Method for preparing low-temperature high-magnetic-induction oriented silicon steel by rapid heating decarburization annealing

Abstract

The application discloses a method for preparing low-temperature high-magnetic-susceptibility oriented silicon steel through rapid heating decarburization annealing, and the oriented silicon steel is cast into a blank after smelting, heated at 1080-1180 DEG C, and then hot-rolled; after the hot-rolled coil is pickled to remove the surface oxide layer, normalizing annealing is carried out; after the normalizing is completed, the steel coil is cold-rolled through one-time pressing, the finished product thickness is d, and the cold-rolling reduction range is 88.4% to 91.0%; the cold-rolled coil is subjected to continuous decarburization and nitriding annealing, the rolling direction iron loss value P R13 / 50 of the steel strip in the continuous annealing process is detected and adjusted; magnesium oxide annealing release agent is coated, high-temperature annealing is carried out, tension coating is coated, and tension leveling is carried out; the application utilizes the relationship between the iron loss value of the low-temperature oriented silicon steel decarburization annealing plate and the nitrogen content after the decarburization annealing to on-line control the stability of the decarburization annealing nitriding amount, controls the transverse and longitudinal difference ratio I0 of the iron loss value of the low-temperature oriented silicon steel decarburization annealing plate to be within a proper range, and finally produces the low-temperature high-magnetic-susceptibility oriented silicon steel product with excellent magnetism.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically relating to a method for preparing low-temperature high-magnetic-induction oriented silicon steel. Background Technology

[0002] Grain-oriented silicon steel is the most widely used magnetic steel material in the world, and its characteristics are {111} <001> The primary grains undergo secondary recrystallization, resulting in unusually long grains with dimensions exceeding centimeters. The preferred arrangement of the Gaussian texture enhances the lattice structure. <001> The shortest axes, most easily magnetized, are concentrated along the rolling direction, giving grain-oriented silicon steel a high magnetic flux density in the cold-rolling direction. Utilizing the magnetic properties of grain-oriented silicon steel in different directions, it is widely used in the manufacture of transformer cores. The magnetic properties of grain-oriented silicon steel sheets have a significant impact on transformer efficiency, losses, and operational stability. Using high-grade, high-magnetic-induction silicon steel sheets to manufacture transformer cores allows for a wider range of magnetic flux density designs. This allows for a smaller cross-sectional area of ​​the transformer core, resulting in a reduction in transformer size and weight. The costs of manufacturing, transporting, and assembling the transformer are also reduced. Higher grades of silicon steel sheets also reduce no-load and operating losses, significantly lowering energy losses during power transmission and transformation. High magnetic flux density and low iron loss are two indispensable aspects of high-quality grain-oriented silicon steel products. In short, using high-grade grain-oriented silicon steel sheets to manufacture transformers offers higher overall economic benefits. In particular, the issuance of the national standard "Minimum Allowable Values ​​of Energy Efficiency and Energy Efficiency Grades of Power Transformers GB20052-2020" in 2020 will drive a surge in demand for high-end grades of grain-oriented silicon steel products due to the mandatory upgrade of high-efficiency transformers.

[0003] The more accurate the Gaussian texture orientation of the grains in a grain-oriented silicon steel product, the higher its magnetic induction and the lower its iron loss. From a manufacturing process perspective, grain-oriented silicon steel production methods are divided into high-temperature hot-rolled slab heating technology (heating temperature typically above 1300℃), medium-temperature slab heating technology (heating temperature between 1200℃ and 1300℃), and low-temperature slab heating technology (heating temperature typically below 1200℃). The low-temperature slab heating method, due to the significantly reduced temperature of the hot-rolling furnace, effectively solves or reduces metallurgical production problems in grain-oriented silicon steel production, such as excessive iron oxide scale, low yield, high equipment wear, high fuel consumption, and numerous surface defects. This aligns with the national steel industry's low-carbon and environmentally friendly strategy and represents a major trend in current technological development.

[0004] Grain-oriented silicon steel is a low-carbon iron-silicon alloy. The grain growth during decarburization annealing using low-temperature slab technology is called "primary recrystallization," characterized by predominantly equiaxed ferrite grains. Precipitates formed in the steel matrix after steelmaking alloying can hinder the growth of primary recrystallized grains. Due to its compositional design, low-temperature grain-oriented steel produces fewer precipitates after steelmaking alloying compared to traditional high-temperature steel, thus weakening the inhibition of primary recrystallization growth. Therefore, low-temperature high-magnetic-induction grain-oriented silicon steel exhibits larger grain sizes during decarburization annealing compared to traditional high-temperature steel, resulting in more coarse grains. The inhomogeneity of the primary grains directly affects the occurrence and completeness of abnormal secondary recrystallization growth. Inhomogeneous primary grains lead to uneven secondary recrystallization areas, and the larger, coarser primary grains are difficult to be absorbed by the abnormally grown Gaussian grains, ultimately resulting in an uneven and imperfect Gaussian texture, leading to poor magnetic properties in the product.

[0005] The initial recrystallization process consists of two stages: grain nucleation and recrystallization growth. During the heating process of a metallic material, the higher the heating rate, the more nuclei are formed, resulting in more grains that are finer and more uniform. After recrystallization nucleation, the higher the heat treatment temperature, the larger the final grain size. During heat treatment, the heating rate achievable for steel strips under conventional equipment conditions is typically below 100℃ / s. To reduce grain coarsening and obtain a highly uniform grain structure, various equipment and methods have been developed to increase the heating rate, such as electromagnetic induction heating, pulsed current heating, and infrared radiation heating. The maximum heating rate for steel strips can even reach approximately 1000℃ / s.

[0006] The application of high-speed heating technology to improve the mechanical properties and microstructure uniformity of steel materials is widespread, but its application in the production of grain-oriented silicon steel is still very limited. Currently, the focus is mainly on controlling the initial recrystallization texture during the decarburization process after cold rolling through rapid heating. For example, Japanese Patent Application Publication No. 2003-3215 shows that by using different heating rates to promote a texture intensity value I{111} / I{411} less than 3 in the initial grains, that is, increasing the proportion of {411} facet grains in the initial recrystallization, the magnetic properties of the product can be improved. However, the process of detecting the initial recrystallization texture of grain-oriented silicon steel is very cumbersome. Furthermore, because low-temperature high-magnetic-induction grain-oriented silicon steel lacks inherent inhibitory elements, the initial grains are more prone to coarsening during decarburization annealing. Therefore, controlling the uniformity of the initial grains in low-temperature slab manufacturing of grain-oriented silicon steel is more difficult and more critical to the magnetic properties of the product. The use of high-speed heating during decarburization annealing creates a humid atmosphere that affects the formation rate of the inner oxide layer in cold-rolled steel sheets, increasing the difficulty of controlling the degree of oxidation and also affecting the adhesion of the final insulating coating.

[0007] Furthermore, to ensure stable secondary recrystallization, the nitrogen and oxygen content of the samples need to be tested after decarburization and nitriding continuous annealing to guarantee the stability of the product's magnetic properties. This process is an intermediate testing process. Since these chemical tests are post-testing and require a certain amount of time, process adjustments are typically made after the tests are completed, affecting timeliness. Summary of the Invention

[0008] To address the problems of difficulty in controlling the initial recrystallization growth and microstructure during the decarburization annealing process in the production of low-temperature oriented silicon steel, and the cumbersome chemical detection process for the key material parameter nitrogen content after annealing, this invention utilizes the relationship between the iron loss value of the decarburized annealed plate of low-temperature oriented silicon steel and the nitrogen content after decarburization annealing to control the stability of the nitriding amount during decarburization annealing online. Furthermore, it employs a rapid heating production technology for decarburization annealing to ensure that the transverse and longitudinal difference ratio I0 of the iron loss value of the decarburized annealed plate of low-temperature oriented silicon steel is within a suitable range. This achieves stable and efficient decarburization annealing production while controlling the initial recrystallization microstructure to achieve a good state, ultimately producing low-temperature high-magnetic-induction oriented silicon steel products with excellent magnetic properties.

[0009] To achieve the above objectives, the following technical solution is adopted:

[0010] A method for preparing low-temperature high-magnetic-induction oriented silicon steel by rapid heating decarburization annealing includes the following steps:

[0011] 1) After smelting, grain-oriented silicon steel is cast into billets, which are then heated at 1080-1180℃ and hot-rolled.

[0012] 2) After the hot-rolled coil is pickled to remove the surface oxide layer, it undergoes normalizing annealing;

[0013] 3) After normalization, the steel coil is cold rolled once to a thickness of d (unit, mm), and the cold rolling reduction rate ranges from 88.4% to 91.0%.

[0014] 4) Cold-rolled coils undergo continuous decarburization and nitriding annealing. The rolling iron loss value P of the steel strip during continuous annealing is... R13 / 50 Testing was conducted, and P was adjusted by controlling the unit ammonia consumption (N) in the nitriding process. R13 / 50 The following detection range is achieved:

[0015] 2.996+2.428×d-10.78×[Si]≤P R1.3 / 50 ≤3.008+2.605×d-11.15×[Si]; (Formula 1)

[0016] Wherein, the ammonia consumption N is the amount of ammonia required per unit weight of steel strip for annealing per unit time (hour), in m³. 3 / (kg·h); d is the finished product thickness in mm; [Si] is the mass percentage of Si in the grain-oriented silicon steel;

[0017] 5) Apply magnesium oxide annealing release agent, anneal at high temperature, apply tension coating, and stretch to flatten.

[0018] According to the above scheme, the composition and weight percentage of the oriented silicon steel in step 1 are as follows: C: 0.036%~0.065%, Si: 3.05~3.46%, Als: 0.0256~0.0325%, Mn: 0.076~0.094%, N: 0.0065~0.0086%, S: ≤0.005%, Cu: ≤0.01%, Ti+Nb: ≤0.002%, and the remainder is Fe and unavoidable inclusions.

[0019] According to the above scheme, the heating rate v of continuous annealing in step 4 is 150℃ / s~350℃ / s, and the annealing temperature range is 820℃~825℃.

[0020] According to the above scheme, step 4 involves adjusting the rolling iron loss value P. R13 / 50 During the process, when the rolling iron loss value increases by P R13 / 50 When N = 0.01 W / kg, the ammonia conditioning amount N during decarburization and nitriding annealing is... P＝0.01 =0.00491+0.0339×d (Formula 2); where d is the thickness of the finished product in mm.

[0021] According to the above scheme, after decarburization and nitriding annealing in step 4, the transverse iron loss value of the steel coil is defined as P. N13 / 50 Its relationship with rolling iron loss value P R13 / 50 The ratio of horizontal to vertical differences satisfies 1.213 ≤ I o ≤1.297 (Formula 3); where

[0022] This invention employs a significantly faster heating technology than conventional annealing in the continuous decarburizing and nitriding annealing process of low-temperature grain-oriented silicon steel, with heating rates reaching 150℃ / s to 350℃ / s. This improves production efficiency and enhances the primary recrystallization microstructure. By increasing the heating rate during the decarburizing annealing process, the release of cold-rolled energy stored in the cold-rolled steel strip under low-temperature conditions is shortened, promoting the most uniform nucleation of the primary recrystallization microstructure. The increased amount of recrystallization nuclei during the decarburizing annealing heating process, along with smaller and more uniform primary recrystallized grain sizes, is beneficial for the subsequent high-temperature annealing secondary recrystallization. Simultaneously, the rapid heating reduces the formation of unfavorable oxide layers caused by slow heating of the grains at low temperatures, improving product surface quality.

[0023] According to formula (1), the rolling iron loss value P of cold-rolled steel strips of different specifications and thicknesses after continuous decarburization, nitriding and annealing is controlled. R13 / 50The range is due to the rolling iron loss value P after the initial recrystallization of grain-oriented silicon steel. R13 / 50 The iron loss value is inversely proportional to the grain size of the material during initial recrystallization; the larger the grain size, the smaller the iron loss value. The silicon content [Si] and the cold-rolled thickness d also have an inversely proportional effect on the iron loss value. The iron loss value can be kept within a suitable range according to formula (1), and the influence of silicon content [Si] and cold-rolled thickness d can be removed, thereby controlling the grain size and nitriding amount during initial recrystallization within a suitable range.

[0024] The reason why this invention adjusts the rolling iron loss value P according to formula (2) is that R13 / 50 The magnitude of the value is due to the amount of nitriding in the material after continuous decarburization and nitriding annealing, which affects the rolling iron loss value P. R13 / 50 The size has a significant impact, specifically manifested as a direct proportional relationship as shown in formula (2), that is, the higher the nitriding amount of the steel strip, the higher the rolling iron loss value P. R13 / 50 The higher the value, the better. Adjusting the ammonia dosage during continuous decarburization and nitriding annealing processes according to this relationship can improve the rolling iron loss value P during the initial recrystallization of different specifications of grain-oriented silicon steel. R13 / 50 It meets the requirements of formula (1), achieves the nitriding target, and reduces the chemical testing procedures for materials.

[0025] The reason for this invention is to measure the rolling iron loss value P of steel strip after continuous decarburization and nitriding annealing. R13 / 50 And transverse iron loss value P N13 / 50 The testing is conducted primarily because, as mentioned earlier, the initial recrystallization grain size, nitriding amount, and iron loss of the material after continuous annealing are correlated. Testing the iron loss value allows for stable control of the nitriding amount. Secondly, oriented silicon steel, after continuous annealing, becomes an ultra-low carbon steel with a carbon content not exceeding 30 ppm. Its initial recrystallization structure consists of single ferrite grains with a body-centered cubic crystal lattice and distinct crystal planes and short axes. <001> shorter axis <011> and long axis <111> The arrangement of crystals affects magnetic conductivity, thus influencing iron loss in the steel strip. This arrangement is termed texture in materials science. Primary recrystallization texture exhibits strong γ-type texture characteristics, meaning that the {111} planes of most grains are parallel to the rolling surface. However, due to the texture characteristics formed by primary recrystallization after continuous annealing following a single high-reduction cold rolling process, the shorter axes of the crystals in the rolling direction are affected by energy storage. <001> and relatively short axis <011> The proportion is relatively large, while the short axis in the transverse direction is relatively perpendicular to the rolling direction. <001> Fewer, shorter shaft <011> Long axis <111> and <112> The presence of numerous such arrangements results in a lower transverse magnetic permeability compared to the rolling direction. When the material reaches 1.3T at 50Hz, the transverse iron loss P... N15 / 50 Too high. This applies to the rolling iron loss value P. R13 / 50 And transverse iron loss value P N13 / 50Testing allows for the evaluation of grain size uniformity in both orientations. Under conventional processes, the transverse iron loss value of the steel strip is typically about 1.15 times that in the longitudinal direction. However, in this invention, the high-speed heating technology used in the decarburization annealing process promotes the uniformity of the primary grain structure, resulting in smaller recrystallized grain sizes and a lower rolling iron loss value P. R15 / 50 And transverse iron loss value P N15 / 50 The iron loss values ​​of materials produced using conventional techniques are all increased. Furthermore, due to the faster and more uniform nucleation of primary grains during rapid heating, grains with {111} and {110} crystal planes are more easily formed due to their higher energy storage. <100> With more RD arrangement in the rolling direction, the iron loss in the rolling direction is reduced, resulting in a higher iron loss value in both the transverse and longitudinal directions of the steel strip compared to conventional methods. Therefore, the difference ratio I0 between the transverse and longitudinal iron loss of the primary recrystallized steel strip under the technology of this invention falls within the range described in formula (3). The rolling direction iron loss value P after continuous decarburization and nitriding annealing in this invention... R13 / 50 And transverse iron loss value P N13 / 50 Distribution characteristics are shown in the diagram. Figure 1 As shown.

[0026] Compared with the prior art, this invention detects the online iron loss value of steel strip after continuous decarburizing and nitriding annealing, and utilizes its iron loss value P. R1.3 / 50 The relationship between the amount of nitriding and the amount of nitriding can reduce chemical testing procedures and control the amount of nitriding within a suitable range in a timely and stable manner. At the same time, the decarburizing and nitriding annealing process adopts rapid heating, and by controlling the difference ratio of iron loss in the transverse and longitudinal directions of the steel strip, it promotes the primary recrystallization structure to reach an excellent state, thereby achieving excellent performance of low-temperature oriented silicon steel products and high efficiency in the production process. Attached Figure Description

[0027] Figure 1 The present invention relates to the amount of ammonia gas used in continuous decarburizing and nitriding annealing and the rolling iron loss value P after annealing. R13 / 50 The relationship.

[0028] Figure 2 The rolling iron loss value P after continuous decarburization, nitriding, and annealing according to this invention R13 / 50 And transverse iron loss value P N13 / 50 Distribution diagram. Detailed Implementation

[0029] The following embodiments further illustrate the technical solution of the present invention, but are not intended to limit the scope of protection of the present invention.

[0030] A specific embodiment provides a method for preparing low-temperature high-magnetic-induction oriented silicon steel by rapid heating decarburization annealing:

[0031] 1) The composition and weight percentage of the applicable steel are as follows: C: 0.036%~0.065%, Si: 3.05~3.46%, Als: 0.0256~0.0325%, Mn: 0.076~0.094%, N: 0.0065~0.0086%, S: ≤0.005%, Cu: ≤0.01%, Ti+Nb: ≤0.002%, with the remainder being Fe and unavoidable inclusions.

[0032] 2) After smelting and continuously casting the billet according to the above composition, heat it at a temperature of 1080-1180℃, and then perform conventional hot rolling.

[0033] 3) After the hot-rolled coil is pickled to remove the surface oxide layer, it undergoes conventional normalizing annealing.

[0034] 4) After normalization, the steel coil is cold rolled once to the finished thickness d (unit, mm), and the cold rolling reduction rate ranges from 88.4% to 91.0%.

[0035] 5) Cold-rolled coils undergo continuous decarburization and nitriding annealing. The heating rate v for continuous annealing is 150℃ / s to 350℃ / s, and the annealing temperature range is 820℃ to 825℃. The rolling iron loss P of the steel strip during continuous annealing is... R13 / 50 Testing was conducted; based on the test results, the rolling iron loss value of the steel coil after decarburization and nitriding annealing was defined as P. R13 / 50 The rolling iron loss value P is adjusted by controlling the unit ammonia gas consumption N in the nitriding process online. R13 / 50 The following detection ranges are achieved:

[0036] 2.996+2.428×d-10.78×[Si]≤P R1.3 / 50 ≤3.008+2.605×d-11.15×[Si];

[0037] In the continuous decarburizing and nitriding process, the amount of ammonia gas required per unit weight of steel strip for annealing per unit time (hour) is defined as the unit ammonia gas consumption N, and the unit is m. 3 / (kg·h). Figure 1 The amount of ammonia gas used in nitriding and nitriding annealing during continuous decarburization and nitriding annealing in this invention, and the rolling iron loss value P after annealing. R13 / 50 The relationship between the iron loss value and the ammonia content of different specifications of oriented silicon steel strips can be used to adjust the iron loss value P. R13 / 50 The effect is within the target range.

[0038] When the rolling iron loss value increment P R13 / 50 When N = 0.01 W / kg, the ammonia conditioning amount N during decarburization and nitriding annealing P＝0.01 The unit ammonia consumption N can be adjusted according to the following formula to make P R13 / 50 The requirements are met;

[0039] N P＝0.01 =0.00491+0.0339×d, where d is the thickness of the finished product.

[0040] After decarburizing and nitriding annealing, the transverse iron loss value of the steel coil is defined as PN13 / 50, and its transverse-to-longitudinal difference ratio with the rolling direction iron loss value PR13 / 50 is I. o Satisfying 1.213≤I o ≤1.297. Figure 2 The rolling iron loss value P after continuous decarburization and nitriding annealing in this invention is... R13 / 50 And transverse iron loss value P N13 / 50 The distribution diagram shows that the initial recrystallization of the same specification grain-oriented silicon steel after decarburization and nitriding is smaller and more uniform, the iron loss value is increased and the difference between the transverse and longitudinal directions is greater than that of conventional technology, thus achieving the goal of controlling the texture of secondary recrystallization.

[0041] 6) Routine post-processing steps include applying magnesium oxide annealing release agent, final high-temperature annealing, applying tension coating, and stretching and leveling.

[0042] The chemical composition of each embodiment and comparative example in the specific implementation is shown in Table 1.

[0043] The main process parameters of each embodiment and comparative example in the specific implementation are shown in Table 2.

[0044] The material parameters and magnetic properties of the products in each embodiment and comparative example are shown in Table 3.

[0045] Table 1 (wt%)

[0046] Example C Si Als Mn S N Cu Ti+Nb 1 0.0369 3.46 0.0263 0.094 0.002 0.0071 0.005 0.002 2 0.0650 3.06 0.0316 0.076 0.004 0.0086 0.008 0.001 3 0.0360 3.05 0.0278 0.084 0.005 0.0082 0.010 0.001 4 0.0451 3.41 0.0256 0.076 0.005 0.0067 0.002 0.001 5 0.0605 3.46 0.0321 0.094 0.000 0.0065 0.004 0.002 6 0.0500 3.26 0.0325 0.077 0.004 0.0083 0.006 0.002 7 0.0392 3.46 0.0297 0.094 0.000 0.0078 0.008 0.002 8 0.0385 3.31 0.0325 0.080 0.000 0.0076 0.009 0.001 9 0.0511 3.05 0.0295 0.076 0.000 0.0086 0.002 0.001 10 0.0496 3.32 0.0287 0.080 0.000 0.0065 0.002 0.001 11 0.0408 3.09 0.0309 0.081 0.003 0.0086 0.002 0.001 12 0.0650 3.05 0.0292 0.083 0.004 0.0086 0.006 0.002 13 0.0471 3.46 0.0279 0.076 0.001 0.0065 0.004 0.001 Comparative Example 1 0.0384 3.46 0.0265 0.092 0.000 0.0070 0.008 0.001 Comparative Example 2 0.0650 3.38 0.0266 0.076 0.002 0.0086 0.002 0.000 Comparative Example 3 0.0360 3.07 0.0279 0.077 0.005 0.0070 0.010 0.002 Comparative Example 4 0.0405 3.27 0.0256 0.076 0.005 0.0067 0.009 0.001 Comparative Example 5 0.0396 3.22 0.0299 0.094 0.002 0.0065 0.004 0.002 Comparative Example 6 0.0404 3.12 0.0325 0.092 0.001 0.0082 0.003 0.002 Comparative Example 7 0.0416 3.44 0.0325 0.091 0.000 0.0080 0.008 0.001 Comparative Example 8 0.0416 3.28 0.0319 0.093 0.003 0.0081 0.003 0.001

[0047] Table 2

[0048]

[0049]

[0050] Table 3

[0051]

[0052] As can be seen from the embodiments, the method of the present invention enables online iron loss detection and adjustment control of steel strip after continuous decarburization and nitriding annealing, eliminating the need for conventional nitriding chemical testing; simultaneously, by adjusting and controlling the I0 value of the steel coil within a reasonable range through a rapid heating process, the produced finished product exhibits refined magnetic domains. 800 ≥1.923T, iron loss P 1.7 / 50 High-magnetic-induction grain-oriented silicon steel with a magnetic domain refinement improvement rate of not less than 10.6%. In contrast, the finished product B produced using conventional methods, after magnetic domain refinement... 800Below 1.907T, and iron loss P 1.7 / 50 The improvement rate of magnetic domain refinement is no higher than 10.5%. This specific embodiment is only a best example and is not a limiting implementation of the technical solution of the present invention.

Claims

1. A method for preparing low-temperature high-magnetic-induction oriented silicon steel by rapid heating and decarburization annealing, characterized in that... Includes the following steps: 1) After smelting, grain-oriented silicon steel is cast into billets, which are then heated at 1080~1180℃ and hot-rolled. 2) After the hot-rolled coil is pickled to remove the surface oxide layer, it undergoes normalizing annealing; 3) After normalizing, the steel coil undergoes a single cold rolling process, resulting in a finished thickness of [thickness value missing]. d (unit: mm), and the cold rolling reduction rate ranges from 88.4% to 91.0%; 4) Cold-rolled coils undergo continuous decarburization and nitriding annealing. The rolling iron loss value P of the steel strip during continuous annealing is... R13 / 50 Testing was conducted, and P was adjusted by controlling the unit ammonia consumption (N) in the nitriding process. R13 / 50 The following detection ranges are achieved: 2.996+2.428×d-10.78×[Si]≤ P R1.3 / 50 ≤ 3.008+2.605×d-11.15×[Si]; Adjusting the rolling iron loss value P R13 / 50 During the process, when the rolling iron loss value increases by P R13 / 50 When N = 0.01 W / kg, the ammonia conditioning amount N during decarburization and nitriding annealing is... P= 0.01 = 0.00491 + 0.0339 × d; Wherein, N represents the amount of ammonia gas required per unit weight of steel strip for annealing per unit time, expressed in m³. 3 / (kg·h); d is the finished product thickness in mm; [Si] is the mass percentage of Si in the grain-oriented silicon steel; 5) Apply magnesium oxide annealing release agent, anneal at high temperature, apply tension coating, and stretch to flatten.

2. The method for preparing low-temperature high-magnetic-induction oriented silicon steel as described in claim 1, characterized in that... The composition and weight percentage of the oriented silicon steel described in step 1 are as follows: C: 0.036%~0.065%, Si: 3.05~3.46%, Als: 0.0256~0.0325%, Mn: 0.076~0.094%, N: 0.0065~0.0086%, S: ≤0.005%, Cu: ≤0.01%, Ti+Nb: ≤0.002%, with the remainder being Fe and unavoidable inclusions.

3. The method for preparing low-temperature high-magnetic-induction oriented silicon steel as described in claim 1, characterized in that... The heating rate of continuous annealing in step 4 v The annealing speed is 150℃ / s to 350℃ / s, and the annealing temperature range is 820℃ to 825℃.

4. The method for preparing low-temperature high-magnetic-induction oriented silicon steel as described in claim 1, characterized in that... Step 4: After decarburization and nitriding annealing, define the transverse iron loss value of the steel coil as P. N13 / 50 Its relationship with rolling iron loss value P R13 / 50 The horizontal and vertical difference ratios satisfy 1.297; of which .

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