Method and device for transversely uniform cooling of hot-rolled low-carbon strip steel

Abstract

This invention provides a method for uniformly cooling hot-rolled low-carbon strip in the transverse direction, comprising the following steps: S1, the low-carbon strip passes through a laminar flow cooling section, reducing the strip temperature to the first-stage cooling temperature, while simultaneously reducing the temperature difference between the middle and edge of the strip to within 15°C; S2, the low-carbon strip passes through an air mist cooling section, reducing the strip temperature to the second-stage cooling temperature, while further reducing the temperature difference between the middle and edge of the strip to within 10°C; S3, the low-carbon strip passes through a water replenishment cooling section, where cooling water is sprayed out in the form of a spray jet, reducing the strip temperature to a suitable coiling temperature before being fed into a coiler for coiling. This invention also provides a cooling device based on the method for uniformly cooling hot-rolled low-carbon strip in the transverse direction. This invention eliminates the temperature difference between the middle and edge of the strip by controlling the cooling water flow rate, gradually reducing the transverse temperature difference and ultimately achieving homogenization, avoiding the occurrence of mixed crystal phenomena, and effectively improving the waviness defects caused by uneven strip microstructure.

Description

Technical Field

[0001] This invention relates to the field of strip cooling technology, and in particular to a method and apparatus for uniform transverse cooling of hot-rolled low-carbon strip. Background Technology

[0002] The coiling temperature of hot-rolled strip steel is one of the important process parameters affecting the properties of the finished strip steel. The final rolling temperature of hot-rolled strip steel of different specifications and grades is generally 800℃~900℃. To obtain good microstructure and properties, the coiling temperature of the strip steel must generally be controlled between 550~700℃. The purpose of laminar flow cooling is to control the temperature of the strip steel through the cooling process, thereby cooling the strip steel temperature from the final rolling temperature at the finishing mill exit to the required coiling temperature, thus obtaining a finished steel coil with excellent microstructure and properties.

[0003] The strip steel travels on the rolling mill rollers for approximately 10 seconds. Relying solely on natural cooling methods such as heat radiation and conduction from the strip to the rollers is insufficient to lower the strip temperature by 100–350°C within this short timeframe between the finishing mill stand and the coiler. Therefore, laminar flow cooling devices are installed above and below the conveyor rollers. Several laminar flow manifolds are installed on both sides of the finishing mill output rollers, forming a cooling zone tens to over 100 meters long to cool the upper surface of the strip steel. The entire cooling zone is divided into several cooling sections, each controlled by valves that spray water. The cooling rate of the strip steel is controlled by adjusting the water flow rate and the number of cooling sections activated. A large amount of cooling water comes into contact with the strip steel surface, forming a thin film-like physical layer. The strip steel transfers its temperature to the cooling water, thus lowering its overall temperature.

[0004] The microstructure of low-carbon steel consists of ferrite and pearlite, with the pearlite transformation temperature around 680–700℃. However, in traditional laminar flow cooling systems, the water supply manifold is installed on only one side of the laminar flow manifold, and the gooseneck tubes installed on the laminar flow manifold have the same aperture and spacing. This results in higher water pressure on the side closer to the water supply manifold and lower water pressure on the side farther away, causing inconsistent lateral water flow rates in the gooseneck tubes. Consequently, the transverse temperature of the strip is uneven and appears as bands, with local temperature differences reaching 50–80℃. This leads to different pearlite transformation temperatures and growth rates, resulting in mixed crystal phenomena. Consequently, the stamping performance of low-carbon steel varies significantly, affecting the stability of its mechanical properties and becoming a major problem that urgently needs to be solved.

[0005] Meanwhile, the transverse temperature distribution with temperature drop at the edges of hot-rolled strip causes tensile stress in the middle and compressive stress at the edges. This stress caused by the temperature drop during cooling leads to the strip's shape developing towards edge waviness. Analysis also reveals that under the same equipment conditions or transverse temperature distribution, a higher cooling rate results in higher internal stress in the strip; a wider strip width makes transverse temperature difference control more difficult and leads to more severe temperature unevenness.

[0006] During the strip cooling process, strain mainly originates from temperature and phase transformation. Temperature is the driving force behind phase transformation, and the phase transformation process releases heat, affecting the strip temperature. Uneven strain in different parts of the strip will generate stress. When the local compressive stress exceeds the critical buckling stress, strip defects such as waviness will appear. According to the waviness determination theory, strip waviness defects are the external manifestation of internal stress: if the strip stress state is edge compressive stress and center tensile stress, the strip shape is edge waviness or has an edge waviness tendency; if it is edge tensile stress and center compressive stress, the strip shape is center waviness or has a center waviness tendency. Regardless of whether it is center waviness or edge waviness, it has a significant impact on processes such as tube making and cold rolling, resulting in reduced yield, or even downgrading or scrapping.

[0007] Currently, one approach to solving the above problems is to improve the uniformity of transverse cooling of the strip. For example, Chinese patent CN201220547168.0 discloses a laminar flow cooling edge shielding device. During production, water collection tanks on both sides shield the water curtain of the laminar flow manifold at the edge, reducing the range of laminar flow cooling at the edge. Simultaneously, the temperature of the strip cross-section is fed back to the control program by a temperature detection instrument during winding. The control program compares the actual temperature value of the strip cross-section with the set temperature value. If the difference exceeds the set range, the control program controls the hydraulic cylinder to move slightly, adjusting the opening of the edge shielding device until it is adjusted to within the set range. By adjusting the spray area of ​​cooling water in the width direction of the strip, the uneven cooling distribution in the width direction of the strip by the laminar flow cooling system is solved, reducing the temperature drop at the edge of the strip and reducing the temperature difference in the strip cross-section. However, when the automatic control of this device malfunctions or when prototyping new products, a manual program needs to be executed. The manual program involves manually setting the opening degree of the edge shielding device in the control program screen to adjust the temperature accuracy of the strip in the transverse direction, which is time-consuming and labor-intensive. Chinese patent CN201010282943.X discloses an equivalent laminar flow cooling method, and Chinese patent CN201510713274.X discloses a laminar flow cooling system and method for controlling bilateral waves in hot-rolled strip, which uses the technology of controlling the cooling effect in the width direction by changing the outlet diameter. These two patents respectively make the outlet diameter vary sinusoidally or linearly from the center to both sides, so that the water flow density gradually decreases from the center to both sides, and the cooling intensity gradually decreases from the center to both sides. The edges undergo secondary cooling to achieve the same cooling intensity as the center, thus maintaining a consistent temperature in the width direction of the strip. Considering that in actual production, the use of non-standard pipe diameters will increase production costs and processing difficulty. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, this invention provides a method and apparatus for uniform transverse cooling of hot-rolled low-carbon strip steel.

[0009] The technical solution adopted by this invention to solve its technical problem is:

[0010] A method for uniform transverse cooling of hot-rolled low-carbon strip steel includes the following steps:

[0011] S1. After hot rolling, the low carbon strip passes through the laminar flow cooling section. A three-stage laminar flow cooling mechanism is set up in the laminar flow cooling section. The cooling water flow rate of the gooseneck tube in each stage of the laminar flow cooling mechanism is adjusted according to the actual temperature distribution in the transverse direction of the strip to reduce the temperature of the strip to the first-stage cooling temperature, while reducing the temperature difference between the middle and the edge of the strip to within 15℃.

[0012] S2. Low carbon strip passes through the air mist cooling section, where cooling water is sprayed out in the form of high-pressure mist to fully contact and cool the surface of the strip. The temperature of the strip drops to the second-stage cooling temperature, and at the same time, the temperature difference between the middle and the edge of the strip is further reduced to within 10°C.

[0013] S3. The low-carbon strip passes through the water cooling section, where cooling water is sprayed out in the form of a spray to reduce the strip temperature to a suitable coiling temperature before it is sent to the coiler for coiling.

[0014] The cooling method is applicable to post-rolling cooling of cold-rolled base materials and ordinary carbon structural steel; the applicable billet composition is: C < 0.08%, Mn: 0.15%~0.30%, S < 0.025%, P < 0.025%, Si < 0.05%, Als < 0.055%, Ti < 0.025%, with the balance being Fe and unavoidable impurities.

[0015] The low-carbon strip steel has a rolling thickness of 2.75mm to 13.75mm, a rolling width of 920mm to 1035mm, and a rolling speed of 3m / s to 11m / s.

[0016] In step S1, the first cooling temperature is the ferrite transformation termination temperature; in step S2, when the subsequent coiling temperature of the strip is below 670°C, the second cooling temperature is selected as 670°C; when the subsequent coiling temperature of the strip is above 670°C, the second cooling temperature is selected as the temperature at which AlN is completely precipitated in the strip matrix.

[0017] A further improvement of the present invention is that the difference between the post-rolling temperature and the ferrite transformation termination temperature of the low-carbon strip is ΔT; within the laminar cooling section, the target temperature reduction of the first-stage laminar cooling mechanism is 35%ΔT to 45%ΔT, the target temperature reduction of the second-stage laminar cooling mechanism is 30%ΔT to 40%ΔT, and the target temperature reduction of the third-stage laminar cooling mechanism is 20%ΔT to 30%ΔT, and the target cooling temperature of each stage of the laminar cooling mechanism is determined according to the target temperature reduction.

[0018] A further improvement of the present invention is that: the flow rate of each gooseneck tube is controlled by an independently installed electric valve, and the formula for calculating the cooling water flow rate of the gooseneck tube is:

[0019]

[0020] In the formula, Q is the flow rate through the gooseneck tube (m³). 3 / h;

[0021] H – Strip thickness (mm);

[0022] v — Rolling speed, m / s;

[0023] Φ—Diameter of the gooseneck tube, mm;

[0024] ρ s —Strip density, kg / m 3

[0025] C S —Specific heat capacity of strip steel, KJ / kg·℃;

[0026] DT—Strip temperature drop DT, °C; DT = Strip temperature before cooling T0 - Target cooling temperature T1;

[0027] ρ w —Density of water, kg / m³ 3 ;

[0028] C W —Specific heat capacity of water, kJ / kg·℃;

[0029] △T — Temperature rise of water, °C;

[0030] n – Number of goose neck tubes.

[0031] In step S2, five sets of aerosol cooling mechanisms are arranged sequentially in the aerosol cooling section. Each set of aerosol cooling mechanisms is equipped with several aerosol nozzles. The aerosol nozzles are arranged in an array, and their width covers the transverse width of the strip steel. The aerosol nozzles located in the middle are all open, while the aerosol nozzles located at both ends are open in alternate rows, and the aerosol nozzles in adjacent rows are staggered.

[0032] A cooling device based on a transverse uniform cooling method for hot-rolled low-carbon strip steel includes a laminar flow cooling section, an air mist cooling section, and a water replenishment cooling section arranged sequentially between the finishing mill and the coiler; the laminar flow cooling section includes a first-stage laminar flow cooling mechanism, a second-stage laminar flow cooling mechanism, and a third-stage laminar flow cooling mechanism arranged sequentially, and an infrared imager for real-time monitoring of the transverse temperature of the strip steel is installed upstream of each stage of the laminar flow cooling mechanism.

[0033] A further improvement of the present invention is that the laminar flow cooling mechanism includes four rows of cooling manifolds arranged side by side, one end of the cooling manifolds is connected to a cooling water supply pipe, and the other end is connected to two rows of gooseneck pipes. The gooseneck pipes are evenly distributed along the width direction of the low carbon strip, and the gooseneck pipes in adjacent rows are staggered.

[0034] A further improvement of the present invention is that: five sets of aerosol cooling mechanisms are provided in the aerosol cooling section, each set of aerosol cooling mechanisms is provided with a number of aerosol nozzles, the aerosol nozzles are arranged in an array, and their width covers the transverse width of the strip steel; the aerosol nozzles are connected to the cooling water supply pipe through the aerosol manifold, and a high-pressure pump is installed on the aerosol manifold.

[0035] The beneficial effects of this invention are:

[0036] This invention discloses a transverse uniform cooling method and device for hot-rolled low-carbon strip steel. It improves upon the shortcomings of existing laminar flow cooling methods by controlling the cooling water flow rate to eliminate the temperature difference between the middle and edges of the strip, gradually reducing the transverse temperature difference and ultimately achieving homogenization. This effectively improves the waviness defects caused by uneven strip microstructure. Based on the phase transformation characteristics of low-carbon steel, progressive cooling is achieved through a sequentially arranged laminar flow cooling section, an air mist cooling section, and a water replenishment cooling section. The laminar flow cooling section facilitates the transformation of austenite to ferrite in the strip steel; the air mist cooling section facilitates the transformation of ferrite to pearlite; and the water replenishment cooling section lowers the strip temperature to the optimal temperature for coiling. This effectively improves the uniformity of the strip microstructure, avoids mixed crystal phenomena, and enhances the mechanical properties of the strip steel.

[0037] This invention requires no changes to the manifold system. Based on the existing laminar flow cooling device, it only requires precise adjustment of the gooseneck tube flow rate in each unit of each cooling stage according to the final rolling temperature, cooling set temperature, and coiling temperature, and based on the distribution of the transverse temperature difference of the strip. This achieves effective temperature control in the middle and edge of the strip. This invention requires no major modifications to the equipment, has low modification costs, and is suitable for industrial use and widespread adoption.

[0038] This invention features a three-stage laminar flow cooling system within its laminar flow cooling section. Each stage is equipped with an infrared imager to monitor the transverse temperature distribution of the strip at different target temperature points in real time. The flow rate of the gooseneck cooling water for each cooling stage is calculated using a formula, allowing for precise control of the transverse temperature of each strip segment. Furthermore, the staggered distribution of the gooseneck tubes in the laminar flow cooling system effectively prevents a strip-like temperature distribution in the transverse direction, improving the uniformity of the transverse temperature, reducing transverse temperature differences, minimizing stress abrupt changes caused by these differences, and improving the strip's waviness. During the laminar flow cooling process, the preset temperature for each stage is a stepped temperature specifically designed based on the phase transformation temperature of different low-carbon steels. This effectively ensures the stable and gradual cooling of the low-carbon steel, preventing excessive local stress that could lead to strip shape defects.

[0039] This invention incorporates an aerosol cooling section at the rear end of the laminar flow cooling process. Cooling water is sprayed out in a high-pressure aerosol form, ensuring full contact with the strip surface and resulting in uniform cooling across the entire strip surface. Simultaneously, the arrangement of fully open aerosol nozzles in the middle and alternately opened nozzles at both ends ensures that the cooling effect in the middle of the strip is greater than that at the edges, further reducing the temperature difference between the middle and edges and increasing the uniformity of the microstructure. Once the temperature difference is essentially eliminated, the strip enters the replenishment cooling section. In this section, a uniform volume of cooling water is used, and the middle and edges of the strip undergo simultaneous cooling to reach a suitable temperature for coiling. Attached Figure Description

[0040] Figure 1 This is a photograph of the edge morphology of the strip steel in Example 1;

[0041] Figure 2 Here is a metallographic photograph of the steel strip edge in Example 1;

[0042] Figure 3 This is a metallographic photograph of the middle section of the strip in Example 1;

[0043] Figure 4 A photograph showing the edge morphology of the strip in Comparative Example 1;

[0044] Figure 5 Here is a metallographic photograph of the edge of the strip in Comparative Example 1;

[0045] Figure 6 A metallographic photograph of the middle section of the strip in Comparative Example 1;

[0046] Figure 7 This is an overall schematic diagram of the cooling device of the present invention;

[0047] Figure 8 This is a schematic diagram of the gooseneck tube arrangement in a laminar flow cooling system;

[0048] Figure 9 This is a schematic diagram of the arrangement of the aerosol nozzles in the aerosol cooling mechanism;

[0049] In the diagram, 1. Finishing mill, 2. Strip steel, 3. Laminar flow roller conveyor, 4. First infrared imager, 5. First-stage laminar flow cooling mechanism, 6. Second infrared imager, 7. Second-stage laminar flow cooling mechanism, 8. Third infrared imager, 9. Third-stage laminar flow cooling mechanism, 10. Fourth infrared imager, 11. Cooling manifold, 12. Gooseneck tube, 13. Aerosol cooling mechanism, 14. Aerosol manifold, 15. Aerosol nozzle, 16. High-pressure pump, 17. Fifth infrared imager, 18. Water replenishment cooling mechanism, 19. Sixth infrared imager, 20. Coiler. Detailed Implementation

[0050] The present invention will be further described below.

[0051] A transverse uniform cooling method for hot-rolled low-carbon strip steel employs a stepped cooling approach to control the degree and rate of phase transformation within the strip steel, enabling orderly transformation of the internal crystalline phases. Simultaneously, during the austenite-to-ferrite transformation process, the cooling water flow rate is adjusted based on the actual temperatures of the middle and edges of the strip steel to minimize the temperature difference between the middle and edges, reduce the stress difference between the middle and edges, improve the strip shape, and ensure that the middle and edges undergo synchronous and uniform phase transformation during subsequent cooling phase transformation, resulting in a uniform crystalline structure.

[0052] The method for uniform transverse cooling of hot-rolled low-carbon strip steel includes the following steps:

[0053] S1. After hot rolling, the low carbon strip passes through the laminar flow cooling section. Based on the monitored transverse temperature distribution of the strip, the cooling water flow rate of the gooseneck tube is adjusted to make the strip cool uniformly in the transverse direction, reduce the strip temperature to the first-stage cooling temperature, and at the same time reduce the temperature difference between the middle and the edge of the strip to within 15℃.

[0054] S2. Low carbon strip passes through the air mist cooling section, where cooling water is sprayed out in the form of high-pressure mist to fully contact and cool the surface of the strip. The temperature of the strip drops to the second-stage cooling temperature, and at the same time, the temperature difference between the middle and the edge of the strip is reduced to less than 10°C.

[0055] S3. The low-carbon strip passes through the water cooling section, where cooling water is sprayed out in the form of a spray to reduce the strip temperature to a suitable coiling temperature before it is sent to the coiler for coiling.

[0056] The cooling method of this invention is applicable to cold-rolled base materials and ordinary carbon structural steel. The applicable billet composition is: C < 0.08%, Mn: 0.15%~0.30%, S < 0.025%, P < 0.025%, Si < 0.05%, Als < 0.055%, Ti < 0.025%, with the balance being Fe and unavoidable impurities (e.g., Cr, Cu, Ni, B, As).

[0057] The cooling method of the present invention is applicable to strip rolling thicknesses ranging from 2.75 mm to 13.75 mm, rolling widths ranging from 920 mm to 1035 mm, and rolling speeds ranging from 3 m / s to 11 m / s.

[0058] Based on the above-mentioned limitations on strip composition, strip size, and strip rolling speed, the phased cooling effect of the method of the present invention can be ensured.

[0059] In this invention, the first-stage cooling temperature, the second-stage cooling temperature, and the appropriate winding temperature are all related to the specific composition and type of low-carbon strip steel, and are determined according to the specific composition of the strip steel.

[0060] In step S1

[0061] In this step, the strip temperature is reduced from the post-rolling temperature to the first-stage cooling temperature, which is the ferrite transformation termination temperature and is determined by the type and specific composition of the strip. This step achieves a complete transformation from austenite to ferrite.

[0062] The laminar flow cooling section comprises three sequentially arranged laminar flow cooling mechanisms. The target temperature for each stage of the laminar flow cooling mechanism is determined based on the difference ΔT between the post-rolling temperature and the ferrite transformation termination temperature of the low-carbon strip, ensuring controllable cooling of the strip. The target temperatures of the laminar flow cooling mechanisms decrease progressively. Typically, the target temperature reduction for the first stage is 35% ΔT to 45% ΔT, for the second stage it is 30% ΔT to 40% ΔT, and for the third stage it is 20% ΔT to 30% ΔT. Based on these target temperature reductions, the target temperature for each stage of the laminar flow cooling mechanism can be determined.

[0063] Depending on the composition of the low-carbon strip steel, the hot rolling temperature and the ferrite transformation termination temperature vary, therefore the target temperature for each stage of the laminar flow cooling mechanism also differs. Low-carbon steel grades rolled in a rolling mill mainly include cold-rolled base materials represented by SPHC, ordinary carbon steel series represented by Q235B, and high-grade carbon steel represented by 20 steel. The target temperature settings for ordinary carbon steel, high-grade carbon steel, and cold-rolled base materials are typically shown in the table below.

[0064] Final rolling temperature 860±15℃ 900±15℃ First-stage laminar flow cooling target temperature 810℃ 820℃ Second-stage laminar flow cooling target temperature 760℃ 760℃ Ferrite transformation termination temperature 720℃ 720℃

[0065] In actual cooling, the final rolling temperature and target cooling temperature can be adjusted adaptively according to the specific composition of the steel.

[0066] For both plain carbon steel and high-carbon steel, approximately 20°C of heat is dissipated through air cooling during the transport process from the rolling mill to the laminar cooling section. This means the initial cooling temperature for both is approximately 840°C. Setting the first-stage cooling temperature to 810°C within this 20°C transformation temperature range reduces the ferrite transformation amount to below 20%. The second-stage cooling temperature is set to 760°C, at which point the ferrite enters a rapid transformation process. Therefore, by adjusting the transverse temperature difference of the strip, the ferrite microstructure during the transformation process is further homogenized. The third-stage cooling temperature is set to 720°C, which is the near-complete transformation temperature of the ferrite. At this point, the transverse temperature difference of the strip is essentially eliminated, meaning the ferrite microstructure at this stage is very uniform. Compared to intensive cooling, this invention can effectively control the uniformity of the ferrite microstructure transformation and reduce grain fluctuations.

[0067] Compared to cold-rolled base materials, the final rolling temperature is higher, and there is a possibility of recrystallization. At this time, adjusting the transverse temperature difference of the strip not only helps to reduce the subsequent temperature difference, but also controls the uniformity of ferrite.

[0068] Specifically, each laminar flow cooling mechanism includes four rows of cooling manifolds arranged side-by-side. One end of each manifold is connected to a cooling water supply pipe, and the other end is connected to two rows of gooseneck tubes. The flow rate of each gooseneck tube is controlled by an independently installed electric valve. In this embodiment, each row has 28 gooseneck tubes, evenly distributed laterally along the width of the strip. Cooling water is sprayed out through the gooseneck tubes to cool the upper and lower surfaces of the low-carbon strip.

[0069] Because of the large temperature difference between the middle and edge of the strip, internal stress can occur, which in turn affects the strip shape. Therefore, this invention increases the cooling water flow rate in the middle of the strip and decreases the cooling water flow rate at the edge of the strip by controlling the cooling water flow rate of the gooseneck tube. This results in a larger temperature drop in the middle of the strip, which was originally at a higher temperature, and a smaller temperature drop in the edge of the strip, which was originally at a lower temperature, during the laminar flow cooling process. This reduces the temperature difference across the transverse width of the strip, minimizes the uneven strain caused by the transverse temperature distribution, and improves the strip shape.

[0070] The flow rate control of the cooling water in the gooseneck tubes is related to the required temperature difference for the strip corresponding to that gooseneck tube. The temperature difference is calculated as: pre-cooling temperature - target temperature for that stage of laminar flow cooling. The pre-cooling temperature is obtained by detecting an infrared imager located upstream of the laminar flow cooling mechanism. Multiple detection points are evenly arranged transversely along the strip width using the infrared imager. The number and location of these detection points correspond one-to-one with the arrangement of the gooseneck tubes, comprehensively detecting the transverse temperature distribution of the strip.

[0071] The formula for calculating the cooling water flow rate of the gooseneck tube is as follows:

[0072]

[0073] In the formula, Q is the flow rate through the gooseneck tube (m³). 3 / h;

[0074] H – Strip thickness (mm);

[0075] v — Rolling speed, m / s;

[0076] Φ—Diameter of the gooseneck tube, mm;

[0077] ρ s —Strip density, kg / m 3

[0078] C S —Specific heat capacity of strip steel, KJ / kg·℃;

[0079] DT—Strip temperature drop DT, °C; DT = Strip temperature before cooling T0 - Target cooling temperature T1;

[0080] ρ w —Density of water, kg / m³ 3 ;

[0081] C W —Specific heat capacity of water, kJ / kg·℃;

[0082] △T — Temperature rise of water, °C;

[0083] n – Number of goose neck tubes.

[0084] The target cooling temperatures for each stage are set in the control system, and the temperature detected by the infrared imager is also transmitted to the control system in real time. After receiving the temperature data and calculating the gooseneck flow rate, the control system transmits the control signal to the electric valve that controls the gooseneck. The control system provides feedback to the electric valve via a percentage, and the flow rate of the gooseneck is regulated by adjusting the opening of the electric valve.

[0085] Furthermore, the staggered arrangement of the adjacent rows of gooseneck tubes can effectively prevent the transverse temperature of the strip from being distributed in a strip-like pattern, thereby improving the uniformity of the transverse temperature.

[0086] In step S2

[0087] In this step, the strip temperature is reduced from the first-stage cooling temperature to the second-stage cooling temperature to achieve a uniform transformation from ferrite to pearlite.

[0088] When the subsequent coiling temperature of the strip is below 670℃, the second-stage cooling temperature is selected as 670℃; when the subsequent coiling temperature of the strip is above 670℃, the second-stage cooling temperature is selected as the temperature at which AlN is completely precipitated in the strip matrix.

[0089] The precipitation of AlN in steel can increase the hardness and strength of steel, improve its wear resistance, thermal conductivity, and oxidation resistance.

[0090] Specifically, five sets of aerosol cooling mechanisms are arranged sequentially in the aerosol cooling section. Each set of aerosol cooling mechanisms is equipped with several aerosol nozzles. The aerosol nozzles are arranged in an array, and their width covers the transverse width of the strip. In this invention, the array of aerosol nozzles is 3 rows × 20 nozzles, and the 20 nozzles are evenly arranged along the transverse direction of the strip.

[0091] The aerosol nozzle has an inner diameter of 0.5–0.8 mm and a spray pressure of 0.8–1.2 MPa. Cooling water is sprayed out at high speed in a mist form, uniformly contacting the upper and lower surfaces of the strip to achieve cooling. Within this cooling section, the strip undergoes a transformation from ferrite to pearlite. The more uniform aerosol cooling method further controls the temperature uniformity of the strip, allowing the microstructure to transform simultaneously and improving its uniformity.

[0092] To further eliminate the temperature difference between the middle and edges of the strip and improve the overall uniformity of the strip's crystalline structure, in the five sets of aerosol cooling mechanisms, all 10 aerosol nozzles in the middle are fully open, while the 5 aerosol nozzles at each end are open in alternating rows, with adjacent rows of open nozzles staggered. This arrangement ensures that the cooling water volume in the middle of the strip is higher than that at the edges, further eliminating the temperature difference between the middle and edges of the strip.

[0093] Downstream of the aerosol cooling mechanism, an infrared imager is also installed to detect the transverse temperature distribution of the strip steel, thereby detecting the distribution of the strip steel after aerosol cooling and providing data support for the amount of water replenished in the subsequent water replenishment cooling section.

[0094] The strip steel is cooled in an orderly manner through a laminar flow cooling stage and an infrared imager. In addition, all rolling parameters are given by the system, and the water temperature is monitored online. As long as the pyrometer is free from distortion, the uniformity of temperature cooling can be guaranteed. Even if there is a certain deviation in the laminar flow cooling temperature, the uneven transformation of ferrite can be completely avoided through the air mist cooling stage, and the strip steel temperature can be reduced to the second-stage cooling temperature.

[0095] In step S3

[0096] The water replenishment cooling section is equipped with multiple sets of water replenishment cooling mechanisms, which are similar in structure to laminar flow cooling mechanisms. Since the temperature difference between the middle and edge of the strip entering the water replenishment cooling section is controlled to 4℃~8℃, a uniform water volume is used for spray cooling. Each set of water replenishment cooling mechanisms is independently controlled to open and close, and can automatically replenish water row by row according to the strip temperature at the outlet of the aerosol cooling section and the coiling temperature, until the strip temperature is cooled to the coiling temperature.

[0097] The present invention will be further described in detail below through embodiments.

[0098] Example 1

[0099] The strip material is SPHC-1, with the following specific chemical composition: C: 0.05%, Mn: 0.19%, S: 0.018%, P: 0.017%, Si: 0.01%, Als: 0.033%, and the balance being Fe and unavoidable impurities (Cr, Cu, Ni, B, As). The rolling specification is 3.0mm*1010mm, and the rolling speed is 11m / s, which falls within the applicable scope of the cooling method of this invention.

[0100] Based on the material of the strip steel, its hot rolling final rolling temperature is 895℃, coiling temperature is 620℃, first-stage cooling temperature is 720℃, and second-stage cooling temperature is 670℃; the first-stage cooling target temperature of the laminar flow cooling section is 820℃, the second-stage cooling target temperature is 760℃, and the third-stage cooling target temperature is 720℃.

[0101] The cooling methods specifically include:

[0102] S1. The temperature of the hot-rolled low-carbon strip is 895℃, and the temperature difference between the surface and the interior of the strip is 50-80℃. It enters the laminar flow cooling section for cooling. During this period, the flow rate of each gooseneck tube is adjusted by detecting the temperature with an infrared imager.

[0103] After passing through the first-stage laminar flow cooling mechanism, the strip temperature is reduced to 820℃, and the temperature difference between the strip surface and the interior of the strip is reduced to 30-55℃.

[0104] After passing through the second-stage laminar flow cooling mechanism, the strip temperature is reduced to 760℃, and the temperature difference between the strip surface and the interior of the strip is reduced to 20-37℃.

[0105] After passing through the third-stage laminar flow cooling mechanism, the strip temperature is reduced to 720℃, allowing the strip to enter the temperature range of austenite to ferrite transformation, and the temperature difference between the strip surface and the interior of the strip is reduced to 10-15℃.

[0106] Through a three-stage laminar flow cooling mechanism, the temperature difference between the surface and interior of the strip steel is significantly reduced, achieving near-uniform temperature and reducing stress.

[0107] S2. The low-carbon strip passes through the air mist cooling section, where cooling water is sprayed out in the form of high-pressure mist to fully contact and cool the surface of the strip. The temperature of the strip drops to 670℃, which is the transition range from ferrite to pearlite. At this time, the temperature difference between the surface and the interior of the strip drops to 4℃~8℃.

[0108] S3. The low-carbon strip passes through the water cooling section, where cooling water is sprayed out in the form of a spray to reduce the temperature of the strip to 620°C before it is sent to the coiler for coiling.

[0109] like Figure 1 As shown, the strip steel obtained in this embodiment has smooth edges and no waviness defects. Metallographic analysis was performed on the strip steel from this embodiment; the metallographic images are shown below. Figure 2 (edge) Figure 3 As shown in the middle section, the crystal phase structure of the edge structure is basically the same as that of the middle structure, which proves that the phase transformation process of the edge structure and the middle structure is stable, the structure is uniform, and the grain size is only 0.5.

[0110] Comparative Example 1

[0111] In this comparative example, the strip material is SPHC-1, with the following specific chemical composition: C: 0.05%, Mn: 0.175%, S: 0.015%, P: 0.010%, Si: 0.015%, Als: 0.027%, and the balance being Fe and unavoidable impurities (Cr, Cu, Ni, B, As). The rolling specifications are 3.0mm*1010mm, the rolling speed is 11m / s, the hot rolling finishing temperature is 895℃, and the coiling temperature is 620℃.

[0112] After hot rolling, the strip is centrally cooled using a traditional laminar flow cooling system, with a target temperature of 620℃. The transverse temperature difference between the cooled strip and the coiled strip is controlled at 45℃~68℃.

[0113] like Figure 4 As shown, the strip obtained in this comparative example exhibits wavy defects at the edges, indicating poor flatness. Metallographic analysis was performed on the strip from this comparative example. Figure 5 (edge) Figure 6 As shown in the middle section, the crystal phase structures of the middle and edge structures are quite different; compared with the crystal phase structure of the middle structure, the crystal phase structure of the edge structure is significantly more compact, with varying degrees of mixed crystals and a grain size difference of 1.0 to 2.0 grades.

[0114] Example 2

[0115] The strip steel is made of Q235B, with the following specific chemical composition: C: 0.17%, Mn: 0.27%, S: 0.019%, P: 0.018%, Si: 0.09%, Als: 0.024%, and the balance being Fe and unavoidable impurities (Cr, Cu, Ni, B, As). The rolling specification is 3.0mm*920mm, and the rolling speed is 11m / s, which falls within the applicable scope of the cooling method of this invention.

[0116] Based on the material of the strip steel, its hot rolling final rolling temperature is 860℃, coiling temperature is 590℃, first-stage cooling temperature is 720℃, and second-stage cooling temperature is 670℃; the first-stage cooling target temperature of the laminar flow cooling section is 810℃, the second-stage cooling target temperature is 760℃, and the third-stage cooling target temperature is 720℃.

[0117] The cooling methods specifically include:

[0118] S1. The temperature of the hot-rolled low-carbon strip is 860℃, and the temperature difference between the surface and the interior of the strip is 40-60℃. It enters the laminar flow cooling section for cooling. During this period, the flow rate of each gooseneck tube is adjusted by detecting the temperature with an infrared imager.

[0119] After passing through the first-stage laminar flow cooling mechanism, the strip temperature is reduced to 810℃, and the temperature difference between the strip surface and the interior of the strip is reduced to 25-40℃.

[0120] After passing through the second-stage laminar flow cooling mechanism, the strip temperature is reduced to 760℃, and the temperature difference between the strip surface and the interior of the strip is reduced to 15-31℃.

[0121] After passing through the third-stage laminar flow cooling mechanism, the strip temperature is reduced to 720℃, allowing the strip to enter the temperature range of ferrite to pearlite transformation, and the temperature difference between the strip surface and the interior of the strip is reduced to 8-13℃.

[0122] Through a three-stage laminar flow cooling mechanism, the temperature difference between the surface and interior of the strip steel is significantly reduced, achieving near-uniform temperature and reducing stress.

[0123] S2. The low-carbon strip passes through the air mist cooling section, where cooling water is sprayed out in the form of high-pressure mist to fully contact and cool the surface of the strip. The temperature of the strip drops to 670℃, which is the transition range from ferrite to pearlite. At this time, the temperature difference between the surface and the interior of the strip drops to 5℃~8℃.

[0124] S3. The low-carbon strip passes through the water cooling section, where cooling water is sprayed out in the form of a spray to reduce the temperature of the strip to 590°C before it is sent to the coiler for coiling.

[0125] The strip obtained in this embodiment has a smooth edge without any waviness defects. Metallographic analysis of the strip in this embodiment showed that the crystal phase structure of the edge structure and the crystal phase structure of the middle structure are basically the same, proving that the phase transformation process of the edge structure and the middle structure are stable, the structure is uniform, and the grain size is only 0.5 grade.

[0126] Comparative Example 2

[0127] In this comparative example, the strip steel is Q235B, with the following chemical composition: C: 0.15%, Mn: 0.24%, S: 0.015%, P: 0.010%, Si: 0.10%, Als: 0.021%, and the balance being Fe and unavoidable impurities (Cr, Cu, Ni, B, As). The rolling specifications are 3.0mm*920mm, the rolling speed is 11m / s, the hot rolling finishing temperature is 860℃, and the coiling temperature is 590℃.

[0128] After hot rolling, the strip is centrally cooled using a traditional laminar flow cooling system, with a target temperature of 590℃. The transverse temperature difference between the cooled strip and the coiled strip is controlled at 41℃~62℃.

[0129] The strip obtained in this comparative example exhibits wavy defects at the edges, resulting in poor flatness. Metallographic analysis of the strip in this comparative example revealed that, compared to the crystal structure of the central part, the crystal structure of the edge part is significantly denser, exhibiting varying degrees of mixed crystals with a grain size difference of 1.5 to 2.5 grades.

[0130] Example 3

[0131] The strip steel is made of 20# steel, with the following specific chemical composition: C: 0.21%, Mn: 0.43%, S: 0.02%, P: 0.03%, Si: 0.23%, Als: 0.032%, and the balance being Fe and unavoidable impurities (Cr, Cu, Ni, B, As). The rolling specification is 4.5mm*920mm, and the rolling speed is 8m / s, which falls within the applicable scope of the cooling method of this invention.

[0132] Based on the material of the strip, its hot rolling final rolling temperature is 860℃, coiling temperature is 650℃, austenite transformation temperature is 840℃, first-stage cooling temperature is 720℃, and second-stage cooling temperature is 670℃; the first-stage cooling target temperature of the laminar flow cooling section is 810℃, the second-stage cooling target temperature is 760℃, and the third-stage cooling target temperature is 720℃.

[0133] The cooling methods specifically include:

[0134] S1. The temperature of the hot-rolled low-carbon strip is 860℃, and the temperature difference between the surface and the interior of the strip is 35-56℃. It enters the laminar flow cooling section for cooling. During this period, the flow rate of each gooseneck tube is adjusted by detecting the temperature with an infrared imager.

[0135] After passing through the first-stage laminar flow cooling mechanism, the strip temperature is reduced to 810℃, and the temperature difference between the strip surface and the interior of the strip is reduced to 27-37℃.

[0136] After passing through the second-stage laminar flow cooling mechanism, the strip temperature is reduced to 760℃, and the temperature difference between the strip surface and the interior of the strip is reduced to 10-28℃.

[0137] After passing through the third-stage laminar flow cooling mechanism, the strip temperature is reduced to 720℃, allowing the strip to enter the temperature range of ferrite to pearlite transformation, and the temperature difference between the strip surface and the interior of the strip is reduced to 5-11℃.

[0138] Through a three-stage laminar flow cooling mechanism, the temperature difference between the surface and interior of the strip steel is significantly reduced, achieving near-uniform temperature and reducing stress.

[0139] S2. The low-carbon strip passes through the air mist cooling section, where cooling water is sprayed out in the form of high-pressure mist to fully contact and cool the surface of the strip. The temperature of the strip drops to 670℃, which is the transition range from ferrite to pearlite. At this time, the temperature difference between the surface and the interior of the strip drops to 3℃~7℃.

[0140] S3. The low-carbon strip passes through the water cooling section, where cooling water is sprayed out in the form of a spray to reduce the temperature of the strip to 650°C before it is sent to the coiler for coiling.

[0141] The strip obtained in this embodiment has a smooth edge without any waviness defects. Metallographic analysis of the strip in this embodiment showed that the crystal phase structure of the edge structure and the crystal phase structure of the middle structure are basically the same, proving that the phase transformation process of the edge structure and the middle structure are stable, the structure is uniform, and the grain size is only 0.5 grade.

[0142] Comparative Example 3

[0143] In this comparative example, the strip steel is 20#, with the following specific chemical composition: C: 0.23%, Mn: 0.45%, S: 0.029%, P: 0.031%, Si: 0.24%, Als: 0.018%, and the balance being Fe and unavoidable impurities (Cr, Cu, Ni, B, As). The rolling specifications are 4.5mm*920mm, the rolling speed is 8m / s, the hot rolling finishing temperature is 860℃, and the coiling temperature is 650℃.

[0144] After hot rolling, the strip is centrally cooled using a traditional laminar flow cooling system, with a target temperature of 650℃. The transverse temperature difference between the cooled strip and the coiled strip is controlled at 37℃~54℃.

[0145] The strip obtained in this comparative example exhibits wavy defects at the edges, resulting in poor flatness. Metallographic analysis of the strip in this comparative example revealed that, compared to the crystal structure of the central part, the crystal structure of the edge part is significantly denser, exhibiting varying degrees of mixed crystals with a grain size difference of 1.5 to 3.0 grades.

[0146] The test results from the examples and comparative examples show that the cooling method of the present invention can significantly eliminate the temperature difference between the inside and outside of the strip, making the microstructure of the strip more uniform in the transverse width, effectively improving the waviness during the post-rolling cooling process, and resulting in a uniform metallographic structure of the strip.

[0147] The present invention also provides a transverse uniform cooling device for hot-rolled low-carbon strip steel, such as... Figure 7 As shown, the system includes a laminar flow cooling section, an air mist cooling section, and a water replenishment cooling section sequentially arranged between the finishing mill 1 and the coiler 20. The hot-rolled high-temperature low-carbon strip 2 is conveyed by rollers and passed through a cooling device. After being cooled by cooling water to a temperature suitable for coiling, it enters the coiler 20 for coiling.

[0148] The laminar flow cooling section includes a first-stage laminar flow cooling mechanism 5, a second-stage laminar flow cooling mechanism 7, and a third-stage laminar flow cooling mechanism 9 arranged sequentially. An infrared imager for real-time monitoring of the transverse temperature of the strip 2 is installed upstream of each laminar flow cooling mechanism. Specifically, a first infrared imager 4 is installed between the exit end of the finishing mill 1 and the first-stage laminar flow cooling mechanism 5; a second infrared imager 6 is installed between the first-stage laminar flow cooling mechanism 5 and the second-stage laminar flow cooling mechanism 7; and a third infrared imager 8 is installed between the second-stage laminar flow cooling mechanism 7 and the third-stage laminar flow cooling mechanism 9. In addition, a fourth infrared imager 10 is installed at the rear end of the third-stage laminar flow cooling mechanism 9.

[0149] The first-stage laminar flow cooling mechanism 5, the second-stage laminar flow cooling mechanism 7, and the third-stage laminar flow cooling mechanism 9 have the same structure, all including four rows of cooling manifolds 11 arranged side by side. One end of each cooling manifold 11 is connected to a cooling water supply pipe, and the other end is connected to two rows of gooseneck tubes 12. Each row contains n gooseneck tubes 12, which are evenly distributed along the width direction of the low-carbon strip steel 2, and the gooseneck tubes 12 in adjacent rows are staggered. See [reference needed]. Figure 8 Each gooseneck tube 12 is equipped with an adjustable electric valve and flow meter to achieve individual control of the cooling water flow. Cooling water is sprayed out through the gooseneck tube 12 to cool and lower the temperature of the low-carbon strip steel 2.

[0150] The flow rate of the gooseneck tube 12 is determined based on the difference between the actual temperature of the strip 2 detected by the infrared imager and the target cooling temperature. Therefore, to accurately detect the transverse temperature of the strip 2, the number of detection points of each infrared imager is the same as the number of gooseneck tubes 12 in its downstream laminar flow cooling mechanism. That is, each infrared imager is equipped with n temperature detection points. These n detection points are evenly distributed along the transverse direction of the strip 2 and correspond to the positions of the gooseneck tubes 12 in the laminar flow cooling mechanism. The number and position of the detection points correspond one-to-one with the arrangement of the gooseneck tubes 12, thus comprehensively detecting the transverse temperature distribution of the strip 2.

[0151] The number n of gooseneck tubes 12 is adjusted according to the width of the strip 2, typically 25 ≤ n ≤ 30. In this embodiment, n = 28, meaning each row of cooling manifolds 11 connects to two rows of gooseneck tubes 12, with 28 gooseneck tubes 12 per row, evenly distributed along the width of the strip 2. The diameter of the gooseneck tubes 12 is 20–23 mm, and the spacing between adjacent gooseneck tubes 12 is 43–45 mm. Correspondingly, each infrared imager has 28 temperature detection points, evenly distributed along the transverse direction of the strip 2, corresponding one-to-one with the positions of the 28 gooseneck tubes 12 in the laminar flow cooling mechanism.

[0152] The temperature detected by the infrared imager is transmitted to the control system in real time. After receiving the temperature data and calculating the flow rate of the gooseneck tube 12, the control system transmits the control signal to the electric valve controlling the gooseneck tube 12, and provides feedback to the electric valve via a percentage. The flow rate of the gooseneck tube 12 is adjusted by changing the opening degree of the electric valve.

[0153] The aerosol cooling section is equipped with five sets of aerosol cooling mechanisms 13, with a total length of 20-25m. Each set of aerosol cooling mechanisms 13 is equipped with several aerosol nozzles 15, which are arranged in an array, their width covering the transverse width of the strip steel 2, and adjacent rows of aerosol nozzles 15 are staggered. In this invention, the array of aerosol nozzles 15 in each set of aerosol cooling mechanisms 13 is 3 rows × 20 nozzles, with the 20 nozzles evenly arranged along the transverse direction of the strip steel 2, participating in... Figure 9 The aerosol nozzle 15 is connected to the cooling water supply pipe through the aerosol manifold 14. A high-pressure pump 16 is installed on the aerosol manifold 14. The high-pressure pump 16 pressurizes the cooling water to 0.8-1.2 MPa and then sprays it out through the aerosol nozzle 15.

[0154] In this embodiment, the nozzle length is 28–30 mm and the inner diameter is 0.5–0.8 mm. In actual use, adjustments can be made according to factors such as water pressure.

[0155] In order to further eliminate the temperature difference between the middle and the edge of the strip 2 and improve the uniformity of the overall crystal phase structure of the strip 2, in the five sets of aerosol cooling mechanisms 13, the 10 aerosol nozzles 15 located in the middle are all in a concentrated open state, and the 5 aerosol nozzles 15 located at each end are in an alternate row open state, and the aerosol nozzles 15 in adjacent rows are staggered, so that the cooling water flow rate in the middle of the strip 2 is greater than the cooling water flow rate at the edge of the strip 2.

[0156] Downstream of the aerosol cooling section, a fifth infrared imager 17 is installed to detect the transverse temperature distribution of the strip 2 after aerosol cooling.

[0157] The water replenishment cooling section includes four sequentially arranged water replenishment cooling mechanisms 18. The structure of the water replenishment cooling mechanism 18 is similar to that of the laminar flow cooling mechanism, but no electric valve is installed on the gooseneck tube 12, and the flow rate of the gooseneck tube 12 adopts a uniform water volume. Each water replenishment cooling mechanism 18 is independently controlled and can automatically replenish water row by row according to the strip steel 2 temperature at the outlet of the aerosol cooling section and the coiling temperature, until the strip steel 2 temperature is cooled to the coiling temperature.

[0158] A sixth infrared imager 19 is also installed downstream of the water replenishment and cooling section to detect the temperature of the strip 2 after water replenishment and cooling.

[0159] It should be emphasized that the laminar flow cooling mechanism, the aerosol cooling mechanism 13, and the water replenishment cooling mechanism 18 are all in two sets, symmetrically arranged above and below the strip 2. Due to the influence of gravity, the cooling water pressure of the cooling mechanism located below the strip 2 is usually higher than that of the cooling water above the strip 2, so as to achieve synchronous cooling of both the upper and lower sides of the strip 2.

[0160] In this embodiment, the cooling water pressure of the laminar flow cooling mechanism / aerosol cooling mechanism 13 / water replenishment cooling mechanism 18 located above the strip 2 is 4.6 kPa to 4.8 kPa, and the cooling water pressure of the laminar flow cooling mechanism / aerosol cooling mechanism 13 / water replenishment cooling mechanism 18 located below the strip 2 is approximately 5.2 kPa to 5.4 kPa, with a difference of not less than 0.6 kPa. The cooling water of the aerosol cooling mechanism 13 requires secondary pressurization.

[0161] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for transverse uniform cooling of hot-rolled low-carbon strip steel, characterized in that... Includes the following steps: S1. After hot rolling, the low carbon strip passes through the laminar flow cooling section. A three-stage laminar flow cooling mechanism is set up in the laminar flow cooling section. The cooling water flow rate of the gooseneck tube in each stage of the laminar flow cooling mechanism is adjusted according to the actual temperature distribution in the transverse direction of the strip to reduce the temperature of the strip to the first-stage cooling temperature, while reducing the temperature difference between the middle and the edge of the strip to within 15℃. S2. Low carbon strip passes through the air mist cooling section, where cooling water is sprayed out in the form of high-pressure mist to fully contact and cool the surface of the strip. The temperature of the strip drops to the second-stage cooling temperature, and at the same time, the temperature difference between the middle and the edge of the strip is further reduced to within 10°C. S3. The low-carbon strip passes through the water cooling section, where cooling water is sprayed out in the form of a spray to reduce the strip temperature to a suitable coiling temperature before it is sent to the coiler for coiling. In step S1, the first cooling temperature is the ferrite transformation termination temperature; in step S2, when the subsequent coiling temperature of the strip is below 670°C, the second cooling temperature is selected as 670°C; when the subsequent coiling temperature of the strip is above 670°C, the second cooling temperature is selected as the temperature at which AlN is completely precipitated in the strip matrix.

2. The transverse uniform cooling method for hot-rolled low-carbon strip steel according to claim 1, characterized in that: The cooling method is applicable to post-rolling cooling of cold-rolled base materials and ordinary carbon structural steel; the applicable billet composition is: C < 0.08%, Mn: 0.15%~0.30%, S < 0.025%, P < 0.025%, Si < 0.05%, Als < 0.055%, Ti < 0.025%, with the balance being Fe and unavoidable impurities.

3. The transverse uniform cooling method for hot-rolled low-carbon strip steel according to claim 2, characterized in that: The low-carbon strip steel has a rolling thickness of 2.75mm to 13.75mm, a rolling width of 920mm to 1035mm, and a rolling speed of 3m / s to 11m / s.

4. The transverse uniform cooling method for hot-rolled low-carbon strip steel according to claim 1, characterized in that: The difference between the post-rolling temperature and the ferrite transformation termination temperature of the low-carbon strip is ΔT; within the laminar cooling section, the target temperature reduction of the first-stage laminar cooling mechanism is 35%ΔT~45%ΔT, the target temperature reduction of the second-stage laminar cooling mechanism is 30%ΔT~40%ΔT, and the target temperature reduction of the third-stage laminar cooling mechanism is 20%ΔT~30%ΔT. The target cooling temperature of each stage of the laminar cooling mechanism is determined based on the target temperature reduction.

5. The transverse uniform cooling method for hot-rolled low-carbon strip steel according to claim 4, characterized in that: Each gooseneck tube has its flow rate controlled by an independently installed electric valve. The formula for calculating the cooling water flow rate of the gooseneck tube is as follows: In the formula, Q is the flow rate through the gooseneck tube (m³). 3 / h; H – Strip thickness (mm); v — Rolling speed, m / s; Φ—Diameter of the gooseneck tube, mm; ρ s —Strip density, kg / m 3 C S —Specific heat capacity of strip steel, KJ / (kg·℃); DT—Strip temperature drop DT, °C; DT = Strip temperature before cooling T0 - Target cooling temperature T1; ρ w —Density of water, kg / m³ 3 ; C W —Specific heat capacity of water, kJ / (kg·℃); △T — Temperature rise of water, °C; n – Number of goose neck tubes.

6. The transverse uniform cooling method for hot-rolled low-carbon strip steel according to claim 1, characterized in that: In step S2, five sets of aerosol cooling mechanisms are sequentially arranged in the aerosol cooling section. Each set of aerosol cooling mechanisms is equipped with several aerosol nozzles. The aerosol nozzles are arranged in an array, and their width covers the transverse width of the strip steel. The aerosol nozzles located in the middle are all open, while the aerosol nozzles located at both ends are open in alternating rows, and the aerosol nozzles in adjacent rows are staggered.

7. A cooling device based on the transverse uniform cooling method for hot-rolled low-carbon strip steel according to any one of claims 1 to 6, characterized in that: It includes a laminar flow cooling section, an air mist cooling section and a water replenishment cooling section arranged sequentially between the finishing mill (1) and the coiler (20); the laminar flow cooling section includes a first-stage laminar flow cooling mechanism (5), a second-stage laminar flow cooling mechanism (7) and a third-stage laminar flow cooling mechanism (9) arranged sequentially, and an infrared imager for real-time monitoring of the transverse temperature of the strip is set upstream of each stage of the laminar flow cooling mechanism.

8. The cooling device according to claim 7, characterized in that: The laminar flow cooling mechanism includes four rows of cooling manifolds (11) arranged side by side. One end of the cooling manifold (11) is connected to a cooling water supply pipe, and the other end is connected to two rows of gooseneck pipes (12). The gooseneck pipes (12) are evenly distributed along the width direction of the low carbon strip, and the gooseneck pipes (12) in adjacent rows are staggered.

9. The cooling device according to claim 7, characterized in that: The aerosol cooling section is provided with five sets of aerosol cooling mechanisms (13), each set of aerosol cooling mechanisms (13) is provided with several aerosol nozzles (15), the aerosol nozzles (15) are arranged in an array, and their width covers the transverse width of the strip steel (2); the aerosol nozzles (15) are connected to the cooling water supply pipe through the aerosol manifold (14), and a high-pressure pump (16) is installed on the aerosol manifold (14).

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