Experimental determination method for optimal water ratio of thickness-direction uniform cooling after hot plate rolling

Abstract

An experimental determination method for the optimal water ratio of thickness-direction uniform cooling of a rolled hot plate adopts a mode of combining an annular track with a trolley, the trolley bears a sample through a sample bearing table to do annular motion, the annular track is an elliptical track comprising two parallel linear sections and two semicircular sections, at least one cooling spray box is arranged along the track of the linear section, and the cooling spray box is arranged on the track of the semicircular section. The cooling area can be infinitely lengthened at any workpiece speed; a cooling area is designed according to the layout of a production line after-rolling cooling area, for a sample of a certain steel type and thickness specification, according to the cooling starting temperature, the cooling stopping temperature and the flow value corresponding to the optimal cooling rate determined by a cooling experiment, the flow of upper and lower spray boxes is adjusted within a certain range of the flow value for a cooling experiment, and the cooling curve of the upper and lower surfaces of the sample is measured. And according to the fitting degree of the cooling curves of the upper and lower surfaces, determining the optimal water-supply and water-discharge ratio meeting the thickness-direction uniform cooling of the steel plate, thereby achieving the purpose of simultaneously meeting the plate shape and performance requirements after cooling.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to an experimental determination method for an optimal water ratio for uniform cooling in the thickness direction of a hot plate after rolling. Background Art

[0002] The technology for uniform cooling of hot plate through the thickness after rolling is to achieve uniform cooling through the thickness by controlling the water volume ratio (hereinafter referred to as the water ratio) between the upper and lower cooling spray boxes, thereby optimizing the hot plate shape after cooling. Currently, there is no corresponding experimental measurement method, and on-site production tests are often required. However, there are many factors that affect the plate shape on site, and temperature measurement during the cooling process is basically impossible, making it difficult to evaluate the uniformity of cooling through the thickness.

[0003] In summary, there is no experimental method for determining the optimal water ratio for uniform cooling of hot plate through the thickness after rolling based on a method and device for achieving an infinitely long cooling zone at an arbitrary workpiece speed at home and abroad. Summary of the Invention

[0004] The purpose of the present invention is to provide an experimental determination method for the optimal water ratio for uniform cooling of the thickness of a hot plate after rolling. By adopting a circular track combined with a trolley, an infinitely long cooling zone is realized at any workpiece speed, and the cooling zone is designed according to the layout of the cooling zone after rolling of the production line. For a sample of a certain steel grade and thickness specification, the flow rates of the upper and lower spray boxes are adjusted within a certain range of the flow rates according to the flow rate values ​​corresponding to the start cooling temperature, stop cooling temperature and optimal cooling rate determined by the cooling experiment. The cooling experiment is carried out, and the optimal upper and lower water ratio that meets the uniform cooling of the steel plate in the thickness is determined based on a fitting degree of more than 80% of the upper and lower surface cooling curves, so as to achieve the purpose of simultaneously meeting the requirements of plate shape and performance after cooling. In addition, since the determination method of the present invention is implemented under conditions basically consistent with the actual working conditions of the production line, the product design output and production line process control are more accurate and efficient, which can effectively accelerate the product research and development speed, improve the process control accuracy and stability, and reduce the production line trial production cost.

[0005] To achieve the above object, the technical solution of the present invention is:

[0006] An experimental method for determining the optimal water ratio for uniform cooling of hot plate through thickness after rolling, comprising the following steps:

[0007] 1) A circular track combined with a trolley is used, wherein the trolley carries the sample through the sample carrying platform and performs circular motion. The circular track is an elliptical track comprising two parallel straight segments and two semicircular segments. At least one cooling spray box is provided along the straight segment track to cool the upper and / or lower surface of the sample. Each cooling spray box includes an upper and a lower cooling spray box. Preferably, the trolley is driven by a motor or a traction drive.

[0008] 2) The sample is heated offline or online, and the temperature of the sample is measured by a temperature measuring device installed on the trolley; when the sample is heated to the temperature required by the process, the trolley is driven to move along the track, driving the sample to pass through the cooling spray box in sequence; the trolley carries the heated sample in a circular motion at a constant speed specified by the process speed or at a certain acceleration; the middle of the sample carrier is hollowed out, and after the sample is fixed to the carrier, the upper and lower surfaces of the sample are unobstructed. The sample passes through the cooling spray box, and the jet ejected by the cooling spray box is directly sprayed onto the sample, cooling the upper and lower surfaces of the sample at the same time; during this period, the sample is driven to pass through a theoretically infinite cooling zone at a set speed to ensure that the sample is cooled from the cooling start temperature to the set target temperature under conditions consistent with the production line working conditions, and the sample temperature and cooling rate are monitored and obtained in real time; wherein,

[0009] Sample running speed: 0~25m / s, acceleration: 0~0.5m / s 2 ;

[0010] The flow rate adjustment range of each cooling spray box is 0~300m 3 / h, preferably, 10 to 50 m 3 / h and other flow rate intervals are set to increase or decrease to conduct cooling experiments;

[0011] The cooling temperature is 700-1000°C. Preferably, the cooling experiment is performed by increasing or decreasing the temperature at intervals of 40-60°C.

[0012] The cooling stop temperature is from room temperature to 800°C. Preferably, the experiment is conducted by increasing or decreasing the temperature by 30-50°C.

[0013] If more than two cooling spray boxes are set, the spacing between the cooling spray boxes should be consistent with the production line design;

[0014] 3) Test the performance and microstructure of the samples;

[0015] 4) Repeat steps 3) and 4) to select cooling control parameters that meet the performance and structure requirements based on the measured data, including determining the flow rate value, cooling start temperature, and cooling end temperature corresponding to the optimal cooling rate;

[0016] 5) Adjusting the flow rates of the upper and lower spray boxes within a certain range of the flow rate value corresponding to the optimal cooling rate, the flow rate adjustment range of the upper and lower spray boxes is 50% to 150% of the measured flow rate value; preferably, the flow rate adjustment range of the upper spray box is 50% to 100% of the measured flow rate value, and the flow rate adjustment range of the lower spray box is 100% to 150% of the measured flow rate value;

[0017] According to the production line process speed and the determined start cooling temperature and final cooling temperature, cooling experiments are carried out under different upper and lower water ratios, and the temperature curves of the upper and lower surfaces of the sample are measured. The optimal upper and lower water ratio that meets the uniform cooling of the steel plate thickness is determined based on the fitting degree of the cooling curves of the upper and lower surfaces of the sample being more than 80%. The upper and lower water ratio is designed to be: 3:1~1:3; preferably, the upper and lower water ratio is 1:1~1:2.

[0018] Preferably, in step 2), based on the start cooling temperature T1, stop cooling temperature T2 and cumulative cooling time t recorded during the experimental process, the cooling rate CR of the steel plate is calculated as follows: (start cooling temperature T1 - stop cooling temperature T2) / cumulative cooling time t, where the cumulative cooling time t is in seconds; the cooling rate range is 0 to 1000°C / s.

[0019] Preferably, in step 3), the performance Xact of the steel plate is measured by a detection device. Xact is considered qualified if it is within the positive and negative tolerance range allowed by the target performance Xtar, that is, ΔX1≤(Xact-Xtar)≤ΔX2, wherein ΔX1: negative tolerance, ΔX2: positive tolerance, and the target performance and positive and negative tolerance range of the steel plate are determined by user needs.

[0020] Preferably, in step 4), the experimental results under different combinations of cooling rate, start cooling temperature and stop cooling temperature are counted, and the combination that meets the product performance is selected for comprehensive comparison. The optimal cooling rate, start cooling temperature and stop cooling temperature that meet the maximum process window of product production are determined according to the production line layout and process system; the preferred start cooling temperature is 800-950°C, and the preferred stop cooling temperature is 550°C-750°C.

[0021] Preferably, the distance between the cooling spray box and the sample surface and the nozzle diameter are arbitrarily adjustable. The nozzle diameter of the cooling spray box is 3 to 30 mm, and the distance between the cooling spray box and the sample surface is 50 to 2200 mm.

[0022] Preferably, the spacing between cooling spray boxes is 0-1.5m, and the flow rate of cooling spray boxes is 0-300m 3 / h, the number of nozzles in the cooling spray box is 1 to 200; the length of the cooling spray box is 100 to 6000 mm.

[0023] Preferably, the circular motion speed of the sample, ie, the linear speed or angular speed, is monitored in real time, and the speed of the sample can be changed online according to the measured temperature data according to the predetermined cooling process, ie, the speed can be increased or decreased or kept constant.

[0024] Preferably, the sample is heated by an offline heating method or an online heating method; preferably, the offline heating method is: after the sample is heated to the temperature required by the process, it is fixedly mounted on the sample carrier, and when it is close to the predetermined cooling temperature, the trolley is driven to move along the circular track, driving the sample to pass through the cooling spray box in sequence, that is, through the theoretically infinitely long cooling zone, to complete the cooling or heat treatment process; the online heating method is: the sample is first fixedly mounted on the sample carrier, and then heated. When the temperature required by the process is reached, the heating device is separated from the circular track area, and then the trolley is driven to move along the circular track to complete the cooling or heat treatment process.

[0025] Preferably, the heating is performed by resistance heating, that is, electrodes are used to clamp both sides of the sample, and the sample is directly heated online as a resistor through a large current; or, induction heating is used.

[0026] Preferably, the sample is cooled by water cooling or air cooling.

[0027] In the experimental determination method of the optimal water ratio for uniform cooling of hot plate through thickness after rolling according to the present invention:

[0028] The experimental device uses a circular runway composed of two parallel straight segments and two semicircular arc segments. A trolley carrying the sample is arranged on the track, and the trolley drives the sample to move along the circular runway.

[0029] The trolley drives the specimen to reach the specified process speed, which can be maintained at a constant speed or accelerated at a certain acceleration.

[0030] Cooling spray boxes are arranged in an array on two straight sections to form two straight cooling zones, which can perform double-sided cooling of the upper and lower surfaces at the same time.

[0031] The hot sample can be driven to any specified speed (slow, medium or high) and pass through a theoretically infinite cooling zone while in motion to ensure that the sample is cooled from the start-of-cooling temperature to the target temperature under conditions that are basically consistent with the on-site working conditions of the production line.

[0032] 1) The water cooling process is completed in the straight line section, which improves the consistency between the experimental and production line conditions;

[0033] 2) The sample speed is adjustable and controllable in a wide range, the sample speed range is: 0 ~ 25m / s, the acceleration range is 0 ~ 0.5m / s 2 ;

[0034] 3) Infinite cooling can meet the cooling needs of any temperature range, sample temperature range: room temperature ~ 1000℃;

[0035] 4) Real-time temperature detection during cooling process, precise control of cooling start and stop temperatures, sample temperature range: room temperature ~ 1000℃;

[0036] 5) The cooling process time is accumulated in real time, and the cooling stop time is precisely controlled to meet the control needs of the phase change time. The cooling time and cooling stop time range: 0 to infinite.

[0037] The distance between the cooling spray box and the sample surface and the nozzle diameter can be adjusted arbitrarily. The basic principle is that the flow rate of cooling water to the sample surface should be as consistent as possible with the production line design.

[0038] The spacing, flow rate and number of nozzles of the cooling spray boxes can be adjusted arbitrarily. The basic principle is that the flow density of cooling water to the sample surface should be kept as consistent as possible with the production line design.

[0039] The distance between the cooling box and the specimen surface, as well as the nozzle diameter, are adjustable. The fundamental principle is to keep the cooling water flow rate to the specimen surface consistent with the production line design. This is because the water-cooling heat exchange capacity is closely related to the water flow rate on the specimen surface. This ensures that the experimental cooling rate is consistent with the field, while maintaining consistency with the production line. The nozzle diameter of the cooling box ranges from 3 to 30 mm, and the distance between the cooling box and the specimen surface ranges from 50 to 2200 mm.

[0040] The spacing, flow rate and number of nozzles of the cooling spray box can be adjusted arbitrarily. The basic principle is that the flow density of cooling water to the sample surface should be as consistent as possible with the production line design. This is an important technical core point for fitting the on-site working conditions of the production line, because the water cooling heat exchange capacity is closely related to the flow density of water on the sample surface. This can ensure to the greatest extent that the experimental cooling rate is consistent with the on-site cooling process under the premise of being consistent with the production line. The spacing range of the cooling spray box is 0 to 1.5m. The flow range of the cooling spray box is 0 to 300m 3 / h, the number of cooling spray box nozzles ranges from 0 to 200.

[0041] If the height and spacing of the cooling boxes are the same as the production line, the calculation can be simply based on the ratio of the cooling box length. If the maximum flow rates of the cooling boxes in different cooling zones of the production line vary, the flow rate of the experimental device box should be calculated based on the flow rate of the cooling box with the highest flow rate. The cooling box length ranges from 100 to 6000 mm.

[0042] Experimental determination of the optimal water ratio for uniform cooling in the thickness direction:

[0043] According to the flow rate value corresponding to the determined optimal cooling rate, the flow rates of the upper and lower spray boxes are adjusted within a certain range of the flow rate value. Cooling experiments are carried out under different water ratios according to the production line process speed and the determined starting cooling temperature and final cooling temperature. The temperature curves of the upper and lower surfaces of the sample are measured. The optimal upper and lower water ratio that meets the requirement of uniform cooling of the steel plate through the thickness is determined based on a fitting degree of more than 80% for the upper and lower surface cooling curves.

[0044] The present invention selects the water ratio as the process parameter for uniform cooling of the product, mainly so as to be applicable to production lines with different post-rolling cooling configurations.

[0045] Beneficial effects of the present invention:

[0046] The present invention realizes an infinitely long cooling zone at any workpiece speed by adopting a circular track combined with a trolley, and designs the cooling zone according to the layout of the post-rolling cooling zone of the production line. For samples of a certain steel grade and thickness specification, the flow rates of the upper and lower spray boxes are adjusted within a certain range of the flow rates according to the start-cooling temperature, stop-cooling temperature and flow rate corresponding to the optimal cooling rate determined by the cooling experiment to conduct a cooling experiment. By measuring the cooling curves of the upper and lower surfaces of the sample, the optimal upper and lower water ratio that satisfies uniform cooling of the steel plate in the thickness direction is determined based on a fitting degree of more than 80% of the upper and lower surface cooling curves, thereby achieving the purpose of simultaneously meeting the requirements of plate shape and performance after cooling.

[0047] In addition, since the experimental measurement method described in the present invention is implemented under conditions that are basically consistent with the actual working conditions of the production line, the product design output and production line process control are more accurate and efficient, which can effectively accelerate the speed of product development, improve process control accuracy and stability, and reduce the production line trial production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 Schematic diagram of the cooling experimental device of the present invention. DETAILED DESCRIPTION

[0049] See also Figure 1 The experimental method for determining the optimal water ratio for uniform cooling of hot plate through thickness after rolling according to the present invention comprises the following steps:

[0050] 1) A circular track 1 is combined with a trolley 2. The trolley 2 carries a sample 100 for circular motion via a sample carrier 3. The circular track 1 is an elliptical track comprising two parallel straight segments and two semicircular segments. At least one cooling spray box 4 is provided along the straight segment track to cool the upper and / or lower surfaces of the sample. Each cooling spray box 4 includes an upper and a lower cooling spray box. The sample 100 is heated to a set temperature by a heating device 5 arranged across the circular track 1 or on the trolley 2. During this time, the temperature of the sample 100 is measured by a temperature measuring device 61 provided on the trolley 2. The temperature measuring device 61 transmits data to a temperature measuring host 62 via wireless or wired means. The temperature measuring host 62 is connected to a controller PLC.

[0051] 2) The sample is heated offline or online, and the temperature of the sample is measured by a temperature measuring device installed on the trolley; when the sample is heated to the temperature required by the process, the trolley is driven to move along the track, driving the sample to pass through the cooling spray box in sequence; the trolley carries the heated sample in a circular motion at a constant speed specified by the process speed or at a certain acceleration; the middle of the sample carrier is hollowed out, and after the sample is fixed to the carrier, the upper and lower surfaces of the sample are unobstructed. The sample passes through the cooling spray box, and the jet ejected by the cooling spray box is directly sprayed onto the sample, cooling the upper and lower surfaces of the sample at the same time; during this period, the sample is driven to pass through a theoretically infinite cooling zone at a set speed to ensure that the sample is cooled from the cooling start temperature to the set target temperature under conditions consistent with the production line working conditions, and the sample temperature and cooling rate are monitored and obtained in real time; wherein,

[0052] Sample running speed: 0~25m / s, acceleration: 0~0.5m / s 2 ;

[0053] The flow rate adjustment range of each cooling spray box is 0~300m 3 / h, preferably, 10 to 50 m 3 / h and other flow rate intervals are set to increase or decrease to conduct cooling experiments;

[0054] The cooling temperature is 700-1000°C. Preferably, the cooling experiment is performed by increasing or decreasing the temperature at intervals of 40-60°C.

[0055] The cooling stop temperature is from room temperature to 800°C. Preferably, the experiment is conducted by increasing or decreasing the temperature by 30-50°C.

[0056] If more than two cooling spray boxes are set, the spacing between the cooling spray boxes should be consistent with the production line design;

[0057] 3) Test the performance and microstructure of the samples;

[0058] 4) Repeat steps 3) and 4) to select cooling control parameters that meet the performance and structure requirements based on the measured data, including determining the flow rate value, cooling start temperature, and cooling end temperature corresponding to the optimal cooling rate;

[0059] 5) Adjusting the flow rates of the upper and lower spray boxes within a certain range of the flow rate value corresponding to the optimal cooling rate, the flow rate adjustment range of the upper and lower spray boxes is 50% to 150% of the measured flow rate value; preferably, the flow rate adjustment range of the upper spray box is 50% to 100% of the measured flow rate value, and the flow rate adjustment range of the lower spray box is 100% to 150% of the measured flow rate value;

[0060] Cooling experiments were carried out under different upper and lower water ratios according to the process speed of the production line and the determined start cooling temperature and final cooling temperature, and the temperature curves of the upper and lower surfaces of the sample were measured. The optimal upper and lower water ratio that satisfied uniform cooling of the steel plate thickness was determined based on a fitting degree of more than 80% of the cooling curves of the upper and lower surfaces of the sample. The designed upper and lower water ratio was 3:1 to 1:3; preferably, the upper and lower water ratio was 1:1 to 1:2.

[0061] Preferably, in step 2), based on the start cooling temperature T1, stop cooling temperature T2 and cumulative cooling time t recorded during the experimental process, the cooling rate CR of the steel plate is calculated as follows: (start cooling temperature T1 - stop cooling temperature T2) / cumulative cooling time t, where the cumulative cooling time t is in seconds; the cooling rate range is 0 to 1000°C / s.

[0062] Preferably, in step 3), the performance Xact of the steel plate is measured by a detection device. Xact is considered qualified if it is within the positive and negative tolerance range allowed by the target performance Xtar, that is, ΔX1≤(Xact-Xtar)≤ΔX2, wherein ΔX1: negative tolerance, ΔX2: positive tolerance, and the target performance and positive and negative tolerance range of the steel plate are determined by user needs.

[0063] Preferably, in step 4), the experimental results under different combinations of cooling rate, start cooling temperature and stop cooling temperature are counted, and the combination that meets the product performance is selected for comprehensive comparison. The optimal cooling rate, start cooling temperature and stop cooling temperature that meet the maximum process window of product production are determined according to the production line layout and process system; the preferred start cooling temperature is 800-950°C, and the preferred stop cooling temperature is 550°C-750°C.

[0064] Preferably, the distance between the cooling spray box and the sample surface and the nozzle diameter are arbitrarily adjustable. The nozzle diameter of the cooling spray box is 3 to 30 mm, and the distance between the cooling spray box and the sample surface is 50 to 2200 mm.

[0065] Preferably, the spacing between cooling spray boxes is 0-1.5m, and the flow rate of cooling spray boxes is 0-300m 3 / h, the number of nozzles in the cooling spray box is 1 to 200; the length of the cooling spray box is 100 to 6000 mm.

[0066] Preferably, the trolley is driven by a motor or a traction drive.

[0067] Preferably, the circular motion speed of the sample, ie, the linear speed or angular speed, is monitored in real time, and the speed of the sample can be changed online according to the measured temperature data according to the predetermined cooling process, ie, the speed can be increased or decreased or kept constant.

[0068] Preferably, the sample is heated by an offline heating method or an online heating method; preferably, the offline heating method is: after the sample is heated to the temperature required by the process, it is fixedly mounted on the sample carrier, and when it is close to the predetermined cooling temperature, the trolley is driven to move along the circular track, driving the sample to pass through the cooling spray box in sequence, that is, through the theoretically infinitely long cooling zone, to complete the cooling or heat treatment process; the online heating method is: the sample is first fixedly mounted on the sample carrier, and then heated. When the temperature required by the process is reached, the heating device is separated from the circular track area, and then the trolley is driven to move along the circular track to complete the cooling or heat treatment process.

[0069] Preferably, the heating is performed by resistance heating, that is, electrodes are used to clamp both sides of the sample, and the sample is directly heated online as a resistor through a large current; or, induction heating is used.

[0070] Preferably, the sample is cooled by water cooling or air cooling.

[0071] Example

[0072] Cooling test of a certain steel grade with a thickness of 3mm, including:

[0073] 1) Cooling spray box layout

[0074] The distance between the cooling spray box and the sample surface and the nozzle diameter are the same as those of a post-rolling cooling spray box flow non-adjustable production line. The distance from the upper surface of the sample is 1.8 meters, the distance from the lower surface of the sample is 0.15 meters, and the nozzle diameter is 22 mm.

[0075] The spacing between the cooling spray boxes in the experimental device is the same as that of a post-rolling cooling spray box flow rate non-adjustable production line, which is 0.36m. Six groups of spray boxes are arranged on one side, the cooling zone length is 2.16m, and there are 12 groups of spray boxes on both sides.

[0076] The cooling spray box length of the production line is 2m, and the flow rate of a single upper spray box is 108m 3 / h, the flow rate of a single lower spray box is 108m 3 / h;

[0077] The cooling spray box of the experimental device is 0.5m long;

[0078] The maximum flow rate of a single upper spray box in the experimental device = 108m 3 / h*0.5 / 2=27m 3 / h;

[0079] The maximum flow rate of a single spray box in the experimental device = 17m 3 / h*0.5 / 2=27m 3 / h.

[0080] 2) Experimental determination of process parameters for uniform cooling in thickness direction after hot plate rolling

[0081] The best cooling rate determined by the cooling experiment of a certain steel grade with a thickness of 3mm is 32℃ / s, and the corresponding cooling spray box flow rate is 18m 3 / h.

[0082] The experimental scheme was designed according to different combinations of upper and lower spray boxes with different flow rates and water ratios, as shown in Table 1. The starting cooling temperature was 850°C and the final cooling temperature was 600°C. The steel plate buried cooling experiment was carried out. The steel plate running speed was set to 12m / s according to the actual production line. The fitting degree of the cooling curve of the steel plate after cooling under different flow rates and water ratios of the upper and lower spray boxes was measured, and the experimental results were obtained, as shown in Table 1.

[0083] The fitting degree of cooling curve of steel plate after cooling under different combinations of flow rate and water ratio of upper and lower spray boxes was analyzed. Taking into account the process conditions before and after the production line and the cooling control window, the sequence number 4 was finally selected as the production line process parameter, that is, the upper spray flow rate of 13.5m 3 / h, downward spray flow rate 18m 3 / h and water ratio is 1:1.333.

[0084] Table 1 Fitting degree of cooling curve of steel plate after cooling at different flow rates of upper and lower spray boxes

[0085]

Claims

1. An experimental method for determining the optimal water ratio for uniform cooling of hot plate through thickness after rolling, characterized in that: The steps include: 1) A circular track combined with a trolley is used, wherein the trolley carries the sample through the sample carrying platform and performs circular motion. The circular track is an elliptical track comprising two parallel straight segments and two semicircular segments. At least one cooling spray box is provided along the straight segment track to cool the upper and / or lower surface of the sample. Each cooling spray box includes an upper and a lower cooling spray box. Preferably, the trolley is driven by a motor or a traction drive. 2) The sample is heated offline or online, and the temperature of the sample is measured by a temperature measuring device installed on the trolley; when the sample is heated to the temperature required by the process, the trolley is driven to move along the track, driving the sample to pass through the cooling spray box in sequence; the trolley carries the heated sample in a circular motion at a constant speed specified by the process speed or at a certain acceleration; the middle of the sample carrier is hollowed out, and after the sample is fixed to the carrier, the upper and lower surfaces of the sample are unobstructed. The sample passes through the cooling spray box, and the jet ejected by the cooling spray box is directly sprayed onto the sample, cooling the upper and lower surfaces of the sample at the same time; during this period, the sample is driven to pass through a theoretically infinite cooling zone at a set speed to ensure that the sample is cooled from the cooling start temperature to the set target temperature under conditions consistent with the production line working conditions, and the sample temperature and cooling rate are monitored and obtained in real time; wherein, Sample running speed: 0~25m / s, acceleration: 0~0.5m / s 2 ; The flow rate adjustment range of each cooling spray box is 0~300m 3 / h, preferably, 10 to 50 m 3 / h and other flow rate intervals are set to increase or decrease to conduct cooling experiments; The cooling temperature is 700-1000°C. Preferably, the cooling experiment is performed by increasing or decreasing the temperature at intervals of 40-60°C. The cooling stop temperature is from room temperature to 800°C. Preferably, the experiment is conducted by increasing or decreasing the temperature by 30-50°C. If more than two cooling spray boxes are set, the spacing between the cooling spray boxes should be consistent with the production line design; 3) Conduct performance and microstructure tests on the samples; 4) Repeat steps 3) and 4) to select cooling control parameters that meet the performance and structure requirements based on the measured data, including determining the flow rate value, cooling start temperature, and cooling end temperature corresponding to the optimal cooling rate; 5) Adjusting the flow rates of the upper and lower spray boxes within a certain range of flow rates corresponding to the optimal cooling rate, wherein the flow rate adjustment range of the upper and lower spray boxes is 50% to 150% of the measured flow rate value; preferably, the flow rate adjustment range of the upper spray box is 50% to 100% of the measured flow rate value, and the flow rate adjustment range of the lower spray box is 100% to 150% of the measured flow rate value; Cooling experiments were carried out under different upper and lower water ratios according to the process speed of the production line and the determined start cooling temperature and final cooling temperature, and the temperature curves of the upper and lower surfaces of the sample were measured. The optimal upper and lower water ratio that satisfied uniform cooling of the steel plate thickness was determined based on a fitting degree of more than 80% for the cooling curves of the upper and lower surfaces of the sample. The upper and lower water ratio was designed to be: 3:1 to 1:3; preferably, the upper and lower water ratio was 1:1 to 1:

2.

2. The method for experimentally determining the optimal water ratio for uniform cooling of hot plate through thickness after rolling according to claim 1, characterized in that: Step 2) Based on the cooling start temperature T1, cooling stop temperature T2, and cumulative cooling time t recorded during the experiment, calculate the cooling rate CR of the steel plate = (cooling start temperature T1 - cooling stop temperature T2) / cumulative cooling time t, where the cumulative cooling time t is in seconds; the cooling rate range is 0 to 1000°C / s.

3. The method for experimentally determining the optimal water ratio for uniform cooling of hot plate through thickness after rolling according to claim 1, characterized in that: Step 3) The performance Xact of the steel plate is measured by a detection device. Xact is considered qualified if it is within the positive and negative tolerance range allowed by the target performance Xtar, that is, ΔX1≤(Xact-Xtar)≤ΔX2, where ΔX1: negative tolerance, ΔX2: positive tolerance, and the target performance and positive and negative tolerance range of the steel plate are determined by user needs.

4. The method for experimentally determining the optimal water ratio for uniform cooling of hot plate through thickness after rolling according to claim 1, characterized in that: In step 4), the experimental results under different combinations of cooling rate, start cooling temperature and stop cooling temperature are counted, and the combination that meets the product performance is selected for comprehensive comparison. The optimal cooling rate, start cooling temperature and stop cooling temperature that meet the maximum process window of product production are determined according to the production line layout and process system; the preferred start cooling temperature is 800-950°C, and the preferred stop cooling temperature is 550°C-750°C.

5. The method for experimentally determining the optimal water ratio for uniform cooling of hot plate through thickness after rolling according to claim 1, characterized in that: The distance between the cooling spray box and the sample surface and the nozzle diameter can be adjusted arbitrarily. The nozzle diameter of the cooling spray box is 3 to 30 mm, and the distance between the cooling spray box and the sample surface is 50 to 2200 mm.

6. The method for experimentally determining the optimal water ratio for uniform cooling of hot plate through thickness after rolling according to claim 1 or 5, characterized in that: The spacing between cooling spray boxes is 0 to 1.5m, and the flow rate of cooling spray boxes is 0 to 300m 3 / h, the number of nozzles in the cooling spray box is 1 to 200; the length of the cooling spray box is 100 to 6000 mm.

7. The method for experimentally determining the optimal water ratio for uniform cooling of hot plate through thickness after rolling according to claim 1, characterized in that: The circular motion speed of the sample, i.e. the linear speed or angular speed, is monitored in real time, and the speed of the sample can be changed online according to the measured temperature data according to the predetermined cooling process, i.e. the speed can be increased or decreased or kept constant.

8. The method for experimentally determining the optimal water ratio for uniform cooling of hot plate through thickness after rolling according to claim 1, characterized in that: The sample is heated by an offline heating method or an online heating method; preferably, the offline heating method is: after the sample is heated to the temperature required by the process, it is fixedly mounted on the sample carrier, and when it is close to the predetermined cooling temperature, the trolley is driven to move along the circular track, driving the sample to pass through the cooling spray box in sequence, that is, through a theoretically infinitely long cooling zone, to complete the cooling or heat treatment process; the online heating method is: the sample is first fixedly mounted on the sample carrier, and then heated. When the temperature required by the process is reached, the heating device is separated from the circular track area, and the trolley is driven to move along the circular track to complete the cooling or heat treatment process.

9. The method for experimentally determining the optimal water ratio for uniform cooling of hot plate through thickness after rolling according to claim 1 or 8, characterized in that: Heating adopts resistance heating method, that is, electrodes are clamped on both sides of the sample, and the sample is directly heated online as a resistor through a large current; or, induction heating method is adopted.

10. The method for experimentally determining the optimal water ratio for uniform cooling of hot plate through thickness after rolling according to claim 1 or 8, characterized in that: The sample is cooled by water or air.

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