A control method for preventing bending of high-quality carbon steel

Abstract

The application discloses a control method for preventing high-quality carbon steel from being bent, and belongs to the technical field of steel smelting. The method comprises the following steps: adopting an ultrafast cooling process to regulate and control the cooling rate of the edge of a steel plate, and combining a hot straightening process to straighten the steel plate after cooling, so that a high-flatness high-quality carbon steel plate is obtained. In the application, for high-quality carbon steel plates with different thickness specifications, the cooling of the steel plate is uniform by controlling the ultrafast cooling opening cooling temperature, roller speed, total cooling water flow and the ratio of the water spraying amount of the upper surface to that of the lower surface, the temperature difference between the upper surface and the lower surface of the steel plate after the ultrafast cooling is effectively controlled, so that the plate surface after the ultrafast cooling is as flat as possible, then the hot straightening process is adopted, the whole steel plate is made more flat by controlling the hot straightening process parameters, the frequency of transverse bending and tortoise-back bending is effectively reduced by adopting the above combined process, and finally the high-flatness high-quality carbon steel plate is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel smelting, in particular to a control method for preventing bending of high-quality carbon steel. BACKGROUND

[0002] In the plate process of a special mill, a large number of plate bending occurs in the process of rolling high-quality carbon steel ≤40 mm, which greatly increases the cost of heavy straightening and heat treatment of the unit, and seriously affects the product quality. How to effectively reduce the bending frequency of steel plates ≤40 mm in thickness, especially the frequency of transverse bending and turtle back bending, is an urgent problem to be solved in the process of cooling and straightening after rolling of high-quality carbon steel.

[0003] In view of the above problems, it is necessary to provide a control method for preventing bending of high-quality carbon steel. SUMMARY

[0004] The purpose of the present application is to overcome the defects of the prior art and provide a control method for preventing bending of high-quality carbon steel.

[0005] The technical problem of the present application is solved by the following technical scheme.

[0006] The present application provides a control method for preventing bending of high-quality carbon steel, comprising: regulating the cooling rate of the edge of the steel plate by using ultrafast cooling process, and straightening the cooled steel plate by combining with the hot straightening process, to obtain high flatness high-quality carbon steel plate.

[0007] The present application has the following beneficial effects:

[0008] The present application provides a control method for preventing bending of high-quality carbon steel, comprising: regulating the cooling rate of the edge of the steel plate by using ultrafast cooling process, and straightening the cooled steel plate by combining with the hot straightening process, to obtain high flatness high-quality carbon steel plate. The above scheme, by regulating the cooling rate of the edge of the steel plate by using ultrafast cooling process, eliminates internal organizational stress, and straightens the cooled steel plate by combining with the hot straightening process, to straighten the steel plate from the outside. By using the above combined control method of ultrafast cooling + hot straightening, the frequency of transverse bending and turtle back bending of carbon steel during cooling is effectively reduced, and the purpose of reducing the bending rate of the steel plate is ultimately achieved. BRIEF DESCRIPTION OF DRAWINGS

[0009] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. Other related drawings can also be obtained by those skilled in the art without creative labor.

[0010] Figure 1 Schematic diagram of different density grids adopted from the edge to the center of the steel plate in the embodiment. DETAILED DESCRIPTION

[0011] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. If specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are adopted. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0012] A control method for preventing the bending of high-quality carbon steel provided by the embodiments of the present application will be described in detail below.

[0013] The embodiments of the present application provide a control method for preventing the bending of high-quality carbon steel, which comprises: regulating the cooling rate of the edge of the steel plate by using the ultrafast cooling process, and straightening the steel plate after cooling by using the hot straightening process, so as to obtain a high-flatness high-quality carbon steel plate.

[0014] In the process of rolling high-quality carbon steel (h≤40 mm) in the plate process of the special rolling mill, a large number of plate bending phenomena (mainly including transverse bending and tortoise-back bending) occur. The inventor has found through long-term practice that the different cooling rates of the edge are the main reason for the transverse bending and tortoise-back bending of the steel plate. Therefore, the inventor proposes that the cooling rate of the edge of the steel plate is first regulated by using the ultrafast cooling process to eliminate the organizational stress in the steel plate, so as to achieve the purpose of making the plate surface as flat as possible after the steel plate is cooled by the ultrafast cooling process. Then, the steel plate after cooling is straightened by using the hot straightening process, so as to achieve the purpose of straightening the steel plate from the outside and ensure the flatness of the straightened steel plate. As can be seen from the above, the embodiments of the present application adopt a combined control method, which effectively reduces the frequency of the occurrence of transverse bending and tortoise-back bending, and finally achieves the purpose of reducing the bending rate of the steel plate.

[0015] In an optional embodiment, the ultrafast cooling is realized by using an ultrafast cooling system, and the ultrafast cooling system comprises 24 groups of headers, wherein: groups 1-4 are gap headers, and groups 5-24 are high-density headers.

[0016] In an optional embodiment, regulating the cooling rate of the edge of the steel plate by using the ultrafast cooling process comprises: shielding the cooling water of the edge of the steel plate by using grids with different densities, so as to ensure that the cooling speed of the edge of the steel plate is the same as the cooling speed of the center of the steel plate, and for steel plates with different thicknesses, different cooling opening temperatures, roller speeds, roller accelerations, water outlet group numbers, water outlet amounts and water outlet ratios are adopted, so that the temperature difference between the upper and lower surfaces of the steel plate after the ultrafast cooling is effectively controlled.

[0017] The regulation of the cooling rate of the edge of the steel plate by the ultrafast cooling process mainly includes: controlling the cooling uniformity of the steel plate by controlling the opening cooling temperature, the roller speed, the total flow of the cooling water and the ratio of the water spraying amount of the upper and lower surfaces, and effectively controlling the temperature difference between the upper and lower surfaces of the steel plate after the ultrafast cooling, so as to achieve the purpose of making the plate surface as flat as possible after the steel plate is taken out of the ultrafast cooling.

[0018] In an optional embodiment, the shielding of the cooling water of the edge of the steel plate by the grids with different densities includes: the cooling water passing area of the grids from the edge to the center of the steel plate is 0.5m 2 / m 2 , 0.65m 2 / m 2 and 0.8m 2 / m 2 respectively, and the width of each group of grids is 100mm.

[0019] Because the temperature drop speed of the edge of the steel plate in contact with the air is fast, the temperature difference between the center and the edge is caused, and the residual stress caused by the uneven cooling between the center and the edge exists in the cooling process, the center is subjected to the compressive stress of the edge, the edge is subjected to the tensile stress of the center, and the cooling of the upper surface is greater than that of the lower surface, so that the upward warping is formed in the state of falling to the normal temperature. In order to ensure that the temperature of the edge of the steel plate meets the requirements, the cooling water of the edge of the steel plate is shielded by the grids with different densities, and the bending caused by the too fast cooling rate of the two edges of the steel plate is reduced. The edge closest to the plate is the densest grid, the cooling water passing area of the grid is 0.5m 2 / m 2 , the cooling water passing area of the grid in the transition area from the edge to the center is 0.65m 2 / m 2 , and the cooling water passing area of the grid closest to the center of the plate is 0.8m 2 / m 2 . The width of each group of grids is 100mm. By using the above grid setting, the cooling speed of the edge of the plate and the cooling speed of the center of the plate can be basically ensured to be the same, and the upward warping caused by the uneven cooling between the edge and the center of the upper surface is prevented.

[0020] In an optional embodiment, the straightening of the cooled steel plate by the hot straightening process includes: different opening straightening temperatures, press-down amounts, straightening forces, outer cooling water of the straightening roll, inclination values and straightening times are adopted for different thicknesses of the steel plate, so as to ensure the flatness of the straightened steel plate.

[0021] The straightening of the cooled steel plate by the hot straightening process mainly includes: the upward warping and the downward buckling of the steel plate after the head rolling need to be straightened by the straightening machine to make the whole steel plate flat. According to the steel plates with different thicknesses, the opening straightening temperature, the press-down amount, the straightening force, the outer cooling water of the straightening roll, the inclination value and the straightening times are controlled in the embodiments of the present application, so as to ensure the flatness of the straightened steel plate.

[0022] In an optional implementation, for steel plates with a thickness h ≤ 20 mm, the initial cooling temperature is controlled at 900℃-1000℃, the roller conveyor speed is 2.3-2.5 m / s, and the roller conveyor acceleration is 0.015±0.001 m / s². 2 The water volume is 70m 3 / h, the water ratio between the upper and lower surfaces of the steel plate is 0.4 and the water volume on the lower surface is 28m³. 3 / h, only open the two sets of high-density manifolds 7 and 8, with 7 open at the top and closed at the bottom, and the rapid cooling and reddening temperature is 800℃±50℃, while ensuring that the target temperature difference between the upper and lower surfaces is within the range of 30-40℃; after the steel plate is subjected to ultra-rapid cooling, control the straightening temperature to 850-925℃, keep the external cooling water of the straightening rollers constantly open, the reduction is 1.8mm, and the straightening force is 1500-2500KN. According to the principle that the exit roller gap is 1.4mm larger than the inlet, perform partial straightening on the head, and then perform full straightening again to ensure that the entire steel plate is straight and without bending.

[0023] In an optional implementation, for steel plates with a thickness of 20 < h ≤ 25 mm, the initial cooling temperature is controlled at 950℃-1000℃, the roller conveyor speed is 2.3-2.5 m / s, and the roller conveyor acceleration is 0.015 ± 0.001 m / s². 2 The water volume is 70m 3 / h, the water content on the upper and lower surfaces of the steel plate is 0.6-1.0, and the water content on the lower surface is 42-70m. 3 / h, only 8 sets of high-density manifolds are turned on, the rapid cooling and reddening temperature is 800℃±50℃, and the target temperature difference between the upper and lower surfaces is kept within the range of 20-30℃; after the steel plate is subjected to ultra-rapid cooling, the straightening temperature is controlled at 850-925℃, the external cooling water of the straightening rollers is always on, the reduction is 1.6mm, the straightening force is 2000-3000KN, and the exit roller gap is 1.2mm larger than the inlet. After local straightening of the head, a full straightening is performed to ensure that the entire steel plate is straight and without bending.

[0024] In an optional implementation, for steel plates with a thickness of 25 < h ≤ 30 mm, the initial cooling temperature is controlled at 950℃-1000℃, the roller conveyor speed is 2.0-2.3 m / s, and the roller conveyor acceleration is 0.012 ± 0.001 m / s². 2 The water volume is 70-80m 3 / h, the water ratio between the upper and lower surfaces of the steel plate is 0.6-1.0 and the water volume on the lower surface is 42-80m³. 3h, only open high-density header 8 group, out of fast cooling red temperature 800℃±50℃, while ensuring the upper and lower surface target temperature difference in the range of 20-30℃; after the steel plate out of ultra-fast cooling, control open straightening temperature is 850-925℃, straightening roll outer cooling water is always open, the reduction is 1.2mm, the straightening force is 2000-3000KN, according to the exit roll gap is 1.0mm larger than the entrance, the head is locally straightened, then the whole straightening is carried out, to ensure the whole steel plate is flat and straight.

[0025] In the optional embodiment, for the steel plate with thickness 30 2 , the water amount is 70-120m 3 / h, the water ratio of the upper and lower surfaces of the steel plate is 1.5-2.0 and the water amount of the lower surface is 105-240m 3 / h, open high-density header 5 and 8 two groups, wherein 5 opens up and closes down, the out of fast cooling red temperature is 800℃±50℃, while ensuring the upper and lower surface target temperature difference in the range of 10-20℃; after the steel plate out of ultra-fast cooling, control open straightening temperature is 850-925℃, straightening roll outer cooling water is always open, the reduction is 0.8mm, the straightening force is 2000-3000KN, according to the exit roll gap is 0.8mm larger than the entrance, the whole straightening is carried out, to ensure the whole steel plate is flat and straight.

[0026] In the optional embodiment, for the steel plate with thickness 35 2 , the water amount is 70-120m 3 / h, the water ratio of the upper and lower surfaces of the steel plate is 1.5-2.0 and the water amount of the lower surface is 105-240m 3 / h, open high-density header 5 and 8 two groups, wherein 5 opens up and closes down, the out of fast cooling red temperature is 800℃±50℃, while ensuring the upper and lower surface target temperature difference in the range of 10-20℃; after the steel plate out of ultra-fast cooling, control open straightening temperature is 850-925℃, straightening roll outer cooling water is always open, the reduction is 0.5mm, the straightening force is 2000-3000KN, according to the exit roll gap is 0.5mm larger than the entrance, the whole straightening is carried out, to ensure the whole steel plate is flat and straight.

[0027] The features and performances of the present application are further described in detail in the following combined with embodiments.

[0028] The schematic diagram of different density grids from the edge to the center of the steel plate in the following embodiments is shown in Figure 1The cooling water cross-sectional area of ​​the grating from the outermost edge to the center of the steel plate is 0.5m². 2 / m 2 0.65m 2 / m 2 and 0.8m 2 / m 2 Each grille is 100mm wide.

[0029] In actual production, the temperature of the steel plate exiting the rolling mill varies, so it is necessary to fine-tune the production operation parameters to keep them within a suitable range.

[0030] Example 1

[0031] For steel plates with a thickness h ≤ 20mm, the initial cooling temperature is controlled at 900℃-1000℃, the roller conveyor speed is 2.3-2.5m / s, and the roller conveyor acceleration is 0.015±0.001m / s². 2 The water volume is 70m 3 / h, the water ratio between the upper and lower surfaces of the steel plate is 0.4 and the water volume on the lower surface is 28m³. 3 / h, only open the two sets of high-density manifolds 7 and 8, with 7 open at the top and closed at the bottom, and the rapid cooling and reddening temperature is 800℃±50℃, while ensuring that the target temperature difference between the upper and lower surfaces is within the range of 30-40℃; after the steel plate is subjected to ultra-rapid cooling, control the straightening temperature to 850-925℃, keep the external cooling water of the straightening rollers constantly open, the reduction is 1.8mm, and the straightening force is 1500-2500KN. According to the principle that the exit roller gap is 1.4mm larger than the inlet, perform partial straightening on the head, and then perform full straightening again to ensure that the entire steel plate is straight and without bending.

[0032] Example 2

[0033] For steel plates with a thickness of 20 < h ≤ 25 mm, the initial cooling temperature is controlled at 950℃-1000℃, the roller conveyor speed is 2.3-2.5 m / s, and the roller conveyor acceleration is 0.015 ± 0.001 m / s². 2 The water volume is 70m 3 / h, the water content on the upper and lower surfaces of the steel plate is 0.6-1.0, and the water content on the lower surface is 42-70m. 3 / h, only 8 sets of high-density manifolds are turned on, the rapid cooling and reddening temperature is 800℃±50℃, and the target temperature difference between the upper and lower surfaces is kept within the range of 20-30℃; after the steel plate is subjected to ultra-rapid cooling, the straightening temperature is controlled at 850-925℃, the external cooling water of the straightening rollers is always on, the reduction is 1.6mm, the straightening force is 2000-3000KN, and the exit roller gap is 1.2mm larger than the inlet. After local straightening of the head, a full straightening is performed to ensure that the entire steel plate is straight and without bending.

[0034] Example 3

[0035] For the steel plate with thickness 25 < h≤ 30mm, the open cooling temperature is controlled to be 950-1000℃, the roller speed is 2.0-2.3m / s, and the roller acceleration is 0.012±0.001m / s 2 , the water amount is 70-80m 3 / h, the water ratio of the upper and lower surfaces of the steel plate is 0.6-1.0, and the water amount of the lower surface is 42-80m 3 / h, only the high-density header 8 groups are opened, the exit fast cooling red temperature is 800℃±50℃, and the target temperature difference between the upper and lower surfaces is ensured to be within the range of 20-30℃; after the steel plate exits the ultra-fast cooling, the open straightening temperature is controlled to be 850-925℃, the straightening roller outer cooling water is always opened, the reduction is 1.2mm, the straightening force is 2000-3000KN, the exit roller gap is 1.0mm larger than the entrance, the head is locally straightened, and then the whole straightening is performed again, so as to ensure that the whole steel plate is flat and straight without bending.

[0036] Example 4

[0037] For the steel plate with thickness 30 < h≤ 35mm, the open cooling temperature is controlled to be 950-1000℃, the roller speed is 2.0-2.3m / s, and the roller acceleration is 0.010±0.001m / s 2 , the water amount is 70-120m 3 / h, the water ratio of the upper and lower surfaces of the steel plate is 1.5-2.0, and the water amount of the lower surface is 105-240m 3 / h, the high-density headers 5 and 8 are opened, and the upper of 5 is opened and the lower is closed, the exit fast cooling red temperature is 800℃±50℃, and the target temperature difference between the upper and lower surfaces is ensured to be within the range of 10-20℃; after the steel plate exits the ultra-fast cooling, the open straightening temperature is controlled to be 850-925℃, the straightening roller outer cooling water is always opened, the reduction is 0.8mm, the straightening force is 2000-3000KN, the exit roller gap is 0.8mm larger than the entrance, and the whole straightening is performed once, so as to ensure that the whole steel plate is flat and straight without bending (when the thickness is more than 30mm, the whole straightening can straighten the plate).

[0038] Example 5

[0039] For the steel plate with thickness 35 < h≤ 40mm, the open cooling temperature is controlled to be 950-1000℃, the roller speed is 1.8-2.0m / s, and the roller acceleration is 0.010±0.001m / s 2 , the water amount is 70-120m 3 / h, the water ratio of the upper and lower surfaces of the steel plate is 1.5-2.0, and the water amount of the lower surface is 105-240m 3 / h, open two groups of high-density header 5 and 8, wherein 5 is opened on the upper switch and the lower switch, the fast cooling red temperature is 800℃±50℃, and the target temperature difference between the upper surface and the lower surface is ensured to be in the range of 10-20℃; after the steel plate is out of the ultra-fast cooling, the straightening temperature is controlled to be 850-925℃, the outer cooling water of the straightening roller is always opened, the pressure reduction is 0.5mm, the straightening force is 2000-3000KN, and the outlet roller gap is 0.5mm larger than the inlet roller gap, so that the whole straightening is carried out once, and the whole steel plate is ensured to be flat and straight without bending.

[0040] Comparative Example 1

[0041] For the steel plate with a thickness h≤40mm, the cooling temperature is controlled to be 900℃-1000℃, the roller speed is 2.3-2.5m / s, and the roller acceleration is 0.015±0.001m / s 2 , the water amount on the roller is 100-110m 3 , the water amount on the roller is 180-220m 3 , the water ratio between the upper surface and the lower surface of the steel plate is 1.8-2.0, only two groups of high-density header 7 and 8 are opened, the fast cooling red temperature is 800℃±50℃, and the target temperature difference between the upper surface and the lower surface is ensured to be in the range of 40-50℃; after the steel plate is out of the ultra-fast cooling, the straightening temperature is controlled to be 850-925℃, the outer cooling water of the straightening roller is always opened, the pressure reduction is 0.8mm, the straightening force is 1000-3000KN, and the outlet roller gap is 1.0mm larger than the inlet roller gap, so that the whole straightening is carried out once, and the whole steel plate is ensured to be flat and straight without bending.

[0042] Experimental results

[0043] Table 1 is the statistical results of the bending of the steel plate with a thickness ≤40mm in Comparative Example 1 (the transverse bending refers to the bending deformation of the steel plate in the width direction, and the tortoise-back bending refers to the bending deformation of the steel plate in the width direction).

[0044] Table 1

[0045] Serial number Bending type Frequency Percentage Cumulative percentage 1 Transverse bending 2337 72.20％ 72.20％ 2 Longitudinal bending 387 11.96％ 84.15％ 3 Camptocormia 319 9.85％ 94.01％ 4 Edge wave bending 59 1.82％ 95.83％ 5 Other bending 135 4.17％ 100％ Total 3237 100％

[0046] As shown in Table 1, in Comparative Example 1, the steel plate with a thickness ≤40mm is subjected to ultra-fast cooling and hot straightening by using a unified method to prevent the steel plate from bending, and the frequency of the transverse bending and the tortoise-back bending is very high.

[0047] Table 2 is the statistical results of the transverse bending ratio, the tortoise-back bending ratio and the bending rate in the examples and the comparative examples.

[0048] Table 2

[0049] Transverse bending percentage Camptocormia percentage Bending rate Example 1 45.37％ 7.21％ 8.34％ Example 2 45.22％ 6.14％ 9.61％ Example 3 47.31％ 7.86％ 8.69％ Example 4 43.57％ 6.97％ 9.41％ Example 5 41.67％ 6.34％ 9.37％ Comparative Example 1 72.53％ 11％ 26％

[0050] As can be seen from the above Table 2, in the embodiment of the present application, the steel plate with a thickness of ≤40 mm is subdivided into steel plates with different thicknesses, different ultrafast cooling and hot straightening processes are adopted for the steel plates with different thicknesses to control the bending rate of the steel plates, and after the different process controls for the steel plates with different thicknesses, the transverse warping ratio, tortoise-back warping ratio and bending rate are obviously reduced.

[0051] The following Table 3 is the bending condition statistical result of the steel plates produced in January to May 2023 in our factory by adopting the scheme provided in the embodiment of the present application.

[0052] Table 3

[0053]

[0054] In the above Table 3, the bending conditions of the steel plates with different thicknesses produced in different months are counted by adopting the method provided in the embodiment of the present application, it can be seen that the transverse warping ratio, tortoise-back warping ratio and bending rate of the steel plates produced in different months are maintained at a relatively constant level, and compared with the method in Comparative Example 1, the transverse warping ratio, tortoise-back warping ratio and bending rate of the steel plates produced by adopting the scheme provided in the embodiment of the present application are lower, and the quality of the steel plates is obviously improved.

[0055] As can be seen above, the embodiment of the present application provides a control method for preventing bending of high-quality carbon steel. Mainly includes: adopting an ultrafast cooling process such as controlling the cooling temperature, roller speed, total cooling water flow and the ratio of water spraying amount on the upper and lower surfaces to regulate and control the cooling rate of the edge of the steel plate, and combining a hot straightening process such as controlling the hot straightening machine pressure, straightening times and tilting adjustment process to straighten the cooled steel plate. The above-mentioned combined control method of ultrafast cooling + hot straightening can effectively reduce the bending rate of carbon steel plate, especially reduce the frequency of occurrence of transverse bending and tortoise-back bending, and improve the quality and economic value of the steel plate.

[0056] The above is only a preferred embodiment of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A control method for preventing bending of high-quality carbon steel, characterized by, The application relates to a high-flatness high-quality carbon steel plate and a preparation method thereof. The superfast cooling system comprises 24 groups of headers, wherein groups 1-4 are gap headers, and groups 5-24 are high-density headers. The superfast cooling process for regulating the cooling rate of the plate edge comprises: shielding the cooling water of the plate edge by using different-density grids to ensure that the cooling speed of the plate edge is the same as the cooling speed of the plate center, and for different-thickness plates, different open cooling temperatures, roller speeds, roller accelerations, water outlet group numbers, water outlet amounts and water outlet ratios are adopted to effectively control the temperature difference between the upper and lower surfaces of the plate after the plate is taken out of the superfast cooling device; The hot straightening process for straightening the cooled plate comprises: for different-thickness plates, different open straightening temperatures, reductions, straightening forces, straightening roller outer cooling water, tilting values and straightening times are adopted to ensure the flatness of the straightened plate. The steel plate edge cooling water is shielded by using different density grids, and the grid cooling water area from the edge of the steel plate to the center is 0.5m 2 / m 2 , 0.65m 2 / m 2 , and 0.8m 2 / m 2 , and the width of each group of grids is 100mm; ​ For the steel plate with thickness h≤20 mm, the open cooling temperature is controlled to be 900-1000℃, the roller speed is 2.3-2.5 m / s, the roller acceleration is 0.015±0.001 m / s 2 , the water amount is 70 m 3 / h, the water ratio of the upper and lower surfaces of the steel plate is 0.4, and the water amount of the lower surface is 28 m 3 / / h, only the two groups of high-density headers 7 and 8 are turned on, the upper 7 is turned on and the lower 7 is turned off, the fast cooling and red temperature is 800℃±50℃, and the target temperature difference between the upper and lower surfaces is ensured to be in the range of 30-40℃; after the steel plate is discharged from the ultra-fast cooling, the open straightening temperature is controlled to be 850-925℃, the outer cooling water of the straightening roller is always turned on, the pressure reduction amount is 1.8 mm, the straightening force is 1500-2500 KN, the exit roller gap is 1.4 mm larger than the entrance, the head is locally straightened, and then the whole straightening is performed again, so that the whole steel plate is flat and straight without bending.

2. The control method according to claim 1, characterized by, For the steel plate with thickness 20 < h ≤ 25 mm, the open cooling temperature is controlled to be 950-1000℃, the roller speed is 2.3-2.5 m / s, the roller acceleration is 0.015±0.001 m / s 2 , the water amount is 70 m 3 / h, the water amount on the upper and lower surfaces of the steel plate is 0.6-1.0 and the water amount on the lower surface is 42-70 m 3 / h, only the high-density header 8 groups are opened, the exit fast cooling red temperature is 800℃±50℃, and meanwhile the target temperature difference between the upper and lower surfaces is ensured to be within the range of 20-30℃; after the steel plate exits the ultra-fast cooling, the open straightening temperature is controlled to be 850-925℃, the outer cooling water of the straightening roller is always opened, the reduction is 1.6 mm, the straightening force is 2000-3000 KN, the exit roller gap is 1.2 mm larger than the entrance, the head is locally straightened, and then the whole straightening is performed again, so as to ensure that the whole steel plate is flat and straight without bending.

3. The control method according to claim 1, characterized by, For the steel plate with thickness 25 < h ≤ 30 mm, the open cooling temperature is controlled to be 950-1000℃, the roller speed is 2.0-2.3 m / s, and the roller acceleration is 0.012±0.001 m / s 2 , the water amount is 70-80 m 3 / h, the water ratio of the upper and lower surfaces of the steel plate is 0.6-1.0, and the water amount of the lower surface is 42-80 m 3 / h, only the high-density header of 8 groups is opened, the exit temperature of the red temperature after the quick cooling is 800℃±50℃, and meanwhile, the target temperature difference of the upper and lower surfaces is ensured to be within the range of 20-30℃; after the steel plate exits the ultra-fast cooling, the open straightening temperature is controlled to be 850-925℃, the outer cooling water of the straightening roller is always opened, the reduction is 1.2 mm, the straightening force is 2000-3000 KN, the exit roller gap is larger than the entrance roller gap by 1.0 mm, the head is locally straightened, and then the whole straightening is performed again, so that the whole steel plate is ensured to be flat and straight without bending.

4. The control method according to claim 1, characterized by, For the steel plate with thickness 30 < h ≤ 35 mm, the open cooling temperature is controlled to be 950-1000℃, the roller speed is 2.0-2.3 m / s, and the roller acceleration is 0.010±0.001 m / s 2 , the water amount is 70-120 m 3 / h, the water ratio of the upper and lower surfaces of the steel plate is 1.5-2.0, and the water amount of the lower surface is 105-240 m 3 / h, two groups of high-density headers 5 and 8 are opened, wherein 5 is opened on the upper surface and closed on the lower surface, the fast cooling and re-red temperature is 800℃±50℃, and the target temperature difference between the upper and lower surfaces is ensured to be within the range of 10-20℃; after the steel plate is discharged from the ultra-fast cooling, the open straightening temperature is controlled to be 850-925℃, the outer cooling water of the straightening roller is always opened, the reduction is 0.8 mm, the straightening force is 2000-3000 KN, and the outlet roller gap is made to be 0.8 mm larger than the inlet according to the outlet roller gap ratio, so that the whole straightening is performed once, and the whole steel plate is ensured to be flat and straight without bending.

5. The control method according to claim 1, characterized by, For the steel plate with thickness 35 < h ≤ 40 mm, the open cooling temperature is controlled to be 950-1000℃, the roller speed is 1.8-2.0 m / s, and the roller acceleration is 0.010±0.001 m / s 2 , the water amount is 70-120 m 3 / h, the water ratio of the upper and lower surfaces of the steel plate is 1.5-2.0, and the water amount of the lower surface is 105-240 m 3 / h, two groups of high-density header pipes 5 and 8 are opened, wherein the upper pipe 5 is opened and the lower pipe 5 is closed, the fast cooling and re-red temperature is 800℃±50℃, and the target temperature difference between the upper and lower surfaces is ensured to be within the range of 10-20℃; after the steel plate is discharged from the ultra-fast cooling, the open straightening temperature is controlled to be 850-925℃, the outer cooling water of the straightening roller is always opened, the reduction is 0.5 mm, the straightening force is 2000-3000 KN, and the outlet roller gap is larger than the inlet roller gap by 0.5 mm, so that the whole straightening is performed once, and the whole steel plate is ensured to be flat and straight without bending.

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