process steps are shown in Table 2 - 1 and Table 2 - 2.

[0055]

Table 2 - 1

[0056]

Table 2 - 2

[0057]

Table 2-3

[0058]

Table 2-4

[0059] In Process 5), the steel plates after decarburization annealing of Examples 1 to 12 and Comparative Examples 1 to 20 were sampled, and then the ratio of Gaussian grains with a misorientation angle of less than 3° in each sample was observed and analyzed by a scanning electron microscope equipped with an electron backscatter diffraction (EBSD) system.

[0060] Table 3 shows the ratio of Gaussian grains with a misorientation angle of less than 3° in the steel plates after decarburization annealing of Examples 1 to 12 and Comparative Examples 1 to 20.

[0061]

Table 3

[0062] As shown in Table 3, the ratio of Gaussian grains with a misorientation angle of less than 3° in the steel plates after decarburization annealing of Examples 1 to 12 is 11% to 22%. In contrast, the ratio of Gaussian grains with a misorientation angle of less than 3° in the steel plates after decarburization annealing of Comparative Examples 1 to 20 is 3.6% to 9.4%, which is significantly lower than that of Examples 1 to 12.

[0063] Directional silicon steel products manufactured in Examples 1 to 12 and Comparative Examples 1 to 20 were sampled, and the magnetic properties of each sample were measured and analyzed to obtain the magnetic induction intensity B8 and the magnetostrictive vibration velocity sound pressure level L v A of each directional silicon steel sample.

[0064] In this application, the test methods related to the magnetic properties of directional silicon steel will be described as follows: Magnetic property test: Measure the magnetic induction intensity of the grain-oriented silicon steel of Examples 1 to 12 and Comparative Examples 1 to 20 in accordance with the national standard GB / T 13789-2008 "Method for Measuring Magnetic Properties of Electromagnetic Steel Sheets (Stripes) Using a Monolithic Tester".

[0065] Magnetostriction test: In accordance with IEC Technical Report IEC / TP 62581, measure the magnetostriction vibration velocity sound pressure level L v A of the grain-oriented silicon steel of Examples 1 to 12 and Comparative Examples 1 to 20 using a non-contact laser Doppler vibrometer at B = 1.7 T and f = 2 MPa (in the actual use conditions of a transformer, the compressive stress applied to the grain-oriented silicon steel is 2 to 3 MPa). In this specification, L v A is the magnetostriction vibration velocity sound pressure level of the grain-oriented silicon steel under the above test conditions. The unit is dB(A).

[0066] The magnetic induction intensity B8 and the magnetostriction vibration velocity sound pressure level L v A of the grain-oriented silicon steel of Examples 1 to 12 and Comparative Examples 1 to 20 are shown in Table 4.

[0067]

Table 4

[0068] As shown in Table 4, the magnetic induction intensity B8 of Examples 1 to 12 is 1.954 to 1.972 T, and the magnetostriction vibration velocity sound pressure level L v A is 43 to 48 dB(A). In contrast, the magnetic induction intensity B8 of Comparative Examples 1 to 20 is 1.805 to 1.939 T (significantly lower than that of Examples 1 to 12), and the magnetostriction vibration velocity sound pressure level L v A is 51 to 64 dB(A) (significantly higher than that of Examples 1 to 12).

[0069] As can be seen from Tables 1 to 4, the proportion of Gauss grains with a declination angle of less than 3° in the steel sheets after decarburization annealing of Examples 1 to 12 is significantly higher than that of Comparative Examples 1 to 20, and their magnetic properties (especially the magnetic induction intensity B8 and L v A) are significantly better than those of Comparative Examples 1 to 20.

[0070] After analyzing the ratio of Goss grains with a tilt angle of less than 3° in the steel sheet after decarburization annealing, the inventors surprisingly found that different combinations of hot rolling and temper rolling process parameters have a significant impact on the tilt angle α of the Goss grain orientation in the steel sheet after decarburization annealing. By coiling and holding the rough rolled sheet at a temperature of 800 to 1050°C and then performing low-temperature temper rolling (the temper rolling temperature is 1000°C or lower), or by not performing the temper rolling treatment, the ratio of Goss grains with a tilt angle of less than 3° in the steel sheet after decarburization annealing can be significantly increased, particularly within the range of the chemical composition claimed in the present invention. The inventors have found through extensive experiments that the degree of orientation of Goss grain nuclei in primary recrystallization has a decisive influence on the Goss grain orientation degree and magnetic induction intensity of the product. As a result, the grain-oriented silicon steel produced according to the method of the present invention exhibits a high level of harmony between high magnetic induction intensity and low magnetostriction.

[0071] It should be noted that all the technical features recorded in this application may be freely combined or incorporated in any manner as long as they do not conflict with each other. Without departing from the scope of the present invention, various modifications and variations can be made to the present invention as will be apparent to those skilled in the art. For example, the features shown or described as part of one embodiment can be used in combination with another embodiment to create yet another embodiment. Therefore, the present invention is intended to cover modifications and variations that fall within the scope of the appended claims and their equivalents.

Claims

1. A grain-oriented silicon steel containing, in mass percent, 90% or more of Fe and unavoidable impurities, and the following components in addition: C: 0.020 - 0.080%, Si: 2.00 - 4.50%, Mn: 0.01 - 0.10%, S ≤ 0.005%, acid-soluble aluminum Al: 0.010 - 0.040%, N: 0.002 - 0.015%, Nb: 0.006 - 0.120%, and at least one selected from P: 0.01 - 0.10%, Sn: 0.01 - 0.30%, and Cu: 0.01 - 0.50%.

2. The grain-oriented silicon steel according to Claim 1, characterized by containing the following components in mass percent: C: 0.020 - 0.080%, Si: 2.00 - 4.50%, Mn: 0.01 - 0.10%, S ≤ 0.005%, acid-soluble aluminum Al: 0.010 - 0.040%, N: 0.002 - 0.015%, Nb: 0.006 - 0.120%, and at least one selected from P: 0.01 - 0.10%, Sn: 0.01 - 0.30%, and Cu: 0.01 - 0.50%; the balance being Fe and unavoidable impurities.

3. having a thickness of 0.15 to 0.30 mm; preferably, a magnetic induction intensity of B8 > 1.95 T and L v The oriented silicon steel according to claim 1 or 2, characterized in that it has a magnetostrictive vibration velocity sound pressure level of A < 50 dB(A).

4. A method for manufacturing the grain-oriented silicon steel according to any one of Claims 1 to 3, comprising the following steps: 1) Smelting and casting molten steel to produce a slab; 2) Heating the slab; 3) Hot rolling including rough rolling, coiling and holding, and final rolling; 4) Cold rolling; 5) Decarburization annealing; 6) Nitriding; 7) Applying an annealing separator; 8) High-temperature annealing; 9) Applying an insulating coating and performing scoring to produce a grain-oriented silicon steel.

5. The method according to Claim 4, characterized in that in step 3), the finishing temperature of rough rolling is higher than 950°C, the coiling temperature is 800 - 1050°C, the coiling time is 30 - 200 s, and the initial temperature of final rolling is lower than 1050°C.

6. The method according to Claim 4, characterized in that after step 3) and before step 4), a homogenizing annealing treatment is performed, and the homogenizing annealing temperature does not exceed 1000°C, preferably 800 - 1000°C, more preferably 800 - 980°C, and the homogenizing annealing time is 20 - 200 s.

7. The method according to any one of Claims 4 to 6, characterized in that in step 2), the heating temperature of the slab is 900 - 1150°C.

8. The method according to any one of claims 4 to 6, characterized by satisfying one or more of the following: In step 1), the thickness of the slab is 180 to 250 mm; In step 3), the thickness of the intermediate slab at the end of rough rolling is 35 to 50 mm; In step 4), the reduction ratio of cold rolling is > 80%; and In step 7), the annealing separator is MgO.

9. In step 5), the decarburization annealing temperature is 800 to 900 °C; preferably, the ratio of Gauss grains with a declination angle of less than 3° in the steel sheet after decarburization annealing is greater than 10%. The method according to any one of claims 4 to 6.

10. In step 6), the amount of nitridation is 50 to 280 ppm. The method according to any one of claims 4 to 6.

11. In step 8), the annealing temperature is 1100 to 1250 °C, and the annealing time is longer than 25 hours. The method according to any one of claims 4 to 6.

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