High-magnetic-induction oriented silicon steel and manufacturing method therefor

Abstract

A high-magnetic-induction oriented silicon steel, comprising, in addition to Fe and inevitable impurities, the following chemical elements in percentage by mass: C≤0.005%, Si: 3.0-3.8%, Als: 0.010-0.035%, Mn: 0.05-0.20%, and at least one of Ce and La which satisfy: Ce+La: 0.003-0.3%, wherein among the inevitable impurity elements, N≤0.005%, S≤0.005%, V≤0.005%, and Ti≤0.005%. Also provided is a manufacturing method for the high-magnetic-induction oriented silicon steel. The annealing temperature of a hot rolled plate can be reduced, annealing of the hot rolled plate can be omitted, the thin-gauge high-magnetic-induction oriented silicon steel can be efficiently produced by means of a cold continuous rolling method, and the magnetic performance of a product is improved while the manufacturing cost is reduced.

Description

High magnetic induction oriented silicon steel and manufacturing method thereof Technical Field

[0001] The present invention relates to a type of steel and a manufacturing method thereof, in particular to a type of oriented silicon steel and a manufacturing method thereof. Background Art

[0002] Grain-oriented silicon steel is a soft magnetic material with excellent magnetic properties. It is composed of grains with a so-called Goss texture. The Goss texture is represented by the Miller index {110} <001> , the {110} crystal plane of the grain is parallel to the rolling plane, and the <001> The crystal direction is parallel to the rolling direction. <001> Crystal orientation has the best magnetization properties in oriented magnetic fields. By fully utilizing magnetocrystalline anisotropy, the optimal magnetic properties of polycrystalline materials are achieved. Transformer cores made of oriented silicon steel, in oriented magnetic fields, have extremely high magnetic induction intensity and extremely low iron loss, which can significantly save materials and energy.

[0003] Generally speaking, the iron loss P is usually used. 17 / 50 and magnetic induction intensity B8 to characterize the magnetic performance level of oriented silicon steel, where P 17 / 50 B represents the iron loss per kg of sample at a magnetic flux density of 1.7 T and a frequency of 50 Hz; B8 represents the magnetic flux density corresponding to a magnetic field strength of 800 A / m. These two parameters effectively reflect the magnetic performance of grain-oriented silicon steel under different magnetic field and frequency conditions.

[0004] Existing manufacturing processes require complex processes to achieve full-process control of microstructure, texture, and inhibitor evolution to obtain finished plates with abnormally grown Goss grains. Grain-oriented silicon steel can be categorized by process flow into single-cold rolling and double-cold rolling. The single-cold rolling method is used to produce high-magnetic-induction oriented silicon steel with AlN and MnS as the primary inhibitors, while the double-cold rolling method is used to produce conventional oriented silicon steel with MnS and Cu2S as the primary inhibitors. The slab heating temperature can also be categorized into low-temperature slab heating processes and high-temperature slab heating processes. The low-temperature slab heating process uses a slab heating temperature below 1250°C.

[0005] Because the low-temperature slab heating process can produce high-magnetic-induction oriented silicon steel at a lower cost, it has developed rapidly and gradually become mainstream. In the low-temperature slab heating process, inhibitors come from both existing inclusions in the slab, which are called primary inhibitors and have a significant impact on primary recrystallization, thereby affecting the magnetic properties of the final product; and from nitriding treatment after decarburization annealing, which are called secondary inhibitors and work together with primary inhibitors to promote secondary recrystallization. Although the low-temperature slab heating process is difficult to control inhibitors and has a narrow annealing process window, the product grade of this process has been continuously improved with the application of improved processes such as adding auxiliary inhibitors, controlling inclusion morphology, and using rapid induction heating.

[0006] To improve transformer efficiency, the fundamental measure is to improve the magnetic properties of the core material. This requires the core material to have low iron loss and high magnetic induction intensity. Iron loss is determined by both the material itself and the operating frequency and magnetic induction intensity of the material in the alternating magnetic field. The magnetic induction intensity is primarily influenced by the material's Goss grain orientation. Grain orientation refers to the direction and degree of grain arrangement within the material. Generally speaking, the higher the Goss grain orientation, the higher the magnetic induction intensity of the oriented silicon steel.

[0007] Iron losses in oriented silicon steel are primarily composed of hysteresis loss and eddy current loss, with eddy current loss accounting for the majority. Commonly used techniques for reducing iron losses in oriented silicon steel include increasing grain orientation, reducing strip thickness, and refining magnetic domains through scoring. However, with the continuous advancement of oriented silicon steel manufacturing technology, increasing grain orientation and refining magnetic domains through scoring have reached a relatively mature stage, resulting in limited improvements in magnetic properties. Therefore, reducing strip thickness has become the primary method for reducing iron losses in oriented silicon steel.

[0008] Strip thickness significantly affects the total core loss. Reducing strip thickness effectively suppresses eddy current losses, significantly reducing total core loss. As the number of laminations increases, the total core loss decreases more rapidly for a core of equal volume. However, it's important to note that excessively thin strip thickness can lead to a sharp increase in manufacturing costs and significantly degrade magnetic properties due to increased hysteresis losses. Therefore, when choosing the optimal strip thickness, a balance between manufacturing cost and magnetic performance is crucial.

[0009] While reducing strip thickness can reduce iron loss, it also presents some challenges and limitations. First, the number of effective Goss nuclei decreases: As the strip thickness decreases, its specific surface area increases significantly, and the number of effective Goss nuclei decreases accordingly. Simultaneously, inhibitor coarsening and decomposition intensify during annealing, weakening the inhibitor's strength. This adversely affects the secondary recrystallization process, and thus the magnetic properties of the product. Second, cold rolling reduction rate control: To achieve the desired primary recrystallization texture, an appropriate cold rolling reduction rate is necessary. However, if the strip thickness is too thin, the hot coil thickness must also be reduced, increasing the difficulty of hot-rolled plate shape control and reducing hot-rolled production stability. Third, the production efficiency of the hot-rolled plate annealing unit decreases significantly: Thinning the hot-rolled plate thickness leads to a significant decrease in the production efficiency of the annealing unit. When the hot-rolled plate thickness is reduced from 2.6mm to 1.8mm, the unit efficiency decreases by approximately 30%. Due to the above problems, under the premise of ensuring product quality and production stability, the thickness of the finished product of the existing oriented silicon steel preparation process is mostly between 0.23 and 0.30 mm, which is difficult to further thin.

[0010] In addition, in order to achieve the desired inhibitor distribution state, hot-rolled plate annealing has become an indispensable process step in the preparation of high magnetic induction oriented silicon steel. During the hot-rolled plate annealing process, the hot-rolled pickled plate is rapidly heated to about 1120°C, held at this temperature for 2 to 4 minutes, air-cooled to about 900°C, and then water-cooled, or a two-stage treatment is performed after holding at this temperature for another 2 minutes and then water-cooled. After annealing, the recrystallized grains on the surface of the hot-rolled plate grow, and the quenching process will produce a certain amount of martensite structure. The quenching and phase transformation stress will also produce mechanical twins. These factors increase the difficulty of cold rolling. Due to the hot-rolled plate annealing and the large reduction rate at one time, the existing high magnetic induction oriented silicon steel needs to be cold-rolled using a 20-high reversible rolling mill with high rolling stress, which makes it difficult to improve rolling efficiency.

[0011] In order to efficiently manufacture thin-gauge high-magnetic-induction oriented silicon steel, several new oriented silicon steel manufacturing technologies have been developed in recent years.

[0012] For example, the Chinese patent document, "An Ultra-Thin High-Magnetic Induction Grained Silicon Steel and Its Rolling Method," with publication number CN116460139A and publication date July 21, 2023, discloses an ultra-thin high-magnetic induction grained silicon steel and its rolling method. In this technical solution, the final product thickness is 0.12 to 0.20 mm. The main difference between this method and existing high-magnetic induction grained silicon steel production processes lies in the rolling process, replacing the reversing rolling used in the existing single-stage cold rolling process with a combined cold tandem rolling and reversing rolling process. The working roll diameter of the cold tandem rolling process is 300 to 500 mm, with a total reduction of 60 to 91%; the working roll diameter of the reversing rolling process is 70 to 150 mm, with a total reduction of 10 to 50%. Compared with existing production processes, this technical solution only adjusts the cold rolling method, which has limited effect on reducing the manufacturing cost of thin-gauge grained silicon steel and improving the product's magnetic properties. It also fails to address the difficulty of cold rolling existing grained silicon steel hot-rolled sheets after annealing.

[0013] For example, the Chinese patent with publication number CN114134423A and publication date of March 4, 2022, entitled "An ultra-short process rare earth oriented silicon steel and its preparation method" discloses a solution for preparing oriented silicon steel by thin strip continuous casting process. The production process of this technical solution includes: molten steel smelting, thin strip continuous casting, cold rolling, primary recrystallization annealing, coating of isolation agent, secondary recrystallization annealing and other processes, which can directly obtain 2-2.5mm thick cast strips, and the thickness of the prepared oriented silicon steel products is 0.20-0.35mm, with an iron loss P 17 / 50 The magnetic flux density is 0.9-1.1 W / kg, and the magnetic induction intensity B8 is 1.87-1.95 T. Compared with the existing process, this technical solution omits important steps such as continuous casting, rough rolling, hot rolling, normalizing and other related heating processes in the conventional process, which has obvious cost advantages. However, the production stability of thin strip continuous casting technology and the magnetic properties of the product need to be improved. Summary of the Invention

[0014] One of the purposes of the present invention is to provide a high magnetic induction oriented silicon steel, which, through reasonable chemical composition design, can obtain thin-gauge high magnetic induction oriented silicon steel while omitting the hot-rolled plate annealing step, thereby reducing manufacturing costs while improving the magnetic properties of the product.

[0015] In order to achieve the above object, the present invention provides a grain-oriented silicon steel, which, in addition to containing Fe and unavoidable impurities, further contains the following chemical elements in percentage by mass:

[0016] C≤0.005%;

[0017] Si: 3.0-3.8%;

[0018] Als: 0.010~0.035%;

[0019] Mn: 0.05~0.20%;

[0020] At least one selected from Ce and La, and satisfying Ce+La: 0.003-0.3%, preferably 0.0445-0.2433%;

[0021] Among the inevitable impurity elements, N≤0.005%, S≤0.005%, V≤0.005%, and Ti≤0.005%.

[0022] Preferably, in the grain-oriented silicon steel of the present invention, the mass percentage of each chemical element is:

[0023] C≤0.005%;

[0024] Si: 3.0-3.8%;

[0025] Als: 0.010~0.035%;

[0026] Mn: 0.05~0.20%;

[0027] At least one selected from Ce and La, and satisfying Ce+La: 0.003-0.3%, preferably 0.0445-0.2433%;

[0028] The balance is Fe and inevitable impurities; among the inevitable impurity elements, N≤0.005%, S≤0.005%, V≤0.005%, Ti≤0.005%.

[0029] In the high magnetic induction oriented silicon steel of the present invention, the design principles of each chemical element are as follows:

[0030] Excessive carbon (C) can precipitate small, dispersed ε-carbide particles in grain-oriented silicon steel, causing magnetic aging—a phenomenon in which the material's magnetic properties change over time. Therefore, C is considered a residual element in this invention and must be removed through processes such as decarburization annealing and purification high-temperature annealing. Therefore, the mass percentage of C in the high-magnetic-induction grain-oriented silicon steel described in this invention is limited to ≤0.005%.

[0031] Si: Si is a basic element in oriented silicon steel, which can increase resistivity and reduce iron loss. It should be noted that when the mass percentage of Si in steel is less than 3.0%, the resistivity of the material will decrease, and the eddy current loss of oriented silicon steel will not be effectively reduced; accordingly, the Si content in steel should not be too high. When the mass percentage of Si in steel is higher than 3.8%, Si tends to segregate along the grain boundaries, which will increase the brittleness of the steel plate and deteriorate the rollability. In particular, when cold rolling is carried out by continuous cold rolling, the breakage rate increases significantly, and the recrystallization structure and inhibitors become unstable, resulting in an insufficient number of effective Goss nuclei, which in turn causes imperfect secondary recrystallization. Based on this, in the high magnetic induction oriented silicon steel described in the present invention, the mass percentage of Si is controlled between 3.0 and 3.8%.

[0032] Als: Acid-soluble aluminum Als can form a secondary inhibitor during the subsequent nitriding treatment of oriented silicon steel materials, which can work together with the primary inhibitor to form sufficient pinning strength and promote secondary recrystallization. However, it should be noted that when the mass percentage of Als in the steel is lower than 0.010%, the pinning strength of the inhibitor will be insufficient, the directional inhibition effect will be weakened, the secondary recrystallization will be incomplete, or even no secondary recrystallization will occur; and if the mass percentage of Als in the steel is higher than 0.035%, the Als nitride will coarsen, the inhibitor effect will decrease, and the magnetic properties of the material will deteriorate. Based on this, in the high magnetic induction oriented silicon steel described in the present invention, the mass percentage of Als is controlled between 0.010 and 0.035%.

[0033] Mn: Mn is similar to Si in that both elements can increase resistivity and reduce eddy current loss. In addition, Mn can also expand the γ phase region, which has the effect of improving hot rolling plasticity and structure, thereby effectively improving the hot rolling properties of the material. However, it should be noted that when the mass percentage of Mn in the steel is lower than 0.05%, the above-mentioned effect cannot be effectively exerted; and if the mass percentage of Mn added to the steel is higher than 0.20%, a mixed dual-phase structure of α and γ is likely to appear, thereby causing phase transformation stress and generating γ phase during annealing, causing secondary recrystallization instability. Based on this, in the high magnetic induction oriented silicon steel described in the present invention, the mass percentage of Mn is controlled between 0.05 and 0.20%.

[0034] Ce and La: Ce and La elements can change the formation path of inclusions during the solidification of molten steel, thereby improving the precipitation morphology of inhibitors. By reducing the number of coarse MnS+AlN composite inclusions in the slab, the slab heating temperature can be reduced. They can also form Ce-S and La-S with the S element in the molten steel and play the role of auxiliary inhibitors as segregated elements, thereby improving the magnetic properties. In the present invention, the addition of Ce and La helps to solve the problem of weakening the inhibitory force due to rapid ripening of inhibitors during the purification high-temperature annealing process of thin-gauge oriented silicon steel. When the sum of the mass percentages of Ce and La is less than 0.003%, the above-mentioned role cannot be effectively played; but if the sum of the mass percentages of Ce and La exceeds 0.3%, it has a strong inhibitory effect on recrystallization, and the secondary recrystallization is imperfect. Based on this, in the high magnetic induction oriented silicon steel of the present invention, the sum of the mass percentages of Ce and La elements is controlled between 0.003 and 0.3%, preferably between 0.0445 and 0.2433%, and more preferably between 0.1543 and 0.2433%.

[0035] S and N: Excessive S or N will precipitate fine dispersed MnS and Fe in the oriented silicon steel material. 16 Particles such as S4 and N4 can cause magnetic aging, a phenomenon in which the material's magnetic properties change over time. Therefore, these impurities are considered impurities. During the production of grain-oriented silicon steel, S and N must be removed through processes such as decarburization annealing and purification high-temperature annealing. Therefore, in the high-magnetic-induction grain-oriented silicon steel described herein, the S content is limited to ≤0.005% by weight, and the N content is limited to ≤0.005% by weight.

[0036] V and Ti: V will form VN after nitriding treatment of oriented silicon steel materials, which affects secondary recrystallization and is not conducive to the magnetic properties of the material. Ti can preferentially precipitate TiN, while MnS will precipitate attached to TiN, and then AlN will precipitate attached to MnS, which will easily form coarse MnS+AlN composite inclusions, which is also not conducive to the magnetic properties of the material. In addition, reducing the content of Ti and V can also reduce the harmful inclusions of TiN and VN in the finished product. Based on this, in the high magnetic induction oriented silicon steel described in the present invention, the mass percentage of Ti is limited to Ti≤0.005%, and the mass percentage of V is limited to V≤0.005%.

[0037] Preferably, the grain-oriented silicon steel of the present invention further contains at least one selected from the following chemical elements:

[0038] P: 0.01~0.08%; Cr: 0.01~0.40%, Sn: 0.03~0.30%, Cu: 0.01~0.40%, 0<Sb≤0.1%, 0<Bi≤0.1%, 0<Nb≤0.1%, 0<Mo≤0.1%.

[0039] In the high magnetic induction oriented silicon steel of the present invention, the above chemical elements can further improve the performance of the high magnetic induction oriented silicon steel of the present invention. The design principle is as follows:

[0040] P: P is a grain boundary segregation element, which can play the role of an auxiliary inhibitor in oriented silicon steel materials. During the secondary recrystallization process, even at a high temperature of about 1000°C, the P element still has the effect of grain boundary segregation, which can delay the premature oxidation and decomposition of AlN, which is beneficial to secondary recrystallization. At the same time, the P element can also play a role in increasing the resistivity of the material and reducing eddy current loss. However, it should be noted that when the mass percentage of the P element in the steel is lower than 0.01%, the above-mentioned role cannot be effectively exerted; but when the mass percentage of the P element in the steel is higher than 0.08%, it will not only reduce the nitriding efficiency, but also deteriorate the cold rolling properties. Therefore, in the high magnetic induction oriented silicon steel described in the present invention, in some preferred embodiments, the mass percentage of the added P can be preferably set to 0.01-0.08%.

[0041] Cr: Adding Cr not only increases resistivity but also improves the mechanical properties of grain-oriented silicon steel. It also significantly enhances surface quality by promoting oxidation of the steel sheet. To fully maximize the effects of Cr, the Cr content in the steel can be higher than 0.01% by weight. However, considering that adding Cr above 0.40% will form a dense oxide layer during the decarburization process, which in turn affects the efficiency of decarburization and nitriding, in some preferred embodiments of the high magnetic induction grain-oriented silicon steel described herein, the Cr content can be preferably set to 0.01-0.40% by weight.

[0042] Sn: Sn is a grain boundary segregation element that acts as an auxiliary inhibitor. It can effectively compensate for the problem of decreased inhibitory force caused by the coarsening of AlN inclusions due to increased Si content in steel or reduced strip thickness, expand the process window, and facilitate the stability of the product's magnetic properties. However, considering that when the mass percentage of Sn added is less than 0.03%, the above-mentioned effect cannot be effectively achieved; and when the mass percentage of Sn added is higher than 0.30%, it will not only affect the decarburization efficiency, but also cause poor surface quality, and the magnetic properties will not be improved, and the manufacturing cost will increase. Therefore, in the high magnetic induction oriented silicon steel described in the present invention, in some preferred embodiments, the mass percentage of added Sn can be preferably set to 0.03-0.30%.

[0043] Cu: Cu is added to oriented silicon steel because: Cu is similar to Mn in that both can expand the γ phase region, which helps to obtain fine AlN inclusions. In addition to expanding the γ phase region, Cu can also preferentially combine with S to form Cu2S over Mn, which helps to suppress the change in primary grain size. When the mass percentage of Cu added to the steel is less than 0.01%, the above-mentioned effects cannot be exerted; but if the mass percentage of Cu added to the steel is higher than 0.40%, the manufacturing cost will increase and the magnetic properties will not be improved. Therefore, in the high magnetic induction oriented silicon steel described in the present invention, in some preferred embodiments, the mass percentage of the added Cu can be preferably set to 0.01-0.40%.

[0044] Sb and Bi: Sb and Bi are added to oriented silicon steel because: Sb and Bi are also grain boundary segregation elements, both of which have the function of auxiliary inhibitors, which can improve the grain boundary migration conditions of Goss nuclei, help to expand the process window, and improve the magnetic induction of the finished product. However, when the mass percentage of Sb and Bi in the steel is higher than 0.100%, it will not only affect the decarburization efficiency, but also cause poor surface quality, and the magnetic properties will not be significantly improved, increasing the manufacturing cost. Therefore, in the high magnetic induction oriented silicon steel described in the present invention, in some preferred embodiments, the mass percentage of Sb can be preferably set to a content of less than 0.100%, and the mass percentage of Bi can also be preferably set to a content of less than 0.100%.

[0045] Nb and Mo: Nb and Mo are added to grain-oriented silicon steel because they are both effective microalloying elements that refine grains and promote the formation of a small, uniform primary grain size. The carbonitrides formed also serve as auxiliary inhibitors, reducing the difficulty of adjusting the primary inhibitor morphology. However, if the mass percentage of Nb and Mo exceeds 0.100%, they have a strong inhibitory effect on recrystallization, resulting in imperfect secondary recrystallization. Therefore, in the high magnetic induction grain-oriented silicon steel described in the present invention, in some preferred embodiments, the mass percentage of Nb can be preferably set to less than 0.100%, and the mass percentage of Mo can be preferably set to less than 0.100%.

[0046] Preferably, the thickness of the high magnetic induction oriented silicon steel of the present invention is 0.13 to 0.20 mm. It should be noted that this thickness refers to the thickness of the silicon steel sheet after cold rolling.

[0047] Preferably, the iron loss P of the high magnetic induction oriented silicon steel of the present invention is 17 / 50 ≤0.86+2×plate thickness-16×Si, magnetic induction intensity B8≥2.14-6.5×Si, where plate thickness is the thickness of silicon steel plate, unit is mm, Si is substituted into the mass percentage of Si element, P17 / 50 The unit of is W / kg, and the unit of B8 is T.

[0048] Accordingly, another object of the present invention is to provide a method for manufacturing the above-mentioned high magnetic induction oriented silicon steel. By adopting this method in combination with the component ratio described above, it is possible to achieve efficient production of thin-gauge high magnetic induction oriented silicon steel by cold continuous rolling while omitting the hot-rolled plate annealing step, thereby reducing manufacturing costs while improving the magnetic properties of the product.

[0049] In order to achieve the above object, the present invention provides a method for manufacturing grain-oriented silicon steel, which comprises the following steps:

[0050] (1) smelting and casting to produce slabs;

[0051] (2) heating the slab;

[0052] (3) hot rolling;

[0053] (4) Single cold rolling

[0054] (5) Intermediate annealing;

[0055] (6) Secondary cold rolling;

[0056] (7) decarburization annealing, nitriding treatment, and coating with a release agent coating, the average primary grain size of the decarburized annealed plate obtained is 6 to 18 μm, and the number of Goss grains with a deviation angle of less than 15° accounts for more than 1.5%;

[0057] (8) Purification high temperature annealing;

[0058] (9) Applying insulation coating and flat annealing.

[0059] In the manufacturing method of the present invention, the morphology of the inhibitor can be adjusted during the intermediate annealing step (5), rather than during the conventional hot-rolled plate annealing process. This change can omit the hot-rolled plate annealing process and greatly reduce the difficulty of cold rolling.

[0060] In existing decarburized steel sheets of high magnetic induction oriented silicon steel, the number of Goss grains with a deviation angle of less than 15° accounts for less than 1.5% of the total number of grains. Thinning the strip thickness can lead to an insufficient number of effective Goss nuclei, which can adversely affect the magnetic properties of the product. The present invention, by adopting a double cold rolling process including a single cold rolling and a secondary cold rolling, can better control the primary recrystallization structure, texture, and primary inhibitor, making it easier to obtain a high proportion of Goss grains with a deviation angle of less than 15° in the decarburized steel sheet in step (7). This means that the present invention can increase the number of effective Goss nuclei, thereby solving the problem caused by thinning the strip thickness and improving the magnetic properties of the product.

[0061] Preferably, in step (2) of the manufacturing method of the present invention, the slab heating temperature is ≤1250°C.

[0062] Preferably, in step (4) of the manufacturing method of the present invention, the primary cold rolling adopts cold continuous rolling, and the reduction rate thereof is 50 to 75%.

[0063] Preferably, in step (6) of the manufacturing method of the present invention, the secondary cold rolling adopts cold continuous rolling, and the reduction rate thereof is 60 to 85%.

[0064] Although conventional reversible rolling can also be used in the cold rolling steps (4) and / or (6) of the present invention, continuous cold rolling is preferably used from the perspective of improving rolling efficiency and yield rate.

[0065] In addition, in the manufacturing method of the present invention, the cold rolling reduction ratio of the two cold rolling processes of step (4) and step (6) is adopted, which is conducive to the formation of fine and uniform recrystallized grains in the decarburized steel sheet and is also conducive to increasing the proportion of Goss grains. In addition, since the rolling efficiency and yield rate of cold rolling are significantly superior to reversible rolling, the overall cold rolling efficiency of the present invention is also significantly improved.

[0066] Preferably, in step (5) of the manufacturing method of the present invention, the intermediate annealing temperature is 900-1050°C.

[0067] In step (5) of the manufacturing method of the present invention, the total oxygen content of the steel sheet after annealing can be controlled to ≤600 ppm, and the carbon content can be controlled to ≥300 ppm. This facilitates stable production during the secondary cold rolling in step (6), promotes the formation of a strong γ texture that is beneficial to magnetic properties, and further facilitates the formation of complete secondary recrystallization. It should also be noted that the oxygen content and carbon content can be adjusted by methods known in the art.

[0068] Optionally, the manufacturing method of the present invention further comprises a hot-rolled plate annealing step after step (3) and before step (4), and the hot-rolled plate annealing temperature is ≤1000°C.

[0069] As described above, in the manufacturing method of the present invention, the hot-rolled plate can be directly cold-rolled without annealing after hot rolling, thereby reducing the process flow, improving production efficiency, and reducing production costs. However, in some embodiments, the hot-rolled plate can also be annealed after the hot rolling step, but the hot-rolled plate annealing temperature needs to be ≤1000°C. This is because when the hot-rolled plate annealing temperature is higher than 1000°C, it will cause the surface grains of the hot-rolled plate to coarsen, which is not conducive to the stable production of the subsequent single cold rolling in step (4).

[0070] Preferably, in step (7) of the manufacturing method of the present invention, the decarburization annealing temperature is 800-900°C, the decarburization annealing time is 80-170s, and the heating rate is 30-150°C / s.

[0071] Preferably, in step (7) of the manufacturing method of the present invention, the nitrogen content of the decarburized annealed plate after nitriding treatment is 160 to 260 ppm.

[0072] In the manufacturing method described herein, nitriding combines nitrogen with the existing aluminum in the steel to form secondary inhibitors consisting of finely dispersed particles such as AlN, (Al,Si)N, and (Al,Si,Mn)N. During the subsequent purification high-temperature annealing process, these secondary inhibitors work together with the primary inhibitors to promote secondary recrystallization.

[0073] The high magnetic induction oriented silicon steel of the present invention has the following advantages and beneficial effects compared with the prior art:

[0074] The suitable composition and process design of the high magnetic induction oriented silicon steel described in the present invention, for example, the use of a double cold rolling method to adjust the primary recrystallization structure, texture and primary inhibitor precipitation, can significantly reduce the annealing temperature of the hot-rolled plate or even omit the hot-rolled plate annealing, thereby realizing the efficient production of thin-gauge high magnetic induction oriented silicon steel with excellent magnetic properties by the cold continuous rolling method.

[0075] Compared to existing technologies, this invention solves the problems of rapid inhibitor ripening and insufficient number of effective Goss nuclei after strip thinning, thereby improving the magnetic properties of the final product. This allows the production of thin-gauge, high-magnetic-induction, oriented silicon steel without further thinning the hot-rolled sheet, thus avoiding a series of problems associated with producing thin-gauge hot-rolled steel on conventional hot-rolling lines. Furthermore, by eliminating hot-rolled sheet annealing, the efficient production of thin-gauge, high-magnetic-induction, oriented silicon steel using a continuous cold rolling process can be achieved, significantly reducing manufacturing costs.

[0076] In addition, the manufacturing method of the present invention also has the above advantages and beneficial effects. DETAILED DESCRIPTION

[0077] The high magnetic induction oriented silicon steel and the manufacturing method thereof according to the present invention will be further explained and illustrated below in conjunction with specific embodiments. However, such explanation and illustration do not constitute an undue limitation to the technical solution of the present invention.

[0078] First, various detection methods of the embodiments and comparative examples of this case are described as follows:

[0079] The average primary grain size is measured by first metallographically preparing the sample according to the standard described in GB / T 15125-2009, and then measuring and statistically analyzing it using the planimetric method in accordance with the standard described in GB / T 6394-2017.

[0080] The detection process for the fraction of Goss grains with a deviation angle less than 15° is as follows: first, the test sample is properly processed, then EBSD (electron backscatter diffraction) technology is used for detection, and the obtained data is screened and statistically analyzed to obtain the proportion of Goss texture components.

[0081] P of non-scored product steel 17 / 50 and B8 are obtained by using the method specified in standard GB / T 3655 to measure the magnetic properties of electrical steel sheets (strips) using the Epstein square ring.

[0082] P of scored product steel 17 / 50 and B8 are obtained by using the method specified in standard GB / T 13789 to measure the magnetic properties of electrical steel sheets (strips) using a single-piece tester.

[0083] Examples 1-12 and Comparative Examples 1-8

[0084] The high magnetic induction oriented silicon steels of Examples 1-12 and the comparative steels of Comparative Examples 1-8 were manufactured according to the following steps:

[0085] (1) Smelting and casting: Use converter or electric furnace for smelting and continuous casting into 230mm thick slabs.

[0086] (2) Heating the slab: Control the slab heating temperature to 1200°C and the heating time to 250 min.

[0087] (3) Hot rolling: Hot rolling is carried out to produce 2.3 mm hot rolled plates.

[0088] (4) Single cold rolling: A plate with a thickness of 0.75 mm was obtained by single cold rolling, and the reduction ratio of the single cold rolling was controlled to be 67.4%.

[0089] (5) Intermediate annealing: The open-coil continuous annealing method was adopted, the intermediate annealing temperature was controlled at 975°C, the intermediate annealing time was 120s, and the total oxygen content of the steel plate after intermediate annealing was obtained to be 261-594ppm, and the C element content was 308-939ppm.

[0090] (6) Secondary cold rolling: The secondary cold rolling yields a plate with a thickness of 0.19 mm, and the secondary cold rolling reduction is controlled to be 74.7%.

[0091] (7) Decarburization annealing: The decarburization annealing temperature is 835°C, the decarburization annealing time is 125s, and the heating rate is 115°C / s. The [C] content in the steel plate is reduced to below 50ppm, and the primary grain size and Goss grain number ratio shown in Table 2 are obtained.

[0092] (8) Nitriding treatment: Control the nitrogen content of the decarburized annealed plate to 190-250 ppm.

[0093] (9) Applying MgO coating: Applying MgO coating on the steel plate.

[0094] (10) Purification high temperature annealing: Purification annealing is carried out for 25 hours at a temperature of 1180°C in a conventional reducing atmosphere to reduce the [S] and [N] contents in the steel to below 50 ppm.

[0095] (11) Insulation coating and flat annealing: After insulation coating and hot stretching and flat annealing, the finished product with the chemical composition content shown in Table 1-1 and Table 1-2 is obtained.

[0096] Table 1-1. (wt%, the balance is Fe and other inevitable impurity elements except N, S, V, Ti)

[0097] Table 1-2 (wt%, the balance is Fe and other inevitable impurity elements except N, S, V, Ti)

[0098] Table 2

[0099] Combining Table 1-1, Table 1-2 and Table 2, it can be seen that the slab composition of the high magnetic induction oriented silicon steel of Example 1-12 of the present invention, the average primary grain size of the decarburized steel plate, and the proportion of the number of Goss grains with a deviation angle of less than 15° in the decarburized steel plate all meet the range defined in this application, so its iron loss P 17 / 50 All of them are lower than the benchmark iron loss calculated based on the following formula: 0.86 + 2 × plate thickness - 16 × Si, and the magnetic induction intensity B8 is higher than the benchmark magnetic induction calculated based on the following formula: 2.14 - 6.5 × Si. In contrast, the iron loss and / or magnetic induction of Comparative Examples 1-8 are inferior to the benchmark values ​​obtained by the above calculations.

[0100] Examples 13-18 and Comparative Examples 9-13

[0101] The high magnetic induction oriented silicon steels of Examples 13-18 and the comparative steels of Comparative Examples 9-13 were manufactured according to the following steps:

[0102] (1) Smelting and casting: Use converter or electric furnace for smelting and continuous casting into 230mm thick slabs.

[0103] (2) Slab heating: The slab heating temperature is controlled to 1140°C and the heating time is controlled to 200 min.

[0104] (3) Hot rolling: Rolled into 2.4 mm and 2.6 mm hot rolled plates as shown in Table 3-1.

[0105] (4) Cold-rolled sheets with a finished thickness of 0.18 mm were prepared according to the process shown in Table 3-1, wherein Examples 13-18 and Comparative Examples 11-13 adopted the double cold rolling preparation process described in the present invention, without annealing the hot-rolled sheets, and intermediate annealing was performed between the first cold rolling and the second cold rolling. The intermediate annealing adopted an open-coil continuous annealing method, and the intermediate annealing and its maximum temperature were controlled according to the process shown in Table 3-1, with an annealing time of 220 s. Comparative Examples 9-10 adopted a conventional single cold rolling preparation process, and the maximum annealing temperature of the hot-rolled sheets was controlled to 1150°C, and the annealing time was controlled to 250 s.

[0106] (5) Decarburization annealing: The decarburization annealing temperature is 835°C, the decarburization annealing time is 125s, and the heating rate is 115°C / s, reducing the [C] content in the steel plate to below 30ppm.

[0107] (6) Nitriding treatment: Control the nitrogen content of the decarburized annealed plate to 180-250 ppm.

[0108] (7) Applying MgO coating: Applying MgO coating on the steel plate.

[0109] (8) Purification high temperature annealing: Purification annealing is carried out for 20 hours at a temperature of 1200°C in a conventional reducing atmosphere to reduce the [S] and [N] contents in the steel to below 40 ppm.

[0110] (9) Insulation coating and flat annealing: After insulation coating and hot stretching and flat annealing, a finished product is obtained. The chemical composition of the finished product is: Si 3.22%, C 0.0016%, Als 0.0334%, N 0.0012%, Mn 0.088%, S 0.0013%, Ce 0.0243%, La 0.0202%, V 0.0025%, Ti 0.0015%.

[0111] Table 3-1

[0112] Table 3-2

[0113] As can be seen from Table 3-1 and Table 3-2, Examples 13-18 use the double cold rolling method of the present invention to prepare 0.17 mm oriented silicon steel, which can obtain a suitable primary grain size and a higher proportion of Goss grains with a deviation angle of less than 15° in the decarburized steel plate, resulting in a product with better magnetic properties and an iron loss P 17 / 50Both are lower than the benchmark iron loss of 0.705 W / kg calculated based on the formula 0.86 + 2 × plate thickness - 16 × Si, and the magnetic induction intensity B8 is higher than the benchmark magnetic induction of 1.931 T calculated based on the formula 2.14 - 6.5 × Si. Comparative Examples 9-10 used a conventional single-stage cold rolling method to prepare 0.17 mm oriented silicon steel, or Comparative Examples 11-13 used a double-stage cold rolling method but the intermediate annealing temperature did not meet the requirements of the present invention. The average primary grain size of the decarburized steel sheets obtained or the proportion of Goss grains with a deviation angle of less than 15° in the decarburized sheets did not meet the requirements of the present application, and the resulting iron loss and / or magnetic induction were inferior to the benchmark values ​​obtained by the above calculations.

[0114] Examples 19-22 and Comparative Examples 14-21

[0115] The high magnetic induction oriented silicon steels of Examples 19-22 and the comparative steels of Comparative Examples 14-21 were manufactured according to the following steps:

[0116] (1) Smelting and casting: Use converter or electric furnace for smelting and continuous casting into 230mm thick slabs.

[0117] (2) Slab heating: The slab heating temperature is controlled to 1190°C and the heating time is controlled to 160 min.

[0118] (3) Hot rolling: Hot rolling is carried out to produce 2.6 mm hot rolled plates.

[0119] (4) Single cold rolling: Single cold rolling to the thickness shown in Table 4-1.

[0120] (5) Intermediate annealing: The plate was annealed for 180 seconds using an open-coil continuous annealing method. The intermediate annealing temperature was controlled as shown in Table 4-1 to obtain the total oxygen content and C element content of the intermediate annealed plate shown in Table 4-1.

[0121] (6) Second cold rolling: Second cold rolling to a thickness of 0.15 mm.

[0122] (7) Decarburization annealing: The decarburization annealing temperature was controlled as shown in Table 4-1, the decarburization annealing time was 100 s, the heating rate was 80 °C / s, and the [C] content in the steel plate was reduced to below 30 ppm, obtaining the primary grain size shown in Table 2.

[0123] (8) Nitriding treatment: Control the nitrogen content of the decarburized annealed plate as shown in Table 4-1.

[0124] (9) Applying MgO coating: Applying MgO coating on the steel plate.

[0125] (10) Purification high temperature annealing: Purification annealing is carried out for 18 hours at a temperature of 1170°C in a conventional reducing atmosphere to reduce the [S] and [N] contents in the steel to below 50 ppm.

[0126] (11) Insulation coating and flat annealing: After insulation coating and hot stretching and flat annealing, a finished product is obtained. The chemical composition of the finished product is: Si 3.39%, C 0.0007%, Als 0.0275%, N 0.0017%, Mn 0.183%, S 0.0008%, Ce 0.1957%, V 0.0031%, Ti 0.0010%.

[0127] Table 4-1

[0128] Table 4-2

[0129] It can be seen from Table 4-1 and Table 4-2 that although Examples 19-22 and Comparative Examples 14-21 all adopt the double cold rolling method of the present invention to prepare 0.15 mm oriented silicon steel, the first cold rolling reduction rate, the second cold rolling reduction rate, the intermediate annealing temperature, the total oxygen content of the steel plate after the intermediate annealing, the C element content of the steel plate after the intermediate annealing, the nitriding amount of the decarburized steel plate, the average primary grain size of the decarburized steel plate and the proportion of the number of Goss grains in the decarburized steel plate of Examples 19-22 all meet the requirements of the present application, so their iron loss P 17 / 50 The values ​​of the iron loss and magnetic induction intensity B8 are all lower than the baseline iron loss of 0.618 W / kg calculated based on the formula 0.86 + 2 × plate thickness - 16 × Si, and the magnetic induction intensity B8 is higher than the baseline magnetic induction of 1.920 T calculated based on the formula 2.14 - 6.5 × Si. In contrast, the iron loss and / or magnetic induction of Comparative Examples 14-21 are inferior to the baseline values ​​calculated above.

[0130] Examples 23-29 and Comparative Examples 22-28

[0131] The high magnetic induction oriented silicon steels of Examples 23-29 and the comparative steels of Comparative Examples 22-28 were manufactured according to the following steps:

[0132] (1) Smelting and casting: Use converter or electric furnace for smelting and continuous casting into 230mm thick slabs.

[0133] (2) Slab heating: The slab heating temperature is controlled to 1250°C and the heating time is controlled to 120 minutes.

[0134] (3) Hot rolling: Hot rolling is performed to produce 2.5 mm hot rolled plates, and some of the hot rolled plates are annealed according to Table 5-1.

[0135] (4) Single cold rolling: The thickness of the steel sheet obtained by single cold rolling is 0.75 mm, and the reduction rate of the single cold rolling is controlled to be 70.0%.

[0136] (5) Intermediate annealing: Intermediate annealing was performed according to the intermediate annealing method, intermediate annealing temperature, and intermediate annealing time shown in Table 5. The uncoiled continuous annealing time was 220 s, and the coiled cover annealing time was 12 h. The total oxygen content of the sample after intermediate annealing was 350-450 ppm, and the C element content was 450-550 ppm.

[0137] (6) Secondary cold rolling: The thickness of the secondary cold rolling was 0.13 mm, and the secondary cold rolling reduction was controlled at 82.7%.

[0138] (7) Decarburization annealing: Control the heating rate, decarburization annealing temperature, and decarburization annealing time according to Table 5-1 to reduce the [C] content in the steel plate to below 30 ppm, and obtain the primary grain size and Goss grain ratio shown in Table 5-2.

[0139] (8) Nitriding treatment: Control the nitrogen content of the decarburized annealed plate to 200-230 ppm.

[0140] (9) Applying MgO coating: Applying MgO coating on the steel plate.

[0141] (10) Purification high temperature annealing: Purification annealing is carried out for 20 hours at a temperature of 1200°C in a conventional reducing atmosphere to reduce the [S] and [N] contents in the steel to below 30 ppm.

[0142] (11) Insulation coating and flat annealing: After insulation coating and hot stretching and flat annealing, a finished product is obtained. The chemical composition of the finished product is: Si 3.17%, C 0.0009%, Als 0.0254%, N 0.0019%, Mn 0.144%, S 0.0027%, La 0.0030%, V 0.0025%, Ti 0.0015%, Sn 0.065%, and Cu 0.12%.

[0143] Table 5-1

[0144] Table 5-2

[0145] It can be seen from Table 5-1 and Table 5-2 that although Examples 23-29 and Comparative Examples 22-28 all adopt the double cold rolling method of the present invention to prepare 0.13 mm oriented silicon steel, the hot rolled plate annealing and annealing temperature, intermediate annealing and intermediate annealing temperature, decarburization annealing heating rate, decarburization annealing temperature, decarburization annealing time, and the average primary grain size of the decarburized steel plate and the proportion of Goss grains in the decarburized steel plate of Examples 23-29 all meet the requirements of this case, so their iron loss P 17 / 50Both are lower than the benchmark iron loss of 0.613 W / kg calculated based on the formula 0.86 + 2 × plate thickness - 16 × Si, and the magnetic induction intensity B8 is higher than the benchmark magnetic induction of 1.934 T calculated based on the formula 2.14 - 6.5 × Si. In contrast, the iron loss and / or magnetic induction of Comparative Examples 22-28 are inferior to the benchmark values ​​obtained by the above calculations, and even have difficulty in rolling, resulting in strip breakage.

[0146] In addition, the present invention also uses a laser scoring method to refine the finished magnetic domains of the 0.15 mm finished samples in Examples 23-29 in Table 5-2, and the iron loss comparison results before and after scoring are listed in Table 6.

[0147] Table 6

[0148] It can be seen from Table 6 that the iron loss of each embodiment after notching is reduced compared with its original iron loss.

[0149] In summary, it can be seen that the high magnetic induction oriented silicon steel and its manufacturing method described in the present invention have significant advantages and beneficial effects compared with the existing technology, can improve product quality, reduce manufacturing costs and avoid common problems, and have good application prospects.

[0150] It should be noted that the composition design and manufacturing process described in the present invention are not only applicable to thin-gauge oriented silicon steel of 0.13-0.20 mm, but are also applicable to oriented silicon steel of conventional thickness, such as 0.23-0.30 mm. For oriented silicon steel of conventional thickness, the problem addressed by the present invention may be less prominent. However, since the manufacturing principles of oriented silicon steel of different thicknesses are similar, it can be assumed that the technical solution proposed in the present invention is also applicable to the production of oriented silicon steel of conventional thickness.

[0151] It should be noted that the combination of the various technical features in this case is not limited to the combination described in the claims of this case or the combination described in the specific embodiments. All technical features recorded in this case can be freely combined or combined in any way unless there is a contradiction between them.

[0152] It should also be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made therefrom that can be directly derived from or easily conceived by those skilled in the art based on the disclosure of the present invention are intended to fall within the scope of protection of the present invention.

Claims

1. An oriented silicon steel, which in addition to containing Fe and inevitable impurities, also contains chemical elements with the following mass percentages: C ≤ 0.005%; Si: 3.0 - 3.8%; Als: 0.010 - 0.035%; Mn: 0.05 - 0.20%; At least one selected from Ce and La, and satisfying Ce + La: 0.003 - 0.3%, preferably 0.0445 - 0.2433%; Among them, Among the inevitable impurity elements, N ≤ 0.005%, S ≤ 0.005%, V ≤ 0.005%, Ti ≤ 0.005%.

2. The grain-oriented electrical steel according to claim 1, characterized in that, The mass percentages of the chemical elements of the silicon steel are: C ≤ 0.005%; Si: 3.0 - 3.8%; Als: 0.010 - 0.035%; Mn: 0.05 - 0.20%; At least one selected from Ce and La, and satisfying Ce + La: 0.003 - 0.3%, preferably 0.0445 - 0.2433%; The balance is Fe and inevitable impurities; among the inevitable impurity elements, N ≤ 0.005%, S ≤ 0.005%, V ≤ 0.005%, Ti ≤ 0.005%.

3. The grain-oriented electrical steel according to claim 1 or 2, characterized in that, The silicon steel further contains at least one selected from the following chemical elements: P: 0.01 - 0.08%; Cr: 0.01 - 0.40%, Sn: 0.03 - 0.30%, Cu: 0.01 - 0.40%, 0 < Sb ≤ 0.1%, 0 < Bi ≤ 0.1%, 0 < Nb ≤ 0.1%, 0 < Mo ≤ 0.1%.

4. The grain-oriented electrical steel according to claim 1 or 2, characterized in that, The thickness of the silicon steel is 0.13 - 0.20 mm.

5. The grain-oriented electrical steel according to claim 1 or 2, characterized in that, The iron loss P of the silicon steel 17 / 50 ≤0.86 + 2×plate thickness - 16×Si, magnetic induction intensity B8 ≥ 2.14 - 6.5×Si, where the plate thickness is the thickness of the silicon steel sheet, in mm, Si is substituted with the mass percentage content of Si element, P 17 / 50 is in W / kg, and the unit of B8 is T.

6. The manufacturing method of the grain-oriented electrical steel according to any one of claims 1-6, characterized in that, Including the following steps: (1) Smelting and casting to obtain a slab; (2) Heating the slab; (3) Hot rolling; (4) First cold rolling (5) Intermediate annealing; (6) Second cold rolling; (7) Decarburizing annealing, nitriding treatment, coating an isolation agent coating, and the average primary grain size of the obtained decarburized annealed sheet is 6 - 18 μm, and the proportion of Goss grains with a deviation angle less than 15° is greater than 1.5%; (8) Purifying high - temperature annealing; (9) Coating an insulating coating and skin - pass annealing.

7. The manufacturing method according to claim 6, characterized in that, In step (2), the slab heating temperature ≤ 1250 °C.

8. The manufacturing method according to claim 6, characterized in that, In step (4), the first cold rolling uses tandem cold rolling, and its reduction ratio is 50 - 75%.

9. The manufacturing method according to claim 6, characterized in that, In step (5), the intermediate annealing temperature is 900 - 1050 °C, and the total oxygen content of the steel sheet after annealing ≤ 600 ppm, and the C element content ≥ 300 ppm.

10. The manufacturing method according to claim 6, characterized in that, In step (6), the second cold rolling uses tandem cold rolling, and its reduction ratio is 60 - 85%.

11. The manufacturing method according to claim 6, characterized in that, The manufacturing method further includes a hot - rolled sheet annealing step after step (3) and before step (4), and the hot - rolled sheet annealing temperature ≤ 1000 °C.

12. The manufacturing method according to claim 6, characterized in that, In step (7), the decarburizing annealing temperature is 800 - 900 °C, the decarburizing annealing time is 80 - 170 s, and the heating rate of temperature rise is 30 - 150 °C / s.

13. The manufacturing method according to claim 6, characterized in that, In step (7), the nitrogen content of the decarburized annealed sheet after nitriding treatment is 160 - 260 ppm.

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