Preparation method of low-temperature super-high magnetic induction oriented silicon steel and super-high magnetic induction oriented silicon steel

Abstract

The application relates to a preparation method of low-temperature super-high magnetic-induction oriented silicon steel and the super-high magnetic-induction oriented silicon steel, and belongs to the technical field of oriented silicon steel. At least one of the problems in the prior art, such as low magnetic-induction value of the oriented silicon steel, increased production cost and increased industrial production difficulty caused by the improvement of the magnetic induction, is solved. A preparation method of low-temperature super-high magnetic-induction oriented silicon steel comprises the steps of initial slab heating, hot rolling, normalizing, pickling, cold rolling, decarburization annealing, coating and high-temperature annealing. Compared with the traditional method, the application optimizes multiple key process links, reduces energy consumption and production cost, reduces the industrial production difficulty, and significantly improves the magnetic-induction value of the oriented silicon steel.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oriented silicon steel, in particular to a preparation method of low-temperature ultra-high magnetic induction oriented silicon steel and the ultra-high magnetic induction oriented silicon steel. BACKGROUND

[0002] As an important soft magnetic material, oriented silicon steel is widely used to make the core of various transformers due to its high magnetic induction in the rolling direction caused by the high proportion of / / RD texture. Among various transformers, low-frequency transformers are of great concern because they are used for frequency division power transmission in offshore power transmission mode. However, the current low-frequency (50 / 3Hz) transformers have the characteristics of large volume and heavy load loss, resulting in low energy utilization, which does not meet the development of "double carbon" in the new era. The magnetic induction of oriented silicon steel used for the core of low-frequency transformers is the key factor restricting the weight and volume of low-frequency transformers. The limit of the magnetic induction B 800 of commercial oriented silicon steel is 1.94T, which is difficult to reach 2.0T or above. Therefore, improving the magnetic induction of oriented silicon steel is the most important link in the application of low-frequency transformers, which is of great significance to promote the development of new energy technology. SUMMARY

[0003] In view of the above analysis, the present application aims to provide a preparation method of low-temperature ultra-high magnetic induction oriented silicon steel and the ultra-high magnetic induction oriented silicon steel, to solve at least one of the problems of low magnetic induction value of the oriented silicon steel in the prior art, increased production cost and increased difficulty of industrial production caused by the improvement of the magnetic induction.

[0004] The purpose of the present application is achieved by the following technical solutions:

[0005] The present application provides a preparation method of low-temperature ultra-high magnetic induction oriented silicon steel, which comprises the steps of initial slab-heating-hot rolling-normalizing-acid washing-cold rolling-decarburization annealing-coating-high temperature annealing; wherein,

[0006] Heating: the initial slab is reheated in an inert atmosphere protection furnace, the heating temperature is 1250℃-1350℃, and the heating time is 180-210min;

[0007] Hot rolling: the opening rolling temperature is ensured to be 650-1150℃, and the final rolling temperature is 600-1060℃;

[0008] Normalizing: the normalizing temperature is 500-1100℃, and the normalizing time is ≥5min;

[0009] Decarburization annealing: the temperature is 720-900℃, the time is 2-25min, the dew point temperature is controlled at 55-85℃, the atmosphere for decarburization annealing is hydrogen-nitrogen mixed atmosphere, and the volume content of H2 is 25%-60%;

[0010] Without nitriding treatment

[0011] High temperature annealing: the holding temperature of the high temperature annealing is 820-980℃.

[0012] Further, the raw material composition of the initial slab is, in mass percentage, Si: 0.5-2.0wt.%, 0

[0013] Further, the hot rolling starting temperature T K The content of C in the raw material composition of the initial slab [C] satisfies:

[0014] When 0 K ≤1150℃;

[0015] When 0.02wt.%≤[C]≤0.04wt.%, K ≤1000℃;

[0016] When 0.04wt.%≤[C]≤0.06wt.%, K ≤850℃.

[0017] Further, the hot rolling starting temperature T K satisfies the relationship between the finishing temperature T Z :

[0018] When 850℃ K ≤1150℃, T Z =T K - (90-110)℃;

[0019] When 650℃ K ≤850℃, T Z is 600-750℃, and T K ≥T Z .

[0020] Further, the process and parameters of the normalizing satisfy: K

[0021] When 750℃ K ​≤1150℃, a two-stage normalizing process is used, the temperature T C1 and time T m1 of the first-stage normalizing satisfy: T C2 of the second-stage normalizing satisfy: T m2 and time T C1 of the second-stage normalizing satisfy: T K - (40~50℃) to T K + (40~50℃), T C2 = T C1 - (95~105℃) and T m1 and T m2 are 2.5~3.0 min;

[0022] When 650℃≤T K <750℃, a one-stage normalizing process is used, the temperature T C and time T m of the one-stage normalizing satisfy: T C of the one-stage normalizing satisfy: T K - (100~110℃) to T K , T m ≥60 min.

[0023] Further, in the decarburization annealing, when 0.005wt.% < [C]≤0.06wt.%, the temperature T t and time T mt of the decarburization annealing satisfy:

[0024] T mt = -0.04×T t + (38~49)℃ and 720℃≤T t ≤900℃; T mt is in min; and / or,

[0025] the temperature T t of the decarburization annealing and dew point temperature T L satisfy:

[0026] T L = -0.16×T t + (190~200℃) and 720℃≤T t ≤900℃.

[0027] Further, in the decarburization annealing, the temperature T t of the decarburization annealing and dew point atmosphere V H2 satisfy:

[0028] V H2 = [lnT t - (6.2~6.3)]×100% and 720℃≤Tt ≤900℃; V H2 The volume percentage of hydrogen in the hydrogen-nitrogen mixed gas.

[0029] Further, when the C content [C] in the initial slab is ≤0.005 wt.%, the decarburization annealing step is replaced by a primary recrystallization annealing step, the temperature of the primary recrystallization annealing is 840-900℃, the time is 2-5 min, the H2 volume content is ≥20%, and water vapor is not needed to be introduced.

[0030] Further, the high-temperature annealing is sequentially divided into three stages:

[0031] The first stage is to raise the temperature from room temperature to a target temperature of 500-700℃ at a rate of 250-350℃ / h, and immediately enters the second stage without holding after reaching the target temperature of the first stage.

[0032] The second stage is to continue to raise the temperature to a target temperature of 820-980℃ at a rate of 10-20℃ / h, and immediately enters the third stage without holding after reaching the target temperature of the second stage.

[0033] The third stage is to hold at the target temperature of the second stage, i.e. the holding temperature of the high-temperature annealing, for 20h or more.

[0034] The present application provides an ultra-high magnetic induction oriented silicon steel for low-frequency transformers obtained by the preparation method described above.

[0035] Compared with the prior art, the present application can at least achieve one of the following beneficial effects:

[0036] (1) The preparation method of the oriented silicon steel of the present application optimizes multiple key process links compared with the traditional method, significantly reducing energy consumption and production cost. Specifically, the preparation of traditional oriented silicon steel usually requires high-temperature hot rolling, the lower limit of the opening rolling temperature is generally above 1050℃, and the lower limit of the final rolling temperature is also generally above 800℃. In addition, the normalizing annealing adopts high-temperature short-time (for example, ≤3 minutes) annealing, and needs to be treated with nitriding, and the holding temperature of high-temperature annealing under full hydrogen is generally higher than 1100℃.

[0037] In contrast, the preparation method of the present application reduces the opening rolling temperature and the final rolling temperature in the hot rolling process as a whole, and the process window of hot rolling is wider, the normalizing annealing adopts longer holding time at a lower temperature, and the nitriding treatment step is omitted, and the holding temperature of high-temperature annealing under full hydrogen is reduced to below 980℃. By reducing the process temperature and reducing the steps, the present application reduces energy consumption, reduces the difficulty and cost of industrial production, and improves production efficiency.

[0038] (2) In some preferred embodiments, from the perspective of component design, by controlling the alloying components of the initial slab within a specific range, combined with the optimized process flow, the magnetic induction of the oriented silicon steel is significantly improved, and B 800 ≥2.00T, providing stronger competitiveness for the application of oriented silicon steel in the field of low-frequency transformers.

[0039] The present application does not require the addition of expensive elements for the component control of the initial slab, and the content of some elements (C, Si) is significantly lower than that of existing oriented silicon steel, further reducing the raw material cost.

[0040] (3) In some preferred embodiments, by establishing a quantitative relationship between the opening temperature, finishing temperature of the hot rolling process and the carbon content in the initial slab, the temperature parameters in the hot rolling process are accurately controlled. This quantitative relationship ensures that the subsurface of the hot rolled plate can meet the requirements of Goss texture, so as to obtain Goss texture "seeds" with sufficient volume fraction, smaller orientation deviation and suitable morphology. Due to the heredity of Goss texture, these favorable texture characteristics are further amplified in the subsequent process, which is beneficial to ultimately achieve the technical breakthrough of high magnetic induction.

[0041] (4) In some preferred embodiments, by establishing a quantitative relationship between the opening temperature of the hot rolling process and the normalizing process temperature, the number of normalizing stages and specific parameters are accurately controlled. This quantitative relationship helps to avoid the occurrence of adverse evolution of hot rolling structure during normalizing process, ensures that the beneficial Goss texture "seeds" generated in the hot rolling process can be completely inherited to the subsequent process, and further optimized in the subsequent process, which is beneficial to ultimately achieve the technical breakthrough of high magnetic induction.

[0042] (5) In some preferred embodiments, by establishing a quantitative relationship between the decarburization annealing temperature, time, dew point temperature and dew point atmosphere, the synergistic effect of these parameters is achieved. This synergistic effect not only ensures that the carbon content is reduced to below 0.005wt%, but also takes into account the simplification of the process and the formation of the required decarburization structure. By accurately controlling these parameters, the present application can effectively promote the formation of Goss seeds, providing favorable conditions for further optimization of Goss texture in the subsequent process, which is helpful to ultimately achieve the technical breakthrough of high magnetic induction.

[0043] In particular, when the C content of the present application is as low as below 0.005wt%, the decarburization annealing step is replaced by the primary recrystallization annealing step, without the need for water vapor, which can achieve process simplification and cost reduction while ensuring high magnetic induction.

[0044] (6) In some preferred embodiments, by optimizing the high-temperature annealing process, a three-stage annealing process is adopted, and the holding temperature under full hydrogen is significantly reduced to below 980℃, and the long-time holding of each stage before full hydrogen annealing in the traditional process is omitted (after the first stage and the second stage are raised to the target temperature, there is no need for holding), and the overall high-temperature annealing time is significantly shortened. This improvement not only improves production efficiency and reduces energy consumption, but also ensures that the high-temperature annealing plate contains a high proportion of Goss texture with a small deviation angle by controlling the process parameters of each stage of high-temperature annealing, which enables the high magnetic induction of the oriented silicon steel to be maintained.

[0045] The various technical solutions described above can also be combined with each other in the present application to achieve more preferred combination solutions. Other features and advantages of the present application will be described in the subsequent specification, and some advantages will become apparent from the specification, or will be understood by implementing the present application. The purpose and other advantages of the present application can be achieved and obtained from the content specifically pointed out in the specification and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0046] The accompanying drawings are included to provide a further understanding of the embodiments, and are incorporated in and constitute a part of this specification, illustrate embodiments of the application, and together with the description serve to explain the principles of the application, and should not be considered limiting of the present application in any way. In the drawings:

[0047] Figure 1 Microstructure characterization map of the hot-rolled plate in the oriented silicon steel preparation method of embodiment 1 of the present application;

[0048] Figure 2 Inhibitor distribution map of the normalized plate in the oriented silicon steel preparation method of embodiment 1 of the present application;

[0049] Figure 3 Microstructure distribution map of the cold-rolled plate in the oriented silicon steel preparation method of embodiments 1 and 10 of the present application, (a) primary cold-rolled plate of embodiment 1, (b) secondary cold-rolled plate of embodiment 10;

[0050] Figure 4 Microstructure distribution longitudinal section map of the decarburization annealing plate in the oriented silicon steel preparation method of embodiment 1 of the present application;

[0051] Figure 5 Macroscopic metallographic structure map of the high-temperature annealing plate in the oriented silicon steel preparation method of embodiment 1 of the present application;

[0052] Figure 6 Microstructure map of the high-temperature annealing plate in the oriented silicon steel preparation method of embodiment 1 of the present application. DETAILED DESCRIPTION

[0053] The preferred embodiments of the present application will be described in detail below with reference to the drawings, wherein the drawings constitute a part of the present application and are used to explain the principles of the present application together with the embodiments of the present application, but are not used to limit the scope of the present application.

[0054] In the production process of oriented silicon steel, the control of process parameters at each process stage, and the design and control of raw material composition have an important influence on the magnetic properties of the product. In order to break through the technical bottleneck of B 800 ≥2.00T which is difficult to break through in current industrial production, the inventors design a full-process ultra-high magnetic induction oriented silicon steel preparation process based on the principles of metallurgy and metallography, aiming to break through the technical bottleneck of B 800 ≥2.00T, while significantly reducing the temperature environment of industrial production, reducing the addition of expensive elements, reducing production cost and process difficulty, and improving production efficiency.

[0055] In a first aspect, the present application discloses a preparation method of low-temperature ultra-high magnetic induction oriented silicon steel, which comprises the steps of initial slab-heating-hot rolling-normalizing-pickling-cold rolling-decarburization annealing-coating-high temperature annealing.

[0056] Specifically, the initial slab: the raw material composition of the initial slab is Si: 0.5-2.0wt.%, 0

[0057] Specifically, heating: the initial slab is reheated in an inert atmosphere protection furnace, and the heating temperature is 1250-1350℃, and the heating time is 180-210min. The above process control can ensure complete solid solution of the inhibitors AlN and MnS. If the temperature is too low, the inhibitor solid solution will be difficult, and if the temperature is too high, the inhibitor will be overburned. Illustratively, the heating temperature is 1250℃, 1260℃, 1270℃, 1280℃, 1290℃, 1300℃, 1310℃, 1320℃, 1330℃, 1340℃, 1350℃. The heating time is 180min, 185min, 190min, 195min, 200min, 205min, 210min. It can be understood that after the initial slab is heated, it is air-cooled to the opening temperature of hot rolling.

[0058] Specifically, hot rolling: ensure the opening rolling temperature of 650-1150℃, the finishing temperature of 600-1060℃; the above process control can ensure the hot rolling process in ferrite zone or two-phase zone, and can obtain ideal hot rolling structure. Exemplarily, the opening rolling temperature is 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, 1040℃, 1100℃, 1150℃. Exemplarily, the finishing temperature is 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, 1060℃.

[0059] Specifically, normalizing: the normalizing temperature is 500-1100℃, and the normalizing time is ≥5min; the above process control is mainly to promote the recovery of the structure of the hot-rolled plate to reduce the substructure, ensure the smooth progress of the cold rolling process, and more importantly, promote the re-dissolution of the inhibitor AlN. Exemplarily, the normalizing temperature is 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, 1100℃. The normalizing time is 5min, 10min, 15min, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min, 60min, 70min, 80min, 90min.

[0060] Specifically, decarburization annealing: the temperature is 720-900℃, the time is 2-25min, the dew point temperature is controlled at 55-85℃, the atmosphere of the decarburization annealing is hydrogen-nitrogen mixed atmosphere, and the H2 volume content is 25%-60%; the above process control is mainly to complete the primary recrystallization, obtain sufficient Goss seeds, and reduce the C content to below 0.005wt.%, so as to ensure that the subsequent high-temperature annealing is in the ferrite zone. Exemplarily, the decarburization annealing temperature is 720℃, 740℃, 760℃, 780℃, 800℃, 820℃, 840℃, 860℃, 880℃, 900℃; the time is 2min, 5min, 8min, 10min, 12min, 14min, 16min, 18min, 20min, 22min, 25min; the dew point temperature is 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃. The H2 volume content is 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%. It should be noted that the dew point temperature usually depends on the C content and the decarburization temperature. The higher the C content and the decarburization temperature, the lower the dew point. Compared with the traditional grain-oriented silicon steel, the dew point temperature provided by the present application is matched with the corresponding decarburization temperature. The decarburization temperature of the present application is lower than that of the prior art, and accordingly the dew point temperature is higher than that of the prior art.

[0061] Specifically, compared with the prior art, the present application does not need nitriding treatment after decarburization annealing. Unlike the conventional grain-oriented silicon steel which must be additionally treated by nitriding after decarburization annealing, the present application introduces an appropriate amount of AlsN inhibitor into the raw material composition at the smelting stage, and controls the subsequent key processes to make AlsN distribute in the steel in a finer, more dispersed and uniform manner; therefore, the present application only needs about 100 ppm of the inhibitor to replace the conventional requirement of 300 ppm, and achieves the effect of the conventional 300 ppm inhibitor. In the case of omitting the nitriding link, the final magnetic properties of the present application are more excellent than those of the prior art, B 800 Stable to reach 2.0T or more.

[0062] Specifically, the holding temperature of the high-temperature annealing is 820-980℃. The holding temperature of the high-temperature annealing of the conventional grain-oriented silicon steel is generally higher than 980℃. The present application significantly reduces the annealing temperature through process innovation, greatly reduces energy consumption, and still obtains higher magnetic induction than the prior art, realizing the synergistic breakthrough of "low-temperature annealing-high energy efficiency-high magnetic induction". Exemplarily, the holding temperature of the high-temperature annealing is 820℃, 850℃, 860℃, 880℃, 900℃, 920℃, 950℃ or 980℃.

[0063] In a preferred embodiment, the hot rolling has a starting rolling temperature T K The C content [C] in the raw material composition of the initial slab satisfies:

[0064] When 0≤[C]≤0.02wt.%, 1000℃ K ≤1150℃;

[0065] When 0.02wt.%<[C]≤0.04wt.%, 850℃ K ≤1000℃;

[0066] When 0.04wt.%<[C]≤0.06wt.%, 650℃ K ≤850℃.

[0067] It should be noted that according to the above relationship, the appropriate starting rolling temperature is controlled according to the C content, which can meet the requirement of the subsurface layer of the hot-rolled plate for the Goss texture in the microstructure, obtain Goss texture "seeds" with sufficient volume fraction, smaller orientation deviation and suitable morphology, the Goss texture has heredity, and the above-mentioned favorable Goss texture is amplified in the subsequent process, finally guarantees excellent magnetic properties, and obtains high magnetic induction.

[0068] In a preferred embodiment, the hot rolling has a starting rolling temperature T K and a finishing rolling temperature T Z satisfying the relationship:

[0069] When 850℃ < T K ≤ 1150℃, T Z = T K - (90~110)℃;

[0070] When 650℃ ≤ T K ≤ 850℃, T Z = 600℃~750℃, and T K ≥ T Z .

[0071] It should be noted that T K and T Z are mainly controlled to meet the hot rolling range, and different hot rolling ranges will result in different existing states of the hot rolling structure, especially the existing state (appearance, content, and orientation deviation angle) of the Goss structure in the subsurface layer. The Goss of the hot rolling plate determines the existing state of the Goss grain in the subsequent process, thereby affecting the macroscopic magnetic properties. Therefore, the present application controls the opening rolling temperature T K and the finishing temperature T Z to meet the above synergistic relationship, which is beneficial to improve the final magnetic properties and obtain high magnetic induction.

[0072] Through the control of the hot rolling process parameters in the above preferred embodiments (such as determining T K according to the C content, and determining T K according to T Z ), the hot rolling plate obtained after the hot rolling process has the following organizational texture characteristics:

[0073] The subsurface layer includes more than 10% of the Goss texture {110}<001>, and the structure is a mixture of equiaxed grains and fibrous structure; wherein the equiaxed grain accounts for 10~20%; the fibrous structure accounts for 80~90%.

[0074] Through the control of the hot rolling process parameters in the above preferred embodiments (such as determining T K according to the C content, and determining T K according to T Z ), in the hot rolling plate, the Goss texture {110}<001> with a deviation angle of 15° or less accounts for 4% or more of the full-thickness structure of the hot rolling plate, and the Goss texture {110}<001> with a deviation angle of 7° or less accounts for 2% or more of the full-thickness structure of the hot rolling plate. In addition, in the hot rolling plate, the Goss texture {110}<001> in the subsurface layer is located at 1 / 8~1 / 4 of the full thickness of the hot rolling plate, that is, measured inward from the upper and lower surfaces of the hot rolling plate, it is located in the range of 1 / 8 to 1 / 4 of the thickness.

[0075] It should be noted that T KBy satisfying the above-mentioned preferred relationship with [C], the subsurface structure of the hot-rolled plate can be a mixture of equiaxed crystals and flat, elongated transitional structures. This structure is beneficial to the inheritance of Goss, which can promote the retention of Goss in subsequent processes, thereby improving magnetic properties and obtaining higher magnetic induction. The flat, elongated transitional structure is a subtype of the fibrous structure. For example, the proportion of equiaxed crystals is 10-20%; the proportion of flat, elongated transitional structures is 80-90%.

[0076] In some embodiments, the hot-rolled sheet has a Goss texture {110} on the subsurface. <001> At 1 / 8 to 1 / 6 of the total thickness of the hot-rolled plate, i.e., measured inward from the upper and lower surfaces of the hot-rolled plate, within the range of 1 / 8 to 1 / 6 of the thickness; the deviation angle of the subsurface layer is within 15°. (Goss weave {110}) <001> It accounts for 5% or more of the total thickness microstructure of hot-rolled steel, of which the Goss texture with a deviation angle within 7° {110} <001> It accounts for 3% or more of the total thickness of the hot-rolled plate.

[0077] In one embodiment, during hot rolling, the rolling reduction rate for each pass is >30%, preferably 35%~50%, exemplarily 35%, 40%, 45%, and 50%; except for the last pass, the rolling reduction rate for the last pass is controlled at 20~30%, and the final rolled thickness is controlled at 2.0~2.3 mm. After hot rolling, the slab is slowly cooled in hot water at 70~80℃. The above-mentioned allocation of hot rolling passes is mainly for the uniform distribution of the microstructure during hot rolling. Slow cooling with hot water at a gentle rate suppresses AlsN coarsening and locks the Goss orientation on the surface of the hot-rolled slab, allowing it to be fully inherited and amplified, which helps to improve magnetic properties and obtain higher magnetic induction.

[0078] In a preferred embodiment, the normalization process and parameters are related to the initial rolling temperature T of the hot rolling process. K satisfy:

[0079] When 750℃≤T K For temperatures ≤1150℃, a two-stage normalization process is adopted, with the first stage normalization temperature T... C1 and time T m1 And the temperature T of the second normalization stage C2 and time T m2 Satisfy: T C1 The range is T K - (40~50℃) to T K + (40~50℃), T C2 =T C1 - (95~105℃) and T m1 and T m2 For example, T is 2.5~3.0 min; m1 and Tm2 Each value is independently selected, such as 2.5min, 2.6min, 2.7min, 2.8min, 2.9min, and 3.0min. Through the parameter control of the above two-stage normalizing process, the normalized plate obtained after normalization has the same microstructure as the hot-rolled plate, and the microstructure is clearer, but the grain size increases, that is, the microstructure of the subsurface layer and the central layer becomes flatter and thicker.

[0080] When 650℃≤T K <750℃, using a one-stage normalizing process, the one-stage normalizing temperature T C and time T m Satisfy: T C The range is T K - (100~110℃) to T K T m ≥60min. Preferably, T m For example, T... m The time intervals were 60 min, 70 min, 80 min, 90 min, and 100 min. By controlling the parameters of the above one-stage normalizing process, the texture of the normalized plate was almost identical to that of the corresponding hot-rolled plate, the microstructure was clearer, but the grain size remained almost unchanged.

[0081] It should be noted that the normalizing process is mainly to promote the recovery of the hot-rolled structure and facilitate the cold rolling process. The fine control of the normalizing process is related to the starting temperature of the hot rolling, and the two are matched to avoid the adverse evolution of the hot-rolled structure. This ensures that the beneficial Goss texture "seeds" generated by hot rolling are fully inherited and further optimized in subsequent processes, ultimately significantly improving the magnetic properties and obtaining high magnetic induction.

[0082] In one embodiment, in the two-stage normalizing process, air cooling is used between the first and second normalizing stages, followed by hot water cooling at 70-90°C after the second normalizing stage. Cooling with hot water at a suitable temperature prevents slab cracking during rolling and allows the slab to quickly pass through the nose temperature range for inhibitor precipitation, avoiding premature and excessive inhibitor precipitation and growth. The resulting fine, uniformly dispersed inhibitor provides uniform pinning in subsequent processes (e.g., high-temperature annealing), promoting secondary recrystallization to form a sharp Goss texture, enhancing magnetic properties (primarily magnetization), and resulting in more uniform and stable mechanical properties. Exemplarily, the hot water temperatures are 70°C, 75°C, 80°C, 85°C, and 90°C, which match the temperature of the second normalizing stage.

[0083] Specifically, the normalized plate obtained after normalization is cold-rolled after normal pickling. The cold rolling adopts a single cold rolling or double cold rolling process to cold roll the pickled plate to a finished thickness of 0.20~0.27mm.

[0084] In a preferred embodiment, in the first cold rolling process, the first pass cold rolling reduction is ≥ 30%, for example 30% ~ 50%, and the subsequent pass reductions are evenly distributed.

[0085] In a preferred embodiment, in the second cold rolling process, the first pass cold rolling reduction of the first rolling stage is ≥ 25%, for example 25% ~ 50%, and the subsequent pass reductions are evenly distributed, and the intermediate annealing is performed when the cold rolling thickness is 0.65 ~ 1.2 mm, and the intermediate annealing temperature T Zt and the intermediate annealing time T Zm satisfies:

[0086] When 700℃ < T Zt ≤ 1060℃, T Zm = -0.02 × T Zt + (22 ~ 24℃);

[0087] When 600℃ ≤ T Zt ≤ 700℃, T Zm = -0.2 × T Zt + (150 ~ 160℃);

[0088] The first pass cold rolling reduction of the second rolling stage is ≥ 26%, for example 26% ~ 50%, and the subsequent pass reductions are evenly distributed.

[0089] It should be noted that the above-mentioned preferred embodiment of the cold rolling process control is mainly to retain the Goss seeds, because the cold rolling process will "crush" the Goss structure retained by the hot rolling and normalizing process, therefore, a suitable cold rolling process can provide good conditions for the growth of Goss grains in the decarburization process, and the quality of the Goss "seeds" in the decarburization process directly affects the secondary recrystallization of Goss grains in the high-temperature annealing process, thereby promoting the improvement of magnetic properties.

[0090] For example, the intermediate annealing temperature in the second cold rolling process is consistent with the normalizing temperature (such as T C1 or T C ). Preferably, the reduction distribution of the first rolling stage and the second rolling stage of the second cold rolling process satisfies: the cumulative cold rolling reduction of the first rolling stage is ≤ 60%. For example, the thickness before cold rolling is 2.1 mm, and the cold rolling is performed twice: from 2.1 mm to 0.86 mm (the cumulative cold rolling reduction of the first rolling stage is 59%, which satisfies ≤ 60%, intermediate annealing, and then from 0.86 mm to 0.27 mm (the cumulative cold rolling reduction of the second rolling stage is 69%).

[0091] It should be noted that the primary cold rolling is mainly used to reduce the process flow and cost, or the secondary cold rolling is selected to ensure that relatively strong {111} texture is obtained in the cold rolling structure, so that more Goss seeds are obtained in the subsequent primary recrystallization, the probability of Goss secondary recrystallization is promoted, and the stability of the final magnetic performance is greatly improved.

[0092] In some embodiments, the cold rolling adopts the secondary cold rolling process without the normalizing step, and the hot rolling is directly followed by pickling, because the intermediate annealing in the secondary cold rolling process can replace the normalizing process and promote the resolubility of the inhibitor AlsN.

[0093] In some embodiments, the cold rolling adopts the primary cold rolling process, and the normalizing step is matched.

[0094] The combination of the cold rolling and the normalizing process can ensure the performance while adapting to different production lines, and provides flexibility for industrial production.

[0095] Through the parameter control (such as the reduction distribution and the intermediate annealing process parameter of the secondary cold rolling) of the cold rolling process in the preferred embodiments, the microstructure of the cold-rolled sheet obtained after the cold rolling process is fibrous structure, including 60% and above α-line texture.

[0096] In a preferred embodiment, in the decarburization annealing, when 0.005 wt.% < [C] ≤ 0.06 wt.%, the temperature T t and the time T mt satisfy:

[0097] T mt =-0.04×T t +(38~49)℃, and 720℃≤T t ≤900℃; the unit of T mt is min.

[0098] In a preferred embodiment, in the decarburization annealing, the temperature T t of the decarburization annealing and the dew point temperature T L satisfy:

[0099] T L =-0.16×T t +(190~200℃), and 720℃≤T t ≤900℃.

[0100] In a preferred embodiment, in the decarburization annealing, the temperature T t of the decarburization annealing and the dew point atmosphere V H2 satisfy:

[0101] V H2 =[lnT t -(6.2~6.3)]×100%, and 720℃≤T t ≤900℃; V H2 Example: The volume percentage of hydrogen in a hydrogen-nitrogen mixture.

[0102] It should be noted that, based on the above regarding T t T mt T L V H2 The coordinated control ensures that the C content is reduced to below 0.005 wt.% so as not to affect the high-temperature annealing process. On the other hand, matching the decarburization annealing temperature with the dew point atmosphere can obtain the desired decarburized structure, that is, promote the formation of Goss seeds, thereby promoting the enhancement of magnetization.

[0103] In a preferred embodiment, when the C content [C] in the initial slab is ≤0.005 wt.%, the decarburization annealing step is replaced by a primary recrystallization annealing step. The primary recrystallization annealing temperature is 840~900℃, the time is 2-5 min, the H2 volume content is ≥20%, and steam is not required. It is understood that this process is only for primary recrystallization, providing Goss seeds for secondary recrystallization, and does not involve a decarburization process. Exemplarily, the H2 volume content is 20%~70%. Exemplarily, the primary recrystallization annealing temperature is 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, the time is 2 min, 3 min, 4 min, 5 min; the H2 volume content is 20%, 30%, 40%, 50%, 60%, 70%.

[0104] It should be noted that when [C] ≤ 0.005 wt.%, the desired microstructure can be obtained by matching temperature and time, that is, promoting the formation of Goss seeds, thereby promoting the improvement of magnetism.

[0105] The decarburization annealing parameter T in the above preferred embodiments t T mt T L V H2 In the synergistic control of the decarburization annealing process, the average grain size of the slab obtained is 6-12 μm, and the proportion of Goss grains is 0.5%-7.0%.

[0106] In one embodiment, the temperature T under the single cold rolling condition and decarburization annealing t Satisfying 800℃≤T t At ≤900℃, the average grain size of the slab obtained after decarburization annealing is 8~10µm, and the proportion of Goss grains is 1%~1.5%.

[0107] In one embodiment, the temperature T of the decarburization annealing under the second cold rolling condition satisfies 720℃≤T t 720℃≤T t When T < 800℃, the average grain size of the slab obtained after the decarburization annealing is 6-8µm, and the proportion of Goss grains is 0.5%-1.0%.

[0108] In one embodiment, the temperature T of the decarburization annealing under the second cold rolling condition satisfies 720℃≤T t 720℃≤T t ≤900℃, the average grain size of the slab obtained after the decarburization annealing is 10-12µm, and the proportion of Goss grains is 2%-4%.

[0109] In one embodiment, the temperature T of the decarburization annealing under the second cold rolling condition satisfies 720℃≤T t 720℃≤T t ≤800℃, the average grain size of the slab obtained after the decarburization annealing is 8-10µm, and the proportion of Goss grains is 3%-7%.

[0110] In one preferred embodiment, the high-temperature annealing is sequentially divided into three stages:

[0111] In the first stage, the temperature is raised from room temperature to a target temperature of 500-700℃ at a rate of 250-350℃ / h, and immediately enters the second stage without holding after reaching the target temperature of the first stage; for example, the target temperature of the first stage is 500℃, 550℃, 600℃, 650℃, 700℃, preferably 600-700℃. The rate of temperature rise in the first stage is 250℃ / h, 270℃ / h, 290℃ / h, 310℃ / h, 330℃ / h, 350℃ / h, preferably 250-310℃ / h.

[0112] In the second stage, the temperature is continuously raised to a target temperature of 820-980℃ (i.e. the holding temperature of the high-temperature annealing) at a rate of 10-20℃ / h, and immediately enters the third stage without holding after reaching the target temperature of the second stage; for example, the target temperature of the second stage is 820℃, 840℃, 860℃, 880℃, 900℃, 920℃, 940℃, 960℃, 980℃, preferably 860-920℃. The rate of temperature rise in the second stage is 10℃ / h, 11℃ / h, 12℃ / h, 13℃ / h, 14℃ / h, 15℃ / h, 16℃ / h, 17℃ / h, 18℃ / h, 19℃ / h, 20℃ / h, preferably 10-15℃ / h.

[0113] The third stage is to keep the temperature at the target temperature of the second stage, i.e., the holding temperature of the high-temperature annealing, for 20 hours or more. Preferably, the third stage is kept for 20-40 hours, and the holding temperature of the high-temperature annealing is 860-920℃.

[0114] In some preferred embodiments, when the content of N in the raw material composition is 0.007-0.010 wt.%, the rate of temperature rise in the second stage is 17-20℃ / h; when the content of N in the raw material composition is 0.010-0.015 wt.%, the rate of temperature rise in the second stage is 15-17℃ / h; and when the content of N in the raw material composition is 0.015-0.020 wt.%, the rate of temperature rise in the second stage is 10-15℃ / h.

[0115] Illustratively, the temperature rising atmosphere in the first stage is pure nitrogen.

[0116] Illustratively, the temperature rising atmosphere in the second stage is ammonia or a mixture of hydrogen and nitrogen, wherein the volume fraction of hydrogen is ≥10%.

[0117] Illustratively, the holding atmosphere in the third stage is pure hydrogen.

[0118] Through the control of the parameters of the three-stage high-temperature annealing in the preferred embodiments, the Goss texture {110}<001> with a deviation angle within 15° accounts for more than 95% of the whole thickness of the high-temperature annealed plate, and the Goss texture {110}<001> with a deviation angle within 7° accounts for more than 85% of the whole thickness of the high-temperature annealed plate.

[0119] It should be noted that, through the control of the pre-process of the high-temperature annealing in the embodiments, as many Goss seeds as possible can be retained and inhibitors can be inhibited, and through the control of the high-temperature annealing process, the Goss seeds can be subjected to secondary recrystallization under the action of the inhibitors and become dominant, so that high magnetic induction can be finally obtained.

[0120] It should be noted that, in the preparation method of the embodiments, the components of the initial plate blank and the main process effects and mechanisms are as follows:

[0121] Si, the addition of Si in oriented silicon steel can increase the resistivity and reduce the iron loss, but will also reduce the magnetic induction, and too high Si content will lead to low magnetic induction B 800≥2.00T difficult to break through one of the important reasons. In order to break through the technical bottleneck of magnetic induction, the Si content is controlled at 0.5~2.0wt.% in the present application, and a certain amount of Si can also improve the toughness of the plate and improve the plate yield during rolling. Exemplarily, the Si content is 0.5wt.%, 0.6wt.%, 0.7wt.%, 0.8wt.%, 0.9wt.%, 1.0wt.%, 1.1wt.%, 1.2wt.%, 1.3wt.%, 1.4wt.%, 1.5wt.%, 1.6wt.%, 1.7wt.%, 1.8wt.%, 1.9wt.%, 2.0wt.%; preferably, the Si content is 0.8~1.2wt.% to ensure the optimized balance between processability and high magnetic induction.

[0122] C, the role of C in the oriented silicon steel is mainly to increase the austenite phase region and increase the solid solubility of inhibitors (AIN and MnS), and the C content in the embodiments of the present application is controlled at 0<C≤0.06wt.%, for example, the C content is controlled between 0.001~0.06wt.%; exemplarily, the C content is 0.001wt.%, 0.002wt.%, 0.005wt.%, 0.008wt.%, 0.010wt.%, 0.012wt.%, 0.014wt.%, 0.0145wt.%, 0.0148wt.%, 0.018wt.%, 0.02wt.%, 0.03wt.%, 0.04wt.%, 0.05wt.%, 0.06wt.%; preferably, 0.001wt.%≤C<0.015wt.%. The inhibitor of the oriented silicon steel in the present application is reduced by half compared with the prior art oriented silicon steel, so that the carbon (C) content can be further reduced.

[0123] Als and N, in order to obtain high proportion of Goss texture in the rolling direction in oriented silicon steel, generally need to add inhibitors, the common inhibitors are mainly AlN and MnS. Among them, with the increase of Al, N content, austenite + AlN phase zone expands, and the precipitation temperature of AlN gradually increases, resulting in poor resolubility of AlN, causing the loss of AlN. Therefore, the content of Als is controlled in 0.018~0.028wt.% and the content of N is controlled in 0.007~0.020wt.%. Exemplarily, the content of Als is 0.018wt.%, 0.019wt.%, 0.020wt.%, 0.021wt.%, 0.022wt.%, 0.023wt.%, 0.024wt.%, 0.025wt.%, 0.026wt.%, 0.027wt.%, 0.028wt.%. Preferably, the content of Als is 0.018~0.025wt.%; more preferably, the content of Als is 0.018~0.022wt.%. Exemplarily, the content of N is 0.007wt.%, 0.008wt.%, 0.009wt.%, 0.010wt.%, 0.011wt.%, 0.012wt.%, 0.013wt.%, 0.014wt.%, 0.015wt.%, 0.016wt.%, 0.017wt.%, 0.018wt.%, 0.019wt.%, 0.020wt.%. Preferably, the content of N is 0.010~0.018wt.%; more preferably, the content of N is 0.012~0.015wt.%.

[0124] Mn and S, with the increase of Mn and S content, its effect is similar to AlN, which can expand the austenite phase zone and cause the precipitation temperature to be too high, resulting in poor resolubility, therefore, the content of Mn is controlled in 0.03~0.08wt.% and the content of S is controlled in 0.003~0.008wt.% in the present application. In oriented silicon steel, the inhibition ability of AlN as inhibitor to particles is stronger than that of MnS, in the composition design process of the present application, Mn and S are controlled in the above range, combined with appropriate amount of Al and N, the excellent performance of oriented silicon steel is ensured under the condition of low element content. Exemplarily, the content of Mn is 0.03wt.%, 0.04wt.%, 0.05wt.%, 0.06wt.%, 0.07wt.%, 0.08wt.%; preferably, the content of Mn is 0.05~0.07wt.%. Exemplarily, the content of S is 0.003wt.%, 0.004wt.%, 0.005wt.%, 0.006wt.%, 0.007wt.%, 0.008wt.%; preferably, the content of S is 0.005~0.007wt.%.

[0125] Cu: add an appropriate amount of Cu, make the primary grain more small and uniform, the elongation ratio (length / width) of secondary grain <2, more like equiaxed shape, secondary recrystallization is more perfect, the magnetic property is improved, and is more stable, too high Cu content will lead to magnetic induction decline. Therefore, the Cu content is controlled at 0 < Cu < = 0.5wt.%. Exemplarily, the Cu content is 0.001~0.5 wt.%; as an example, the Cu content is 0.001wt.%, 0.002wt.%, 0.005wt.%, 0.008wt.%, 0.01wt.%, 0.02wt.%, 0.05wt.%, 0.08wt.%, 0.1wt.%, 0.2wt.%, 0.3wt.%, 0.4wt.%, 0.5wt.%; preferably, the Cu content is 0.001~0.3wt.%.

[0126] Sn+Sb+Bi: the three have the same effect, the three segregate along the grain boundary in the normalizing stage, adding an appropriate amount of Sn and / or Sb and / or Bi can inhibit the growth of precipitates, strengthen the inhibition ability, and at the same time make the distribution of inhibitors more uniform; too high Sn+Sb+Bi content leads to too strong inhibition ability, Goss texture cannot occur secondary recrystallization, resulting in magnetic induction decline. Therefore, the Sn+Sb+Bi content is controlled at 0 < Sn+Sb+Bi < = 0.10wt.%. Exemplarily, the sum of Sn+Sb+Bi content is 0.001wt.%~0.10wt.%. Sn+Sb+Bi is understood as adding one or more of Sn, Sb and Bi, and the sum of Sn, Sb and Bi content does not exceed 0.10wt.%. Exemplarily, the sum of Sn+Sb+Bi content is 0.001wt.%, 0.002wt.%, 0.005wt.%, 0.008wt.%, 0.01wt.%, 0.02wt.%, 0.05wt.%, 0.08wt.%, 0.1wt.%; preferably, the sum of Sn+Sb+Bi content is 0.001wt.%~0.05wt.%.

[0127] Mo: adding an appropriate amount of Mo is beneficial to improve the inhibition ability of inhibitors, prevent grain boundary oxidation and reduce the formation of FeS; too high Mo content leads to too strong inhibition ability, Goss texture cannot occur secondary recrystallization, resulting in magnetic induction decline. Therefore, the Mo content is controlled at 0 < Mo < = 0.01wt.%. Exemplarily, the Mo content is 0.001wt.%~0.10wt.%. As an example, the Mo content is 0.001wt.%, 0.002wt.%, 0.004wt.%, 0.006wt.%, 0.008wt.%, 0.01wt.%; preferably, the Mo content is 0.001wt.%~0.007wt.%.

[0128] Cr: adding appropriate amount of Cr can improve resistivity and improve mechanical properties, especially for the application of oriented silicon steel for low frequency transformer, the improvement of resistivity is beneficial to reduce eddy current loss, thereby reducing iron loss, improving efficiency and reducing heat, which is important for long-term stable operation and energy saving of low frequency transformer; too high Cr content will have negative impact on mechanical properties and magnetic properties. Therefore, the Cr content is controlled at 0 < Cr≤ 0.08wt.%. As an example, the Cr content is 0.001wt.%~0.08wt.%. Illustratively, the Cr content is 0.001wt.%, 0.002wt.%, 0.005wt.%, 0.008wt.%, 0.010wt.%, 0.015wt.%, 0.020wt.%, 0.025wt.%, 0.030wt.%, 0.035wt.%, 0.040wt.%, 0.045wt.%, 0.050wt.%, 0.055wt.%, 0.060wt.%, 0.065wt.%, 0.070wt.%, 0.075wt.%, 0.080wt.%; preferably, the Cr content is 0.001wt.%~0.05wt.%.

[0129] Ni: is a ferromagnetic element, adding appropriate amount of Ni can significantly expand the gamma zone, refine the hot-rolled plate grain, prevent the formation of secondary grains with inaccurate orientation later, and improve the magnetic properties; too high Ni content will have adverse effects on magnetic properties. Therefore, the Ni content is controlled at 0 < Ni≤ 0.15wt.%. As an example, the Ni content is 0.001wt.%~0.15wt.%. Illustratively, the Ni content is 0.001wt.%, 0.002wt.%, 0.005wt.%, 0.008wt.%, 0.01wt.%, 0.02wt.%, 0.05wt.%, 0.08wt.%, 0.10wt.%, 0.12wt.%, 0.15wt.%; preferably, the Ni content is 0.001wt.%~0.10wt.%.

[0130] In some embodiments, the raw material composition has [C]:[Si]≤1 / 10, [C] and [Si] representing the content of elements C and Si; preferably, [C]:[Si]≤1 / 100. The element Si can expand the ferrite region, and the element C expands the austenite region and inhibits the formation of ferrite. In the high-temperature annealing stage, the structure must be in the complete ferrite region, so increasing the content of Si and reducing the content of C can reduce the decarburization process and increase the temperature in the holding stage of high-temperature annealing, which is beneficial to the increase of the inhibitor content and the boundary control of the ripening process. If the ratio of [C]:[Si] is too large, both the decarburization process and the process control boundary of the magnetic property are reduced. For example, [C]:[Si]=1 / 1000, 1 / 500, 1 / 300, 1 / 200, 1 / 100, 1 / 80, 1 / 50, 1 / 20, 1 / 10.

[0131] In some embodiments, the raw material composition has [Mn]:[S]=7~14, [Mn] and [S] representing the content of elements Mn and S. Mn also belongs to the austenite region element, and a too high content (high ratio) will reduce the solid solubility of the element S, increase the heating temperature, and hinder the desulfurization effect in the high-temperature purification annealing; a too high content of S (low ratio) makes it difficult to remove S in the high-temperature annealing process, and hot brittleness is prone to occur during hot rolling. For example, [Mn]:[S]=7, 8, 9, 10, 11, 12, 13, 14.

[0132] In some embodiments, the raw material composition has [Als]:[N]=1~2.5, [Als] and [N] representing the content of elements Als and N; preferably, [Als]:[N]=1.5~2. A too high content of Als will deteriorate the quality of the bottom layer, form a too thick aluminum oxide layer, and affect the subsequent processing and coating quality; a too high content of N will make the casting prone to rising, and the product will have peeling and blistering defects. A too low content of Als and N will not form enough fine aluminum nitride (AlsN) after normalizing, which cannot effectively inhibit primary recrystallization, thereby leading to incomplete secondary recrystallization and a decrease in magnetic properties. By controlling [Als]:[N] within a suitable ratio range, the synergistic effect of the inhibitors can be better exerted to promote the improvement of magnetic properties. For example, [Als]:[N]=1.0, 1.25, 1.5, 1.75, 2.0, 2.25, 2.5.

[0133] In a second aspect, the present application provides an ultra-high magnetic induction oriented silicon steel for low-frequency transformers prepared by the preparation method of the first aspect.

[0134] It should be noted that the magnetic induction value B 800 ≥2.00T.

[0135] In low-frequency transformers, the impact of iron loss is relatively small, while high magnetic induction can significantly reduce the weight and volume of the transformer and improve energy utilization. This is because at low frequencies, hysteresis loss and eddy current loss are relatively small, and the impact of iron loss on transformer performance is limited. High magnetic induction value silicon steel can use smaller core cross-sectional area and fewer winding turns under the same magnetic flux demand, thereby significantly reducing the amount of material used, reducing the weight and volume of the transformer. At the same time, high magnetic induction can also reduce iron loss and resistance loss, improve the efficiency of the transformer, and reduce operating costs. These advantages make high magnetic induction oriented silicon steel an ideal material for low-frequency transformers, not only facilitating transportation and installation, but also reducing material usage, meeting the requirements of sustainable development.

[0136] The technical solutions of the present application are further described in detail below in combination with specific examples and comparative examples.

[0137] Example 1

[0138] The present embodiment provides a preparation method of low-temperature ultra-high magnetic induction oriented silicon steel, comprising:

[0139] initial slab-heating-hot rolling-normalizing-pickling-cold rolling-decarburization annealing-coating-high temperature annealing to obtain ultra-high magnetic induction oriented silicon steel;

[0140] The initial slab (cast slab) has the following chemical composition by mass percentage: Si: 0.5wt.%, C: 0.06wt.%, Als: 0.028wt.%, N: 0.007wt.%, Mn: 0.08wt.%, S: 0.003wt.%, Cu: 0.001wt.%, Bi: 0.001wt.%, Sn+Sb: 0.05wt.%, Mo: 0.001wt.%, Cr: 0.002wt.%, Ni: 0.005wt.%, and the rest is iron and inevitable impurity elements.

[0141] Heating: The initial slab is heated in a high-temperature furnace, and the heating temperature is 1350℃, and the heating time is 180min;

[0142] Hot rolling: The heated initial slab is hot rolled using a four-roll mill, the opening rolling temperature is 1040℃, the final rolling temperature is 900℃, and the final rolling thickness is a hot-rolled plate with a thickness of 2.2mm;

[0143] Normalizing: The hot-rolled slab is normalized, and a two-stage normalizing process is adopted, the first-stage normalizing temperature T C1 and time T m1 , and the second-stage normalizing temperature T C2 and time T m2 satisfy: T C1 =900℃, T C2=750℃ and T m1 =T m2 =3.5min; the first normalization stage and the second normalization stage are air-cooled, and after the second normalization stage, the temperature is cooled with 110℃ hot water;

[0144] Pickling: A conventional pickling process;

[0145] Cold rolling: The slab is cold rolled in one pass with a reduction rate of 23% in each pass, and the slab is cold rolled to a finished thickness of 0.27±0.005mm.

[0146] Decarburization annealing: The decarburization annealing temperature is T. t =720℃, heat preservation time T mt =25min, water bath with dew point temperature controlled at 70℃, dew point atmosphere V H2 =20%;

[0147] Coating: A barrier layer with magnesium oxide as the main component is applied to the above-mentioned decarburized annealed plate to prevent it from sticking during the high-temperature annealing process;

[0148] High-temperature annealing: The temperature is directly increased from room temperature to 980℃ at a rate of 100℃ / h, and held for 20 hours.

[0149] Stretching, leveling, and coating with insulating coating: High-temperature annealed plates are hot-stretched, leveled, and annealed, and then coated with an insulating coating to obtain ultra-high magnetic induction oriented silicon steel.

[0150] Examples 2 to 7 and Comparative Examples 1 to 5 were prepared using the same process as Example 1, except for the alloy composition of the initial slab, as shown in Table 1.

[0151] Table 1. Main alloy composition (wt.%) of the initial slabs of the Examples and Comparative Examples

[0152]

[0153] Examples 8 to 10, as well as Comparative Examples 6 and 7, have the same alloy composition as the initial slab in Example 1. The difference lies in the preparation process parameters, as shown in Table 2.

[0154] Table 2. Main process parameters of the examples and comparative examples (Group 1)

[0155]

[0156] The alloy composition of the initial slabs in Examples 11 to 13 is basically the same as that in Example 3. The difference lies in the preparation process parameters, as shown in Table 3.

[0157] Table 3. Main process parameters of the embodiments (second group)

[0158]

[0159] Examples 14-17 have substantially the same alloy composition as the initial slab of Example 6, except for the process parameters, as shown in Table 4.

[0160] Table 4 Main process parameters of examples and comparative examples (third group)

[0161]

[0162] Table 5 Performance results of examples and comparative examples

[0163]

[0164] From Figure 1 It can be seen that the sub-surface layer has fibrous Goss structure, which provides sufficient Goss "seeds" for the secondary recrystallization of Goss in the subsequent high-temperature annealing process.

[0165] From Figure 2 It can be seen that the normalizing plate has sufficient inhibitor particles, which ensures that the inhibitors can play a role in the high-temperature annealing process.

[0166] From Figure 3 It can be seen that the secondary cold-rolled structure is thicker in the thickness direction compared with the primary cold-rolled structure, which is beneficial to generate sufficient Goss "seeds" in the decarburization annealing structure.

[0167] From Figure 4 It can be seen that sufficient Goss "seeds" can be observed in the decarburization structure.

[0168] From Figure 5 and Figure 6 It can be seen that under the process conditions of the embodiments of the present application, Goss has secondary recrystallization and occupies the advantage, and finally obtains high magnetic induction.

[0169] The above describes only the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any changes or replacements easily thought of by those skilled in the art within the technical range disclosed by the present application should be covered in the protection scope of the present application.

Claims

1. A method for preparing low-temperature ultra-high magnetic induction oriented silicon steel, characterized in that, The preparation method includes the following steps: initial slab - heating - hot rolling - normalizing - pickling - cold rolling - decarburization annealing - coating - high temperature annealing; in, Heating: The initial slab is reheated in an inert atmosphere furnace at a temperature of 1250℃~1350℃ for 180~210 min; Hot rolling: Ensure an initial rolling temperature of 650~1150℃ and a final rolling temperature of 600~1060℃; Normalization: Normalization temperature is 500~1100℃, and normalization time is ≥5min; Decarburization annealing: temperature 720~900℃, time 2-25min, dew point temperature controlled at 55-85℃, decarburization annealing atmosphere is hydrogen-nitrogen mixed atmosphere, H2 volume content 25%~60%; No nitriding treatment required; High-temperature annealing: The holding temperature for high-temperature annealing is 820~980℃; Wherein, the initial rolling temperature T of the hot rolling K The C content [C] in the raw material composition of the initial slab satisfies: When 0 < [C] ≤ 0.02 wt.%, 1000℃ < T K ≤1150℃; When 0.02wt.% < [C] ≤ 0.04wt.%, 850℃ < T K ≤1000℃; When 0.04wt.% < [C] ≤ 0.06wt.%, 650℃ ≤ T K ≤850℃; The initial rolling temperature T of the hot rolling K With the final rolling temperature T Z The relationship between them is satisfied: When 850℃ < T K ≤1150℃, T Z =T K - (90~110)℃; When 650℃≤T K ≤850℃, T Z The temperature range is 600℃~750℃, and T K ≥T Z ; The normalization process and parameters are related to the initial rolling temperature T of the hot rolling process. K satisfy: When 750℃≤T K For temperatures ≤1150℃, a two-stage normalization process is adopted, with the first stage normalization temperature T... C1 and time T m1 And the temperature T of the second normalization stage C2 and time T m2 Satisfy: T C1 The range is T K - (40~50℃) to T K + (40~50℃), T C2 =T C1 - (95~105℃) and T m1 and T m2 For 2.5~3.0 minutes; When 650℃≤T K <750℃, using a one-stage normalizing process, the one-stage normalizing temperature T C and time T m Satisfy: T C The range is T K - (100~110℃) to T K T m ≥60min.

2. The preparation method according to claim 1, characterized in that, The raw material composition of the initial slab, by mass percentage, is as follows: Si: 0.5~2.0 wt.%, 0 < C ≤ 0.06 wt.%, Als: 0.018~0.028 wt.%, N: 0.007~0.020 wt.%, Mn: 0.03~0.08 wt.%, S: 0.003~0.008 wt.%, 0 < Cu ≤ 0.5 wt.%, 0 < Sn + Sb + Bi ≤ 0.10 wt.%, 0 < Mo ≤ 0.01 wt.%, 0 < Cr ≤ 0.08 wt.%, 0 < Ni ≤ 0.15 wt.%, with the remainder being Fe and unavoidable impurities.

3. The preparation method according to claim 2, characterized in that, The T m1 and T m2 The time is 2.6~2.9 min; the T m The time is 60-90 minutes.

4. The preparation method according to claim 2, characterized in that, In the decarburization annealing, when 0.005wt.% < [C] ≤ 0.06wt.%, the decarburization annealing temperature T t ℃ and time T mt satisfy: T mt =-0.04×T t + (38~49), and 720℃≤T t ℃≤900℃; T mt The unit is min.

5. The preparation method according to claim 2, characterized in that, In the decarburization annealing, when 0.005wt.% < [C] ≤ 0.06wt.%, the decarburization annealing temperature T t ℃ and dew point temperature T L satisfy: T L =-0.16×T t + (190~200)℃, and 720℃≤T t ℃≤900℃.

6. The preparation method according to claim 2, characterized in that, In the decarburization annealing, the temperature T of the decarburization annealing is... t ℃ and dew point atmosphere V H2 satisfy: V H2 =[lnT t -(6.2~6.3)]×100%, and 720℃≤T t ℃≤900℃; V H2 Example: The volume percentage of hydrogen in a hydrogen-nitrogen mixture.

7. The preparation method according to claim 2, characterized in that, When the C content [C] in the initial slab is ≤0.005wt.%, the decarburization annealing step is replaced by the primary recrystallization annealing step. The temperature of the primary recrystallization annealing is 840~900℃, the time is 2-5min, the H2 volume content is ≥20%, and there is no need to introduce water vapor.

8. The preparation method according to claim 2, characterized in that, The high-temperature annealing process is divided into three stages: In the first stage, the temperature is increased from room temperature to the target temperature of 500-700℃ at a rate of 250-350℃ / h. After reaching the target temperature of the first stage, the second stage is started immediately without heat preservation. In the second stage, the temperature continues to rise at a rate of 10-20℃ / h to the target temperature of 820-980℃. Once the target temperature of the second stage is reached, the third stage begins immediately without heat preservation. The third stage involves holding the material at the target temperature of the second stage, i.e., the high-temperature annealing temperature, for 20 hours or more.

9. An ultra-high magnetic induction oriented silicon steel for low-frequency transformers obtained by the preparation method according to any one of claims 1-8.

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