Method for improving hot-rolled hemming cracks of medium-temperature oriented silicon steel

Abstract

The invention relates to a method for improving hot-rolled hemming cracks of medium-temperature oriented silicon steel, and belongs to the technical field of steel rolling. The method comprises the following steps: obtaining a plate blank with set chemical components; the plate blank is heated, and then high-pressure water descaling is conducted; rough rolling is conducted on the plate blank subjected to high-pressure water descaling, and an intermediate blank is obtained; the intermediate billet is subjected to finish rolling, and a semi-finished hot-rolled coil is obtained; and the semi-finished hot-rolled coil is subjected to laminar cooling and then coiled, and the hot-rolled coil is obtained. According to the method, on the basis of the characteristics of a steel grade component system of the medium-temperature oriented silicon steel, on the basis of an existing hot rolling process, the hot-rolled medium-temperature oriented silicon steel is stably produced in batches by optimizing the in-furnace time of each section of a heating furnace, the width reduction amount of a rough rolling vertical roll, the reduction of a finish rolling vertical roll and other core control points, and the edge crack is controlled to be 3 mm or below.

Description

Technical Field

[0001] The present application relates to the technical field of steel rolling, and in particular to a method for improving hot-rolled edge cracking of medium-temperature oriented silicon steel. Background Art

[0002] Medium temperature oriented silicon steel is a silicon steel material with special magnetic properties. It is mainly used to make various transformer cores and stator cores of large generators. It is an important soft magnetic material that is indispensable in the power, electronics and military industries. Oriented silicon steel is known as the "crown jewel" of steel products and is the most difficult type of steel product to manufacture.

[0003] Shougang Co., Ltd. will start increasing production of CGO ordinary medium-temperature oriented silicon steel base material in 2022. It has now achieved stable supply capacity in four forms: hot-rolled coils, pickled coils, single-chilled coils, and decarburized annealed coils. Due to the continuous improvement in customers' requirements for the magnetic properties of this type of silicon steel, in order to ensure that the CuS inhibitor is fully dissolved, it is necessary to ensure that the high temperature of 1300°C is kept in the furnace for a long time (more than 250 minutes). However, long-term heating at high temperature will cause edge cracks on the edges of the hot-rolled coils. The depth of the edge cracks is serious and can reach more than 15mm, affecting the pickling and trimming operation and the improvement of the yield rate. Summary of the invention

[0004] The present application provides a method for improving edge cracking of medium temperature oriented silicon steel hot rolled coils, so as to solve the following technical problem: how to reduce the edge cracking phenomenon of medium temperature oriented silicon steel hot rolled coils.

[0005] The present application provides a method for improving hot-rolled edge cracking of medium-temperature oriented silicon steel, the method comprising:

[0006] A slab with a set chemical composition is obtained;

[0007] The slab is heated and then descaled with high pressure water;

[0008] Rough rolling the slab after high-pressure water descaling to obtain an intermediate slab;

[0009] Finish rolling the intermediate billet to obtain a semi-finished hot-rolled coil;

[0010] The semi-finished hot-rolled coil is subjected to laminar cooling and then coiled to obtain a hot-rolled coil.

[0011] Optionally, the set chemical composition of the slab includes, by mass fraction: C: 0.025% to 0.045%, Si: 3.05% to 3.25%, Cu: 0.48% to 0.52%, Mn: 0.18% to 0.25%, Als: 0.014% to 0.025%, wherein Als represents acid-soluble aluminum.

[0012] Optionally, the total time in the furnace for heating is ≥250 min, and the temperature out of the furnace after heating is ≥1290°C.

[0013] Optionally, the heating includes a preheating section, a first heating section, a second heating section and a soaking section, and the total time in the furnace of the first heating section, the second heating section and the soaking section is ≤180 min; the total time in the furnace of the second heating section and the soaking section is ≤120 min.

[0014] Optionally, the rough rolling adopts a 1+5 rolling mode or a 0+5 rolling mode, wherein the total width reduction of the E2 vertical rolling mill of the rough rolling is ≥80 mm.

[0015] Optionally, the rough rolling adopts a high-temperature and high-reduction rolling process, the reduction rate of the rough rolling is ≥80%, and the terminal temperature of the rough rolling is ≥1090°C.

[0016] Optionally, the vertical roller mill before the finishing mill of the finish rolling adopts a constant pressure control mode, and the rolling force of the vertical roller mill before the finishing mill is ≥200KN.

[0017] Optionally, the finishing rolling method is a method of combining head speed-limited rolling with speed-increasing rolling after a final rolling temperature instrument is loaded for 10 to 100 meters, and the final rolling temperature of the finishing rolling is 925° C. to 935° C.

[0018] Optionally, the laminar cooling adopts a rear-stage intensive cooling mode, and the coiling temperature is 500°C to 600°C.

[0019] Optionally, the thickness of the hot-rolled coil is 2.2 mm to 2.4 mm.

[0020] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0021] The present application provides a method for improving the edge cracking of hot-rolled coils of medium-temperature oriented silicon steel, the method comprising: obtaining a slab with a set chemical composition; heating the slab, and then descaling it with high-pressure water; rough rolling the slab after high-pressure water descaling to obtain an intermediate slab; finishing rolling the intermediate slab to obtain a semi-finished hot-rolled coil; laminar cooling the semi-finished hot-rolled coil, and then coiling it to obtain a hot-rolled coil. Based on the characteristics of the steel grade component system of medium-temperature oriented silicon steel, on the basis of the existing hot rolling process, by optimizing the furnace time of each section of the heating furnace, the slab is evenly heated during the heating process, and the internal structure of the slab is homogenized and refined. By optimizing the width reduction of the rough rolling vertical roll, the grains are made finer and more evenly distributed, and the plasticity and toughness of the edge are improved, which helps to reduce cracks caused by uneven organization. In the finishing rolling stage, by reasonably setting the reduction of the vertical roll, the edge of the rolled piece is subjected to more uniform compression deformation, further reducing the stress concentration and crack generation at the edge of the hot-rolled coil. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0024] Figure 1 A schematic flow chart of a method for improving hot-rolled edge cracking of medium-temperature oriented silicon steel according to some embodiments of the present application;

[0025] Figure 2 This is the edge morphology of the oriented silicon steel provided in Comparative Example 2 of the present application.

[0026] Figure 3 This is the edge morphology of the oriented silicon steel provided in Example 1 of the present application. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0028] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a rigid limitation on the scope of the present application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within the range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range; in addition, whenever a numerical range is indicated in this document, it is meant to include any cited numbers (fractions or integers) within the indicated range.

[0029] In this document, the terms including "including" and "including" mean "including but not limited to". Relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone; where A and B can be singular or plural. "At least one" means one or more, and "plurality" means two or more; "at least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items; for example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple. Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0030] Figure 1 A schematic flow chart of a method for improving hot-rolled edge cracking of medium-temperature oriented silicon steel provided in an embodiment of the present application;

[0031] like Figure 1 As shown, the embodiment of the present application provides a method for improving hot-rolled edge cracking of medium-temperature oriented silicon steel, comprising:

[0032] S1. Obtaining a slab with a set chemical composition;

[0033] In some embodiments, the set chemical composition of the slab includes, by mass fraction: C: 0.025% to 0.045%, Si: 3.05% to 3.25%, Cu: 0.48% to 0.52%, Mn: 0.18% to 0.25%, Als: 0.014% to 0.025%, wherein Als represents acid-soluble aluminum.

[0034] The positive effect of controlling the C content to 0.025% to 0.045% is that the appropriate amount of carbon content helps to form a Gaussian texture during the hot rolling process, which is the key to the high magnetic induction characteristics of oriented silicon steel. At the same time, controlling the carbon content can avoid the magnetic aging phenomenon caused by excessive carbon content, thereby maintaining the stability of the magnetic properties of silicon steel. In addition, the appropriate amount of carbon content can improve the plasticity and toughness of silicon steel, making it easier to deform and less likely to break during hot rolling, which helps to improve the stability of the hot rolling process and the yield rate of the product. Exemplarily, the C content can be 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, etc.

[0035] The positive effect of controlling the Si content to 3.05% to 3.25% is that this content range helps to improve the magnetic permeability of silicon steel and reduce iron loss. In addition, the appropriate amount of Si content can also improve the mechanical properties and processing properties of silicon steel, making it easier to process into the desired shape and size. Exemplarily, the Si content can be 3.05%, 3.1%, 3.15%, 3.2%, 3.25%, etc.

[0036] Positive effects of controlling the Cu content to 0.48% to 0.52%: In oriented silicon steel, Cu is mainly added as an inhibitor-forming element to control the size of the primary recrystallized grains, thereby promoting the occurrence of secondary recrystallization and improving the magnetic properties of silicon steel. For example, the Cu content can be 0.48%, 0.49%, 0.5%, 0.51%, 0.52%, etc.

[0037] The positive effect of controlling the Mn content to 0.18% to 0.25% is that Mn can combine with elements such as S in steel within this content range to form fine inhibitor particles such as MnS. These inhibitors can effectively inhibit the growth of primary recrystallized grains and promote the occurrence of secondary recrystallization during hot rolling and other processes, thereby optimizing the magnetic properties of silicon steel. In addition, an appropriate amount of Mn content can improve the thermoplasticity of silicon steel, make the hot rolling process more stable, and reduce the occurrence of defects such as cracks and broken bands. Exemplarily, the Mn content can be 0.18%, 0.22%, 0.23%, 0.24%, 0.25%, etc.

[0038] The positive effect of controlling the Als content to 0.014% to 0.025% is that Als is an important element for forming aluminum nitride (AlN) inhibitors. Aluminum nitride is the main inhibitor of high magnetic induction oriented silicon steel. It can effectively inhibit the growth of primary grains and promote secondary recrystallization, thereby improving the magnetic properties of silicon steel. Fluctuations in the Als content will directly affect the magnetic induction and iron loss properties of the finished silicon steel sheet. When the Als content is too low, a sufficient amount of aluminum nitride cannot be formed, resulting in insufficient inhibitor strength; and when the Als content is too high, the aluminum nitride particles may become coarser, which will also lead to a decrease in inhibitor strength. Exemplarily, the Als content can be 0.014%, 0.016%, 0.018%, 0.022%, 0.025%, etc.

[0039] S2, heating the slab, and then descaling it with high-pressure water;

[0040] In some embodiments, the total furnace time of the heating is ≥250 min, and the furnace exit temperature of the heating is ≥1290°C.

[0041] The total heating time in the furnace is ≥250min, and the heating outlet temperature is ≥1290℃, which are the key process points to ensure the performance of the finished medium-temperature oriented silicon steel products. Through this process control, inhibitors such as AlN and CuS in the steel billet are fully dissolved, ensuring that the magnetic properties of the finished products in the downstream process meet the requirements.

[0042] In some embodiments, the heating includes a preheating section, a first heating section, a second heating section and a soaking section, and the total time in the furnace for the first heating section, the second heating section and the soaking section is ≤180 min; the total time in the furnace for the second heating section and the soaking section is ≤120 min.

[0043] The heating process includes preheating section, first heating section, second heating section and soaking section. The preheating section can ensure that the slab reaches a certain preheating temperature before entering the main heating section to reduce thermal stress. The total furnace time of each heating section is strictly controlled. The total furnace time of the first heating section, the second heating section and the soaking section is ≤180min, and the total furnace time of the second heating section and the soaking section is ≤120min. This helps to achieve uniform heating of the slab and avoid local overheating or overcooling.

[0044] Before hot rolling, the slab needs to be heated to a temperature suitable for rolling in a heating furnace. During the heating process, the iron oxide scale (i.e., scale) on the surface of the slab will thicken, affecting the rolling quality and surface finish of the product. Therefore, descaling treatment is required after heating. In this application, a high-pressure water jet method is used to remove the iron oxide scale on the surface of the slab.

[0045] S3, rough rolling the slab after high-pressure water descaling to obtain an intermediate slab;

[0046] In some embodiments, the rough rolling adopts a 1+5 rolling mode or a 0+5 rolling mode, wherein the total width reduction of the E2 vertical rolling mill of the rough rolling is ≥80 mm.

[0047] The rough rolling adopts 1+5 rolling mode or 0+5 rolling mode, that is, the R1 rough rolling mill rolls 0 or 1 passes, and the R2 rough rolling mill rolls 5 passes.

[0048] The positive effects of controlling the total width reduction ≥ 80mm: the greater the width reduction, the greater the distribution of each rough rolling pass, the higher the extrusion deformation heat, and the stronger the edge structure repair ability; too small a width reduction will lead to the edge structure being unable to be repaired, the edge crack depth will increase during the rolling and calendering process, and the edge quality will deteriorate.

[0049] In some embodiments, the rough rolling adopts a high temperature and high reduction rolling process, the reduction rate of the rough rolling is ≥80%, and the terminal temperature of the rough rolling is ≥1090°C.

[0050] The positive effect of controlling the rough rolling reduction rate ≥ 80% is: the greater the rough rolling reduction rate, the greater the slab width, and the corresponding vertical roll load increases accordingly, which is a favorable factor for edge shaping.

[0051] The positive effect of controlling the end temperature of rough rolling ≥ 1090℃: The end temperature of rough rolling directly affects the parameter setting of the subsequent finishing process. When the end temperature of rough rolling is high, it can provide more temperature margin for finishing rolling, making the adjustment of finishing process parameters more flexible and accurate. In addition, the plasticity of metal materials is enhanced and the deformation resistance is reduced at high temperatures, making the rolling process smoother and reducing the energy consumption in the rolling process.

[0052] S4, finishing rolling the intermediate billet to obtain a semi-finished hot-rolled coil;

[0053] In some embodiments, the vertical roller mill before the finishing mill of the finish rolling adopts a constant pressure control mode, and the rolling force of the vertical roller mill before the finishing mill is ≥200KN.

[0054] The constant pressure control mode is a control method that keeps the rolling pressure constant during the rolling process. This control mode ensures that the pressure applied by the rollers to the workpiece remains constant throughout the rolling process. This can effectively reduce the stress concentration caused by uneven pressure at the edges of the workpiece, thereby reducing the risk of edge cracks. In addition, under constant pressure, the deformation behavior of the workpiece is more uniform and controllable. This helps to reduce the occurrence of cracks caused by excessive local deformation and improve the overall quality of the workpiece.

[0055] When implementing the constant pressure control mode, the rolling force needs to be set. If the rolling force is set too high, the rolled piece may be too thin or even broken, while if the rolling force is set too low, the expected rolling effect may not be achieved.

[0056] In some embodiments, the finishing rolling method is a method of combining head speed-limited rolling with speed-increasing rolling after a final rolling temperature instrument is loaded for 10 to 100 meters, and the final rolling temperature of the finishing rolling is 925° C. to 935° C.

[0057] Head speed-limited rolling is a speed-limiting measure taken at the head of the strip in the initial stage of strip rolling to ensure that the strip can smoothly pass through the various stands of the finishing mill and avoid floating, buckling and other problems caused by excessive speed. Specifically, the initial running speed of the strip on the output roller should not be too high, and low-speed strip threading is required. The purpose of this stage is to ensure that the head of the strip can smoothly enter the finishing mill, laying a good foundation for subsequent high-speed rolling.

[0058] The final rolling temperature is an extremely important parameter in the production of hot rolled strip steel, which directly affects the structural properties, mechanical properties and final quality of the strip steel. The final rolling temperature instrument (such as infrared thermometer, etc.) is used to monitor the temperature change of the strip steel in real time during the rolling process to ensure that the final rolling temperature is controlled within the allowable fluctuation range.

[0059] After the head of the strip is caught by the coiler and runs stably for a distance (such as 10 meters to 100 meters), in order to meet the requirements of the final rolling temperature and increase the output, the rolling mill and the coiler will increase the speed synchronously for high-speed rolling. This process is called speed-up rolling. Speed-up rolling can significantly increase the rolling speed of the strip and make the final rolling temperature of the strip more accurately controlled. At the same time, since the residence time of the tail of the strip in the air is shortened during the speed-up rolling process, the radiation heat loss and forced convection heat loss are reduced, which helps to eliminate the problem of temperature difference between the head and tail of the strip.

[0060] The positive effect of controlling the final rolling temperature of the finishing rolling to 925℃~935℃: Ensuring the final rolling temperature is a key process point to ensure the performance of the finished product. In the finishing rolling stage, strictly controlling the final rolling temperature can avoid the stress concentration on the edge due to too low temperature and cause cracks. Exemplarily, the final rolling temperature of the finishing rolling can be 925℃, 928℃, 930℃, 932℃, 935℃, etc.

[0061] S5, laminar cooling the semi-finished hot-rolled coil, and then coiling it to obtain a hot-rolled coil.

[0062] In some embodiments, the laminar cooling adopts a rear-stage intensive cooling mode, and the coiling temperature is 500°C to 600°C.

[0063] The rear-stage intensive cooling mode can ensure that the hot-rolled coil is evenly cooled when passing through the laminar cooling section by opening 4 upper and 4 lower cooling pipes in each group of cooling headers. This uniform cooling helps to reduce the temperature gradient inside and on the edges of the rolled piece, thereby avoiding the problem of thermal stress concentration and edge cracking caused by uneven temperature. In addition, compared with the front-stage or middle-stage cooling, the rear-stage intensive cooling can more effectively utilize the residual heat of the rolled piece on the output roller table for rapid cooling. This can not only improve cooling efficiency, but also reduce energy waste.

[0064] The beneficial effect of controlling the coiling temperature to 500℃~600℃: When coiling within this temperature range, the microstructure of silicon steel can be optimized, avoiding the coarse grain structure and carbide accumulation caused by too high or too low temperature. Coarse grain structure and carbide accumulation are one of the important factors leading to edge cracking, so optimizing the microstructure helps reduce the risk of edge cracking. In addition, slow cooling after coiling helps to reduce the residual stress inside silicon steel. Excessively high coiling temperature will cause greater internal stress during recrystallization and slow cooling, thereby increasing the possibility of edge cracking. The appropriate coiling temperature can reduce this internal stress, thereby reducing the occurrence of edge cracking. Exemplarily, the coiling temperature can be 500℃, 520℃, 550℃, 570℃, 600℃, etc.

[0065] In some embodiments, the hot rolled coil has a thickness of 2.2 mm to 2.4 mm.

[0066] Medium temperature oriented silicon steel is widely used in high-end fields such as transformers and motors. These fields have high requirements for the dimensional accuracy and performance of materials. By controlling the thickness of the hot rolled coil within the range of 2.2mm to 2.4mm, the special requirements of these high-end applications for material size and performance can be met. For example, the thickness of the hot rolled coil can be 2.2mm, 2.25mm, 2.3mm, 2.4mm, etc.

[0067] The present application is further described below in conjunction with specific examples. The experimental methods in the following examples that do not specify specific conditions are usually measured according to industry standards; if there are no corresponding industry standards, they are carried out according to common international standards, conventional conditions, or conditions recommended by the manufacturer.

[0068] The following is a detailed description of a method for improving hot-rolled edge cracking of medium-temperature oriented silicon steel provided by the present application in combination with embodiments, comparative examples and experimental data. The method comprises:

[0069] S11, obtaining a slab with a set chemical composition;

[0070] S21, heating the slab, and then descaling it with high-pressure water;

[0071] S31, rough rolling the slab after high-pressure water descaling to obtain an intermediate slab;

[0072] S41, finishing rolling the intermediate billet to obtain a semi-finished hot-rolled coil;

[0073] S51, laminar cooling the semi-finished hot-rolled coil, and then coiling it to obtain a hot-rolled coil. The process parameters of each embodiment and each comparative example are shown in Table 1.

[0074] Table 1 Process parameters for improving the edge cracking of hot-rolled medium-temperature oriented silicon steel

[0075]

[0076]

[0077] The edge quality of the oriented silicon steel obtained in the embodiment and the comparative example was evaluated, and the evaluation results are shown in Table 2.

[0078] Table 2 Evaluation results of edge quality of oriented silicon steel

[0079] Group Edge quality Magnetic properties Example 1 The edge is smooth and continuous, with slight burr chain and a depth of 1mm Magnetic induction 1.90T, iron loss 1.02W / Kg Example 2 The edge is smooth and continuous, with slight burr chain and a depth of 1mm Magnetic induction 1.89T, iron loss 1.00W / Kg Example 3 The edge is smooth and continuous, with slight burr chain and a depth of 1mm Magnetic induction 1.88T, iron loss 0.98W / Kg Comparative Example 1 There are intermittent cracks on the edge, with a depth of 4mm Magnetic induction 1.88T, iron loss 1.01W / Kg Comparative Example 2 There are intermittent cracks on the edge, with a depth of 10mm Magnetic induction 1.87T, iron loss 0.99W / Kg

[0080] It can be seen from the data in Table 1 that the process parameters of the embodiment are within the required range of the present invention, and the edge quality of the obtained oriented silicon steel is good, with edge cracks below 3 mm.

[0081] Attached Figure 2-3 Detailed description:

[0082] Figure 2 The edge morphology of the oriented silicon steel provided in Comparative Example 2 of the present application; Figure 2 As shown, the edge crack depth of the oriented silicon steel provided in the comparative example is serious.

[0083] Figure 3 This is the edge morphology of the oriented silicon steel provided in Example 1 of the present application; Figure 3 As shown, the edge cracking situation of the oriented silicon steel provided in the embodiment is effectively improved.

[0084] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0085] 1. Effectively reducing or eliminating cracks on the edges of hot-rolled coils can significantly improve the yield of oriented silicon steel and reduce the scrap rate, thereby improving the overall quality and market competitiveness of the product.

[0086] 2. Reducing the scrap rate and increasing the yield rate directly reduce the consumption of raw materials and energy, and also reduce the rework and repair costs due to quality problems. For manufacturing companies, this means reduced costs and increased profits.

[0087] The above is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. It will be apparent to those skilled in the art that various modifications to these embodiments are possible, and the general principles defined in the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown in the present application, but will conform to the widest scope consistent with the principles and novel features applied for by the present application.

Claims

1. A method for improving hot-rolled edge cracking of medium-temperature oriented silicon steel, characterized in that: The method comprises: A slab with a set chemical composition is obtained; The slab is heated and then descaled with high pressure water; Rough rolling the slab after high-pressure water descaling to obtain an intermediate slab; Finish rolling the intermediate billet to obtain a semi-finished hot-rolled coil; The semi-finished hot-rolled coil is subjected to laminar cooling and then coiled to obtain a hot-rolled coil.

2. The method according to claim 1, characterized in that In terms of mass fraction, the set chemical composition of the slab includes: C: 0.025% to 0.045%, Si: 3.05% to 3.25%, Cu: 0.48% to 0.52%, Mn: 0.18% to 0.25%, Als: 0.014% to 0.025%, wherein Als represents acid-soluble aluminum.

3. The method according to claim 1, characterized in that The total furnace time of the heating is ≥250min, and the furnace outlet temperature of the heating is ≥1290°C.

4. The method according to claim 1, characterized in that: The heating includes a preheating section, a first heating section, a second heating section and a soaking section. The total time in the furnace for the first heating section, the second heating section and the soaking section is ≤180 minutes; the total time in the furnace for the second heating section and the soaking section is ≤120 minutes.

5. The method according to claim 1, characterized in that The rough rolling adopts a 1+5 rolling mode or a 0+5 rolling mode, wherein the total width reduction of the E2 vertical roller mill of the rough rolling is ≥80mm.

6. The method according to claim 1, characterized in that The rough rolling adopts a high temperature and high reduction rolling process, the reduction rate of the rough rolling is ≥80%, and the terminal temperature of the rough rolling is ≥1090°C.

7. The method according to claim 1, characterized in that The vertical roller mill in front of the finishing mill of the finishing rolling adopts a constant pressure control mode, and the rolling force of the vertical roller mill in front of the finishing mill is ≥200KN.

8. The method according to claim 1, characterized in that The finishing rolling is a combination of speed-limited rolling at the head and speed-increasing rolling after the final rolling temperature instrument is loaded for 10 to 100 meters. The final rolling temperature of the finishing rolling is 925° C. to 935° C.

9. The method according to claim 1, characterized in that: The laminar cooling adopts a rear-stage intensive cooling mode, and the coiling temperature is 500°C to 600°C.

10. The method according to claim 1, characterized in that The thickness of the hot rolled coil is 2.2 mm to 2.4 mm.

Images