Preparation Method and System for Ultra-Thin Strip of High Magnetic Induction Oriented Silicon Steel

Abstract

The present invention provides a method and a system for preparing an extremely thin strip of high magnetic induction oriented silicon steel. The method includes: melting molten steel with required components to a certain temperature, stirring evenly, and then spraying it onto a rapidly rotating crystallization roll in a planar flow casting state successively through a tundish, a nozzle package, and a nozzle, so that the alloy steel liquid solidifies instantaneously to form a planar flow casting steel strip; then entering a nitrogen protection area for cooling, and automatically coiling it into a silicon steel thin strip coil by a coiler after cooling; finally, through non-uniform diameter rolling by a cold rolling mill, heating and crystallization treatment by a continuous annealing furnace, coating an Al2O3 isolation layer, and secondary crystallization in a high-temperature bell-type furnace, an extremely thin strip finished product of high magnetic induction oriented silicon steel is finally obtained. The present invention can achieve rapid solidification of molten steel, and has the advantages of simple equipment, convenient operation, large preparation quantity, dense material, and low cost.

Description

Technical Field

[0001] The present invention relates to the field of electrical steel, and more specifically, to a method and system for preparing an extremely thin strip of high magnetic induction oriented silicon steel based on a planar streamer technology. Background Art

[0002] The extremely thin oriented silicon steel is a soft magnetic material in important fields and is also one of the important materials in fields such as the electronic industry and the power industry. Compared with other magnetic property materials, it is mainly characterized by a thinner steel strip, products with higher applicable frequencies and higher magnetic induction requirements, which is beneficial to the miniaturization of products. Under the condition of meeting the product design, the extremely thin oriented silicon steel can make the iron core smaller, with the characteristics of "four highs and three lows", namely: high technical threshold, high gold content, high quality precision, high added value, small output, small market and small consumption. The main frequencies of the high magnetic induction oriented silicon steel extremely thin strip products are 400 - 3000 Hz. According to the new national standard, the thickness is 0.10 mm (0.08 mm), 0.05 mm, 0.03 mm, and the width is less than 350 mm. It is widely used in high-end industries such as reactors, precision electronics, computer components, smart hardware, power components, smart car connectors, electrical manufacturing, ship accessories, instruments, pulse navigation, medical electronics, aerospace, high-speed rail and bullet trains, communication components, precision machining, welding and cutting, laser processing, electronic materials, medical devices, military manufacturing, surface chemical treatment processing, electrical precision components, and precision machinery.

[0003] Currently, the existing production processes for high magnetic induction oriented silicon steel extremely thin strips at home and abroad are as Figure 3 shown. First, an underlyingless oriented silicon steel semi-finished product is used as the raw material. This underlyingless oriented silicon steel semi-finished product is mainly made from oriented silicon steel (HiB steel) through the following processes: through primary rolling and continuous decarburization annealing and nitriding, adding Al 2 O 3(alumina and calcium aluminate) as a separator, coated on the surface of the steel strip, and then annealed at high temperature. The purpose of high temperature annealing is: 1) to carry out secondary recrystallization. During high temperature annealing, the oriented grains in the primary recrystallization structure grow abnormally, making the steel strip a secondary recrystallization structure with a single orientation, so that the material can obtain a final product with low iron loss and high magnetic induction. 2) Purify the steel. The steel must contain necessary inclusions such as sulfides and nitrides, but if these inclusions remain in the silicon steel finished product, they will distort the lattice and become a resistance to the magnetization process, which is harmful to the magnetism. 3) By adding Al2O3 separator to MgO, a glassy film-magnesium silicate bottom layer is not formed. Then, the bottom-free oriented silicon steel semi-finished product as the raw material is sheared, weakly acid cleaned, cleaned and dried, and rolled, and the steel strip is rolled to 0.10mm, 0.08mm or 0.05mm, 0.03mm, and then surface cleaning, continuous annealing, surface coating, drying treatment, inspection, packaging, and storage are carried out. This production method mainly uses the whole process of high magnetic induction oriented silicon steel to produce bottom-free oriented silicon steel coils as the raw material of ultra-thin oriented silicon steel, and then undergoes deep processing such as cold rolling and annealing. This process is long, with low production efficiency, high production cost and low yield rate.

[0004] The thin strip continuous casting method can directly produce thin strips using liquid alloy. It is a short-process metal thin strip preparation process with great potential. The casting process uses the casting roller as a crystallizer, and the alloy liquid is in direct contact with the casting roller. The solidification structure and texture of the oriented silicon steel obtained are significantly different from those of the traditional continuous casting billet. Its sub-rapid solidification characteristics can fully inhibit the coarsening process of the second phase particles, which can fundamentally solve the disadvantages of high-temperature heating of oriented silicon steel billets and provide favorable conditions for the fine, uniform and dispersed distribution of inhibitors required for the preparation of oriented silicon steel. This technology has been successfully applied to the production of low-carbon steel, high-speed steel and other processes. However, in the production of oriented high-silicon steel, the requirements for the control of solidification structure, precipitation of inhibitors, cold working plasticity, etc. are higher. These problems are difficult to overcome, resulting in the defects of low purity, poor stability, low magnetic induction intensity and high iron loss in the oriented high-silicon steel in the prior art.

[0005] The Chinese patent CN114561597A discloses a low iron loss and high magnetic induction oriented silicon steel strip and its preparation method, whose chemical composition by mass percentage is: C: 0.003-0.008; Si: 3.0-4.0; Al: 0.5-1.0; Mn: 0.06-0.12; Cu: 0.2-0.4; N: 0.01-0.02; S: 0.004-0.02; Nb: 0.001-0.01; the rest is Fe and inevitable impurities; its preparation process is: smelting-strip casting-normalization-cold rolling-recrystallization annealing-high temperature annealing, which is characterized by using strong magnetic field annealing to control the precipitation of inhibitors and the nucleation and growth of Goss texture during the preparation process, thereby achieving precise control of the organization and texture. However, this method is difficult to achieve small size and uniform distribution of inhibitors for recrystallization annealing of thin strips under strong magnetic fields, and strong magnetic fields require more complex equipment.

[0006] The industrial continuous production method of ultra-thin strips of oriented silicon steel disclosed in Chinese patent CN113617839A includes asynchronous rolling, degreasing, heat treatment, rapid cooling, insulation coating, drying and sintering, and coil collection. The asynchronous ratio used in asynchronous rolling is 1:1.05-1:1.24. In the heat treatment process, the first step is preheating, the preheating temperature is 500℃-700℃, and the preheating time is 4 seconds-120 seconds. The second step is phase change heat treatment, the phase change heat treatment temperature is 820℃-920℃, and the phase change heating time is 100 seconds-600 seconds. In the rapid cooling process, the steel strip is cooled to below 350℃ within 30 seconds. This method only performs post-hot rolling process processing and cannot effectively control the nucleation and growth of Goss texture.

[0007] Therefore, there is an urgent need for a method for preparing ultra-thin strips of high magnetic induction oriented silicon steel that can effectively shorten the process and improve production efficiency. Summary of the invention

[0008] In view of the problems existing in the above-mentioned prior art, such as long process flow, low production efficiency, high production cost, low yield rate and precise control of organizational texture and precipitation phase during the preparation process, the purpose of the present invention is to provide a method and system for preparing ultra-thin strips of high magnetic induction oriented silicon steel based on planar streamer technology.

[0009] According to one aspect of the present invention, a method for preparing an ultra-thin strip of high magnetic induction oriented silicon steel is provided, comprising:

[0010] Step S1: Put the raw materials containing preset chemical components into a melting furnace to melt them into molten steel; among them, the raw materials contain the following elements in mass percentages: C≤0.0030%, Si: 2.5% - 6.5%, Mn: 0.15% - 0.25%, P≤0.015%, S: 0.02% - 0.05%, Als: 0.03% - 0.08%, Cu: 0.05% - 0.15%, N: 0.006% - 0.015%, Ti≤0.0030, Sn≤0.012% or Bi≤0.030%; the segregation factor Pj composed of Sn and Bi = (3*Sn / 50 + Bi / 83)*10000, satisfying the relationship: 3.5≤Pj≤9.5, and the rest are iron and inevitable impurities;

[0011] Step S2: Place the molten steel into a tundish to control the temperature and superheat of the molten steel;

[0012] Step S3: Preheat the nozzle package. After the preheating reaches the nozzle package preheating temperature, lift the flow control plug rod of the tundish to inject the molten steel in the tundish into the nozzle package. When the liquid level of the nozzle package reaches the preset height, open the nozzle to make the molten steel spray onto a high-speed rotating crystallization roll in a planar flow casting state and solidify into a planar flow casting steel strip; among them, argon protection is adopted during the planar flow casting process of the molten steel;

[0013] Step S4: Make the planar flow casting steel strip enter a nitrogen protection area for cooling. After cooling, automatically wind the planar flow casting steel strip through a coiler to obtain a silicon steel thin strip coil;

[0014] Step S5: Roll the silicon steel thin strip coil on a cold rolling mill with different diameters to obtain a cold-rolled silicon steel thin strip coil;

[0015] Step S6: Pass the cold-rolled silicon steel thin strip coil into a continuous annealing furnace, heat it to a first preset temperature to complete primary recrystallization, and then, after the steel strip cools to a second preset temperature, coat it with Al 2 O 3 isolation layer liquid, and after drying, cool it to room temperature;

[0016] Step S7: Put the silicon steel thin strip coil coated with Al 2 O 3 isolation layer into a high-temperature bell-type furnace, heat it to a third preset temperature under full hydrogen protection, keep it warm, cool it slowly, and then take it out of the furnace to complete secondary recrystallization and steel quality purification;

[0017] Step S8: Clean the surface of the silicon steel thin strip after taking it out of the furnace, coat it with an insulating coating and dry and sinter it. After finishing, inspection, packaging, and warehousing, obtain a finished product of high magnetic induction oriented silicon steel ultra-thin strip.

[0018] Among them, an optional solution is that in step S1, during the process of melting the raw material containing the preset chemical components into molten steel in the melting furnace, the temperature of the molten steel in the melting furnace is controlled at 1570 - 1670 °C; in step S2, the temperature of the molten steel in the tundish is controlled at 1550 - 1650 °C.

[0019] Among them, an optional solution is that in step S2, the temperature of the molten steel in the tundish is controlled at 1530 - 1620 °C, and the superheat of the molten steel is controlled at 25 - 55 °C.

[0020] Among them, an optional solution is that in step S3, according to Si%, the preheating temperature Ty of the nozzle package is determined as Ty = 1200 - 45 * Si%, with the unit of °C, and the preheating temperature of the nozzle package is controlled at 900 - 1100 °C.

[0021] Among them, an optional solution is that during the process of opening the nozzle to spray the molten steel onto the rapidly rotating crystallization roll in a planar flow casting state to solidify and form a planar flow casting steel strip, the fluctuation range of the liquid level in the nozzle package and the linear velocity at the roll surface of the crystallization roll are controlled; among them,

[0022] The linear velocity Vx at the roll surface of the crystallization roll is Vx = 300 + (55 - △t) / δm * 4, with the unit of m / min, where △t is the superheat, with the unit of °C; δm is the target thickness of the cast strip, with the unit of mm; the fluctuation range of the liquid level in the nozzle package is controlled within ±2 mm, and the linear velocity at the roll surface of the crystallization roll is controlled at 300 - 1200 m / min.

[0023] Among them, an optional solution is that the molten steel is protected by argon during the planar flow casting process, and the flow rate Ya of the argon is controlled according to the melting temperature Tg of the molten steel as Ya = 12 + △t / 2, with the unit of L / min;

[0024] The planar flow casting steel strip enters the nitrogen protection area for cooling to below 200 °C, and is automatically coiled by a coiler to obtain a silicon steel thin strip coil with a thickness of 0.08 - 0.18 mm.

[0025] Among them, an optional solution is that during the process of performing non-uniform diameter rolling on the silicon steel thin strip coil on a cold rolling mill,

[0026] The roll diameter ratio λ of the non-uniform diameter rolling is λ = 400×δs / τ, where s is the actual thickness of the cast strip, with the unit of mm, and τ is the cold rolling target reduction ratio; the roll diameter ratio is controlled at 0.8 - 1.8; the reduction ratio of the non-uniform diameter rolling is controlled between 35% and 60%;

[0027] The thickness of the silicon steel thin strip coil obtained after cold rolling is 0.05 - 0.10 mm.

[0028] Among them, an optional solution is that the first preset temperature is 750°C to 950°C. After the cold-rolled silicon steel strip coil is fed into a continuous annealing furnace and heated to the first preset temperature, the holding time is 25 to 60 s, and then it is cooled to room temperature. In an environment where the furnace atmosphere N 2 、H 2 mixed dry gas, H 2 / N 2 with a volume ratio of 20% to 80%, an Al 2 O 3 isolation layer liquid is coated on the silicon steel strip coil, and after drying, it is cooled to room temperature.

[0029] Among them, an optional solution is that the third temperature is 1050 to 1200°C, the holding time is 2.5 to 25 h, and it is slowly cooled to below 200°C and then taken out of the furnace.

[0030] Among them, an optional solution is that according to another aspect of the present invention, a preparation system for an ultra-thin strip of high magnetic induction oriented silicon steel is provided, including a melting furnace, a tundish, a crystallizing roll, a coiler, a cold rolling mill, a continuous annealing furnace and a high-temperature bell-type furnace. Among them,

[0031] the melting furnace is used to melt raw materials containing preset chemical components into molten steel; among them, the raw materials contain the following elements in mass percentages: C≤0.0030%, Si: 2.5% to 6.5%, Mn: 0.15% to 0.25%, P≤0.015%, S: 0.02% to 0.05%, Als: 0.03% to 0.08%, Cu: 0.05% to 0.15%, N: 0.006% to 0.015%, Ti≤0.0030, Sn≤0.012% or Bi≤0.030%; the segregation factor Pj composed of Sn and Bi = (3*Sn / 50 + Bi / 83)*10000, satisfying the relationship: 3.5≤Pj≤9.5, and the rest are iron and inevitable impurities;

[0032] the tundish is used to receive the molten steel for planar flow casting to control the temperature and superheat of the molten steel; among them, a nozzle package is arranged at the lower part of the tundish. Before planar flow casting, the nozzle package is preheated first. After the preheating reaches the nozzle package preheating temperature, the flow control plug rod of the tundish is lifted to inject the molten steel in the tundish into the nozzle package. When the liquid level of the nozzle package reaches the preset height, the nozzle is opened to spray the molten steel onto the high-speed rotating crystallizing roll in a planar flow casting state to solidify and form a planar flow casting steel strip; among them, argon protection is adopted during the planar flow casting of the molten steel;

[0033] the coiler is used to automatically coil the planar flow casting steel strip after the planar flow casting steel strip enters the nitrogen protection area for cooling to obtain a silicon steel strip coil;

[0034] The cold rolling mill is used for performing unequal-diameter rolling on the silicon steel strip coil to obtain a cold-rolled silicon steel strip coil;

[0035] The continuous annealing furnace is used to heat the cold-rolled silicon steel strip coil to a first preset temperature to complete primary recrystallization. Then, after the steel strip is cooled to a second preset temperature, Al 2 O 3 is coated with an isolation layer liquid, and after drying, it is cooled to room temperature;

[0036] The high-temperature bell-type furnace is used to heat the silicon steel strip coil coated with Al 2 O 3 isolation layer to a third preset temperature under full hydrogen protection, keep it warm, cool it slowly, and then take it out of the furnace to complete secondary recrystallization and steel quality purification;

[0037] After the silicon steel strip is taken out of the furnace, it is surface-cleaned, coated with an insulating coating, dried and sintered, and then finished, inspected, packaged, and stored in the warehouse to obtain a finished product of high magnetic induction oriented silicon steel ultra-thin strip.

[0038] The above-mentioned method and system for preparing high magnetic induction oriented silicon steel ultra-thin strip according to the present invention melts the required component steel liquid to a certain temperature, stirs it evenly, and then uniformly pours it onto the crystallizing roll through the tundish (bottom-pouring furnace), nozzle package, and nozzle. There is cooling water inside the crystallizing roll. Through the high-speed rotation of the crystallizing roll, the alloy steel liquid is instantaneously solidified to form an ultra-thin planar flow strip. Compared with the prior art, the present invention has the following technical advantages:

[0039] (1) The planar flow casting process of ultra-rapid solidification and the temperature reduction process of ultra-rapid cooling are adopted to obtain an ultra-thin silicon steel strip, which shortens the process flow and is beneficial to energy conservation and carbon reduction; the planar flow casting process of ultra-rapid solidification solves the problem of silicon steel strip forming, and the temperature reduction process of ultra-rapid cooling realizes the uniformity, fineness, and dispersion of the precipitated phases inside the silicon steel strip, achieving the purpose of suppressing the growth of primary recrystallization grains.

[0040] (2) The raw material selects a super-low-carbon composition design, eliminating the decarburization process in the subsequent process;

[0041] (3) The planar flow casting process adopts a protective atmosphere throughout to avoid oxidation of the steel strip, and pickling is not required in the subsequent process;

[0042] (4) Unequal-diameter rolling is adopted by the cold rolling mill, effectively reducing the rolling force and improving the strip shape. It is easy to form a sharp {111}<112> texture in the rolling direction, and high magnetic induction finished products are obtained after high-temperature heat treatment.

[0043] It can be seen from the above technical advantages that the present invention is a planar flow casting process with an ultra-short process flow, which can achieve rapid solidification of molten steel, and has the advantages of simple equipment, convenient operation, large preparation volume, dense material, and low cost.

[0044] In order to achieve the above and related purposes, one or more aspects of the present invention include features that will be described in detail later and are particularly pointed out in the claims. The following description and the accompanying drawings describe some exemplary aspects of the present invention in detail. However, these aspects indicate only some of the various ways in which the principles of the present invention can be used. In addition, the present invention is intended to include all of these aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] By referring to the following description and claims in conjunction with the accompanying drawings, and with a more comprehensive understanding of the present invention, other objects and results of the present invention will become more apparent and easier to understand. In the accompanying drawings:

[0046] Figure 1 This is a flow chart of a method for preparing an ultra-thin strip of high magnetic induction oriented silicon steel according to an embodiment of the present invention;

[0047] Figure 2 A process flow chart of preparing an ultra-thin strip of high magnetic induction oriented silicon steel by plane streamer according to an embodiment of the present invention; and

[0048] Figure 3 This is a process flow chart for the existing production of ultra-thin strips of high magnetic induction oriented silicon steel.

[0049] The same reference numerals throughout the drawings indicate similar or corresponding features or functions. DETAILED DESCRIPTION

[0050] In the following description, for the purpose of illustration, in order to provide a comprehensive understanding of one or more embodiments, to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, many specific details are set forth. However, it is obvious that these embodiments can also be implemented without these specific details, and the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In other examples, in order to facilitate the description of one or more embodiments, known structures and devices are shown in the form of block diagrams.

[0051] In order to solve the problems in the existing process technology of high magnetic induction oriented silicon steel ultra-thin strip, such as long process flow, low production efficiency, high production cost, low yield rate and precise control of organizational texture and precipitation phase during the preparation process, the present invention provides a solution for preparing high magnetic induction oriented silicon steel ultra-thin strip based on planar stream casting process.

[0052] Through the present invention, the planar flow casting steel strip is solidified and formed under argon protection and the cooling rate is controlled under nitrogen protection, obtaining a silicon steel strip with fine grains, uniform structure, and uniform and dispersed precipitation of inhibitors such as MnS and AlN; the silicon steel strip is then subjected to unequal diameter rolling by a cold rolling mill, generating a large stress and strain gradient inside, increasing the distortion energy in the cold rolled strip steel. In this way, during high-temperature annealing, the number of recrystallized grains driven by this stored energy as the recrystallization driving force will increase significantly, and there are more η textures, and the grains with {110}<001> orientation increase; in addition, due to the genetic effect of the texture, it helps to form a perfect Goss texture, thereby improving the magnetic properties of the finished silicon steel ultra-thin strip.

[0053] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0054] Figure 1 and Figure 2 respectively show the flow of the method for preparing a high magnetic induction oriented silicon steel ultra-thin strip and the process flow of preparing a high magnetic induction oriented silicon steel ultra-thin strip by planar flow casting according to an embodiment of the present invention.

[0055] As Figure 1 and Figure 2 jointly shown, the method for preparing a high magnetic induction oriented silicon steel ultra-thin strip provided by the present invention mainly includes the following eight steps:

[0056] Step S1: Put the raw materials containing preset chemical components into a melting furnace to melt them into molten steel; wherein, the raw materials contain the following elements by mass percentage: C≤0.0030%, Si: 2.5% - 6.5%, Mn: 0.15% - 0.25%, P≤0.015%, S: 0.02% - 0.05%, Als: 0.03% - 0.08%, Cu: 0.05% - 0.15%, N: 0.006% - 0.015%, Ti≤0.0030, Sn≤0.012% or Bi≤0.030%; the segregation factor Pj composed of Sn and Bi = (3*Sn / 50 + Bi / 83)*10000, satisfying the relationship: 3.5≤Pj≤9.5, and the rest are iron and inevitable impurities.

[0057] Among them, during the process of putting the raw materials containing preset chemical components into a melting furnace to melt them into molten steel, the temperature of the molten steel needs to be controlled. In a specific embodiment of the present invention, the temperature of the molten steel in the melting furnace is controlled at 1570 - 1670°C.

[0058] Step S2: Place the molten steel into (such as pour it into) a tundish (also called a bottom-pouring furnace) to control the temperature and superheat of the molten steel.

[0059] The tundish has the functions of heating and heat preservation, and can conveniently control the superheat of the molten steel. In a specific embodiment of the present invention, the temperature of the molten steel in the tundish is controlled within 1550 - 1650 °C, and a more preferred control temperature is 1530 - 1620 °C. In addition, the superheat of the molten steel is controlled within 25 - 55 °C through the tundish.

[0060] Step S3: Preheat the nozzle package. After the preheating reaches the preheating temperature of the nozzle package, lift the flow control plug rod of the tundish to inject the molten steel in the tundish into the nozzle package. When the liquid level of the nozzle package reaches the preset height (such as: 240 mm ± 2 mm), open the nozzle to make the molten steel spray onto the high-speed rotating crystallization roll in a planar flow casting state and solidify into a planar flow casting steel strip; wherein, argon protection is adopted during the process of planar flow casting of the molten steel.

[0061] In order to make the molten steel in planar flow casting maintain a consistent temperature during the planar retention process and improve the solidification effect, natural gas needs to be ignited to preheat the nozzle package before pouring, and pouring can only be carried out after reaching a certain temperature.

[0062] Specifically, as an example, the preheating temperature Ty of the nozzle package can be determined according to Si% as Ty = 1200 - 45 * Si%, with the unit of °C. In a specific embodiment of the present invention, the preheating temperature of the nozzle package is controlled within 900 - 1100 °C.

[0063] During the process of opening the nozzle to make the molten steel spray onto the high-speed rotating crystallization roll in a planar flow casting state and solidify into a planar flow casting steel strip, control the fluctuation range of the liquid level in the nozzle package and the linear velocity at the roll surface of the crystallization roll. Specifically, as an example, in a specific embodiment of the present invention, the linear velocity Vx at the roll surface of the crystallization roll is Vx = 300 + (55 - △t) / δm * 4, with the unit of m / min, where △t is the superheat, with the unit of °C; δm is the target thickness of the cast strip, with the unit of mm; the fluctuation range of the liquid level in the nozzle package is controlled within ±2 mm, and the linear velocity at the roll surface of the crystallization roll is controlled within 300 - 1200 m / min.

[0064] Step S4: Make the planar flow casting steel strip enter the nitrogen protection area for cooling, and after cooling, automatically wind the planar flow casting steel strip through a coiler to obtain a silicon steel thin strip coil.

[0065] During the process of planar flow casting of the molten steel, that is, from the starting position of planar flow casting to the position where the steel strip is formed, argon protection is adopted. Specifically, the flow rate Ya of argon can be controlled according to the melting temperature Tg of the molten steel as Ya = 12 + △t / 2, with the unit of L / min; the planar flow casting steel strip enters the nitrogen protection area for cooling to below 200 °C, and is automatically wound through a coiler, and a silicon steel thin strip coil with a thickness of 0.08 - 0.18 mm can be obtained.

[0066] Step S5: Wind the silicon steel strip onto a cold rolling mill for unequal-diameter rolling to obtain a cold-rolled silicon steel strip coil.

[0067] During the process of winding the silicon steel strip onto a cold rolling mill for unequal-diameter rolling, the roll diameter ratio λ of the unequal-diameter rolling is 400×δs / τ, where s is the actual thickness of the cast strip in mm and τ is the cold rolling target reduction ratio; the roll diameter ratio is controlled within 0.8 - 1.8; the reduction ratio of the unequal-diameter rolling is controlled between 35% and 60%. The thickness of the cold-rolled silicon steel strip coil obtained is 0.05 - 0.10 mm, and the thickness of the silicon steel strip coil is further reduced.

[0068] Step S6: Pass the cold-rolled silicon steel strip coil into a continuous annealing furnace, heat it to a first preset temperature to complete primary recrystallization, and then, after the steel strip is cooled to a second preset temperature, coat it with Al 2 O 3 isolation layer liquid, and cool it to room temperature after drying.

[0069] Among them, the first preset temperature is 750°C - 950°C. After passing the cold-rolled silicon steel strip coil into the continuous annealing furnace and heating it to the first preset temperature, the holding time is 25 - 60 s, and then it is cooled to room temperature. In the furnace atmosphere N 2 、H 2 mixed dry gas, and in an environment where the volume ratio of H 2 / N 2 is 20% - 80%, coat the silicon steel strip coil with Al 2 O 3 isolation layer liquid, and cool it to room temperature after drying.

[0070] Step S7: Put the silicon steel strip coil coated with Al 2 O 3 isolation layer into a high-temperature bell-type furnace, heat it to a third preset temperature under full hydrogen protection, hold the temperature, cool it slowly, and then take it out of the furnace to complete secondary recrystallization and steel purification. Specifically, as an example, the third temperature is 1050 - 1200°C, the holding time is 2.5 - 25 h, and it can be taken out of the furnace after slowly cooling to below 200°C.

[0071] Step S8: Clean the surface of the silicon steel strip after taking it out of the furnace, coat an insulating coating and dry and sinter it, and then obtain the finished product of high magnetic induction oriented silicon steel ultra-thin strip through finishing, inspection, packaging, and warehousing.

[0072] Finally, the magnetic properties of the finished product of the oriented silicon steel ultra-thin strip can be detected.

[0073] The working principle of the present invention is as follows:

[0074] The present invention relates to a planar flow casting process with an ultra-short process flow, that is, the required molten steel of the composition is melted to a certain temperature, stirred evenly, and then successively poured onto a crystallizing roll through a tundish (bottom-pouring furnace), a nozzle package, and a nozzle evenly. Cooling water is passed through the inside of the crystallizing roll. Through the high-speed rotation of the crystallizing roll, the alloy steel liquid solidifies instantaneously to form an extremely thin strip of silicon steel. Therefore, the extremely thin strip of silicon steel formed by using this planar flow casting process is also called a planar flow casting steel strip.

[0075] The planar flow casting steel strip is solidified and formed under argon protection and cooled down under nitrogen protection to obtain a silicon steel thin strip with fine grains, uniform structure, and uniform and dispersed precipitation of inhibitors such as MnS and AlN. The silicon steel thin strip is then subjected to unequal-diameter rolling by a cold rolling mill, generating a large stress and strain gradient inside, increasing the distortion energy in the cold-rolled strip steel. In this way, during high-temperature annealing, the number of recrystallized grains driven by this stored energy as the recrystallization driving force will increase significantly, and there are more η textures, and the grains with {110}<001> orientation increase. In addition, due to the genetic effect of the texture, it helps to form a perfect Goss texture, thereby improving the magnetic properties.

[0076] In addition, due to the high surface-to-volume ratio of the silicon steel thin strip, the surface energy plays an important role in grain growth. The surface energies of grains with different orientations are different, which is related to the atom-dense plane. Grains with low surface energy can grow preferentially. The surface energy of (110) plane grains is the lowest, followed by (100) plane, and the highest is (111) plane. The thinner the strip, the greater the role played by the surface energy, the greater the driving force for recrystallized grain growth, and the easier the grain growth. When producing non-oriented silicon steel thin strips, due to the different abilities of grains with different crystal planes to adsorb impurity atoms on their free surfaces, by controlling the atmosphere during annealing, a trace amount of strongly polar gas hydrogen sulfide is added to the pure hydrogen atmosphere. As an impurity, it will be adsorbed onto grains with different orientations. The adsorbed hydrogen sulfide gas can reduce the surface energy of the grains. Among these crystal planes, the (100) plane is the most easily adsorbed, ultimately resulting in the lowest surface energy of the (100) plane grains, and the grains of this orientation grow preferentially compared to the (110) plane, inhibiting the development of the Goss texture beneficial to the properties of oriented silicon steel.

[0077] Compared with ordinary grain-oriented silicon steel, there are problems such as insufficient precipitation of traditional inherent inhibitors (MnS, MnSe, AlN, etc.) and limited addition amounts of grain boundary segregation elements (Sn, Sb, etc.) in high-silicon grain-oriented steel, resulting in increased difficulty in matching the microstructure-texture-inhibitor during the high-temperature annealing process. Therefore, selecting a suitable inhibitor and matching reasonable microstructure and texture control processes are the keys to developing a technology for preparing high-silicon grain-oriented steel by rapid annealing. During the preparation of high-silicon grain-oriented steel, the inhibitor precipitates dispersively during the hot rolling stage and redissolves and coarsens during the subsequent deformation and annealing processes. During the primary recrystallization process, the inhibitor regulates the grain growth behavior and refines the microstructure. During the final annealing stage, the inhibitor hinders the growth of matrix grains and induces abnormal growth of certain oriented grains, ultimately completing secondary recrystallization.

[0078] Selecting a suitable inhibitor needs to meet the following conditions:

[0079] (1) Before the start of secondary recrystallization, as second-phase particles, the inhibitor is uniformly distributed on the grain boundaries of recrystallized grains;

[0080] (2) During the secondary recrystallization process, as the temperature increases, the inhibitor undergoes ripening and its ability to pin grain boundaries decreases;

[0081] (3) The inhibitor decomposes under high temperature and special atmospheres, reducing the impact on the magnetic properties of the alloy.

[0082] Among them, the precipitation behavior of the inhibitor during hot rolling and the failure behavior during the secondary recrystallization annealing process are the key factors determining the secondary recrystallization behavior and quality. Therefore, in the chemical composition of the present invention, a combination of traditional inherent inhibitors (MnS, AlN, Cu2S) and grain boundary segregation elements (Sn, Bi) is adopted to further strengthen the role of the precipitated phase.

[0083] The following Table 1 is a list of the chemical compositions and segregation factors of each example and comparative example

[0084] Table 1

[0085]

[0086]

[0087] As shown in Table 1 above, it can be obtained that:

[0088] 1) The segregation factor Pj = (3*Sn / 50 + Bi / 83)*10000;

[0089] 2) Comparative example 1 is the comparative example of Example 1 because S = 0.065% is higher than that of Example 1; Comparative example 2 is the comparative example of Example 6 because N = 0.0023% is lower than N = 0.0129% of Example 6; Comparative example 3 is the comparative example of Example 8 because it has no Sn and no Bi; Comparative example 4 is the comparative example of Example 10 because Ti = 0.0048% > 0.0030%.

[0090] Table 2 below is a list of process parameters implemented for each example and comparative example

[0091] Table 2 (I)

[0092]

[0093] In Table 2 (I) above, the superheat of molten steel Δt = Tg - Td during bottom pouring, with the unit of °C; the nozzle preheating temperature Ty = 1200 - 45 * Si%, with the unit of °C; the crystallizing roll linear speed Vx = 300 + (55 - Δt) / δm * 4, with the unit of m / min; the argon flow rate Ya = 12 + Δt / 2, with the unit of L / min.

[0094] Table 2 (II)

[0095]

[0096] In Table (II) above, the cold rolling target reduction ratio τ = (δm - δL) / δm; the roll diameter ratio λ of unequal diameter rolling = 400 × δs / τ.

[0097] The present invention adopts unequal diameter rolling, and its texture components are basically similar to those of synchronous rolling, but there are differences in the strength and symmetry of the texture distribution. At the same time, unequal diameter rolling helps to improve the cold rolling texture, strengthen the γ texture on the slow roll side, and suppress the α texture. With the increase of the asynchronous speed ratio, this increase does not increase linearly. Therefore, the formation and distribution of the metal cold rolling texture are closely related to the stress state in the deformation zone.

[0098] Under the condition of unequal-diameter rolling, due to the opposite acting directions of the frictions of the upper and lower rolls on the steel, a rubbing rolling zone is formed in the deformation zone. This shearing causes a certain shear strain. Since the acting directions of this shear strain are opposite in the metal deformations of adjacent passes, after a reciprocating reversible rolling process, the influence of this shear strain on the thin strip can be generally offset. That is, under the condition of unequal-diameter rolling, since the external force acting on the deformation zone is still mainly the rolling pressure and the texture still has good macroscopic statistics, the rotation mode of grains and the cold-rolled texture components are similar to those of synchronous rolling in many aspects. However, under the condition of unequal-diameter rolling, due to the existence of the rubbing rolling zone, the cold-rolled texture components are asymmetric in the thickness direction. Under the condition of synchronous rolling, there are certain strengths and amounts of α texture in the surface layer and the middle layer of the thin strip, and these components are relatively stable during subsequent high-temperature annealing, which is not conducive to the development of the cubic recrystallization Goss texture. However, under the condition of unequal-diameter rolling, the strengths of these components are relatively very low (basically equal in the lower surface layer), and there is no concentration in the (001)<110> orientation, which indicates that the shear strain can effectively inhibit the formation of unfavorable texture components. At the same time, this shear strain makes the strengths and amounts of the {111}<112> texture in the surface layer and the middle layer relatively increase, and since the reduction rate per pass is higher than that of synchronous rolling, the shear deformation of the cold-rolled sheet surface layer is more obvious, and the enhancement of these texture components is conducive to the occurrence of cubic recrystallization. As the speed ratio increases, the η texture increases. With the increase of the asynchronous speed ratio, the number of Goss crystal nuclei also increases.

[0099] Table 3 below shows the detected magnetic property lists of each example and comparative example.

[0100] Table 3

[0101]

[0102]

[0103] As can be seen from Table 3 above, Comparative Example 1 is a comparative example of Example 2 because S = 0.065% is higher than S = 0.046% in Example 2. The magnetic properties of Example 2, B800 = 1.94T and P1.0 / 400 = 6.40W / Kg, are significantly better than those of Comparative Example 1, B800 = 1.84T and P1.0 / 400 = 7.22W / Kg; Comparative Example 2 is a comparative example of Example 6 because N = 0.0023% is lower than N = 0.0129% in Example 6. The magnetic properties of Example 6, B800 = 1.84T and P1.0 / 400 = 6.12W / Kg, are significantly better than those of Comparative Example 2, B800 = 1.78T and P1.0 / 400 = 7.60W / Kg; Comparative Example 3 is a comparative example of Example 8 (Sn: 0.0091%, Bi: 0.015%) because of none, none. The magnetic properties of Example 8, B800 = 1.78T and P1.0 / 400 = 6.50W / Kg, are significantly better than those of Comparative Example 3, B800 = 1.66T and P1.0 / 400 = 6.84W / Kg; Comparative Example 4 is a comparative example of Example 10 because Ti = 0.0048% > 0.0030%. The magnetic properties of Example 10, B800 = 1.74T and P1.0 / 400 = 5.60W / Kg, are significantly better than those of Comparative Example 4, B800 = 1.56T and P1.0 / 400 = 7.81W / Kg. Thus, compared with the comparative examples, the high magnetic induction oriented high silicon steel ultra-thin strip obtained in the embodiments of the present invention has excellent magnetic properties.

[0104] As referred to above Figure 1 and Figure 2 The preparation method of the high magnetic induction oriented silicon steel ultra-thin strip according to the present invention is described. Corresponding to the preparation method of the high magnetic induction oriented silicon steel ultra-thin strip, the present invention also provides a high magnetic induction oriented silicon steel ultra-thin strip preparation system applying the above-mentioned preparation method of the high magnetic induction oriented silicon steel ultra-thin strip, which mainly includes equipment such as a melting furnace, a tundish, a nozzle package, a nozzle, a crystallization roll, a coiler, a cold rolling mill, a continuous annealing furnace, and a high-temperature bell-type furnace.

[0105] The melting furnace is used to melt the raw materials containing preset chemical components into molten steel; wherein, the raw materials contain the following elements in mass percentages: C ≤ 0.0030%, Si: 2.5% - 6.5%, Mn: 0.15% - 0.25%, P ≤ 0.015%, S: 0.02% - 0.05%, Als: 0.03% - 0.08%, Cu: 0.05% - 0.15%, N: 0.006% - 0.015%, Ti ≤ 0.0030, Sn ≤ 0.012% or Bi ≤ 0.030%; the segregation factor Pj composed of Sn and Bi = (3*Sn / 50 + Bi / 83)*10000, satisfying the relationship: 3.5 ≤ Pj ≤ 9.5, and the rest are iron and inevitable impurities;

[0106] The tundish is used to store the molten steel for planar flow casting to control the temperature and superheat of the molten steel. Wherein, a nozzle package is arranged at the lower part of the tundish. Before planar flow casting, the nozzle package is preheated first. After the preheating reaches the preheating temperature of the nozzle package, the flow control plug rod of the tundish is lifted to inject the molten steel in the tundish into the nozzle package. When the liquid level of the nozzle package reaches the preset height, the nozzle is opened to spray the molten steel onto a high-speed rotating crystallizing roll in a planar flow casting state to solidify and form a planar flow casting steel strip. Wherein, argon protection is adopted during the planar flow casting process of the molten steel;

[0107] The coiler is used to automatically coil the planar flow casting steel strip after the planar flow casting steel strip enters the nitrogen protection area for cooling to obtain a silicon steel thin strip coil;

[0108] The cold rolling mill is used to perform unequal-diameter rolling on the silicon steel thin strip coil to obtain a cold-rolled silicon steel thin strip coil;

[0109] The continuous annealing furnace is used to heat the cold-rolled silicon steel thin strip coil to a first preset temperature to complete primary recrystallization. Then, after the steel strip is cooled to a second preset temperature, Al 2 O 3 isolation layer liquid is coated, and after drying, it is cooled to room temperature;

[0110] The high-temperature bell-type furnace is used to heat the silicon steel thin strip coil coated with Al 2 O 3 isolation layer to a third preset temperature under full hydrogen protection, keep it warm, slow-cool it, and take it out of the furnace to complete secondary recrystallization and steel quality purification;

[0111] After the silicon steel thin strip is taken out of the furnace, it is surface-cleaned, coated with an insulating coating and dried and sintered, and after finishing, inspection, packaging, and warehousing, a finished product of high magnetic induction oriented silicon steel ultra-thin strip is obtained.

[0112] For a more specific implementation manner of the above high magnetic induction oriented silicon steel ultra-thin strip preparation system, reference can be made to the foregoing description of the embodiments of the high magnetic induction oriented silicon steel ultra-thin strip preparation method, which will not be elaborated herein one by one.

[0113] As described above by way of example with reference to the drawings, the method and system for preparing a high magnetic induction oriented silicon steel ultra-thin strip according to the present invention are described. However, those skilled in the art should understand that various improvements can be made to the above method and system for preparing a high magnetic induction oriented silicon steel ultra-thin strip proposed by the present invention without departing from the content of the present invention. Therefore, the protection scope of the present invention should be determined by the content of the appended claims.

Claims

1. A method for preparing an extremely thin strip of high magnetic induction oriented silicon steel, characterized in that, it includes: Step S1: Put the raw materials containing preset chemical components into a melting furnace to melt into molten steel; wherein, the raw materials contain the following elements by mass percentage: C≤0.0030%, Si: 2.5% - 6.5%, Mn: 0.15% - 0.25%, P≤0.015%, S: 0.02% - 0.05%, Als: 0.03% - 0.08%, Cu: 0.05% - 0.15%, N: 0.006% - 0.015%, Ti≤0.0030%, Sn ≤0.012% or Bi ≤0.030%; The segregation factor Pj composed of Sn and Bi = (3*Sn / 50 + Bi / 83)*10000, satisfying the relationship: 3.5≤Pj≤9.5, and the rest are iron and inevitable impurities; Step S2: Place the molten steel into a tundish to control the temperature and superheat of the molten steel; Step S3: Preheat the nozzle package. After the preheating reaches the preheating temperature of the nozzle package, lift the flow control plug rod of the tundish to inject the molten steel in the tundish into the nozzle package. When the liquid level of the nozzle package reaches the preset height, open the nozzle to spray the molten steel onto a high-speed rotating crystallization roll in a planar flow casting state to solidify and form a planar flow casting steel strip; wherein, the linear velocity Vx at the roll surface of the crystallization roll = 300 + (55 - △t) / δm * 4, with the unit of m / min, where △t is the superheat, with the unit of °C; δm is the target thickness of the cast strip, with the unit of mm; the fluctuation range of the liquid level in the nozzle package is controlled within ±2mm, the linear velocity at the roll surface of the crystallization roll is controlled within 300 - 1200m / min, and argon protection is adopted during the planar flow casting process of the molten steel. According to the melting temperature Tg of the molten steel, control the argon flow rate Ya = 12 + △t / 2, with the unit of L / min; where △t is the difference between the melting temperature Tg of the molten steel and the tundish molten steel temperature; Step S4: Let the planar flow casting steel strip enter a nitrogen protection area for cooling. After cooling down to below 200°C, automatically wind up the planar flow casting steel strip through a coiler to obtain a silicon steel thin strip coil with a thickness of 0.08 - 0.18mm; Step S5: Perform non-uniform diameter rolling on the silicon steel thin strip coil on a cold rolling mill to obtain a silicon steel thin strip coil with a thickness of 0.05 - 0.10mm after cold rolling; wherein, the roll diameter ratio λ of the non-uniform diameter rolling = 400×δs / τ, where δs is the actual thickness of the cast strip, with the unit of mm, and τ is the cold rolling target reduction ratio; the roll diameter ratio is controlled within 0.8 - 1.8; the reduction ratio of the non-uniform diameter rolling is controlled between 35% - 60%; Step S6: Feed the cold-rolled silicon steel strip coil into a continuous annealing furnace, heat it to a first preset temperature to complete primary recrystallization, and then, after the steel strip is cooled to a second preset temperature, coat it with Al 2 O 3 isolation layer liquid, and after drying, cool it to room temperature; Step S7: Put the silicon steel strip coil coated with Al 2 O 3 isolation layer into a high-temperature bell-type furnace, heat it to the third preset temperature under full hydrogen protection, keep it warm, cool it slowly, and then take it out of the furnace to complete secondary recrystallization and steel purification; Step S8: Clean the surface of the silicon steel thin strip after it comes out of the furnace, coat an insulating coating and dry and sinter it. After finishing, inspection, packaging, and warehousing, obtain the finished product of the extremely thin strip of high magnetic induction oriented silicon steel.

2. The method for preparing an extremely thin strip of high magnetic induction oriented silicon steel according to claim 1, characterized in that, During the process of melting the raw material containing a preset chemical composition into molten steel in a melting furnace, the temperature of the molten steel in the melting furnace is controlled at 1570 - 1670 °C; In step S2, the temperature of the molten steel in the tundish is controlled at 1550 - 1650 °C.

3. The method for preparing a high magnetic induction oriented silicon steel ultra-thin strip as described in claim 2, characterized in that, In step S2, the temperature of the molten steel in the tundish is controlled at 1530 - 1620 °C, and the superheat of the molten steel is controlled at 25 - 55 °C.

4. The method for preparing a high magnetic induction oriented silicon steel ultra-thin strip as described in claim 1, characterized in that, In step S3, the preheating temperature Ty of the nozzle package is determined according to Si% as Ty = 1200 - 45 * Si%, with the unit of °C, and the preheating temperature of the nozzle package is controlled at 900 - 1100 °C.

5. The method for preparing a high magnetic induction oriented silicon steel ultra-thin strip as described in claim 1, characterized in that, The first preset temperature is 750°C to 950°C. After passing the cold-rolled silicon steel strip coil into a continuous annealing furnace and heating it to the first preset temperature, keep it warm for 25 to 60 s, and then cool it to the second preset temperature. The furnace atmosphere in the continuous annealing furnace is N 2 , H 2 mixed dry gas, and H 2 / N 2 under the environment with a volume ratio of 20% to 80%, coat the silicon steel strip coil with Al 2 O 3 isolation layer liquid, and after drying, cool it to room temperature.

6. The method for preparing a high magnetic induction oriented silicon steel ultra-thin strip as described in claim 1, characterized in that, The third preset temperature is 1050 - 1200 °C, the heat preservation time is 2.5 - 25 h, and it is slowly cooled to below 200 °C and then taken out of the furnace.

7. A system for preparing a high magnetic induction oriented silicon steel ultra-thin strip, characterized in that, It includes a melting furnace, a tundish, a crystallizing roll, a coiler, a cold rolling mill, a continuous annealing furnace, and a high-temperature bell-type furnace. Among them, The melting furnace is used to melt the raw material containing a preset chemical composition into molten steel; among them, the raw material contains the following elements by mass percentage: C ≤ 0.0030%, Si: 2.5% - 6.5%, Mn: 0.15% - 0.25%, P ≤ 0.015%, S: 0.02% - 0.05%, Als: 0.03% - 0.08%, Cu: 0.05% - 0.15%, N: 0.006% - 0.015%, Ti ≤ 0.0030%, Sn ≤ 0.012% or Bi ≤ 0.030%; the segregation factor Pj composed of Sn and Bi is Pj = (3 * Sn / 50 + Bi / 83) * 10000, satisfying the relationship: 3.5 ≤ Pj ≤ 9.5, and the rest are iron and inevitable impurities; The tundish is used to store the molten steel for strip casting to control the temperature and superheat of the molten steel. Among them, a nozzle package is arranged at the lower part of the tundish. Before strip casting, the nozzle package is preheated first. After the preheating reaches the preheating temperature of the nozzle package, the flow control plug rod of the tundish is lifted to inject the molten steel in the tundish into the nozzle package. When the liquid level of the nozzle package reaches the preset height, the nozzle is opened to spray the molten steel onto the high-speed rotating crystallization roll in a strip casting state to solidify and form a strip casting steel strip. Among them, the linear velocity Vx at the roll surface of the crystallization roll is 300 + (55 - △t) / δm * 4, with the unit of m / min, where △t is the superheat with the unit of °C; δm is the target thickness of the cast strip with the unit of mm. The fluctuation range of the liquid level in the nozzle package is controlled within ±2 mm, and the linear velocity at the roll surface of the crystallization roll is controlled within 300 - 1200 m / min. During the strip casting process of the molten steel, argon protection is adopted, and the flow rate Ya of argon is controlled according to the melting temperature Tg of the molten steel, Ya = 12 + △t / 2, with the unit of L / min, where △t is the difference between the melting temperature Tg of the molten steel and the temperature of the molten steel in the tundish. The coiler is used to automatically coil the strip casting steel strip after the strip casting steel strip enters the nitrogen protection area for cooling to below 200 °C to obtain a silicon steel thin strip coil with a thickness of 0.08 - 0.18 mm. The cold rolling mill is used to perform unequal-diameter rolling on the silicon steel thin strip coil to obtain a silicon steel thin strip coil with a thickness of 0.05 - 0.10 mm after cold rolling. Among them, the roll diameter ratio λ of the unequal-diameter rolling is 400×δs / τ, where δs is the actual thickness of the cast strip with the unit of mm, and τ is the target cold rolling reduction rate. The roll diameter ratio is controlled within 0.8 - 1.

8. The reduction rate of the unequal-diameter rolling is controlled between 35% - 60%. The continuous annealing furnace is used to heat the cold-rolled silicon steel strip coil to a first preset temperature to complete primary recrystallization. Then, after the steel strip is cooled to a second preset temperature, an Al 2 O 3 isolation layer liquid is coated, and after drying, it is cooled to room temperature; The high-temperature bell-type furnace is used to heat a silicon steel strip coil coated with an Al 2 O 3 isolation layer to a third preset temperature under full hydrogen protection, hold the temperature, cool slowly, and then take the furnace out to complete secondary recrystallization and steel purification; The silicon steel thin strip after being taken out of the furnace is subjected to surface cleaning, coated with an insulating coating and dried and sintered, and then undergoes finishing, inspection, packaging, and warehousing to obtain a finished product of a high magnetic induction oriented silicon steel ultra-thin strip.

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