Manufacturing method of low-temperature high-magnetic-induction oriented silicon steel with excellent and stable magnetic performance

Abstract

The invention discloses a manufacturing method of low-temperature high-magnetic-induction oriented silicon steel with excellent and stable magnetic performance, and belongs to the technical field of high-magnetic-induction oriented silicon steel. According to the method, the temperature of the steel strip is controlled before cold rolling, the heating speed and the heating temperature of the steel strip and the temperature of the steel strip before cold rolling and in the cold rolling process are controlled by emphatically utilizing the C content in the steel, on one hand, oriented silicon steel with an excellent plate shape can be obtained, and on the other hand, the texture orientation degree of the steel strip after cold rolling is improved; particularly, the Gaussian orientation degree of the steel plate in the rolling direction is stably controlled, the magnetic performance of the steel plate is improved, it is guaranteed that the magnetism of the steel strip in the rolling direction is stable and uniform, the magnetic induction range in the rolling direction does not exceed 0.001 T, and the iron loss range in the rolling direction does not exceed 0.001 w / kg.

Description

Technical Field

[0001] The invention belongs to the technical field of high magnetic induction oriented silicon steel, and in particular relates to a method for manufacturing low-temperature high magnetic induction oriented silicon steel with excellent and stable magnetic properties. Background Art

[0002] High magnetic induction oriented silicon steel is an important soft magnetic material, widely used in power transmission and transformation industries such as large transformers. The transformer core is generally composed of oriented silicon steel laminations. The lamination direction requires that the silicon steel sheets are easily magnetized in the same direction as the magnetic field and form a ring loop. The smaller the resistance when the core is magnetized, the higher the efficiency of the transformer. Therefore, the oriented silicon steel sheets used to make the transformer core are required to have high magnetic induction intensity and low iron loss.

[0003] The manufacturing process of low-temperature and high-magnetic induction oriented silicon steel mainly includes: steelmaking, hot rolling, pickling and normalizing, cold rolling, decarburization annealing, nitriding, coating of magnesium oxide isolation agent, high-temperature annealing, coating of insulating coating, flat stretching annealing, finishing and other steps. When the Gaussian texture in oriented silicon steel is highly consistent with the rolling direction, it has a lower iron loss. Reducing the thickness of the steel plate is beneficial to improving the magnetic properties of the steel plate. However, as the thickness of the steel plate is reduced, the orientation change of the Gaussian texture during the rolling process becomes larger and larger, especially at the head and tail. The deviation of the Gaussian texture from the rolling direction becomes larger and larger, resulting in uneven magnetic properties of the finished steel plate along the rolling direction. The uneven magnetic properties of the steel coil along the rolling direction, especially the head and tail magnetic properties difference caused by the head and tail waste, the reduction of product grade rate, and the poor stability of the performance of the transformer core made by the user are urgent problems to be solved in the production of oriented silicon steel. In order to obtain low-temperature and high-magnetic induction oriented silicon steel with uniform magnetic properties, relevant personnel have done a lot of research.

[0004] Patent CN116287626A proposes a method for improving the magnetic uniformity of oriented silicon steel, wherein the hot-rolled strips are connected and heated in sequence, and the heating temperature of the head and tail of each hot-rolled strip is controlled to be 100-300°C higher than the heating temperature of the middle part; the heated hot-rolled strips are cold-rolled in a row, and the cold rolling rate of the middle part of each hot-rolled strip is controlled to be higher than the cold rolling rate of the head and tail, so as to obtain oriented silicon steel with uniform magnetic properties. With this method, the maximum value of the longitudinal magnetic induction range of the oriented silicon steel is 0.001-0.005T, and the longitudinal magnetic induction uniformity of the oriented silicon steel is good. However, in actual production, it is difficult to control the temperature of the head and tail of the strip to be higher than the temperature of the middle of the steel strip.

[0005] Patent CN115478145A proposes a method for improving the magnetic uniformity and production efficiency of oriented silicon steel. This method adopts two cold rolling + intermediate annealing process, which is aimed at the production of ordinary oriented silicon steel. It mainly carries out decarburization annealing and high-temperature annealing on the same production line. It adopts a vertical annealing furnace unit to avoid the plate defects and magnetic unevenness caused by long-term high temperature in the high-temperature bell furnace. By improving the high-temperature annealing equipment, the uniformity of steel plate heating is improved, thereby improving the magnetic uniformity of oriented silicon steel. This method is mainly aimed at the problem of magnetic uniformity along the width direction of the steel plate, and still cannot solve the problem of magnetic uniformity of the steel plate along the rolling direction.

[0006] Patent CN115747650A proposes a method for improving the magnetic stability of low-temperature, high-magnetic-induction oriented silicon steel. By comprehensively considering the composition, normalizing process and nitriding process, the uniformity of the content of nitride inhibitors formed later is ensured, thereby improving the stability of the magnetic properties of the finished product of low-temperature, high-magnetic-induction oriented silicon steel. This method requires the calculation of the AlN inhibitor content dissolved at the normalizing heating temperature, mainly to avoid the problem of unstable magnetic properties of the finished product caused by fluctuations in Als and N content during the smelting of low-temperature oriented silicon steel, and still cannot solve the problem of uniform magnetic properties of steel plates along the rolling direction.

[0007] Patent CN115537512A proposes a production method for improving the uniformity of longitudinal magnetic properties of low-temperature high-magnetic induction oriented silicon steel coils. By strictly controlling the temperature after hot rolling, the heating rate of the decarburization annealing process, and the total amount of nitriding, and matching the appropriate high-temperature annealing atmosphere protection system, the uniformity of longitudinal magnetic properties of the steel coil is significantly improved, and the longitudinal magnetic property difference is controlled within 3%. However, the longitudinal magnetic property difference is still high, and the magnetic uniformity of the steel plate along the rolling direction needs to be improved.

[0008] Patent CN108004376A proposes a method for producing low-temperature, high-magnetic-induction oriented silicon steel with uniform longitudinal magnetic properties. The method mainly controls the concentration of acid-soluble aluminum, adjusts the decarburization temperature and prolongs the annealing time during the decarburization annealing process, etc., which can reduce the difference in magnetic properties between the head and the tail and improve the magnetic properties of the head and tail of the steel coil. The difference can be reduced to less than 5%. The longitudinal magnetic property difference is still relatively high, and the magnetic uniformity of the steel plate along the rolling direction needs to be improved.

[0009] How to reduce the uneven magnetic properties of oriented silicon steel coils along the rolling direction is an urgent issue. Summary of the invention

[0010] The present invention provides a method for manufacturing low-temperature high magnetic induction oriented silicon steel with excellent and stable magnetic properties. While obtaining oriented silicon steel with excellent plate shape, the Gaussian orientation degree of the steel plate along the rolling direction is stably controlled, the magnetic properties of the steel plate are improved, and the magnetic uniformity of the steel strip along the rolling direction is ensured.

[0011] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0012] Provided is a method for manufacturing low-temperature high-magnetic induction oriented silicon steel with excellent and stable magnetic properties, comprising the following steps: molten steel is smelted in a converter, continuously cast, the ingot is heated, hot rolled to 1.8 mm-2.3 mm, normalized pickling, cold rolled to 0.18 mm-0.30 mm, then decarburized and nitrided annealed, coated with a magnesium oxide annealing separator, and subjected to high-temperature annealing; coated with an insulating coating liquid, and finally subjected to stretching and flattening annealing; wherein:

[0013] The C content in the ingot is 350-550ppm;

[0014] The steel plate is heated up to the heating temperature T at a heating speed of V. The first cold rolling is started after the steel strip reaches the temperature T. The time from the steel strip reaching the temperature T to the start of the first cold rolling is controlled within 10 minutes. The temperature of the steel plate is not less than 140°C when the cold rolling starts.

[0015] The temperature of the steel plate is not less than 140℃ at the beginning of cold rolling, which is beneficial to the shape control during rolling and can give full play to the pinning effect of carbides on dislocations in the steel, especially to make the pinning effect of carbides on dislocations in the steel plate consistent along the rolling direction, so as to obtain oriented silicon steel with excellent and uniform magnetic properties. If the temperature of the steel plate is lower than 140℃, it is not conducive to the shape control during rolling, and the pinning effect of carbides on dislocations in the steel along the rolling direction cannot be fully exerted.

[0016] The time from the steel strip reaching the temperature to the start of the first cold rolling is controlled within 10 minutes. If the time is too long, the temperature of the steel plate will decrease, which is not conducive to the plate shape control during rolling. At the same time, due to the large temperature difference between the inner and outer rings of the steel coil, the magnetic properties of the steel coil along the rolling direction after cold rolling are uneven; if the heat preservation method is adopted, the heat preservation time is too long, which will cause the carbides in the steel to be coarse and reduce the pinning effect on dislocations.

[0017] The heating rate V of the steel strip has the following relationship with the thickness a (1.8mm-2.3mm) of the hot-rolled plate obtained by hot rolling and the C content [C] in the ingot:

[0018] [C] / (1.5×a)≤V≤[C] / (1.2×a) Relationship 1

[0019] The thicker the hot-rolled plate, the slower the heating speed should be; the higher the C content in the steel, the faster the heating speed should be. The thicker the hot-rolled plate, the less conducive it is to heat transfer in the steel plate. Therefore, the heating speed needs to be slowed down to reduce the temperature difference along the thickness direction of the hot-rolled plate, which is beneficial to stabilizing the Gaussian texture in the steel plate along the rolling direction. When the C content in the steel is relatively high, increasing the heating speed helps to increase the carbon diffusion rate in the steel sharply, which is beneficial to the solid solution of C in the steel. At the same time, it will not cause the rapid coarsening of carbides, which is beneficial to stabilizing the texture of the steel strip during subsequent cold rolling, making the Gaussian texture of the oriented silicon steel highly consistent with the rolling direction, and improving the magnetic properties of the final oriented silicon steel product.

[0020] The heating temperature T of the steel strip before cold rolling and the final thickness b (0.18mm-0.30mm) of the steel plate after cold rolling and the C content [C] in the ingot have the following relationship:

[0021] [C] / (10×b)≤T≤[C] / (9×b) Relationship 2

[0022] Among them, [C] / b is not less than 1400. The thinner the finished product thickness b, the less low the C content should be. Because the thinner the finished product thickness b, the higher the C content is, the more cold rolling dislocations will be during cold rolling, which will increase the recrystallization nucleation sites during annealing after cold rolling, and the primary grains will be small and uniform, which will promote the development of secondary recrystallization and improve the magnetic properties of the steel strip.

[0023] The higher the C content in the steel, the higher the temperature of the steel sheet should be before cold rolling, which is more conducive to promoting the solid solution of C and N in the steel and stabilizing the texture of the steel strip during the cold rolling process. The thinner the finished steel strip is, the greater the influence of the dislocation deformation in the steel during the cold rolling process on the grains. Increasing the temperature of the steel sheet before cold rolling is conducive to promoting the solid solution of C in the steel, increasing the amount of dissolved carbon and fine carbides in the steel, and increasing the pinning effect of carbides on dislocations in the steel during the cold rolling process, hindering the movement of dislocations, which is conducive to obtaining oriented silicon steel with a Gaussian texture highly consistent with the rolling direction, and improving the magnetic properties of the final oriented silicon steel product.

[0024] The temperature of the steel strip is controlled during the cold rolling process to keep the steel strip temperature T 冷 , cold rolling process steel strip temperature T 冷 The control of and the cold rolling reduction rate η have the following relationship:

[0025] 8 / (1-η)+100≤T 冷 ≤12 / (1-η)+120 Relationship 3

[0026] η=1-b / a

[0027] Maintaining the temperature of oriented silicon steel during the cold rolling process is conducive to improving the magnetic properties of the steel plate, especially making the magnetic properties of the steel strip more uniform along the rolling direction. If the temperature of the steel plate is too low, it is not conducive to the control of the shape of the steel plate. If the temperature of the steel plate is too high, it will cause the grains to recover and grow during the cold rolling process, resulting in poor primary recrystallization texture and reduced magnetic properties of the steel plate.

[0028] Among them, in equations 1-3, V, a, b, [C], T and T 冷 The unitless table represents a specific value, where V is expressed in °C / s; a and b are expressed in mm; [C] is expressed in ppm; T and T 冷 The unit is °C. η takes a specific value. For example, when η is 90%, the value is 0.9.

[0029] According to the above scheme, the steel plate is quickly heated to the heating temperature T at a heating rate of V by induction heating.

[0030] According to the above scheme, the composition and weight percentage content of the ingot are: C: 0.035%-0.055%, Si: 2.5%-3.5%, Mn: 0.02%-0.05%, S: 0.003%-0.008%, Als: 0.020%-0.035%, N: 0.006%-0.01%, and the balance is Fe and unavoidable impurities.

[0031] According to the above scheme, the ingot is heated to 1100-1200°C.

[0032] According to the above scheme, a 20-roll rolling mill is used to cold-roll the oriented silicon steel hot-rolled plate to a finished product thickness of 0.18mm-0.30mm; the rolling passes are 3 times.

[0033] According to the above scheme, the temperature of the steel strip is controlled during the cold rolling process, and the temperature T of the steel strip is controlled by controlling the emulsion flow rate. 冷 .

[0034] The beneficial effects of the present invention are as follows:

[0035] The present invention provides a method for manufacturing low-temperature high-magnetic induction oriented silicon steel with excellent and stable magnetic properties. The temperature of the steel strip is controlled before cold rolling, and the C content in the steel is mainly used to control its heating speed and heating temperature, as well as the temperature of the steel strip before and during cold rolling. On the one hand, oriented silicon steel with excellent plate shape can be obtained, and on the other hand, the texture orientation degree of the steel strip after cold rolling is improved, especially the Gauss orientation degree of the steel plate along the rolling direction is stably controlled, the magnetic properties of the steel plate are improved, and the magnetism of the steel strip along the rolling direction is ensured to be stable and uniform. The magnetic induction extreme difference along the rolling direction does not exceed 0.001T, and the iron loss extreme difference along the rolling direction does not exceed 0.001w / kg. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] The embodiment of the present invention provides a method for manufacturing low-temperature high magnetic induction oriented silicon steel with excellent and stable magnetic properties, comprising the following steps:

[0038] The molten steel is smelted in a converter and continuously cast, and the ingot is heated, hot-rolled to 1.8mm-2.3mm, normalized and pickled, cold-rolled to 0.18mm-0.30mm, and then decarburized and nitrided annealed, coated with magnesium oxide annealing separator, and high-temperature annealed; coated with insulating coating liquid, and finally stretched and flattened annealed; wherein:

[0039] The percentage content of C in the ingot is 350-550ppm;

[0040] The steel plate is quickly heated to the heating temperature T at a heating speed of V by induction heating. The first cold rolling is started after the steel strip reaches the temperature. The time from the steel strip reaching the temperature to the start of the first cold rolling is controlled within 10 minutes. The temperature of the steel plate is not less than 140°C when the cold rolling starts.

[0041] The heating speed V of the steel strip has the following relationship with the hot-rolled plate thickness a (1.8mm-2.3mm) and the C content [C] in the steel:

[0042] [C] / (1.5×a)≤V≤[C] / (1.2×a) Relationship 1

[0043] The heating temperature T of the steel strip before cold rolling and the final thickness b (0.18mm-0.30mm) of the steel plate after cold rolling and the C content [C] in the steel have the following relationship:

[0044] [C] / (10×b)≤T≤[C] / (9×b) Relationship 2

[0045] Where: [C] / b≥1400

[0046] The temperature of the steel strip is controlled during the cold rolling process to keep the steel strip temperature T 冷 , cold rolling process steel strip temperature T 冷 The control of and the cold rolling reduction rate η have the following relationship:

[0047] 8 / (1-η)+100≤T 冷 ≤12 / (1-η)+120 Relationship 3

[0048] Where: η = 1-b / a

[0049] Among them, in equations 1-3, V, a, b, [C], T and T 冷 In unitless form, it represents a specific value, where V is expressed in °C / s; a and b are expressed in mm; [C] is expressed in ppm. T and T 冷 The value is in °C.

[0050] In one of the embodiments, the composition and weight percentage of the ingot are: C: 0.035%-0.055%, Si: 2.5%-3.5%, Mn: 0.02%-0.05%, S: 0.003%-0.008%, Als: 0.020%-0.035%, N: 0.006%-0.01%, and the balance is Fe and unavoidable impurities.

[0051] In one embodiment, the ingot is heated to 1100-1200°C.

[0052] In one embodiment, a 20-roll rolling mill is used to cold-roll the oriented silicon steel hot-rolled plate to a finished product thickness of 0.18 mm-0.30 mm; the rolling passes are 3 times.

[0053] In one embodiment, the temperature of the steel strip is controlled during the cold rolling process by controlling the emulsion flow rate. 冷 .

[0054] The compositions of the ingots of specific examples 1-8 and comparative examples 1-2 are shown in Table 1, the heating and cold rolling process parameters are shown in Table 2, and the magnetic properties of the finished steel plates are shown in Table 3.

[0055] Table 1. Composition of the ingots in the embodiments of the present invention and the comparative examples (wt%)

[0056]

[0057]

[0058] Table 2. Relevant parameters during the preparation of Examples 1-8 and Comparative Examples 1-2

[0059]

[0060] Table 3. Performance data of steel strips obtained from Examples 1-8 and Comparative Examples 1-2

[0061]

[0062]

[0063] The extreme differences in magnetic induction and iron loss are the differences between the maximum and minimum values ​​of the magnetic induction and iron loss of the head sample, tail sample and middle sample of the steel strip.

[0064] It can be seen from Table 3 that when the induction heating process of the oriented silicon steel hot-rolled plate before cold rolling and the temperature control of the steel plate during the cold rolling process meet the scope of the technical solution of the present invention, a low-temperature high magnetic induction oriented silicon steel product with excellent and stable uniform magnetic properties can be obtained.

[0065] In Comparative Example 1, the induction heating rate of the oriented silicon steel hot-rolled plate and the maximum heating temperature of the steel plate do not satisfy the relationship equations (1) and (2) proposed in the present invention. The residence time from the time the steel strip reaches the maximum temperature to the start of the first cold rolling is too long, and the temperature of the steel plate at the start of cold rolling is too low, resulting in the inability to fully exert the pinning effect of carbides on dislocations in the steel along the rolling direction. The magnetic properties of the finished steel plate are poor, and the magnetic stability along the rolling direction is also poor.

[0066] In Comparative Example 2, the induction heating rate of the oriented silicon steel hot-rolled plate and the maximum heating temperature of the steel plate do not satisfy the relationship equations (1) and (2) proposed in the present invention, the residence time from the time the steel strip reaches the maximum temperature to the start of the first cold rolling is too long, the temperature of the steel plate at the start of cold rolling is too low, and the temperature of the steel strip during the cold rolling process does not satisfy the relationship equation (3) proposed in the present invention, the temperature of the steel strip during the cold rolling process is too low, resulting in the inability to fully exert the pinning effect of carbides on dislocations in the steel along the rolling direction, the magnetic properties of the finished steel plate are poor, and the magnetic stability along the rolling direction is also poor.

[0067] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A method for manufacturing low-temperature high magnetic induction oriented silicon steel with excellent and stable magnetic properties, characterized in that: The following steps are involved: The molten steel is smelted in a converter and continuously cast, and the ingot is heated, hot-rolled to 1.8mm-2.3mm, normalized and pickled, cold-rolled to 0.18mm-0.30mm, and then decarburized and nitrided annealed, coated with magnesium oxide annealing separator, and high-temperature annealed; coated with insulating coating liquid, and finally stretched and flattened annealed; wherein: The C content in the ingot is 350-550ppm; The steel plate is heated up to the heating temperature T at a heating speed of V. The first cold rolling is started after the steel strip reaches the temperature T. The time from the steel strip reaching the temperature T to the start of the first cold rolling is controlled within 10 minutes. The temperature of the steel plate is not less than 140°C when the cold rolling starts. The heating rate V of the steel strip has the following relationship with the hot rolled plate thickness a and the C content [C] in the ingot: [C] / (1.5×a)≤V≤[C] / (1.2×a) Relationship 1 The heating temperature T of the steel strip before cold rolling and the final thickness b of the steel plate after cold rolling and the C content [C] in the ingot have the following relationship: [C] / (10×b)≤T≤[C] / (9×b) Relationship 2 [C] / b≥1400 The temperature of the steel strip is controlled during the cold rolling process to keep the steel strip temperature T 冷 , cold rolling process steel strip temperature T 冷 The control of and the cold rolling reduction rate η have the following relationship: 8 / (1-η)+100≤T 冷 ≤12 / (1-η)+120 Relationship 3 η=1-b / a Among them, in equations 1-3, V, a, b, [C], T and T 冷 The unitless table represents a specific value, where V is expressed in °C / s; a and b are expressed in mm; [C] is expressed in ppm; T and T 冷 The value is in °C.

2. The manufacturing method according to claim 1, characterized in that: The induction heating method is used to quickly heat the steel plate to the heating temperature T at a heating rate of V.

3. The manufacturing method according to claim 1, characterized in that: The composition and weight percentage of the ingot are: C: 0.035%-0.055%, Si: 2.5%-3.5%, Mn: 0.02%-0.05%, S: 0.003%-0.008%, Als: 0.020%-0.035%, N: 0.006%-0.01%, and the balance is Fe and unavoidable impurities.

4. The manufacturing method according to claim 1, characterized in that: The ingot is heated to 1100-1200°C.

5. The manufacturing method according to claim 1, characterized in that: A 20-roll rolling mill is used to cold-roll the oriented silicon steel hot-rolled plate to a finished product thickness of 0.18 mm-0.30 mm; the rolling passes are 3 passes.

6. The manufacturing method according to claim 1, characterized in that: The temperature of the steel strip is controlled during the cold rolling process by controlling the emulsion flow rate. 冷 .

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