Method for quickly determining differences in cooling speed of steel plates

Abstract

The application discloses a method for quickly determining the difference of cooling speed of a steel plate, comprising the following steps: S1. hot-rolling a steel plate blank, wherein the thickness of the steel plate blank is greater than or equal to 12 mm, preferably greater than or equal to 15 mm; S2. cooling the hot-rolled steel plate blank, wherein the cooling comprises laminar flow cooling; S3. performing real-time flatness detection on the cooled steel plate blank to obtain a flatness detection result of the cooled steel plate blank, wherein the flatness detection result comprises the plate shape of the cooled steel plate blank; and S4. determining the difference of cooling speed of the upper surface and the lower surface of the steel plate blank according to the flatness detection result after cooling. The method of the application solves the problem that the prior art can only be judged after sampling and performing organization performance analysis, has real-time performance, can quickly determine the difference of cooling speed of the steel plate, and can be adjusted in time in the production process; a large number of steel plate blanks can be found and saved in time, the efficiency is improved, and waste is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steel cooling, and particularly relates to a method for quickly determining the cooling speed difference of a steel plate. BACKGROUND

[0002] In the hot rolling production process of a steel plate, cooling is a conventional process after the steel plate leaves the F7 rolling mill stand. For a steel plate with a thickness of 12 mm or more, the performance is not uniform in the thickness direction and the shape is poor, which is a major difficulty currently faced. In order to ensure that the performance of the steel plate is the same in the thickness direction and the shape is good, it is required that the cooling speeds of the upper surface and the lower surface of the steel plate are the same. When the steel plate is cooled through the upper and lower cooling headers, if only the same water flow, the proportion and the pressure of the upper cooling header and the lower cooling header are set, the cooling speeds of the upper surface and the lower surface of the steel plate cannot be the same. For different steel grades, the speeds of the upper cooling header and the lower cooling header can only be set according to experience, so that the cooling speeds of the upper surface and the lower surface of the steel plate are as same as possible.

[0003] The prior art takes a sample of a thick-gauge plate blank after cooling, analyzes the organization and performance thereof, adjusts the process parameters of cooling according to the performance difference, and the sampling and adjustment cycle is as long as 4-7 days, during which, numerous steel plates are cooled by using the same cooling process parameters. The method of sampling and analyzing the steel plate blank has serious hysteresis, which affects the performance of the steel plate in batches, and the steel plate cannot be discovered and rescued in time. SUMMARY

[0004] In view of this, the application provides a method for quickly determining the cooling speed difference of a steel plate, which solves the problem that the cooling speed of the steel plate cannot be judged in time in the prior art.

[0005] In a first aspect, an embodiment of the application provides a method for quickly determining the cooling speed difference of a steel plate, including the following steps:

[0006] S1. Hot rolling a steel plate blank, wherein the thickness of the steel plate blank is 12 mm or more, and is preferably 15 mm or more;

[0007] S2. Cooling the hot-rolled steel plate blank, wherein the cooling includes laminar cooling;

[0008] S3. Real-time flatness detection of the cooled steel plate blank to obtain a cooling flatness detection result of the steel plate blank, wherein the cooling flatness detection result includes the shape of the cooled steel plate blank;

[0009] S4. Determining the cooling speed difference between the upper surface and the lower surface of the steel plate blank according to the cooling flatness detection result.

[0010] According to an embodiment of one aspect of the present application, the cooling further comprises ultrafast cooling, which is performed before the laminar cooling.

[0011] According to an embodiment of one aspect of the present application, the S1 step further comprises: performing flatness detection on the hot-rolled steel plate slab to obtain an initial flatness detection result, wherein the initial flatness detection result comprises a shape of the hot-rolled steel plate slab.

[0012] According to an embodiment of one aspect of the present application, the S4 step specifically comprises: correcting the post-cooling flatness detection result by using the initial flatness detection result to obtain a shape of the steel plate slab due to thermal expansion, and determining a difference in cooling speed between the upper surface and the lower surface of the steel plate slab according to the corrected post-cooling flatness detection result.

[0013] According to an embodiment of one aspect of the present application, the S2 step specifically comprises: cooling the hot-rolled steel plate slab to cool the steel plate slab to 560-600°C, wherein the cooling comprises laminar cooling.

[0014] According to an embodiment of one aspect of the present application, the method further comprises:

[0015] S5. Adjusting the cooling parameters according to the difference in cooling speed between the upper surface and the lower surface of the steel plate slab to reduce the difference in cooling speed between the upper surface and the lower surface, wherein the cooling parameters comprise at least one of a pressure, a water flow speed, a water flow volume of each of the upper cooling header and the lower cooling header, and a water flow volume ratio of the upper cooling header and the lower cooling header.

[0016] According to an embodiment of one aspect of the present application, the cooling parameters are the water flow volume ratio of the upper cooling header and the lower cooling header.

[0017] In a second aspect, embodiments of the present application provide a system for quickly determining a cooling speed of a steel plate, the system comprising:

[0018] A hot rolling unit configured to hot roll a steel plate slab;

[0019] A cooling device configured to cool the hot-rolled steel plate slab, wherein the cooling device comprises a laminar cooling device;

[0020] A flatness detection device configured to perform real-time flatness detection on the cooled steel plate slab to obtain a post-cooling flatness detection result of the steel plate slab, wherein the post-cooling flatness detection result comprises a shape of the cooled steel plate slab;

[0021] The cooling speed determining device is configured to determine the difference between the cooling speeds of the upper surface and the lower surface of the steel slab in the cooling device according to the flatness detection result.

[0022] According to an embodiment of the aspect of the present application, the system further comprises:

[0023] The cooling parameter adjusting device is configured to adjust the cooling parameter of the cooling device according to the difference between the cooling speeds of the upper surface and the lower surface of the steel slab, so as to reduce the difference between the cooling speeds of the upper surface and the lower surface of the steel slab.

[0024] According to an embodiment of the aspect of the present application, the flatness detection device further comprises a flatness detector arranged at the end of the hot rolling unit, and configured to detect the flatness of the hot-rolled steel slab to obtain an initial flatness detection result.

[0025] The cooling speed determining device is configured to correct the post-cooling flatness detection result by using the initial flatness detection result to obtain the shape of the steel slab caused by thermal expansion, and determine the difference between the cooling speeds of the upper surface and the lower surface of the steel slab according to the corrected post-cooling flatness detection result.

[0026] Compared with the prior art, the present application has at least the following beneficial effects:

[0027] The method provided by the present application can obtain the shape of the steel slab by detecting the flatness of the post-cooling steel slab with a thickness of 12 mm or more in real time after hot rolling. Based on the influence of thermal expansion on the shape of the steel slab during cooling, the difference between the cooling speeds of the upper surface and the lower surface of the steel slab can be determined according to the shape of the steel slab. The method is timely and accurate, and solves the long process analysis method of the prior art, which uses sampling of thick gauge hot-rolled plates, organization performance analysis, evaluation of the difference in organization performance of the steel slab in the thickness direction, and judgment of whether the cooling speeds of the upper surface and the lower surface of the steel slab are consistent. The method of the present application can quickly determine the cooling speed difference of the steel slab, and timely adjust in the production process, thereby avoiding the performance unevenness in the thickness direction of the thick gauge steel plate. The method of the present application can timely find and save a large amount of steel slab, improve the efficiency, and reduce the waste. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments of the present application will be briefly introduced. For those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0029] Figure 1is a flowchart of a method for quickly determining the difference in cooling speed of a steel plate provided by an embodiment of the present application;

[0030] Figure 2 is a schematic diagram of the metallographic structure of a steel material provided by an embodiment of the present application;

[0031] Figure 3 is a relationship diagram of the corresponding cooling speed of a steel plate and the shape of the steel plate in the upper cooling header and the lower cooling header in a cooling process provided by an embodiment of the present application;

[0032] Figure 4 is a schematic diagram of a system for quickly determining the cooling speed of a steel plate provided by an embodiment of the present application;

[0033] Figure 5 is a shape diagram of a cooled steel plate provided by an embodiment 1 of the present application;

[0034] Figure 6 is a shape diagram of a cooled steel plate provided by an embodiment 2 of the present application;

[0035] Figure 7 is a metallographic structure diagram of a steel plate provided by an embodiment 1 of the present application;

[0036] Figure 8 is a metallographic structure diagram of a steel plate provided by an embodiment 2 of the present application;

[0037] Figure 9 is a shape diagram of a steel plate after adjusting the cooling parameters provided by an embodiment of the present application;

[0038] Figure 10 is a metallographic structure diagram of a steel plate after adjusting the cooling parameters provided by an embodiment of the present application.

[0039] Wherein, 100, hot rolling unit, 200, cooling equipment, 210, ultra-fast cooling equipment, 211, upper cooling header, 212, lower cooling header, 220, layer cooling equipment, 300, flatness detection device, 400, cooling speed determination device, 500, conveying roller, 600, coiling equipment. DETAILED DESCRIPTION

[0040] In order to make the application purposes, technical solutions and beneficial technical effects of the present application clearer, the present application will be further described in detail below in combination with embodiments. It should be understood that the embodiments described in the present specification are only for the purpose of explaining the present application, and are not intended to limit the present application.

[0041] For simplicity, only some numerical ranges are explicitly recited herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with any other lower limit to form a range not explicitly recited, and likewise any upper limit can be combined with any other upper limit to form a range not explicitly recited. Furthermore, although a range is recited, it is to be understood that every point or individual number within the range is also specifically disclosed. Thus, for example, every point or individual number within the range is to be considered as a separate embodiment.

[0042] In the description of the present application, it is to be understood that, unless otherwise specified, "above" and "below" are inclusive of the number itself, and "a plurality of" means two or more.

[0043] The foregoing summary of the present application is not intended to describe every disclosed embodiment or implementation of the present application. The following description more specifically illustrates example embodiments. Throughout this application, guidance is provided by a series of examples, which can be used in various combinations. In each instance, the recitation is merely representative of a group, and should not be construed as exhaustive.

[0044] In the hot rolling production process, the steel plate is usually cooled after the F7 rack for the purpose of performance control. The difference in cold hardenability between thick gauge steel plate (12 mm and above) and thin gauge (4 mm and below) is obvious: thin gauge steel plate is not sensitive to the difference in cooling speed of the upper and lower headers of ultra-fast cooling / zone cooling, and it is easy to harden, and the cooling structure in the thickness direction is uniform; while thick gauge steel plate is sensitive to the difference in cooling speed of the upper and lower headers of ultra-fast cooling / zone cooling, and it is not easy to harden, and it is easy to have non-uniform structure in the thickness direction.

[0045] The current production process for thick gauge steel plate mainly includes rolling-cooling-coiling-cooling. The sampling of the steel plate for structure and performance testing is generally after the cooling process. One of the existing methods to judge the difference in cooling speed of the upper and lower surfaces of the steel plate in cooling is to take samples of thick gauge hot-rolled plates for structure and performance analysis, then evaluate the difference in structure and performance in the thickness direction, and thus make the judgment. If abnormal structure and performance is found, the cooling parameters in cooling are adjusted, including adjusting the cooling water flow or the number of header switches of the upper and lower headers of ultra-fast cooling / zone cooling.

[0046] The above method has a large lag, and the cycle is long and the efficiency is low, which cannot timely respond to the cooling parameters of the steel plate in rolling, resulting in batch reduction or rejection of the same batch of steel plate due to non-uniform performance in the thickness direction, causing great economic loss to the enterprise. At present, there is no method and basis for real-time determination of the difference in cooling speed of the upper and lower cooling headers during the rolling process of thick gauge steel plate.

[0047] The inventors discovered that the effect of cooling on sheet shape includes two aspects: thermal expansion and phase transformation expansion. Thermal expansion is essentially the thermal expansion and contraction of the steel slab; phase transformation expansion is essentially the dissolution of the original austenite structure in the steel slab as the cooling rate changes, while other structures, such as pearlite and bainite, precipitate. Due to the different densities of these structures, phase transformation expansion causes a change in the volume of the steel slab. Further research revealed that the phase transformation pathways in steel materials during cooling are quite complex due to factors such as differences in carbon content and alloying element content, cooling rate, and the cooling initiation point. Figure 2 Taking typical microstructures of several steel materials as examples, the trend of phase transformation expansion with changes in microstructure is illustrated.

[0048] Depend on Figure 2 It is known that the volume of the microstructure continuously increases during the transformation of austenite to martensite. This is essentially related to the transformation from a face-centered cubic (FCC) crystal structure to a body-centered cubic (BCC) crystal structure and the solid solution of carbon atoms in the matrix. The volume expansion during the transformation of austenite to ferrite / pearlite is not significant, but the volume expansion is more pronounced when a large amount of austenite transforms into martensite.

[0049] Furthermore, the inventors discovered that the aforementioned thermal expansion and phase transformation expansion have opposite effects on the shape of the steel slab. Considering only the effect of thermal expansion, in the cooling equipment, when the cooling rate of the upper manifold is less than that of the lower manifold, the steel slab exhibits a turtle-back shape; when the cooling rate of the upper manifold is greater than that of the lower manifold, the steel slab exhibits a U-shape, such as... Figure 3 As shown.

[0050] Based on this, the inventors conducted extensive research and provided a method for quickly determining the difference in cooling rate of steel plates. This method uses plate shape changes to achieve online determination of the difference in cooling rate between the upper and lower surfaces of the steel plate during cooling, avoiding the need for offline microstructure analysis and performance testing.

[0051] The first aspect of this application provides a method for rapidly determining differences in the cooling rates of steel plates, such as... Figure 1 As shown, it includes the following steps:

[0052] S1. Hot-rolling the steel slab, wherein the thickness of the steel slab is 12mm or more, preferably 15mm or more;

[0053] S2. Cooling the hot-rolled steel slab, wherein the cooling includes laminar flow cooling;

[0054] S3. Perform real-time flatness detection on the cooled steel slab blank to obtain the flatness detection result of the cooled steel slab blank, wherein the flatness detection result after cooling includes the shape of the cooled steel slab blank;

[0055] S4. Determine the difference of cooling speed of the upper surface and the lower surface of the steel slab according to the flatness detection result after the cooling.

[0056] According to the embodiments of the present application, the real-time flatness detection of the steel slab can be used to determine the difference of cooling speed of the steel slab or to adjust the parameters in the cooling process in real time. The method of the present application can determine the difference of cooling speed of the steel slab, which is real-time, simple and fast, and does not increase the cost.

[0057] According to the embodiments of the present application, the influence of the rolling on the deformation of the steel slab of the same thickness specification of the same batch or different batches can be ignored to a certain extent through the theoretical research and analysis of the inventor. The main reason for the deformation of the slab is the setting of the cooling parameters in the cooling process. In the cooling process, the influence of thermal expansion and phase change expansion on the shape of the steel slab is opposite. In the case of only considering the influence of thermal expansion, the difference of cooling speed of the upper surface and the lower surface of the steel slab can be determined by the shape of the steel slab, so that the cooling parameters in the cooling process can be adjusted on this basis. According to the embodiments of the present application, the thicker the steel plate, the more difficult it is to cool through, and the above specification is beneficial to magnify the influence of the difference of cooling speed in the cooling process on the shape of the steel plate. Therefore, the steel plate with a thickness of 12 mm or more can be selected, and the thickness of 15 mm or more is preferred.

[0058] According to the embodiments of the present application, the flatness detection in the S4 step is set after the cooling process in the S3 step. After the flatness detection in the S4 step, the steel plate can be subjected to the coiling process to make the steel plate into a steel coil.

[0059] In some embodiments, when the shape of the cooled steel slab is tortoise-back shape, the cooling speed of the upper header on the steel slab is less than that of the lower header in the cooling process. The cooling speed of the upper header on the steel slab can be increased, or the cooling speed of the lower header on the steel slab can be reduced to reduce the difference of cooling speed of the upper surface and the lower surface of the steel slab, so as to control the shape of the steel plate.

[0060] In some embodiments, when the shape of the cooled steel slab is U-shaped, the cooling speed of the upper header on the steel slab is greater than that of the lower header in the cooling process. The cooling speed of the upper header on the steel slab can be reduced, or the cooling speed of the lower header on the steel slab can be increased to reduce the difference of cooling speed of the upper surface and the lower surface of the steel slab, so as to control the shape of the steel plate. In some embodiments, after the real-time flatness detection of the cooled steel slab, the coiling is carried out. The real-time flatness detection is arranged between the cooling and the coiling, which can determine the shape of the steel slab affected by the cooling more timely and accurately.

[0061] In some embodiments, the cooling further comprises ultra-fast cooling, which is performed before the laminar cooling.

[0062] According to the embodiments of the present application, in the production process of the steel plate slab, the commonly used cooling process includes ultra-fast cooling and laminar cooling, and both of the two cooling processes can have certain deformation effects on the steel plate.

[0063] In some embodiments, the same steel grade is selected, and the laminar cooling or the ultra-fast cooling and the laminar cooling in sequence are independently performed, so that the effects of the ultra-fast cooling and the laminar cooling on the plate shape can be distinguished.

[0064] In some embodiments, at least two steel grades are selected, and the laminar cooling or the ultra-fast cooling and the laminar cooling in sequence are independently performed, so that the effects of the upper header and the lower header in the ultra-fast cooling and the laminar cooling on the cooling speed of the steel plate can be determined respectively.

[0065] In some embodiments, the S1 step further comprises: performing flatness detection on the hot-rolled steel plate slab to obtain an initial flatness detection result, wherein the initial flatness detection result includes the plate shape of the hot-rolled steel plate slab.

[0066] In some embodiments, the S4 step specifically comprises: correcting the flatness detection result after cooling by using the initial flatness detection result to obtain the plate shape of the steel plate slab caused by thermal expansion, and determining the difference in cooling speed between the upper surface and the lower surface of the steel plate slab according to the corrected flatness detection result after cooling. In order to more accurately obtain the effect of cooling on the plate shape of the steel plate, so that the flatness detection result can more accurately reflect the effect of cooling on the plate shape of the steel plate slab, the flatness detection is performed on the hot-rolled steel plate slab, and the initial flatness detection result and the flatness detection result are used to understand and exclude the effect of hot rolling on the plate shape of the steel plate.

[0067] In some embodiments, the S2 step specifically comprises: cooling the hot-rolled steel plate slab to 560-600 DEG C, wherein the cooling includes laminar cooling.

[0068] According to the embodiments of the present application, by selecting a suitable steel grade, the characteristics of the steel grade are that the target cooling is 560-600 DEG C when cooling; when the above-mentioned steel plate slab is cooled to 560-600 DEG C, the temperature range in which a large amount of bainite is formed and the temperature range in which martensite is formed can be avoided, so that the effect of phase change expansion on the plate shape is greatly weakened, and only the effect of thermal expansion on the plate shape is determined, so that the effect of phase change expansion on the plate shape in cooling can be eliminated.

[0069] In some embodiments, the method further comprises:

[0070] S5. Adjusting the cooling parameters according to the difference between the cooling speeds of the upper surface and the lower surface of the steel slab, so as to reduce the difference between the cooling speeds of the upper surface and the lower surface, the cooling parameters including at least one of the pressure, the water flow speed, the water flow volume of each of the upper cooling header and the lower cooling header, and the ratio of the water flow volumes of the upper cooling header and the lower cooling header.

[0071] According to the embodiments of the present application, after the difference between the cooling speeds of the upper surface and the lower surface of the steel slab is determined, the cooling parameters can be adjusted so that the difference between the cooling speeds of the upper surface and the lower surface is reduced, and the shape of the steel slab is close to a straight line, thus achieving a good shape effect.

[0072] In some embodiments, the cooling parameters are the ratio of the water flow volumes of the upper cooling header and the lower cooling header.

[0073] According to the embodiments of the present application, the pressure, the water flow speed, the water flow volume of each of the upper cooling header and the lower cooling header, and the ratio of the water flow volumes of the upper cooling header and the lower cooling header can all affect the cooling speeds of the upper surface and the lower surface of the steel slab, and the cooling parameter that plays a major role, i.e., the ratio of the water flow volumes of the upper cooling header and the lower cooling header, has the greatest impact on the cooling speeds of the upper surface and the lower surface of the steel slab.

[0074] In a second aspect, the embodiments of the present application provide a system for quickly determining the cooling speed of a steel plate, as shown in Figure 4 The system comprises:

[0075] A hot rolling unit 100 for hot rolling a steel slab;

[0076] A cooling device 200 for cooling the hot-rolled steel slab, wherein the cooling device comprises a laminar cooling device;

[0077] A flatness detection device 300 for real-time flatness detection of the cooled steel slab to obtain a cooled flatness detection result of the steel slab, wherein the cooled flatness detection result includes the shape of the cooled steel slab;

[0078] A cooling speed determination device 400 for determining the difference between the cooling speeds of the upper surface and the lower surface of the steel slab in the cooling device according to the flatness detection result.

[0079] According to the embodiments of the present application, in the system, the steel plate can be rolled and cooled, and the existing flatness detection device is arranged after the cooling equipment, and the flatness of the steel plate can be detected. In the present application, the flatness detection device detects the flatness detection result, which is used to determine the difference between the cooling speeds of the upper surface and the lower surface of the steel plate slab in the cooling equipment. In addition, the operator can use the flatness detection result to determine the difference between the cooling speeds of the upper surface and the lower surface of the steel plate slab in the cooling equipment, and the flatness detection result can also be used to determine the difference between the cooling speeds of the upper surface and the lower surface of the steel plate slab in the cooling equipment through related software, virtual devices, etc.

[0080] According to the embodiments of the present application, the cooling equipment 200 can be a laminar cooling equipment 220, and can also be a super-fast cooling equipment 210 and a laminar cooling equipment 220. The super-fast cooling equipment 210 is provided with an upper cooling header 211 and a lower cooling header 212. The laminar cooling equipment 220 can be provided with an upper cooling header and a lower cooling header. The steel plate slab is conveyed through the conveying roller 500. Between the cooling equipment 200 and the coiling equipment 600, the flatness detection device 300 is arranged, and the cooling speed determination device 400 can also be arranged.

[0081] In some embodiments, the system further comprises:

[0082] The cooling parameter adjustment device is used to adjust the cooling parameters of the cooling equipment according to the difference between the cooling speeds of the upper surface and the lower surface of the steel plate slab, so as to reduce the difference between the cooling speeds of the upper surface and the lower surface of the steel plate slab.

[0083] According to the embodiments of the present application, after the difference between the cooling speeds of the upper surface and the lower surface of the steel plate slab in the cooling equipment is determined, the parameters in the cooling equipment can be adjusted by a person, and the cooling parameters of the cooling equipment can also be adjusted by using a corresponding device, such as a cooling parameter adjustment device, or in combination with a corresponding algorithm, etc.

[0084] In some embodiments, the flatness detection device further comprises a flatness detector arranged at the end of the hot rolling mill train, which is used to detect the flatness of the hot-rolled steel plate slab to obtain an initial flatness detection result.

[0085] The cooling speed determination device is used to correct the post-cooling flatness detection result by using the initial flatness detection result to obtain the plate shape caused by thermal expansion of the steel plate slab, and determine the difference between the cooling speeds of the upper surface and the lower surface of the steel plate slab according to the corrected post-cooling flatness detection result.

[0086] In order to more accurately obtain the influence of cooling on the shape of the steel plate, and make the flatness detection result more accurately reflect the effect of cooling on the shape of the slab, the flatness detector at the end of the hot rolling mill can correct the shape of the steel plate in the cooling process, so as to determine the shape of the slab caused by thermal expansion in the cooling process, and determine the difference in cooling speed between the upper surface and the lower surface of the slab in the cooling process.

[0087] Example

[0088] The present disclosure is more specifically described by the following examples, which are merely illustrative and not limiting, as various modifications and changes in the procedures and compositions described herein can become apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported herein are on a weight basis, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used without further purification, and the instruments used in the examples are commercially available.

[0089] Example 1

[0090] A method for quickly determining the cooling speed difference of a steel plate is provided, which is used for producing a steel plate with a grade of S460Q-Z, and includes the following steps:

[0091] S1. Hot rolling a slab, wherein the thickness of the slab is 20 mm and the width of the slab is 2040 mm;

[0092] S2. Cooling the hot-rolled slab, wherein the cooling includes laminar cooling and ultra-fast cooling, and the target cooling temperature is 560℃;

[0093] S3. Real-time flatness detection of the cooled slab to obtain a flatness detection result of the cooled slab, wherein the flatness detection result includes the shape of the cooled slab;

[0094] S4. Determining the difference in cooling speed between the upper surface and the lower surface of the slab according to the flatness detection result. The shape of the steel plate before coiling after cooling is shown in FIG. 1. Figure 5

[0095] Example 2

[0096] A method for quickly determining the cooling speed difference of a steel plate is provided, which is used for producing a steel plate with a grade of CCS-B, and includes the following steps:

[0097] S1. Hot rolling a slab, wherein the thickness of the slab is 19.75 mm and the width of the slab is 2000 mm; ​

[0098] S2. cooling the hot-rolled steel slab, wherein the cooling is laminar cooling, and the target cooling temperature is 590°C;

[0099] S3. performing real-time flatness detection on the cooled steel slab to obtain a flatness detection result of the cooled steel slab, wherein the flatness detection result comprises a shape of the cooled steel slab;

[0100] S4. determining a difference in cooling speed between the upper surface and the lower surface of the steel slab according to the flatness detection result. The shape of the steel after cooling and before coiling is shown in Figure 6 .

[0101] Performance detection

[0102] By means of optical microscope, the steel plates prepared in Example 1 and Example 2 are detected respectively after coiling, and the metallographic structures shown in Figure 7 and Figure 8 are obtained respectively, Figure 7 is the metallographic structure of the steel plate of Example 1, the left picture is the metallographic structure of the upper surface of the steel plate, and the right picture is the metallographic structure of the lower surface of the steel plate. By comparing the two pictures, it can be inferred that the metallographic structures of the upper and lower surfaces are different, and it can be inferred that the cooling speeds of the upper and lower surfaces are different. Figure 8 is the metallographic structure of the steel plate of Example 2, the left picture is the metallographic structure of the upper surface of the steel plate, and the right picture is the metallographic structure of the lower surface of the steel plate. By comparing the two pictures, it can be inferred that the metallographic structures of the upper and lower surfaces are different, and it can be inferred that the cooling speeds of the upper and lower surfaces are different.

[0103] The shape of the steel plate in Example 1 is tortoise-back shape. By adjusting the cooling parameters in the cooling process in the production process of the steel production line in Example 1, at least one of the cooling parameters including the pressure, water flow speed, water flow rate of the upper cooling header and the lower cooling header, and the water flow rate ratio of the upper cooling header and the lower cooling header, mainly the water flow rate ratio of the upper cooling header and the lower cooling header. The adjustment method is as follows: the opening degree of the upper header water valve is 100%, and the opening degree of the lower header water valve is 75%, to obtain the shape of the steel plate shown in Figure 9 . After coiling, the steel plate is detected, and the metallographic structure of the steel plate after adjusting the cooling parameters is shown in Figure 10 . As can be seen from the figure, the metallographic structures of the upper surface and the lower surface are approximately the same, and it can be inferred that the cooling speeds of the upper and lower surfaces are the same.

[0104] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present application, and these modifications or replacements shall be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A method for quickly determining a difference in cooling speed of a steel sheet, characterized by, The method comprises the following steps: S1. Hot-rolling a steel plate slab, and detecting flatness of the hot-rolled steel plate slab to obtain an initial flatness detection result, wherein the initial flatness detection result comprises a shape of the hot-rolled steel plate slab; the thickness of the steel plate slab is greater than or equal to 12 mm, and the production grade of the steel plate is S460Q-Z or CCS-B; S2. cooling the hot-rolled steel sheet slab to cool the steel sheet slab to 560 o C-590 o C, wherein the cooling comprises laminar cooling; S3. Real-time flatness detection is performed on the cooled steel plate slab to obtain a post-cooling flatness detection result of the steel plate slab, wherein the post-cooling flatness detection result comprises a shape of the cooled steel plate slab; S4. The post-cooling flatness detection result is corrected by using the initial flatness detection result to obtain a shape of the steel plate slab caused by thermal expansion, and a difference in cooling speed between the upper surface and the lower surface of the steel plate slab is determined according to the corrected post-cooling flatness detection result.

2. The method of claim 1, wherein, The thickness of the steel plate slab is greater than or equal to 15 mm.

3. The method of claim 1, wherein, The cooling further comprises ultrafast cooling, which is performed before the laminar cooling.

4. The method of claim 1, wherein, The method further comprises: S5. Adjusting cooling parameters according to the difference in cooling speed between the upper surface and the lower surface of the steel plate slab to reduce the difference in cooling speed between the upper surface and the lower surface, wherein the cooling parameters comprise at least one of pressure, water flow speed, water flow rate of each of the upper cooling header and the lower cooling header, and a water flow rate ratio of the upper cooling header and the lower cooling header.

5. The method of claim 4, wherein, The cooling parameters are the water flow rate ratio of the upper cooling header and the lower cooling header.

6. A system for rapidly determining the cooling rate of a steel sheet, characterized by The system is used to perform the method according to any one of claims 1-5, and the system comprises: a hot rolling unit configured to hot-roll a steel plate slab; a cooling device configured to cool the hot-rolled steel plate slab, wherein the cooling device comprises a laminar cooling device; a flatness detection device configured to perform real-time flatness detection on the cooled steel plate slab to obtain a post-cooling flatness detection result of the steel plate slab, wherein the post-cooling flatness detection result comprises a shape of the cooled steel plate slab; the flatness detection device further comprises a flatness detector arranged at the end of the hot rolling unit and configured to detect flatness of the hot-rolled steel plate slab to obtain an initial flatness detection result; a cooling speed determination device configured to correct the post-cooling flatness detection result by using the initial flatness detection result to obtain a shape of the steel plate slab caused by thermal expansion, and determine a difference in cooling speed between the upper surface and the lower surface of the steel plate slab according to the corrected post-cooling flatness detection result.

7. The system of claim 6, wherein, The system further comprises: a cooling parameter adjustment device configured to adjust cooling parameters of the cooling device according to the difference in cooling speed between the upper surface and the lower surface of the steel plate slab to reduce the difference in cooling speed between the upper surface and the lower surface of the steel plate slab.

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