Method for producing low-temperature high-magnetic-induction oriented silicon steel by rapid heating and normalizing

Abstract

The application discloses a method for preparing low-temperature high-magnetic-susceptibility oriented silicon steel through rapid heating and normalizing, and the oriented silicon steel is cast into a blank after smelting, and the cast blank is heated at 1060-1160 DEG C; the cast blank is subjected to conventional hot rolling, and the thickness D of the hot-rolled coil is 1.8-2.8 mm; the steel coil after the hot-rolled coiling is subjected to two-stage heating and normalizing of a high-temperature stage and a low-temperature stage under dry pure N2 conditions; after the normalizing is completed, the steel coil is subjected to one-pass cold rolling; the cold-rolled coil is subjected to decarburization and nitriding continuous annealing, and the continuous annealing temperature is 820-825 DEG C; the carbon content of the steel strip after the continuous annealing is not higher than 10 ppm; the nitrogen content ranges from 220 to 240 ppm; after the continuous annealing is completed, the rolling direction iron loss value P R15 / 50 and the transverse direction iron loss value P N15 / 50 of the steel strip are detected; the surface of the steel strip after the nitriding treatment is coated with high-temperature annealing release agent and dried, and the steel strip is coiled; two-stage high-temperature annealing of low-temperature holding and high-temperature holding is carried out; and conventional stretching, flattening, insulating layer coating and dry curing annealing are carried out.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metallurgy, and particularly relates to a preparation method of low-temperature high-magnetic-susceptibility oriented silicon steel. BACKGROUND

[0002] Oriented silicon steel is the most widely used ferromagnetic material in the world. Its characteristic is that the secondary recrystallization of the primary grains in the {111} <001> orientation is abnormally long to form finished grains with a size of more than one centimeter, and the Goss texture is preferentially arranged so that the shortest axis <001> in the metal lattice is concentrated along the rolling direction. Therefore, the oriented silicon steel has excellent magnetic properties in the rolling direction of cold rolling, and can achieve very high magnetic susceptibility in the magnetization process. The magnetic performance characteristics of the oriented silicon steel in different directions are used to manufacture transformer cores. The magnetic properties of the oriented silicon steel sheet have an important influence on the efficiency and loss of the transformer, and the working stability. When high-grade silicon steel sheets with high magnetic susceptibility are used to manufacture transformer cores, a wide range of magnetic density design can be achieved, and the cross-sectional area of the transformer core can be designed to be smaller to the maximum extent. At this time, the volume and weight of the transformer are reduced. The manufacturing, transportation and assembly costs of the transformer are also reduced; the higher the grade of the silicon steel sheet, the lower the no-load loss and operating loss of the transformer, thereby greatly reducing the energy loss in the power transmission process. In addition, the higher the magnetic susceptibility of the oriented silicon steel, the smaller the magnetic strain value in the magnetization process, and the smaller the noise caused by the expansion of the silicon steel sheet in the alternating magnetization of the manufactured core, which can particularly meet the demand of urban low-noise transformers. In summary, high magnetic susceptibility and low iron loss are two indispensable aspects of high-quality oriented silicon steel products, and the comprehensive economic benefits of manufacturing transformers by using high-grade oriented silicon steel sheets will be higher. Especially since 2020, the national standard "Power Transformer Energy Efficiency Limit Value and Energy Efficiency Grade GB20052-2020" has been issued, and the mandatory upgrading of high-energy-efficiency transformers will promote the surge in demand for high-end oriented silicon steel products.

[0003] The more accurate the Goss texture orientation of the finished grain of the oriented silicon steel, the higher the magnetic susceptibility, and the lower the product iron loss. From the manufacturing process, the production method of the oriented silicon steel is divided into high-temperature hot-rolled slab heating technology (the heating temperature is usually higher than 1300℃), medium-temperature slab heating technology (the heating temperature is between 1200℃ and 1300℃), and low-temperature slab heating technology (the heating temperature is usually below 1200℃). The low-temperature slab heating preparation method effectively solves or reduces the problems of iron oxide scale, low yield, large equipment loss, high fuel consumption, and many surface defects in the production of oriented silicon steel, which meets the requirements of the national low-carbon and environmental protection strategy of the steel industry, and is the main trend of current technology development.

[0004] Decarburization annealing process in the manufacturing process of low temperature high magnetic induction oriented silicon steel is crucial for the above three quality. Oriented silicon steel belongs to low carbon iron silicon alloy, and its grain growth in normalizing annealing and decarburization annealing process in silicon steel production process is called "primary recrystallization", which is characterized by equiaxed ferrite grains. The precipitates formed after steelmaking alloying in steel will hinder the growth of primary recrystallization grains to a certain extent. Due to the composition design characteristics, the precipitates of low temperature oriented steel after steelmaking alloying are less than those of traditional high temperature steel, which leads to the weakening of the inhibition of primary recrystallization growth. Therefore, the grain size of low temperature high magnetic induction oriented silicon steel is larger than that of traditional high temperature steel in the decarburization annealing process, and more coarse grains appear. The unevenness of primary grains will directly affect the occurrence and perfection degree of secondary recrystallization abnormal growth. The uneven primary grains will lead to the uneven occurrence of secondary recrystallization, and the larger coarse primary grains are difficult to be swallowed by the abnormal growth of gauss grains, finally forming uneven and imperfect gauss texture, and the product magnetic performance is poor.

[0005] The primary recrystallization growth process is divided into two stages of grain nucleation and recrystallization growth. The greater the heating rate during the heating process of metal materials, the more the number of nucleation, so the formed grains are more, the grain size is small and uniform; after recrystallization nucleation, the higher the heat treatment temperature, the further the grain growth and the larger the final size. In the heat treatment process, the heating rate of steel strip obtained under the condition of conventional heating equipment is usually below 100℃ / s. In order to reduce the grain coarsening and obtain highly uniform grain structure, people have developed many heat treatment equipment means to improve the heating rate, such as electromagnetic induction heating, pulse current heating, infrared radiation heating and other technologies, and the heating rate of steel strip can reach more than 300℃ / s.

[0006] The application of high-speed heating technology to improve the mechanical properties and microstructure uniformity of steel materials has been widely used, but the actual application of technology to improve product performance in the production of grain-oriented silicon steel is still limited. At present, there are many applications of rapid heating equipment in the rapid drying of MgO coating and coating solution for silicon steel. However, for the improvement of material properties, the control of primary recrystallization during decarburization after cold rolling is mainly used by rapid heating. For example, Japanese Patent No. 2013-189712 shows that by using different heating rates, the texture intensity value I{111} / I{411} of the primary grains is less than 3, that is, the proportion of {411} type grains in the primary recrystallization is increased, which can improve the magnetic induction of the product. However, this technology requires the annealing process to have a layered structure with a spacing of more than 20 μm, and the penetration depth of eddy current increases in the temperature range near the Curie point during rapid heating due to the thinness of the grain-oriented silicon steel sheet. On the cross-section of the steel sheet thickness direction, the eddy current generated in the surface layer will be offset inside and outside, and it is difficult to flow through the eddy current to continue to heat the steel sheet. The maximum heating temperature of induction heating is near the Curie point 720℃. Therefore, the heating rate and capacity of rapid heating after cold rolling are very limited. At the same time, the use of high-speed heating during decarburization annealing and the moisture atmosphere will affect the formation rate of the internal oxidation layer of the cold-rolled sheet, increase the control difficulty of the oxidation degree, and also affect the adhesion of the final insulating coating of the product. SUMMARY

[0007] To solve the problems of low magnetic induction and uneven magnetic properties in the length direction of the product, and small improvement rate of iron loss after domain refinement in the grain-oriented silicon steel produced by low-temperature slab heating with less inherent inhibitor elements in the steelmaking composition and difficult to control the primary recrystallization structure during annealing, the present application uses rapid heating technology with a heating rate of 300℃ / s to 1200℃ / s in the normalizing annealing process to control the iron loss difference between the horizontal and vertical directions of the primary recrystallization to reach a suitable range, and uses a targeted heat preservation method in high-temperature annealing to promote the full development of secondary recrystallization, thereby preparing a low-temperature high-magnetic induction grain-oriented silicon steel with a thickness of 0.18-0.35 mm, a product magnetic induction of not less than 1.926T, and an improvement rate of iron loss after domain refinement of not less than 11.5%.

[0008] To achieve the above-mentioned purpose, the technical solution is as follows:

[0009] The method for preparing low-temperature high-magnetic induction grain-oriented silicon steel by rapid heating normalizing comprises the following steps:

[0010] 1) The grain-oriented silicon steel is cast into a slab after smelting, and the cast slab is heated at a temperature of 1060-1160℃;

[0011] 2) The cast slab is conventionally hot-rolled to form a hot-rolled coil with a thickness D of 1.8-2.8 mm;

[0012] 3) The hot-rolled coil is heated to high temperature + low temperature two-stage heating and normalizing under dry pure N2 conditions after coiling;

[0013] The high-temperature heating and normalizing stage heats the hot-rolled plate to a high-temperature normalizing soaking temperature T h at a heating rate v, and the heating rate v ranges from 300-1200 ℃ / s, the high-temperature normalizing soaking temperature T h is determined by formula (1), and the temperature T h is maintained for 35-55 s;

[0014] T h = 921-5645×[Als]+10883[N]+68.7×D............(1)

[0015] wherein [Als] and [N] are the weight percentage contents of steelmaking components Als and N elements, respectively; and D is the hot-rolled coil thickness in mm;

[0016] The low-temperature heating and normalizing stage reduces the temperature of the coil to T l , and the temperature T l ranges from 890-930 ℃, and the temperature T l is maintained for 45-55 s;

[0017] 4) After the normalizing is completed, the coil is cold-rolled by one pass, and the cold-rolling reduction rate is determined by formula (2);

[0018]

[0019] wherein d is the finished product thickness, and D is the hot-rolled coil thickness in mm;

[0020] 5) The cold-rolled coil is subjected to decarburization and nitriding continuous annealing, and the continuous annealing temperature is 820-825 ℃; the carbon content of the steel strip after the continuous annealing is not higher than 10 ppm; the nitrogen content ranges from 220-240 ppm; and the rolling direction iron loss value P R15 / 50 and the transverse direction iron loss value P N15 / 50 of the steel strip are detected after the continuous annealing is completed;

[0021] and the difference between the steel coil structure in the transverse and longitudinal directions I o satisfies 1.256≤I o ≤1.345, and the definition is

[0022] 6) The surface of the steel strip after the nitriding treatment is coated with a high-temperature annealing release agent and dried, and the coil is coiled;

[0023] 7) Two-stage high-temperature annealing of low-temperature holding + high-temperature holding is performed;

[0024] The low-temperature annealing stage is to heat to temperature T1 and keep temperature for t time, and temperature T1 and time t are determined by formula (3) and (4);

[0025] T1=-66.8×P R15 / 50 +130.3×d-8884.5×[Si]-0.035×v+1617.7............(3)

[0026] t=987.8×I o -1105.4............(4)

[0027] Wherein, [Si] is the weight percentage content of Si element in the steelmaking component;

[0028] The high-temperature annealing stage is to heat to temperature T2, and T2 ranges from 1160 to 1240℃;

[0029] 8) to carry out the conventional drawing, flattening, coating insulation layer and drying curing annealing.

[0030] According to the above scheme, the components and weight ratio of the high-magnetic-sensing oriented silicon steel are as follows: C: 0.039% to 0.064%, Si: 2.95 to 3.46%, Al: 0.0246 to 0.0335%, Mn: 0.056 to 0.095%, N: 0.0061 to 0.0089%, S: ≤0.01%, Cu: ≤0.2%, Ti+Nb: ≤0.003%, and the rest is Fe and inevitable inclusions.

[0031] According to the above scheme, in the low-temperature annealing stage in step 7, pure N2 atmosphere is used in the heating process before T1, and the pure nitrogen gas is converted into N2:H2=1:(2.5 to 3.5) mixed gas during the t time.

[0032] According to the above scheme, in the high-temperature annealing stage in step 7, the temperature T h The atmosphere is converted into pure H2 atmosphere during the process, and the N and S element contents in the steel are not more than 10 ppm by keeping the temperature.

[0033] Compared with the prior art, the present application has the following beneficial effects:

[0034] The application adopts a rapid heating technology obviously higher than the conventional normalizing in the normalizing process of low-temperature oriented silicon steel, the heating rate reaches 300℃ / s or above, and has the effects of improving production efficiency and improving product performance. By increasing the heating rate of the normalizing high-temperature heating process from the conventional 75℃ / s or below to a higher rate of 300℃ / s or above, the heating time of the normalizing process can be reduced by 90%, and the length of the heating furnace body can be greatly shortened, saving equipment space and investment. From the aspect of material organization improvement, the rapid heating of normalizing can promote the maximum degree of uniform nucleation of the recrystallization process of the hot-rolled plate, and reduce the recovery of the heat storage energy of the hot-rolled plate. The recrystallization nucleation amount increases during the normalizing heating process, the grain size decreases and is uniform. At the same time, the rapid heating shortens the heating time, which can promote the material to enter the temperature range with the largest proportion of austenite in the shortest time, reduce the size of the precipitated phase due to slow heating, and thus solve the problem of losing the control ability of the primary recrystallization.

[0035] And according to formula (1), the normalizing high-temperature section temperature is controlled for different hot-rolled thickness raw materials and key components, in order to ensure that the main inhibitor AlN of low-temperature high-magnetic oriented silicon steel remains highly solid-soluted and is not easy to overheat, so as to prevent the inhibitor from becoming coarse. And according to different thickness of the hot-rolled coil, the appropriate normalizing temperature is proposed, so that the normalizing raw material state before cold rolling is more stable. The reason why the present application controls the relationship between the hot-rolled thickness raw material and the finished product thickness according to formula (2) is to control the stable range of the cold rolling reduction rate when producing hot-rolled raw materials of different thicknesses.

[0036] The reason why the present application detects the rolling direction iron loss value P R15 / 50 and the transverse direction iron loss value P N15 / 50 of the steel strip after decarburization and nitriding continuous annealing is that the primary recrystallization size and the iron loss of the material after continuous annealing have important relevance. After continuous annealing, the primary recrystallization diameter of the oriented silicon steel can reach tens of μm, similar to the grain structure of the non-oriented silicon steel finished product. The primary recrystallization size and the iron loss value of the steel strip at this time present a certain inverse relationship, the smaller the primary recrystallization grain diameter, the larger the rolling direction iron loss value P R15 / 50 and the transverse direction iron loss value P N15 / 50 Therefore, the on-line detection of the iron loss value of the steel strip can improve the detection efficiency and efficiently evaluate the grain size level in different directions of the metal material. Moreover, the oriented silicon steel after continuous annealing presents single ferrite grains, and the rolling direction iron loss value P R15 / 50 and the transverse direction iron loss value P N15 / 50The detection can evaluate the uniformity of the grain size in the two directions respectively. This is because the oriented silicon steel is ultra-low carbon steel with carbon content not higher than 30ppm after decarburization annealing, the ferrite grains of which undergo equiaxial grain growth and is called primary recrystallization, the lattice of which is body-centered cubic structure, and the arrangement of the crystal faces and short axis <001>, relatively short axis <011> and long axis <111> of the lattice affect the magnetic conduction and thus affect the iron loss of the steel strip. The arrangement is called texture in material science, and the primary recrystallization texture shows strong γ texture characteristics, that is, the crystal lattices of most of the grains have the crystal face {111} parallel to the rolling plane. Due to the texture characteristics of the primary recrystallization formed by continuous annealing after cold rolling with large reduction ratio, the proportion of the relatively short axis <001> and <011> in the lattice is relatively large in the rolling direction due to the energy storage, and the proportion of the short axis <001>, relatively short axis <011>, long axis <111> and <112> is relatively large in the transverse direction perpendicular to the rolling direction, so that the magnetic conduction in the transverse direction is worse than that in the rolling direction, and the iron loss P 15 / 50 of the material in the transverse direction is usually about 1.2 times of that in the longitudinal direction at 1.5T and 50Hz. According to formula (3), the difference ratio of the texture in the transverse direction and the longitudinal direction of the steel strip after continuous annealing is I0. In the present application, the high-speed heating technology is used in the normalizing process, so that the uniformity of the grain structure after normalizing is improved, and the grain size of the primary recrystallization after continuous decarburization and nitriding annealing is relatively small, so that the iron loss P R15 / 50 in the rolling direction and the iron loss P N15 / 50 in the transverse direction are both larger than those of the material produced by the conventional technology. On the other hand, due to the high-speed heating, the energy storage of the normalizing annealing is improved, and the energy storage of the steel strip after cold rolling is further increased, so that the primary grains can nucleate more quickly and uniformly in the subsequent continuous annealing process, the grains with {111} and {110} crystal faces are more likely to form due to the high energy storage, and the <100>∥RD arrangement is more, so that the iron loss in the rolling direction is reduced, and thus the difference ratio I o of the transverse direction and the longitudinal direction is improved. In the present application, the iron loss P R15 / 50 in the rolling direction and the iron loss P N15 / 50 in the transverse direction after continuous decarburization and nitriding annealing have the distribution characteristics as shown in the accompanying Figure 1 .

[0037] In the present application, the two-stage process of "low-temperature holding + high-temperature holding" is used in the high-temperature annealing process, the high-temperature holding is the conventional annealing for purifying elements such as N and S, and the requirement of purifying the steel is achieved; and the low-temperature holding is to change the traditional temperature development process of the secondary recrystallization to a stable and appropriate temperature for developing the secondary recrystallization, and a mixed gas atmosphere beneficial to the stability of the inhibitor is used, so that the secondary recrystallization is more perfect, and the magnetic property stability of the product is better. The starting temperature T l of the secondary recrystallization is determined by the primary grain size, PR15 / 50 The initial recrystallization size is inversely proportional to the initial grain size. This invention uses the initial grain size and P... R15 / 50 The interrelationships between these factors determined the temperature T at which the material began to recrystallize. l As described in formula (3). On the other hand, the development of secondary recrystallization from the initial recrystallization under a certain temperature condition requires time to complete. The difference between the transverse and longitudinal directions of the microstructure after the initial recrystallization is I. o The larger the crystal, the more likely it is to be in the initial recrystallization stage. <001> The shafts or shorter shafts are arranged more along the rolling direction, and the time required for secondary recrystallization is relatively short. High-temperature annealing at a low temperature for a long time is not good for product performance. Therefore, setting the low holding time according to formula (4) for secondary recrystallization can avoid long-term low-temperature annealing and provide sufficient time for secondary recrystallization development.

[0038] Compared with the prior art, this invention uses high-speed heating and normalization to control the difference ratio of iron loss in the transverse and longitudinal directions during the initial recrystallization to prepare low-temperature high magnetic induction oriented silicon steel products with a thickness of 0.18-0.35mm. The normalization heating time is shortened, the product thickness specifications are widely applicable, the product magnetic induction is not less than 1.923T, and the iron loss reduction improvement rate after magnetic domain refinement is not less than 11.5%. Attached Figure Description

[0039] Figure 1 The rolling iron loss value P after continuous decarburization, nitriding, and annealing according to this invention R15 / 50 And transverse iron loss value P N15 / 50 Distribution characteristics. Detailed Implementation

[0040] 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.

[0041] The specific implementation provides a method for rapidly heating and normalizing to prepare low-temperature high-magnetic-induction oriented silicon steel, including the following steps:

[0042] 1) After smelting, grain-oriented silicon steel is cast into billets and heated at 1060-1160℃;

[0043] 2) The billet is subjected to conventional hot rolling, and the thickness D of the hot-rolled coil is 1.8 to 2.8 mm;

[0044] 3) The hot-rolled coils are normalized by a two-stage heating process of high temperature section + low temperature section under dry pure N2 conditions.

[0045] During the high-temperature heating and normalization stage, the hot-rolled plate is heated to the high-temperature normalization homogenization temperature T at a heating rate v. h The heating rate v ranges from 300 to 1200℃ / s, and the high-temperature normalization homogenization temperature T h As determined by formula (1), at Th Keep warm at the specified temperature for 35–55 seconds;

[0046] T h =921-5645×[Als]+10883[N]+68.7×D............(1)

[0047] Where [Als] and [N] are the weight percentage contents of Als and N elements in the steelmaking components, respectively; D is the thickness of the hot-rolled coil, in mm;

[0048] During the low-temperature heating and normalization stage, the temperature of the steel coil is reduced to T. l T l The temperature range is between 890 and 930℃, at T l Hold at the temperature for 45–55 seconds;

[0049] 4) After normalizing, the steel coil undergoes a single cold rolling process with a reduction rate of [missing information]. Determined by formula (2);

[0050]

[0051] Where d is the finished product thickness and D is the hot-rolled coil thickness, in mm;

[0052] 5) Cold-rolled coils undergo continuous decarburization and nitriding annealing at temperatures ranging from 820℃ to 825℃; after continuous annealing, the carbon content of the steel strip should not exceed 10 ppm; the nitrogen content should range from 220-240 ppm; after continuous annealing, the rolling iron loss value P of the steel strip should be measured. R15 / 50 And transverse iron loss value P N15 / 50 ;

[0053] Furthermore, the difference in the transverse and longitudinal structure of the steel coil is greater than that of I. o Satisfying 1.256≤I o ≤1.345, defined

[0054] 6) After nitriding, the steel strip surface is coated with a high-temperature annealing release agent and dried to remove moisture, then wound into coils;

[0055] 7) Perform a two-stage high-temperature annealing process consisting of low-temperature insulation and high-temperature insulation;

[0056] During the low-temperature heat preservation annealing stage, the temperature is raised to T1 and held for t time. The temperature T1 and time t are determined by formulas (3) and (4). During the heating process before T1, a pure N2 atmosphere is used. During the heat preservation time t, the pure nitrogen gas is converted into a mixed gas of N2:H2 = 1:(2.5~3.5).

[0057] T1 = -66.8 × P R15 / 50+130.3×d-8884.5×[Si]-0.035×v+1617.7............(3)

[0058] t = 987.8 × I o -1105.4............(4)

[0059] Wherein, [Si] represents the weight percentage content of Si element in the steelmaking component;

[0060] During the high-temperature holding annealing stage, the temperature is raised to T2, which ranges from 1160 to 1240℃. During the process of raising the temperature to T2, the atmosphere is converted to pure H2 atmosphere, and the temperature is held at this temperature so that the content of N and S elements in the steel does not exceed 10ppm.

[0061] 8) Perform routine stretching, leveling, coating with an insulating layer, and drying, curing, and annealing.

[0062] Specifically, the high magnetic orientation silicon steel composition and weight percentage adapted to this invention are: C: 0.039%–0.064%, Si: 2.95–3.46%, Als: 0.0246–0.0335%, Mn: 0.056–0.095%, N: 0.0061–0.0089%, S: ≤0.01%, Cu: ≤0.2%, Ti+Nb: ≤0.003%, with the remainder being Fe and unavoidable inclusions.

[0063] Table 1 is a list of chemical components for each embodiment and comparative example of the present invention.

[0064] Table 2 is a list of the main process parameters for each embodiment and comparative example of the present invention.

[0065] Table 3 lists the material parameters and magnetic properties of the products in the various embodiments and comparative examples of the present invention.

[0066] Table 1

[0067] Examples C Si Als Mn S N Cu Ti+Nb 1 0.0512 3.46 0.3340 0.068 0.075 0.7600 0.036 0.0030 2 0.0640 3.41 0.3310 0.056 0.030 0.0089 0.048 0.0000 3 0.0390 2.95 0.3160 0.095 0.010 0.7600 0.200 0.0028 4 0.0485 3.27 0.0260 0.056 0.010 0.8500 0.126 0.0017 5 0.0595 3.06 0.2750 0.095 0.011 0.0061 0.142 0.0014 6 0.0625 3.06 0.0335 0.088 0.081 0.8800 0.101 0.0007 7 0.0561 3.46 0.2700 0.095 0.001 0.6700 0.180 0.0030 8 0.0506 3.02 0.0335 0.091 0.047 0.7900 0.053 0.0030 9 0.0454 2.95 0.2980 0.056 0.006 0.6400 0.001 0.0005 10 0.0453 3.34 0.3130 0.069 0.051 0.8800 0.135 0.0000 11 0.0633 3.03 0.3150 0.090 0.045 0.0089 0.089 0.0013 12 0.0640 3.30 0.2910 0.062 0.036 0.0089 0.176 0.0012 13 0.0630 3.06 0.3150 0.058 0.071 0.8600 0.200 0.0006 14 0.0513 3.05 0.0246 0.095 0.057 0.8800 0.154 0.0017 15 0.0526 3.31 0.2880 0.062 0.074 0.0061 0.185 0.0026 16 0.0621 3.37 0.2830 0.056 0.011 0.0061 0.178 0.0009 Comparative Example 1 0.0410 3.41 0.3090 0.093 0.029 0.7000 0.093 0.0029 Comparative Example 2 0.0640 3.10 0.3060 0.056 0.036 0.0089 0.020 0.0030 Comparative Example 3 0.0390 3.38 0.2860 0.056 0.010 0.8300 0.200 0.0004 Comparative Example 4 0.0491 2.99 0.0246 0.056 0.010 0.6400 0.136 0.0016 Comparative Example 5 0.0561 3.15 0.2730 0.095 0.035 0.0061 0.079 0.0012 Comparative Example 6 0.0435 3.05 0.0335 0.059 0.080 0.7700 0.074 0.0011 Comparative Example 7 0.0448 3.41 0.2460 0.095 0.071 0.8300 0.068 0.0020 Comparative Example 8 0.0468 2.98 0.0335 0.070 0.071 0.8300 0.129 0.0030 Comparative Example 9 0.0476 2.95 0.2840 0.084 0.037 0.6600 0.123 0.0026 Comparative Example 10 0.0533 3.40 0.2520 0.093 0.032 0.7500 0.041 0.0025

[0068] Table 2

[0069]

[0070] Table 3

[0071]

[0072]

[0073] As can be seen from Table 3, the low-temperature high magnetic induction oriented silicon steel products produced using the method of the present invention, under the same specifications, exhibit magnetic properties B after domain refinement using the process of the examples.800 The average value reached over 1.923T. Meanwhile, under the same finished product thickness specifications, the average improvement in iron loss after magnetic domain refinement in the example product was at least 11.5%. This specific embodiment is merely a best example and is not intended to limit the implementation of the technical solution of this invention.

Claims

1. A method for rapidly heating and normalizing to prepare low-temperature high-magnetic-induction oriented silicon steel, characterized in that... Includes the following steps: 1) After smelting, grain-oriented silicon steel is cast into billets and heated at 1060-1160℃; 2) The billet is subjected to conventional hot rolling, and the thickness D of the hot-rolled coil is 1.8 to 2.8 mm; 3) The hot-rolled coils are normalized by a two-stage heating process of high temperature section + low temperature section under dry pure N2 conditions. 4) After normalizing, the steel coil undergoes a single cold rolling process with a reduction rate of [missing information]. Determined by formula (2); Where d is the finished product thickness and D is the hot-rolled coil thickness, in mm; 5) Cold-rolled coils undergo continuous decarburization and nitriding annealing at temperatures ranging from 820℃ to 825℃; after continuous annealing, the carbon content of the steel strip should not exceed 10 ppm; the nitrogen content should range from 220-240 ppm; after continuous annealing, the rolling iron loss value P of the steel strip should be measured. R15 / 50 And transverse iron loss value P N15 / 50 ; Furthermore, the difference in the transverse and longitudinal structure of the steel coil is greater than that of I. o Satisfying 1.256≤I o ≤1.345, defined 6) After nitriding, the steel strip surface is coated with a high-temperature annealing release agent and dried to remove moisture, then wound into coils; 7) Perform a two-stage high-temperature annealing process consisting of low-temperature insulation and high-temperature insulation; During the low-temperature heat preservation annealing stage, the temperature is raised to T1 and held for t time. The temperature T1 and time t are determined by formulas (3) and (4). T1=-66.8×P R15 / 50 +130.3×d-8884.5×[Si]-0.035×v+1617.7…………(3)t=987.8×I o -1105.4…………(4) Wherein, [Si] represents the weight percentage content of Si element in the steelmaking component; During the high-temperature heat preservation and annealing stage, the temperature is raised to T2, which ranges from 1160 to 1240℃. 8) Perform routine stretching, leveling, coating with an insulating layer, and drying, curing, and annealing.

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 ratio of the high magnetic induction oriented silicon steel are as follows: C: 0.039%–0.064%, Si: 2.95–3.46%, Als: 0.0246–0.0335%, Mn: 0.056–0.095%, N: 0.0061–0.0089%, S: ≤0.01%, Cu: ≤0.2%, Ti+Nb: ≤0.003%, 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... In step 3, during the high-temperature heating and normalizing stage, the hot-rolled plate is heated to the high-temperature normalizing homogenization temperature T at a heating rate v. h The heating rate v ranges from 300 to 1200℃ / s, and the high-temperature normalization homogenization temperature T h As determined by formula (1), at T h Keep warm at the specified temperature for 35–55 seconds; T h =921-5645×[Als]+10883[N]+68.7×D…………(1) Wherein, [Als] and [N] are the weight percentage contents of Als and N elements in the steelmaking components, respectively; D is the thickness of the hot-rolled coil, in mm.

4. The method for preparing low-temperature high-magnetic-induction oriented silicon steel as described in claim 1, characterized in that... In step 3, during the low-temperature heating and normalization stage, the temperature of the steel coil is reduced to T. l T l The temperature range is between 890 and 930℃, at T l Keep warm at the specified temperature for 45–55 seconds.

5. The method for preparing low-temperature high magnetic induction oriented silicon steel as described in claim 1, characterized in that... In step 7, during the low-temperature annealing stage, a pure N2 atmosphere is used during the heating process before T1. During the holding time t, the pure nitrogen gas is converted into a mixed gas of N2:H2 = 1:(2.5~3.5).

6. The method for preparing low-temperature high magnetic induction oriented silicon steel as described in claim 1, characterized in that... In step 7, during the high-temperature holding annealing stage, the atmosphere is converted to pure H2 atmosphere during the process of heating to temperature T2, and the temperature is held at this temperature so that the content of N and S elements in the steel does not exceed 10ppm.

Images