Method for improving shape of IF steel cold-rolled sheet

Abstract

The invention relates to a method for improving the shape of an IF steel cold-rolled sheet, and belongs to the technical field of steelmaking processes. The method comprises the steps that casting blanks are heated in a furnace, and gaps between the adjacent casting blanks are controlled; wherein the in-furnace heating comprises a preheating section, a first heating section, a second heating section and a soaking section; edge heating is conducted on the heated casting blank, and it is ensured that the target area of the casting blank rises to the set temperature; the casting blank with the edge heated is sequentially subjected to finish rolling and ultra-fast cooling, and a hot-rolled coil is obtained; step cooling is carried out on the working roll subjected to finish rolling; and the hot-rolled coil is subjected to cold rolling, and the cold-rolled sheet is obtained. By optimizing the hot rolling process and equipment, the edge structure of a hot-rolled coil is effectively improved, so that the plate shape defect of the IF steel cold-rolled plate is improved.

Description

Technical Field

[0001] The present application relates to the technical field of steelmaking technology, and in particular to a method for improving the shape of IF steel cold-rolled plates. Background Art

[0002] IF steel, the full name of which is interstitial-free steel, has been widely used in many fields such as automobile manufacturing, household appliances and construction due to its excellent deep drawing performance and excellent surface quality. Its unique microstructure and excellent mechanical properties enable IF steel to meet a series of high-strength, high-precision and high-corrosion resistance requirements. However, its plate shape control has always been a difficult point in the production process, which directly affects the yield and quality of the product. With the continuous improvement of the manufacturing industry's requirements for material performance, it is particularly urgent to explore and practice effective plate shape improvement methods.

[0003] IF steel cold-hardened coils generally have edge wave shape defects, which is a type of plate shape problem that is difficult to solve in the industry. The plate shape problem is mainly double-sided waves. After heat treatment, the degradation rate of the galvanized plate wave shape problem is as high as 5%, which cannot meet the use needs of high-end customers. In order to improve the shape defects of cold-rolled plates, the industry usually tries to adjust the cold rolling process parameters. Patent CN103801580A proposes to control the final rolling temperature to ensure that there is no mixed crystal and deformation structure at the edge, and the cold rolling trimming is 15-30mm to ensure the cold-rolled plate shape, but no specific measures to improve the edge structure are proposed; Patent CN114226453A solves the wave shape problem of ferrite rolling process by controlling the heating temperature, rolling temperature, rolling speed and reduction rate. This patent is for ferrite rolling process and has no reference significance for traditional austenite rolling process; Patent CN115415332A proposes high temperature furnace temperature and flattening after hot rolling to improve the shape problem of high-strength steel.

[0004] However, although these methods can alleviate the plate shape problem to a certain extent, they cannot fundamentally solve the wave-shaped defects after cold rolling caused by uneven hot rolling structure. During the hot rolling process, due to the influence of various factors such as rolling pressure, temperature control, and roll state, uneven internal stress and structural changes may occur inside the plate, which will be amplified during the cold rolling process, eventually leading to the generation of plate shape defects such as edge waves. Summary of the invention

[0005] The present application provides a method for improving the plate shape of an IF steel cold-rolled plate to solve the following technical problem: how to improve the edge wave shape defect of an IF steel cold-rolled plate through a hot rolling process.

[0006] The embodiment of the present application provides a method for improving the shape of an IF steel cold-rolled plate, the method comprising:

[0007] The ingots are heated in a furnace, and the gaps between adjacent ingots are controlled; wherein the in-furnace heating includes: a preheating section, a first heating section, a second heating section, and a soaking section;

[0008] The heated ingot is edge-heated to ensure that the target area of ​​the ingot is raised to a set temperature;

[0009] The cast billet after edge heating is sequentially subjected to finish rolling and ultra-rapid cooling to obtain a hot-rolled coil; wherein the work rolls for the finish rolling are subjected to step cooling;

[0010] The hot-rolled coil is cold-rolled to obtain a cold-rolled sheet.

[0011] Optionally, the temperature of the soaking section is 1170°C to 1190°C.

[0012] Optionally, the gap between adjacent ingots is 200 mm to 280 mm.

[0013] Optionally, the temperature of the soaking section is at least 20° C. higher than the temperature of the second heating section.

[0014] Optionally, the target area is within 80 mm from the edge.

[0015] Optionally, the set temperature is 50°C to 80°C.

[0016] Optionally, the edge rolls of the working rolls are areas within 200 mm from the edges of the working rolls, and through the step cooling, the temperature of the edge rolls is 15° C. to 20° C. lower than the temperature of the middle rolls of the working rolls.

[0017] Optionally, the reduction ratio of the finishing rolling stand F6 is 27% to 29%, and the reduction ratio of the finishing rolling stand F7 is 17% to 19%.

[0018] Optionally, the ultra-rapid cooling pressure is 0.45 MPa to 0.55 MPa.

[0019] Optionally, the cooling rate of the ultra-fast cooling is 70°C / s to 100°C / s.

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

[0021] The embodiment of the present application provides a method for improving the shape of IF steel cold-rolled plate, the method comprising: heating the ingot in a furnace and controlling the gap between adjacent ingots; wherein the in-furnace heating comprises: a preheating section, a first heating section, a second heating section and a soaking section; heating the heated ingot at the edge to ensure that the target area of ​​the ingot is raised to a set temperature; the ingot after edge heating is sequentially finished rolled and ultra-fast cooled to obtain a hot-rolled coil; wherein the finishing rolling work roll is step-cooled; the hot-rolled coil is cold-rolled to obtain a cold-rolled plate. By precisely controlling parameters such as temperature during furnace heating, the temperature of the ingot is uniform and the internal stress is reduced; secondly, edge heating can improve the heating uniformity of the edge of the strip, effectively reduce edge cracks and local deformation, and thus improve the plate shape quality; step cooling of the finishing rolling work roll can ensure the working stability of the roll and reduce the plate shape defects caused by the thermal deformation of the roll. In addition, the optimized configuration of the finishing rolling load can adjust the deformation distribution of each part of the strip to make it more uniform and reasonable, thereby effectively preventing the occurrence of various plate shape problems. Finally, the introduction of ultra-rapid cooling can significantly improve the cooling efficiency of the strip and ensure the uniformity of the strip structure during the rapid cooling process, which plays a significant role in improving the plate shape of IF steel cold-rolled sheet. 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 technical solutions in the embodiments of the present application or 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 the shape of IF steel cold-rolled sheet provided in an embodiment of the present application;

[0025] Figure 2 The edge structure of the hot-rolled coil provided as a comparative example of this application;

[0026] Figure 3 This is the edge structure of the hot-rolled coil provided in the embodiment 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. "Parts" such as parts by weight and parts by mass indicate the proportional relationship between the components. In the proportional relationship involved in this article, the parameters that need to be described by proportion should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, if the mass ratio of substance A, substance B and substance C is 1:2:3, then substance A, substance B and substance C should correspond to the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0030] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this article can be purchased from the market or prepared by existing methods.

[0031] Figure 1 A schematic flow chart of a method for improving the shape of IF steel cold-rolled plate provided in an embodiment of the present application.

[0032] like Figure 1 As shown, the embodiment of the present application provides a method for improving the shape of IF steel cold-rolled plate, the method comprising:

[0033] S1. Heating the ingots in a furnace and controlling the gaps between adjacent ingots; wherein the in-furnace heating includes: a preheating section, a first heating section, a second heating section and a soaking section;

[0034] First, the ingot is sent to the heating furnace for heating treatment. This process is divided into preheating section, heating section, heating section and soaking section. During the heating process, special attention is paid to controlling the gap between adjacent ingots to ensure uniformity and efficiency of heating.

[0035] In the embodiment of the present application, the chemical composition of the ingot includes, by mass fraction: C≤0.06%, Si≤0.03%, 0.05%≤Mn≤0.25%, P≤0.017%, S≤0.015%, 0.035%≤Ti≤0.07%, and matrix element Fe.

[0036] In interstitial-free steels, low carbon content is critical because it helps reduce interstitial atoms (such as carbon and nitrogen) in the steel, thereby improving the toughness and deep drawing properties of the steel. Silicon is usually used for deoxidation and as a solid solution strengthening element, but in IF steels, its content needs to be strictly controlled to maintain the purity and performance of the steel. Manganese is a common alloying element in steel and is used to increase the strength and hardness of the steel. It also helps with deoxidation and desulfurization. In IF steels, the manganese content needs to be properly balanced to ensure good deep drawing properties and strength. Although phosphorus can improve the strength of steel, too much phosphorus can cause increased cold brittleness of steel, so its content needs to be strictly controlled in IF steels. Sulfur is one of the main factors causing hot brittleness of steel, so its content needs to be strictly controlled in IF steels to ensure good weldability and mechanical properties. Titanium plays a vital role in interstitial-free steels. It can combine with carbon and nitrogen in steel to form stable compounds, thereby reducing the number of interstitial atoms and improving the toughness and deep drawing properties of steel.

[0037] Fe is a matrix element. The specific content / content range of Fe can be obtained by the upper and lower limit formula of the component, that is:

[0038] The sum of the percentages of the contents of each component in a composition should be equal to 100%, and the content ranges of several components should meet the following conditions: the upper limit value of a component + the lower limit value of other components ≤ 100; the lower limit value of a component + the upper limit value of other components ≥ 100.

[0039] In the embodiment of the present application, the ingot is heated through a preheating section, a first heating section, a second heating section and a soaking section, and then taken out of the furnace, and the furnace-out temperature is the soaking section temperature.

[0040] Starting from the time when the billet is put into the furnace, the preheating stage is the initial stage of the billet heating process and the basic link of the entire heating process. The main purpose is to slowly increase the temperature of the billet so that it can gradually adapt to the ambient temperature in the heating furnace, thereby reducing the thermal stress caused by the large temperature difference and preparing for the subsequent heating process. In the embodiment of the present application, the temperature of the preheating section is controlled at 680℃~790℃ to avoid changes in the organizational structure and degradation of mechanical properties caused by rapid heating.

[0041] Immediately following the preheating section is the heating section, at which time the billet has adapted to the ambient temperature in the furnace and can begin to speed up the heating rate. At this stage, the furnace temperature will gradually rise to a higher level to achieve the purpose of deep burning of the billet. In the embodiment of the present application, the heating section includes a heating section and a second heating section. After the billet enters the first heating section, the task of this stage is to continue to increase the temperature of the billet and ensure that the heating rate is moderate and uniform. The temperature of the first heating section is controlled at 1030°C to 1090°C. After entering the second heating section, the billet continues to be subjected to high temperature to complete the necessary phase change and grain growth process. The temperature of the second heating section is controlled at 1130°C to 1170°C.

[0042] The soaking stage is the last stage in the heating process of the billet and is also the key link to ensure the quality of the billet. In this stage, the furnace temperature needs to be accurately controlled so that the billet is fully and evenly heated under constant or slowly changing temperature conditions. The purpose of the soaking stage is to eliminate possible local overheating or overcooling, ensure that the temperature difference on the entire billet section is within an acceptable range, reduce the internal stress caused by the temperature difference, and thus ensure the stable performance and qualified quality of the product in the subsequent process.

[0043] In some embodiments, the temperature of the soaking section is 1170°C to 1190°C.

[0044] By optimizing the temperature of the soaking section, the deep drawing performance of IF steel is ensured on the one hand, and the lateral temperature difference of the low-temperature furnace rolling line is smaller on the other hand, which is conducive to the uniformity of the edge structure. For example, the temperature of the soaking section can be 1170℃, 1175℃, 1180℃, 1185℃, 1190℃, etc.

[0045] In some embodiments, the temperature of the soaking section is 20° C. or higher than the temperature of the second heating section.

[0046] This setting can ensure that the gas flow rate in the soaking section can be increased, and the heating capacity of the soaking section can be fully utilized to ensure the temperature of the surface and edge of the slab. For example, the temperature of the soaking section can be 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C higher than the temperature of the second heating section.

[0047] In some embodiments, the gap between adjacent casting billets is 200 mm to 280 mm.

[0048] Inside the heating furnace, the gap between adjacent billets has a significant impact on the overall heating effect. If the gap is too small, the billets may contact each other and produce extrusion, which hinders the effective conduction and convection of heat, and thus affects the uniformity of billet heating; while if the gap is too large, it may cause excessive consumption of heat in the heating furnace, reduce energy efficiency, and increase production costs. The embodiment of the present application sets the gap between adjacent billets to 200mm to 280mm. Exemplarily, the gap between adjacent billets can be 200mm, 220mm, 240mm, 260mm, 280mm, etc.

[0049] S2, heating the edges of the heated ingot to ensure that the target area of ​​the ingot is heated to a set temperature;

[0050] After heating is completed, additional heating is performed on specific target areas (usually the edges) of the ingot to raise its temperature to a set level. This step is intended to improve the heating uniformity of the edge of the strip, effectively reduce edge cracks and local deformation caused by uneven temperature, and thus improve the final plate quality.

[0051] Edge heating can effectively reduce the temperature difference between the edge and the center by applying an appropriate amount of heat to the edge of the billet, thereby reducing edge thinning, wave and other plate defects caused by the temperature difference. Edge heating of the heated billet aims to improve the temperature distribution of the billet through local heating, thereby affecting its shape and quality after rolling.

[0052] In some embodiments, the target area is within 80 mm from the edge.

[0053] In some embodiments, the set temperature is 50°C to 80°C.

[0054] In the embodiment of the present application, an edge heater is used for edge heating. The use of an edge heater can effectively solve the problem of low edge temperature of hot-rolled strip. By accurately setting the temperature and heating range of the edge heating, it can be ensured that the temperature of the edge and the center of the strip are consistent, thereby reducing plate defects such as edge wavy caused by temperature differences. The temperature within 80 mm of the edge is set 50°C to 80°C higher than the temperature in the middle. The purpose is to compensate for the temperature drop at the edge of the rolling line, ensure that the temperature of the edge is consistent with that of the middle, and thus improve the edge structure of the hot-rolled strip.

[0055] S3, sequentially performing finish rolling and ultra-rapid cooling on the cast billet after edge heating to obtain a hot-rolled coil; wherein the work rolls for the finish rolling are step-cooled;

[0056] In the finishing rolling stage, the cooling effect of the working roll plays a vital role in the strip shape quality. In order to achieve efficient and accurate strip shape control, the use of stepped cooling technology is an advanced and effective means. The core of this technology is to divide the surface of the working roll into multiple cooling zones along the axial or radial direction according to the different heat load requirements during the working process, and design and implement differentiated cooling intensities for each zone. In this way, it can ensure that the working roll maintains a uniform temperature distribution during the rolling process, effectively reduce the thermal deformation problem caused by heat concentration, and thus significantly improve the straightness and overall quality of the strip.

[0057] In some embodiments, the edge rolls of the working rolls are areas within 200 mm from the edges of the working rolls, and through the step cooling, the temperature of the edge rolls is 15° C. to 20° C. lower than the temperature of the middle rolls of the working rolls.

[0058] By increasing the temperature of the edge rollers, the deformation behavior of the rolled piece during rolling can be affected, which helps to reduce or eliminate edge thinning, wave and other plate defects, thereby improving the plate quality of the product. In the embodiment of the present application, the water flow rate of the three rows of nozzles on the edge of the working roll is adjusted to 40m 3 / h, the water flow rate of the nozzle in the middle of the working roll is 85m 3 / h, so that the temperature of the edge roll is 15℃~20℃ lower than the temperature of the middle roll of the working roll, and then the edge temperature of the strip is 20℃~25℃ lower than the middle temperature of the strip, and the temperature difference between the edge and the middle of the strip is increased by 4℃~5℃ compared with the general method. Exemplarily, the temperature of the edge roll can be 15℃, 16℃, 17℃, 18℃, 19℃, 20℃, etc. lower than the temperature of the middle roll of the working roll.

[0059] In some embodiments, the rolling reduction ratio of the finishing mill F6 is 27% to 29%, and the rolling reduction ratio of the finishing mill F7 is 17% to 19%.

[0060] In the finishing stage, by cleverly adjusting the load distribution and moving part of the load to the rear frame, the pressure reduction burden of the front frame can be effectively reduced, thereby reducing the internal stress caused by excessive pressure reduction. In addition, the rear frame has a large deformation resistance. Increasing the large pressure reduction rate can increase the forward and backward sliding of the strip, increase friction heat, and reduce the temperature drop in the center and edge of the strip. For example, the pressure reduction rate of frame F6 can be 27%, 27.4%, 27.8%, 28.2%, 28.6%, 29%, etc.; the pressure reduction rate of frame F7 can be 17%, 17.4%, 17.8%, 18.2%, 18.6%, 19%, etc.

[0061] Ultra-rapid cooling of hot-rolled coils is an advanced metal processing technology that aims to improve the microstructure, mechanical properties and surface quality of hot-rolled materials. In this process, a high-pressure cooling medium (such as water or oil) is sprayed onto the surface of the hot-rolled coil at high speed through a dedicated nozzle system, achieving rapid heat transfer in a very short time, thereby effectively controlling the grain size and residual stress distribution inside the material. In the embodiment of the present application, the hot-rolled coil is subjected to ultra-rapid cooling, and the strip is rapidly cooled after the phase change is completed. The grains at the edge are finer and more uniform, avoiding the wave-shaped defects caused by the difference in the edge structure after subsequent cold rolling.

[0062] In some embodiments, the ultra-rapid cooling pressure is 0.45 MPa to 0.55 MPa.

[0063] When the pressure of ultra-fast cooling is in the range of 0.45MPa to 0.55MPa, it can ensure that the cooling medium is sprayed onto the hot rolled coil at an appropriate speed and flow rate, thereby achieving a uniform cooling effect. If the pressure is too low, insufficient cooling may result, affecting the quality and performance of the product; while if the pressure is too high, energy consumption and equipment wear may increase. Exemplarily, the pressure of ultra-fast cooling can be 0.45MPa, 0.47MPa, 0.49MPa, 0.51MPa, 0.53MPa, 0.55MPa, etc.

[0064] In some embodiments, the ultra-fast cooling has a cooling rate of 70° C. / s to 100° C. / s.

[0065] If the cooling rate is too slow, the temperature gradient inside the hot-rolled coil may not be large enough, thus failing to achieve the desired cooling effect and grain refinement. On the contrary, if the cooling rate is too fast, although the temperature can be quickly lowered, it may also cause other problems, such as deformation or cracking caused by excessive thermal stress. Therefore, setting the cooling rate within the range of 70°C / s to 100°C / s can ensure that the hot-rolled coil can achieve rapid temperature reduction during the cooling process while avoiding the negative effects of excessive cooling. This speed range can not only meet the needs of grain refinement, but also ensure the quality and performance of the product. Exemplarily, the cooling rate for ultra-fast cooling can be 70°C / s, 75°C / s, 80°C / s, 85°C / s, 90°C / s, 95°C / s, 100°C / s, and the like.

[0066] S4, cold rolling the hot-rolled coil to obtain a cold-rolled sheet.

[0067] In summary, a series of comprehensive measures, such as optimizing the heating process parameters in the furnace, rationally using the edge heating technology to maintain uniform temperature at the edge of the strip, optimizing the cooling system of the rollers in the finishing rolling area to keep the rollers working stably, scientifically adjusting the load distribution of each frame of the finishing rolling mill, and enabling the ultra-fast cooling medium pressure mode, can significantly improve the overall plate quality level of IF steel cold-rolled plates. These strategies not only help to improve the market competitiveness of products and meet the needs of downstream users for high-quality products, but also effectively reduce energy consumption and cost input in the production process and improve production efficiency. Therefore, in future production practices, we should continue to explore and improve the application strategies of these advanced technologies in daily production, and actively promote them to a wider range of steel product production lines to promote the overall technological progress and industrial upgrading of my country's steel industry.

[0068] The present application is further described below in conjunction with specific examples. The experimental methods in the following examples where specific conditions are not specified are usually measured in accordance with national standards / industry standards; if there are no corresponding national standards / industry standards, they are measured in accordance with common international standards, conventional conditions or conditions recommended by the manufacturer.

[0069] A method for improving the shape of an IF steel cold-rolled plate provided in an embodiment of the present application comprises:

[0070] The ingots are heated in a furnace, and the gaps between adjacent ingots are controlled; wherein the in-furnace heating includes: a preheating section, a first heating section, a second heating section, and a soaking section;

[0071] The heated ingot is edge-heated to ensure that the target area of ​​the ingot is raised to a set temperature;

[0072] The cast billet after edge heating is sequentially subjected to finish rolling and ultra-rapid cooling to obtain a hot-rolled coil; wherein the work rolls for the finish rolling are subjected to step cooling;

[0073] The hot rolled coil is cold rolled to obtain a cold rolled sheet. Specific process parameters are shown in Table 1.

[0074] Table 1

[0075]

[0076] The cold rolled sheet shape degradation rates of the embodiments and comparative examples are shown in Table 3.

[0077] The cold-rolled plate shape degradation rate is an important indicator to measure the quality of cold-rolled plate shape. It refers to the proportion of product degradation caused by plate shape defects (such as wave, curvature, edge thinning, etc.) during the cold rolling production process. The calculation method is: degradation rate = (number of degraded products / total production quantity) × 100%.

[0078] It can be seen from Table 1 that the preparation process parameters of the embodiments are all within the required range of the present invention, and the plate shape defects of the cold-rolled sheet are well controlled.

[0079] Attached Figure 2-3 Detailed description:

[0080] Figure 2 The edge structure of the hot-rolled coil provided as a comparative example of this application; Figure 3 The edge structure of the hot rolled coil provided in the embodiment of the present application. Figure 2-3 It can be seen that the edge structure of the hot-rolled coil provided in the embodiment of the present application is more uniform, which can avoid the wave-shaped defects after cold rolling caused by the difference in edge structure.

[0081] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0082] The plate shape of the IF steel cold-rolled plate provided by the embodiment of the present invention is greatly improved, the plate surface is flatter and smoother, without obvious undulations, and is uniform in the entire width direction.

[0083] 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 the shape of IF steel cold-rolled sheet, the method comprising: The ingots are heated in a furnace, and the gaps between adjacent ingots are controlled; wherein the in-furnace heating includes: a preheating section, a first heating section, a second heating section, and a soaking section; The heated ingot is edge-heated to ensure that the target area of ​​the ingot is raised to a set temperature; The cast billet after edge heating is sequentially subjected to finish rolling and ultra-rapid cooling to obtain a hot-rolled coil; wherein the work rolls for the finish rolling are subjected to step cooling; The hot-rolled coil is cold-rolled to obtain a cold-rolled sheet.

2. The method according to claim 1, characterized in that The temperature of the soaking section is 1170°C to 1190°C.

3. The method according to claim 1, characterized in that The gap between adjacent ingots is 200 mm to 280 mm.

4. The method according to claim 1, characterized in that: The temperature of the soaking section is at least 20° C. higher than the temperature of the second heating section.

5. The method according to claim 1, characterized in that The target area is within 80 mm from the edge.

6. The method according to claim 1, characterized in that The set temperature is 50℃~80℃ The method according to claim 1 is characterized in that the edge rolls of the working rolls are areas within 200 mm from the edges of the working rolls, and through the step cooling, the temperature of the edge rolls is 15°C to 20°C lower than the temperature of the middle rolls of the working rolls.

7. The method according to claim 1, characterized in that The rolling reduction ratio of the finish rolling stand F6 is 27% to 29%, and the rolling reduction ratio of the finish rolling stand F7 is 17% to 19%.

8. The method according to claim 1, characterized in that The pressure of the ultra-fast cooling is 0.45 MPa to 0.55 MPa.

9. The method according to claim 1, characterized in that: The cooling rate of the ultra-fast cooling is 70°C / s to 100°C / s.

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