High magnetic induction grain-oriented silicon steel and its manufacturing method

Abstract

The present disclosure provides grain-oriented silicon steel containing, in addition to Fe and unavoidable impurities, the following chemical elements in mass percent: 0.035-0.120% C, 2.5-4.5% Si, 0.05-0.20% Mn, 0.005-0.05% P, 0.005-0.012% S, 0.015-0.045% Als, 0.003-0.010% N, 0.03-0.30% Sn, and 0.01-0.03% Mo. The grain-oriented silicon steel of the present disclosure has excellent magnetic induction properties. Furthermore, the present disclosure also provides a method for producing grain-oriented silicon steel. In the method of the present disclosure, by using an appropriate steel composition ratio in combination with specific normalizing annealing, decarburization, and nitriding processes, grain-oriented silicon steel products with stable and ultra-high magnetic induction are obtained, edge cracking is avoided, and product yield is greatly improved.

Description

[Technical Field]

[0001] The present disclosure relates to steel sheets and methods for manufacturing the same, and in particular to grain oriented silicon steels and methods for manufacturing the same. [Background technology]

[0002] For conventional grain-oriented silicon steel, there are two main manufacturing processes: high-temperature process (using MnS+AlN as inhibitor) and low-temperature process (AlN+nitriding).

[0003] In the high-temperature process, high-temperature HiB steel is produced using MnS and AlN as inhibitors, as well as normalizing and single-stage cold rolling. This manufacturing process is characterized by the requirement of a high slab heating temperature of as much as 1400°C during hot rolling, so that the MnS and AlN in the steel sheet completely dissolve into solid solution and then precipitate as fine and dispersed second-phase particles during the subsequent normalizing process. These particles serve as inhibitors for primary grain growth and promote the formation of large Goss grains through secondary recrystallization during high-temperature annealing, resulting in a high-magnetic-induction grain-oriented silicon steel product with high orientation and low core loss. However, high-temperature slab heating suffers from several drawbacks, including low yield, significant slag accumulation at the bottom of the furnace, reduced production, high energy consumption, shortened furnace life, high production costs, frequent surface defects, and unstable magnetic properties.

[0004] In the low-temperature HiB manufacturing process, the slab heating temperature can be reduced to 1150°C. Only a trace amount of Al is added during the steelmaking process, and nitriding is performed after decarburization annealing. The main feature of this process is that when decarburization annealing is performed at a low temperature, the inhibitor cannot be formed during hot rolling and normalizing because coarse sulfides and nitrides cannot dissolve in solid solution; instead, the inhibitor AlN is formed in the nitriding atmosphere after decarburization annealing. However, when using the low-temperature slab heating process, the amount of inhibitor is insufficient because AlN cannot completely dissolve in solid solution in the heated phase, and therefore secondary recrystallization cannot be fully achieved. For this reason, many manufacturers have investigated various methods to strengthen the inhibitor, improve secondary recrystallization, and / or improve the magnetic induction strength of grain-oriented silicon steel.

[0005] Furthermore, to shorten the manufacturing process, grain-oriented silicon steel can be produced using a thin slab continuous casting and rolling process. In this process, the cast slab is directly hot-rolled, thereby shortening the manufacturing process and saving energy. Producing grain-oriented silicon steel through the thin slab continuous casting and rolling process has advantages such as rapid slab solidification, low segregation, and finely dispersed inhibitors (MnS, AlN, etc.). However, hot-rolled silicon steel sheets often exhibit defects at the edges, such as hard nonmetallic slag and microcracks. Furthermore, during the subsequent cold-rolling process, the steel sheet not only withstands tensile and bending forces but also undergoes large plastic deformation. Defects can expand under such complex stress deformation, resulting in more serious cold-rolled edge cracks and even broken bands.

[0006] For this reason, in conventional hot rolling processes, measures are often adopted to prevent hot rolled edge cracking, including controlling the mass fraction of oxygen in the protective atmosphere and the residence time during slab reheating, as well as adjusting the rough reduction and rolling temperature, to achieve the purpose of reducing intergranular oxidation and refining the steel sheet grains, thereby reducing the occurrence of edge cracking.

[0007] Furthermore, a publication entitled "Method for Preventing Edge Cracking in Hot-Rolled Grain-Oriented Silicon Steel Under Low-Temperature Heating," published on July 2, 2021, under publication number CN113058998A, discloses that after the grain-oriented silicon steel cast slab enters the second heating section, rapid heating is performed at a heating rate of 15-30°C / min; the furnace gas temperature in the soaking section is controlled within the range of 1150-1180°C; the number of rolling passes during the rough rolling stage is not more than five; and the side pressure during rough rolling is ≥ 75 mm, with the side pressure of the vertical roller mill being ≥ 40 mm. This method employs a large side pressure to strengthen edge rolling, improve edge stress and strain, promote edge recrystallization, and refine grains, thereby effectively reducing hot-rolled edge cracking.

[0008] However, for the thin slab continuous casting and continuous rolling process, because the thickness of the slab is small, the deformation amount in rough rolling is relatively small, no vertical roller mill is formed, and the side pressure amount at the edge is very small. Therefore, the quality of the hot rolled edge is relatively poor, and edge trimming is often required before cold rolling, which still seriously affects the production efficiency and yield. Summary of the Invention

[0009] overview In view of the above-mentioned disadvantages in the prior art, one of the objects of the present invention is to provide a high magnetic induction grain oriented silicon steel having excellent magnetic induction properties while having a low crack rate in hot rolled coils, thereby greatly improving yield.

[0010] To achieve the above objectives, the present disclosure provides a method for producing a galvanic alloy comprising, in addition to Fe and unavoidable impurities, the following chemical elements in mass percent: C: 0.035-0.120%, Si: 2.5-4.5%, Mn: 0.05-0.20%, P: 0.005-0.05%, S: 0.005-0.012%, Als: 0.015-0.045%, N: 0.003-0.010%, Sn: 0.03-0.30%, and Mo: 0.01-0.03% The present invention provides a grain oriented silicon steel comprising:

[0011] In another aspect, the present disclosure also provides a composition comprising a composition having a chemical element content in mass percent of: C: 0.035-0.120%, Si: 2.5-4.5%, Mn: 0.05-0.20%, P: 0.005-0.05%, S: 0.005-0.012%, Als: 0.015-0.045%, N: 0.003-0.010%, Sn: 0.03-0.30%, Mo: 0.01-0.03%, and the balance being Fe and unavoidable impurities. The present invention provides a grain-oriented silicon steel.

[0012] Preferably, the grain oriented silicon steel according to the present disclosure further comprises at least one of the following chemical elements in mass percent: 0 <Cr≦0.30%; 0 <Cu≦0.3%; 0 <Nb≦0.01%; 0 <Bi≦0.05% include.

[0013] Preferably, the unavoidable impurities include V and Ti elements, and V≦0.01% and Ti≦0.01%.

[0014] Preferably, in the grain oriented silicon steel according to the present disclosure, the contents of the chemical elements in mass percent are as follows: C: 0.04~0.08%; Si: 3.0~4.0%; Mn: 0.08~0.18%; P: 0.005~0.040%; S: 0.006~0.010%; Als: 0.02-0.04%; N: 0.004~0.009%; Sn: 0.03~0.20%; Mo: 0.015~0.025%. At least one of the following is satisfied.

[0015] Preferably, the grain-oriented silicon steel according to the present disclosure has secondary recrystallized grains with an average grain size (average grain size D of the secondary recrystallized grains) of 20 mm or more.

[0016] Preferably, the grain oriented silicon steel according to the present disclosure has a magnetic induction B8 of ≧1.95T.

[0017] Preferably, the grain oriented silicon steel according to the present disclosure has a ratio of magnetic induction B8 to saturation magnetic induction Bs (B8 / Bs) of 0.98 or greater.

[0018] Preferably, the grain oriented silicon steel according to the present disclosure has an iron loss P of <1.00 W / kg. 17 / 50 It has.

[0019] Preferably, the grain oriented silicon steel according to the present disclosure has an untrimmed cold rolling ratio η of ≧90%.

[0020] In a further aspect, the present disclosure further provides a method for preparing a pharmaceutical composition comprising the steps of: (1) Smelting; (2) Thin slab continuous casting and rolling: slabs with a thickness of 60-70 mm, soaking the slabs at a temperature of 1100-1200 ° C, and soaking in a furnace for a period of 20-40 minutes; (3) Normalizing annealing: heating from room temperature to 900-1020°C and holding for 60 seconds or less; then cooling to 900-930°C within 15 seconds and holding for 60-120 seconds; then quenching in water at a cooling rate of 30-100°C / s; (4) cold rolling; (5) Decarburization annealing and nitriding treatment: adopting two-stage decarburization annealing, where in the first decarburization annealing stage, decarburization annealing is carried out at a temperature of 800-900°C for a period of 80-160 seconds at pH2O / pH2=0.4-0.75; in the second decarburization annealing stage, decarburization annealing is carried out at a temperature of 800-950°C for a period of 40-60 seconds at pH2O / pH2<0.4; and Carrying out nitriding treatment during the carburizing annealing process, wherein the nitriding is carried out at a temperature of 750-900°C for a period of 5-50 seconds, such that the molar ratio of the acid-soluble aluminum content to the nitrogen content (Als / [N]) of the steel sheet before secondary recrystallization satisfies: 1≦Als / [N]≦1.8, the nitriding atmosphere is NH3+H2+N2, and the volume percentage of NH3 in the nitriding atmosphere is 0.1-15%; (6) applying an MgO coating and performing high-temperature annealing; (7) Applying an insulating coating on the surface of the annealed plate, and performing hot drawing and leveling annealing to obtain grain-oriented silicon steel. The present invention provides a method for producing the grain-oriented silicon steel described above, comprising:

[0021] Preferably, in step (2), the molten steel has a superheat of 20 to 40° C. at a casting speed of 3 to 5 mpm.

[0022] Preferably, in step (2), the starting rolling temperature for the hot rolling is 1000 to 1150°C, and the finishing rolling temperature for the hot rolling is 850 to 1050°C.

[0023] Preferably, in step (2), laminar cooling is performed after rolling, and then coiling is performed, wherein the coiling is performed at a temperature of 650° C. or less. When coiling is performed at a temperature of 650° C. or less, it can be further ensured that no coarse precipitates are formed.

[0024] Preferably, in step (4), the cold rolling further comprises an intermediate annealing.

[0025] The grain-oriented silicon steel of the present disclosure is obtained based on thin slab continuous casting and rolling process, which effectively avoids the problem of hot-rolled coil cracking.

[0026] Through research, the inventors have found that the thickness of the slab has a significant effect on the size of precipitates after continuous casting and rolling. When the thickness of the slab is 60 to 70 mm, the equivalent diameter of the precipitates is relatively small. The slab of grain-oriented silicon steel prepared by the method of the present disclosure is thin, the cooling rate for casting is fast, and the precipitates are relatively few. The method of the present disclosure can effectively reduce cracking of hot-rolled coils and improve yield.

[0027] Furthermore, the specific normalizing annealing process of the present disclosure may result in the precipitation of fine inhibitors such as AlN, thereby increasing the amount of recrystallized grains in the hot-rolled sheet and making the texture distribution more rational.

[0028] The inventors discovered that in the prior art decarburization annealing process, when pH2O / pH2 is <0.4, a SiO2-rich oxide film forms, which inhibits decarburization. When pH2O / pH2 is 0.30-0.65, the decarburization effect is good, but the magnetic properties and glass film quality are poor. After extensive research, the method disclosed herein uses a two-stage decarburization annealing process: the first stage is at 800-900°C for 80-160 seconds at pH2O / pH2 = 0.4-0.75; and the second stage is at 800-950°C for 40-60 seconds at pH2O / pH2 <0.4. The two-stage decarburization annealing process disclosed herein achieves sufficient decarburization, improves the glass film quality, stabilizes secondary recrystallization, and refines secondary recrystallized grains, thereby improving the magnetic properties.

[0029] In the disclosed method, nitriding is performed during or after the decarburization annealing process to form beneficial inclusions. According to this specific nitriding method (nitriding temperature is 750-900°C, nitriding time is 5-50 seconds, nitriding atmosphere is NH3+H2+N2, and the volume percent of NH3 in the nitriding atmosphere is 0.1-15%), after nitriding is complete, the nitrogen that has penetrated into the surface of the steel sheet diffuses to form beneficial inclusions mainly composed of (Al,Si)N, which inhibit primary grain growth and prepare for secondary recrystallization so that the molar ratio of the acid-dissolved aluminum content to the nitrogen content of the steel sheet before secondary recrystallization, Als / [N], satisfies: 1≦Als / [N]≦1.8. Therefore, an ultra-high magnetic induction grain-oriented silicon steel product with B8≧1.95T can be obtained. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 shows the effect of slab thickness on precipitate size in grain oriented silicon steel of the present disclosure. [Figure 2] FIG. 2 shows the effect of the molar ratio of acid-soluble aluminum content to nitrogen content (Als / [N]) on the magnetic induction B8 of the grain-oriented silicon steel of the present disclosure before secondary recrystallization. DETAILED DESCRIPTION OF THE INVENTION

[0031] Detailed Description Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used in describing the present disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0032] In this description, the average diameter of secondary recrystallized grains is measured as described in the Examples section. Specifically, a single magnetic test sample is subjected to pickling to remove the surface coating and reveal the macrograins, and then photographed to obtain an image. The image of the secondary recrystallized grains is then processed using image processing software, and the circle-equivalent diameters of the secondary recrystallized grains in the image are obtained via the area method to calculate the average value of the circle-equivalent diameters of the secondary recrystallized grains, i.e., the average diameter of the secondary recrystallized grains.

[0033] In this description, magnetic induction B8 and B 25 is measured in accordance with GB / T 13789-2008 "Method for determination of magnetic properties of magnetic sheets and strips by single sheet tester"; and B 25 is defined as the saturation magnetic induction value Bs.

[0034] In this explanation, iron loss P 17 / 50 is measured using a 0.3mm thick sample in accordance with GB / T 13789-2008 "Method for determination of magnetic properties of magnetic sheets and strips by single sheet tester".

[0035] In this description, the no-trim cold rolling ratio η refers to the ratio of the number of hot rolled coils for direct use without trimming to the total number of hot rolled coils during cold rolling.

[0036] In this description, pH2O / pH2 refers to the partial pressure ratio of water to hydrogen in the atmosphere, which is obtained by measuring the dew point in the atmosphere, determining the moisture content, and calculating according to the hydrogen content.

[0037] In this description, when calculating the molar ratio of acid-soluble aluminum to the nitrogen content (Als / [N]) of a steel sheet before secondary recrystallization occurs, the nitrogen content is expressed as [N] because the nitrogen content of the steel sheet changes compared to the smelting components.

[0038] In the grain-oriented silicon steel of this disclosure, the design principles of each chemical element are explained as follows:

[0039] C: In the grain-oriented silicon steel of this disclosure, the main function of the C element is as follows: during the hot rolling process, the steel contains 20% to 30% γ phase, and the structure of the hot-rolled steel sheet can be refined through the γ⇔α phase transformation, and the microstructure of the hot-rolled steel sheet exhibits a specific structural gradient along the thickness direction of the steel sheet. That is, in the center of the steel sheet, the C content is relatively high and the grain structure is fine, while near the surface of the steel sheet, due to decarburization, the C content is low and the ferrite grains are coarse, which facilitates the formation of coarse and precisely oriented Goss grains along the rolling direction. However, the content of the C element in the steel should not be too high. If the C content in the steel is too high, not only will it be difficult to decarburize, but it will also lead to the presence of coarse carbides and troostite along the grain boundaries, resulting in an inhomogeneous structure and even the inability of secondary recrystallization to occur. Furthermore, C is also a major factor in causing magnetic aging. If the carbon content in the steel is too high and decarburization is incomplete, the carbon in the final product will dissolve interstitially in the ferrite lattice, which will generate a large stress field around the carbon atoms and significantly increase the magnetic hysteresis loss. Therefore, in the grain-oriented silicon steel of this disclosure, the mass percent of carbon element is controlled to be 0.035-0.120%.

[0040] In some preferred embodiments, the mass percentage of the C element is controlled to be 0.04-0.08%.

[0041] Si: In the grain-oriented silicon steel of this disclosure, the Si element can effectively reduce the iron loss of the final steel sheet. However, the Si element content in the steel should not be too high. If the Si element content in the steel is too high, the γ phase content drops sharply, making material processing difficult, and the microstructure of the hot-rolled steel sheet becomes coarse. As a result, the precipitated inhibitors are coarse, the amount of inhibitors decreases, the inhibitory power decreases, the primary recrystallized grains are coarse, the {110} pole density in the primary recrystallized structure decreases, and secondary recrystallization is difficult. Furthermore, if the Si element content in the steel is too high, the carbide particles precipitated after the normalizing process are coarse, which affects cold-rolling aging and decarburization annealing. Therefore, in the grain-oriented silicon steel of this disclosure, the mass percent of the Si element is controlled to be 2.5 to 4.5%.

[0042] In some preferred embodiments, the mass percentage of the Si element is controlled to be 3.0-4.0%.

[0043] Mn: In the grain-oriented silicon steel of this disclosure, the Mn element can prevent hot embrittlement of the hot-rolled sheet and can also combine with the S element to form MnS precipitates, ensuring fine and uniform primary recrystallized grains and promoting the development of secondary recrystallization. Furthermore, the Mn element can also effectively reduce the amount of C added to the steel, thereby expanding the γ-phase region in the steel and reducing the decarburization burden in subsequent processes. However, the manganese content in the steel should not be too high. If the Mn content in the steel is too high, it will cause the γ-phase to appear in subsequent processes and hinder the secondary recrystallization process. Therefore, in the grain-oriented silicon steel of this disclosure, the mass percent of the Mn element is controlled to be 0.05 to 0.20%.

[0044] In some preferred embodiments, the mass percentage of Mn element is controlled to be 0.08-0.18%.

[0045] P: In the grain-oriented silicon steel of this disclosure, the P element can effectively promote finer and more uniform primary recrystallized grains, while also increasing the ratio of {111} texture within the primary recrystallized grains and improving secondary recrystallization. However, if the P content in the steel is too high, the steel is brittle. Therefore, in the grain-oriented silicon steel of this disclosure, the mass percent of the P element is controlled to be 0.005-0.050%.

[0046] In some preferred embodiments, the mass percentage of the P element is controlled to be 0.005-0.040%.

[0047] S: It is generally believed that the content of S element in grain-oriented silicon steel produced by the nitriding process should be controlled to 0.007% or less. However, through research, the inventors have found that in the grain-oriented silicon steel of the present disclosure, when the S element content is <0.005%, not only is steelmaking difficult, but the magnetic properties of the final steel sheet are also affected. This is likely due to the formation of an insufficient amount of (Cu,Mn)S and the affected AlN precipitation. This is because there is a specific orientation relationship between AlN and (Cu,Mn)S: {2110}AlN / / {110}(Cu,Mn)S, where excessive or insufficient S content can affect the AlN precipitation morphology. Furthermore, the content of S element in steel should not be too high. When the S content in steel is >0.012%, secondary recrystallization is incomplete and linear crystals are likely to occur. Based on this, in the grain-oriented silicon steel of this disclosure, the mass percent of the S element is controlled to be 0.005 to 0.012%.

[0048] In some preferred embodiments, the mass percentage of the S element is controlled to be 0.006 to 0.010%.

[0049] Als and N: In the grain-oriented silicon steel of this disclosure, Als (acid-soluble aluminum) in the steel can combine with N to form AlN. AlN is the main inhibitor of grain-oriented silicon steel. To ensure sufficient magnetic properties, the acid-soluble aluminum content should be 0.015-0.045%, and the nitrogen content should be 0.003% or less. Furthermore, when the nitrogen content exceeds 0.010%, the casting tends to expand, resulting in peeling and blister defects in the product.

[0050] In some preferred embodiments, the mass percentage of Als is controlled to be between 0.02 and 0.04%, and the N content is controlled to be between 0.004 and 0.009%.

[0051] Mo: In the grain-oriented silicon steel of this disclosure, Mo is a key element for controlling edge cracking of hot-rolled sheets. The addition of Mo can reduce cracking of hot-rolled sheets. The enrichment of Mo in the surface of hot-rolled sheets can suppress grain boundary oxidation, form Mo3S3 near the surface, and prevent FeS formation, so that primary grain refinement is promoted and cracking at grain boundaries is prevented. Furthermore, the addition of Mo can also increase secondary nucleation sites, improve directional accuracy, and improve magnetic induction strength.

[0052] In some preferred embodiments, the mass percentage of the Mo element is controlled to be 0.015-0.025%.

[0053] Sn: In the grain-oriented silicon steel of this disclosure, Sn is a grain boundary segregating element. Adding an appropriate amount of Sn in steel can strengthen the inhibitory effect on grain growth, prevent premature denitrification and nitrogen incorporation during high-temperature annealing, promote complete secondary recrystallization, and improve the magnetic properties of the steel. Furthermore, in the grain-oriented silicon steel of this disclosure, Sn occupies the grain boundaries, hindering the diffusion of O in the steel and affecting the formation of the lower buried structure, which can deteriorate the quality of the lower layer. Therefore, the quality of the lower layer can be compensated for by adding Cr and Cu. Based on this, the mass percent of Sn in the grain-oriented silicon steel of this disclosure is controlled to be 0.03 to 0.30%.

[0054] In some preferred embodiments, the mass percentage of Sn element is controlled to be 0.03-0.20%.

[0055] In some preferred embodiments, the grain oriented silicon steel of this disclosure further comprises at least one of the following chemical elements in weight percent: 0 <Cr≦0.30%; 0 <Cu≦0.3%; 0 <Nb≦0.01%; 0 <Bi≦0.05% include.

[0056] Cr: In the grain-oriented silicon steel disclosed herein, adding an appropriate amount of Cr element can effectively promote oxidation during decarburization annealing, improve oxygen adhesion, and improve the quality of the lower layer. Based on this, the mass percent of Cr in the grain-oriented silicon steel disclosed herein is controlled to be 0.05-0.30%.

[0057] In some preferred embodiments, the mass percentage of the Cr element is controlled to be 0.08-0.28%.

[0058] Cu: In the grain-oriented silicon steel of this disclosure, the addition of Cu can increase the content of the γ phase, can appropriately reduce the content of C, and can lower the heating temperature of the slab. Furthermore, the addition of Cu, (Cu,Mn) x S or Cu x can precipitate S particles. (Cu,Mn) x S or Cu x The precipitation temperature of S is 80 °C to 100 °C lower than that of MnS, thereby helping to lower the heating temperature of the slab. Furthermore, the precipitated (Cu,Mn) x S or Cu x S is finer and more dispersed than MnS, and the precipitation amount also significantly increases. Therefore, the inhibitory force against grain growth is enhanced, and the secondary cold rolling reduction rate and the magnetic properties of the final product are improved. Furthermore, the addition of Cu can enhance the {110}<001>-oriented grains in the hot-rolled sheet and after decarburization annealing, can reduce the {100}<001>-oriented grains, and can promote secondary recrystallization. The addition of Cu can also reduce the deterioration of the glass film due to the addition of Sn or Sb. Based on this, in the grain-oriented silicon steel of this disclosure, the mass percentage of the Cu element is controlled such that 0 < Cu ≦ 0.3%.

[0059] In some preferred embodiments, in the grain-oriented silicon steel of this disclosure, the inevitable impurities include V and Ti, and V ≦ 0.01% and Ti ≦ 0.01%.

[0060] In the grain-oriented silicon steel of this disclosure, the inevitable impurities are mainly V and Ti. V and Ti are strong carbide or oxide-forming elements. When the contents of V and Ti are high, the decarburization annealing process is affected. Therefore, the contents of V and Ti must be controlled. Therefore, in the grain-oriented silicon steel of this disclosure, V ≦ 0.01% and Ti ≦ 0.01%.

[0061] In some preferred embodiments, V ≦ 0.008% and Ti ≦ 0.008%.

[0062] Furthermore, in some preferred embodiments, by adding Nb and Bi and controlling the contents of impurity elements V and Ti, the number of coarse MnS+AlN composite precipitates in the slabs with TiN, TiC and VN as nuclei can be greatly reduced.

[0063] In some preferred embodiments, the average size of the secondary recrystallized grains in the grain-oriented silicon steel of the present disclosure is 20 mm or greater.

[0064] In the grain oriented silicon steel of this disclosure, the resulting magnetic properties of the final grain oriented silicon steel product depend on the principle of secondary recrystallization, which results in a single Goss texture {110} <001> Secondary recrystallization refers to the phenomenon in which, after deformation, the metal is restricted by certain conditions (such as inhibitors and texture) so that most grains cannot grow normally during heating and recrystallization of the metal, and only a few grains (Goss grains) grow abnormally by consuming grains with other orientations. Only those Goss nuclei with a more precise orientation can grow and consume grains with other orientations by utilizing the size effect. The number of secondary recrystallized grains decreases, and the size of the secondary recrystallized grains increases, resulting in better magnetic properties for the steel.

[0065] The grain oriented silicon steel and its manufacturing method of the present disclosure have the following advantages and beneficial effects:

[0066] In the grain-oriented silicon steel of the present disclosure, by optimizing the chemical composition design of the steel, in particular by adding an appropriate amount of Mo element, the cracking of hot-rolled coils is effectively reduced so that the no-trimming cold-rolling ratio is 90% or more and the yield is improved.

[0067] In the present disclosure, the normalizing annealing, decarburization, and nitriding processes are adjusted so that the molar ratio of the acid-soluble aluminum content to the nitrogen content in the grain-oriented silicon steel before secondary recrystallization satisfies: 1≦Als / [N]≦1.8, the inhibition ability on the primary grains is enhanced, the average grain size D of the secondary recrystallized grains in the final product is ≧20 mm, and finally, a product with stable and ultra-high magnetic induction is obtained, where the product has a magnetic induction of B8≧1.95 T, a ratio of the magnetic induction B8 to the saturated magnetic induction value Bs, B8 / Bs, of ≧0.98, and P for the final product with a thickness of 0.3 mm. 17 / 50 It has an iron loss of <1.00 W / kg. [Example]

[0068] The grain-oriented silicon steel and its manufacturing method according to the present disclosure will be further explained and described below with reference to specific examples and the accompanying drawings, but the explanations and descriptions do not constitute undue limitations on the technical solutions of the present disclosure. The experimental methods, in which specific conditions are not specified in the examples, were carried out according to conventional conditions known in the art or conditions recommended by manufacturers.

[0069] Examples 1 to 18 and Comparative Examples 1 to 8 Table 1 lists the mass percentages of various chemical elements in the grain oriented silicon steels in Examples 1-18 and the comparative steels in Comparative Examples 1-8.

[0070] [Table 1]

[0071] The grain-oriented silicon steels in Examples 1 to 18 and the comparative steels in Comparative Examples 1 to 8 were prepared by the following steps (specific process parameters are shown in Tables 2-1, 2-2, and 2-3): (1) Producing steel in a converter or electric furnace and subjecting the molten steel to secondary refining; (2) thin slab continuous casting and rolling, followed by laminar cooling, and then coiling to obtain a 2.6 mm hot-rolled plate; (3) Normalizing annealing; (4) Cold rolling: the cumulative reduction rate in cold rolling is ≥ 88%, and a cold-rolled plate with a thickness of 0.3 mm is obtained; (5) Decarburization annealing and nitriding treatment; (6) Applying an MgO coating and performing high-temperature annealing in a bell furnace or tube furnace in an atmosphere of 100% H2 at a temperature of 1200°C for 20 hours; (7) Applying an insulating coating on the surface of the annealed plate, and performing hot drawing and leveling annealing to obtain grain-oriented silicon steel.

[0072] Tables 2-1, 2-2, and 2-3 list specific process parameters for the grain-oriented silicon steels in Examples 1-18 and the comparative steels in Comparative Examples 1-8.

[0073] [Table 2-1]

[0074] [Table 2-2]

[0075] [Table 2-3]

[0076] The final grain-oriented silicon steels in Examples 1 to 18 and the comparative steels in Comparative Examples 1 to 8 were sampled, observed, and subjected to various relevant performance tests. The obtained observations and test results are listed in Table 3.

[0077] The average diameter of the secondary recrystallized grains was measured as follows: a single magnetic test sample was subjected to pickling to remove the surface coating and reveal the macrograins, and then photographed to obtain an image. The image of the secondary recrystallized grains was then processed with image processing software, and the circle-equivalent diameters of the secondary recrystallized grains in the image were obtained via the area method to calculate the average value of the circle-equivalent diameters of the secondary recrystallized grains, i.e., the average diameter of the secondary recrystallized grains.

[0078] The parameters for magnetic properties were measured according to GB / T 13789-2008 "Method for determination of magnetic properties of magnetic sheets and strips by single sheet tester".

[0079] No-trimming cold rolling ratio η: The ratio of the number of hot-rolled coils used directly without trimming to the total number of hot-rolled coils during cold rolling.

[0080] Table 3 lists the observation results and performance test results for the grain-oriented silicon steels in Examples 1-18 and the comparative steels in Comparative Examples 1-8.

[0081] [Table 3]

[0082] As shown in Table 3, the magnetic induction B8 of the grain-oriented silicon steels in Examples 1 to 18 is significantly higher than that of the comparative steels in Comparative Examples 1 to 8, and the iron loss P 17 / 50 was significantly lower than that of the comparative steels in Comparative Examples 1 to 8. In the grain-oriented silicon steels in Examples 1 to 18, the average grain size of the secondary recrystallized grains was 20 mm or more, the magnetic induction B8 was ≧1.95 T, the ratio B8 / Bs of the magnetic induction B8 to the saturated magnetic induction value Bs was ≧0.98, and the iron loss P of the final product having a thickness of 0.3 mm was 17 / 50was <1.00 W / kg. Furthermore, the no-trim cold rolling ratio η for the grain-oriented silicon steels in Examples 1 to 18 was ≧90%, while the no-trim cold rolling ratio η for the comparative steels in Comparative Examples 1 to 8 was all below 90%.

[0083] It can be seen that the grain oriented silicon steels in Examples 1 to 18 not only achieve excellent magnetic properties but also avoid the problem of edge cracking.

[0084] FIG. 2 shows the effect of the molar ratio of acid-soluble aluminum content to nitrogen content (Als / [N]) on the magnetic induction B8 of the grain-oriented silicon steel of the present disclosure before secondary recrystallization.

[0085] From FIG. 2, it can be seen that when the molar ratio of acid-soluble aluminum to nitrogen content in the steel sheet before secondary recrystallization satisfies: 1≦Als / [N]≦1.8, a relatively high magnetic induction can be obtained.

[0086] It should be noted that the combination manner of the technical features in the present disclosure is not limited to the combination manner described in the claims or the combination manner described in the embodiments. All technical features described in the present disclosure can be combined or integrated in any way as long as there is no contradiction between them.

[0087] It should also be noted that the above-described embodiments are merely specific embodiments of the present disclosure. It is clear that the present disclosure is not limited to the above embodiments, and all similar variations or modifications that can be directly obtained or easily conceived by those skilled in the art from the contents disclosed in the present disclosure are intended to fall within the scope of the present disclosure.

Claims

1. 1. Grain-oriented silicon steel, which contains, in addition to Fe and unavoidable impurities, the following chemical elements in percent by mass: C: 0.035 to 0.120%, Si: 2.5 to 4.5%, Mn: 0.05 to 0.20%, P: 0.005 to 0.05%, S: 0.005 to 0.012%, Als: 0.015 to 0.045%, N: 0.003 to 0.010%, Sn: 0.03 to 0.30%, and Mo: 0.01 to 0.03% Including grain oriented silicon steel.

2. The content of chemical elements in weight percent in grain oriented silicon steel is as follows: C: 0.035 to 0.120%, Si: 2.5 to 4.5%, Mn: 0.05 to 0.20%, P: 0.005 to 0.05%, S: 0.005 to 0.012%, Als: 0.015 to 0.045%, N: 0.003 to 0.010%, Sn: 0.03 to 0.30%, Mo: 0.01 to 0.03%, and the balance being Fe and unavoidable impurities. The grain-oriented silicon steel according to claim 1,

3. The grain oriented silicon steel further comprises at least one of the following chemical elements in weight percent: 0<Cr≦0.30%; 0<Cu≦0.3%; 0<Nb≦0.01%; 0<Bi≦0.05% The grain-oriented silicon steel according to claim 1 or 2, comprising:

4. 3. The grain-oriented silicon steel according to claim 1, wherein the unavoidable impurities include V and Ti, and V≦0.01% and Ti≦0.01%.

5. The content of chemical elements in mass percent is: C: 0.04-0.08%; Si: 3.0-4.0%; Mn: 0.08-0.18%; P: 0.005-0.040%; S: 0.006-0.010%; Als: 0.02-0.04%; N: 0.004-0.009%; Sn: 0.03-0.20%; Mo: 0.015-0.025%. The grain-oriented silicon steel according to claim 1 or 2, which satisfies at least one of the following conditions.

6. 3. The grain-oriented silicon steel according to claim 1, wherein the grain-oriented silicon steel has secondary recrystallized grains having an average grain size of 20 μm or more.

7. Grain-oriented silicon steel has a magnetic induction B of ≥ 1.95T ８ , ≧0.98, magnetic induction B ８ the ratio of B to the saturated magnetic induction value Bs, B ８ / Bs, and iron loss P of <1.00 W / kg １７／５０ The grain-oriented silicon steel according to claim 1 or 2, having

8. 3. The grain-oriented silicon steel according to claim 1, wherein the grain-oriented silicon steel has an untrimmed cold rolling ratio η of ≥ 90%.

9. The following steps: (1) Smelting; (2) Thin slab continuous casting and rolling: a slab having a thickness of 60-70 mm, soaking the slab at a temperature of 1100-1200°C, and soaking in a furnace for a period of 20-40 minutes; (3) Normalizing annealing: heating from room temperature to 900-1020°C and holding for a period of 60 seconds or less; then cooling to 900-930°C within 15 seconds and holding for a period of 60-120 seconds; then water quenching at a cooling rate of 30-100°C / s; (4) Cold rolling. (5) Decarburization annealing and nitriding treatment: adopting two-stage decarburization annealing, where in the first decarburization annealing stage, the decarburization annealing is performed at pH ２ O / pH ２ = 0.4 to 0.75, at a temperature of 800 to 900°C for a period of 80 seconds to 160 seconds; in the second decarburization annealing step, the decarburization annealing is carried out at a pH of ２ O / pH ２ and performing a nitriding treatment during the decarburization annealing process, wherein the nitriding is performed at a temperature of 750-900°C for a period of 5-50 seconds, and the nitriding atmosphere is NH 4, so that the molar ratio of the acid-soluble aluminum content to the nitrogen content of the steel sheet before secondary recrystallization satisfies: 1≦Als / [N]≦1.

8. ３ +H ２ +N ２ and NH in a nitriding atmosphere ３ wherein the volume percentage of is 0.1 to 15%; (6) applying an MgO coating and performing a high temperature anneal; (7) Applying an insulating coating on the surface of the annealed plate, and then performing hot drawing and leveling annealing to obtain grain-oriented silicon steel. A method for producing the grain-oriented silicon steel according to any one of claims 1 to 8, comprising:

10. 10. The method of claim 9, wherein in step (2), the molten steel has a superheat of 20 to 40°C at a casting speed of 3 to 5 mpm.

11. 10. The method according to claim 9, wherein in step (2), the starting rolling temperature for the hot rolling is 1000 to 1150°C, and the finishing rolling temperature for the hot rolling is 850 to 1050°C.

12. 12. The method according to claim 11, wherein in step (2), laminar cooling is performed after rolling and then coiling is performed, wherein the coiling is performed at a temperature of 650°C or less.

13. 10. The method of claim 9, wherein in step (4), the cold rolling further comprises an intermediate anneal.

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